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# Line 2  Line 2 
2  This file contains a concatenation of the PCRE man pages, converted to plain  This file contains a concatenation of the PCRE man pages, converted to plain
3  text format for ease of searching with a text editor, or for use on systems  text format for ease of searching with a text editor, or for use on systems
4  that do not have a man page processor. The small individual files that give  that do not have a man page processor. The small individual files that give
5  synopses of each function in the library have not been included. There are  synopses of each function in the library have not been included. Neither has
6  separate text files for the pcregrep and pcretest commands.  the pcredemo program. There are separate text files for the pcregrep and
7    pcretest commands.
8  -----------------------------------------------------------------------------  -----------------------------------------------------------------------------
9    
10    
# Line 18  INTRODUCTION Line 19  INTRODUCTION
19    
20         The  PCRE  library is a set of functions that implement regular expres-         The  PCRE  library is a set of functions that implement regular expres-
21         sion pattern matching using the same syntax and semantics as Perl, with         sion pattern matching using the same syntax and semantics as Perl, with
22         just  a  few  differences. Certain features that appeared in Python and         just  a few differences. Some features that appeared in Python and PCRE
23         PCRE before they appeared in Perl are also available using  the  Python         before they appeared in Perl are also available using the  Python  syn-
24         syntax.  There is also some support for certain .NET and Oniguruma syn-         tax,  there  is  some  support for one or two .NET and Oniguruma syntax
25         tax items, and there is an option for  requesting  some  minor  changes         items, and there is an option for requesting some  minor  changes  that
26         that give better JavaScript compatibility.         give better JavaScript compatibility.
27    
28         The  current  implementation of PCRE (release 7.x) corresponds approxi-         The  current implementation of PCRE corresponds approximately with Perl
29         mately with Perl 5.10, including support for UTF-8 encoded strings  and         5.12, including support for UTF-8 encoded strings and  Unicode  general
30         Unicode general category properties. However, UTF-8 and Unicode support         category  properties.  However,  UTF-8  and  Unicode  support has to be
31         has to be explicitly enabled; it is not the default. The Unicode tables         explicitly enabled; it is not the default. The  Unicode  tables  corre-
32         correspond to Unicode release 5.0.0.         spond to Unicode release 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 54  INTRODUCTION Line 55  INTRODUCTION
55         library is built. The pcre_config() function makes it  possible  for  a         library is built. The pcre_config() function makes it  possible  for  a
56         client  to  discover  which  features are available. The features them-         client  to  discover  which  features are available. The features them-
57         selves are described in the pcrebuild page. Documentation about  build-         selves are described in the pcrebuild page. Documentation about  build-
58         ing  PCRE for various operating systems can be found in the README file         ing  PCRE  for various operating systems can be found in the README and
59         in the source distribution.         NON-UNIX-USE files in the source distribution.
60    
61         The library contains a number of undocumented  internal  functions  and         The library contains a number of undocumented  internal  functions  and
62         data  tables  that  are  used by more than one of the exported external         data  tables  that  are  used by more than one of the exported external
# Line 71  USER DOCUMENTATION Line 72  USER DOCUMENTATION
72         The user documentation for PCRE comprises a number  of  different  sec-         The user documentation for PCRE comprises a number  of  different  sec-
73         tions.  In the "man" format, each of these is a separate "man page". In         tions.  In the "man" format, each of these is a separate "man page". In
74         the HTML format, each is a separate page, linked from the  index  page.         the HTML format, each is a separate page, linked from the  index  page.
75         In  the  plain text format, all the sections are concatenated, for ease         In  the  plain  text format, all the sections, except the pcredemo sec-
76         of searching. The sections are as follows:         tion, are concatenated, for ease of searching. The sections are as fol-
77           lows:
78    
79           pcre              this document           pcre              this document
80           pcre-config       show PCRE installation configuration information           pcre-config       show PCRE installation configuration information
# Line 81  USER DOCUMENTATION Line 83  USER DOCUMENTATION
83           pcrecallout       details of the callout feature           pcrecallout       details of the callout feature
84           pcrecompat        discussion of Perl compatibility           pcrecompat        discussion of Perl compatibility
85           pcrecpp           details of the C++ wrapper           pcrecpp           details of the C++ wrapper
86             pcredemo          a demonstration C program that uses PCRE
87           pcregrep          description of the pcregrep command           pcregrep          description of the pcregrep command
88             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
93                               regular expressions                               regular expressions
          pcresyntax        quick syntax reference  
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.  
   
        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.  
   
    Validity of UTF-8 strings  
   
        When you set the PCRE_UTF8 flag, the strings  passed  as  patterns  and  
        subjects are (by default) checked for validity on entry to the relevant  
        functions. From release 7.3 of PCRE, the check is according  the  rules  
        of  RFC  3629, which are themselves derived from the Unicode specifica-  
        tion. Earlier releases of PCRE followed the rules of  RFC  2279,  which  
        allows  the  full range of 31-bit values (0 to 0x7FFFFFFF). The current  
        check allows only values in the range U+0 to U+10FFFF, excluding U+D800  
        to U+DFFF.  
   
        The  excluded  code  points are the "Low Surrogate Area" of Unicode, of  
        which the Unicode Standard says this: "The Low Surrogate Area does  not  
        contain  any  character  assignments,  consequently  no  character code  
        charts or namelists are provided for this area. Surrogates are reserved  
        for  use  with  UTF-16 and then must be used in pairs." The code points  
        that are encoded by UTF-16 pairs  are  available  as  independent  code  
        points  in  the  UTF-8  encoding.  (In other words, the whole surrogate  
        thing is a fudge for UTF-16 which unfortunately messes up UTF-8.)  
   
        If an  invalid  UTF-8  string  is  passed  to  PCRE,  an  error  return  
        (PCRE_ERROR_BADUTF8) 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  when  PCRE_NO_UTF8_CHECK  is  set,  
        what  happens  depends on why the string is invalid. If the string con-  
        forms to the "old" definition of UTF-8 (RFC 2279), it is processed as a  
        string  of  characters  in  the  range 0 to 0x7FFFFFFF. In other words,  
        apart from the initial validity test, PCRE (when in UTF-8 mode) handles  
        strings  according  to  the more liberal rules of RFC 2279. However, if  
        the string does not even conform to RFC 2279, the result is  undefined.  
        Your program may crash.  
   
        If  you  want  to  process  strings  of  values  in the full range 0 to  
        0x7FFFFFFF, encoded in a UTF-8-like manner as per the old RFC, you  can  
        set PCRE_NO_UTF8_CHECK to bypass the more restrictive test. However, in  
        this situation, you will have to apply your own validity check.  
   
    General comments about UTF-8 mode  
   
        1. An unbraced hexadecimal escape sequence (such  as  \xb3)  matches  a  
        two-byte UTF-8 character if the value is greater than 127.  
   
        2.  Octal  numbers  up to \777 are recognized, and match two-byte UTF-8  
        characters for values greater than \177.  
   
        3. Repeat quantifiers apply to complete UTF-8 characters, not to  indi-  
        vidual bytes, for example: \x{100}{3}.  
   
        4.  The dot metacharacter matches one UTF-8 character instead of a sin-  
        gle byte.  
   
        5. 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().  
   
        6. 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}.  
   
        7.  Similarly,  characters that match the POSIX named character classes  
        are all low-valued characters.  
   
        8. However, the Perl 5.10 horizontal and vertical  whitespace  matching  
        escapes (\h, \H, \v, and \V) do match all the appropriate Unicode char-  
        acters.  
   
        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
110         University Computing Service         University Computing Service
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  two  initials,         so  I've  taken  it away. If you want to email me, use my two initials,
115         followed by the two digits 10, at the domain cam.ac.uk.         followed by the two digits 10, at the domain cam.ac.uk.
116    
117    
118  REVISION  REVISION
119    
120         Last updated: 12 April 2008         Last updated: 24 August 2011
121         Copyright (c) 1997-2008 University of Cambridge.         Copyright (c) 1997-2011 University of Cambridge.
122  ------------------------------------------------------------------------------  ------------------------------------------------------------------------------
123    
124    
# Line 277  PCRE BUILD-TIME OPTIONS Line 136  PCRE BUILD-TIME OPTIONS
136         script,  where the optional features are selected or deselected by pro-         script,  where the optional features are selected or deselected by pro-
137         viding options to configure before running the make  command.  However,         viding options to configure before running the make  command.  However,
138         the  same  options  can be selected in both Unix-like and non-Unix-like         the  same  options  can be selected in both Unix-like and non-Unix-like
139         environments using the GUI facility of  CMakeSetup  if  you  are  using         environments using the GUI facility of cmake-gui if you are using CMake
140         CMake instead of configure to build PCRE.         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         The complete list of options for configure (which includes the standard
148         ones such as the  selection  of  the  installation  directory)  can  be         ones  such  as  the  selection  of  the  installation directory) can be
149         obtained by running         obtained by running
150    
151           ./configure --help           ./configure --help
152    
153         The  following  sections  include  descriptions  of options whose names         The following sections include  descriptions  of  options  whose  names
154         begin with --enable or --disable. These settings specify changes to the         begin with --enable or --disable. These settings specify changes to the
155         defaults  for  the configure command. Because of the way that configure         defaults for the configure command. Because of the way  that  configure
156         works, --enable and --disable always come in pairs, so  the  complemen-         works,  --enable  and --disable always come in pairs, so the complemen-
157         tary  option always exists as well, but as it specifies the default, it         tary option always exists as well, but as it specifies the default,  it
158         is 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
174    
175         By default, the configure script will search for a C++ compiler and C++         By default, the configure script will search for a C++ compiler and C++
# Line 307  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
203    
204         UTF-8  support allows PCRE to process character values greater than 255         UTF-8 support allows PCRE to process character values greater than  255
205         in the strings that it handles. On its own, however, it does  not  pro-         in  the  strings that it handles. On its own, however, it does not pro-
206         vide any facilities for accessing the properties of such characters. If         vide any facilities for accessing the properties of such characters. If
207         you want to be able to use the pattern escapes \P, \p,  and  \X,  which         you  want  to  be able to use the pattern escapes \P, \p, and \X, which
208         refer to Unicode character properties, you must add         refer to Unicode character properties, you must add
209    
210           --enable-unicode-properties           --enable-unicode-properties
211    
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 30K  of  tables  to  the         Including  Unicode  property  support  adds around 30K of tables to the
216         PCRE  library.  Only  the general category properties such as Lu and Nd         PCRE library. Only the general category properties such as  Lu  and  Nd
217         are supported. Details are given in the pcrepattern documentation.         are supported. Details are given in the pcrepattern documentation.
218    
219    
220    JUST-IN-TIME COMPILER SUPPORT
221    
222           Just-in-time compiler support is included in the build by specifying
223    
224             --enable-jit
225    
226           This  support  is available only for certain hardware architectures. If
227           this option is set for an  unsupported  architecture,  a  compile  time
228           error  occurs.   See  the pcrejit documentation for a discussion of JIT
229           usage. When JIT support is enabled, pcregrep automatically makes use of
230           it, unless you add
231    
232             --disable-pcregrep-jit
233    
234           to the "configure" command.
235    
236    
237  CODE VALUE OF NEWLINE  CODE VALUE OF NEWLINE
238    
239         By default, PCRE interprets character 10 (linefeed, LF)  as  indicating         By  default,  PCRE interprets the linefeed (LF) character as indicating
240         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
241         systems. You can compile PCRE to use character 13 (carriage return, CR)         systems.  You  can compile PCRE to use carriage return (CR) instead, by
242         instead, by adding         adding
243    
244           --enable-newline-is-cr           --enable-newline-is-cr
245    
246         to  the  configure  command.  There  is  also  a --enable-newline-is-lf         to the  configure  command.  There  is  also  a  --enable-newline-is-lf
247         option, which explicitly specifies linefeed as the newline character.         option, which explicitly specifies linefeed as the newline character.
248    
249         Alternatively, you can specify that line endings are to be indicated by         Alternatively, you can specify that line endings are to be indicated by
# Line 356  CODE VALUE OF NEWLINE Line 255  CODE VALUE OF NEWLINE
255    
256           --enable-newline-is-anycrlf           --enable-newline-is-anycrlf
257    
258         which  causes  PCRE  to recognize any of the three sequences CR, LF, or         which causes PCRE to recognize any of the three sequences  CR,  LF,  or
259         CRLF as indicating a line ending. Finally, a fifth option, specified by         CRLF as indicating a line ending. Finally, a fifth option, specified by
260    
261           --enable-newline-is-any           --enable-newline-is-any
# Line 381  WHAT \R MATCHES Line 280  WHAT \R MATCHES
280         functions are called.         functions are called.
281    
282    
 BUILDING SHARED AND STATIC LIBRARIES  
   
        The  PCRE building process uses libtool to build both shared and static  
        Unix libraries by default. You can suppress one of these by adding  one  
        of  
   
          --disable-shared  
          --disable-static  
   
        to the configure command, as required.  
   
