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revision 211 by ph10, Thu Aug 9 09:52:43 2007 UTC revision 691 by ph10, Sun Sep 11 14:31:21 2011 UTC
# Line 2  Line 2 
2  This file contains a concatenation of the PCRE man pages, converted to plain  This file contains a concatenation of the PCRE man pages, converted to plain
3  text format for ease of searching with a text editor, or for use on systems  text format for ease of searching with a text editor, or for use on systems
4  that do not have a man page processor. The small individual files that give  that do not have a man page processor. The small individual files that give
5  synopses of each function in the library have not been included. There are  synopses of each function in the library have not been included. Neither has
6  separate text files for the pcregrep and pcretest commands.  the pcredemo program. There are separate text files for the pcregrep and
7    pcretest commands.
8  -----------------------------------------------------------------------------  -----------------------------------------------------------------------------
9    
10    
# Line 18  INTRODUCTION Line 19  INTRODUCTION
19    
20         The  PCRE  library is a set of functions that implement regular expres-         The  PCRE  library is a set of functions that implement regular expres-
21         sion pattern matching using the same syntax and semantics as Perl, with         sion pattern matching using the same syntax and semantics as Perl, with
22         just  a  few differences. (Certain features that appeared in Python and         just  a few differences. Some features that appeared in Python and PCRE
23         PCRE before they appeared in Perl are also available using  the  Python         before they appeared in Perl are also available using the  Python  syn-
24         syntax.)         tax,  there  is  some  support for one or two .NET and Oniguruma syntax
25           items, and there is an option for requesting some  minor  changes  that
26         The  current  implementation of PCRE (release 7.x) corresponds approxi-         give better JavaScript compatibility.
27         mately with Perl 5.10, including support for UTF-8 encoded strings  and  
28         Unicode general category properties. However, UTF-8 and Unicode support         The  current implementation of PCRE corresponds approximately with Perl
29         has to be explicitly enabled; it is not the default. The Unicode tables         5.12, including support for UTF-8 encoded strings and  Unicode  general
30         correspond to Unicode release 5.0.0.         category  properties.  However,  UTF-8  and  Unicode  support has to be
31           explicitly enabled; it is not the default. The  Unicode  tables  corre-
32           spond to Unicode release 6.0.0.
33    
34         In  addition to the Perl-compatible matching function, PCRE contains an         In  addition to the Perl-compatible matching function, PCRE contains an
35         alternative matching function that matches the same  compiled  patterns         alternative function that matches the same compiled patterns in a  dif-
36         in  a different way. In certain circumstances, the alternative function         ferent way. In certain circumstances, the alternative function has some
37         has some advantages. For a discussion of the two  matching  algorithms,         advantages.  For a discussion of the two matching algorithms,  see  the
38         see the pcrematching page.         pcrematching page.
39    
40         PCRE  is  written  in C and released as a C library. A number of people         PCRE  is  written  in C and released as a C library. A number of people
41         have written wrappers and interfaces of various kinds.  In  particular,         have written wrappers and interfaces of various kinds.  In  particular,
# Line 52  INTRODUCTION Line 55  INTRODUCTION
55         library is built. The pcre_config() function makes it  possible  for  a         library is built. The pcre_config() function makes it  possible  for  a
56         client  to  discover  which  features are available. The features them-         client  to  discover  which  features are available. The features them-
57         selves are described in the pcrebuild page. Documentation about  build-         selves are described in the pcrebuild page. Documentation about  build-
58         ing  PCRE for various operating systems can be found in the README file         ing  PCRE  for various operating systems can be found in the README and
59         in the source distribution.         NON-UNIX-USE files in the source distribution.
60    
61         The library contains a number of undocumented  internal  functions  and         The library contains a number of undocumented  internal  functions  and
62         data  tables  that  are  used by more than one of the exported external         data  tables  that  are  used by more than one of the exported external
# Line 69  USER DOCUMENTATION Line 72  USER DOCUMENTATION
72         The user documentation for PCRE comprises a number  of  different  sec-         The user documentation for PCRE comprises a number  of  different  sec-
73         tions.  In the "man" format, each of these is a separate "man page". In         tions.  In the "man" format, each of these is a separate "man page". In
74         the HTML format, each is a separate page, linked from the  index  page.         the HTML format, each is a separate page, linked from the  index  page.
75         In  the  plain text format, all the sections are concatenated, for ease         In  the  plain  text format, all the sections, except the pcredemo sec-
76         of searching. The sections are as follows:         tion, are concatenated, for ease of searching. The sections are as fol-
77           lows:
78    
79           pcre              this document           pcre              this document
80           pcre-config       show PCRE installation configuration information           pcre-config       show PCRE installation configuration information
# Line 79  USER DOCUMENTATION Line 83  USER DOCUMENTATION
83           pcrecallout       details of the callout feature           pcrecallout       details of the callout feature
84           pcrecompat        discussion of Perl compatibility           pcrecompat        discussion of Perl compatibility
85           pcrecpp           details of the C++ wrapper           pcrecpp           details of the C++ wrapper
86             pcredemo          a demonstration C program that uses PCRE
87           pcregrep          description of the pcregrep command           pcregrep          description of the pcregrep command
88             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: 09 August 2007         Last updated: 24 August 2011
121         Copyright (c) 1997-2007 University of Cambridge.         Copyright (c) 1997-2011 University of Cambridge.
122  ------------------------------------------------------------------------------  ------------------------------------------------------------------------------
123    
124    
# Line 271  NAME Line 132  NAME
132  PCRE BUILD-TIME OPTIONS  PCRE BUILD-TIME OPTIONS
133    
134         This  document  describes  the  optional  features  of PCRE that can be         This  document  describes  the  optional  features  of PCRE that can be
135         selected when the library is compiled. They are all selected, or  dese-         selected when the library is compiled. It assumes use of the  configure
136         lected, by providing options to the configure script that is run before         script,  where the optional features are selected or deselected by pro-
137         the make command. The complete list of  options  for  configure  (which         viding options to configure before running the make  command.  However,
138         includes  the  standard  ones such as the selection of the installation         the  same  options  can be selected in both Unix-like and non-Unix-like
139         directory) can be obtained by running         environments using the GUI facility of cmake-gui if you are using CMake
140           instead of configure to build PCRE.
141    
142           There  is  a  lot more information about building PCRE in non-Unix-like
143           environments in the file called NON_UNIX_USE, which is part of the PCRE
144           distribution.  You  should consult this file as well as the README file
145           if you are building in a non-Unix-like environment.
146    
147           The complete list of options for configure (which includes the standard
148           ones  such  as  the  selection  of  the  installation directory) can be
149           obtained by running
150    
151           ./configure --help           ./configure --help
152    
# Line 287  PCRE BUILD-TIME OPTIONS Line 158  PCRE BUILD-TIME OPTIONS
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 300  C++ SUPPORT Line 183  C++ SUPPORT
183    
184  UTF-8 SUPPORT  UTF-8 SUPPORT
185    
186         To build PCRE with support for UTF-8 character strings, add         To build PCRE with support for UTF-8 Unicode character strings, add
187    
188           --enable-utf8           --enable-utf8
189    
190         to  the  configure  command.  Of  itself, this does not make PCRE treat         to  the  configure  command.  Of  itself, this does not make PCRE treat
191         strings as UTF-8. As well as compiling PCRE with this option, you  also         strings as UTF-8. As well as compiling PCRE with this option, you  also
192         have  have to set the PCRE_UTF8 option when you call the pcre_compile()         have  have to set the PCRE_UTF8 option when you call the pcre_compile()
193         function.         or pcre_compile2() functions.
194    
195           If you set --enable-utf8 when compiling in an EBCDIC environment,  PCRE
196           expects its input to be either ASCII or UTF-8 (depending on the runtime
197           option). It is not possible to support both EBCDIC and UTF-8  codes  in
198           the  same  version  of  the  library.  Consequently,  --enable-utf8 and
199           --enable-ebcdic are mutually exclusive.
200    
201    
202  UNICODE CHARACTER PROPERTY SUPPORT  UNICODE CHARACTER PROPERTY SUPPORT
# Line 328  UNICODE CHARACTER PROPERTY SUPPORT Line 217  UNICODE CHARACTER PROPERTY SUPPORT
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    
# Line 356  CODE VALUE OF NEWLINE Line 262  CODE VALUE OF NEWLINE
262    
263         causes PCRE to recognize any Unicode newline sequence.         causes PCRE to recognize any Unicode newline sequence.
264    
265         Whatever line ending convention is selected when PCRE is built  can  be         Whatever  line  ending convention is selected when PCRE is built can be
266         overridden  when  the library functions are called. At build time it is         overridden when the library functions are called. At build time  it  is
267         conventional to use the standard for your operating system.         conventional to use the standard for your operating system.
268    
269    
270  BUILDING SHARED AND STATIC LIBRARIES  WHAT \R MATCHES
271    
272         The PCRE building process uses libtool to build both shared and  static         By  default,  the  sequence \R in a pattern matches any Unicode newline
273         Unix  libraries by default. You can suppress one of these by adding one         sequence, whatever has been selected as the line  ending  sequence.  If
274         of         you specify
275    
276           --disable-shared           --enable-bsr-anycrlf
          --disable-static  
277    
278         to the configure command, as required.         the  default  is changed so that \R matches only CR, LF, or CRLF. What-
279           ever is selected when PCRE is built can be overridden when the  library
280           functions are called.
281    
282    
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-
286         umentation),  additional  working  storage  is required for holding the         umentation), additional working storage is  required  for  holding  the
287         pointers to capturing substrings, because PCRE requires three  integers         pointers  to capturing substrings, because PCRE requires three integers
288         per  substring,  whereas  the POSIX interface provides only two. If the         per substring, whereas the POSIX interface provides only  two.  If  the
289         number of expected substrings is small, the wrapper function uses space         number of expected substrings is small, the wrapper function uses space
290         on the stack, because this is faster than using malloc() for each call.         on the stack, because this is faster than using malloc() for each call.
291         The default threshold above which the stack is no longer used is 10; it         The default threshold above which the stack is no longer used is 10; it
# Line 391  POSIX MALLOC USAGE Line 298  POSIX MALLOC USAGE
298    
299  HANDLING VERY LARGE PATTERNS  HANDLING VERY LARGE PATTERNS
300    
301         Within  a  compiled  pattern,  offset values are used to point from one         Within a compiled pattern, offset values are used  to  point  from  one
302         part to another (for example, from an opening parenthesis to an  alter-         part  to another (for example, from an opening parenthesis to an alter-
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    
312         to the configure command. The value given must be 2,  3,  or  4.  Using         to  the  configure  command.  The value given must be 2, 3, or 4. Using
313         longer  offsets slows down the operation of PCRE because it has to load         longer offsets slows down the operation of PCRE because it has to  load
314         additional bytes when handling them.         additional bytes when handling them.
315    
316    
317  AVOIDING EXCESSIVE STACK USAGE  AVOIDING EXCESSIVE STACK USAGE
318    
319         When matching with the pcre_exec() function, PCRE implements backtrack-         When matching with the pcre_exec() function, PCRE implements backtrack-
320         ing  by  making recursive calls to an internal function called match().         ing by making recursive calls to an internal function  called  match().
321         In environments where the size of the stack is limited,  this  can  se-         In  environments  where  the size of the stack is limited, this can se-
322         verely  limit  PCRE's operation. (The Unix environment does not usually         verely limit PCRE's operation. (The Unix environment does  not  usually
323         suffer from this problem, but it may sometimes be necessary to increase         suffer from this problem, but it may sometimes be necessary to increase
324         the  maximum  stack size.  There is a discussion in the pcrestack docu-         the maximum stack size.  There is a discussion in the  pcrestack  docu-
325         mentation.) An alternative approach to recursion that uses memory  from         mentation.)  An alternative approach to recursion that uses memory from
326         the  heap  to remember data, instead of using recursive function calls,         the heap to remember data, instead of using recursive  function  calls,
327         has been implemented to work round the problem of limited  stack  size.         has  been  implemented to work round the problem of limited stack size.
328         If you want to build a version of PCRE that works this way, add         If you want to build a version of PCRE that works this way, add
329    
330           --disable-stack-for-recursion           --disable-stack-for-recursion
331    
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
339         requested are always the same, and  the  blocks  are  always  freed  in         requested  are  always  the  same,  and  the blocks are always freed in
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
# Line 496  USING EBCDIC CODE Line 402  USING EBCDIC CODE
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
410    
411           By default, pcregrep reads all files as plain text. You can build it so
412           that it recognizes files whose names end in .gz or .bz2, and reads them
413           with libz or libbz2, respectively, by adding one or both of
414    
415             --enable-pcregrep-libz
416             --enable-pcregrep-libbz2
417    
418           to the configure command. These options naturally require that the rel-
419           evant libraries are installed on your system. Configuration  will  fail
420           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
440    
441           If you add
442    
443             --enable-pcretest-libreadline
444    
445           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
447           readline() function. This provides line-editing and history facilities.
448           Note that libreadline is GPL-licensed, so if you distribute a binary of
449           pcretest linked in this way, there may be licensing issues.
450    
451           Setting this option causes the -lreadline option to  be  added  to  the
452           pcretest  build.  In many operating environments with a sytem-installed
453           libreadline this is sufficient. However, in some environments (e.g.  if
454           an  unmodified  distribution version of readline is in use), some extra
455           configuration may be necessary. The INSTALL file for  libreadline  says
456           this:
457    
458             "Readline uses the termcap functions, but does not link with the
459             termcap or curses library itself, allowing applications which link
460             with readline the to choose an appropriate library."
461    
462           If  your environment has not been set up so that an appropriate library
463           is automatically included, you may need to add something like
464    
465             LIBS="-ncurses"
466    
467           immediately before the configure command.
468    
469    
470  SEE ALSO  SEE ALSO
# Line 513  AUTHOR Line 481  AUTHOR
481    
482  REVISION  REVISION
483    
484         Last updated: 30 July 2007         Last updated: 06 September 2011
485         Copyright (c) 1997-2007 University of Cambridge.         Copyright (c) 1997-2011 University of Cambridge.
486  ------------------------------------------------------------------------------  ------------------------------------------------------------------------------
487    
488    
# Line 601  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 because the  alterna-
637         tive algorithm moves through the subject  string  one  character  at  a         tive  algorithm  moves  through  the  subject string one character at a
638         time, for all active paths through the tree.         time, for all active paths through the tree.
639    
640         8.  None  of  the  backtracking control verbs such as (*PRUNE) are sup-         8. Except for (*FAIL), the backtracking control verbs such as  (*PRUNE)
641         ported.         are  not  supported.  (*FAIL)  is supported, and behaves like a failing
642           negative assertion.
643    
644    
645  ADVANTAGES OF THE ALTERNATIVE ALGORITHM  ADVANTAGES OF THE ALTERNATIVE ALGORITHM
# Line 676  ADVANTAGES OF THE ALTERNATIVE ALGORITHM Line 652  ADVANTAGES OF THE ALTERNATIVE ALGORITHM
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
        on  the content of the pattern that apply when using the standard algo-  
        rithm for partial matching do not apply to the  alternative  algorithm.  
        For  non-anchored patterns, the starting position of a partial match is  
        available.  
   
        3. Because the alternative algorithm  scans  the  subject  string  just  
656         once,  and  never  needs to backtrack, it is possible to pass very long         once,  and  never  needs to backtrack, it is possible to pass very long
657         subject strings to the matching function in  several  pieces,  checking         subject strings to the matching function in  several  pieces,  checking
658         for partial matching each time.         for  partial  matching  each time. Although it is possible to do multi-
659           segment matching using the standard algorithm (pcre_exec()), by retain-
660           ing  partially matched substrings, it is more complicated. The pcrepar-
661           tial documentation gives details  of  partial  matching  and  discusses
662           multi-segment matching.
663    
664    
665  DISADVANTAGES OF THE ALTERNATIVE ALGORITHM  DISADVANTAGES OF THE ALTERNATIVE ALGORITHM
# Line 711  AUTHOR Line 685  AUTHOR
685    
686  REVISION  REVISION
687    
688         Last updated: 08 August 2007         Last updated: 17 November 2010
689         Copyright (c) 1997-2007 University of Cambridge.         Copyright (c) 1997-2010 University of Cambridge.
690  ------------------------------------------------------------------------------  ------------------------------------------------------------------------------
691    
692    
# Line 723  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 739  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 792  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 807  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         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 849  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
920           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
922           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. The choice of newline convention  does         ment for a non-anchored pattern. There is more detail about this in the
930         not affect the interpretation of the \n or \r escape sequences.         section on pcre_exec() options below.
931    
932           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,
934           which is controlled in a similar way, but by separate options.
935    
936    
937  MULTITHREADING  MULTITHREADING
# Line 924  MULTITHREADING Line 941  MULTITHREADING
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.
943    
944         The  compiled form of a regular expression is not altered during match-         The compiled form of a regular expression is not altered during  match-
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    
955         The compiled form of a regular expression can be saved and re-used at a         The compiled form of a regular expression can be saved and re-used at a
956         later time, possibly by a different program, and even on a  host  other         later  time,  possibly by a different program, and even on a host other
957         than  the  one  on  which  it  was  compiled.  Details are given in the         than the one on which  it  was  compiled.  Details  are  given  in  the
958         pcreprecompile documentation. However, compiling a  regular  expression         pcreprecompile  documentation.  However, compiling a regular expression
959         with  one version of PCRE for use with a different version is not guar-         with one version of PCRE for use with a different version is not  guar-
960         anteed to work and may cause crashes.         anteed to work and may cause crashes.
961    
962    
# Line 943  CHECKING BUILD-TIME OPTIONS Line 964  CHECKING BUILD-TIME OPTIONS
964    
965         int pcre_config(int what, void *where);         int pcre_config(int what, void *where);
966    
967         The function pcre_config() makes it possible for a PCRE client to  dis-         The  function pcre_config() makes it possible for a PCRE client to dis-
968         cover which optional features have been compiled into the PCRE library.         cover which optional features have been compiled into the PCRE library.