   
283  POSIX MALLOC USAGE  POSIX MALLOC USAGE
284    
285         When PCRE is called through the POSIX interface (see the pcreposix doc-         When PCRE is called through the POSIX interface (see the pcreposix doc-
# Line 416  HANDLING VERY LARGE PATTERNS Line 303  HANDLING VERY LARGE PATTERNS
303         nation metacharacter). By default, two-byte values are used  for  these         nation metacharacter). By default, two-byte values are used  for  these
304         offsets,  leading  to  a  maximum size for a compiled pattern of around         offsets,  leading  to  a  maximum size for a compiled pattern of around
305         64K. This is sufficient to handle all but the most  gigantic  patterns.         64K. This is sufficient to handle all but the most  gigantic  patterns.
306         Nevertheless,  some  people do want to process enormous patterns, so it         Nevertheless,  some  people do want to process truyl enormous patterns,
307         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-
308         adding a setting such as         sets by adding a setting such as
309    
310           --with-link-size=3           --with-link-size=3
311    
# Line 445  AVOIDING EXCESSIVE STACK USAGE Line 332  AVOIDING EXCESSIVE STACK USAGE
332         to the configure command. With this configuration, PCRE  will  use  the         to the configure command. With this configuration, PCRE  will  use  the
333         pcre_stack_malloc  and pcre_stack_free variables to call memory manage-         pcre_stack_malloc  and pcre_stack_free variables to call memory manage-
334         ment functions. By default these point to malloc() and free(), but  you         ment functions. By default these point to malloc() and free(), but  you
335         can replace the pointers so that your own functions are used.         can replace the pointers so that your own functions are used instead.
336    
337         Separate  functions  are  provided  rather  than  using pcre_malloc and         Separate  functions  are  provided  rather  than  using pcre_malloc and
338         pcre_free because the  usage  is  very  predictable:  the  block  sizes         pcre_free because the  usage  is  very  predictable:  the  block  sizes
# Line 453  AVOIDING EXCESSIVE STACK USAGE Line 340  AVOIDING EXCESSIVE STACK USAGE
340         reverse order. A calling program might be able to  implement  optimized         reverse order. A calling program might be able to  implement  optimized
341         functions  that  perform  better  than  malloc()  and free(). PCRE runs         functions  that  perform  better  than  malloc()  and free(). PCRE runs
342         noticeably more slowly when built in this way. This option affects only         noticeably more slowly when built in this way. This option affects only
343         the   pcre_exec()   function;   it   is   not   relevant  for  the  the         the pcre_exec() function; it is not relevant for pcre_dfa_exec().
        pcre_dfa_exec() function.  
344    
345    
346  LIMITING PCRE RESOURCE USAGE  LIMITING PCRE RESOURCE USAGE
347    
348         Internally, PCRE has a function called match(), which it calls  repeat-         Internally,  PCRE has a function called match(), which it calls repeat-
349         edly   (sometimes   recursively)  when  matching  a  pattern  with  the         edly  (sometimes  recursively)  when  matching  a  pattern   with   the
350         pcre_exec() function. By controlling the maximum number of  times  this         pcre_exec()  function.  By controlling the maximum number of times this
351         function  may be called during a single matching operation, a limit can         function may be called during a single matching operation, a limit  can
352         be placed on the resources used by a single call  to  pcre_exec().  The         be  placed  on  the resources used by a single call to pcre_exec(). The
353         limit  can be changed at run time, as described in the pcreapi documen-         limit can be changed at run time, as described in the pcreapi  documen-
354         tation. The default is 10 million, but this can be changed by adding  a         tation.  The default is 10 million, but this can be changed by adding a
355         setting such as         setting such as
356    
357           --with-match-limit=500000           --with-match-limit=500000
358    
359         to   the   configure  command.  This  setting  has  no  effect  on  the         to  the  configure  command.  This  setting  has  no  effect   on   the
360         pcre_dfa_exec() matching function.         pcre_dfa_exec() matching function.
361    
362         In some environments it is desirable to limit the  depth  of  recursive         In  some  environments  it is desirable to limit the depth of recursive
363         calls of match() more strictly than the total number of calls, in order         calls of match() more strictly than the total number of calls, in order
364         to restrict the maximum amount of stack (or heap,  if  --disable-stack-         to  restrict  the maximum amount of stack (or heap, if --disable-stack-
365         for-recursion is specified) that is used. A second limit controls this;         for-recursion is specified) that is used. A second limit controls this;
366         it defaults to the value that  is  set  for  --with-match-limit,  which         it  defaults  to  the  value  that is set for --with-match-limit, which
367         imposes  no  additional constraints. However, you can set a lower limit         imposes no additional constraints. However, you can set a  lower  limit
368         by adding, for example,         by adding, for example,
369    
370           --with-match-limit-recursion=10000           --with-match-limit-recursion=10000
371    
372         to the configure command. This value can  also  be  overridden  at  run         to  the  configure  command.  This  value can also be overridden at run
373         time.         time.
374    
375    
376  CREATING CHARACTER TABLES AT BUILD TIME  CREATING CHARACTER TABLES AT BUILD TIME
377    
378         PCRE  uses fixed tables for processing characters whose code values are         PCRE uses fixed tables for processing characters whose code values  are
379         less than 256. By default, PCRE is built with a set of tables that  are         less  than 256. By default, PCRE is built with a set of tables that are
380         distributed  in  the  file pcre_chartables.c.dist. These tables are for         distributed in the file pcre_chartables.c.dist. These  tables  are  for
381         ASCII codes only. If you add         ASCII codes only. If you add
382    
383           --enable-rebuild-chartables           --enable-rebuild-chartables
384    
385         to the configure command, the distributed tables are  no  longer  used.         to  the  configure  command, the distributed tables are no longer used.
386         Instead,  a  program  called dftables is compiled and run. This outputs         Instead, a program called dftables is compiled and  run.  This  outputs
387         the source for new set of tables, created in the default locale of your         the source for new set of tables, created in the default locale of your
388         C runtime system. (This method of replacing the tables does not work if         C runtime system. (This method of replacing the tables does not work if
389         you are cross compiling, because dftables is run on the local host.  If         you  are cross compiling, because dftables is run on the local host. If
390         you  need  to  create alternative tables when cross compiling, you will         you need to create alternative tables when cross  compiling,  you  will
391         have to do so "by hand".)         have to do so "by hand".)
392    
393    
394  USING EBCDIC CODE  USING EBCDIC CODE
395    
396         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
397         character  code  is  ASCII  (or Unicode, which is a superset of ASCII).         character code is ASCII (or Unicode, which is  a  superset  of  ASCII).
398         This is the case for most computer operating systems.  PCRE  can,  how-         This  is  the  case for most computer operating systems. PCRE can, how-
399         ever, be compiled to run in an EBCDIC environment by adding         ever, be compiled to run in an EBCDIC environment by adding
400    
401           --enable-ebcdic           --enable-ebcdic
402    
403         to the configure command. This setting implies --enable-rebuild-charta-         to the configure command. This setting implies --enable-rebuild-charta-
404         bles. You should only use it if you know that  you  are  in  an  EBCDIC         bles.  You  should  only  use  it if you know that you are in an EBCDIC
405         environment (for example, an IBM mainframe operating system).         environment (for example,  an  IBM  mainframe  operating  system).  The
406           --enable-ebcdic option is incompatible with --enable-utf8.
407    
408    
409  PCREGREP OPTIONS FOR COMPRESSED FILE SUPPORT  PCREGREP OPTIONS FOR COMPRESSED FILE SUPPORT
# Line 533  PCREGREP OPTIONS FOR COMPRESSED FILE SUP Line 420  PCREGREP OPTIONS FOR COMPRESSED FILE SUP
420         if they are not.         if they are not.
421    
422    
423    PCREGREP BUFFER SIZE
424    
425           pcregrep  uses  an internal buffer to hold a "window" on the file it is
426           scanning, in order to be able to output "before" and "after" lines when
427           it  finds  a match. The size of the buffer is controlled by a parameter
428           whose default value is 20K. The buffer itself is three times this size,
429           but because of the way it is used for holding "before" lines, the long-
430           est line that is guaranteed to be processable is  the  parameter  size.
431           You can change the default parameter value by adding, for example,
432    
433             --with-pcregrep-bufsize=50K
434    
435           to the configure command. The caller of pcregrep can, however, override
436           this value by specifying a run-time option.
437    
438    
439  PCRETEST OPTION FOR LIBREADLINE SUPPORT  PCRETEST OPTION FOR LIBREADLINE SUPPORT
440    
441         If you add         If you add
442    
443           --enable-pcretest-libreadline           --enable-pcretest-libreadline
444    
445         to  the  configure  command,  pcretest  is  linked with the libreadline         to the configure command,  pcretest  is  linked  with  the  libreadline
446         library, and when its input is from a terminal, it reads it  using  the         library,  and  when its input is from a terminal, it reads it using the
447         readline() function. This provides line-editing and history facilities.         readline() function. This provides line-editing and history facilities.
448         Note that libreadline is GPL-licenced, so if you distribute a binary of         Note that libreadline is GPL-licensed, so if you distribute a binary of
449         pcretest linked in this way, there may be licensing issues.         pcretest linked in this way, there may be licensing issues.
450    
451         Setting  this  option  causes  the -lreadline option to be added to the         Setting this option causes the -lreadline option to  be  added  to  the
452         pcretest build. In many operating environments with  a  sytem-installed         pcretest  build.  In many operating environments with a sytem-installed
453         libreadline this is sufficient. However, in some environments (e.g.  if         libreadline this is sufficient. However, in some environments (e.g.  if
454         an unmodified distribution version of readline is in use),  some  extra         an  unmodified  distribution version of readline is in use), some extra
455         configuration  may  be necessary. The INSTALL file for libreadline says         configuration may be necessary. The INSTALL file for  libreadline  says
456         this:         this:
457    
458           "Readline uses the termcap functions, but does not link with the           "Readline uses the termcap functions, but does not link with the
459           termcap or curses library itself, allowing applications which link           termcap or curses library itself, allowing applications which link
460           with readline the to choose an appropriate library."           with readline the to choose an appropriate library."
461    
462         If your environment has not been set up so that an appropriate  library         If  your environment has not been set up so that an appropriate library
463         is automatically included, you may need to add something like         is automatically included, you may need to add something like
464    
465           LIBS="-ncurses"           LIBS="-ncurses"
# Line 578  AUTHOR Line 481  AUTHOR
481    
482  REVISION  REVISION
483    
484         Last updated: 13 April 2008         Last updated: 06 September 2011
485         Copyright (c) 1997-2008 University of Cambridge.         Copyright (c) 1997-2011 University of Cambridge.
486  ------------------------------------------------------------------------------  ------------------------------------------------------------------------------
487    
488    
# Line 666  THE ALTERNATIVE MATCHING ALGORITHM Line 569  THE ALTERNATIVE MATCHING ALGORITHM
569         though  it is not implemented as a traditional finite state machine (it         though  it is not implemented as a traditional finite state machine (it
570         keeps multiple states active simultaneously).         keeps multiple states active simultaneously).
571    
572           Although the general principle of this matching algorithm  is  that  it
573           scans  the subject string only once, without backtracking, there is one
574           exception: when a lookaround assertion is encountered,  the  characters
575           following  or  preceding  the  current  point  have to be independently
576           inspected.
577    
578         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
579         there  are  no more unterminated paths. At this point, terminated paths         there  are  no more unterminated paths. At this point, terminated paths
580         represent the different matching possibilities (if there are none,  the         represent the different matching possibilities (if there are none,  the
581         match  has  failed).   Thus,  if there is more than one possible match,         match  has  failed).   Thus,  if there is more than one possible match,
582         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-
583         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
584         match (which is necessarily the shortest) has been found.         an option to stop the algorithm after the first match (which is  neces-
585           sarily the shortest) is found.
586    
587         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
588         subject. If the pattern         subject. If the pattern
589    
590           cat(er(pillar)?)           cat(er(pillar)?)?
591    
592         is  matched  against the string "the caterpillar catchment", the result         is matched against the string "the caterpillar catchment",  the  result
593         will be the three strings "cat", "cater", and "caterpillar" that  start         will  be the three strings "caterpillar", "cater", and "cat" that start
594         at the fourth character of the subject. The algorithm does not automat-         at the fifth character of the subject. The algorithm does not automati-
595         ically move on to find matches that start at later positions.         cally move on to find matches that start at later positions.
596    
597         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
598         supported by the alternative matching algorithm. They are as follows:         supported by the alternative matching algorithm. They are as follows:
599    
600         1.  Because  the  algorithm  finds  all possible matches, the greedy or         1. Because the algorithm finds all  possible  matches,  the  greedy  or
601         ungreedy nature of repetition quantifiers is not relevant.  Greedy  and         ungreedy  nature  of repetition quantifiers is not relevant. Greedy and
602         ungreedy quantifiers are treated in exactly the same way. However, pos-         ungreedy quantifiers are treated in exactly the same way. However, pos-
603         sessive quantifiers can make a difference when what follows could  also         sessive  quantifiers can make a difference when what follows could also
604         match what is quantified, for example in a pattern like this:         match what is quantified, for example in a pattern like this:
605    
606           ^a++\w!           ^a++\w!
607    
608         This  pattern matches "aaab!" but not "aaa!", which would be matched by         This pattern matches "aaab!" but not "aaa!", which would be matched  by
609         a non-possessive quantifier. Similarly, if an atomic group is  present,         a  non-possessive quantifier. Similarly, if an atomic group is present,
610         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,
611         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
612         pattern.         pattern.
613    
614         2. When dealing with multiple paths through the tree simultaneously, it         2. When dealing with multiple paths through the tree simultaneously, it
615         is not straightforward to keep track of  captured  substrings  for  the         is  not  straightforward  to  keep track of captured substrings for the
616         different  matching  possibilities,  and  PCRE's implementation of this         different matching possibilities, and  PCRE's  implementation  of  this
617         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-
618         strings are available.         strings are available.
619    
620         3.  Because no substrings are captured, back references within the pat-         3. Because no substrings are captured, back references within the  pat-
621         tern are not supported, and cause errors if encountered.         tern are not supported, and cause errors if encountered.
622    
623         4. For the same reason, conditional expressions that use  a  backrefer-         4.  For  the same reason, conditional expressions that use a backrefer-
624         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
625         supported.         supported.
626    
627         5. Because many paths through the tree may be  active,  the  \K  escape         5.  Because  many  paths  through the tree may be active, the \K escape
628         sequence, which resets the start of the match when encountered (but may         sequence, which resets the start of the match when encountered (but may
629         be on some paths and not on others), is not  supported.  It  causes  an         be  on  some  paths  and not on others), is not supported. It causes an
630         error if encountered.         error if encountered.
631    
632         6.  Callouts  are  supported, but the value of the capture_top field is         6. Callouts are supported, but the value of the  capture_top  field  is
633         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.
634    
635         7. The \C escape sequence, which (in the standard algorithm) matches  a         7.  The \C escape sequence, which (in the standard algorithm) matches a
636         single  byte, even in UTF-8 mode, is not supported because the alterna-         single byte, even in UTF-8  mode,  is  not  supported  in  UTF-8  mode,
637         tive algorithm moves through the subject  string  one  character  at  a         because  the alternative algorithm moves through the subject string one
638         time, for all active paths through the tree.         character at a time, for all active paths through the tree.
639    
640         8.  Except for (*FAIL), the backtracking control verbs such as (*PRUNE)         8. Except for (*FAIL), the backtracking control verbs such as  (*PRUNE)
641         are not supported. (*FAIL) is supported, and  behaves  like  a  failing         are  not  supported.  (*FAIL)  is supported, and behaves like a failing
642         negative assertion.         negative assertion.
643    
644    
645  ADVANTAGES OF THE ALTERNATIVE ALGORITHM  ADVANTAGES OF THE ALTERNATIVE ALGORITHM
646    
647         Using  the alternative matching algorithm provides the following advan-         Using the alternative matching algorithm provides the following  advan-
648         tages:         tages:
649    
650         1. All possible matches (at a single point in the subject) are automat-         1. All possible matches (at a single point in the subject) are automat-
651         ically  found,  and  in particular, the longest match is found. To find         ically found, and in particular, the longest match is  found.  To  find
652         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
653         things with callouts.         things with callouts.
654    
655         2.  There is much better support for partial matching. The restrictions         2. Because the alternative algorithm  scans  the  subject  string  just
656         on the content of the pattern that apply when using the standard  algo-         once,  and  never  needs to backtrack, it is possible to pass very long
657         rithm  for  partial matching do not apply to the alternative algorithm.         subject strings to the matching function in  several  pieces,  checking
658         For non-anchored patterns, the starting position of a partial match  is         for  partial  matching  each time. Although it is possible to do multi-
659         available.         segment matching using the standard algorithm (pcre_exec()), by retain-
660           ing  partially matched substrings, it is more complicated. The pcrepar-
661         3.  Because  the  alternative  algorithm  scans the subject string just         tial documentation gives details  of  partial  matching  and  discusses
662         once, and never needs to backtrack, it is possible to  pass  very  long         multi-segment matching.
        subject  strings  to  the matching function in several pieces, checking  
        for partial matching each time.  
663    
664    
665  DISADVANTAGES OF THE ALTERNATIVE ALGORITHM  DISADVANTAGES OF THE ALTERNATIVE ALGORITHM
666    
667         The alternative algorithm suffers from a number of disadvantages:         The alternative algorithm suffers from a number of disadvantages:
668    
669         1. It is substantially slower than  the  standard  algorithm.  This  is         1.  It  is  substantially  slower  than the standard algorithm. This is
670         partly  because  it has to search for all possible matches, but is also         partly because it has to search for all possible matches, but  is  also
671         because it is less susceptible to optimization.         because it is less susceptible to optimization.
672    
673         2. Capturing parentheses and back references are not supported.         2. Capturing parentheses and back references are not supported.
# Line 777  AUTHOR Line 685  AUTHOR
685    
686  REVISION  REVISION
687    
688         Last updated: 19 April 2008         Last updated: 19 November 2011
689         Copyright (c) 1997-2008 University of Cambridge.         Copyright (c) 1997-2010 University of Cambridge.
690  ------------------------------------------------------------------------------  ------------------------------------------------------------------------------
691    
692    
# Line 789  NAME Line 697  NAME
697         PCRE - Perl-compatible regular expressions         PCRE - Perl-compatible regular expressions
698    
699    
700  PCRE NATIVE API  PCRE NATIVE API BASIC FUNCTIONS
701    
702         #include <pcre.h>         #include <pcre.h>
703    
# Line 805  PCRE NATIVE API Line 713  PCRE NATIVE API
713         pcre_extra *pcre_study(const pcre *code, int options,         pcre_extra *pcre_study(const pcre *code, int options,
714              const char **errptr);              const char **errptr);
715    
716           void pcre_free_study(pcre_extra *extra);
717    
718         int pcre_exec(const pcre *code, const pcre_extra *extra,         int pcre_exec(const pcre *code, const pcre_extra *extra,
719              const char *subject, int length, int startoffset,              const char *subject, int length, int startoffset,
720              int options, int *ovector, int ovecsize);              int options, int *ovector, int ovecsize);
721    
722    
723    PCRE NATIVE API AUXILIARY FUNCTIONS
724    
725           pcre_jit_stack *pcre_jit_stack_alloc(int startsize, int maxsize);
726    
727           void pcre_jit_stack_free(pcre_jit_stack *stack);
728    
729           void pcre_assign_jit_stack(pcre_extra *extra,
730                pcre_jit_callback callback, void *data);
731    
732         int pcre_dfa_exec(const pcre *code, const pcre_extra *extra,         int pcre_dfa_exec(const pcre *code, const pcre_extra *extra,
733              const char *subject, int length, int startoffset,              const char *subject, int length, int startoffset,
734              int options, int *ovector, int ovecsize,              int options, int *ovector, int ovecsize,
# Line 858  PCRE NATIVE API Line 778  PCRE NATIVE API
778    
779         char *pcre_version(void);         char *pcre_version(void);
780    
781    
782    PCRE NATIVE API INDIRECTED FUNCTIONS
783    
784         void *(*pcre_malloc)(size_t);         void *(*pcre_malloc)(size_t);
785    
786         void (*pcre_free)(void *);         void (*pcre_free)(void *);
# Line 873  PCRE API OVERVIEW Line 796  PCRE API OVERVIEW
796    
797         PCRE has its own native API, which is described in this document. There         PCRE has its own native API, which is described in this document. There
798         are also some wrapper functions that correspond to  the  POSIX  regular         are also some wrapper functions that correspond to  the  POSIX  regular
799         expression  API.  These  are  described in the pcreposix documentation.         expression  API,  but they do not give access to all the functionality.
800         Both of these APIs define a set of C function calls. A C++  wrapper  is         They are described in the pcreposix documentation. Both of  these  APIs
801         distributed with PCRE. It is documented in the pcrecpp page.         define  a  set  of  C function calls. A C++ wrapper is also distributed
802           with PCRE. It is documented in the pcrecpp page.
803    
804         The  native  API  C  function prototypes are defined in the header file         The native API C function prototypes are defined  in  the  header  file
805         pcre.h, and on Unix systems the library itself is called  libpcre.   It         pcre.h,  and  on Unix systems the library itself is called libpcre.  It
806         can normally be accessed by adding -lpcre to the command for linking an         can normally be accessed by adding -lpcre to the command for linking an
807         application  that  uses  PCRE.  The  header  file  defines  the  macros         application  that  uses  PCRE.  The  header  file  defines  the  macros
808         PCRE_MAJOR  and  PCRE_MINOR to contain the major and minor release num-         PCRE_MAJOR and PCRE_MINOR to contain the major and minor  release  num-
809         bers for the library.  Applications can use these  to  include  support         bers  for  the  library.  Applications can use these to include support
810         for different releases of PCRE.         for different releases of PCRE.
811    
812         The   functions   pcre_compile(),  pcre_compile2(),  pcre_study(),  and         In a Windows environment, if you want to statically link an application
813         pcre_exec() are used for compiling and matching regular expressions  in         program  against  a  non-dll  pcre.a  file, you must define PCRE_STATIC
814         a  Perl-compatible  manner. A sample program that demonstrates the sim-         before including pcre.h or pcrecpp.h, because otherwise  the  pcre_mal-
815         plest way of using them is provided in the file  called  pcredemo.c  in         loc()   and   pcre_free()   exported   functions   will   be   declared
816         the  source distribution. The pcresample documentation describes how to         __declspec(dllimport), with unwanted results.
817         compile and run it.  
818           The  functions  pcre_compile(),  pcre_compile2(),   pcre_study(),   and
819           pcre_exec()  are used for compiling and matching regular expressions in
820           a Perl-compatible manner. A sample program that demonstrates  the  sim-
821           plest  way  of  using them is provided in the file called pcredemo.c in
822           the PCRE source distribution. A listing of this program is given in the
823           pcredemo  documentation, and the pcresample documentation describes how
824           to compile and run it.
825    
826           Just-in-time compiler support is an optional feature of PCRE  that  can
827           be built in appropriate hardware environments. It greatly speeds up the
828           matching performance of  many  patterns.  Simple  programs  can  easily
829           request  that  it  be  used  if available, by setting an option that is
830           ignored when it is not relevant. More complicated programs  might  need
831           to     make    use    of    the    functions    pcre_jit_stack_alloc(),
832           pcre_jit_stack_free(), and pcre_assign_jit_stack() in order to  control
833           the  JIT  code's  memory  usage.   These functions are discussed in the
834           pcrejit documentation.
835    
836         A second matching function, pcre_dfa_exec(), which is not Perl-compati-         A second matching function, pcre_dfa_exec(), which is not Perl-compati-
837         ble,  is  also provided. This uses a different algorithm for the match-         ble,  is  also provided. This uses a different algorithm for the match-
838         ing. The alternative algorithm finds all possible matches (at  a  given         ing. The alternative algorithm finds all possible matches (at  a  given
839         point  in  the subject), and scans the subject just once. However, this         point  in  the  subject), and scans the subject just once (unless there
840         algorithm does not return captured substrings. A description of the two         are lookbehind assertions). However, this  algorithm  does  not  return
841         matching  algorithms and their advantages and disadvantages is given in         captured  substrings.  A description of the two matching algorithms and
842         the pcrematching documentation.         their advantages and disadvantages is given in the  pcrematching  docu-
843           mentation.
844    
845         In addition to the main compiling and  matching  functions,  there  are         In  addition  to  the  main compiling and matching functions, there are
846         convenience functions for extracting captured substrings from a subject         convenience functions for extracting captured substrings from a subject
847         string that is matched by pcre_exec(). They are:         string that is matched by pcre_exec(). They are:
848    
# Line 915  PCRE API OVERVIEW Line 857  PCRE API OVERVIEW
857         pcre_free_substring() and pcre_free_substring_list() are also provided,         pcre_free_substring() and pcre_free_substring_list() are also provided,
858         to free the memory used for extracted strings.         to free the memory used for extracted strings.
859    
860         The  function  pcre_maketables()  is  used  to build a set of character         The function pcre_maketables() is used to  build  a  set  of  character
861         tables  in  the  current  locale   for   passing   to   pcre_compile(),         tables   in   the   current   locale  for  passing  to  pcre_compile(),
862         pcre_exec(),  or  pcre_dfa_exec(). This is an optional facility that is         pcre_exec(), or pcre_dfa_exec(). This is an optional facility  that  is
863         provided for specialist use.  Most  commonly,  no  special  tables  are         provided  for  specialist  use.  Most  commonly,  no special tables are
864         passed,  in  which case internal tables that are generated when PCRE is         passed, in which case internal tables that are generated when  PCRE  is
865         built are used.         built are used.
866    
867         The function pcre_fullinfo() is used to find out  information  about  a         The  function  pcre_fullinfo()  is used to find out information about a
868         compiled  pattern; pcre_info() is an obsolete version that returns only         compiled pattern; pcre_info() is an obsolete version that returns  only
869         some of the available information, but is retained for  backwards  com-         some  of  the available information, but is retained for backwards com-
870         patibility.   The function pcre_version() returns a pointer to a string         patibility.  The function pcre_version() returns a pointer to a  string
871         containing the version of PCRE and its date of release.         containing the version of PCRE and its date of release.
872    
873         The function pcre_refcount() maintains a  reference  count  in  a  data         The  function  pcre_refcount()  maintains  a  reference count in a data
874         block  containing  a compiled pattern. This is provided for the benefit         block containing a compiled pattern. This is provided for  the  benefit
875         of object-oriented applications.         of object-oriented applications.
876    
877         The global variables pcre_malloc and pcre_free  initially  contain  the         The  global  variables  pcre_malloc and pcre_free initially contain the
878         entry  points  of  the  standard malloc() and free() functions, respec-         entry points of the standard malloc()  and  free()  functions,  respec-
879         tively. PCRE calls the memory management functions via these variables,         tively. PCRE calls the memory management functions via these variables,
880         so  a  calling  program  can replace them if it wishes to intercept the         so a calling program can replace them if it  wishes  to  intercept  the
881         calls. This should be done before calling any PCRE functions.         calls. This should be done before calling any PCRE functions.
882    
883         The global variables pcre_stack_malloc  and  pcre_stack_free  are  also         The  global  variables  pcre_stack_malloc  and pcre_stack_free are also
884         indirections  to  memory  management functions. These special functions         indirections to memory management functions.  These  special  functions
885         are used only when PCRE is compiled to use  the  heap  for  remembering         are  used  only  when  PCRE is compiled to use the heap for remembering