969         The pcrebuild documentation has more details about these optional  fea-         The  pcrebuild documentation has more details about these optional fea-
970         tures.         tures.
971    
972         The  first  argument  for pcre_config() is an integer, specifying which         The first argument for pcre_config() is an  integer,  specifying  which
973         information is required; the second argument is a pointer to a variable         information is required; the second argument is a pointer to a variable
974         into  which  the  information  is  placed. The following information is         into which the information is  placed.  The  following  information  is
975         available:         available:
976    
977           PCRE_CONFIG_UTF8           PCRE_CONFIG_UTF8
978    
979         The output is an integer that is set to one if UTF-8 support is  avail-         The  output is an integer that is set to one if UTF-8 support is avail-
980         able; otherwise it is set to zero.         able; otherwise it is set to zero.
981    
982           PCRE_CONFIG_UNICODE_PROPERTIES           PCRE_CONFIG_UNICODE_PROPERTIES
983    
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
1002    
1003           The output is an integer whose value indicates what character sequences
1004           the \R escape sequence matches by default. A value of 0 means  that  \R
1005           matches  any  Unicode  line ending sequence; a value of 1 means that \R
1006           matches only CR, LF, or CRLF. The default can be overridden when a pat-
1007           tern is compiled or matched.
1008    
1009           PCRE_CONFIG_LINK_SIZE           PCRE_CONFIG_LINK_SIZE
1010    
1011         The output is an integer that contains the number  of  bytes  used  for         The  output  is  an  integer that contains the number of bytes used for
1012         internal linkage in compiled regular expressions. The value is 2, 3, or         internal linkage in compiled regular expressions. The value is 2, 3, or
1013         4. Larger values allow larger regular expressions to  be  compiled,  at         4.  Larger  values  allow larger regular expressions to be compiled, at
1014         the  expense  of  slower matching. The default value of 2 is sufficient         the expense of slower matching. The default value of  2  is  sufficient
1015         for all but the most massive patterns, since  it  allows  the  compiled         for  all  but  the  most massive patterns, since it allows the compiled
1016         pattern to be up to 64K in size.         pattern to be up to 64K in size.
1017    
1018           PCRE_CONFIG_POSIX_MALLOC_THRESHOLD           PCRE_CONFIG_POSIX_MALLOC_THRESHOLD
1019    
1020         The  output  is  an integer that contains the threshold above which the         The output is an integer that contains the threshold  above  which  the
1021         POSIX interface uses malloc() for output vectors. Further  details  are         POSIX  interface  uses malloc() for output vectors. Further details are
1022         given in the pcreposix documentation.         given in the pcreposix documentation.
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    
# Line 1023  COMPILING A PATTERN Line 1059  COMPILING A PATTERN
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
# Line 1040  COMPILING A PATTERN Line 1078  COMPILING A PATTERN
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         If pcre_compile2() is used instead of pcre_compile(),  and  the  error-         Also, some errors are not detected until checks are  carried  out  when
1101         codeptr  argument is not NULL, a non-zero error code number is returned         the  whole  pattern  has been scanned; in these cases the offset passed
1102         via this argument in the event of an error. This is in addition to  the         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-
1108           codeptr argument is not NULL, a non-zero error code number is  returned
1109           via  this argument in the event of an error. This is in addition to the
1110         textual error message. Error codes and messages are listed below.         textual error message. Error codes and messages are listed below.
1111    
1112         If  the  final  argument, tableptr, is NULL, PCRE uses a default set of         If the final argument, tableptr, is NULL, PCRE uses a  default  set  of
1113         character tables that are  built  when  PCRE  is  compiled,  using  the         character  tables  that  are  built  when  PCRE  is compiled, using the
1114         default  C  locale.  Otherwise, tableptr must be an address that is the         default C locale. Otherwise, tableptr must be an address  that  is  the
1115         result of a call to pcre_maketables(). This value is  stored  with  the         result  of  a  call to pcre_maketables(). This value is stored with the
1116         compiled  pattern,  and used again by pcre_exec(), unless another table         compiled pattern, and used again by pcre_exec(), unless  another  table
1117         pointer is passed to it. For more discussion, see the section on locale         pointer is passed to it. For more discussion, see the section on locale
1118         support below.         support below.
1119    
1120         This  code  fragment  shows a typical straightforward call to pcre_com-         This code fragment shows a typical straightforward  call  to  pcre_com-
1121         pile():         pile():
1122    
1123           pcre *re;           pcre *re;
# Line 1083  COMPILING A PATTERN Line 1130  COMPILING A PATTERN
1130             &erroffset,       /* for error offset */             &erroffset,       /* for error offset */
1131             NULL);            /* use default character tables */             NULL);            /* use default character tables */
1132    
1133         The following names for option bits are defined in  the  pcre.h  header         The  following  names  for option bits are defined in the pcre.h header
1134         file:         file:
1135    
1136           PCRE_ANCHORED           PCRE_ANCHORED
1137    
1138         If this bit is set, the pattern is forced to be "anchored", that is, it         If this bit is set, the pattern is forced to be "anchored", that is, it
1139         is constrained to match only at the first matching point in the  string         is  constrained to match only at the first matching point in the string
1140         that  is being searched (the "subject string"). This effect can also be         that is being searched (the "subject string"). This effect can also  be
1141         achieved by appropriate constructs in the pattern itself, which is  the         achieved  by appropriate constructs in the pattern itself, which is the
1142         only way to do it in Perl.         only way to do it in Perl.
1143    
1144           PCRE_AUTO_CALLOUT           PCRE_AUTO_CALLOUT
1145    
1146         If this bit is set, pcre_compile() automatically inserts callout items,         If this bit is set, pcre_compile() automatically inserts callout items,
1147         all with number 255, before each pattern item. For  discussion  of  the         all  with  number  255, before each pattern item. For discussion of the
1148         callout facility, see the pcrecallout documentation.         callout facility, see the pcrecallout documentation.
1149    
1150             PCRE_BSR_ANYCRLF
1151             PCRE_BSR_UNICODE
1152    
1153           These options (which are mutually exclusive) control what the \R escape
1154           sequence  matches.  The choice is either to match only CR, LF, or CRLF,
1155           or to match any Unicode newline sequence. The default is specified when
1156           PCRE is built. It can be overridden from within the pattern, or by set-
1157           ting an option when a compiled pattern is matched.
1158    
1159           PCRE_CASELESS           PCRE_CASELESS
1160    
1161         If  this  bit is set, letters in the pattern match both upper and lower         If this bit is set, letters in the pattern match both upper  and  lower
1162         case letters. It is equivalent to Perl's  /i  option,  and  it  can  be         case  letters.  It  is  equivalent  to  Perl's /i option, and it can be
1163         changed  within a pattern by a (?i) option setting. In UTF-8 mode, PCRE         changed within a pattern by a (?i) option setting. In UTF-8 mode,  PCRE
1164         always understands the concept of case for characters whose values  are         always  understands the concept of case for characters whose values are
1165         less  than 128, so caseless matching is always possible. For characters         less than 128, so caseless matching is always possible. For  characters
1166         with higher values, the concept of case is supported if  PCRE  is  com-         with  higher  values,  the concept of case is supported if PCRE is com-
1167         piled  with Unicode property support, but not otherwise. If you want to         piled with Unicode property support, but not otherwise. If you want  to
1168         use caseless matching for characters 128 and  above,  you  must  ensure         use  caseless  matching  for  characters 128 and above, you must ensure
1169         that  PCRE  is  compiled  with Unicode property support as well as with         that PCRE is compiled with Unicode property support  as  well  as  with
1170         UTF-8 support.         UTF-8 support.
1171    
1172           PCRE_DOLLAR_ENDONLY           PCRE_DOLLAR_ENDONLY
1173    
1174         If this bit is set, a dollar metacharacter in the pattern matches  only         If  this bit is set, a dollar metacharacter in the pattern matches only
1175         at  the  end  of the subject string. Without this option, a dollar also         at the end of the subject string. Without this option,  a  dollar  also
1176         matches immediately before a newline at the end of the string (but  not         matches  immediately before a newline at the end of the string (but not
1177         before  any  other newlines). The PCRE_DOLLAR_ENDONLY option is ignored         before any other newlines). The PCRE_DOLLAR_ENDONLY option  is  ignored
1178         if PCRE_MULTILINE is set.  There is no equivalent  to  this  option  in         if  PCRE_MULTILINE  is  set.   There is no equivalent to this option in
1179         Perl, and no way to set it within a pattern.         Perl, and no way to set it within 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    
1194         If this bit is set, names used to identify capturing  subpatterns  need         If  this  bit is set, names used to identify capturing subpatterns need
1195         not be unique. This can be helpful for certain types of pattern when it         not be unique. This can be helpful for certain types of pattern when it
1196         is known that only one instance of the named  subpattern  can  ever  be         is  known  that  only  one instance of the named subpattern can ever be
1197         matched.  There  are  more details of named subpatterns below; see also         matched. There are more details of named subpatterns  below;  see  also
1198         the pcrepattern documentation.         the pcrepattern documentation.
1199    
1200           PCRE_EXTENDED           PCRE_EXTENDED
1201    
1202         If this bit is set, whitespace  data  characters  in  the  pattern  are         If  this  bit  is  set,  whitespace  data characters in the pattern are
1203         totally ignored except when escaped or inside a character class. White-         totally ignored except when escaped or inside a character class. White-
1204         space does not include the VT character (code 11). In addition, charac-         space does not include the VT character (code 11). In addition, charac-
1205         ters between an unescaped # outside a character class and the next new-         ters between an unescaped # outside a character class and the next new-
1206         line, inclusive, are also ignored. This  is  equivalent  to  Perl's  /x         line,  inclusive,  are  also  ignored.  This is equivalent to Perl's /x
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           Which  characters  are  interpreted  as  newlines  is controlled by the
1211           options passed to pcre_compile() or by a special sequence at the  start
1212           of  the  pattern, as described in the section entitled "Newline conven-
1213           tions" in the pcrepattern documentation. Note that the end of this type
1214           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         This option makes it possible to include  comments  inside  complicated
1218         patterns.   Note,  however,  that this applies only to data characters.         patterns.   Note,  however,  that this applies only to data characters.
1219         Whitespace  characters  may  never  appear  within  special   character         Whitespace  characters  may  never  appear  within  special   character
1220         sequences  in  a  pattern,  for  example  within the sequence (?( which         sequences in a pattern, for example within the sequence (?( that intro-
1221         introduces a conditional subpattern.         duces a conditional subpattern.
1222    
1223           PCRE_EXTRA           PCRE_EXTRA
1224    
# Line 1163  COMPILING A PATTERN Line 1228  COMPILING A PATTERN
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    
1238         If this option is set, an  unanchored  pattern  is  required  to  match         If  this  option  is  set,  an  unanchored pattern is required to match
1239         before  or  at  the  first  newline  in  the subject string, though the         before or at the first  newline  in  the  subject  string,  though  the
1240         matched text may continue over the newline.         matched text may continue over the newline.
1241    
1242             PCRE_JAVASCRIPT_COMPAT
1243    
1244           If this option is set, PCRE's behaviour is changed in some ways so that
1245           it is compatible with JavaScript rather than Perl. The changes  are  as
1246           follows:
1247    
1248           (1)  A  lone  closing square bracket in a pattern causes a compile-time
1249           error, because this is illegal in JavaScript (by default it is  treated
1250           as a data character). Thus, the pattern AB]CD becomes illegal when this
1251           option is set.
1252    
1253           (2) At run time, a back reference to an unset subpattern group  matches
1254           an  empty  string (by default this causes the current matching alterna-
1255           tive to fail). A pattern such as (\1)(a) succeeds when this  option  is
1256           set  (assuming  it can find an "a" in the subject), whereas it fails by
1257           default, for Perl compatibility.
1258    
1259           PCRE_MULTILINE           PCRE_MULTILINE
1260    
1261         By default, PCRE treats the subject string as consisting  of  a  single         By default, PCRE treats the subject string as consisting  of  a  single
# Line 1217  COMPILING A PATTERN Line 1300  COMPILING A PATTERN
1300         PCRE_NEWLINE_CRLF,  but other combinations may yield unused numbers and         PCRE_NEWLINE_CRLF,  but other combinations may yield unused numbers and
1301         cause an error.         cause an error.
1302    
1303         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
1304         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
1305         character class is encountered. This indicates  a  comment  that  lasts         characters, and so are ignored in this mode. Also, an unescaped #  out-
1306         until  after the next line break sequence. In other circumstances, line         side  a  character class indicates a comment that lasts until after the
1307         break  sequences  are  treated  as  literal  data,   except   that   in         next line break sequence. In other circumstances, line break  sequences
1308         PCRE_EXTENDED mode, both CR and LF are treated as whitespace characters         in patterns are treated as literal data.
        and are therefore ignored.  
1309    
1310         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
1311         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.
1312    
1313           PCRE_NO_AUTO_CAPTURE           PCRE_NO_AUTO_CAPTURE
1314    
# Line 1236  COMPILING A PATTERN Line 1318  COMPILING A PATTERN
1318         be  used  for  capturing  (and  they acquire numbers in the usual way).         be  used  for  capturing  (and  they acquire numbers in the usual way).
1319         There is no equivalent of this option in Perl.         There is no equivalent of this option in Perl.
1320    
1321             NO_START_OPTIMIZE
1322    
1323           This is an option that acts at matching time; that is, it is really  an
1324           option  for  pcre_exec()  or  pcre_dfa_exec().  If it is set at compile
1325           time, it is remembered with the compiled pattern and assumed at  match-
1326           ing  time.  For  details  see  the discussion of PCRE_NO_START_OPTIMIZE
1327           below.
1328    
1329             PCRE_UCP
1330    
1331           This option changes the way PCRE processes \B, \b, \D, \d, \S, \s,  \W,
1332           \w,  and  some  of  the POSIX character classes. By default, only ASCII
1333           characters are recognized, but if PCRE_UCP is set,  Unicode  properties
1334           are  used instead to classify characters. More details are given in the
1335           section on generic character types in the pcrepattern page. If you  set
1336           PCRE_UCP,  matching  one of the items it affects takes much longer. The
1337           option is available only if PCRE has been compiled with  Unicode  prop-
1338           erty support.
1339    
1340           PCRE_UNGREEDY           PCRE_UNGREEDY
1341    
1342         This option inverts the "greediness" of the quantifiers  so  that  they         This  option  inverts  the "greediness" of the quantifiers so that they
1343         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
1344         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
1345         within the pattern.         within the pattern.
1346    
1347           PCRE_UTF8           PCRE_UTF8
1348    
1349         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
1350         strings of UTF-8 characters instead of single-byte  character  strings.         strings  of  UTF-8 characters instead of single-byte character strings.
1351         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-
1352         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
1353         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
1354         UTF-8 support in the main pcre page.         page.
1355    
1356           PCRE_NO_UTF8_CHECK           PCRE_NO_UTF8_CHECK
1357    
1358         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
1359         automatically  checked.  There  is  a  discussion about the validity of         automatically checked. There is a  discussion  about  the  validity  of
1360         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
1361         bytes  is  found,  pcre_compile() returns an error. If you already know         bytes is found, pcre_compile() returns an error. If  you  already  know
1362         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-
1363         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
1364         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
1365         undefined.  It  may  cause your program to crash. Note that this option         undefined. It may cause your program to crash. Note  that  this  option
1366         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
1367         UTF-8 validity checking of subject strings.         UTF-8 validity checking of subject strings.
1368    
1369    
1370  COMPILATION ERROR CODES  COMPILATION ERROR CODES
1371    
1372         The  following  table  lists  the  error  codes than may be returned by         The following table lists the error  codes  than  may  be  returned  by
1373         pcre_compile2(), along with the error messages that may be returned  by         pcre_compile2(),  along with the error messages that may be returned by
1374         both  compiling functions. As PCRE has developed, some error codes have         both compiling functions. As PCRE has developed, some error codes  have
1375         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.