886         data, instead of recursive function calls, when running the pcre_exec()         data, instead of recursive function calls, when running the pcre_exec()
887         function. See the pcrebuild documentation for  details  of  how  to  do         function.  See  the  pcrebuild  documentation  for details of how to do
888         this.  It  is  a non-standard way of building PCRE, for use in environ-         this. It is a non-standard way of building PCRE, for  use  in  environ-
889         ments that have limited stacks. Because of the greater  use  of  memory         ments  that  have  limited stacks. Because of the greater use of memory
890         management,  it  runs  more  slowly. Separate functions are provided so         management, it runs more slowly. Separate  functions  are  provided  so
891         that special-purpose external code can be  used  for  this  case.  When         that  special-purpose  external  code  can  be used for this case. When
892         used,  these  functions  are always called in a stack-like manner (last         used, these functions are always called in a  stack-like  manner  (last
893         obtained, first freed), and always for memory blocks of the same  size.         obtained,  first freed), and always for memory blocks of the same size.
894         There  is  a discussion about PCRE's stack usage in the pcrestack docu-         There is a discussion about PCRE's stack usage in the  pcrestack  docu-
895         mentation.         mentation.
896    
897         The global variable pcre_callout initially contains NULL. It can be set         The global variable pcre_callout initially contains NULL. It can be set
898         by  the  caller  to  a "callout" function, which PCRE will then call at         by the caller to a "callout" function, which PCRE  will  then  call  at
899         specified points during a matching operation. Details are given in  the         specified  points during a matching operation. Details are given in the
900         pcrecallout documentation.         pcrecallout documentation.
901    
902    
903  NEWLINES  NEWLINES
904    
905         PCRE  supports five different conventions for indicating line breaks in         PCRE supports five different conventions for indicating line breaks  in
906         strings: a single CR (carriage return) character, a  single  LF  (line-         strings:  a  single  CR (carriage return) character, a single LF (line-
907         feed) character, the two-character sequence CRLF, any of the three pre-         feed) character, the two-character sequence CRLF, any of the three pre-
908         ceding, or any Unicode newline sequence. The Unicode newline  sequences         ceding,  or any Unicode newline sequence. The Unicode newline sequences
909         are  the  three just mentioned, plus the single characters VT (vertical         are the three just mentioned, plus the single characters  VT  (vertical
910         tab, U+000B), FF (formfeed, U+000C), NEL (next line, U+0085), LS  (line         tab,  U+000B), FF (formfeed, U+000C), NEL (next line, U+0085), LS (line
911         separator, U+2028), and PS (paragraph separator, U+2029).         separator, U+2028), and PS (paragraph separator, U+2029).
912    
913         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
914         system as its standard newline sequence. When PCRE is built, a  default         system  as its standard newline sequence. When PCRE is built, a default
915         can  be  specified.  The default default is LF, which is the Unix stan-         can be specified.  The default default is LF, which is the  Unix  stan-
916         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
917         pattern is compiled, or when it is matched.         pattern is compiled, or when it is matched.
918    
919         At compile time, the newline convention can be specified by the options         At compile time, the newline convention can be specified by the options
920         argument of pcre_compile(), or it can be specified by special  text  at         argument  of  pcre_compile(), or it can be specified by special text at
921         the start of the pattern itself; this overrides any other settings. See         the start of the pattern itself; this overrides any other settings. See
922         the pcrepattern page for details of the special character sequences.         the pcrepattern page for details of the special character sequences.
923    
924         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-
925         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
926         newline convention affects the handling of  the  dot,  circumflex,  and         newline  convention  affects  the  handling of the dot, circumflex, and
927         dollar metacharacters, the handling of #-comments in /x mode, and, when         dollar metacharacters, the handling of #-comments in /x mode, and, when
928         CRLF is a recognized line ending sequence, the match position  advance-         CRLF  is a recognized line ending sequence, the match position advance-
929         ment for a non-anchored pattern. There is more detail about this in the         ment for a non-anchored pattern. There is more detail about this in the
930         section on pcre_exec() options below.         section on pcre_exec() options below.
931    
932         The choice of newline convention does not affect the interpretation  of         The  choice of newline convention does not affect the interpretation of
933         the  \n  or  \r  escape  sequences, nor does it affect what \R matches,         the \n or \r escape sequences, nor does  it  affect  what  \R  matches,
934         which is controlled in a similar way, but by separate options.         which is controlled in a similar way, but by separate options.
935    
936    
937  MULTITHREADING  MULTITHREADING
938    
939         The PCRE functions can be used in  multi-threading  applications,  with         The  PCRE  functions  can be used in multi-threading applications, with
940         the  proviso  that  the  memory  management  functions  pointed  to  by         the  proviso  that  the  memory  management  functions  pointed  to  by
941         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
942         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 1003  MULTITHREADING Line 945  MULTITHREADING
945         ing, so the same compiled pattern can safely be used by several threads         ing, so the same compiled pattern can safely be used by several threads
946         at once.         at once.
947    
948           If the just-in-time optimization feature is being used, it needs  sepa-
949           rate  memory stack areas for each thread. See the pcrejit documentation
950           for more details.
951    
952    
953  SAVING PRECOMPILED PATTERNS FOR LATER USE  SAVING PRECOMPILED PATTERNS FOR LATER USE
954    
# Line 1038  CHECKING BUILD-TIME OPTIONS Line 984  CHECKING BUILD-TIME OPTIONS
984         The output is an integer that is set to  one  if  support  for  Unicode         The output is an integer that is set to  one  if  support  for  Unicode
985         character properties is available; otherwise it is set to zero.         character properties is available; otherwise it is set to zero.
986    
987             PCRE_CONFIG_JIT
988    
989           The output is an integer that is set to one if support for just-in-time
990           compiling is available; otherwise it is set to zero.
991    
992           PCRE_CONFIG_NEWLINE           PCRE_CONFIG_NEWLINE
993    
994         The  output  is  an integer whose value specifies the default character         The output is an integer whose value specifies  the  default  character
995         sequence that is recognized as meaning "newline". The four values  that         sequence  that is recognized as meaning "newline". The four values that
996         are supported are: 10 for LF, 13 for CR, 3338 for CRLF, -2 for ANYCRLF,         are supported are: 10 for LF, 13 for CR, 3338 for CRLF, -2 for ANYCRLF,
997         and -1 for ANY. The default should normally be  the  standard  sequence         and  -1  for  ANY.  Though they are derived from ASCII, the same values
998         for your operating system.         are returned in EBCDIC environments. The default should normally corre-
999           spond to the standard sequence for your operating system.
1000    
1001           PCRE_CONFIG_BSR           PCRE_CONFIG_BSR
1002    
# Line 1071  CHECKING BUILD-TIME OPTIONS Line 1023  CHECKING BUILD-TIME OPTIONS
1023    
1024           PCRE_CONFIG_MATCH_LIMIT           PCRE_CONFIG_MATCH_LIMIT
1025    
1026         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-
1027         internal  matching  function  calls in a pcre_exec() execution. Further         ber  of  internal  matching  function calls in a pcre_exec() execution.
1028         details are given with pcre_exec() below.         Further details are given with pcre_exec() below.
1029    
1030           PCRE_CONFIG_MATCH_LIMIT_RECURSION           PCRE_CONFIG_MATCH_LIMIT_RECURSION
1031    
1032         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
1033         recursion  when calling the internal matching function in a pcre_exec()         of   recursion  when  calling  the  internal  matching  function  in  a
1034         execution. Further details are given with pcre_exec() below.         pcre_exec() execution.  Further  details  are  given  with  pcre_exec()
1035           below.
1036    
1037           PCRE_CONFIG_STACKRECURSE           PCRE_CONFIG_STACKRECURSE
1038    
1039         The output is an integer that is set to one if internal recursion  when         The  output is an integer that is set to one if internal recursion when
1040         running pcre_exec() is implemented by recursive function calls that use         running pcre_exec() is implemented by recursive function calls that use
1041         the stack to remember their state. This is the usual way that  PCRE  is         the  stack  to remember their state. This is the usual way that PCRE is
1042         compiled. The output is zero if PCRE was compiled to use blocks of data         compiled. The output is zero if PCRE was compiled to use blocks of data
1043         on the  heap  instead  of  recursive  function  calls.  In  this  case,         on  the  heap  instead  of  recursive  function  calls.  In  this case,
1044         pcre_stack_malloc  and  pcre_stack_free  are  called  to  manage memory         pcre_stack_malloc and  pcre_stack_free  are  called  to  manage  memory
1045         blocks on the heap, thus avoiding the use of the stack.         blocks on the heap, thus avoiding the use of the stack.
1046    
1047    
# Line 1105  COMPILING A PATTERN Line 1058  COMPILING A PATTERN
1058    
1059         Either of the functions pcre_compile() or pcre_compile2() can be called         Either of the functions pcre_compile() or pcre_compile2() can be called
1060         to compile a pattern into an internal form. The only difference between         to compile a pattern into an internal form. The only difference between
1061         the two interfaces is that pcre_compile2() has an additional  argument,         the  two interfaces is that pcre_compile2() has an additional argument,
1062         errorcodeptr, via which a numerical error code can be returned.         errorcodeptr, via which a numerical error  code  can  be  returned.  To
1063           avoid  too  much repetition, we refer just to pcre_compile() below, but
1064           the information applies equally to pcre_compile2().
1065    
1066         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
1067         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
1068         obtained  via  pcre_malloc is returned. This contains the compiled code         obtained via pcre_malloc is returned. This contains the  compiled  code
1069         and related data. The pcre type is defined for the returned block; this         and related data. The pcre type is defined for the returned block; this
1070         is a typedef for a structure whose contents are not externally defined.         is a typedef for a structure whose contents are not externally defined.
1071         It is up to the caller to free the memory (via pcre_free) when it is no         It is up to the caller to free the memory (via pcre_free) when it is no
1072         longer required.         longer required.
1073    
1074         Although  the compiled code of a PCRE regex is relocatable, that is, it         Although the compiled code of a PCRE regex is relocatable, that is,  it
1075         does not depend on memory location, the complete pcre data block is not         does not depend on memory location, the complete pcre data block is not
1076         fully  relocatable, because it may contain a copy of the tableptr argu-         fully relocatable, because it may contain a copy of the tableptr  argu-
1077         ment, which is an address (see below).         ment, which is an address (see below).
1078    
1079         The options argument contains various bit settings that affect the com-         The options argument contains various bit settings that affect the com-
1080         pilation.  It  should be zero if no options are required. The available         pilation. It should be zero if no options are required.  The  available
1081         options are described below. Some of them, in  particular,  those  that         options  are  described  below. Some of them (in particular, those that
1082         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
1083         pattern (see the detailed description  in  the  pcrepattern  documenta-         unset  from  within  the  pattern  (see the detailed description in the
1084         tion).  For  these options, the contents of the options argument speci-         pcrepattern documentation). For those options that can be different  in
1085         fies their initial settings at the start of compilation and  execution.         different  parts  of  the pattern, the contents of the options argument
1086         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
1087         of matching as well as at compile time.         PCRE_ANCHORED,  PCRE_BSR_xxx, PCRE_NEWLINE_xxx, PCRE_NO_UTF8_CHECK, and
1088           PCRE_NO_START_OPT options can be set at the time of matching as well as
1089           at compile time.
1090    
1091         If errptr is NULL, pcre_compile() returns NULL immediately.  Otherwise,         If errptr is NULL, pcre_compile() returns NULL immediately.  Otherwise,
1092         if  compilation  of  a  pattern fails, pcre_compile() returns NULL, and         if compilation of a pattern fails,  pcre_compile()  returns  NULL,  and
1093         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-
1094         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
1095         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
1096         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
1097         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
1098         given.         (if it is, an immediate error is given). However, for an invalid  UTF-8
1099           string,  the offset is that of the first byte of the failing character.
1100           Also, some errors are not detected until checks are  carried  out  when
1101           the  whole  pattern  has been scanned; in these cases the offset passed
1102           back is the length of the pattern.
1103    
1104           Note that the offset is in bytes, not characters, even in  UTF-8  mode.
1105           It may sometimes point into the middle of a UTF-8 character.
1106    
1107         If  pcre_compile2()  is  used instead of pcre_compile(), and the error-         If  pcre_compile2()  is  used instead of pcre_compile(), and the error-
1108         codeptr argument is not NULL, a non-zero error code number is  returned         codeptr argument is not NULL, a non-zero error code number is  returned
# Line 1216  COMPILING A PATTERN Line 1180  COMPILING A PATTERN
1180    
1181           PCRE_DOTALL           PCRE_DOTALL
1182    
1183         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-
1184         acters,  including  those that indicate newline. Without it, a dot does         acter of any value, including one that indicates a newline. However, it
1185         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.
1186         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
1187         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
1188         newline characters, independent of the setting of this option.         be  changed within a pattern by a (?s) option setting. A negative class
1189           such as [^a] always matches newline characters, independent of the set-
1190           ting of this option.
1191    
1192           PCRE_DUPNAMES           PCRE_DUPNAMES
1193    
# Line 1241  COMPILING A PATTERN Line 1207  COMPILING A PATTERN
1207         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-
1208         ting.         ting.
1209    
1210         This  option  makes  it possible to include comments inside complicated         Which  characters  are  interpreted  as  newlines  is controlled by the
1211         patterns.  Note, however, that this applies only  to  data  characters.         options passed to pcre_compile() or by a special sequence at the  start
1212         Whitespace   characters  may  never  appear  within  special  character         of  the  pattern, as described in the section entitled "Newline conven-
1213         sequences in a pattern, for  example  within  the  sequence  (?(  which         tions" in the pcrepattern documentation. Note that the end of this type
1214         introduces a conditional subpattern.         of  comment  is  a  literal  newline  sequence  in  the pattern; escape
1215           sequences that happen to represent a newline do not count.
1216    
1217           This option makes it possible to include  comments  inside  complicated
1218           patterns.   Note,  however,  that this applies only to data characters.
1219           Whitespace  characters  may  never  appear  within  special   character
1220           sequences in a pattern, for example within the sequence (?( that intro-
1221           duces a conditional subpattern.
1222    
1223           PCRE_EXTRA           PCRE_EXTRA
1224    
1225         This  option  was invented in order to turn on additional functionality         This option was invented in order to turn on  additional  functionality
1226         of PCRE that is incompatible with Perl, but it  is  currently  of  very         of  PCRE  that  is  incompatible with Perl, but it is currently of very
1227         little  use. When set, any backslash in a pattern that is followed by a         little use. When set, any backslash in a pattern that is followed by  a
1228         letter that has no special meaning  causes  an  error,  thus  reserving         letter  that  has  no  special  meaning causes an error, thus reserving
1229         these  combinations  for  future  expansion.  By default, as in Perl, a         these combinations for future expansion. By  default,  as  in  Perl,  a
1230         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
1231         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
1232         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
1233         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
1234           within a pattern.
1235    
1236           PCRE_FIRSTLINE           PCRE_FIRSTLINE
1237    
# Line 1282  COMPILING A PATTERN Line 1256  COMPILING A PATTERN
1256         set  (assuming  it can find an "a" in the subject), whereas it fails by         set  (assuming  it can find an "a" in the subject), whereas it fails by
1257         default, for Perl compatibility.         default, for Perl compatibility.
1258    
1259           (3) \U matches an upper case "U" character; by default \U causes a com-
1260           pile time error (Perl uses \U to upper case subsequent characters).
1261    
1262           (4) \u matches a lower case "u" character unless it is followed by four
1263           hexadecimal digits, in which case the hexadecimal  number  defines  the
1264           code  point  to match. By default, \u causes a compile time error (Perl
1265           uses it to upper case the following character).
1266    
1267           (5) \x matches a lower case "x" character unless it is followed by  two
1268           hexadecimal  digits,  in  which case the hexadecimal number defines the
1269           code point to match. By default, as in Perl, a  hexadecimal  number  is
1270           always expected after \x, but it may have zero, one, or two digits (so,
1271           for example, \xz matches a binary zero character followed by z).
1272    
1273           PCRE_MULTILINE           PCRE_MULTILINE
1274    
1275         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 1326  COMPILING A PATTERN Line 1314  COMPILING A PATTERN
1314         PCRE_NEWLINE_CRLF,  but other combinations may yield unused numbers and         PCRE_NEWLINE_CRLF,  but other combinations may yield unused numbers and
1315         cause an error.         cause an error.
1316    
1317         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
1318         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
1319         character class is encountered. This indicates  a  comment  that  lasts         characters, and so are ignored in this mode. Also, an unescaped #  out-
1320         until  after the next line break sequence. In other circumstances, line         side  a  character class indicates a comment that lasts until after the
1321         break  sequences  are  treated  as  literal  data,   except   that   in         next line break sequence. In other circumstances, line break  sequences
1322         PCRE_EXTENDED mode, both CR and LF are treated as whitespace characters         in patterns are treated as literal data.
        and are therefore ignored.  
1323    
1324         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
1325         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.
1326    
1327           PCRE_NO_AUTO_CAPTURE           PCRE_NO_AUTO_CAPTURE
1328    
# Line 1345  COMPILING A PATTERN Line 1332  COMPILING A PATTERN
1332         be  used  for  capturing  (and  they acquire numbers in the usual way).         be  used  for  capturing  (and  they acquire numbers in the usual way).
1333         There is no equivalent of this option in Perl.         There is no equivalent of this option in Perl.
1334    
1335             NO_START_OPTIMIZE
1336    
1337           This is an option that acts at matching time; that is, it is really  an
1338           option  for  pcre_exec()  or  pcre_dfa_exec().  If it is set at compile
1339           time, it is remembered with the compiled pattern and assumed at  match-
1340           ing  time.  For  details  see  the discussion of PCRE_NO_START_OPTIMIZE
1341           below.
1342    
1343             PCRE_UCP
1344    
1345           This option changes the way PCRE processes \B, \b, \D, \d, \S, \s,  \W,
1346           \w,  and  some  of  the POSIX character classes. By default, only ASCII
1347           characters are recognized, but if PCRE_UCP is set,  Unicode  properties
1348           are  used instead to classify characters. More details are given in the
1349           section on generic character types in the pcrepattern page. If you  set
1350           PCRE_UCP,  matching  one of the items it affects takes much longer. The
1351           option is available only if PCRE has been compiled with  Unicode  prop-
1352           erty support.
1353    
1354           PCRE_UNGREEDY           PCRE_UNGREEDY
1355    
1356         This option inverts the "greediness" of the quantifiers  so  that  they         This  option  inverts  the "greediness" of the quantifiers so that they
1357         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
1358         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
1359         within the pattern.         within the pattern.
1360    
1361           PCRE_UTF8           PCRE_UTF8
1362    
1363         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
1364         strings of UTF-8 characters instead of single-byte  character  strings.         strings  of  UTF-8 characters instead of single-byte character strings.
1365         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-
1366         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
1367         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
1368         UTF-8 support in the main pcre page.         page.
1369    
1370           PCRE_NO_UTF8_CHECK           PCRE_NO_UTF8_CHECK
1371    
1372         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
1373         automatically  checked.  There  is  a  discussion about the validity of         automatically checked. There is a  discussion  about  the  validity  of
1374         UTF-8 strings in the main pcre page. If an invalid  UTF-8  sequence  of         UTF-8  strings  in  the main pcre page. If an invalid UTF-8 sequence of
1375         bytes  is  found,  pcre_compile() returns an error. If you already know         bytes is found, pcre_compile() returns an error. If  you  already  know
1376         that your pattern is valid, and you want to skip this check for perfor-         that your pattern is valid, and you want to skip this check for perfor-
1377         mance  reasons,  you  can set the PCRE_NO_UTF8_CHECK option. When it is         mance reasons, you can set the PCRE_NO_UTF8_CHECK option.  When  it  is
1378         set, the effect of passing an invalid UTF-8  string  as  a  pattern  is         set,  the  effect  of  passing  an invalid UTF-8 string as a pattern is
1379         undefined.  It  may  cause your program to crash. Note that this option         undefined. It may cause your program to crash. Note  that  this  option
1380         can also be passed to pcre_exec() and pcre_dfa_exec(), to suppress  the         can  also be passed to pcre_exec() and pcre_dfa_exec(), to suppress the
1381         UTF-8 validity checking of subject strings.         UTF-8 validity checking of subject strings.
1382    
1383    
1384  COMPILATION ERROR CODES  COMPILATION ERROR CODES
1385    
1386         The  following  table  lists  the  error  codes than may be returned by         The following table lists the error  codes  than  may  be  returned  by
1387         pcre_compile2(), along with the error messages that may be returned  by         pcre_compile2(),  along with the error messages that may be returned by
1388         both  compiling functions. As PCRE has developed, some error codes have         both compiling functions. As PCRE has developed, some error codes  have
1389         fallen out of use. To avoid confusion, they have not been re-used.         fallen out of use. To avoid confusion, they have not been re-used.
1390    
1391            0  no error            0  no error
# Line 1419  COMPILATION ERROR CODES Line 1425  COMPILATION ERROR CODES
1425           34  character value in \x{...} sequence is too large           34  character value in \x{...} sequence is too large
1426           35  invalid condition (?(0)           35  invalid condition (?(0)
1427           36  \C not allowed in lookbehind assertion           36  \C not allowed in lookbehind assertion
1428           37  PCRE does not support \L, \l, \N, \U, or \u           37  PCRE does not support \L, \l, \N{name}, \U, or \u
1429           38  number after (?C is > 255           38  number after (?C is > 255
1430           39  closing ) for (?C expected           39  closing ) for (?C expected
1431           40  recursive call could loop indefinitely           40  recursive call could loop indefinitely
# Line 1435  COMPILATION ERROR CODES Line 1441  COMPILATION ERROR CODES
1441           50  [this code is not in use]           50  [this code is not in use]
1442           51  octal value is greater than \377 (not in UTF-8 mode)           51  octal value is greater than \377 (not in UTF-8 mode)
1443           52  internal error: overran compiling workspace           52  internal error: overran compiling workspace
1444           53  internal  error:  previously-checked  referenced  subpattern  not           53  internal error: previously-checked referenced subpattern
1445         found                 not found
1446           54  DEFINE group contains more than one branch           54  DEFINE group contains more than one branch
1447           55  repeating a DEFINE group is not allowed           55  repeating a DEFINE group is not allowed
1448           56  inconsistent NEWLINE options           56  inconsistent NEWLINE options
1449           57  \g is not followed by a braced, angle-bracketed, or quoted           57  \g is not followed by a braced, angle-bracketed, or quoted
1450                 name/number or by a plain number                 name/number or by a plain number
1451           58  a numbered reference must not be zero           58  a numbered reference must not be zero
1452           59  (*VERB) with an argument is not supported           59  an argument is not allowed for (*ACCEPT), (*FAIL), or (*COMMIT)
1453           60  (*VERB) not recognized           60  (*VERB) not recognized
1454           61  number is too big           61  number is too big
1455           62  subpattern name expected           62  subpattern name expected
1456           63  digit expected after (?+           63  digit expected after (?+
1457           64  ] is an invalid data character in JavaScript compatibility mode           64  ] is an invalid data character in JavaScript compatibility mode
1458             65  different names for subpatterns of the same number are
1459                   not allowed
1460             66  (*MARK) must have an argument
1461             67  this version of PCRE is not compiled with PCRE_UCP support
1462             68  \c must be followed by an ASCII character
1463             69  \k is not followed by a braced, angle-bracketed, or quoted name
1464    
1465         The  numbers  32  and 10000 in errors 48 and 49 are defaults; different         The  numbers  32  and 10000 in errors 48 and 49 are defaults; different
1466         values may be used if the limits were changed when PCRE was built.         values may be used if the limits were changed when PCRE was built.
# Line 1468  STUDYING A PATTERN Line 1480  STUDYING A PATTERN
1480         the results of the study.         the results of the study.
1481    
1482         The  returned  value  from  pcre_study()  can  be  passed  directly  to         The  returned  value  from  pcre_study()  can  be  passed  directly  to
1483         pcre_exec().  However,  a  pcre_extra  block also contains other fields         pcre_exec()  or  pcre_dfa_exec(). However, a pcre_extra block also con-
1484         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
1485         described below in the section on matching a pattern.         passed; these are described below in the section on matching a pattern.
1486    
1487         If  studying  the  pattern  does not produce any additional information         If  studying  the  pattern  does  not  produce  any useful information,
1488         pcre_study() returns NULL. In that circumstance, if the calling program         pcre_study() returns NULL. In that circumstance, if the calling program
1489         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
1490         its own pcre_extra block.         pcre_dfa_exec(), it must set up its own pcre_extra block.
1491    
1492         The second argument of pcre_study() contains option bits.  At  present,         The second argument of pcre_study() contains option bits. There is only
1493         no options are defined, and this argument should always be zero.         one  option:  PCRE_STUDY_JIT_COMPILE.  If this is set, and the just-in-
1494           time compiler is  available,  the  pattern  is  further  compiled  into
1495           machine  code  that  executes much faster than the pcre_exec() matching
1496           function. If the just-in-time compiler is not available, this option is
1497           ignored. All other bits in the options argument must be zero.
1498    
1499           JIT  compilation  is  a heavyweight optimization. It can take some time
1500           for patterns to be analyzed, and for one-off matches  and  simple  pat-
1501           terns  the benefit of faster execution might be offset by a much slower
1502           study time.  Not all patterns can be optimized by the JIT compiler. For
1503           those  that cannot be handled, matching automatically falls back to the
1504           pcre_exec() interpreter. For more details, see the  pcrejit  documenta-
1505           tion.
1506    
1507         The  third argument for pcre_study() is a pointer for an error message.         The  third argument for pcre_study() is a pointer for an error message.
1508         If studying succeeds (even if no data is  returned),  the  variable  it         If studying succeeds (even if no data is  returned),  the  variable  it
# Line 1487  STUDYING A PATTERN Line 1511  STUDYING A PATTERN
1511         must  not  try  to  free it. You should test the error pointer for NULL         must  not  try  to  free it. You should test the error pointer for NULL
1512         after calling pcre_study(), to be sure that it has run successfully.         after calling pcre_study(), to be sure that it has run successfully.
1513    
1514         This is a typical call to pcre_study():         When you are finished with a pattern, you can free the memory used  for
1515           the study data by calling pcre_free_study(). This function was added to
1516           the API for release 8.20. For earlier versions,  the  memory  could  be
1517           freed  with  pcre_free(), just like the pattern itself. This will still
1518           work in cases where PCRE_STUDY_JIT_COMPILE  is  not  used,  but  it  is
1519           advisable to change to the new function when convenient.
1520    
1521           pcre_extra *pe;         This  is  a typical way in which pcre_study() is used (except that in a
1522           pe = pcre_study(         real application there should be tests for errors):
1523    
1524             int rc;
1525             pcre *re;
1526             pcre_extra *sd;
1527             re = pcre_compile("pattern", 0, &error, &erroroffset, NULL);
1528             sd = pcre_study(
1529             re,             /* result of pcre_compile() */             re,             /* result of pcre_compile() */
1530             0,              /* no options exist */             0,              /* no options */
1531             &error);        /* set to NULL or points to a message */             &error);        /* set to NULL or points to a message */
1532             rc = pcre_exec(   /* see below for details of pcre_exec() options */
1533         At present, studying a pattern is useful only for non-anchored patterns             re, sd, "subject", 7, 0, 0, ovector, 30);
1534         that  do not have a single fixed starting character. A bitmap of possi-           ...
1535         ble starting bytes is created.           pcre_free_study(sd);