1376    
1377            0  no error            0  no error
# Line 1285  COMPILATION ERROR CODES Line 1386  COMPILATION ERROR CODES
1386            9  nothing to repeat            9  nothing to repeat
1387           10  [this code is not in use]           10  [this code is not in use]
1388           11  internal error: unexpected repeat           11  internal error: unexpected repeat
1389           12  unrecognized character after (?           12  unrecognized character after (? or (?-
1390           13  POSIX named classes are supported only within a class           13  POSIX named classes are supported only within a class
1391           14  missing )           14  missing )
1392           15  reference to non-existent subpattern           15  reference to non-existent subpattern
# Line 1293  COMPILATION ERROR CODES Line 1394  COMPILATION ERROR CODES
1394           17  unknown option bit(s) set           17  unknown option bit(s) set
1395           18  missing ) after comment           18  missing ) after comment
1396           19  [this code is not in use]           19  [this code is not in use]
1397           20  regular expression too large           20  regular expression is too large
1398           21  failed to get memory           21  failed to get memory
1399           22  unmatched parentheses           22  unmatched parentheses
1400           23  internal error: code overflow           23  internal error: code overflow
# Line 1310  COMPILATION ERROR CODES Line 1411  COMPILATION ERROR CODES
1411           34  character value in \x{...} sequence is too large           34  character value in \x{...} sequence is too large
1412           35  invalid condition (?(0)           35  invalid condition (?(0)
1413           36  \C not allowed in lookbehind assertion           36  \C not allowed in lookbehind assertion
1414           37  PCRE does not support \L, \l, \N, \U, or \u           37  PCRE does not support \L, \l, \N{name}, \U, or \u
1415           38  number after (?C is > 255           38  number after (?C is > 255
1416           39  closing ) for (?C expected           39  closing ) for (?C expected
1417           40  recursive call could loop indefinitely           40  recursive call could loop indefinitely
# Line 1322  COMPILATION ERROR CODES Line 1423  COMPILATION ERROR CODES
1423           46  malformed \P or \p sequence           46  malformed \P or \p sequence
1424           47  unknown property name after \P or \p           47  unknown property name after \P or \p
1425           48  subpattern name is too long (maximum 32 characters)           48  subpattern name is too long (maximum 32 characters)
1426           49  too many named subpatterns (maximum 10,000)           49  too many named subpatterns (maximum 10000)
1427           50  [this code is not in use]           50  [this code is not in use]
1428           51  octal value is greater than \377 (not in UTF-8 mode)           51  octal value is greater than \377 (not in UTF-8 mode)
1429           52  internal error: overran compiling workspace           52  internal error: overran compiling workspace
1430           53  internal  error:  previously-checked  referenced  subpattern  not           53  internal error: previously-checked referenced subpattern
1431         found                 not found
1432           54  DEFINE group contains more than one branch           54  DEFINE group contains more than one branch
1433           55  repeating a DEFINE group is not allowed           55  repeating a DEFINE group is not allowed
1434           56  inconsistent NEWLINE options"           56  inconsistent NEWLINE options
1435           57  \g is not followed by a braced name or an optionally braced           57  \g is not followed by a braced, angle-bracketed, or quoted
1436                 non-zero number                 name/number or by a plain number
1437           58  (?+ or (?- or (?(+ or (?(- must be followed by a non-zero number           58  a numbered reference must not be zero
1438             59  an argument is not allowed for (*ACCEPT), (*FAIL), or (*COMMIT)
1439             60  (*VERB) not recognized
1440             61  number is too big
1441             62  subpattern name expected
1442             63  digit expected after (?+
1443             64  ] is an invalid data character in JavaScript compatibility mode
1444             65  different names for subpatterns of the same number are
1445                   not allowed
1446             66  (*MARK) must have an argument
1447             67  this version of PCRE is not compiled with PCRE_UCP support
1448             68  \c must be followed by an ASCII character
1449             69  \k is not followed by a braced, angle-bracketed, or quoted name
1450    
1451           The  numbers  32  and 10000 in errors 48 and 49 are defaults; different
1452           values may be used if the limits were changed when PCRE was built.
1453    
1454    
1455  STUDYING A PATTERN  STUDYING A PATTERN
# Line 1341  STUDYING A PATTERN Line 1457  STUDYING A PATTERN
1457         pcre_extra *pcre_study(const pcre *code, int options         pcre_extra *pcre_study(const pcre *code, int options
1458              const char **errptr);              const char **errptr);
1459    
1460         If  a  compiled  pattern is going to be used several times, it is worth         If a compiled pattern is going to be used several times,  it  is  worth
1461         spending more time analyzing it in order to speed up the time taken for         spending more time analyzing it in order to speed up the time taken for
1462         matching.  The function pcre_study() takes a pointer to a compiled pat-         matching. The function pcre_study() takes a pointer to a compiled  pat-
1463         tern as its first argument. If studying the pattern produces additional         tern as its first argument. If studying the pattern produces additional
1464         information  that  will  help speed up matching, pcre_study() returns a         information that will help speed up matching,  pcre_study()  returns  a
1465         pointer to a pcre_extra block, in which the study_data field points  to         pointer  to a pcre_extra block, in which the study_data field points to
1466         the results of the study.         the results of the study.
1467    
1468         The  returned  value  from  pcre_study()  can  be  passed  directly  to         The  returned  value  from  pcre_study()  can  be  passed  directly  to
1469         pcre_exec(). However, a pcre_extra block  also  contains  other  fields         pcre_exec()  or  pcre_dfa_exec(). However, a pcre_extra block also con-
1470         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
1471         described below in the section on matching a pattern.         passed; these are described below in the section on matching a pattern.
1472    
1473         If studying the pattern does not  produce  any  additional  information         If  studying  the  pattern  does  not  produce  any useful information,
1474         pcre_study() returns NULL. In that circumstance, if the calling program         pcre_study() returns NULL. In that circumstance, if the calling program
1475         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
1476         its own pcre_extra block.         pcre_dfa_exec(), it must set up its own pcre_extra block.
1477    
1478         The  second  argument of pcre_study() contains option bits. At present,         The second argument of pcre_study() contains option bits. There is only
1479         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-
1480           time compiler is  available,  the  pattern  is  further  compiled  into
1481           machine  code  that  executes much faster than the pcre_exec() matching
1482           function. If the just-in-time compiler is not available, this option is
1483           ignored. All other bits in the options argument must be zero.
1484    
1485           JIT  compilation  is  a heavyweight optimization. It can take some time
1486           for patterns to be analyzed, and for one-off matches  and  simple  pat-
1487           terns  the benefit of faster execution might be offset by a much slower
1488           study time.  Not all patterns can be optimized by the JIT compiler. For
1489           those  that cannot be handled, matching automatically falls back to the
1490           pcre_exec() interpreter. For more details, see the  pcrejit  documenta-
1491           tion.
1492    
1493         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.
1494         If  studying  succeeds  (even  if no data is returned), the variable it         If studying succeeds (even if no data is  returned),  the  variable  it
1495         points to is set to NULL. Otherwise it is set to  point  to  a  textual         points  to  is  set  to NULL. Otherwise it is set to point to a textual
1496         error message. This is a static string that is part of the library. You         error message. This is a static string that is part of the library. You
1497         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
1498         after calling pcre_study(), to be sure that it has run successfully.         after calling pcre_study(), to be sure that it has run successfully.
1499    
1500         This is a typical call to pcre_study():         When you are finished with a pattern, you can free the memory used  for
1501           the study data by calling pcre_free_study(). This function was added to
1502           the API for release 8.20. For earlier versions,  the  memory  could  be
1503           freed  with  pcre_free(), just like the pattern itself. This will still
1504           work in cases where PCRE_STUDY_JIT_COMPILE  is  not  used,  but  it  is
1505           advisable to change to the new function when convenient.
1506    
1507           This  is  a typical way in which pcre_study() is used (except that in a
1508           real application there should be tests for errors):
1509    
1510           pcre_extra *pe;           int rc;
1511           pe = pcre_study(           pcre *re;
1512             pcre_extra *sd;
1513             re = pcre_compile("pattern", 0, &error, &erroroffset, NULL);
1514             sd = pcre_study(
1515             re,             /* result of pcre_compile() */             re,             /* result of pcre_compile() */
1516             0,              /* no options exist */             0,              /* no options */
1517             &error);        /* set to NULL or points to a message */             &error);        /* set to NULL or points to a message */
1518             rc = pcre_exec(   /* see below for details of pcre_exec() options */
1519         At present, studying a pattern is useful only for non-anchored patterns             re, sd, "subject", 7, 0, 0, ovector, 30);
1520         that do not have a single fixed starting character. A bitmap of  possi-           ...
1521         ble starting bytes is created.           pcre_free_study(sd);
1522             pcre_free(re);
1523    
1524           Studying a pattern does two things: first, a lower bound for the length
1525           of subject string that is needed to match the pattern is computed. This
1526           does not mean that there are any strings of that length that match, but
1527           it  does  guarantee that no shorter strings match. The value is used by
1528           pcre_exec() and pcre_dfa_exec() to avoid  wasting  time  by  trying  to
1529           match  strings  that are shorter than the lower bound. You can find out
1530           the value in a calling program via the pcre_fullinfo() function.
1531    
1532           Studying a pattern is also useful for non-anchored patterns that do not
1533           have  a  single fixed starting character. A bitmap of possible starting
1534           bytes is created. This speeds up finding a position in the  subject  at
1535           which to start matching.
1536    
1537           These  two optimizations apply to both pcre_exec() and pcre_dfa_exec().
1538           However, they are not used by pcre_exec()  if  pcre_study()  is  called
1539           with  the  PCRE_STUDY_JIT_COMPILE option, and just-in-time compiling is
1540           successful.  The  optimizations  can  be  disabled   by   setting   the
1541           PCRE_NO_START_OPTIMIZE    option    when    calling    pcre_exec()   or
1542           pcre_dfa_exec(). You might want to do this  if  your  pattern  contains
1543           callouts  or (*MARK) (which cannot be handled by the JIT compiler), and
1544           you want to make use of these facilities in cases where matching fails.
1545           See the discussion of PCRE_NO_START_OPTIMIZE below.
1546    
1547    
1548  LOCALE SUPPORT  LOCALE SUPPORT
# Line 1387  LOCALE SUPPORT Line 1550  LOCALE SUPPORT
1550         PCRE  handles  caseless matching, and determines whether characters are         PCRE  handles  caseless matching, and determines whether characters are
1551         letters, digits, or whatever, by reference to a set of tables,  indexed         letters, digits, or whatever, by reference to a set of tables,  indexed
1552         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
1553         characters with codes less than 128. Higher-valued  codes  never  match         characters with codes less than 128. By  default,  higher-valued  codes
1554         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
1555         with Unicode character property support. The use of locales  with  Uni-         PCRE is built with Unicode character property  support.  Alternatively,
1556         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
1557         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
1558         not try to mix the two.         use of locales with Unicode is discouraged. If you are handling charac-
1559           ters with codes greater than 128, you should either use UTF-8 and  Uni-
1560           code, or use locales, but not try to mix the two.
1561    
1562         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
1563         argument of pcre_compile() is  NULL.  These  are  sufficient  for  many         argument of pcre_compile() is  NULL.  These  are  sufficient  for  many
# Line 1468  INFORMATION ABOUT A PATTERN Line 1633  INFORMATION ABOUT A PATTERN
1633           size_t length;           size_t length;
1634           rc = pcre_fullinfo(           rc = pcre_fullinfo(
1635             re,               /* result of pcre_compile() */             re,               /* result of pcre_compile() */
1636             pe,               /* result of pcre_study(), or NULL */             sd,               /* result of pcre_study(), or NULL */
1637             PCRE_INFO_SIZE,   /* what is required */             PCRE_INFO_SIZE,   /* what is required */
1638             &length);         /* where to put the data */             &length);         /* where to put the data */
1639    
# Line 1522  INFORMATION ABOUT A PATTERN Line 1687  INFORMATION ABOUT A PATTERN
1687         returned.  The fourth argument should point to an unsigned char * vari-         returned.  The fourth argument should point to an unsigned char * vari-
1688         able.         able.
1689    
1690             PCRE_INFO_HASCRORLF
1691    
1692           Return 1 if the pattern contains any explicit  matches  for  CR  or  LF
1693           characters,  otherwise  0.  The  fourth argument should point to an int
1694           variable. An explicit match is either a literal CR or LF character,  or
1695           \r or \n.
1696    
1697           PCRE_INFO_JCHANGED           PCRE_INFO_JCHANGED
1698    
1699         Return 1 if the (?J) option setting is used in the  pattern,  otherwise         Return  1  if  the (?J) or (?-J) option setting is used in the pattern,
1700         0. The fourth argument should point to an int variable. The (?J) inter-         otherwise 0. The fourth argument should point to an int variable.  (?J)
1701         nal option setting changes the local PCRE_DUPNAMES option.         and (?-J) set and unset the local PCRE_DUPNAMES option, respectively.
1702    
1703             PCRE_INFO_JIT
1704    
1705           Return  1  if  the  pattern was studied with the PCRE_STUDY_JIT_COMPILE
1706           option, and just-in-time compiling was successful. The fourth  argument
1707           should  point  to  an  int variable. A return value of 0 means that JIT
1708           support is not available in this version of PCRE, or that  the  pattern
1709           was not studied with the PCRE_STUDY_JIT_COMPILE option, or that the JIT
1710           compiler could not handle this particular pattern. See the pcrejit doc-
1711           umentation for details of what can and cannot be handled.
1712    
1713           PCRE_INFO_LASTLITERAL           PCRE_INFO_LASTLITERAL
1714    
1715         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
1716         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
1717         recorded. The fourth argument should point to an int variable. If there         recorded. The fourth argument should point to an int variable. If there
1718         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
1719         byte is recorded only if it follows something of variable  length.  For         byte  is  recorded only if it follows something of variable length. For
1720         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
1721         /^a\dz\d/ the returned value is -1.         /^a\dz\d/ the returned value is -1.
1722    
1723             PCRE_INFO_MINLENGTH
1724    
1725           If  the  pattern  was studied and a minimum length for matching subject
1726           strings was computed, its value is  returned.  Otherwise  the  returned
1727           value  is  -1. The value is a number of characters, not bytes (this may
1728           be relevant in UTF-8 mode). The fourth argument should point to an  int
1729           variable.  A  non-negative  value is a lower bound to the length of any
1730           matching string. There may not be any strings of that  length  that  do
1731           actually match, but every string that does match is at least that long.
1732    
1733           PCRE_INFO_NAMECOUNT           PCRE_INFO_NAMECOUNT
1734           PCRE_INFO_NAMEENTRYSIZE           PCRE_INFO_NAMEENTRYSIZE
1735           PCRE_INFO_NAMETABLE           PCRE_INFO_NAMETABLE
1736    
1737         PCRE supports the use of named as well as numbered capturing  parenthe-         PCRE  supports the use of named as well as numbered capturing parenthe-
1738         ses.  The names are just an additional way of identifying the parenthe-         ses. The names are just an additional way of identifying the  parenthe-
1739         ses, which still acquire numbers. Several convenience functions such as         ses, which still acquire numbers. Several convenience functions such as
1740         pcre_get_named_substring()  are  provided  for extracting captured sub-         pcre_get_named_substring() are provided for  extracting  captured  sub-
1741         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
1742         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
1743         pointers in the output vector (described with pcre_exec() below). To do         pointers in the output vector (described with pcre_exec() below). To do
1744         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
1745         described by these three values.         described by these three values.
1746    
1747         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
1748         gives the number of entries, and PCRE_INFO_NAMEENTRYSIZE gives the size         gives the number of entries, and PCRE_INFO_NAMEENTRYSIZE gives the size
1749         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
1750         depends  on the length of the longest name. PCRE_INFO_NAMETABLE returns         depends on the length of the longest name. PCRE_INFO_NAMETABLE  returns
1751         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
1752         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-
1753         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-
1754         sponding  name,  zero  terminated. The names are in alphabetical order.         sponding name, zero terminated.
1755         When PCRE_DUPNAMES is set, duplicate names are in order of their paren-  
1756         theses  numbers.  For  example,  consider the following pattern (assume         The names are in alphabetical order. Duplicate names may appear if  (?|
1757         PCRE_EXTENDED is  set,  so  white  space  -  including  newlines  -  is         is used to create multiple groups with the same number, as described in
1758         ignored):         the section on duplicate subpattern numbers in  the  pcrepattern  page.
1759           Duplicate  names  for  subpatterns with different numbers are permitted
1760           only if PCRE_DUPNAMES is set. In all cases  of  duplicate  names,  they
1761           appear  in  the table in the order in which they were found in the pat-
1762           tern. In the absence of (?| this is the  order  of  increasing  number;
1763           when (?| is used this is not necessarily the case because later subpat-
1764           terns may have lower numbers.
1765    
1766           As a simple example of the name/number table,  consider  the  following
1767           pattern  (assume  PCRE_EXTENDED is set, so white space - including new-
1768           lines - is ignored):
1769    
1770           (?<date> (?<year>(\d\d)?\d\d) -           (?<date> (?<year>(\d\d)?\d\d) -
1771           (?<month>\d\d) - (?<day>\d\d) )           (?<month>\d\d) - (?<day>\d\d) )
1772    
1773         There  are  four  named subpatterns, so the table has four entries, and         There are four named subpatterns, so the table has  four  entries,  and
1774         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,
1775         with non-printing bytes shows in hexadecimal, and undefined bytes shown         with non-printing bytes shows in hexadecimal, and undefined bytes shown
1776         as ??:         as ??:
1777    
# Line 1578  INFORMATION ABOUT A PATTERN Line 1780  INFORMATION ABOUT A PATTERN
1780           00 04 m  o  n  t  h  00           00 04 m  o  n  t  h  00
1781           00 02 y  e  a  r  00 ??           00 02 y  e  a  r  00 ??
1782    
1783         When writing code to extract data  from  named  subpatterns  using  the         When  writing  code  to  extract  data from named subpatterns using the
1784         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
1785         to be different for each compiled pattern.         to be different for each compiled pattern.
1786    
1787           PCRE_INFO_OKPARTIAL           PCRE_INFO_OKPARTIAL
1788    
1789         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
1790         The  fourth  argument  should point to an int variable. The pcrepartial         pcre_exec(), otherwise 0. The fourth argument should point  to  an  int
1791         documentation lists the restrictions that apply to patterns  when  par-         variable.  From  release  8.00,  this  always  returns  1,  because the
1792         tial matching is used.         restrictions that previously applied  to  partial  matching  have  been
1793           lifted.  The  pcrepartial documentation gives details of partial match-
1794           ing.
1795    
1796           PCRE_INFO_OPTIONS           PCRE_INFO_OPTIONS
1797    
1798         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
1799         fourth argument should point to an unsigned long  int  variable.  These         fourth  argument  should  point to an unsigned long int variable. These
1800         option bits are those specified in the call to pcre_compile(), modified         option bits are those specified in the call to pcre_compile(), modified
1801         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
1802         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
1803         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
1804         the  PCRE_EXTENDED option, the result is PCRE_CASELESS, PCRE_MULTILINE,         the PCRE_EXTENDED option, the result is PCRE_CASELESS,  PCRE_MULTILINE,
1805         and PCRE_EXTENDED.         and PCRE_EXTENDED.