1536             pcre_free(re);
1537    
1538           Studying a pattern does two things: first, a lower bound for the length
1539           of subject string that is needed to match the pattern is computed. This
1540           does not mean that there are any strings of that length that match, but
1541           it  does  guarantee that no shorter strings match. The value is used by
1542           pcre_exec() and pcre_dfa_exec() to avoid  wasting  time  by  trying  to
1543           match  strings  that are shorter than the lower bound. You can find out
1544           the value in a calling program via the pcre_fullinfo() function.
1545    
1546           Studying a pattern is also useful for non-anchored patterns that do not
1547           have  a  single fixed starting character. A bitmap of possible starting
1548           bytes is created. This speeds up finding a position in the  subject  at
1549           which to start matching.
1550    
1551           These  two optimizations apply to both pcre_exec() and pcre_dfa_exec().
1552           However, they are not used by pcre_exec()  if  pcre_study()  is  called
1553           with  the  PCRE_STUDY_JIT_COMPILE option, and just-in-time compiling is
1554           successful.  The  optimizations  can  be  disabled   by   setting   the
1555           PCRE_NO_START_OPTIMIZE    option    when    calling    pcre_exec()   or
1556           pcre_dfa_exec(). You might want to do this  if  your  pattern  contains
1557           callouts  or (*MARK) (which cannot be handled by the JIT compiler), and
1558           you want to make use of these facilities in cases where matching fails.
1559           See the discussion of PCRE_NO_START_OPTIMIZE below.
1560    
1561    
1562  LOCALE SUPPORT  LOCALE SUPPORT
1563    
1564         PCRE handles caseless matching, and determines whether  characters  are         PCRE  handles  caseless matching, and determines whether characters are
1565         letters,  digits, or whatever, by reference to a set of tables, indexed         letters, digits, or whatever, by reference to a set of tables,  indexed
1566         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
1567         characters  with  codes  less than 128. Higher-valued codes never match         characters with codes less than 128. By  default,  higher-valued  codes
1568         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
1569         with  Unicode  character property support. The use of locales with Uni-         PCRE is built with Unicode character property  support.  Alternatively,
1570         code is discouraged. If you are handling characters with codes  greater         the  PCRE_UCP  option  can  be  set at compile time; this causes \w and
1571         than  128, you should either use UTF-8 and Unicode, or use locales, but         friends to use Unicode property support instead of built-in tables. The
1572         not try to mix the two.         use of locales with Unicode is discouraged. If you are handling charac-
1573           ters with codes greater than 128, you should either use UTF-8 and  Uni-
1574           code, or use locales, but not try to mix the two.
1575    
1576         PCRE contains an internal set of tables that are used  when  the  final         PCRE  contains  an  internal set of tables that are used when the final
1577         argument  of  pcre_compile()  is  NULL.  These  are sufficient for many         argument of pcre_compile() is  NULL.  These  are  sufficient  for  many
1578         applications.  Normally, the internal tables recognize only ASCII char-         applications.  Normally, the internal tables recognize only ASCII char-
1579         acters. However, when PCRE is built, it is possible to cause the inter-         acters. However, when PCRE is built, it is possible to cause the inter-
1580         nal tables to be rebuilt in the default "C" locale of the local system,         nal tables to be rebuilt in the default "C" locale of the local system,
1581         which may cause them to be different.         which may cause them to be different.
1582    
1583         The  internal tables can always be overridden by tables supplied by the         The internal tables can always be overridden by tables supplied by  the
1584         application that calls PCRE. These may be created in a different locale         application that calls PCRE. These may be created in a different locale
1585         from  the  default.  As more and more applications change to using Uni-         from the default. As more and more applications change  to  using  Uni-
1586         code, the need for this locale support is expected to die away.         code, the need for this locale support is expected to die away.
1587    
1588         External tables are built by calling  the  pcre_maketables()  function,         External  tables  are  built by calling the pcre_maketables() function,
1589         which  has no arguments, in the relevant locale. The result can then be         which has no arguments, in the relevant locale. The result can then  be
1590         passed to pcre_compile() or pcre_exec()  as  often  as  necessary.  For         passed  to  pcre_compile()  or  pcre_exec()  as often as necessary. For
1591         example,  to  build  and use tables that are appropriate for the French         example, to build and use tables that are appropriate  for  the  French
1592         locale (where accented characters with  values  greater  than  128  are         locale  (where  accented  characters  with  values greater than 128 are
1593         treated as letters), the following code could be used:         treated as letters), the following code could be used:
1594    
1595           setlocale(LC_CTYPE, "fr_FR");           setlocale(LC_CTYPE, "fr_FR");
1596           tables = pcre_maketables();           tables = pcre_maketables();
1597           re = pcre_compile(..., tables);           re = pcre_compile(..., tables);
1598    
1599         The  locale  name "fr_FR" is used on Linux and other Unix-like systems;         The locale name "fr_FR" is used on Linux and other  Unix-like  systems;
1600         if you are using Windows, the name for the French locale is "french".         if you are using Windows, the name for the French locale is "french".
1601    
1602         When pcre_maketables() runs, the tables are built  in  memory  that  is         When  pcre_maketables()  runs,  the  tables are built in memory that is
1603         obtained  via  pcre_malloc. It is the caller's responsibility to ensure         obtained via pcre_malloc. It is the caller's responsibility  to  ensure
1604         that the memory containing the tables remains available for as long  as         that  the memory containing the tables remains available for as long as
1605         it is needed.         it is needed.
1606    
1607         The pointer that is passed to pcre_compile() is saved with the compiled         The pointer that is passed to pcre_compile() is saved with the compiled
1608         pattern, and the same tables are used via this pointer by  pcre_study()         pattern,  and the same tables are used via this pointer by pcre_study()
1609         and normally also by pcre_exec(). Thus, by default, for any single pat-         and normally also by pcre_exec(). Thus, by default, for any single pat-
1610         tern, compilation, studying and matching all happen in the same locale,         tern, compilation, studying and matching all happen in the same locale,
1611         but different patterns can be compiled in different locales.         but different patterns can be compiled in different locales.
1612    
1613         It  is  possible to pass a table pointer or NULL (indicating the use of         It is possible to pass a table pointer or NULL (indicating the  use  of
1614         the internal tables) to pcre_exec(). Although  not  intended  for  this         the  internal  tables)  to  pcre_exec(). Although not intended for this
1615         purpose,  this facility could be used to match a pattern in a different         purpose, this facility could be used to match a pattern in a  different
1616         locale from the one in which it was compiled. Passing table pointers at         locale from the one in which it was compiled. Passing table pointers at
1617         run time is discussed below in the section on matching a pattern.         run time is discussed below in the section on matching a pattern.
1618    
# Line 1561  INFORMATION ABOUT A PATTERN Line 1622  INFORMATION ABOUT A PATTERN
1622         int pcre_fullinfo(const pcre *code, const pcre_extra *extra,         int pcre_fullinfo(const pcre *code, const pcre_extra *extra,
1623              int what, void *where);              int what, void *where);
1624    
1625         The  pcre_fullinfo() function returns information about a compiled pat-         The pcre_fullinfo() function returns information about a compiled  pat-
1626         tern. It replaces the obsolete pcre_info() function, which is neverthe-         tern. It replaces the obsolete pcre_info() function, which is neverthe-
1627         less retained for backwards compability (and is documented below).         less retained for backwards compability (and is documented below).
1628    
1629         The  first  argument  for  pcre_fullinfo() is a pointer to the compiled         The first argument for pcre_fullinfo() is a  pointer  to  the  compiled
1630         pattern. The second argument is the result of pcre_study(), or NULL  if         pattern.  The second argument is the result of pcre_study(), or NULL if
1631         the  pattern  was not studied. The third argument specifies which piece         the pattern was not studied. The third argument specifies  which  piece
1632         of information is required, and the fourth argument is a pointer  to  a         of  information  is required, and the fourth argument is a pointer to a
1633         variable  to  receive  the  data. The yield of the function is zero for         variable to receive the data. The yield of the  function  is  zero  for
1634         success, or one of the following negative numbers:         success, or one of the following negative numbers:
1635    
1636           PCRE_ERROR_NULL       the argument code was NULL           PCRE_ERROR_NULL       the argument code was NULL
# Line 1577  INFORMATION ABOUT A PATTERN Line 1638  INFORMATION ABOUT A PATTERN
1638           PCRE_ERROR_BADMAGIC   the "magic number" was not found           PCRE_ERROR_BADMAGIC   the "magic number" was not found
1639           PCRE_ERROR_BADOPTION  the value of what was invalid           PCRE_ERROR_BADOPTION  the value of what was invalid
1640    
1641         The "magic number" is placed at the start of each compiled  pattern  as         The  "magic  number" is placed at the start of each compiled pattern as
1642         an  simple check against passing an arbitrary memory pointer. Here is a         an simple check against passing an arbitrary memory pointer. Here is  a
1643         typical call of pcre_fullinfo(), to obtain the length of  the  compiled         typical  call  of pcre_fullinfo(), to obtain the length of the compiled
1644         pattern:         pattern:
1645    
1646           int rc;           int rc;
1647           size_t length;           size_t length;
1648           rc = pcre_fullinfo(           rc = pcre_fullinfo(
1649             re,               /* result of pcre_compile() */             re,               /* result of pcre_compile() */
1650             pe,               /* result of pcre_study(), or NULL */             sd,               /* result of pcre_study(), or NULL */
1651             PCRE_INFO_SIZE,   /* what is required */             PCRE_INFO_SIZE,   /* what is required */
1652             &length);         /* where to put the data */             &length);         /* where to put the data */
1653    
1654         The  possible  values for the third argument are defined in pcre.h, and         The possible values for the third argument are defined in  pcre.h,  and
1655         are as follows:         are as follows:
1656    
1657           PCRE_INFO_BACKREFMAX           PCRE_INFO_BACKREFMAX
1658    
1659         Return the number of the highest back reference  in  the  pattern.  The         Return  the  number  of  the highest back reference in the pattern. The
1660         fourth  argument  should  point to an int variable. Zero is returned if         fourth argument should point to an int variable. Zero  is  returned  if
1661         there are no back references.         there are no back references.
1662    
1663           PCRE_INFO_CAPTURECOUNT           PCRE_INFO_CAPTURECOUNT
1664    
1665         Return the number of capturing subpatterns in the pattern.  The  fourth         Return  the  number of capturing subpatterns in the pattern. The fourth
1666         argument should point to an int variable.         argument should point to an int variable.
1667    
1668           PCRE_INFO_DEFAULT_TABLES           PCRE_INFO_DEFAULT_TABLES
1669    
1670         Return  a pointer to the internal default character tables within PCRE.         Return a pointer to the internal default character tables within  PCRE.
1671         The fourth argument should point to an unsigned char *  variable.  This         The  fourth  argument should point to an unsigned char * variable. This
1672         information call is provided for internal use by the pcre_study() func-         information call is provided for internal use by the pcre_study() func-
1673         tion. External callers can cause PCRE to use  its  internal  tables  by         tion.  External  callers  can  cause PCRE to use its internal tables by
1674         passing a NULL table pointer.         passing a NULL table pointer.
1675    
1676           PCRE_INFO_FIRSTBYTE           PCRE_INFO_FIRSTBYTE
1677    
1678         Return  information  about  the first byte of any matched string, for a         Return information about the first byte of any matched  string,  for  a
1679         non-anchored pattern. The fourth argument should point to an int  vari-         non-anchored  pattern. The fourth argument should point to an int vari-
1680         able.  (This option used to be called PCRE_INFO_FIRSTCHAR; the old name         able. (This option used to be called PCRE_INFO_FIRSTCHAR; the old  name
1681         is still recognized for backwards compatibility.)         is still recognized for backwards compatibility.)
1682    
1683         If there is a fixed first byte, for example, from  a  pattern  such  as         If  there  is  a  fixed first byte, for example, from a pattern such as
1684         (cat|cow|coyote), its value is returned. Otherwise, if either         (cat|cow|coyote), its value is returned. Otherwise, if either
1685    
1686         (a)  the pattern was compiled with the PCRE_MULTILINE option, and every         (a) the pattern was compiled with the PCRE_MULTILINE option, and  every
1687         branch starts with "^", or         branch starts with "^", or
1688    
1689         (b) every branch of the pattern starts with ".*" and PCRE_DOTALL is not         (b) every branch of the pattern starts with ".*" and PCRE_DOTALL is not
1690         set (if it were set, the pattern would be anchored),         set (if it were set, the pattern would be anchored),
1691    
1692         -1  is  returned, indicating that the pattern matches only at the start         -1 is returned, indicating that the pattern matches only at  the  start
1693         of a subject string or after any newline within the  string.  Otherwise         of  a  subject string or after any newline within the string. Otherwise
1694         -2 is returned. For anchored patterns, -2 is returned.         -2 is returned. For anchored patterns, -2 is returned.
1695    
1696           PCRE_INFO_FIRSTTABLE           PCRE_INFO_FIRSTTABLE
1697    
1698         If  the pattern was studied, and this resulted in the construction of a         If the pattern was studied, and this resulted in the construction of  a
1699         256-bit table indicating a fixed set of bytes for the first byte in any         256-bit table indicating a fixed set of bytes for the first byte in any
1700         matching  string, a pointer to the table is returned. Otherwise NULL is         matching string, a pointer to the table is returned. Otherwise NULL  is
1701         returned. The fourth argument should point to an unsigned char *  vari-         returned.  The fourth argument should point to an unsigned char * vari-
1702         able.         able.
1703    
1704           PCRE_INFO_HASCRORLF           PCRE_INFO_HASCRORLF
1705    
1706         Return  1  if  the  pattern  contains any explicit matches for CR or LF         Return 1 if the pattern contains any explicit  matches  for  CR  or  LF
1707         characters, otherwise 0. The fourth argument should  point  to  an  int         characters,  otherwise  0.  The  fourth argument should point to an int
1708         variable.  An explicit match is either a literal CR or LF character, or         variable. An explicit match is either a literal CR or LF character,  or
1709         \r or \n.         \r or \n.
1710    
1711           PCRE_INFO_JCHANGED           PCRE_INFO_JCHANGED
1712    
1713         Return 1 if the (?J) or (?-J) option setting is used  in  the  pattern,         Return  1  if  the (?J) or (?-J) option setting is used in the pattern,
1714         otherwise  0. The fourth argument should point to an int variable. (?J)         otherwise 0. The fourth argument should point to an int variable.  (?J)
1715         and (?-J) set and unset the local PCRE_DUPNAMES option, respectively.         and (?-J) set and unset the local PCRE_DUPNAMES option, respectively.
1716    
1717             PCRE_INFO_JIT
1718    
1719           Return  1  if  the  pattern was studied with the PCRE_STUDY_JIT_COMPILE
1720           option, and just-in-time compiling was successful. The fourth  argument
1721           should  point  to  an  int variable. A return value of 0 means that JIT
1722           support is not available in this version of PCRE, or that  the  pattern
1723           was not studied with the PCRE_STUDY_JIT_COMPILE option, or that the JIT
1724           compiler could not handle this particular pattern. See the pcrejit doc-
1725           umentation for details of what can and cannot be handled.
1726    
1727             PCRE_INFO_JITSIZE
1728    
1729           If the pattern was successfully studied with the PCRE_STUDY_JIT_COMPILE
1730           option, return the size of the  JIT  compiled  code,  otherwise  return
1731           zero. The fourth argument should point to a size_t variable.
1732    
1733           PCRE_INFO_LASTLITERAL           PCRE_INFO_LASTLITERAL
1734    
1735         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
1736         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
1737         recorded. The fourth argument should point to an int variable. If there         recorded. The fourth argument should point to an int variable. If there
1738         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
1739         byte is recorded only if it follows something of variable  length.  For         byte  is  recorded only if it follows something of variable length. For
1740         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
1741         /^a\dz\d/ the returned value is -1.         /^a\dz\d/ the returned value is -1.
1742    
1743             PCRE_INFO_MINLENGTH
1744    
1745           If  the  pattern  was studied and a minimum length for matching subject
1746           strings was computed, its value is  returned.  Otherwise  the  returned
1747           value  is  -1. The value is a number of characters, not bytes (this may
1748           be relevant in UTF-8 mode). The fourth argument should point to an  int
1749           variable.  A  non-negative  value is a lower bound to the length of any
1750           matching string. There may not be any strings of that  length  that  do
1751           actually match, but every string that does match is at least that long.
1752    
1753           PCRE_INFO_NAMECOUNT           PCRE_INFO_NAMECOUNT
1754           PCRE_INFO_NAMEENTRYSIZE           PCRE_INFO_NAMEENTRYSIZE
1755           PCRE_INFO_NAMETABLE           PCRE_INFO_NAMETABLE
1756    
1757         PCRE supports the use of named as well as numbered capturing  parenthe-         PCRE  supports the use of named as well as numbered capturing parenthe-
1758         ses.  The names are just an additional way of identifying the parenthe-         ses. The names are just an additional way of identifying the  parenthe-
1759         ses, which still acquire numbers. Several convenience functions such as         ses, which still acquire numbers. Several convenience functions such as
1760         pcre_get_named_substring()  are  provided  for extracting captured sub-         pcre_get_named_substring() are provided for  extracting  captured  sub-
1761         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
1762         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
1763         pointers in the output vector (described with pcre_exec() below). To do         pointers in the output vector (described with pcre_exec() below). To do
1764         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
1765         described by these three values.         described by these three values.
1766    
1767         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
1768         gives the number of entries, and PCRE_INFO_NAMEENTRYSIZE gives the size         gives the number of entries, and PCRE_INFO_NAMEENTRYSIZE gives the size
1769         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
1770         depends  on the length of the longest name. PCRE_INFO_NAMETABLE returns         depends on the length of the longest name. PCRE_INFO_NAMETABLE  returns
1771         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
1772         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-
1773         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-
1774         sponding  name,  zero  terminated. The names are in alphabetical order.         sponding name, zero terminated.
1775         When PCRE_DUPNAMES is set, duplicate names are in order of their paren-  
1776         theses  numbers.  For  example,  consider the following pattern (assume         The names are in alphabetical order. Duplicate names may appear if  (?|
1777         PCRE_EXTENDED is  set,  so  white  space  -  including  newlines  -  is         is used to create multiple groups with the same number, as described in
1778         ignored):         the section on duplicate subpattern numbers in  the  pcrepattern  page.
1779           Duplicate  names  for  subpatterns with different numbers are permitted
1780           only if PCRE_DUPNAMES is set. In all cases  of  duplicate  names,  they
1781           appear  in  the table in the order in which they were found in the pat-
1782           tern. In the absence of (?| this is the  order  of  increasing  number;
1783           when (?| is used this is not necessarily the case because later subpat-
1784           terns may have lower numbers.
1785    
1786           As a simple example of the name/number table,  consider  the  following
1787           pattern  (assume  PCRE_EXTENDED is set, so white space - including new-
1788           lines - is ignored):
1789    
1790           (?<date> (?<year>(\d\d)?\d\d) -           (?<date> (?<year>(\d\d)?\d\d) -
1791           (?<month>\d\d) - (?<day>\d\d) )           (?<month>\d\d) - (?<day>\d\d) )
1792    
1793         There  are  four  named subpatterns, so the table has four entries, and         There are four named subpatterns, so the table has  four  entries,  and
1794         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,
1795         with non-printing bytes shows in hexadecimal, and undefined bytes shown         with non-printing bytes shows in hexadecimal, and undefined bytes shown
1796         as ??:         as ??:
1797    
# Line 1703  INFORMATION ABOUT A PATTERN Line 1800  INFORMATION ABOUT A PATTERN
1800           00 04 m  o  n  t  h  00           00 04 m  o  n  t  h  00
1801           00 02 y  e  a  r  00 ??           00 02 y  e  a  r  00 ??
1802    
1803         When writing code to extract data  from  named  subpatterns  using  the         When  writing  code  to  extract  data from named subpatterns using the
1804         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
1805         to be different for each compiled pattern.         to be different for each compiled pattern.
1806    
1807           PCRE_INFO_OKPARTIAL           PCRE_INFO_OKPARTIAL
1808    
1809         Return 1 if the pattern can be used for partial matching, otherwise  0.         Return  1  if  the  pattern  can  be  used  for  partial  matching with
1810         The  fourth  argument  should point to an int variable. The pcrepartial         pcre_exec(), otherwise 0. The fourth argument should point  to  an  int
1811         documentation lists the restrictions that apply to patterns  when  par-         variable.  From  release  8.00,  this  always  returns  1,  because the
1812         tial matching is used.         restrictions that previously applied  to  partial  matching  have  been
1813           lifted.  The  pcrepartial documentation gives details of partial match-
1814           ing.
1815    
1816           PCRE_INFO_OPTIONS           PCRE_INFO_OPTIONS
1817    
1818         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
1819         fourth argument should point to an unsigned long  int  variable.  These         fourth  argument  should  point to an unsigned long int variable. These
1820         option bits are those specified in the call to pcre_compile(), modified         option bits are those specified in the call to pcre_compile(), modified
1821         by any top-level option settings at the start of the pattern itself. In         by any top-level option settings at the start of the pattern itself. In
1822         other  words,  they are the options that will be in force when matching         other words, they are the options that will be in force  when  matching
1823         starts. For example, if the pattern /(?im)abc(?-i)d/ is  compiled  with         starts.  For  example, if the pattern /(?im)abc(?-i)d/ is compiled with
1824         the  PCRE_EXTENDED option, the result is PCRE_CASELESS, PCRE_MULTILINE,         the PCRE_EXTENDED option, the result is PCRE_CASELESS,  PCRE_MULTILINE,
1825         and PCRE_EXTENDED.         and PCRE_EXTENDED.
1826    
1827         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
1828         alternatives begin with one of the following:         alternatives begin with one of the following:
1829    
1830           ^     unless PCRE_MULTILINE is set           ^     unless PCRE_MULTILINE is set
# Line 1739  INFORMATION ABOUT A PATTERN Line 1838  INFORMATION ABOUT A PATTERN
1838    
1839           PCRE_INFO_SIZE           PCRE_INFO_SIZE
1840    
1841         Return the size of the compiled pattern, that is, the  value  that  was         Return  the  size  of  the compiled pattern. The fourth argument should
1842         passed as the argument to pcre_malloc() when PCRE was getting memory in         point to a size_t variable. This value does not include the size of the
1843         which to place the compiled data. The fourth argument should point to a         pcre  structure  that  is returned by pcre_compile(). The value that is
1844         size_t variable.         passed as the argument to pcre_malloc() when pcre_compile() is  getting
1845           memory  in  which  to  place the compiled data is the value returned by
1846           this option plus the size of the pcre structure.  Studying  a  compiled
1847           pattern, with or without JIT, does not alter the value returned by this
1848           option.
1849    
1850           PCRE_INFO_STUDYSIZE           PCRE_INFO_STUDYSIZE
1851    
1852         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
1853         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,
1854         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-
1855         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-
1856         variable.         tion that will speed up matching (see the section entitled "Studying  a
1857           pattern" above). The format of the study_data block is private, but its
1858           length is made available via this option so that it can  be  saved  and
1859           restored (see the pcreprecompile documentation for details).
1860    
1861    
1862  OBSOLETE INFO FUNCTION  OBSOLETE INFO FUNCTION
# Line 1803  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 1909  MATCHING A PATTERN: THE TRADITIONAL FUNC
1909              const char *subject, int length, int startoffset,              const char *subject, int length, int startoffset,
1910              int options, int *ovector, int ovecsize);              int options, int *ovector, int ovecsize);
1911    
1912         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
1913         compiled pattern, which is passed in the code argument. If the  pattern         compiled  pattern, which is passed in the code argument. If the pattern
1914         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
1915         argument. This function is the main matching facility of  the  library,         argument.  You  can call pcre_exec() with the same code and extra argu-
1916         and it operates in a Perl-like manner. For specialist use there is also         ments as many times as you like, in order to  match  different  subject
1917         an alternative matching function, which is described below in the  sec-         strings with the same pattern.
1918         tion about the pcre_dfa_exec() function.  
1919           This  function  is  the  main  matching facility of the library, and it
1920           operates in a Perl-like manner. For specialist use  there  is  also  an
1921           alternative  matching function, which is described below in the section
1922           about the pcre_dfa_exec() function.
1923    
1924         In  most applications, the pattern will have been compiled (and option-         In most applications, the pattern will have been compiled (and  option-
1925         ally studied) in the same process that calls pcre_exec().  However,  it         ally  studied)  in the same process that calls pcre_exec(). However, it
1926         is possible to save compiled patterns and study data, and then use them         is possible to save compiled patterns and study data, and then use them
1927         later in different processes, possibly even on different hosts.  For  a         later  in  different processes, possibly even on different hosts. For a
1928         discussion about this, see the pcreprecompile documentation.         discussion about this, see the pcreprecompile documentation.
1929    
1930         Here is an example of a simple call to pcre_exec():         Here is an example of a simple call to pcre_exec():
# Line 1833  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 1943  MATCHING A PATTERN: THE TRADITIONAL FUNC
1943    
1944     Extra data for pcre_exec()     Extra data for pcre_exec()
1945    
1946         If  the  extra argument is not NULL, it must point to a pcre_extra data         If the extra argument is not NULL, it must point to a  pcre_extra  data
1947         block. The pcre_study() function returns such a block (when it  doesn't         block.  The pcre_study() function returns such a block (when it doesn't
1948         return  NULL), but you can also create one for yourself, and pass addi-         return NULL), but you can also create one for yourself, and pass  addi-
1949         tional information in it. The pcre_extra block contains  the  following         tional  information  in it. The pcre_extra block contains the following
1950         fields (not necessarily in this order):         fields (not necessarily in this order):
1951    
1952           unsigned long int flags;           unsigned long int flags;
1953           void *study_data;           void *study_data;
1954             void *executable_jit;
1955           unsigned long int match_limit;           unsigned long int match_limit;
1956           unsigned long int match_limit_recursion;           unsigned long int match_limit_recursion;
1957           void *callout_data;           void *callout_data;
1958           const unsigned char *tables;           const unsigned char *tables;
1959             unsigned char **mark;
1960    
1961         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
1962         are set. The flag bits are:         are set. The flag bits are:
1963    
1964           PCRE_EXTRA_STUDY_DATA           PCRE_EXTRA_STUDY_DATA
1965             PCRE_EXTRA_EXECUTABLE_JIT
1966           PCRE_EXTRA_MATCH_LIMIT           PCRE_EXTRA_MATCH_LIMIT
1967           PCRE_EXTRA_MATCH_LIMIT_RECURSION           PCRE_EXTRA_MATCH_LIMIT_RECURSION
1968           PCRE_EXTRA_CALLOUT_DATA           PCRE_EXTRA_CALLOUT_DATA
1969           PCRE_EXTRA_TABLES           PCRE_EXTRA_TABLES
1970             PCRE_EXTRA_MARK
1971    
1972         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 and some-
1973         the  pcre_extra  block  that is returned by pcre_study(), together with         times the executable_jit field are set in the pcre_extra block that  is
1974         the appropriate flag bit. You should not set this yourself, but you may         returned  by pcre_study(), together with the appropriate flag bits. You
1975         add  to  the  block by setting the other fields and their corresponding         should not set these yourself, but you may add to the block by  setting
1976         flag bits.         the other fields and their corresponding flag bits.
1977    
1978         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
1979         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
1980         match, but which have a very large number  of  possibilities  in  their         match,  but  which  have  a very large number of possibilities in their
1981         search  trees.  The  classic  example  is  the  use of nested unlimited         search trees. The classic example is a pattern that uses nested  unlim-
1982         repeats.         ited repeats.
1983    
1984         Internally, PCRE uses a function called match() which it calls  repeat-         Internally,  pcre_exec() uses a function called match(), which it calls
1985         edly  (sometimes  recursively). The limit set by match_limit is imposed         repeatedly (sometimes recursively). The limit  set  by  match_limit  is
1986         on the number of times this function is called during  a  match,  which         imposed  on the number of times this function is called during a match,
1987         has  the  effect  of  limiting the amount of backtracking that can take         which has the effect of limiting the amount of  backtracking  that  can
1988         place. For patterns that are not anchored, the count restarts from zero         take place. For patterns that are not anchored, the count restarts from