1806    
1807         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
1808         alternatives begin with one of the following:         alternatives begin with one of the following:
1809    
1810           ^     unless PCRE_MULTILINE is set           ^     unless PCRE_MULTILINE is set
# Line 1614  INFORMATION ABOUT A PATTERN Line 1818  INFORMATION ABOUT A PATTERN
1818    
1819           PCRE_INFO_SIZE           PCRE_INFO_SIZE
1820    
1821         Return the size of the compiled pattern, that is, the  value  that  was         Return  the  size  of the compiled pattern, that is, the value that was
1822         passed as the argument to pcre_malloc() when PCRE was getting memory in         passed as the argument to pcre_malloc() when PCRE was getting memory in
1823         which to place the compiled data. The fourth argument should point to a         which to place the compiled data. The fourth argument should point to a
1824         size_t variable.         size_t variable.
# Line 1622  INFORMATION ABOUT A PATTERN Line 1826  INFORMATION ABOUT A PATTERN
1826           PCRE_INFO_STUDYSIZE           PCRE_INFO_STUDYSIZE
1827    
1828         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
1829         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,
1830         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-
1831         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-
1832         variable.         tion that will speed up matching (see the section entitled "Studying  a
1833           pattern" above). The format of the study_data block is private, but its
1834           length is made available via this option so that it can  be  saved  and
1835           restored (see the pcreprecompile documentation for details).
1836    
1837    
1838  OBSOLETE INFO FUNCTION  OBSOLETE INFO FUNCTION
# Line 1678  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 1885  MATCHING A PATTERN: THE TRADITIONAL FUNC
1885              const char *subject, int length, int startoffset,              const char *subject, int length, int startoffset,
1886              int options, int *ovector, int ovecsize);              int options, int *ovector, int ovecsize);
1887    
1888         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
1889         compiled pattern, which is passed in the code argument. If the  pattern         compiled  pattern, which is passed in the code argument. If the pattern
1890         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
1891         argument. This function is the main matching facility of  the  library,         argument.  This  function is the main matching facility of the library,
1892         and it operates in a Perl-like manner. For specialist use there is also         and it operates in a Perl-like manner. For specialist use there is also
1893         an alternative matching function, which is described below in the  sec-         an  alternative matching function, which is described below in the sec-
1894         tion about the pcre_dfa_exec() function.         tion about the pcre_dfa_exec() function.
1895    
1896         In  most applications, the pattern will have been compiled (and option-         In most applications, the pattern will have been compiled (and  option-
1897         ally studied) in the same process that calls pcre_exec().  However,  it         ally  studied)  in the same process that calls pcre_exec(). However, it
1898         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
1899         later in different processes, possibly even on different hosts.  For  a         later  in  different processes, possibly even on different hosts. For a
1900         discussion about this, see the pcreprecompile documentation.         discussion about this, see the pcreprecompile documentation.
1901    
1902         Here is an example of a simple call to pcre_exec():         Here is an example of a simple call to pcre_exec():
# Line 1708  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 1915  MATCHING A PATTERN: THE TRADITIONAL FUNC
1915    
1916     Extra data for pcre_exec()     Extra data for pcre_exec()
1917    
1918         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
1919         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
1920         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-
1921         tional information in it. The pcre_extra block contains  the  following         tional  information  in it. The pcre_extra block contains the following
1922         fields (not necessarily in this order):         fields (not necessarily in this order):
1923    
1924           unsigned long int flags;           unsigned long int flags;
1925           void *study_data;           void *study_data;
1926             void *executable_jit;
1927           unsigned long int match_limit;           unsigned long int match_limit;
1928           unsigned long int match_limit_recursion;           unsigned long int match_limit_recursion;
1929           void *callout_data;           void *callout_data;
1930           const unsigned char *tables;           const unsigned char *tables;
1931             unsigned char **mark;
1932    
1933         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
1934         are set. The flag bits are:         are set. The flag bits are:
1935    
1936           PCRE_EXTRA_STUDY_DATA           PCRE_EXTRA_STUDY_DATA
1937             PCRE_EXTRA_EXECUTABLE_JIT
1938           PCRE_EXTRA_MATCH_LIMIT           PCRE_EXTRA_MATCH_LIMIT
1939           PCRE_EXTRA_MATCH_LIMIT_RECURSION           PCRE_EXTRA_MATCH_LIMIT_RECURSION
1940           PCRE_EXTRA_CALLOUT_DATA           PCRE_EXTRA_CALLOUT_DATA
1941           PCRE_EXTRA_TABLES           PCRE_EXTRA_TABLES
1942             PCRE_EXTRA_MARK
1943    
1944         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-
1945         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
1946         the appropriate flag bit. You should not set this yourself, but you may         returned  by pcre_study(), together with the appropriate flag bits. You
1947         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
1948         flag bits.         the other fields and their corresponding flag bits.
1949    
1950         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
1951         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
1952         match, but which have a very large number  of  possibilities  in  their         match,  but  which  have  a very large number of possibilities in their
1953         search  trees.  The  classic  example  is  the  use of nested unlimited         search trees. The classic example is a pattern that uses nested  unlim-
1954         repeats.         ited repeats.
1955    
1956         Internally, PCRE uses a function called match() which it calls  repeat-         Internally,  pcre_exec() uses a function called match(), which it calls
1957         edly  (sometimes  recursively). The limit set by match_limit is imposed         repeatedly (sometimes recursively). The limit  set  by  match_limit  is
1958         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,
1959         has  the  effect  of  limiting the amount of backtracking that can take         which has the effect of limiting the amount of  backtracking  that  can
1960         place. For patterns that are not anchored, the count restarts from zero         take place. For patterns that are not anchored, the count restarts from
1961         for each position in the subject string.         zero for each position in the subject string.
1962    
1963           When pcre_exec() is called with a pattern that was successfully studied
1964           with  the  PCRE_STUDY_JIT_COMPILE  option, the way that the matching is
1965           executed is entirely different. However, there is still the possibility
1966           of  runaway  matching  that  goes  on  for a very long time, and so the
1967           match_limit value is also used in this case (but in a different way) to
1968           limit how long the matching can continue.
1969    
1970         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
1971         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 1762  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 1980  MATCHING A PATTERN: THE TRADITIONAL FUNC
1980         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-
1981         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.
1982    
1983         Limiting  the  recursion  depth  limits the amount of stack that can be         Limiting the recursion depth limits the amount of  machine  stack  that
1984         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
1985         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
1986           limit  is not relevant, and is ignored, if the pattern was successfully
1987         The  default  value  for  match_limit_recursion can be set when PCRE is         studied with PCRE_STUDY_JIT_COMPILE.
1988         built; the default default  is  the  same  value  as  the  default  for  
1989         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
1990         a  pcre_extra  block  in  which  match_limit_recursion  is   set,   and         built;  the  default  default  is  the  same  value  as the default for
1991         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
1992           a   pcre_extra   block  in  which  match_limit_recursion  is  set,  and
1993           PCRE_EXTRA_MATCH_LIMIT_RECURSION is set in  the  flags  field.  If  the
1994         limit is exceeded, pcre_exec() returns PCRE_ERROR_RECURSIONLIMIT.         limit is exceeded, pcre_exec() returns PCRE_ERROR_RECURSIONLIMIT.
1995    
1996         The pcre_callout field is used in conjunction with the  "callout"  fea-         The  callout_data  field is used in conjunction with the "callout" fea-
1997         ture, which is described in the pcrecallout documentation.         ture, and is described in the pcrecallout documentation.
1998    
1999         The  tables  field  is  used  to  pass  a  character  tables pointer to         The tables field  is  used  to  pass  a  character  tables  pointer  to
2000         pcre_exec(); this overrides the value that is stored with the  compiled         pcre_exec();  this overrides the value that is stored with the compiled
2001         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
2002         custom tables were supplied to pcre_compile() via  its  tableptr  argu-         custom  tables  were  supplied to pcre_compile() via its tableptr argu-
2003         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
2004         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-
2005         using  patterns  that  have been saved after compiling with an external         using patterns that have been saved after compiling  with  an  external
2006         set of tables, because the external tables  might  be  at  a  different         set  of  tables,  because  the  external tables might be at a different
2007         address  when  pcre_exec() is called. See the pcreprecompile documenta-         address when pcre_exec() is called. See the  pcreprecompile  documenta-
2008         tion for a discussion of saving compiled patterns for later use.         tion for a discussion of saving compiled patterns for later use.
2009    
2010           If  PCRE_EXTRA_MARK  is  set in the flags field, the mark field must be
2011           set to point to a char * variable. If the pattern  contains  any  back-
2012           tracking  control verbs such as (*MARK:NAME), and the execution ends up
2013           with a name to pass back, a pointer to the  name  string  (zero  termi-
2014           nated)  is  placed  in  the  variable pointed to by the mark field. The
2015           names are within the compiled pattern; if you wish  to  retain  such  a
2016           name  you must copy it before freeing the memory of a compiled pattern.
2017           If there is no name to pass back, the variable pointed to by  the  mark
2018           field  set  to NULL. For details of the backtracking control verbs, see
2019           the section entitled "Backtracking control" in the pcrepattern documen-
2020           tation.
2021    
2022     Option bits for pcre_exec()     Option bits for pcre_exec()
2023    
2024         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.
2025         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,
2026         PCRE_NOTBOL,   PCRE_NOTEOL,   PCRE_NOTEMPTY,   PCRE_NO_UTF8_CHECK   and         PCRE_NOTBOL,    PCRE_NOTEOL,    PCRE_NOTEMPTY,   PCRE_NOTEMPTY_ATSTART,
2027         PCRE_PARTIAL.         PCRE_NO_START_OPTIMIZE,  PCRE_NO_UTF8_CHECK,   PCRE_PARTIAL_SOFT,   and
2028           PCRE_PARTIAL_HARD.
2029    
2030           If the pattern was successfully studied with the PCRE_STUDY_JIT_COMPILE
2031           option,  the   only   supported   options   for   JIT   execution   are
2032           PCRE_NO_UTF8_CHECK,   PCRE_NOTBOL,   PCRE_NOTEOL,   PCRE_NOTEMPTY,  and
2033           PCRE_NOTEMPTY_ATSTART. Note in particular that partial matching is  not
2034           supported.  If an unsupported option is used, JIT execution is disabled
2035           and the normal interpretive code in pcre_exec() is run.
2036    
2037           PCRE_ANCHORED           PCRE_ANCHORED
2038    
2039         The  PCRE_ANCHORED  option  limits pcre_exec() to matching at the first         The PCRE_ANCHORED option limits pcre_exec() to matching  at  the  first
2040         matching position. If a pattern was  compiled  with  PCRE_ANCHORED,  or         matching  position.  If  a  pattern was compiled with PCRE_ANCHORED, or
2041         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
2042         unachored at matching time.         unachored at matching time.
2043    
2044             PCRE_BSR_ANYCRLF
2045             PCRE_BSR_UNICODE
2046    
2047           These options (which are mutually exclusive) control what the \R escape
2048           sequence matches. The choice is either to match only CR, LF,  or  CRLF,
2049           or  to  match  any Unicode newline sequence. These options override the
2050           choice that was made or defaulted when the pattern was compiled.
2051    
2052           PCRE_NEWLINE_CR           PCRE_NEWLINE_CR
2053           PCRE_NEWLINE_LF           PCRE_NEWLINE_LF
2054           PCRE_NEWLINE_CRLF           PCRE_NEWLINE_CRLF
# Line 1812  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 2060  MATCHING A PATTERN: THE TRADITIONAL FUNC
2060         tion of pcre_compile()  above.  During  matching,  the  newline  choice         tion of pcre_compile()  above.  During  matching,  the  newline  choice
2061         affects  the  behaviour  of the dot, circumflex, and dollar metacharac-         affects  the  behaviour  of the dot, circumflex, and dollar metacharac-
2062         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
2063         match  failure  for  an  unanchored  pattern.  When  PCRE_NEWLINE_CRLF,         match failure for an unanchored pattern.
2064         PCRE_NEWLINE_ANYCRLF, or PCRE_NEWLINE_ANY is set, and a  match  attempt  
2065         fails  when the current position is at a CRLF sequence, the match posi-         When  PCRE_NEWLINE_CRLF,  PCRE_NEWLINE_ANYCRLF,  or PCRE_NEWLINE_ANY is
2066         tion is advanced by two characters instead of one, in other  words,  to         set, and a match attempt for an unanchored pattern fails when the  cur-
2067         after the CRLF.         rent  position  is  at  a  CRLF  sequence,  and the pattern contains no
2068           explicit matches for  CR  or  LF  characters,  the  match  position  is
2069           advanced by two characters instead of one, in other words, to after the
2070           CRLF.
2071    
2072           The above rule is a compromise that makes the most common cases work as
2073           expected.  For  example,  if  the  pattern  is .+A (and the PCRE_DOTALL
2074           option is not set), it does not match the string "\r\nA" because, after
2075           failing  at the start, it skips both the CR and the LF before retrying.
2076           However, the pattern [\r\n]A does match that string,  because  it  con-
2077           tains an explicit CR or LF reference, and so advances only by one char-
2078           acter after the first failure.
2079    
2080           An explicit match for CR of LF is either a literal appearance of one of
2081           those  characters,  or  one  of the \r or \n escape sequences. Implicit
2082           matches such as [^X] do not count, nor does \s (which includes  CR  and
2083           LF in the characters that it matches).
2084    
2085           Notwithstanding  the above, anomalous effects may still occur when CRLF
2086           is a valid newline sequence and explicit \r or \n escapes appear in the
2087           pattern.
2088    
2089           PCRE_NOTBOL           PCRE_NOTBOL
2090    
# Line 1844  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 2112  MATCHING A PATTERN: THE TRADITIONAL FUNC
2112    
2113           a?b?           a?b?
2114    
2115         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
2116         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
2117         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-
2118         rences of "a" or "b".         rences of "a" or "b".
2119    
2120         Perl has no direct equivalent of PCRE_NOTEMPTY, but it does make a spe-           PCRE_NOTEMPTY_ATSTART
2121         cial  case  of  a  pattern match of the empty string within its split()  
2122         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
2123         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
2124         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.
2125         if  that  fails by advancing the starting offset (see below) and trying  
2126         an ordinary match again. There is some code that demonstrates how to do         Perl    has    no    direct    equivalent    of    PCRE_NOTEMPTY     or
2127         this in the pcredemo.c sample program.         PCRE_NOTEMPTY_ATSTART,  but  it  does  make a special case of a pattern
2128           match of the empty string within its split() function, and  when  using
2129           the  /g  modifier.  It  is  possible  to emulate Perl's behaviour after
2130           matching a null string by first trying the match again at the same off-
2131           set  with  PCRE_NOTEMPTY_ATSTART  and  PCRE_ANCHORED,  and then if that
2132           fails, by advancing the starting offset (see below) and trying an ordi-
2133           nary  match  again. There is some code that demonstrates how to do this
2134           in the pcredemo sample program. In the most general case, you  have  to
2135           check  to  see  if the newline convention recognizes CRLF as a newline,
2136           and if so, and the current character is CR followed by LF, advance  the
2137           starting offset by two characters instead of one.
2138    
2139             PCRE_NO_START_OPTIMIZE
2140    
2141           There  are a number of optimizations that pcre_exec() uses at the start
2142           of a match, in order to speed up the process. For  example,  if  it  is
2143           known that an unanchored match must start with a specific character, it
2144           searches the subject for that character, and fails  immediately  if  it
2145           cannot  find  it,  without actually running the main matching function.
2146           This means that a special item such as (*COMMIT) at the start of a pat-
2147           tern  is  not  considered until after a suitable starting point for the
2148           match has been found. When callouts or (*MARK) items are in use,  these
2149           "start-up" optimizations can cause them to be skipped if the pattern is
2150           never actually used. The start-up optimizations are in  effect  a  pre-
2151           scan of the subject that takes place before the pattern is run.
2152    
2153           The  PCRE_NO_START_OPTIMIZE option disables the start-up optimizations,
2154           possibly causing performance to suffer,  but  ensuring  that  in  cases
2155           where  the  result is "no match", the callouts do occur, and that items
2156           such as (*COMMIT) and (*MARK) are considered at every possible starting
2157           position  in  the  subject  string. If PCRE_NO_START_OPTIMIZE is set at
2158           compile time, it cannot be unset at matching time.
2159    
2160           Setting PCRE_NO_START_OPTIMIZE can change the  outcome  of  a  matching
2161           operation.  Consider the pattern
2162    
2163             (*COMMIT)ABC
2164    
2165           When  this  is  compiled, PCRE records the fact that a match must start
2166           with the character "A". Suppose the subject  string  is  "DEFABC".  The
2167           start-up  optimization  scans along the subject, finds "A" and runs the
2168           first match attempt from there. The (*COMMIT) item means that the  pat-
2169           tern  must  match the current starting position, which in this case, it
2170           does. However, if the same match  is  run  with  PCRE_NO_START_OPTIMIZE
2171           set,  the  initial  scan  along the subject string does not happen. The
2172           first match attempt is run starting  from  "D"  and  when  this  fails,
2173           (*COMMIT)  prevents  any  further  matches  being tried, so the overall
2174           result is "no match". If the pattern is studied,  more  start-up  opti-
2175           mizations  may  be  used. For example, a minimum length for the subject
2176           may be recorded. Consider the pattern
2177    
2178             (*MARK:A)(X|Y)
2179    
2180           The minimum length for a match is one  character.  If  the  subject  is
2181           "ABC",  there  will  be  attempts  to  match "ABC", "BC", "C", and then
2182           finally an empty string.  If the pattern is studied, the final  attempt
2183           does  not take place, because PCRE knows that the subject is too short,
2184           and so the (*MARK) is never encountered.  In this  case,  studying  the
2185           pattern  does  not  affect the overall match result, which is still "no
2186           match", but it does affect the auxiliary information that is returned.