1989         for each position in the subject string.         zero for each position in the subject string.
1990    
1991           When pcre_exec() is called with a pattern that was successfully studied
1992           with  the  PCRE_STUDY_JIT_COMPILE  option, the way that the matching is
1993           executed is entirely different. However, there is still the possibility
1994           of  runaway  matching  that  goes  on  for a very long time, and so the
1995           match_limit value is also used in this case (but in a different way) to
1996           limit how long the matching can continue.
1997    
1998         The  default  value  for  the  limit can be set when PCRE is built; the         The  default  value  for  the  limit can be set when PCRE is built; the
1999         default default is 10 million, which handles all but the  most  extreme         default default is 10 million, which handles all but the  most  extreme
# Line 1887  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 2008  MATCHING A PATTERN: THE TRADITIONAL FUNC
2008         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-
2009         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.
2010    
2011         Limiting  the  recursion  depth  limits the amount of stack that can be         Limiting the recursion depth limits the amount of  machine  stack  that
2012         used, or, when PCRE has been compiled to use memory on the heap instead         can  be used, or, when PCRE has been compiled to use memory on the heap
2013         of the stack, the amount of heap memory that can be used.         instead of the stack, the amount of heap memory that can be used.  This
2014           limit  is not relevant, and is ignored, if the pattern was successfully
2015         The  default  value  for  match_limit_recursion can be set when PCRE is         studied with PCRE_STUDY_JIT_COMPILE.
2016         built; the default default  is  the  same  value  as  the  default  for  
2017         match_limit.  You can override the default by suppling pcre_exec() with         The default value for match_limit_recursion can be  set  when  PCRE  is
2018         a  pcre_extra  block  in  which  match_limit_recursion  is   set,   and         built;  the  default  default  is  the  same  value  as the default for
2019         PCRE_EXTRA_MATCH_LIMIT_RECURSION  is  set  in  the  flags field. If the         match_limit. You can override the default by suppling pcre_exec()  with
2020           a   pcre_extra   block  in  which  match_limit_recursion  is  set,  and
2021           PCRE_EXTRA_MATCH_LIMIT_RECURSION is set in  the  flags  field.  If  the
2022         limit is exceeded, pcre_exec() returns PCRE_ERROR_RECURSIONLIMIT.         limit is exceeded, pcre_exec() returns PCRE_ERROR_RECURSIONLIMIT.
2023    
2024         The pcre_callout field is used in conjunction with the  "callout"  fea-         The  callout_data  field is used in conjunction with the "callout" fea-
2025         ture, which is described in the pcrecallout documentation.         ture, and is described in the pcrecallout documentation.
2026    
2027         The  tables  field  is  used  to  pass  a  character  tables pointer to         The tables field  is  used  to  pass  a  character  tables  pointer  to
2028         pcre_exec(); this overrides the value that is stored with the  compiled         pcre_exec();  this overrides the value that is stored with the compiled
2029         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
2030         custom tables were supplied to pcre_compile() via  its  tableptr  argu-         custom  tables  were  supplied to pcre_compile() via its tableptr argu-
2031         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
2032         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-
2033         using  patterns  that  have been saved after compiling with an external         using patterns that have been saved after compiling  with  an  external
2034         set of tables, because the external tables  might  be  at  a  different         set  of  tables,  because  the  external tables might be at a different
2035         address  when  pcre_exec() is called. See the pcreprecompile documenta-         address when pcre_exec() is called. See the  pcreprecompile  documenta-
2036         tion for a discussion of saving compiled patterns for later use.         tion for a discussion of saving compiled patterns for later use.
2037    
2038           If  PCRE_EXTRA_MARK  is  set in the flags field, the mark field must be
2039           set to point to a char * variable. If the pattern  contains  any  back-
2040           tracking  control verbs such as (*MARK:NAME), and the execution ends up
2041           with a name to pass back, a pointer to the  name  string  (zero  termi-
2042           nated)  is  placed  in  the  variable pointed to by the mark field. The
2043           names are within the compiled pattern; if you wish  to  retain  such  a
2044           name  you must copy it before freeing the memory of a compiled pattern.
2045           If there is no name to pass back, the variable pointed to by  the  mark
2046           field  set  to NULL. For details of the backtracking control verbs, see
2047           the section entitled "Backtracking control" in the pcrepattern documen-
2048           tation.
2049    
2050     Option bits for pcre_exec()     Option bits for pcre_exec()
2051    
2052         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.
2053         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,
2054         PCRE_NOTBOL,   PCRE_NOTEOL,   PCRE_NOTEMPTY,   PCRE_NO_UTF8_CHECK   and         PCRE_NOTBOL,    PCRE_NOTEOL,    PCRE_NOTEMPTY,   PCRE_NOTEMPTY_ATSTART,
2055         PCRE_PARTIAL.         PCRE_NO_START_OPTIMIZE,  PCRE_NO_UTF8_CHECK,   PCRE_PARTIAL_SOFT,   and
2056           PCRE_PARTIAL_HARD.
2057    
2058           If the pattern was successfully studied with the PCRE_STUDY_JIT_COMPILE
2059           option,  the   only   supported   options   for   JIT   execution   are
2060           PCRE_NO_UTF8_CHECK,   PCRE_NOTBOL,   PCRE_NOTEOL,   PCRE_NOTEMPTY,  and
2061           PCRE_NOTEMPTY_ATSTART. Note in particular that partial matching is  not
2062           supported.  If an unsupported option is used, JIT execution is disabled
2063           and the normal interpretive code in pcre_exec() is run.
2064    
2065           PCRE_ANCHORED           PCRE_ANCHORED
2066    
2067         The  PCRE_ANCHORED  option  limits pcre_exec() to matching at the first         The PCRE_ANCHORED option limits pcre_exec() to matching  at  the  first
2068         matching position. If a pattern was  compiled  with  PCRE_ANCHORED,  or         matching  position.  If  a  pattern was compiled with PCRE_ANCHORED, or
2069         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
2070         unachored at matching time.         unachored at matching time.
2071    
2072           PCRE_BSR_ANYCRLF           PCRE_BSR_ANYCRLF
2073           PCRE_BSR_UNICODE           PCRE_BSR_UNICODE
2074    
2075         These options (which are mutually exclusive) control what the \R escape         These options (which are mutually exclusive) control what the \R escape
2076         sequence  matches.  The choice is either to match only CR, LF, or CRLF,         sequence matches. The choice is either to match only CR, LF,  or  CRLF,
2077         or to match any Unicode newline sequence. These  options  override  the         or  to  match  any Unicode newline sequence. These options override the
2078         choice that was made or defaulted when the pattern was compiled.         choice that was made or defaulted when the pattern was compiled.
2079    
2080           PCRE_NEWLINE_CR           PCRE_NEWLINE_CR
# Line 1940  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 2083  MATCHING A PATTERN: THE TRADITIONAL FUNC
2083           PCRE_NEWLINE_ANYCRLF           PCRE_NEWLINE_ANYCRLF
2084           PCRE_NEWLINE_ANY           PCRE_NEWLINE_ANY
2085    
2086         These  options  override  the  newline  definition  that  was chosen or         These options override  the  newline  definition  that  was  chosen  or
2087         defaulted when the pattern was compiled. For details, see the  descrip-         defaulted  when the pattern was compiled. For details, see the descrip-
2088         tion  of  pcre_compile()  above.  During  matching,  the newline choice         tion of pcre_compile()  above.  During  matching,  the  newline  choice
2089         affects the behaviour of the dot, circumflex,  and  dollar  metacharac-         affects  the  behaviour  of the dot, circumflex, and dollar metacharac-
2090         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
2091         match failure for an unanchored pattern.         match failure for an unanchored pattern.
2092    
2093         When PCRE_NEWLINE_CRLF, PCRE_NEWLINE_ANYCRLF,  or  PCRE_NEWLINE_ANY  is         When  PCRE_NEWLINE_CRLF,  PCRE_NEWLINE_ANYCRLF,  or PCRE_NEWLINE_ANY is
2094         set,  and a match attempt for an unanchored pattern fails when the cur-         set, and a match attempt for an unanchored pattern fails when the  cur-
2095         rent position is at a  CRLF  sequence,  and  the  pattern  contains  no         rent  position  is  at  a  CRLF  sequence,  and the pattern contains no
2096         explicit  matches  for  CR  or  LF  characters,  the  match position is         explicit matches for  CR  or  LF  characters,  the  match  position  is
2097         advanced by two characters instead of one, in other words, to after the         advanced by two characters instead of one, in other words, to after the
2098         CRLF.         CRLF.
2099    
2100         The above rule is a compromise that makes the most common cases work as         The above rule is a compromise that makes the most common cases work as
2101         expected. For example, if the  pattern  is  .+A  (and  the  PCRE_DOTALL         expected.  For  example,  if  the  pattern  is .+A (and the PCRE_DOTALL
2102         option is not set), it does not match the string "\r\nA" because, after         option is not set), it does not match the string "\r\nA" because, after
2103         failing at the start, it skips both the CR and the LF before  retrying.         failing  at the start, it skips both the CR and the LF before retrying.
2104         However,  the  pattern  [\r\n]A does match that string, because it con-         However, the pattern [\r\n]A does match that string,  because  it  con-
2105         tains an explicit CR or LF reference, and so advances only by one char-         tains an explicit CR or LF reference, and so advances only by one char-
2106         acter after the first failure.         acter after the first failure.
2107    
2108         An explicit match for CR of LF is either a literal appearance of one of         An explicit match for CR of LF is either a literal appearance of one of
2109         those characters, or one of the \r or  \n  escape  sequences.  Implicit         those  characters,  or  one  of the \r or \n escape sequences. Implicit
2110         matches  such  as [^X] do not count, nor does \s (which includes CR and         matches such as [^X] do not count, nor does \s (which includes  CR  and
2111         LF in the characters that it matches).         LF in the characters that it matches).
2112    
2113         Notwithstanding the above, anomalous effects may still occur when  CRLF         Notwithstanding  the above, anomalous effects may still occur when CRLF
2114         is a valid newline sequence and explicit \r or \n escapes appear in the         is a valid newline sequence and explicit \r or \n escapes appear in the
2115         pattern.         pattern.
2116    
2117           PCRE_NOTBOL           PCRE_NOTBOL
2118    
2119         This option specifies that first character of the subject string is not         This option specifies that first character of the subject string is not
2120         the  beginning  of  a  line, so the circumflex metacharacter should not         the beginning of a line, so the  circumflex  metacharacter  should  not
2121         match before it. Setting this without PCRE_MULTILINE (at compile  time)         match  before it. Setting this without PCRE_MULTILINE (at compile time)
2122         causes  circumflex  never to match. This option affects only the behav-         causes circumflex never to match. This option affects only  the  behav-
2123         iour of the circumflex metacharacter. It does not affect \A.         iour of the circumflex metacharacter. It does not affect \A.
2124    
2125           PCRE_NOTEOL           PCRE_NOTEOL
2126    
2127         This option specifies that the end of the subject string is not the end         This option specifies that the end of the subject string is not the end
2128         of  a line, so the dollar metacharacter should not match it nor (except         of a line, so the dollar metacharacter should not match it nor  (except
2129         in multiline mode) a newline immediately before it. Setting this  with-         in  multiline mode) a newline immediately before it. Setting this with-
2130         out PCRE_MULTILINE (at compile time) causes dollar never to match. This         out PCRE_MULTILINE (at compile time) causes dollar never to match. This
2131         option affects only the behaviour of the dollar metacharacter. It  does         option  affects only the behaviour of the dollar metacharacter. It does
2132         not affect \Z or \z.         not affect \Z or \z.
2133    
2134           PCRE_NOTEMPTY           PCRE_NOTEMPTY
2135    
2136         An empty string is not considered to be a valid match if this option is         An empty string is not considered to be a valid match if this option is
2137         set. If there are alternatives in the pattern, they are tried.  If  all         set.  If  there are alternatives in the pattern, they are tried. If all
2138         the  alternatives  match  the empty string, the entire match fails. For         the alternatives match the empty string, the entire  match  fails.  For
2139         example, if the pattern         example, if the pattern
2140    
2141           a?b?           a?b?
2142    
2143         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
2144         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
2145         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-
2146         rences of "a" or "b".         rences of "a" or "b".
2147    
2148         Perl has no direct equivalent of PCRE_NOTEMPTY, but it does make a spe-           PCRE_NOTEMPTY_ATSTART
2149         cial case of a pattern match of the empty  string  within  its  split()  
2150         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
2151         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
2152         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.
2153         if that fails by advancing the starting offset (see below)  and  trying  
2154         an ordinary match again. There is some code that demonstrates how to do         Perl    has    no    direct    equivalent    of    PCRE_NOTEMPTY     or
2155         this in the pcredemo.c sample program.         PCRE_NOTEMPTY_ATSTART,  but  it  does  make a special case of a pattern
2156           match of the empty string within its split() function, and  when  using
2157           the  /g  modifier.  It  is  possible  to emulate Perl's behaviour after
2158           matching a null string by first trying the match again at the same off-
2159           set  with  PCRE_NOTEMPTY_ATSTART  and  PCRE_ANCHORED,  and then if that
2160           fails, by advancing the starting offset (see below) and trying an ordi-
2161           nary  match  again. There is some code that demonstrates how to do this
2162           in the pcredemo sample program. In the most general case, you  have  to
2163           check  to  see  if the newline convention recognizes CRLF as a newline,
2164           and if so, and the current character is CR followed by LF, advance  the
2165           starting offset by two characters instead of one.
2166    
2167             PCRE_NO_START_OPTIMIZE
2168    
2169           There  are a number of optimizations that pcre_exec() uses at the start
2170           of a match, in order to speed up the process. For  example,  if  it  is
2171           known that an unanchored match must start with a specific character, it
2172           searches the subject for that character, and fails  immediately  if  it
2173           cannot  find  it,  without actually running the main matching function.
2174           This means that a special item such as (*COMMIT) at the start of a pat-
2175           tern  is  not  considered until after a suitable starting point for the
2176           match has been found. When callouts or (*MARK) items are in use,  these
2177           "start-up" optimizations can cause them to be skipped if the pattern is
2178           never actually used. The start-up optimizations are in  effect  a  pre-
2179           scan of the subject that takes place before the pattern is run.
2180    
2181           The  PCRE_NO_START_OPTIMIZE option disables the start-up optimizations,
2182           possibly causing performance to suffer,  but  ensuring  that  in  cases
2183           where  the  result is "no match", the callouts do occur, and that items
2184           such as (*COMMIT) and (*MARK) are considered at every possible starting
2185           position  in  the  subject  string. If PCRE_NO_START_OPTIMIZE is set at
2186           compile time, it cannot be unset at matching time.
2187    
2188           Setting PCRE_NO_START_OPTIMIZE can change the  outcome  of  a  matching
2189           operation.  Consider the pattern
2190    
2191             (*COMMIT)ABC
2192    
2193           When  this  is  compiled, PCRE records the fact that a match must start
2194           with the character "A". Suppose the subject  string  is  "DEFABC".  The
2195           start-up  optimization  scans along the subject, finds "A" and runs the
2196           first match attempt from there. The (*COMMIT) item means that the  pat-
2197           tern  must  match the current starting position, which in this case, it
2198           does. However, if the same match  is  run  with  PCRE_NO_START_OPTIMIZE
2199           set,  the  initial  scan  along the subject string does not happen. The
2200           first match attempt is run starting  from  "D"  and  when  this  fails,
2201           (*COMMIT)  prevents  any  further  matches  being tried, so the overall
2202           result is "no match". If the pattern is studied,  more  start-up  opti-
2203           mizations  may  be  used. For example, a minimum length for the subject
2204           may be recorded. Consider the pattern
2205    
2206             (*MARK:A)(X|Y)
2207    
2208           The minimum length for a match is one  character.  If  the  subject  is
2209           "ABC",  there  will  be  attempts  to  match "ABC", "BC", "C", and then
2210           finally an empty string.  If the pattern is studied, the final  attempt
2211           does  not take place, because PCRE knows that the subject is too short,
2212           and so the (*MARK) is never encountered.  In this  case,  studying  the
2213           pattern  does  not  affect the overall match result, which is still "no
2214           match", but it does affect the auxiliary information that is returned.
2215    
2216           PCRE_NO_UTF8_CHECK           PCRE_NO_UTF8_CHECK
2217    
# Line 2019  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 2221  MATCHING A PATTERN: THE TRADITIONAL FUNC
2221         points  to  the start of a UTF-8 character. There is a discussion about         points  to  the start of a UTF-8 character. There is a discussion about
2222         the validity of UTF-8 strings in the section on UTF-8  support  in  the         the validity of UTF-8 strings in the section on UTF-8  support  in  the
2223         main  pcre  page.  If  an  invalid  UTF-8  sequence  of bytes is found,         main  pcre  page.  If  an  invalid  UTF-8  sequence  of bytes is found,
2224         pcre_exec() returns the error PCRE_ERROR_BADUTF8. If  startoffset  con-         pcre_exec() returns  the  error  PCRE_ERROR_BADUTF8  or,  if  PCRE_PAR-
2225         tains an invalid value, PCRE_ERROR_BADUTF8_OFFSET is returned.         TIAL_HARD  is set and the problem is a truncated UTF-8 character at the
2226           end of the subject, PCRE_ERROR_SHORTUTF8. In  both  cases,  information
2227           about  the  precise  nature  of the error may also be returned (see the
2228           descriptions of these errors in the section entitled Error return  val-
2229           ues from pcre_exec() below).  If startoffset contains a value that does
2230           not point to the start of a UTF-8 character (or to the end of the  sub-
2231           ject), PCRE_ERROR_BADUTF8_OFFSET is returned.
2232    
2233         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
2234         these   checks   for   performance   reasons,   you   can    set    the         these   checks   for   performance   reasons,   you   can    set    the
# Line 2028  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 2236  MATCHING A PATTERN: THE TRADITIONAL FUNC
2236         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
2237         making  repeated  calls  to  find  all  the matches in a single subject         making  repeated  calls  to  find  all  the matches in a single subject
2238         string. However, you should be  sure  that  the  value  of  startoffset         string. However, you should be  sure  that  the  value  of  startoffset
2239         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).
2240         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
2241         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.
2242         acter, is undefined. Your program may crash.         Your program may crash.
2243    
2244           PCRE_PARTIAL           PCRE_PARTIAL_HARD
2245             PCRE_PARTIAL_SOFT
2246         This option turns on the  partial  matching  feature.  If  the  subject  
2247         string  fails to match the pattern, but at some point during the match-         These options turn on the partial matching feature. For backwards  com-
2248         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
2249         partially  matches  the  pattern and the failure to match occurred only         match occurs if the end of the subject string is reached  successfully,
2250         because there were not enough subject characters), pcre_exec()  returns         but  there  are not enough subject characters to complete the match. If
2251         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,
2252         used, there are restrictions on what may appear in the  pattern.  These         matching  continues  by  testing any remaining alternatives. Only if no
2253         are discussed in the pcrepartial documentation.         complete match can be found is PCRE_ERROR_PARTIAL returned  instead  of
2254           PCRE_ERROR_NOMATCH.  In  other  words,  PCRE_PARTIAL_SOFT says that the
2255           caller is prepared to handle a partial match, but only if  no  complete
2256           match can be found.
2257    
2258           If  PCRE_PARTIAL_HARD  is  set, it overrides PCRE_PARTIAL_SOFT. In this
2259           case, if a partial match  is  found,  pcre_exec()  immediately  returns
2260           PCRE_ERROR_PARTIAL,  without  considering  any  other  alternatives. In
2261           other words, when PCRE_PARTIAL_HARD is set, a partial match is  consid-
2262           ered to be more important that an alternative complete match.
2263    
2264           In  both  cases,  the portion of the string that was inspected when the
2265           partial match was found is set as the first matching string. There is a
2266           more  detailed  discussion  of partial and multi-segment matching, with
2267           examples, in the pcrepartial documentation.
2268    
2269     The string to be matched by pcre_exec()     The string to be matched by pcre_exec()
2270    
2271         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
2272         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.
2273         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,
2274         Unlike the pattern string, the subject may contain binary  zero  bytes.         pcre_exec()  returns  PCRE_ERROR_BADOFFSET. When the starting offset is
2275         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,
2276         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
2277           must point to the start of a UTF-8 character (or the end  of  the  sub-
2278           ject).  Unlike  the pattern string, the subject may contain binary zero
2279           bytes.
2280    
2281         A non-zero starting offset is useful when searching for  another  match         A non-zero starting offset is useful when searching for  another  match
2282         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 2072  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 2297  MATCHING A PATTERN: THE TRADITIONAL FUNC
2297         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
2298         discover that it is preceded by a letter.         discover that it is preceded by a letter.
2299    
2300         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
2301           match an empty string. It is possible to emulate Perl's /g behaviour by
2302           first   trying   the   match   again  at  the  same  offset,  with  the
2303           PCRE_NOTEMPTY_ATSTART and  PCRE_ANCHORED  options,  and  then  if  that
2304           fails,  advancing  the  starting  offset  and  trying an ordinary match
2305           again. There is some code that demonstrates how to do this in the pcre-
2306           demo sample program. In the most general case, you have to check to see
2307           if the newline convention recognizes CRLF as a newline, and if so,  and
2308           the current character is CR followed by LF, advance the starting offset
2309           by two characters instead of one.
2310    
2311           If a non-zero starting offset is passed when the pattern  is  anchored,
2312         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
2313         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
2314         subject.         subject.
2315    
2316     How pcre_exec() returns captured substrings     How pcre_exec() returns captured substrings
2317    
2318         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
2319         addition,  further  substrings  from  the  subject may be picked out by         addition, further substrings from the subject  may  be  picked  out  by
2320         parts of the pattern. Following the usage  in  Jeffrey  Friedl's  book,         parts  of  the  pattern.  Following the usage in Jeffrey Friedl's book,
2321         this  is  called "capturing" in what follows, and the phrase "capturing         this is called "capturing" in what follows, and the  phrase  "capturing
2322         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-
2323         string.  PCRE  supports several other kinds of parenthesized subpattern         string. PCRE supports several other kinds of  parenthesized  subpattern
2324         that do not cause substrings to be captured.         that do not cause substrings to be captured.
2325    
2326         Captured substrings are returned to the caller via a vector of  integer         Captured substrings are returned to the caller via a vector of integers
2327         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-
2328         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:
2329         Note: this argument is NOT the size of ovector in bytes.         this argument is NOT the size of ovector in bytes.
2330    
2331         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-
2332         strings, each substring using a pair of integers. The  remaining  third         strings,  each  substring using a pair of integers. The remaining third
2333         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-
2334         turing subpatterns, and is not available for passing back  information.         turing  subpatterns, and is not available for passing back information.
2335         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
2336         it is not, it is rounded down.         it is not, it is rounded down.
2337    
2338         When a match is successful, information about  captured  substrings  is         When  a  match  is successful, information about captured substrings is
2339         returned  in  pairs  of integers, starting at the beginning of ovector,         returned in pairs of integers, starting at the  beginning  of  ovector,
2340         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
2341         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
2342         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
2343         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
2344         tor[1], identify the portion of  the  subject  string  matched  by  the         byte offsets, even in UTF-8 mode. They are not character counts.
2345         entire  pattern.  The next pair is used for the first capturing subpat-  
2346         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
2347         highest numbered pair that has been set. For example, if two substrings         portion of the subject string matched by the entire pattern.  The  next
2348         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
2349         subpatterns,  the return value from a successful match is 1, indicating         returned by pcre_exec() is one more than the highest numbered pair that
2350         that just the first pair of offsets has been set.         has  been  set.  For example, if two substrings have been captured, the
2351           returned value is 3. If there are no capturing subpatterns, the  return
2352           value from a successful match is 1, indicating that just the first pair
2353           of offsets has been set.
2354    
2355         If a capturing subpattern is matched repeatedly, it is the last portion         If a capturing subpattern is matched repeatedly, it is the last portion
2356         of the string that it matched that is returned.         of the string that it matched that is returned.
2357    
2358         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,
2359         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
2360         function  returns a value of zero. In particular, if the substring off-         function  returns a value of zero. If neither the actual string matched
2361         sets are not of interest, pcre_exec() may be called with ovector passed         not any captured substrings are of interest, pcre_exec() may be  called
2362         as  NULL  and  ovecsize  as zero. However, if the pattern contains back         with  ovector passed as NULL and ovecsize as zero. However, if the pat-
2363         references and the ovector is not big enough to  remember  the  related         tern contains back references and the ovector  is  not  big  enough  to
2364         substrings,  PCRE has to get additional memory for use during matching.         remember  the related substrings, PCRE has to get additional memory for
2365         Thus it is usually advisable to supply an ovector.         use during matching. Thus it is usually advisable to supply an  ovector
2366           of reasonable size.
2367    
2368           There  are  some  cases where zero is returned (indicating vector over-
2369           flow) when in fact the vector is exactly the right size for  the  final
2370           match. For example, consider the pattern
2371    
2372             (a)(?:(b)c|bd)
2373    
2374           If  a  vector of 6 elements (allowing for only 1 captured substring) is
2375           given with subject string "abd", pcre_exec() will try to set the second
2376           captured string, thereby recording a vector overflow, before failing to
2377           match "c" and backing up  to  try  the  second  alternative.  The  zero
2378           return,  however,  does  correctly  indicate that the maximum number of
2379           slots (namely 2) have been filled. In similar cases where there is tem-
2380           porary  overflow,  but  the final number of used slots is actually less
2381           than the maximum, a non-zero value is returned.
2382    
2383         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
2384         subpatterns  there  are  in  a  compiled pattern. The smallest size for         subpatterns  there  are  in  a  compiled pattern. The smallest size for
2385         ovector that will allow for n captured substrings, in addition  to  the         ovector that will allow for n captured substrings, in addition  to  the
2386         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 2141  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 2396  MATCHING A PATTERN: THE TRADITIONAL FUNC
2396         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
2397         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
2398         matched.  The  return  from the function is 2, because the highest used         matched.  The  return  from the function is 2, because the highest used
2399         capturing subpattern number is 1. However, you can refer to the offsets         capturing subpattern number is 1, and the offsets for  for  the  second
2400         for  the  second  and third capturing subpatterns if you wish (assuming         and  third  capturing subpatterns (assuming the vector is large enough,
2401         the vector is large enough, of course).         of course) are set to -1.
2402    
2403           Note: Elements in the first two-thirds of ovector that  do  not  corre-
2404           spond  to  capturing parentheses in the pattern are never changed. That
2405           is, if a pattern contains n capturing parentheses, no more  than  ovec-
2406           tor[0]  to ovector[2n+1] are set by pcre_exec(). The other elements (in
2407           the first two-thirds) retain whatever values they previously had.
2408    
2409         Some convenience functions are provided  for  extracting  the  captured         Some convenience functions are provided  for  extracting  the  captured
2410         substrings as separate strings. These are described below.         substrings as separate strings. These are described below.
# Line 2188  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 2449  MATCHING A PATTERN: THE TRADITIONAL FUNC
2449         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
2450         memory is automatically freed at the end of matching.         memory is automatically freed at the end of matching.
2451    
2452           This  error  is also given if pcre_stack_malloc() fails in pcre_exec().
2453           This can happen only when PCRE has been compiled with  --disable-stack-
2454           for-recursion.
2455    