2187    
2188           PCRE_NO_UTF8_CHECK           PCRE_NO_UTF8_CHECK
2189    
2190         When PCRE_UTF8 is set at compile time, the validity of the subject as a         When PCRE_UTF8 is set at compile time, the validity of the subject as a
2191         UTF-8 string is automatically checked when pcre_exec() is  subsequently         UTF-8  string is automatically checked when pcre_exec() is subsequently
2192         called.   The  value  of  startoffset is also checked to ensure that it         called.  The value of startoffset is also checked  to  ensure  that  it
2193         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
2194         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
2195         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,
2196         pcre_exec()  returns  the error PCRE_ERROR_BADUTF8. If startoffset con-         pcre_exec() returns  the  error  PCRE_ERROR_BADUTF8  or,  if  PCRE_PAR-
2197         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
2198           end of the subject, PCRE_ERROR_SHORTUTF8. In  both  cases,  information
2199         If you already know that your subject is valid, and you  want  to  skip         about  the  precise  nature  of the error may also be returned (see the
2200         these    checks    for   performance   reasons,   you   can   set   the         descriptions of these errors in the section entitled Error return  val-
2201         PCRE_NO_UTF8_CHECK option when calling pcre_exec(). You might  want  to         ues from pcre_exec() below).  If startoffset contains a value that does
2202         do  this  for the second and subsequent calls to pcre_exec() if you are         not point to the start of a UTF-8 character (or to the end of the  sub-
2203         making repeated calls to find all  the  matches  in  a  single  subject         ject), PCRE_ERROR_BADUTF8_OFFSET is returned.
2204         string.  However,  you  should  be  sure  that the value of startoffset  
2205         points to the start of a UTF-8 character.  When  PCRE_NO_UTF8_CHECK  is         If  you  already  know that your subject is valid, and you want to skip
2206         set,  the  effect of passing an invalid UTF-8 string as a subject, or a         these   checks   for   performance   reasons,   you   can    set    the
2207         value of startoffset that does not point to the start of a UTF-8  char-         PCRE_NO_UTF8_CHECK  option  when calling pcre_exec(). You might want to
2208         acter, is undefined. Your program may crash.         do this for the second and subsequent calls to pcre_exec() if  you  are
2209           making  repeated  calls  to  find  all  the matches in a single subject
2210           PCRE_PARTIAL         string. However, you should be  sure  that  the  value  of  startoffset
2211           points  to  the start of a UTF-8 character (or the end of the subject).
2212         This  option  turns  on  the  partial  matching feature. If the subject         When PCRE_NO_UTF8_CHECK is set, the effect of passing an invalid  UTF-8
2213         string fails to match the pattern, but at some point during the  match-         string  as  a  subject or an invalid value of startoffset is undefined.
2214         ing  process  the  end of the subject was reached (that is, the subject         Your program may crash.
2215         partially matches the pattern and the failure to  match  occurred  only  
2216         because  there were not enough subject characters), pcre_exec() returns           PCRE_PARTIAL_HARD
2217         PCRE_ERROR_PARTIAL instead of PCRE_ERROR_NOMATCH. When PCRE_PARTIAL  is           PCRE_PARTIAL_SOFT
2218         used,  there  are restrictions on what may appear in the pattern. These  
2219         are discussed in the pcrepartial documentation.         These options turn on the partial matching feature. For backwards  com-
2220           patibility,  PCRE_PARTIAL is a synonym for PCRE_PARTIAL_SOFT. A partial
2221           match occurs if the end of the subject string is reached  successfully,
2222           but  there  are not enough subject characters to complete the match. If
2223           this happens when PCRE_PARTIAL_SOFT (but not PCRE_PARTIAL_HARD) is set,
2224           matching  continues  by  testing any remaining alternatives. Only if no
2225           complete match can be found is PCRE_ERROR_PARTIAL returned  instead  of
2226           PCRE_ERROR_NOMATCH.  In  other  words,  PCRE_PARTIAL_SOFT says that the
2227           caller is prepared to handle a partial match, but only if  no  complete
2228           match can be found.
2229    
2230           If  PCRE_PARTIAL_HARD  is  set, it overrides PCRE_PARTIAL_SOFT. In this
2231           case, if a partial match  is  found,  pcre_exec()  immediately  returns
2232           PCRE_ERROR_PARTIAL,  without  considering  any  other  alternatives. In
2233           other words, when PCRE_PARTIAL_HARD is set, a partial match is  consid-
2234           ered to be more important that an alternative complete match.
2235    
2236           In  both  cases,  the portion of the string that was inspected when the
2237           partial match was found is set as the first matching string. There is a
2238           more  detailed  discussion  of partial and multi-segment matching, with
2239           examples, in the pcrepartial documentation.
2240    
2241     The string to be matched by pcre_exec()     The string to be matched by pcre_exec()
2242    
2243         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
2244         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.
2245         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,
2246         Unlike  the  pattern string, the subject may contain binary zero bytes.         pcre_exec()  returns  PCRE_ERROR_BADOFFSET. When the starting offset is
2247         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,
2248         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
2249           must point to the start of a UTF-8 character (or the end  of  the  sub-
2250         A  non-zero  starting offset is useful when searching for another match         ject).  Unlike  the pattern string, the subject may contain binary zero
2251         in the same subject by calling pcre_exec() again after a previous  suc-         bytes.
2252         cess.   Setting  startoffset differs from just passing over a shortened  
2253         string and setting PCRE_NOTBOL in the case of  a  pattern  that  begins         A non-zero starting offset is useful when searching for  another  match
2254           in  the same subject by calling pcre_exec() again after a previous suc-
2255           cess.  Setting startoffset differs from just passing over  a  shortened
2256           string  and  setting  PCRE_NOTBOL  in the case of a pattern that begins
2257         with any kind of lookbehind. For example, consider the pattern         with any kind of lookbehind. For example, consider the pattern
2258    
2259           \Biss\B           \Biss\B
2260    
2261         which  finds  occurrences  of "iss" in the middle of words. (\B matches         which finds occurrences of "iss" in the middle of  words.  (\B  matches
2262         only if the current position in the subject is not  a  word  boundary.)         only  if  the  current position in the subject is not a word boundary.)
2263         When  applied  to the string "Mississipi" the first call to pcre_exec()         When applied to the string "Mississipi" the first call  to  pcre_exec()
2264         finds the first occurrence. If pcre_exec() is called  again  with  just         finds  the  first  occurrence. If pcre_exec() is called again with just
2265         the  remainder  of  the  subject,  namely  "issipi", it does not match,         the remainder of the subject,  namely  "issipi",  it  does  not  match,
2266         because \B is always false at the start of the subject, which is deemed         because \B is always false at the start of the subject, which is deemed
2267         to  be  a  word  boundary. However, if pcre_exec() is passed the entire         to be a word boundary. However, if pcre_exec()  is  passed  the  entire
2268         string again, but with startoffset set to 4, it finds the second occur-         string again, but with startoffset set to 4, it finds the second occur-
2269         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
2270         discover that it is preceded by a letter.         discover that it is preceded by a letter.
2271    
2272           Finding  all  the  matches  in a subject is tricky when the pattern can
2273           match an empty string. It is possible to emulate Perl's /g behaviour by
2274           first   trying   the   match   again  at  the  same  offset,  with  the
2275           PCRE_NOTEMPTY_ATSTART and  PCRE_ANCHORED  options,  and  then  if  that
2276           fails,  advancing  the  starting  offset  and  trying an ordinary match
2277           again. There is some code that demonstrates how to do this in the pcre-
2278           demo sample program. In the most general case, you have to check to see
2279           if the newline convention recognizes CRLF as a newline, and if so,  and
2280           the current character is CR followed by LF, advance the starting offset
2281           by two characters instead of one.
2282    
2283         If a non-zero starting offset is passed when the pattern  is  anchored,         If a non-zero starting offset is passed when the pattern  is  anchored,
2284         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
2285         if the pattern does not require the match to be at  the  start  of  the         if the pattern does not require the match to be at  the  start  of  the
# Line 1934  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 2295  MATCHING A PATTERN: THE TRADITIONAL FUNC
2295         string. PCRE supports several other kinds of  parenthesized  subpattern         string. PCRE supports several other kinds of  parenthesized  subpattern
2296         that do not cause substrings to be captured.         that do not cause substrings to be captured.
2297    
2298         Captured  substrings are returned to the caller via a vector of integer         Captured substrings are returned to the caller via a vector of integers
2299         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-
2300         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:
2301         Note: this argument is NOT the size of ovector in bytes.         this argument is NOT the size of ovector in bytes.
2302    
2303         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-
2304         strings,  each  substring using a pair of integers. The remaining third         strings,  each  substring using a pair of integers. The remaining third
2305         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-
2306         turing  subpatterns, and is not available for passing back information.         turing  subpatterns, and is not available for passing back information.
2307         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
2308         it is not, it is rounded down.         it is not, it is rounded down.
2309    
2310         When  a  match  is successful, information about captured substrings is         When  a  match  is successful, information about captured substrings is
2311         returned in pairs of integers, starting at the  beginning  of  ovector,         returned in pairs of integers, starting at the  beginning  of  ovector,
2312         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
2313         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
2314         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
2315         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
2316         tor[1],  identify  the  portion  of  the  subject string matched by the         byte offsets, even in UTF-8 mode. They are not character counts.
2317         entire pattern. The next pair is used for the first  capturing  subpat-  
2318         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
2319         highest numbered pair that has been set. For example, if two substrings         portion of the subject string matched by the entire pattern.  The  next
2320         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
2321         subpatterns, the return value from a successful match is 1,  indicating         returned by pcre_exec() is one more than the highest numbered pair that
2322         that just the first pair of offsets has been set.         has  been  set.  For example, if two substrings have been captured, the
2323           returned value is 3. If there are no capturing subpatterns, the  return
2324           value from a successful match is 1, indicating that just the first pair
2325           of offsets has been set.
2326    
2327         If a capturing subpattern is matched repeatedly, it is the last portion         If a capturing subpattern is matched repeatedly, it is the last portion
2328         of the string that it matched that is returned.         of the string that it matched that is returned.
2329    
2330         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,
2331         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
2332         function returns a value of zero. In particular, if the substring  off-         function  returns a value of zero. If neither the actual string matched
2333         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
2334         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-
2335         references  and  the  ovector is not big enough to remember the related         tern contains back references and the ovector  is  not  big  enough  to
2336         substrings, PCRE has to get additional memory for use during  matching.         remember  the related substrings, PCRE has to get additional memory for
2337         Thus it is usually advisable to supply an ovector.         use during matching. Thus it is usually advisable to supply an  ovector
2338           of reasonable size.
2339         The  pcre_info()  function  can  be used to find out how many capturing  
2340         subpatterns there are in a compiled  pattern.  The  smallest  size  for         There  are  some  cases where zero is returned (indicating vector over-
2341         ovector  that  will allow for n captured substrings, in addition to the         flow) when in fact the vector is exactly the right size for  the  final
2342           match. For example, consider the pattern
2343    
2344             (a)(?:(b)c|bd)
2345    
2346           If  a  vector of 6 elements (allowing for only 1 captured substring) is
2347           given with subject string "abd", pcre_exec() will try to set the second
2348           captured string, thereby recording a vector overflow, before failing to
2349           match "c" and backing up  to  try  the  second  alternative.  The  zero
2350           return,  however,  does  correctly  indicate that the maximum number of
2351           slots (namely 2) have been filled. In similar cases where there is tem-
2352           porary  overflow,  but  the final number of used slots is actually less
2353           than the maximum, a non-zero value is returned.
2354    
2355           The pcre_fullinfo() function can be used to find out how many capturing
2356           subpatterns  there  are  in  a  compiled pattern. The smallest size for
2357           ovector that will allow for n captured substrings, in addition  to  the
2358         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.
2359    
2360         It is possible for capturing subpattern number n+1 to match  some  part         It  is  possible for capturing subpattern number n+1 to match some part
2361         of the subject when subpattern n has not been used at all. For example,         of the subject when subpattern n has not been used at all. For example,
2362         if the string "abc" is matched  against  the  pattern  (a|(z))(bc)  the         if  the  string  "abc"  is  matched against the pattern (a|(z))(bc) the
2363         return from the function is 4, and subpatterns 1 and 3 are matched, but         return from the function is 4, and subpatterns 1 and 3 are matched, but
2364         2 is not. When this happens, both values in  the  offset  pairs  corre-         2  is  not.  When  this happens, both values in the offset pairs corre-
2365         sponding to unused subpatterns are set to -1.         sponding to unused subpatterns are set to -1.
2366    
2367         Offset  values  that correspond to unused subpatterns at the end of the         Offset values that correspond to unused subpatterns at the end  of  the
2368         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
2369         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
2370         matched. The return from the function is 2, because  the  highest  used         matched.  The  return  from the function is 2, because the highest used
2371         capturing subpattern number is 1. However, you can refer to the offsets         capturing subpattern number is 1, and the offsets for  for  the  second
2372         for the second and third capturing subpatterns if  you  wish  (assuming         and  third  capturing subpatterns (assuming the vector is large enough,
2373         the vector is large enough, of course).         of course) are set to -1.
2374    
2375           Note: Elements in the first two-thirds of ovector that  do  not  corre-
2376           spond  to  capturing parentheses in the pattern are never changed. That
2377           is, if a pattern contains n capturing parentheses, no more  than  ovec-
2378           tor[0]  to ovector[2n+1] are set by pcre_exec(). The other elements (in
2379           the first two-thirds) retain whatever values they previously had.
2380    
2381         Some  convenience  functions  are  provided for extracting the captured         Some convenience functions are provided  for  extracting  the  captured
2382         substrings as separate strings. These are described below.         substrings as separate strings. These are described below.
2383    
2384     Error return values from pcre_exec()     Error return values from pcre_exec()
2385    
2386         If pcre_exec() fails, it returns a negative number. The  following  are         If  pcre_exec()  fails, it returns a negative number. The following are
2387         defined in the header file:         defined in the header file:
2388    
2389           PCRE_ERROR_NOMATCH        (-1)           PCRE_ERROR_NOMATCH        (-1)
# Line 2006  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 2392  MATCHING A PATTERN: THE TRADITIONAL FUNC
2392    
2393           PCRE_ERROR_NULL           (-2)           PCRE_ERROR_NULL           (-2)
2394    
2395         Either  code  or  subject  was  passed as NULL, or ovector was NULL and         Either code or subject was passed as NULL,  or  ovector  was  NULL  and
2396         ovecsize was not zero.         ovecsize was not zero.
2397    
2398           PCRE_ERROR_BADOPTION      (-3)           PCRE_ERROR_BADOPTION      (-3)
# Line 2015  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 2401  MATCHING A PATTERN: THE TRADITIONAL FUNC
2401    
2402           PCRE_ERROR_BADMAGIC       (-4)           PCRE_ERROR_BADMAGIC       (-4)
2403    
2404         PCRE stores a 4-byte "magic number" at the start of the compiled  code,         PCRE  stores a 4-byte "magic number" at the start of the compiled code,
2405         to catch the case when it is passed a junk pointer and to detect when a         to catch the case when it is passed a junk pointer and to detect when a
2406         pattern that was compiled in an environment of one endianness is run in         pattern that was compiled in an environment of one endianness is run in
2407         an  environment  with the other endianness. This is the error that PCRE         an environment with the other endianness. This is the error  that  PCRE
2408         gives when the magic number is not present.         gives when the magic number is not present.
2409    
2410           PCRE_ERROR_UNKNOWN_OPCODE (-5)           PCRE_ERROR_UNKNOWN_OPCODE (-5)
2411    
2412         While running the pattern match, an unknown item was encountered in the         While running the pattern match, an unknown item was encountered in the
2413         compiled  pattern.  This  error  could be caused by a bug in PCRE or by         compiled pattern. This error could be caused by a bug  in  PCRE  or  by
2414         overwriting of the compiled pattern.         overwriting of the compiled pattern.
2415    
2416           PCRE_ERROR_NOMEMORY       (-6)           PCRE_ERROR_NOMEMORY       (-6)
2417    
2418         If a pattern contains back references, but the ovector that  is  passed         If  a  pattern contains back references, but the ovector that is passed
2419         to pcre_exec() is not big enough to remember the referenced substrings,         to pcre_exec() is not big enough to remember the referenced substrings,
2420         PCRE gets a block of memory at the start of matching to  use  for  this         PCRE  gets  a  block of memory at the start of matching to use for this
2421         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
2422         memory is automatically freed at the end of matching.         memory is automatically freed at the end of matching.
2423    
2424           This  error  is also given if pcre_stack_malloc() fails in pcre_exec().
2425           This can happen only when PCRE has been compiled with  --disable-stack-
2426           for-recursion.
2427    
2428           PCRE_ERROR_NOSUBSTRING    (-7)           PCRE_ERROR_NOSUBSTRING    (-7)
2429    
2430         This error is used by the pcre_copy_substring(),  pcre_get_substring(),         This  error is used by the pcre_copy_substring(), pcre_get_substring(),
2431         and  pcre_get_substring_list()  functions  (see  below).  It  is  never         and  pcre_get_substring_list()  functions  (see  below).  It  is  never
2432         returned by pcre_exec().         returned by pcre_exec().
2433    
2434           PCRE_ERROR_MATCHLIMIT     (-8)           PCRE_ERROR_MATCHLIMIT     (-8)
2435    
2436         The backtracking limit, as specified by  the  match_limit  field  in  a         The  backtracking  limit,  as  specified  by the match_limit field in a
2437         pcre_extra  structure  (or  defaulted) was reached. See the description         pcre_extra structure (or defaulted) was reached.  See  the  description
2438         above.         above.
2439    
2440           PCRE_ERROR_CALLOUT        (-9)           PCRE_ERROR_CALLOUT        (-9)
2441    
2442         This error is never generated by pcre_exec() itself. It is provided for         This error is never generated by pcre_exec() itself. It is provided for
2443         use  by  callout functions that want to yield a distinctive error code.         use by callout functions that want to yield a distinctive  error  code.
2444         See the pcrecallout documentation for details.         See the pcrecallout documentation for details.
2445    
2446           PCRE_ERROR_BADUTF8        (-10)           PCRE_ERROR_BADUTF8        (-10)
2447    
2448         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
2449         subject.         subject, and the PCRE_NO_UTF8_CHECK option was not set. If the size  of
2450           the  output  vector  (ovecsize)  is  at least 2, the byte offset to the
2451           start of the the invalid UTF-8 character is placed in  the  first  ele-
2452           ment,  and  a  reason  code is placed in the second element. The reason
2453           codes are listed in the following section.  For backward compatibility,
2454           if  PCRE_PARTIAL_HARD is set and the problem is a truncated UTF-8 char-
2455           acter  at  the  end  of  the   subject   (reason   codes   1   to   5),
2456           PCRE_ERROR_SHORTUTF8 is returned instead of PCRE_ERROR_BADUTF8.
2457    
2458           PCRE_ERROR_BADUTF8_OFFSET (-11)           PCRE_ERROR_BADUTF8_OFFSET (-11)
2459    
2460         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
2461         value of startoffset did not point to the beginning of a UTF-8  charac-         found to be valid (the PCRE_NO_UTF8_CHECK option was not set), but  the
2462         ter.         value  of startoffset did not point to the beginning of a UTF-8 charac-
2463           ter or the end of the subject.
2464    
2465           PCRE_ERROR_PARTIAL        (-12)           PCRE_ERROR_PARTIAL        (-12)
2466    
2467         The  subject  string did not match, but it did match partially. See the         The subject string did not match, but it did match partially.  See  the
2468         pcrepartial documentation for details of partial matching.         pcrepartial documentation for details of partial matching.
2469    
2470           PCRE_ERROR_BADPARTIAL     (-13)           PCRE_ERROR_BADPARTIAL     (-13)
2471    
2472         The PCRE_PARTIAL option was used with  a  compiled  pattern  containing         This  code  is  no  longer  in  use.  It was formerly returned when the
2473         items  that are not supported for partial matching. See the pcrepartial         PCRE_PARTIAL option was used with a compiled pattern  containing  items
2474         documentation for details of partial matching.         that  were  not  supported  for  partial  matching.  From  release 8.00
2475           onwards, there are no restrictions on partial matching.
2476    
2477           PCRE_ERROR_INTERNAL       (-14)           PCRE_ERROR_INTERNAL       (-14)
2478    
# Line 2082  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 2481  MATCHING A PATTERN: THE TRADITIONAL FUNC
2481    
2482           PCRE_ERROR_BADCOUNT       (-15)           PCRE_ERROR_BADCOUNT       (-15)
2483    
2484         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.
2485    
2486           PCRE_ERROR_RECURSIONLIMIT (-21)           PCRE_ERROR_RECURSIONLIMIT (-21)
2487    
2488         The internal recursion limit, as specified by the match_limit_recursion         The internal recursion limit, as specified by the match_limit_recursion
2489         field  in  a  pcre_extra  structure (or defaulted) was reached. See the         field in a pcre_extra structure (or defaulted)  was  reached.  See  the
2490         description above.         description above.
2491    
2492           PCRE_ERROR_BADNEWLINE     (-23)           PCRE_ERROR_BADNEWLINE     (-23)
2493    
2494         An invalid combination of PCRE_NEWLINE_xxx options was given.         An invalid combination of PCRE_NEWLINE_xxx options was given.
2495    
2496             PCRE_ERROR_BADOFFSET      (-24)
2497    
2498           The value of startoffset was negative or greater than the length of the
2499           subject, that is, the value in length.
2500    
2501             PCRE_ERROR_SHORTUTF8      (-25)
2502    
2503           This error is returned instead of PCRE_ERROR_BADUTF8 when  the  subject
2504           string  ends with a truncated UTF-8 character and the PCRE_PARTIAL_HARD
2505           option is set.  Information  about  the  failure  is  returned  as  for
2506           PCRE_ERROR_BADUTF8.  It  is in fact sufficient to detect this case, but
2507           this special error code for PCRE_PARTIAL_HARD precedes the  implementa-
2508           tion  of returned information; it is retained for backwards compatibil-
2509           ity.
2510    
2511             PCRE_ERROR_RECURSELOOP    (-26)
2512    
2513           This error is returned when pcre_exec() detects a recursion loop within
2514           the  pattern. Specifically, it means that either the whole pattern or a
2515           subpattern has been called recursively for the second time at the  same
2516           position in the subject string. Some simple patterns that might do this
2517           are detected and faulted at compile time, but more  complicated  cases,
2518           in particular mutual recursions between two different subpatterns, can-
2519           not be detected until run time.
2520    
2521             PCRE_ERROR_JIT_STACKLIMIT (-27)
2522    
2523           This error is returned when a pattern  that  was  successfully  studied
2524           using  the PCRE_STUDY_JIT_COMPILE option is being matched, but the mem-
2525           ory available for  the  just-in-time  processing  stack  is  not  large
2526           enough. See the pcrejit documentation for more details.
2527    
2528         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().
2529    
2530       Reason codes for invalid UTF-8 strings
2531    
2532           When pcre_exec() returns either PCRE_ERROR_BADUTF8 or PCRE_ERROR_SHORT-
2533           UTF8, and the size of the output vector (ovecsize) is at least  2,  the
2534           offset  of  the  start  of the invalid UTF-8 character is placed in the
2535           first output vector element (ovector[0]) and a reason code is placed in
2536           the  second  element  (ovector[1]). The reason codes are given names in
2537           the pcre.h header file:
2538    
2539             PCRE_UTF8_ERR1
2540             PCRE_UTF8_ERR2
2541             PCRE_UTF8_ERR3
2542             PCRE_UTF8_ERR4
2543             PCRE_UTF8_ERR5
2544    
2545           The string ends with a truncated UTF-8 character;  the  code  specifies
2546           how  many bytes are missing (1 to 5). Although RFC 3629 restricts UTF-8
2547           characters to be no longer than 4 bytes, the  encoding  scheme  (origi-
2548           nally  defined  by  RFC  2279)  allows  for  up to 6 bytes, and this is
2549           checked first; hence the possibility of 4 or 5 missing bytes.
2550    
2551             PCRE_UTF8_ERR6
2552             PCRE_UTF8_ERR7
2553             PCRE_UTF8_ERR8
2554             PCRE_UTF8_ERR9
2555             PCRE_UTF8_ERR10
2556    
2557           The two most significant bits of the 2nd, 3rd, 4th, 5th, or 6th byte of
2558           the  character  do  not have the binary value 0b10 (that is, either the
2559           most significant bit is 0, or the next bit is 1).
2560    
2561             PCRE_UTF8_ERR11
2562             PCRE_UTF8_ERR12
2563    
2564           A character that is valid by the RFC 2279 rules is either 5 or 6  bytes
2565           long; these code points are excluded by RFC 3629.
2566    
2567             PCRE_UTF8_ERR13
2568    
2569           A  4-byte character has a value greater than 0x10fff; these code points
2570           are excluded by RFC 3629.
2571    
2572             PCRE_UTF8_ERR14
2573    
2574           A 3-byte character has a value in the  range  0xd800  to  0xdfff;  this
2575           range  of code points are reserved by RFC 3629 for use with UTF-16, and
2576           so are excluded from UTF-8.
2577    
2578             PCRE_UTF8_ERR15
2579             PCRE_UTF8_ERR16
2580             PCRE_UTF8_ERR17
2581             PCRE_UTF8_ERR18
2582             PCRE_UTF8_ERR19
2583    
2584           A 2-, 3-, 4-, 5-, or 6-byte character is "overlong", that is, it  codes
2585           for  a  value that can be represented by fewer bytes, which is invalid.
2586           For example, the two bytes 0xc0, 0xae give the value 0x2e,  whose  cor-
2587           rect coding uses just one byte.
2588    
2589             PCRE_UTF8_ERR20
2590    
2591           The two most significant bits of the first byte of a character have the
2592           binary value 0b10 (that is, the most significant bit is 1 and the  sec-
2593           ond  is  0). Such a byte can only validly occur as the second or subse-
2594           quent byte of a multi-byte character.
2595    
2596             PCRE_UTF8_ERR21
2597    
2598           The first byte of a character has the value 0xfe or 0xff. These  values
2599           can never occur in a valid UTF-8 string.
2600    
2601    
2602  EXTRACTING CAPTURED SUBSTRINGS BY NUMBER  EXTRACTING CAPTURED SUBSTRINGS BY NUMBER
2603    
# Line 2110  EXTRACTING CAPTURED SUBSTRINGS BY NUMBER Line 2612  EXTRACTING CAPTURED SUBSTRINGS BY NUMBER
2612         int pcre_get_substring_list(const char *subject,         int pcre_get_substring_list(const char *subject,
2613              int *ovector, int stringcount, const char ***listptr);              int *ovector, int stringcount, const char ***listptr);
2614    
2615         Captured substrings can be  accessed  directly  by  using  the  offsets         Captured  substrings  can  be  accessed  directly  by using the offsets
2616         returned  by  pcre_exec()  in  ovector.  For convenience, the functions         returned by pcre_exec() in  ovector.  For  convenience,  the  functions
2617         pcre_copy_substring(),    pcre_get_substring(),    and    pcre_get_sub-         pcre_copy_substring(),    pcre_get_substring(),    and    pcre_get_sub-
2618         string_list()  are  provided for extracting captured substrings as new,         string_list() are provided for extracting captured substrings  as  new,
2619         separate, zero-terminated strings. These functions identify  substrings         separate,  zero-terminated strings. These functions identify substrings
2620         by  number.  The  next section describes functions for extracting named         by number. The next section describes functions  for  extracting  named
2621         substrings.         substrings.
2622    
2623         A substring that contains a binary zero is correctly extracted and  has         A  substring that contains a binary zero is correctly extracted and has
2624         a  further zero added on the end, but the result is not, of course, a C         a further zero added on the end, but the result is not, of course, a  C
2625         string.  However, you can process such a string  by  referring  to  the         string.   However,  you  can  process such a string by referring to the
2626         length  that  is  returned  by  pcre_copy_substring() and pcre_get_sub-         length that is  returned  by  pcre_copy_substring()  and  pcre_get_sub-
2627         string().  Unfortunately, the interface to pcre_get_substring_list() is         string().  Unfortunately, the interface to pcre_get_substring_list() is
2628         not  adequate for handling strings containing binary zeros, because the         not adequate for handling strings containing binary zeros, because  the
2629         end of the final string is not independently indicated.         end of the final string is not independently indicated.
2630    
2631         The first three arguments are the same for all  three  of  these  func-         The  first  three  arguments  are the same for all three of these func-
2632         tions:  subject  is  the subject string that has just been successfully         tions: subject is the subject string that has  just  been  successfully
2633         matched, ovector is a pointer to the vector of integer offsets that was         matched, ovector is a pointer to the vector of integer offsets that was
2634         passed to pcre_exec(), and stringcount is the number of substrings that         passed to pcre_exec(), and stringcount is the number of substrings that
2635         were captured by the match, including the substring  that  matched  the         were  captured  by  the match, including the substring that matched the
2636         entire regular expression. This is the value returned by pcre_exec() if         entire regular expression. This is the value returned by pcre_exec() if
2637         it is greater than zero. If pcre_exec() returned zero, indicating  that         it  is greater than zero. If pcre_exec() returned zero, indicating that
2638         it  ran out of space in ovector, the value passed as stringcount should         it ran out of space in ovector, the value passed as stringcount  should
2639         be the number of elements in the vector divided by three.         be the number of elements in the vector divided by three.
2640    
2641         The functions pcre_copy_substring() and pcre_get_substring() extract  a         The  functions pcre_copy_substring() and pcre_get_substring() extract a
2642         single  substring,  whose  number  is given as stringnumber. A value of         single substring, whose number is given as  stringnumber.  A  value  of
2643         zero extracts the substring that matched the  entire  pattern,  whereas         zero  extracts  the  substring that matched the entire pattern, whereas
2644         higher  values  extract  the  captured  substrings.  For pcre_copy_sub-         higher values  extract  the  captured  substrings.  For  pcre_copy_sub-
2645         string(), the string is placed in buffer,  whose  length  is  given  by         string(),  the  string  is  placed  in buffer, whose length is given by
2646         buffersize,  while  for  pcre_get_substring()  a new block of memory is         buffersize, while for pcre_get_substring() a new  block  of  memory  is
2647         obtained via pcre_malloc, and its address is  returned  via  stringptr.         obtained  via  pcre_malloc,  and its address is returned via stringptr.
2648         The  yield  of  the function is the length of the string, not including         The yield of the function is the length of the  string,  not  including
2649         the terminating zero, or one of these error codes:         the terminating zero, or one of these error codes:
2650    
2651           PCRE_ERROR_NOMEMORY       (-6)           PCRE_ERROR_NOMEMORY       (-6)
2652    
2653         The buffer was too small for pcre_copy_substring(), or the  attempt  to         The  buffer  was too small for pcre_copy_substring(), or the attempt to
2654         get memory failed for pcre_get_substring().         get memory failed for pcre_get_substring().
2655    
2656           PCRE_ERROR_NOSUBSTRING    (-7)           PCRE_ERROR_NOSUBSTRING    (-7)
2657    
2658         There is no substring whose number is stringnumber.         There is no substring whose number is stringnumber.
2659    
2660         The  pcre_get_substring_list()  function  extracts  all  available sub-         The pcre_get_substring_list()  function  extracts  all  available  sub-
2661         strings and builds a list of pointers to them. All this is  done  in  a         strings  and  builds  a list of pointers to them. All this is done in a
2662         single block of memory that is obtained via pcre_malloc. The address of         single block of memory that is obtained via pcre_malloc. The address of
2663         the memory block is returned via listptr, which is also  the  start  of         the  memory  block  is returned via listptr, which is also the start of
2664         the  list  of  string pointers. The end of the list is marked by a NULL         the list of string pointers. The end of the list is marked  by  a  NULL
2665         pointer. The yield of the function is zero if all  went  well,  or  the         pointer.  The  yield  of  the function is zero if all went well, or the
2666         error code         error code
2667    
2668           PCRE_ERROR_NOMEMORY       (-6)           PCRE_ERROR_NOMEMORY       (-6)
2669    
2670         if the attempt to get the memory block failed.         if the attempt to get the memory block failed.
2671    
2672         When  any of these functions encounter a substring that is unset, which         When any of these functions encounter a substring that is unset,  which
2673         can happen when capturing subpattern number n+1 matches  some  part  of         can  happen  when  capturing subpattern number n+1 matches some part of
2674         the  subject, but subpattern n has not been used at all, they return an         the subject, but subpattern n has not been used at all, they return  an
2675         empty string. This can be distinguished from a genuine zero-length sub-         empty string. This can be distinguished from a genuine zero-length sub-
2676         string  by inspecting the appropriate offset in ovector, which is nega-         string by inspecting the appropriate offset in ovector, which is  nega-
2677         tive for unset substrings.         tive for unset substrings.
2678    
2679         The two convenience functions pcre_free_substring() and  pcre_free_sub-         The  two convenience functions pcre_free_substring() and pcre_free_sub-
2680         string_list()  can  be  used  to free the memory returned by a previous         string_list() can be used to free the memory  returned  by  a  previous
2681         call  of  pcre_get_substring()  or  pcre_get_substring_list(),  respec-         call  of  pcre_get_substring()  or  pcre_get_substring_list(),  respec-
2682         tively.  They  do  nothing  more  than  call the function pointed to by         tively. They do nothing more than  call  the  function  pointed  to  by
2683         pcre_free, which of course could be called directly from a  C  program.         pcre_free,  which  of course could be called directly from a C program.
2684         However,  PCRE is used in some situations where it is linked via a spe-         However, PCRE is used in some situations where it is linked via a  spe-
2685         cial  interface  to  another  programming  language  that  cannot   use         cial   interface  to  another  programming  language  that  cannot  use
2686         pcre_free  directly;  it is for these cases that the functions are pro-         pcre_free directly; it is for these cases that the functions  are  pro-
2687         vided.         vided.
2688    
2689    
# Line 2200  EXTRACTING CAPTURED SUBSTRINGS BY NAME Line 2702  EXTRACTING CAPTURED SUBSTRINGS BY NAME
2702              int stringcount, const char *stringname,              int stringcount, const char *stringname,
2703              const char **stringptr);              const char **stringptr);
2704    
2705         To extract a substring by name, you first have to find associated  num-         To  extract a substring by name, you first have to find associated num-
2706         ber.  For example, for this pattern         ber.  For example, for this pattern
2707    
2708           (a+)b(?<xxx>\d+)...           (a+)b(?<xxx>\d+)...
# Line 2209  EXTRACTING CAPTURED SUBSTRINGS BY NAME Line 2711  EXTRACTING CAPTURED SUBSTRINGS BY NAME
2711         be unique (PCRE_DUPNAMES was not set), you can find the number from the         be unique (PCRE_DUPNAMES was not set), you can find the number from the
2712         name by calling pcre_get_stringnumber(). The first argument is the com-         name by calling pcre_get_stringnumber(). The first argument is the com-
2713         piled pattern, and the second is the name. The yield of the function is         piled pattern, and the second is the name. The yield of the function is
2714         the  subpattern  number,  or PCRE_ERROR_NOSUBSTRING (-7) if there is no         the subpattern number, or PCRE_ERROR_NOSUBSTRING (-7) if  there  is  no
2715         subpattern of that name.         subpattern of that name.
2716    
2717         Given the number, you can extract the substring directly, or use one of         Given the number, you can extract the substring directly, or use one of
2718         the functions described in the previous section. For convenience, there         the functions described in the previous section. For convenience, there
2719         are also two functions that do the whole job.         are also two functions that do the whole job.