2456           PCRE_ERROR_NOSUBSTRING    (-7)           PCRE_ERROR_NOSUBSTRING    (-7)
2457    
2458         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 2209  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 2474  MATCHING A PATTERN: THE TRADITIONAL FUNC
2474           PCRE_ERROR_BADUTF8        (-10)           PCRE_ERROR_BADUTF8        (-10)
2475    
2476         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
2477         subject.         subject, and the PCRE_NO_UTF8_CHECK option was not set. If the size  of
2478           the  output  vector  (ovecsize)  is  at least 2, the byte offset to the
2479           start of the the invalid UTF-8 character is placed in  the  first  ele-
2480           ment,  and  a  reason  code is placed in the second element. The reason
2481           codes are listed in the following section.  For backward compatibility,
2482           if  PCRE_PARTIAL_HARD is set and the problem is a truncated UTF-8 char-
2483           acter  at  the  end  of  the   subject   (reason   codes   1   to   5),
2484           PCRE_ERROR_SHORTUTF8 is returned instead of PCRE_ERROR_BADUTF8.
2485    
2486           PCRE_ERROR_BADUTF8_OFFSET (-11)           PCRE_ERROR_BADUTF8_OFFSET (-11)
2487    
2488         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
2489           found to be valid (the PCRE_NO_UTF8_CHECK option was not set), but  the
2490         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-
2491         ter.         ter or the end of the subject.
2492    
2493           PCRE_ERROR_PARTIAL        (-12)           PCRE_ERROR_PARTIAL        (-12)
2494    
# Line 2224  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 2497  MATCHING A PATTERN: THE TRADITIONAL FUNC
2497    
2498           PCRE_ERROR_BADPARTIAL     (-13)           PCRE_ERROR_BADPARTIAL     (-13)
2499    
2500         The  PCRE_PARTIAL  option  was  used with a compiled pattern containing         This  code  is  no  longer  in  use.  It was formerly returned when the
2501         items that are not supported for partial matching. See the  pcrepartial         PCRE_PARTIAL option was used with a compiled pattern  containing  items
2502         documentation for details of partial matching.         that  were  not  supported  for  partial  matching.  From  release 8.00
2503           onwards, there are no restrictions on partial matching.
2504    
2505           PCRE_ERROR_INTERNAL       (-14)           PCRE_ERROR_INTERNAL       (-14)
2506    
2507         An  unexpected  internal error has occurred. This error could be caused         An unexpected internal error has occurred. This error could  be  caused
2508         by a bug in PCRE or by overwriting of the compiled pattern.         by a bug in PCRE or by overwriting of the compiled pattern.
2509    
2510           PCRE_ERROR_BADCOUNT       (-15)           PCRE_ERROR_BADCOUNT       (-15)
2511    
2512         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.
2513    
2514           PCRE_ERROR_RECURSIONLIMIT (-21)           PCRE_ERROR_RECURSIONLIMIT (-21)
2515    
# Line 2247  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 2521  MATCHING A PATTERN: THE TRADITIONAL FUNC
2521    
2522         An invalid combination of PCRE_NEWLINE_xxx options was given.         An invalid combination of PCRE_NEWLINE_xxx options was given.
2523    
2524             PCRE_ERROR_BADOFFSET      (-24)
2525    
2526           The value of startoffset was negative or greater than the length of the
2527           subject, that is, the value in length.
2528    
2529             PCRE_ERROR_SHORTUTF8      (-25)
2530    
2531           This error is returned instead of PCRE_ERROR_BADUTF8 when  the  subject
2532           string  ends with a truncated UTF-8 character and the PCRE_PARTIAL_HARD
2533           option is set.  Information  about  the  failure  is  returned  as  for
2534           PCRE_ERROR_BADUTF8.  It  is in fact sufficient to detect this case, but
2535           this special error code for PCRE_PARTIAL_HARD precedes the  implementa-
2536           tion  of returned information; it is retained for backwards compatibil-
2537           ity.
2538    
2539             PCRE_ERROR_RECURSELOOP    (-26)
2540    
2541           This error is returned when pcre_exec() detects a recursion loop within
2542           the  pattern. Specifically, it means that either the whole pattern or a
2543           subpattern has been called recursively for the second time at the  same
2544           position in the subject string. Some simple patterns that might do this
2545           are detected and faulted at compile time, but more  complicated  cases,
2546           in particular mutual recursions between two different subpatterns, can-
2547           not be detected until run time.
2548    
2549             PCRE_ERROR_JIT_STACKLIMIT (-27)
2550    
2551           This error is returned when a pattern  that  was  successfully  studied
2552           using  the PCRE_STUDY_JIT_COMPILE option is being matched, but the mem-
2553           ory available for  the  just-in-time  processing  stack  is  not  large
2554           enough. See the pcrejit documentation for more details.
2555    
2556         Error numbers -16 to -20 and -22 are not used by pcre_exec().         Error numbers -16 to -20 and -22 are not used by pcre_exec().
2557    
2558       Reason codes for invalid UTF-8 strings
2559    
2560           When pcre_exec() returns either PCRE_ERROR_BADUTF8 or PCRE_ERROR_SHORT-
2561           UTF8, and the size of the output vector (ovecsize) is at least  2,  the
2562           offset  of  the  start  of the invalid UTF-8 character is placed in the
2563           first output vector element (ovector[0]) and a reason code is placed in
2564           the  second  element  (ovector[1]). The reason codes are given names in
2565           the pcre.h header file:
2566    
2567             PCRE_UTF8_ERR1
2568             PCRE_UTF8_ERR2
2569             PCRE_UTF8_ERR3
2570             PCRE_UTF8_ERR4
2571             PCRE_UTF8_ERR5
2572    
2573           The string ends with a truncated UTF-8 character;  the  code  specifies
2574           how  many bytes are missing (1 to 5). Although RFC 3629 restricts UTF-8
2575           characters to be no longer than 4 bytes, the  encoding  scheme  (origi-
2576           nally  defined  by  RFC  2279)  allows  for  up to 6 bytes, and this is
2577           checked first; hence the possibility of 4 or 5 missing bytes.
2578    
2579             PCRE_UTF8_ERR6
2580             PCRE_UTF8_ERR7
2581             PCRE_UTF8_ERR8
2582             PCRE_UTF8_ERR9
2583             PCRE_UTF8_ERR10
2584    
2585           The two most significant bits of the 2nd, 3rd, 4th, 5th, or 6th byte of
2586           the  character  do  not have the binary value 0b10 (that is, either the
2587           most significant bit is 0, or the next bit is 1).
2588    
2589             PCRE_UTF8_ERR11
2590             PCRE_UTF8_ERR12
2591    
2592           A character that is valid by the RFC 2279 rules is either 5 or 6  bytes
2593           long; these code points are excluded by RFC 3629.
2594    
2595             PCRE_UTF8_ERR13
2596    
2597           A  4-byte character has a value greater than 0x10fff; these code points
2598           are excluded by RFC 3629.
2599    
2600             PCRE_UTF8_ERR14
2601    
2602           A 3-byte character has a value in the  range  0xd800  to  0xdfff;  this
2603           range  of code points are reserved by RFC 3629 for use with UTF-16, and
2604           so are excluded from UTF-8.
2605    
2606             PCRE_UTF8_ERR15
2607             PCRE_UTF8_ERR16
2608             PCRE_UTF8_ERR17
2609             PCRE_UTF8_ERR18
2610             PCRE_UTF8_ERR19
2611    
2612           A 2-, 3-, 4-, 5-, or 6-byte character is "overlong", that is, it  codes
2613           for  a  value that can be represented by fewer bytes, which is invalid.
2614           For example, the two bytes 0xc0, 0xae give the value 0x2e,  whose  cor-
2615           rect coding uses just one byte.
2616    
2617             PCRE_UTF8_ERR20
2618    
2619           The two most significant bits of the first byte of a character have the
2620           binary value 0b10 (that is, the most significant bit is 1 and the  sec-
2621           ond  is  0). Such a byte can only validly occur as the second or subse-
2622           quent byte of a multi-byte character.
2623    
2624             PCRE_UTF8_ERR21
2625    
2626           The first byte of a character has the value 0xfe or 0xff. These  values
2627           can never occur in a valid UTF-8 string.
2628    
2629    
2630  EXTRACTING CAPTURED SUBSTRINGS BY NUMBER  EXTRACTING CAPTURED SUBSTRINGS BY NUMBER
2631    
# Line 2385  EXTRACTING CAPTURED SUBSTRINGS BY NAME Line 2762  EXTRACTING CAPTURED SUBSTRINGS BY NAME
2762         ate. NOTE: If PCRE_DUPNAMES is set and there are duplicate  names,  the         ate. NOTE: If PCRE_DUPNAMES is set and there are duplicate  names,  the
2763         behaviour may not be what you want (see the next section).         behaviour may not be what you want (see the next section).
2764    
2765           Warning: If the pattern uses the (?| feature to set up multiple subpat-
2766           terns with the same number, as described in the  section  on  duplicate
2767           subpattern  numbers  in  the  pcrepattern page, you cannot use names to
2768           distinguish the different subpatterns, because names are  not  included
2769           in  the compiled code. The matching process uses only numbers. For this
2770           reason, the use of different names for subpatterns of the  same  number
2771           causes an error at compile time.
2772    
2773    
2774  DUPLICATE SUBPATTERN NAMES  DUPLICATE SUBPATTERN NAMES
2775    
# Line 2392  DUPLICATE SUBPATTERN NAMES Line 2777  DUPLICATE SUBPATTERN NAMES
2777              const char *name, char **first, char **last);              const char *name, char **first, char **last);
2778    
2779         When  a  pattern  is  compiled with the PCRE_DUPNAMES option, names for         When  a  pattern  is  compiled with the PCRE_DUPNAMES option, names for
2780         subpatterns are not required to  be  unique.  Normally,  patterns  with         subpatterns are not required to be unique. (Duplicate names are  always
2781         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 (?|
2782         subpatterns participates. An example is shown in the pcrepattern  docu-         feature. Indeed, if such subpatterns are named, they  are  required  to
2783         mentation.         use the same names.)
2784    
2785           Normally, patterns with duplicate names are such that in any one match,
2786           only one of the named subpatterns participates. An example is shown  in
2787           the pcrepattern documentation.
2788    
2789         When    duplicates   are   present,   pcre_copy_named_substring()   and         When    duplicates   are   present,   pcre_copy_named_substring()   and
2790         pcre_get_named_substring() return the first substring corresponding  to         pcre_get_named_substring() return the first substring corresponding  to
# Line 2412  DUPLICATE SUBPATTERN NAMES Line 2801  DUPLICATE SUBPATTERN NAMES
2801         the  name-to-number  table  for  the  given  name.  The function itself         the  name-to-number  table  for  the  given  name.  The function itself
2802         returns the length of each entry,  or  PCRE_ERROR_NOSUBSTRING  (-7)  if         returns the length of each entry,  or  PCRE_ERROR_NOSUBSTRING  (-7)  if
2803         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-
2804         tion entitled Information about a  pattern.   Given  all  the  relevant         tion entitled Information about a pattern above.  Given all  the  rele-
2805         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
2806         the captured data, if any.         hence the captured data, if any.
2807    
2808    
2809  FINDING ALL POSSIBLE MATCHES  FINDING ALL POSSIBLE MATCHES
# Line 2448  MATCHING A PATTERN: THE ALTERNATIVE FUNC Line 2837  MATCHING A PATTERN: THE ALTERNATIVE FUNC
2837         characteristics to the normal algorithm, and  is  not  compatible  with         characteristics to the normal algorithm, and  is  not  compatible  with
2838         Perl.  Some  of the features of PCRE patterns are not supported. Never-         Perl.  Some  of the features of PCRE patterns are not supported. Never-
2839         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
2840         a discussion of the two matching algorithms, see the pcrematching docu-         a  discussion  of  the  two matching algorithms, and a list of features
2841         mentation.         that pcre_dfa_exec() does not support, see the pcrematching  documenta-
2842           tion.
2843    
2844         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
2845         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-
2846         ent way, and this is described below. The other  common  arguments  are         ent  way,  and  this is described below. The other common arguments are
2847         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
2848         repeated here.         repeated here.
2849    
2850         The two additional arguments provide workspace for  the  function.  The         The  two  additional  arguments provide workspace for the function. The
2851         workspace  vector  should  contain at least 20 elements. It is used for         workspace vector should contain at least 20 elements. It  is  used  for
2852         keeping  track  of  multiple  paths  through  the  pattern  tree.  More         keeping  track  of  multiple  paths  through  the  pattern  tree.  More
2853         workspace  will  be  needed for patterns and subjects where there are a         workspace will be needed for patterns and subjects where  there  are  a
2854         lot of potential matches.         lot of potential matches.
2855    
2856         Here is an example of a simple call to pcre_dfa_exec():         Here is an example of a simple call to pcre_dfa_exec():
# Line 2482  MATCHING A PATTERN: THE ALTERNATIVE FUNC Line 2872  MATCHING A PATTERN: THE ALTERNATIVE FUNC
2872    
2873     Option bits for pcre_dfa_exec()     Option bits for pcre_dfa_exec()
2874    
2875         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
2876         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-
2877         LINE_xxx, PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY,  PCRE_NO_UTF8_CHECK,         LINE_xxx,        PCRE_NOTBOL,        PCRE_NOTEOL,        PCRE_NOTEMPTY,
2878         PCRE_PARTIAL, PCRE_DFA_SHORTEST, and PCRE_DFA_RESTART. All but the last         PCRE_NOTEMPTY_ATSTART,      PCRE_NO_UTF8_CHECK,       PCRE_BSR_ANYCRLF,
2879         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-
2880         not repeated here.         TIAL_SOFT, PCRE_DFA_SHORTEST, and PCRE_DFA_RESTART.  All but  the  last
2881           four  of  these  are  exactly  the  same  as  for pcre_exec(), so their
2882           PCRE_PARTIAL         description is not repeated here.
2883    
2884         This  has  the  same general effect as it does for pcre_exec(), but the           PCRE_PARTIAL_HARD
2885         details  are  slightly  different.  When  PCRE_PARTIAL   is   set   for           PCRE_PARTIAL_SOFT
2886         pcre_dfa_exec(),  the  return code PCRE_ERROR_NOMATCH is converted into  
2887         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
2888         been no complete matches, but there is still at least one matching pos-         details  are  slightly  different.  When  PCRE_PARTIAL_HARD  is set for
2889         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-
2890         set as the first matching string.         ject  is  reached  and there is still at least one matching possibility
2891           that requires additional characters. This happens even if some complete
2892           matches have also been found. When PCRE_PARTIAL_SOFT is set, the return
2893           code PCRE_ERROR_NOMATCH is converted into PCRE_ERROR_PARTIAL if the end
2894           of  the  subject  is  reached, there have been no complete matches, but
2895           there is still at least one matching possibility. The  portion  of  the
2896           string  that  was inspected when the longest partial match was found is
2897           set as the first matching string  in  both  cases.   There  is  a  more
2898           detailed  discussion  of partial and multi-segment matching, with exam-
2899           ples, in the pcrepartial documentation.
2900    
2901           PCRE_DFA_SHORTEST           PCRE_DFA_SHORTEST
2902    
2903         Setting  the  PCRE_DFA_SHORTEST option causes the matching algorithm to         Setting the PCRE_DFA_SHORTEST option causes the matching  algorithm  to
2904         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-
2905         tive  algorithm  works, this is necessarily the shortest possible match         tive algorithm works, this is necessarily the shortest  possible  match
2906         at the first possible matching point in the subject string.         at the first possible matching point in the subject string.
2907    
2908           PCRE_DFA_RESTART           PCRE_DFA_RESTART
2909    
2910         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
2911         returns  a  partial  match, it is possible to call it again, with addi-         again, with additional subject characters, and have  it  continue  with
2912         tional subject characters, and have it continue with  the  same  match.         the  same match. The PCRE_DFA_RESTART option requests this action; when
2913         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
2914         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
2915         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
2916         match. There is more discussion of this  facility  in  the  pcrepartial         pcrepartial documentation.
        documentation.  
2917    
2918     Successful returns from pcre_dfa_exec()     Successful returns from pcre_dfa_exec()
2919    
# Line 2549  MATCHING A PATTERN: THE ALTERNATIVE FUNC Line 2947  MATCHING A PATTERN: THE ALTERNATIVE FUNC
2947         The strings are returned in reverse order of length; that is, the long-         The strings are returned in reverse order of length; that is, the long-
2948         est  matching  string is given first. If there were too many matches to         est  matching  string is given first. If there were too many matches to
2949         fit into ovector, the yield of the function is zero, and the vector  is         fit into ovector, the yield of the function is zero, and the vector  is
2950         filled with the longest matches.         filled  with  the  longest matches. Unlike pcre_exec(), pcre_dfa_exec()
2951           can use the entire ovector for returning matched strings.
2952    
2953     Error returns from pcre_dfa_exec()     Error returns from pcre_dfa_exec()
2954    
2955         The  pcre_dfa_exec()  function returns a negative number when it fails.         The pcre_dfa_exec() function returns a negative number when  it  fails.
2956         Many of the errors are the same  as  for  pcre_exec(),  and  these  are         Many  of  the  errors  are  the  same as for pcre_exec(), and these are
2957         described  above.   There are in addition the following errors that are         described above.  There are in addition the following errors  that  are
2958         specific to pcre_dfa_exec():         specific to pcre_dfa_exec():
2959    
2960           PCRE_ERROR_DFA_UITEM      (-16)           PCRE_ERROR_DFA_UITEM      (-16)
2961    
2962         This return is given if pcre_dfa_exec() encounters an item in the  pat-         This  return is given if pcre_dfa_exec() encounters an item in the pat-
2963         tern  that  it  does not support, for instance, the use of \C or a back         tern that it does not support, for instance, the use of \C  or  a  back
2964         reference.         reference.
2965    
2966           PCRE_ERROR_DFA_UCOND      (-17)           PCRE_ERROR_DFA_UCOND      (-17)
2967    
2968         This return is given if pcre_dfa_exec()  encounters  a  condition  item         This  return  is  given  if pcre_dfa_exec() encounters a condition item
2969         that  uses  a back reference for the condition, or a test for recursion         that uses a back reference for the condition, or a test  for  recursion
2970         in a specific group. These are not supported.         in a specific group. These are not supported.
2971    
2972           PCRE_ERROR_DFA_UMLIMIT    (-18)           PCRE_ERROR_DFA_UMLIMIT    (-18)
2973    
2974         This return is given if pcre_dfa_exec() is called with an  extra  block         This  return  is given if pcre_dfa_exec() is called with an extra block
2975         that contains a setting of the match_limit field. This is not supported         that contains a setting of  the  match_limit  or  match_limit_recursion
2976         (it is meaningless).         fields.  This  is  not  supported (these fields are meaningless for DFA
2977           matching).
2978    
2979           PCRE_ERROR_DFA_WSSIZE     (-19)           PCRE_ERROR_DFA_WSSIZE     (-19)
2980    
# Line 2592  MATCHING A PATTERN: THE ALTERNATIVE FUNC Line 2992  MATCHING A PATTERN: THE ALTERNATIVE FUNC
2992  SEE ALSO  SEE ALSO
2993    
2994         pcrebuild(3), pcrecallout(3), pcrecpp(3)(3), pcrematching(3),  pcrepar-         pcrebuild(3), pcrecallout(3), pcrecpp(3)(3), pcrematching(3),  pcrepar-
2995         tial(3),  pcreposix(3), pcreprecompile(3), pcresample(3), pcrestack(3).         tial(3), pcreposix(3), pcreprecompile(3), pcresample(3), pcrestack(3).
2996    
2997    
2998  AUTHOR  AUTHOR
# Line 2604  AUTHOR Line 3004  AUTHOR
3004    
3005  REVISION  REVISION
3006    
3007         Last updated: 12 April 2008         Last updated: 02 December 2011
3008         Copyright (c) 1997-2008 University of Cambridge.         Copyright (c) 1997-2011 University of Cambridge.
3009  ------------------------------------------------------------------------------  ------------------------------------------------------------------------------
3010    
3011    
# Line 2634  PCRE CALLOUTS Line 3034  PCRE CALLOUTS
3034    
3035           (?C1)abc(?C2)def           (?C1)abc(?C2)def
3036    
3037         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
3038         called, PCRE automatically  inserts  callouts,  all  with  number  255,         pcre_compile2() is called, PCRE  automatically  inserts  callouts,  all
3039         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
3040         used with the pattern         PCRE_AUTO_CALLOUT is used with the pattern
3041    
3042           A(\d{2}|--)           A(\d{2}|--)
3043    
# Line 2652  PCRE CALLOUTS Line 3052  PCRE CALLOUTS
3052         pattern is matched. This is useful information when you are  trying  to         pattern is matched. This is useful information when you are  trying  to
3053         optimize the performance of a particular pattern.         optimize the performance of a particular pattern.
3054    
3055           The  use  of callouts in a pattern makes it ineligible for optimization
3056           by  the  just-in-time  compiler.  Studying  such  a  pattern  with  the
3057           PCRE_STUDY_JIT_COMPILE option always fails.
3058    
3059    
3060  MISSING CALLOUTS  MISSING CALLOUTS
3061    
3062         You  should  be  aware  that,  because of optimizations in the way PCRE         You  should  be  aware  that,  because of optimizations in the way PCRE
3063         matches patterns, callouts sometimes do not happen. For example, if the         matches patterns by default, callouts  sometimes  do  not  happen.  For
3064         pattern is         example, if the pattern is
3065    
3066           ab(?C4)cd           ab(?C4)cd
3067    
# Line 2666  MISSING CALLOUTS Line 3070  MISSING CALLOUTS
3070         ever  start,  and  the  callout is never reached. However, with "abyd",         ever  start,  and  the  callout is never reached. However, with "abyd",
3071         though the result is still no match, the callout is obeyed.         though the result is still no match, the callout is obeyed.
3072    
3073           If the pattern is studied, PCRE knows the minimum length of a  matching
3074           string,  and will immediately give a "no match" return without actually
3075           running a match if the subject is not long enough, or,  for  unanchored
3076           patterns, if it has been scanned far enough.
3077    
3078           You  can disable these optimizations by passing the PCRE_NO_START_OPTI-
3079           MIZE option to pcre_compile(), pcre_exec(), or pcre_dfa_exec(),  or  by
3080           starting the pattern with (*NO_START_OPT). This slows down the matching
3081           process, but does ensure that callouts such as the  example  above  are
3082           obeyed.
3083    
3084    
3085  THE CALLOUT INTERFACE  THE CALLOUT INTERFACE
3086    
3087         During matching, when PCRE reaches a callout point, the external  func-         During  matching, when PCRE reaches a callout point, the external func-
3088         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
3089         both the pcre_exec() and the pcre_dfa_exec()  matching  functions.  The         both  the  pcre_exec()  and the pcre_dfa_exec() matching functions. The
3090         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
3091         block. This structure contains the following fields:         block. This structure contains the following fields:
3092    
3093           int          version;           int         version;
3094           int          callout_number;           int         callout_number;
3095           int         *offset_vector;           int        *offset_vector;
3096           const char  *subject;           const char *subject;
3097           int          subject_length;           int         subject_length;
3098           int          start_match;           int         start_match;
3099           int          current_position;           int         current_position;
3100           int          capture_top;           int         capture_top;
3101           int          capture_last;           int         capture_last;
3102           void        *callout_data;           void       *callout_data;
3103           int          pattern_position;           int         pattern_position;
3104           int          next_item_length;           int         next_item_length;
3105             const unsigned char *mark;
3106         The version field is an integer containing the version  number  of  the  
3107         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
3108         version number will change again in future  if  additional  fields  are         block format. The initial version was 0; the current version is 2.  The
3109           version  number  will  change  again in future if additional fields are
3110         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.
3111    
3112         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 2749  THE CALLOUT INTERFACE Line 3165  THE CALLOUT INTERFACE
3165         in  distinguishing between different automatic callouts, which all have         in  distinguishing between different automatic callouts, which all have
3166         the same callout number. However, they are set for all callouts.         the same callout number. However, they are set for all callouts.
3167    
3168           The mark field is present from version 2 of the pcre_callout structure.
3169           In  callouts  from pcre_exec() it contains a pointer to the zero-termi-
3170           nated name of the most recently passed (*MARK),  (*PRUNE),  or  (*THEN)
3171           item in the match, or NULL if no such items have been passed. Instances
3172           of (*PRUNE) or (*THEN) without a name  do  not  obliterate  a  previous
3173           (*MARK).  In  callouts  from pcre_dfa_exec() this field always contains
3174           NULL.
3175    
3176    
3177  RETURN VALUES  RETURN VALUES
3178    
# Line 2757  RETURN VALUES Line 3181  RETURN VALUES
3181         zero, matching fails at the current point, but  the  testing  of  other         zero, matching fails at the current point, but  the  testing  of  other
3182         matching possibilities goes ahead, just as if a lookahead assertion had         matching possibilities goes ahead, just as if a lookahead assertion had
3183         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
3184         pcre_exec() (or pcre_dfa_exec()) returns the negative value.         pcre_exec() or pcre_dfa_exec() returns the negative value.
3185    
3186         Negative   values   should   normally   be   chosen  from  the  set  of         Negative   values   should   normally   be   chosen  from  the  set  of
3187         PCRE_ERROR_xxx values. In particular, PCRE_ERROR_NOMATCH forces a stan-         PCRE_ERROR_xxx values. In particular, PCRE_ERROR_NOMATCH forces a stan-
# Line 2775  AUTHOR Line 3199  AUTHOR
3199    
3200  REVISION  REVISION
3201    
3202         Last updated: 29 May 2007         Last updated: 30 November 2011
3203         Copyright (c) 1997-2007 University of Cambridge.         Copyright (c) 1997-2011 University of Cambridge.
3204  ------------------------------------------------------------------------------  ------------------------------------------------------------------------------
3205    
3206    
# Line 2790  NAME Line 3214  NAME
3214  DIFFERENCES BETWEEN PCRE AND PERL  DIFFERENCES BETWEEN PCRE AND PERL
3215    
3216         This  document describes the differences in the ways that PCRE and Perl         This  document describes the differences in the ways that PCRE and Perl
3217         handle regular expressions. The differences described here  are  mainly         handle regular expressions. The differences  described  here  are  with
3218         with  respect  to  Perl 5.8, though PCRE versions 7.0 and later contain         respect to Perl versions 5.10 and above.
3219         some features that are expected to be in the forthcoming Perl 5.10.  
3220           1.  PCRE has only a subset of Perl's UTF-8 and Unicode support. Details
3221         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.
3222         of  what  it does have are given in the section on UTF-8 support in the  
3223         main pcre page.         2. PCRE allows repeat quantifiers only on parenthesized assertions, but
3224           they  do  not mean what you might think. For example, (?!a){3} does not
3225         2. PCRE does not allow repeat quantifiers on lookahead assertions. Perl         assert that the next three characters are not "a". It just asserts that
3226         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
3227         (?!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
3228         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.
3229    
3230         3.  Capturing  subpatterns  that occur inside negative lookahead asser-         3.  Capturing  subpatterns  that occur inside negative lookahead asser-
3231         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 2816  DIFFERENCES BETWEEN PCRE AND PERL Line 3240  DIFFERENCES BETWEEN PCRE AND PERL
3240         the pattern to represent a binary zero.         the pattern to represent a binary zero.
3241    
3242         5.  The  following Perl escape sequences are not supported: \l, \u, \L,         5.  The  following Perl escape sequences are not supported: \l, \u, \L,
3243         \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
3244         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
3245         are encountered by PCRE, an error is generated.         are implemented by Perl's general string-handling and are not  part  of
3246           its  pattern  matching engine. If any of these are encountered by PCRE,
3247           an error is generated by default. However, if the  PCRE_JAVASCRIPT_COM-
3248           PAT  option  is set, \U and \u are interpreted as JavaScript interprets
3249           them.
3250    
3251         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
3252         is  built  with Unicode character property support. The properties that         is  built  with Unicode character property support. The properties that
3253         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-
3254         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
3255         derived properties Any and L&.         derived properties Any and L&. PCRE does  support  the  Cs  (surrogate)
3256           property,  which  Perl  does  not; the Perl documentation says "Because
3257         7. PCRE does support the \Q...\E escape for quoting substrings. Charac-         Perl hides the need for the user to understand the internal representa-
3258         ters  in  between  are  treated as literals. This is slightly different         tion  of Unicode characters, there is no need to implement the somewhat
3259         from Perl in that $ and @ are  also  handled  as  literals  inside  the         messy concept of surrogates."
3260         quotes.  In Perl, they cause variable interpolation (but of course PCRE  
3261           7. PCRE implements a simpler version of \X than Perl, which changed  to
3262           make  \X  match what Unicode calls an "extended grapheme cluster". This
3263           is more complicated than an extended Unicode sequence,  which  is  what
3264           PCRE matches.
3265    
3266           8. PCRE does support the \Q...\E escape for quoting substrings. Charac-
3267           ters in between are treated as literals.  This  is  slightly  different
3268           from  Perl  in  that  $  and  @ are also handled as literals inside the
3269           quotes. In Perl, they cause variable interpolation (but of course  PCRE
3270         does not have variables). Note the following examples:         does not have variables). Note the following examples:
3271    
3272             Pattern            PCRE matches      Perl matches             Pattern            PCRE matches      Perl matches
# Line 2839  DIFFERENCES BETWEEN PCRE AND PERL Line 3276  DIFFERENCES BETWEEN PCRE AND PERL
3276             \Qabc\$xyz\E       abc\$xyz          abc\$xyz             \Qabc\$xyz\E       abc\$xyz          abc\$xyz
3277             \Qabc\E\$\Qxyz\E   abc$xyz           abc$xyz             \Qabc\E\$\Qxyz\E   abc$xyz           abc$xyz
3278    
3279         The \Q...\E sequence is recognized both inside  and  outside  character         The  \Q...\E  sequence  is recognized both inside and outside character
3280         classes.         classes.
3281    
3282         8. Fairly obviously, PCRE does not support the (?{code}) and (??{code})         9. Fairly obviously, PCRE does not support the (?{code}) and (??{code})
3283         constructions. However, there is support for recursive  patterns.  This         constructions.  However,  there is support for recursive patterns. This
3284         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
3285         "callout" feature allows an external function to be called during  pat-         "callout"  feature allows an external function to be called during pat-