2720    
2721         Most   of   the   arguments    of    pcre_copy_named_substring()    and         Most    of    the    arguments   of   pcre_copy_named_substring()   and
2722         pcre_get_named_substring()  are  the  same  as  those for the similarly         pcre_get_named_substring() are the same  as  those  for  the  similarly
2723         named functions that extract by number. As these are described  in  the         named  functions  that extract by number. As these are described in the
2724         previous  section,  they  are not re-described here. There are just two         previous section, they are not re-described here. There  are  just  two
2725         differences:         differences:
2726    
2727         First, instead of a substring number, a substring name is  given.  Sec-         First,  instead  of a substring number, a substring name is given. Sec-
2728         ond, there is an extra argument, given at the start, which is a pointer         ond, there is an extra argument, given at the start, which is a pointer
2729         to the compiled pattern. This is needed in order to gain access to  the         to  the compiled pattern. This is needed in order to gain access to the
2730         name-to-number translation table.         name-to-number translation table.
2731    
2732         These  functions call pcre_get_stringnumber(), and if it succeeds, they         These functions call pcre_get_stringnumber(), and if it succeeds,  they
2733         then call pcre_copy_substring() or pcre_get_substring(),  as  appropri-         then  call  pcre_copy_substring() or pcre_get_substring(), as appropri-
2734         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
2735         behaviour may not be what you want (see the next section).         behaviour may not be what you want (see the next section).
2736    
2737           Warning: If the pattern uses the (?| feature to set up multiple subpat-
2738           terns with the same number, as described in the  section  on  duplicate
2739           subpattern  numbers  in  the  pcrepattern page, you cannot use names to
2740           distinguish the different subpatterns, because names are  not  included
2741           in  the compiled code. The matching process uses only numbers. For this
2742           reason, the use of different names for subpatterns of the  same  number
2743           causes an error at compile time.
2744    
2745    
2746  DUPLICATE SUBPATTERN NAMES  DUPLICATE SUBPATTERN NAMES
2747    
2748         int pcre_get_stringtable_entries(const pcre *code,         int pcre_get_stringtable_entries(const pcre *code,
2749              const char *name, char **first, char **last);              const char *name, char **first, char **last);
2750    
2751         When a pattern is compiled with the  PCRE_DUPNAMES  option,  names  for         When  a  pattern  is  compiled with the PCRE_DUPNAMES option, names for
2752         subpatterns  are  not  required  to  be unique. Normally, patterns with         subpatterns are not required to be unique. (Duplicate names are  always
2753         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 (?|
2754         subpatterns  participates. An example is shown in the pcrepattern docu-         feature. Indeed, if such subpatterns are named, they  are  required  to
2755         mentation.         use the same names.)
2756    
2757           Normally, patterns with duplicate names are such that in any one match,
2758           only one of the named subpatterns participates. An example is shown  in
2759           the pcrepattern documentation.
2760    
2761         When   duplicates   are   present,   pcre_copy_named_substring()    and         When    duplicates   are   present,   pcre_copy_named_substring()   and
2762         pcre_get_named_substring()  return the first substring corresponding to         pcre_get_named_substring() return the first substring corresponding  to
2763         the given name that is set. If  none  are  set,  PCRE_ERROR_NOSUBSTRING         the  given  name  that  is set. If none are set, PCRE_ERROR_NOSUBSTRING
2764         (-7)  is  returned;  no  data  is returned. The pcre_get_stringnumber()         (-7) is returned; no  data  is  returned.  The  pcre_get_stringnumber()
2765         function returns one of the numbers that are associated with the  name,         function  returns one of the numbers that are associated with the name,
2766         but it is not defined which it is.         but it is not defined which it is.
2767    
2768         If  you want to get full details of all captured substrings for a given         If you want to get full details of all captured substrings for a  given
2769         name, you must use  the  pcre_get_stringtable_entries()  function.  The         name,  you  must  use  the pcre_get_stringtable_entries() function. The
2770         first argument is the compiled pattern, and the second is the name. The         first argument is the compiled pattern, and the second is the name. The
2771         third and fourth are pointers to variables which  are  updated  by  the         third  and  fourth  are  pointers to variables which are updated by the
2772         function. After it has run, they point to the first and last entries in         function. After it has run, they point to the first and last entries in
2773         the name-to-number table  for  the  given  name.  The  function  itself         the  name-to-number  table  for  the  given  name.  The function itself
2774         returns  the  length  of  each entry, or PCRE_ERROR_NOSUBSTRING (-7) if         returns the length of each entry,  or  PCRE_ERROR_NOSUBSTRING  (-7)  if
2775         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-
2776         tion  entitled  Information  about  a  pattern.  Given all the relevant         tion entitled Information about a pattern above.  Given all  the  rele-
2777         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
2778         the captured data, if any.         hence the captured data, if any.
2779    
2780    
2781  FINDING ALL POSSIBLE MATCHES  FINDING ALL POSSIBLE MATCHES
2782    
2783         The  traditional  matching  function  uses a similar algorithm to Perl,         The traditional matching function uses a  similar  algorithm  to  Perl,
2784         which stops when it finds the first match, starting at a given point in         which stops when it finds the first match, starting at a given point in
2785         the  subject.  If you want to find all possible matches, or the longest         the subject. If you want to find all possible matches, or  the  longest
2786         possible match, consider using the alternative matching  function  (see         possible  match,  consider using the alternative matching function (see
2787         below)  instead.  If you cannot use the alternative function, but still         below) instead. If you cannot use the alternative function,  but  still
2788         need to find all possible matches, you can kludge it up by  making  use         need  to  find all possible matches, you can kludge it up by making use
2789         of the callout facility, which is described in the pcrecallout documen-         of the callout facility, which is described in the pcrecallout documen-
2790         tation.         tation.
2791    
2792         What you have to do is to insert a callout right at the end of the pat-         What you have to do is to insert a callout right at the end of the pat-
2793         tern.   When your callout function is called, extract and save the cur-         tern.  When your callout function is called, extract and save the  cur-
2794         rent matched substring. Then return  1,  which  forces  pcre_exec()  to         rent  matched  substring.  Then  return  1, which forces pcre_exec() to
2795         backtrack  and  try other alternatives. Ultimately, when it runs out of         backtrack and try other alternatives. Ultimately, when it runs  out  of
2796         matches, pcre_exec() will yield PCRE_ERROR_NOMATCH.         matches, pcre_exec() will yield PCRE_ERROR_NOMATCH.
2797    
2798    
# Line 2289  MATCHING A PATTERN: THE ALTERNATIVE FUNC Line 2803  MATCHING A PATTERN: THE ALTERNATIVE FUNC
2803              int options, int *ovector, int ovecsize,              int options, int *ovector, int ovecsize,
2804              int *workspace, int wscount);              int *workspace, int wscount);
2805    
2806         The function pcre_dfa_exec()  is  called  to  match  a  subject  string         The  function  pcre_dfa_exec()  is  called  to  match  a subject string
2807         against  a  compiled pattern, using a matching algorithm that scans the         against a compiled pattern, using a matching algorithm that  scans  the
2808         subject string just once, and does not backtrack.  This  has  different         subject  string  just  once, and does not backtrack. This has different
2809         characteristics  to  the  normal  algorithm, and is not compatible with         characteristics to the normal algorithm, and  is  not  compatible  with
2810         Perl. Some of the features of PCRE patterns are not  supported.  Never-         Perl.  Some  of the features of PCRE patterns are not supported. Never-
2811         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
2812         a discussion of the two matching algorithms, see the pcrematching docu-         a  discussion  of  the  two matching algorithms, and a list of features
2813         mentation.         that pcre_dfa_exec() does not support, see the pcrematching  documenta-
2814           tion.
2815    
2816         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
2817         pcre_exec(), plus two extras. The ovector argument is used in a differ-         pcre_exec(), plus two extras. The ovector argument is used in a differ-
# Line 2331  MATCHING A PATTERN: THE ALTERNATIVE FUNC Line 2846  MATCHING A PATTERN: THE ALTERNATIVE FUNC
2846    
2847         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
2848         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-
2849         LINE_xxx,  PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY, PCRE_NO_UTF8_CHECK,         LINE_xxx,        PCRE_NOTBOL,        PCRE_NOTEOL,        PCRE_NOTEMPTY,
2850         PCRE_PARTIAL, PCRE_DFA_SHORTEST, and PCRE_DFA_RESTART. All but the last         PCRE_NOTEMPTY_ATSTART,      PCRE_NO_UTF8_CHECK,       PCRE_BSR_ANYCRLF,
2851         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-
2852         not repeated here.         TIAL_SOFT, PCRE_DFA_SHORTEST, and PCRE_DFA_RESTART.  All but  the  last
2853           four  of  these  are  exactly  the  same  as  for pcre_exec(), so their
2854           PCRE_PARTIAL         description is not repeated here.
2855    
2856         This has the same general effect as it does for  pcre_exec(),  but  the           PCRE_PARTIAL_HARD
2857         details   are   slightly   different.  When  PCRE_PARTIAL  is  set  for           PCRE_PARTIAL_SOFT
2858         pcre_dfa_exec(), the return code PCRE_ERROR_NOMATCH is  converted  into  
2859         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
2860         been no complete matches, but there is still at least one matching pos-         details  are  slightly  different.  When  PCRE_PARTIAL_HARD  is set for
2861         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-
2862         set as the first matching string.         ject  is  reached  and there is still at least one matching possibility
2863           that requires additional characters. This happens even if some complete
2864           matches have also been found. When PCRE_PARTIAL_SOFT is set, the return
2865           code PCRE_ERROR_NOMATCH is converted into PCRE_ERROR_PARTIAL if the end
2866           of  the  subject  is  reached, there have been no complete matches, but
2867           there is still at least one matching possibility. The  portion  of  the
2868           string  that  was inspected when the longest partial match was found is
2869           set as the first matching string  in  both  cases.   There  is  a  more
2870           detailed  discussion  of partial and multi-segment matching, with exam-
2871           ples, in the pcrepartial documentation.
2872    
2873           PCRE_DFA_SHORTEST           PCRE_DFA_SHORTEST
2874    
# Line 2355  MATCHING A PATTERN: THE ALTERNATIVE FUNC Line 2879  MATCHING A PATTERN: THE ALTERNATIVE FUNC
2879    
2880           PCRE_DFA_RESTART           PCRE_DFA_RESTART
2881    
2882         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
2883         returns a partial match, it is possible to call it  again,  with  addi-         again, with additional subject characters, and have  it  continue  with
2884         tional  subject  characters,  and have it continue with the same match.         the  same match. The PCRE_DFA_RESTART option requests this action; when
2885         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
2886         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
2887         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
2888         match.  There  is  more  discussion of this facility in the pcrepartial         pcrepartial documentation.
        documentation.  
2889    
2890     Successful returns from pcre_dfa_exec()     Successful returns from pcre_dfa_exec()
2891    
2892         When pcre_dfa_exec() succeeds, it may have matched more than  one  sub-         When  pcre_dfa_exec()  succeeds, it may have matched more than one sub-
2893         string in the subject. Note, however, that all the matches from one run         string in the subject. Note, however, that all the matches from one run
2894         of the function start at the same point in  the  subject.  The  shorter         of  the  function  start  at the same point in the subject. The shorter
2895         matches  are all initial substrings of the longer matches. For example,         matches are all initial substrings of the longer matches. For  example,
2896         if the pattern         if the pattern
2897    
2898           <.*>           <.*>
# Line 2384  MATCHING A PATTERN: THE ALTERNATIVE FUNC Line 2907  MATCHING A PATTERN: THE ALTERNATIVE FUNC
2907           <something> <something else>           <something> <something else>
2908           <something> <something else> <something further>           <something> <something else> <something further>
2909    
2910         On success, the yield of the function is a number  greater  than  zero,         On  success,  the  yield of the function is a number greater than zero,
2911         which  is  the  number of matched substrings. The substrings themselves         which is the number of matched substrings.  The  substrings  themselves
2912         are returned in ovector. Each string uses two elements;  the  first  is         are  returned  in  ovector. Each string uses two elements; the first is
2913         the  offset  to  the start, and the second is the offset to the end. In         the offset to the start, and the second is the offset to  the  end.  In
2914         fact, all the strings have the same start  offset.  (Space  could  have         fact,  all  the  strings  have the same start offset. (Space could have
2915         been  saved by giving this only once, but it was decided to retain some         been saved by giving this only once, but it was decided to retain  some
2916         compatibility with the way pcre_exec() returns data,  even  though  the         compatibility  with  the  way pcre_exec() returns data, even though the
2917         meaning of the strings is different.)         meaning of the strings is different.)
2918    
2919         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-
2920         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
2921         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
2922         filled with the longest matches.         filled  with  the  longest matches. Unlike pcre_exec(), pcre_dfa_exec()
2923           can use the entire ovector for returning matched strings.
2924    
2925     Error returns from pcre_dfa_exec()     Error returns from pcre_dfa_exec()
2926    
# Line 2420  MATCHING A PATTERN: THE ALTERNATIVE FUNC Line 2944  MATCHING A PATTERN: THE ALTERNATIVE FUNC
2944           PCRE_ERROR_DFA_UMLIMIT    (-18)           PCRE_ERROR_DFA_UMLIMIT    (-18)
2945    
2946         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
2947         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
2948         (it is meaningless).         fields.  This  is  not  supported (these fields are meaningless for DFA
2949           matching).
2950    
2951           PCRE_ERROR_DFA_WSSIZE     (-19)           PCRE_ERROR_DFA_WSSIZE     (-19)
2952    
2953         This  return  is  given  if  pcre_dfa_exec()  runs  out of space in the         This return is given if  pcre_dfa_exec()  runs  out  of  space  in  the
2954         workspace vector.         workspace vector.
2955    
2956           PCRE_ERROR_DFA_RECURSE    (-20)           PCRE_ERROR_DFA_RECURSE    (-20)
2957    
2958         When a recursive subpattern is processed, the matching  function  calls         When  a  recursive subpattern is processed, the matching function calls
2959         itself  recursively,  using  private vectors for ovector and workspace.         itself recursively, using private vectors for  ovector  and  workspace.
2960         This error is given if the output vector  is  not  large  enough.  This         This  error  is  given  if  the output vector is not large enough. This
2961         should be extremely rare, as a vector of size 1000 is used.         should be extremely rare, as a vector of size 1000 is used.
2962    
2963    
2964  SEE ALSO  SEE ALSO
2965    
2966         pcrebuild(3),  pcrecallout(3), pcrecpp(3)(3), pcrematching(3), pcrepar-         pcrebuild(3), pcrecallout(3), pcrecpp(3)(3), pcrematching(3),  pcrepar-
2967         tial(3), pcreposix(3), pcreprecompile(3), pcresample(3),  pcrestack(3).         tial(3), pcreposix(3), pcreprecompile(3), pcresample(3), pcrestack(3).
2968    
2969    
2970  AUTHOR  AUTHOR
# Line 2451  AUTHOR Line 2976  AUTHOR
2976    
2977  REVISION  REVISION
2978    
2979         Last updated: 09 August 2007         Last updated: 06 September 2011
2980         Copyright (c) 1997-2007 University of Cambridge.         Copyright (c) 1997-2011 University of Cambridge.
2981  ------------------------------------------------------------------------------  ------------------------------------------------------------------------------
2982    
2983    
# Line 2481  PCRE CALLOUTS Line 3006  PCRE CALLOUTS
3006    
3007           (?C1)abc(?C2)def           (?C1)abc(?C2)def
3008    
3009         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
3010         called, PCRE automatically  inserts  callouts,  all  with  number  255,         pcre_compile2() is called, PCRE  automatically  inserts  callouts,  all
3011         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
3012         used with the pattern         PCRE_AUTO_CALLOUT is used with the pattern
3013    
3014           A(\d{2}|--)           A(\d{2}|--)
3015    
# Line 2499  PCRE CALLOUTS Line 3024  PCRE CALLOUTS
3024         pattern is matched. This is useful information when you are  trying  to         pattern is matched. This is useful information when you are  trying  to
3025         optimize the performance of a particular pattern.         optimize the performance of a particular pattern.
3026    
3027           The  use  of callouts in a pattern makes it ineligible for optimization
3028           by  the  just-in-time  compiler.  Studying  such  a  pattern  with  the
3029           PCRE_STUDY_JIT_COMPILE option always fails.
3030    
3031    
3032  MISSING CALLOUTS  MISSING CALLOUTS
3033    
3034         You  should  be  aware  that,  because of optimizations in the way PCRE         You  should  be  aware  that,  because of optimizations in the way PCRE
3035         matches patterns, callouts sometimes do not happen. For example, if the         matches patterns by default, callouts  sometimes  do  not  happen.  For
3036         pattern is         example, if the pattern is
3037    
3038           ab(?C4)cd           ab(?C4)cd
3039    
# Line 2513  MISSING CALLOUTS Line 3042  MISSING CALLOUTS
3042         ever  start,  and  the  callout is never reached. However, with "abyd",         ever  start,  and  the  callout is never reached. However, with "abyd",
3043         though the result is still no match, the callout is obeyed.         though the result is still no match, the callout is obeyed.
3044    
3045           If the pattern is studied, PCRE knows the minimum length of a  matching
3046           string,  and will immediately give a "no match" return without actually
3047           running a match if the subject is not long enough, or,  for  unanchored
3048           patterns, if it has been scanned far enough.
3049    
3050           You  can disable these optimizations by passing the PCRE_NO_START_OPTI-
3051           MIZE option to pcre_compile(), pcre_exec(), or pcre_dfa_exec(),  or  by
3052           starting the pattern with (*NO_START_OPT). This slows down the matching
3053           process, but does ensure that callouts such as the  example  above  are
3054           obeyed.