3286         tern matching. See the pcrecallout documentation for details.         tern matching. See the pcrecallout documentation for details.
3287    
3288         9.  Subpatterns  that  are  called  recursively or as "subroutines" are         10. Subpatterns that are called as subroutines (whether or  not  recur-
3289         always treated as atomic groups in  PCRE.  This  is  like  Python,  but         sively)  are  always  treated  as  atomic  groups in PCRE. This is like
3290         unlike Perl.         Python, but unlike Perl.  Captured values that are set outside  a  sub-
3291           routine  call  can  be  reference from inside in PCRE, but not in Perl.
3292           There is a discussion that explains these differences in more detail in
3293           the section on recursion differences from Perl in the pcrepattern page.
3294    
3295           11.  If  (*THEN)  is present in a group that is called as a subroutine,
3296           its action is limited to that group, even if the group does not contain
3297           any | characters.
3298    
3299         10.  There are some differences that are concerned with the settings of         12.  There are some differences that are concerned with the settings of
3300         captured strings when part of  a  pattern  is  repeated.  For  example,         captured strings when part of  a  pattern  is  repeated.  For  example,
3301         matching  "aba"  against  the  pattern  /^(a(b)?)+$/  in Perl leaves $2         matching  "aba"  against  the  pattern  /^(a(b)?)+$/  in Perl leaves $2
3302         unset, but in PCRE it is set to "b".         unset, but in PCRE it is set to "b".
3303    
3304         11.  PCRE  does  support  Perl  5.10's  backtracking  verbs  (*ACCEPT),         13. PCRE's handling of duplicate subpattern numbers and duplicate  sub-
3305         (*FAIL),  (*F),  (*COMMIT), (*PRUNE), (*SKIP), and (*THEN), but only in         pattern names is not as general as Perl's. This is a consequence of the
3306         the forms without an  argument.  PCRE  does  not  support  (*MARK).  If         fact the PCRE works internally just with numbers, using an external ta-
3307         (*ACCEPT)  is within capturing parentheses, PCRE does not set that cap-         ble  to  translate  between numbers and names. In particular, a pattern
3308         ture group; this is different to Perl.         such as (?|(?<a>A)|(?<b)B), where the two  capturing  parentheses  have
3309           the  same  number  but different names, is not supported, and causes an
3310         12. PCRE provides some extensions to the Perl regular expression facil-         error at compile time. If it were allowed, it would not be possible  to
3311         ities.   Perl  5.10  will  include new features that are not in earlier         distinguish  which  parentheses matched, because both names map to cap-
3312         versions, some of which (such as named parentheses) have been  in  PCRE         turing subpattern number 1. To avoid this confusing situation, an error
3313         for some time. This list is with respect to Perl 5.10:         is given at compile time.
3314    
3315         (a)  Although  lookbehind  assertions  must match fixed length strings,         14.  Perl  recognizes  comments  in some places that PCRE does not, for
3316         each alternative branch of a lookbehind assertion can match a different         example, between the ( and ? at the start of a subpattern.  If  the  /x
3317         length of string. Perl requires them all to have the same length.         modifier  is set, Perl allows whitespace between ( and ? but PCRE never
3318           does, even if the PCRE_EXTENDED option is set.
3319    
3320           15. PCRE provides some extensions to the Perl regular expression facil-
3321           ities.   Perl  5.10  includes new features that are not in earlier ver-
3322           sions of Perl, some of which (such as named parentheses) have  been  in
3323           PCRE for some time. This list is with respect to Perl 5.10:
3324    
3325           (a)  Although  lookbehind  assertions  in  PCRE must match fixed length
3326           strings, each alternative branch of a lookbehind assertion can match  a
3327           different  length  of  string.  Perl requires them all to have the same
3328           length.
3329    
3330         (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  $
3331         meta-character matches only at the very end of the string.         meta-character matches only at the very end of the string.
3332    
3333         (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-
3334         cial meaning is faulted. Otherwise, like Perl, the backslash is quietly         cial meaning is faulted. Otherwise, like Perl, the backslash is quietly
3335         ignored.  (Perl can be made to issue a warning.)         ignored.  (Perl can be made to issue a warning.)
3336    
3337         (d) If PCRE_UNGREEDY is set, the greediness of the  repetition  quanti-         (d)  If  PCRE_UNGREEDY is set, the greediness of the repetition quanti-
3338         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-
3339         lowed by a question mark they are.         lowed by a question mark they are.
3340    
3341         (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
3342         tried only at the first matching position in the subject string.         tried only at the first matching position in the subject string.
3343    
3344         (f)  The PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY, and PCRE_NO_AUTO_CAP-         (f) The PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY, PCRE_NOTEMPTY_ATSTART,
3345         TURE options for pcre_exec() have no Perl equivalents.         and  PCRE_NO_AUTO_CAPTURE  options for pcre_exec() have no Perl equiva-
3346           lents.
3347    
3348         (g) The \R escape sequence can be restricted to match only CR,  LF,  or         (g) The \R escape sequence can be restricted to match only CR,  LF,  or
3349         CRLF by the PCRE_BSR_ANYCRLF option.         CRLF by the PCRE_BSR_ANYCRLF option.
# Line 2897  DIFFERENCES BETWEEN PCRE AND PERL Line 3353  DIFFERENCES BETWEEN PCRE AND PERL
3353         (i) The partial matching facility is PCRE-specific.         (i) The partial matching facility is PCRE-specific.
3354    
3355         (j) Patterns compiled by PCRE can be saved and re-used at a later time,         (j) Patterns compiled by PCRE can be saved and re-used at a later time,
3356         even on different hosts that have the other endianness.         even on different hosts that have the other endianness.  However,  this
3357           does not apply to optimized data created by the just-in-time compiler.
3358    
3359         (k) The alternative matching function (pcre_dfa_exec())  matches  in  a         (k)  The  alternative  matching function (pcre_dfa_exec()) matches in a
3360         different way and is not Perl-compatible.         different way and is not Perl-compatible.
3361    
3362         (l)  PCRE  recognizes some special sequences such as (*CR) at the start         (l) PCRE recognizes some special sequences such as (*CR) at  the  start
3363         of a pattern that set overall options that cannot be changed within the         of a pattern that set overall options that cannot be changed within the
3364         pattern.         pattern.
3365    
# Line 2916  AUTHOR Line 3373  AUTHOR
3373    
3374  REVISION  REVISION
3375    
3376         Last updated: 11 September 2007         Last updated: 14 November 2011
3377         Copyright (c) 1997-2007 University of Cambridge.         Copyright (c) 1997-2011 University of Cambridge.
3378  ------------------------------------------------------------------------------  ------------------------------------------------------------------------------
3379    
3380    
# Line 2947  PCRE REGULAR EXPRESSION DETAILS Line 3404  PCRE REGULAR EXPRESSION DETAILS
3404    
3405         The original operation of PCRE was on strings of  one-byte  characters.         The original operation of PCRE was on strings of  one-byte  characters.
3406         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
3407         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
3408         pcre_compile()  with  the  PCRE_UTF8  option.  How this affects pattern         pcre_compile()  or  pcre_compile2() with the PCRE_UTF8 option. There is
3409         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:
3410         of  UTF-8  features  in  the  section on UTF-8 support in the main pcre  
3411             (*UTF8)
3412    
3413           Starting a pattern with this sequence  is  equivalent  to  setting  the
3414           PCRE_UTF8  option.  This  feature  is  not Perl-compatible. How setting
3415           UTF-8 mode affects pattern matching  is  mentioned  in  several  places
3416           below.  There  is  also  a summary of UTF-8 features in the pcreunicode
3417         page.         page.
3418    
3419         The remainder of this document discusses the  patterns  that  are  sup-         Another special sequence that may appear at the start of a  pattern  or
3420         ported  by  PCRE when its main matching function, pcre_exec(), is used.         in combination with (*UTF8) is:
3421         From  release  6.0,   PCRE   offers   a   second   matching   function,  
3422         pcre_dfa_exec(),  which matches using a different algorithm that is not           (*UCP)
3423    
3424           This  has  the  same  effect  as setting the PCRE_UCP option: it causes
3425           sequences such as \d and \w to  use  Unicode  properties  to  determine
3426           character types, instead of recognizing only characters with codes less
3427           than 128 via a lookup table.
3428    
3429           If a pattern starts with (*NO_START_OPT), it has  the  same  effect  as
3430           setting the PCRE_NO_START_OPTIMIZE option either at compile or matching
3431           time. There are also some more of these special sequences that are con-
3432           cerned with the handling of newlines; they are described below.
3433    
3434           The  remainder  of  this  document discusses the patterns that are sup-
3435           ported by PCRE when its main matching function, pcre_exec(),  is  used.
3436           From   release   6.0,   PCRE   offers   a   second  matching  function,
3437           pcre_dfa_exec(), which matches using a different algorithm that is  not
3438         Perl-compatible. Some of the features discussed below are not available         Perl-compatible. Some of the features discussed below are not available
3439         when  pcre_dfa_exec()  is used. The advantages and disadvantages of the         when pcre_dfa_exec() is used. The advantages and disadvantages  of  the
3440         alternative function, and how it differs from the normal function,  are         alternative  function, and how it differs from the normal function, are
3441         discussed in the pcrematching page.         discussed in the pcrematching page.
3442    
3443    
3444  NEWLINE CONVENTIONS  NEWLINE CONVENTIONS
3445    
3446         PCRE  supports five different conventions for indicating line breaks in         PCRE supports five different conventions for indicating line breaks  in
3447         strings: a single CR (carriage return) character, a  single  LF  (line-         strings:  a  single  CR (carriage return) character, a single LF (line-
3448         feed) character, the two-character sequence CRLF, any of the three pre-         feed) character, the two-character sequence CRLF, any of the three pre-
3449         ceding, or any Unicode newline sequence. The pcreapi page  has  further         ceding,  or  any Unicode newline sequence. The pcreapi page has further
3450         discussion  about newlines, and shows how to set the newline convention         discussion about newlines, and shows how to set the newline  convention
3451         in the options arguments for the compiling and matching functions.         in the options arguments for the compiling and matching functions.
3452    
3453         It is also possible to specify a newline convention by starting a  pat-         It  is also possible to specify a newline convention by starting a pat-
3454         tern string with one of the following five sequences:         tern string with one of the following five sequences:
3455    
3456           (*CR)        carriage return           (*CR)        carriage return
# Line 2981  NEWLINE CONVENTIONS Line 3459  NEWLINE CONVENTIONS
3459           (*ANYCRLF)   any of the three above           (*ANYCRLF)   any of the three above
3460           (*ANY)       all Unicode newline sequences           (*ANY)       all Unicode newline sequences
3461    
3462         These override the default and the options given to pcre_compile(). For         These override the default and the options given to  pcre_compile()  or
3463         example, on a Unix system where LF is the default newline sequence, the         pcre_compile2().  For example, on a Unix system where LF is the default
3464         pattern         newline sequence, the pattern
3465    
3466           (*CR)a.b           (*CR)a.b
3467    
3468         changes the convention to CR. That pattern matches "a\nb" because LF is         changes the convention to CR. That pattern matches "a\nb" because LF is
3469         no longer a newline. Note that these special settings,  which  are  not         no  longer  a  newline. Note that these special settings, which are not
3470         Perl-compatible,  are  recognized  only at the very start of a pattern,         Perl-compatible, are recognized only at the very start  of  a  pattern,
3471         and that they must be in upper case.  If  more  than  one  of  them  is         and  that  they  must  be  in  upper  case. If more than one of them is
3472         present, the last one is used.         present, the last one is used.
3473    
3474         The  newline  convention  does  not  affect what the \R escape sequence         The newline convention affects the interpretation of the dot  metachar-
3475         matches. By default, this is any Unicode  newline  sequence,  for  Perl         acter  when  PCRE_DOTALL is not set, and also the behaviour of \N. How-
3476         compatibility.  However, this can be changed; see the description of \R         ever, it does not affect  what  the  \R  escape  sequence  matches.  By
3477         in the section entitled "Newline sequences" below. A change of \R  set-         default,  this is any Unicode newline sequence, for Perl compatibility.
3478         ting can be combined with a change of newline convention.         However, this can be changed; see the description of \R in the  section
3479           entitled  "Newline sequences" below. A change of \R setting can be com-
3480           bined with a change of newline convention.
3481    
3482    
3483  CHARACTERS AND METACHARACTERS  CHARACTERS AND METACHARACTERS
3484    
3485         A  regular  expression  is  a pattern that is matched against a subject         A regular expression is a pattern that is  matched  against  a  subject
3486         string from left to right. Most characters stand for  themselves  in  a         string  from  left  to right. Most characters stand for themselves in a
3487         pattern,  and  match  the corresponding characters in the subject. As a         pattern, and match the corresponding characters in the  subject.  As  a
3488         trivial example, the pattern         trivial example, the pattern
3489    
3490           The quick brown fox           The quick brown fox
3491    
3492         matches a portion of a subject string that is identical to itself. When         matches a portion of a subject string that is identical to itself. When
3493         caseless  matching is specified (the PCRE_CASELESS option), letters are         caseless matching is specified (the PCRE_CASELESS option), letters  are
3494         matched independently of case. In UTF-8 mode, PCRE  always  understands         matched  independently  of case. In UTF-8 mode, PCRE always understands
3495         the  concept  of case for characters whose values are less than 128, so         the concept of case for characters whose values are less than  128,  so
3496         caseless matching is always possible. For characters with  higher  val-         caseless  matching  is always possible. For characters with higher val-
3497         ues,  the concept of case is supported if PCRE is compiled with Unicode         ues, the concept of case is supported if PCRE is compiled with  Unicode
3498         property support, but not otherwise.   If  you  want  to  use  caseless         property  support,  but  not  otherwise.   If  you want to use caseless
3499         matching  for  characters  128  and above, you must ensure that PCRE is         matching for characters 128 and above, you must  ensure  that  PCRE  is
3500         compiled with Unicode property support as well as with UTF-8 support.         compiled with Unicode property support as well as with UTF-8 support.
3501    
3502         The power of regular expressions comes  from  the  ability  to  include         The  power  of  regular  expressions  comes from the ability to include
3503         alternatives  and  repetitions in the pattern. These are encoded in the         alternatives and repetitions in the pattern. These are encoded  in  the
3504         pattern by the use of metacharacters, which do not stand for themselves         pattern by the use of metacharacters, which do not stand for themselves
3505         but instead are interpreted in some special way.         but instead are interpreted in some special way.
3506    
3507         There  are  two different sets of metacharacters: those that are recog-         There are two different sets of metacharacters: those that  are  recog-
3508         nized anywhere in the pattern except within square brackets, and  those         nized  anywhere in the pattern except within square brackets, and those
3509         that  are  recognized  within square brackets. Outside square brackets,         that are recognized within square brackets.  Outside  square  brackets,
3510         the metacharacters are as follows:         the metacharacters are as follows:
3511    
3512           \      general escape character with several uses           \      general escape character with several uses
# Line 3045  CHARACTERS AND METACHARACTERS Line 3525  CHARACTERS AND METACHARACTERS
3525                  also "possessive quantifier"                  also "possessive quantifier"
3526           {      start min/max quantifier           {      start min/max quantifier
3527    
3528         Part of a pattern that is in square brackets  is  called  a  "character         Part  of  a  pattern  that is in square brackets is called a "character
3529         class". In a character class the only metacharacters are:         class". In a character class the only metacharacters are:
3530    
3531           \      general escape character           \      general escape character
# Line 3055  CHARACTERS AND METACHARACTERS Line 3535  CHARACTERS AND METACHARACTERS
3535                    syntax)                    syntax)
3536           ]      terminates the character class           ]      terminates the character class
3537    
3538         The  following sections describe the use of each of the metacharacters.         The following sections describe the use of each of the metacharacters.
3539    
3540    
3541  BACKSLASH  BACKSLASH
3542    
3543         The backslash character has several uses. Firstly, if it is followed by         The backslash character has several uses. Firstly, if it is followed by
3544         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
3545         character may have. This  use  of  backslash  as  an  escape  character         meaning that character may have. This use of  backslash  as  an  escape
3546         applies both inside and outside character classes.         character applies both inside and outside character classes.
3547    
3548         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
3549         pattern.  This escaping action applies whether  or  not  the  following         pattern.  This escaping action applies whether  or  not  the  following
# Line 3072  BACKSLASH Line 3552  BACKSLASH
3552         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-
3553         slash, you write \\.         slash, you write \\.
3554    
3555           In UTF-8 mode, only ASCII numbers and letters have any special  meaning
3556           after  a  backslash.  All  other characters (in particular, those whose
3557           codepoints are greater than 127) are treated as literals.
3558    
3559         If a pattern is compiled with the PCRE_EXTENDED option,  whitespace  in         If a pattern is compiled with the PCRE_EXTENDED option,  whitespace  in
3560         the  pattern (other than in a character class) and characters between a         the  pattern (other than in a character class) and characters between a
3561         # outside a character class and the next newline are ignored. An escap-         # outside a character class and the next newline are ignored. An escap-
# Line 3092  BACKSLASH Line 3576  BACKSLASH
3576           \Qabc\E\$\Qxyz\E   abc$xyz        abc$xyz           \Qabc\E\$\Qxyz\E   abc$xyz        abc$xyz
3577    
3578         The \Q...\E sequence is recognized both inside  and  outside  character         The \Q...\E sequence is recognized both inside  and  outside  character
3579         classes.         classes.   An  isolated \E that is not preceded by \Q is ignored. If \Q
3580           is not followed by \E later in the pattern, the literal  interpretation
3581           continues  to  the  end  of  the pattern (that is, \E is assumed at the
3582           end). If the isolated \Q is inside a character class,  this  causes  an
3583           error, because the character class is not terminated.
3584    
3585     Non-printing characters     Non-printing characters
3586    
# Line 3100  BACKSLASH Line 3588  BACKSLASH
3588         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
3589         appearance  of non-printing characters, apart from the binary zero that         appearance  of non-printing characters, apart from the binary zero that
3590         terminates a pattern, but when a pattern  is  being  prepared  by  text         terminates a pattern, but when a pattern  is  being  prepared  by  text
3591         editing,  it  is  usually  easier  to  use  one of the following escape         editing,  it  is  often  easier  to  use  one  of  the following escape
3592         sequences than the binary character it represents:         sequences than the binary character it represents:
3593    
3594           \a        alarm, that is, the BEL character (hex 07)           \a        alarm, that is, the BEL character (hex 07)
3595           \cx       "control-x", where x is any character           \cx       "control-x", where x is any ASCII character
3596           \e        escape (hex 1B)           \e        escape (hex 1B)
3597           \f        formfeed (hex 0C)           \f        formfeed (hex 0C)
3598           \n        linefeed (hex 0A)           \n        linefeed (hex 0A)
3599           \r        carriage return (hex 0D)           \r        carriage return (hex 0D)
3600           \t        tab (hex 09)           \t        tab (hex 09)
3601           \ddd      character with octal code ddd, or backreference           \ddd      character with octal code ddd, or back reference
3602           \xhh      character with hex code hh           \xhh      character with hex code hh
3603           \x{hhh..} character with hex code hhh..           \x{hhh..} character with hex code hhh.. (non-JavaScript mode)
3604             \uhhhh    character with hex code hhhh (JavaScript mode only)
3605    
3606         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,
3607         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
3608         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 ({
3609         becomes hex 7B.         is  7B),  while  \c; becomes hex 7B (; is 3B). If the byte following \c
3610           has a value greater than 127, a compile-time error occurs.  This  locks
3611         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
3612         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
3613         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.)
3614         than 256 in non-UTF-8 mode, and less than 2**31 in UTF-8 mode. That is,  
3615         the  maximum value in hexadecimal is 7FFFFFFF. Note that this is bigger         By  default,  after  \x,  from  zero to two hexadecimal digits are read
3616         than the largest Unicode code point, which is 10FFFF.         (letters can be in upper or lower case). Any number of hexadecimal dig-
3617           its  may  appear between \x{ and }, but the value of the character code
3618           must be less than 256 in non-UTF-8 mode, and less than 2**31  in  UTF-8
3619           mode.  That is, the maximum value in hexadecimal is 7FFFFFFF. Note that
3620           this is bigger than the largest Unicode code point, which is 10FFFF.
3621    
3622         If characters other than hexadecimal digits appear between \x{  and  },         If characters other than hexadecimal digits appear between \x{  and  },
3623         or if there is no terminating }, this form of escape is not recognized.         or if there is no terminating }, this form of escape is not recognized.
# Line 3132  BACKSLASH Line 3625  BACKSLASH
3625         escape,  with  no  following  digits, giving a character whose value is         escape,  with  no  following  digits, giving a character whose value is
3626         zero.         zero.
3627    
3628           If the PCRE_JAVASCRIPT_COMPAT option is set, the interpretation  of  \x
3629           is  as  just described only when it is followed by two hexadecimal dig-
3630           its.  Otherwise, it matches a  literal  "x"  character.  In  JavaScript
3631           mode, support for code points greater than 256 is provided by \u, which
3632           must be followed by four hexadecimal digits;  otherwise  it  matches  a
3633           literal "u" character.
3634    
3635         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
3636         two  syntaxes  for  \x. There is no difference in the way they are han-         two syntaxes for \x (or by \u in JavaScript mode). There is no  differ-
3637         dled. For example, \xdc is exactly the same as \x{dc}.         ence in the way they are handled. For example, \xdc is exactly the same
3638           as \x{dc} (or \u00dc in JavaScript mode).
3639    
3640         After \0 up to two further octal digits are read. If  there  are  fewer         After \0 up to two further octal digits are read. If  there  are  fewer
3641         than  two  digits,  just  those  that  are  present  are used. Thus the         than  two  digits,  just  those  that  are  present  are used. Thus the
# Line 3178  BACKSLASH Line 3679  BACKSLASH
3679    
3680         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
3681         inside and outside character classes. In addition, inside  a  character         inside and outside character classes. In addition, inside  a  character
3682         class,  the  sequence \b is interpreted as the backspace character (hex         class, \b is interpreted as the backspace character (hex 08).
3683         08), and the sequences \R and \X are interpreted as the characters  "R"  
3684         and  "X", respectively. Outside a character class, these sequences have         \N  is not allowed in a character class. \B, \R, and \X are not special
3685         different meanings (see below).         inside a character class. Like  other  unrecognized  escape  sequences,
3686           they  are  treated  as  the  literal  characters  "B",  "R", and "X" by
3687           default, but cause an error if the PCRE_EXTRA option is set. Outside  a
3688           character class, these sequences have different meanings.
3689    
3690       Unsupported escape sequences
3691    
3692           In  Perl, the sequences \l, \L, \u, and \U are recognized by its string
3693           handler and used  to  modify  the  case  of  following  characters.  By
3694           default,  PCRE does not support these escape sequences. However, if the
3695           PCRE_JAVASCRIPT_COMPAT option is set, \U matches a "U"  character,  and
3696           \u can be used to define a character by code point, as described in the
3697           previous section.
3698    
3699     Absolute and relative back references     Absolute and relative back references
3700    
# Line 3201  BACKSLASH Line 3714  BACKSLASH
3714    
3715     Generic character types     Generic character types
3716    
3717         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:  
3718    
3719           \d     any decimal digit           \d     any decimal digit
3720           \D     any character that is not a decimal digit           \D     any character that is not a decimal digit
# Line 3215  BACKSLASH Line 3727  BACKSLASH
3727           \w     any "word" character           \w     any "word" character
3728           \W     any "non-word" character           \W     any "non-word" character
3729    
3730         Each pair of escape sequences partitions the complete set of characters         There is also the single sequence \N, which matches a non-newline char-
3731         into two disjoint sets. Any given character matches one, and only  one,         acter.   This  is the same as the "." metacharacter when PCRE_DOTALL is
3732         of each pair.         not set. Perl also uses \N to match characters by name; PCRE  does  not
3733           support this.
3734         These character type sequences can appear both inside and outside char-  
3735         acter classes. They each match one character of the  appropriate  type.         Each  pair of lower and upper case escape sequences partitions the com-
3736         If  the current matching point is at the end of the subject string, all         plete set of characters into two disjoint  sets.  Any  given  character
3737         of them fail, since there is no character to match.         matches  one, and only one, of each pair. The sequences can appear both
3738           inside and outside character classes. They each match one character  of
3739         For compatibility with Perl, \s does not match the VT  character  (code         the  appropriate  type.  If the current matching point is at the end of
3740         11).   This makes it different from the the POSIX "space" class. The \s         the subject string, all of them fail, because there is no character  to
3741         characters are HT (9), LF (10), FF (12), CR (13), and  space  (32).  If         match.
3742    
3743           For  compatibility  with Perl, \s does not match the VT character (code
3744           11).  This makes it different from the the POSIX "space" class. The  \s
3745           characters  are  HT  (9), LF (10), FF (12), CR (13), and space (32). If
3746         "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-
3747         ter. In PCRE, it never does.         ter. In PCRE, it never does.
3748    
3749         In UTF-8 mode, characters with values greater than 128 never match  \d,         A  "word"  character is an underscore or any character that is a letter
3750         \s, or \w, and always match \D, \S, and \W. This is true even when Uni-         or digit.  By default, the definition of letters  and  digits  is  con-
3751         code character property support is available.  These  sequences  retain         trolled  by PCRE's low-valued character tables, and may vary if locale-
3752         their original meanings from before UTF-8 support was available, mainly         specific matching is taking place (see "Locale support" in the  pcreapi
3753         for efficiency reasons.         page).  For  example,  in  a French locale such as "fr_FR" in Unix-like
3754           systems, or "french" in Windows, some character codes greater than  128
3755         The sequences \h, \H, \v, and \V are Perl 5.10 features. In contrast to         are  used  for  accented letters, and these are then matched by \w. The
3756         the  other  sequences, these do match certain high-valued codepoints in         use of locales with Unicode is discouraged.
3757         UTF-8 mode.  The horizontal space characters are:  
3758           By default, in UTF-8 mode, characters  with  values  greater  than  128
3759           never  match  \d,  \s,  or  \w,  and always match \D, \S, and \W. These
3760           sequences retain their original meanings from before UTF-8 support  was
3761           available,  mainly for efficiency reasons. However, if PCRE is compiled
3762           with Unicode property support, and the PCRE_UCP option is set, the  be-
3763           haviour  is  changed  so  that Unicode properties are used to determine
3764           character types, as follows:
3765    
3766             \d  any character that \p{Nd} matches (decimal digit)
3767             \s  any character that \p{Z} matches, plus HT, LF, FF, CR
3768             \w  any character that \p{L} or \p{N} matches, plus underscore
3769    
3770           The upper case escapes match the inverse sets of characters. Note  that
3771           \d  matches  only decimal digits, whereas \w matches any Unicode digit,
3772           as well as any Unicode letter, and underscore. Note also that  PCRE_UCP
3773           affects  \b,  and  \B  because  they are defined in terms of \w and \W.
3774           Matching these sequences is noticeably slower when PCRE_UCP is set.
3775    
3776           The sequences \h, \H, \v, and \V are features that were added  to  Perl
3777           at  release  5.10. In contrast to the other sequences, which match only
3778           ASCII characters by default, these  always  match  certain  high-valued
3779           codepoints  in UTF-8 mode, whether or not PCRE_UCP is set. The horizon-
3780           tal space characters are:
3781    
3782           U+0009     Horizontal tab           U+0009     Horizontal tab
3783           U+0020     Space           U+0020     Space
# Line 3270  BACKSLASH Line 3809  BACKSLASH
3809           U+2028     Line separator           U+2028     Line separator
3810           U+2029     Paragraph separator           U+2029     Paragraph separator
3811    
        A "word" character is an underscore or any character less than 256 that  
        is  a  letter  or  digit.  The definition of letters and digits is con-  
        trolled by PCRE's low-valued character tables, and may vary if  locale-  
        specific  matching is taking place (see "Locale support" in the pcreapi  
        page). For example, in a French locale such  as  "fr_FR"  in  Unix-like  
        systems,  or "french" in Windows, some character codes greater than 128  
        are used for accented letters, and these are matched by \w. The use  of  
        locales with Unicode is discouraged.  
   
3812     Newline sequences     Newline sequences
3813    
3814         Outside  a  character class, by default, the escape sequence \R matches         Outside a character class, by default, the escape sequence  \R  matches
3815         any Unicode newline sequence. This is a Perl 5.10 feature. In non-UTF-8         any Unicode newline sequence. In non-UTF-8 mode \R is equivalent to the
3816         mode \R is equivalent to the following:         following:
3817    
3818           (?>\r\n|\n|\x0b|\f|\r|\x85)           (?>\r\n|\n|\x0b|\f|\r|\x85)
3819    
3820         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
3821         below.  This particular group matches either the two-character sequence         below.  This particular group matches either the two-character sequence
3822         CR  followed  by  LF,  or  one  of  the single characters LF (linefeed,         CR followed by LF, or  one  of  the  single  characters  LF  (linefeed,
3823         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
3824         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
3825         is treated as a single unit that cannot be split.         is treated as a single unit that cannot be split.
3826    
3827         In UTF-8 mode, two additional characters whose codepoints  are  greater         In  UTF-8  mode, two additional characters whose codepoints are greater
3828         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-
3829         rator, U+2029).  Unicode character property support is not  needed  for         rator,  U+2029).   Unicode character property support is not needed for
3830         these characters to be recognized.         these characters to be recognized.
3831    
3832         It is possible to restrict \R to match only CR, LF, or CRLF (instead of         It is possible to restrict \R to match only CR, LF, or CRLF (instead of
3833         the complete set  of  Unicode  line  endings)  by  setting  the  option         the  complete  set  of  Unicode  line  endings)  by  setting the option
3834         PCRE_BSR_ANYCRLF either at compile time or when the pattern is matched.         PCRE_BSR_ANYCRLF either at compile time or when the pattern is matched.
3835         (BSR is an abbrevation for "backslash R".) This can be made the default         (BSR is an abbrevation for "backslash R".) This can be made the default
3836         when  PCRE  is  built;  if this is the case, the other behaviour can be         when PCRE is built; if this is the case, the  other  behaviour  can  be
3837         requested via the PCRE_BSR_UNICODE option.   It  is  also  possible  to         requested  via  the  PCRE_BSR_UNICODE  option.   It is also possible to
3838         specify  these  settings  by  starting a pattern string with one of the         specify these settings by starting a pattern string  with  one  of  the
3839         following sequences:         following sequences:
3840    
3841           (*BSR_ANYCRLF)   CR, LF, or CRLF only           (*BSR_ANYCRLF)   CR, LF, or CRLF only
3842           (*BSR_UNICODE)   any Unicode newline sequence           (*BSR_UNICODE)   any Unicode newline sequence
3843    
3844         These override the default and the options given to pcre_compile(), but         These  override  the default and the options given to pcre_compile() or
3845         they can be overridden by options given to pcre_exec(). Note that these         pcre_compile2(), but  they  can  be  overridden  by  options  given  to
3846         special settings, which are not Perl-compatible, are recognized only at         pcre_exec() or pcre_dfa_exec(). Note that these special settings, which
3847         the  very  start  of a pattern, and that they must be in upper case. If         are not Perl-compatible, are recognized only at the  very  start  of  a
3848         more than one of them is present, the last one is  used.  They  can  be         pattern,  and that they must be in upper case. If more than one of them
3849         combined  with  a  change of newline convention, for example, a pattern         is present, the last one is used. They can be combined with a change of
3850         can start with:         newline convention; for example, a pattern can start with:
3851    
3852           (*ANY)(*BSR_ANYCRLF)           (*ANY)(*BSR_ANYCRLF)
3853    
3854         Inside a character class, \R matches the letter "R".         They can also be combined with the (*UTF8) or (*UCP) special sequences.
3855           Inside a character class, \R  is  treated  as  an  unrecognized  escape
3856           sequence, and so matches the letter "R" by default, but causes an error
3857           if PCRE_EXTRA is set.
3858    
3859     Unicode character properties     Unicode character properties
3860    
# Line 3336  BACKSLASH Line 3869  BACKSLASH
3869           \X       an extended Unicode sequence           \X       an extended Unicode sequence
3870    
3871         The property names represented by xx above are limited to  the  Unicode         The property names represented by xx above are limited to  the  Unicode
3872         script names, the general category properties, and "Any", which matches         script names, the general category properties, "Any", which matches any
3873         any character (including newline). Other properties such as "InMusical-         character  (including  newline),  and  some  special  PCRE   properties
3874