3055    
3056    
3057  THE CALLOUT INTERFACE  THE CALLOUT INTERFACE
3058    
3059         During matching, when PCRE reaches a callout point, the external  func-         During  matching, when PCRE reaches a callout point, the external func-
3060         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
3061         both the pcre_exec() and the pcre_dfa_exec()  matching  functions.  The         both  the  pcre_exec()  and the pcre_dfa_exec() matching functions. The
3062         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
3063         block. This structure contains the following fields:         block. This structure contains the following fields:
3064    
3065           int          version;           int         version;
3066           int          callout_number;           int         callout_number;
3067           int         *offset_vector;           int        *offset_vector;
3068           const char  *subject;           const char *subject;
3069           int          subject_length;           int         subject_length;
3070           int          start_match;           int         start_match;
3071           int          current_position;           int         current_position;
3072           int          capture_top;           int         capture_top;
3073           int          capture_last;           int         capture_last;
3074           void        *callout_data;           void       *callout_data;
3075           int          pattern_position;           int         pattern_position;
3076           int          next_item_length;           int         next_item_length;
3077             const unsigned char *mark;
3078         The version field is an integer containing the version  number  of  the  
3079         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
3080         version number will change again in future  if  additional  fields  are         block format. The initial version was 0; the current version is 2.  The
3081           version  number  will  change  again in future if additional fields are
3082         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.
3083    
3084         The callout_number field contains the number of the  callout,  as  com-         The callout_number field contains the number of the  callout,  as  com-
# Line 2596  THE CALLOUT INTERFACE Line 3137  THE CALLOUT INTERFACE
3137         in  distinguishing between different automatic callouts, which all have         in  distinguishing between different automatic callouts, which all have
3138         the same callout number. However, they are set for all callouts.         the same callout number. However, they are set for all callouts.
3139    
3140           The mark field is present from version 2 of the pcre_callout structure.
3141           In  callouts  from pcre_exec() it contains a pointer to the zero-termi-
3142           nated name of the most recently passed (*MARK) item in  the  match,  or
3143           NULL if there are no (*MARK)s in the current matching path. In callouts
3144           from pcre_dfa_exec() this field always contains NULL.
3145    
3146    
3147  RETURN VALUES  RETURN VALUES
3148    
# Line 2604  RETURN VALUES Line 3151  RETURN VALUES
3151         zero, matching fails at the current point, but  the  testing  of  other         zero, matching fails at the current point, but  the  testing  of  other
3152         matching possibilities goes ahead, just as if a lookahead assertion had         matching possibilities goes ahead, just as if a lookahead assertion had
3153         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
3154         pcre_exec() (or pcre_dfa_exec()) returns the negative value.         pcre_exec() or pcre_dfa_exec() returns the negative value.
3155    
3156         Negative   values   should   normally   be   chosen  from  the  set  of         Negative   values   should   normally   be   chosen  from  the  set  of
3157         PCRE_ERROR_xxx values. In particular, PCRE_ERROR_NOMATCH forces a stan-         PCRE_ERROR_xxx values. In particular, PCRE_ERROR_NOMATCH forces a stan-
# Line 2622  AUTHOR Line 3169  AUTHOR
3169    
3170  REVISION  REVISION
3171    
3172         Last updated: 29 May 2007         Last updated: 26 August 2011
3173         Copyright (c) 1997-2007 University of Cambridge.         Copyright (c) 1997-2011 University of Cambridge.
3174  ------------------------------------------------------------------------------  ------------------------------------------------------------------------------
3175    
3176    
# Line 2637  NAME Line 3184  NAME
3184  DIFFERENCES BETWEEN PCRE AND PERL  DIFFERENCES BETWEEN PCRE AND PERL
3185    
3186         This  document describes the differences in the ways that PCRE and Perl         This  document describes the differences in the ways that PCRE and Perl
3187         handle regular expressions. The differences described here  are  mainly         handle regular expressions. The differences  described  here  are  with
3188         with  respect  to  Perl 5.8, though PCRE versions 7.0 and later contain         respect to Perl versions 5.10 and above.
3189         some features that are expected to be in the forthcoming Perl 5.10.  
3190           1.  PCRE has only a subset of Perl's UTF-8 and Unicode support. Details
3191         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.
3192         of  what  it does have are given in the section on UTF-8 support in the  
3193         main pcre page.         2. PCRE allows repeat quantifiers only on parenthesized assertions, but
3194           they  do  not mean what you might think. For example, (?!a){3} does not
3195         2. PCRE does not allow repeat quantifiers on lookahead assertions. Perl         assert that the next three characters are not "a". It just asserts that
3196         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
3197         (?!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
3198         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.
3199    
3200         3.  Capturing  subpatterns  that occur inside negative lookahead asser-         3.  Capturing  subpatterns  that occur inside negative lookahead asser-
3201         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 2663  DIFFERENCES BETWEEN PCRE AND PERL Line 3210  DIFFERENCES BETWEEN PCRE AND PERL
3210         the pattern to represent a binary zero.         the pattern to represent a binary zero.
3211    
3212         5.  The  following Perl escape sequences are not supported: \l, \u, \L,         5.  The  following Perl escape sequences are not supported: \l, \u, \L,
3213         \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
3214         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
3215         are encountered by PCRE, an error is generated.         are implemented by Perl's general string-handling and are not  part  of
3216           its  pattern  matching engine. If any of these are encountered by PCRE,
3217           an error is generated.
3218    
3219         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
3220         is  built  with Unicode character property support. The properties that         is  built  with Unicode character property support. The properties that
3221         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-
3222         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
3223         derived properties Any and L&.         derived properties Any and L&. PCRE does  support  the  Cs  (surrogate)
3224           property,  which  Perl  does  not; the Perl documentation says "Because
3225         7. PCRE does support the \Q...\E escape for quoting substrings. Charac-         Perl hides the need for the user to understand the internal representa-
3226         ters  in  between  are  treated as literals. This is slightly different         tion  of Unicode characters, there is no need to implement the somewhat
3227         from Perl in that $ and @ are  also  handled  as  literals  inside  the         messy concept of surrogates."
3228         quotes.  In Perl, they cause variable interpolation (but of course PCRE  
3229           7. PCRE implements a simpler version of \X than Perl, which changed  to
3230           make  \X  match what Unicode calls an "extended grapheme cluster". This
3231           is more complicated than an extended Unicode sequence,  which  is  what
3232           PCRE matches.
3233    
3234           8. PCRE does support the \Q...\E escape for quoting substrings. Charac-
3235           ters in between are treated as literals.  This  is  slightly  different
3236           from  Perl  in  that  $  and  @ are also handled as literals inside the
3237           quotes. In Perl, they cause variable interpolation (but of course  PCRE
3238         does not have variables). Note the following examples:         does not have variables). Note the following examples:
3239    
3240             Pattern            PCRE matches      Perl matches             Pattern            PCRE matches      Perl matches
# Line 2686  DIFFERENCES BETWEEN PCRE AND PERL Line 3244  DIFFERENCES BETWEEN PCRE AND PERL
3244             \Qabc\$xyz\E       abc\$xyz          abc\$xyz             \Qabc\$xyz\E       abc\$xyz          abc\$xyz
3245             \Qabc\E\$\Qxyz\E   abc$xyz           abc$xyz             \Qabc\E\$\Qxyz\E   abc$xyz           abc$xyz
3246    
3247         The \Q...\E sequence is recognized both inside  and  outside  character         The  \Q...\E  sequence  is recognized both inside and outside character
3248         classes.         classes.
3249    
3250         8. Fairly obviously, PCRE does not support the (?{code}) and (??{code})         9. Fairly obviously, PCRE does not support the (?{code}) and (??{code})
3251         constructions. However, there is support for recursive  patterns.  This         constructions.  However,  there is support for recursive patterns. This
3252         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
3253         "callout" feature allows an external function to be called during  pat-         "callout"  feature allows an external function to be called during pat-
3254         tern matching. See the pcrecallout documentation for details.         tern matching. See the pcrecallout documentation for details.
3255    
3256         9.  Subpatterns  that  are  called  recursively or as "subroutines" are         10. Subpatterns that are called recursively  or  as  "subroutines"  are
3257         always treated as atomic groups in  PCRE.  This  is  like  Python,  but         always  treated  as  atomic  groups  in  PCRE. This is like Python, but
3258         unlike Perl.         unlike Perl. There is a discussion of an example that explains this  in
3259           more  detail  in  the section on recursion differences from Perl in the
3260         10.  There are some differences that are concerned with the settings of         pcrepattern page.
3261         captured strings when part of  a  pattern  is  repeated.  For  example,  
3262         matching  "aba"  against  the  pattern  /^(a(b)?)+$/  in Perl leaves $2         11. There are some differences that are concerned with the settings  of
3263           captured  strings  when  part  of  a  pattern is repeated. For example,
3264           matching "aba" against the  pattern  /^(a(b)?)+$/  in  Perl  leaves  $2
3265         unset, but in PCRE it is set to "b".         unset, but in PCRE it is set to "b".
3266    
3267         11.  PCRE  does  support  Perl  5.10's  backtracking  verbs  (*ACCEPT),         12.  PCRE's handling of duplicate subpattern numbers and duplicate sub-
3268         (*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
3269         the forms without an  argument.  PCRE  does  not  support  (*MARK).  If         fact the PCRE works internally just with numbers, using an external ta-
3270         (*ACCEPT)  is within capturing parentheses, PCRE does not set that cap-         ble to translate between numbers and names. In  particular,  a  pattern
3271         ture group; this is different to Perl.         such  as  (?|(?<a>A)|(?<b)B),  where the two capturing parentheses have
3272           the same number but different names, is not supported,  and  causes  an
3273         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
3274         ities.   Perl  5.10  will  include new features that are not in earlier         distinguish which parentheses matched, because both names map  to  cap-
3275         versions, some of which (such as named parentheses) have been  in  PCRE         turing subpattern number 1. To avoid this confusing situation, an error
3276         for some time. This list is with respect to Perl 5.10:         is given at compile time.
3277    
3278         (a)  Although  lookbehind  assertions  must match fixed length strings,         13. Perl recognizes comments in some places that  PCRE  does  not,  for
3279         each alternative branch of a lookbehind assertion can match a different         example,  between  the  ( and ? at the start of a subpattern. If the /x
3280         length of string. Perl requires them all to have the same length.         modifier is set, Perl allows whitespace between ( and ? but PCRE  never
3281           does, even if the PCRE_EXTENDED option is set.
3282    
3283           14. PCRE provides some extensions to the Perl regular expression facil-
3284           ities.  Perl 5.10 includes new features that are not  in  earlier  ver-
3285           sions  of  Perl, some of which (such as named parentheses) have been in
3286           PCRE for some time. This list is with respect to Perl 5.10:
3287    
3288           (a) Although lookbehind assertions in  PCRE  must  match  fixed  length
3289           strings,  each alternative branch of a lookbehind assertion can match a
3290           different length of string. Perl requires them all  to  have  the  same
3291           length.
3292    
3293         (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 $
3294         meta-character matches only at the very end of the string.         meta-character matches only at the very end of the string.
# Line 2733  DIFFERENCES BETWEEN PCRE AND PERL Line 3304  DIFFERENCES BETWEEN PCRE AND PERL
3304         (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
3305         tried only at the first matching position in the subject string.         tried only at the first matching position in the subject string.
3306    
3307         (f)  The PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY, and PCRE_NO_AUTO_CAP-         (f) The PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY, PCRE_NOTEMPTY_ATSTART,
3308         TURE options for pcre_exec() have no Perl equivalents.         and PCRE_NO_AUTO_CAPTURE options for pcre_exec() have no  Perl  equiva-
3309           lents.
3310    
3311         (g) The callout facility is PCRE-specific.         (g)  The  \R escape sequence can be restricted to match only CR, LF, or
3312           CRLF by the PCRE_BSR_ANYCRLF option.
3313    
3314         (h) The partial matching facility is PCRE-specific.         (h) The callout facility is PCRE-specific.
3315    
3316         (i) Patterns compiled by PCRE can be saved and re-used at a later time,         (i) The partial matching facility is PCRE-specific.
3317    
3318           (j) Patterns compiled by PCRE can be saved and re-used at a later time,
3319         even on different hosts that have the other endianness.         even on different hosts that have the other endianness.
3320    
3321         (j)  The  alternative  matching function (pcre_dfa_exec()) matches in a         (k)  The  alternative  matching function (pcre_dfa_exec()) matches in a
3322         different way and is not Perl-compatible.         different way and is not Perl-compatible.
3323    
3324           (l) PCRE recognizes some special sequences such as (*CR) at  the  start
3325           of a pattern that set overall options that cannot be changed within the
3326           pattern.
3327    
3328    
3329  AUTHOR  AUTHOR
3330    
# Line 2756  AUTHOR Line 3335  AUTHOR
3335    
3336  REVISION  REVISION
3337    
3338         Last updated: 08 August 2007         Last updated: 24 August 2011
3339         Copyright (c) 1997-2007 University of Cambridge.         Copyright (c) 1997-2011 University of Cambridge.
3340  ------------------------------------------------------------------------------  ------------------------------------------------------------------------------
3341    
3342    
# Line 2772  PCRE REGULAR EXPRESSION DETAILS Line 3351  PCRE REGULAR EXPRESSION DETAILS
3351    
3352         The  syntax and semantics of the regular expressions that are supported         The  syntax and semantics of the regular expressions that are supported
3353         by PCRE are described in detail below. There is a quick-reference  syn-         by PCRE are described in detail below. There is a quick-reference  syn-
3354         tax  summary  in  the  pcresyntax  page. Perl's regular expressions are         tax summary in the pcresyntax page. PCRE tries to match Perl syntax and
3355         described in its own documentation, and regular expressions in  general         semantics as closely as it can. PCRE  also  supports  some  alternative
3356         are  covered in a number of books, some of which have copious examples.         regular  expression  syntax (which does not conflict with the Perl syn-
3357         Jeffrey  Friedl's  "Mastering  Regular   Expressions",   published   by         tax) in order to provide some compatibility with regular expressions in
3358         O'Reilly,  covers regular expressions in great detail. This description         Python, .NET, and Oniguruma.
3359         of PCRE's regular expressions is intended as reference material.  
3360           Perl's  regular expressions are described in its own documentation, and
3361           regular expressions in general are covered in a number of  books,  some
3362           of  which  have  copious  examples. Jeffrey Friedl's "Mastering Regular
3363           Expressions", published by  O'Reilly,  covers  regular  expressions  in
3364           great  detail.  This  description  of  PCRE's  regular  expressions  is
3365           intended as reference material.
3366    
3367         The original operation of PCRE was on strings of  one-byte  characters.         The original operation of PCRE was on strings of  one-byte  characters.
3368         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
3369         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
3370         pcre_compile()  with  the  PCRE_UTF8  option.  How this affects pattern         pcre_compile()  or  pcre_compile2() with the PCRE_UTF8 option. There is
3371         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:
3372         of  UTF-8  features  in  the  section on UTF-8 support in the main pcre  
3373             (*UTF8)
3374    
3375           Starting a pattern with this sequence  is  equivalent  to  setting  the
3376           PCRE_UTF8  option.  This  feature  is  not Perl-compatible. How setting
3377           UTF-8 mode affects pattern matching  is  mentioned  in  several  places
3378           below.  There  is  also  a summary of UTF-8 features in the pcreunicode
3379         page.         page.
3380    
3381         The remainder of this document discusses the  patterns  that  are  sup-         Another special sequence that may appear at the start of a  pattern  or
3382         ported  by  PCRE when its main matching function, pcre_exec(), is used.         in combination with (*UTF8) is:
3383         From  release  6.0,   PCRE   offers   a   second   matching   function,  
3384         pcre_dfa_exec(),  which matches using a different algorithm that is not           (*UCP)
3385    
3386           This  has  the  same  effect  as setting the PCRE_UCP option: it causes
3387           sequences such as \d and \w to  use  Unicode  properties  to  determine
3388           character types, instead of recognizing only characters with codes less
3389           than 128 via a lookup table.
3390    
3391           If a pattern starts with (*NO_START_OPT), it has  the  same  effect  as
3392           setting the PCRE_NO_START_OPTIMIZE option either at compile or matching
3393           time. There are also some more of these special sequences that are con-
3394           cerned with the handling of newlines; they are described below.
3395    
3396           The  remainder  of  this  document discusses the patterns that are sup-
3397           ported by PCRE when its main matching function, pcre_exec(),  is  used.
3398           From   release   6.0,   PCRE   offers   a   second  matching  function,
3399           pcre_dfa_exec(), which matches using a different algorithm that is  not
3400         Perl-compatible. Some of the features discussed below are not available         Perl-compatible. Some of the features discussed below are not available
3401         when  pcre_dfa_exec()  is used. The advantages and disadvantages of the         when pcre_dfa_exec() is used. The advantages and disadvantages  of  the
3402         alternative function, and how it differs from the normal function,  are         alternative  function, and how it differs from the normal function, are
3403         discussed in the pcrematching page.         discussed in the pcrematching page.
3404    
3405    
3406    NEWLINE CONVENTIONS
3407    
3408           PCRE supports five different conventions for indicating line breaks  in
3409           strings:  a  single  CR (carriage return) character, a single LF (line-
3410           feed) character, the two-character sequence CRLF, any of the three pre-
3411           ceding,  or  any Unicode newline sequence. The pcreapi page has further
3412           discussion about newlines, and shows how to set the newline  convention
3413           in the options arguments for the compiling and matching functions.
3414    
3415           It  is also possible to specify a newline convention by starting a pat-
3416           tern string with one of the following five sequences:
3417    
3418             (*CR)        carriage return
3419             (*LF)        linefeed
3420             (*CRLF)      carriage return, followed by linefeed
3421             (*ANYCRLF)   any of the three above
3422             (*ANY)       all Unicode newline sequences
3423    
3424           These override the default and the options given to  pcre_compile()  or
3425           pcre_compile2().  For example, on a Unix system where LF is the default
3426           newline sequence, the pattern
3427    
3428             (*CR)a.b
3429    
3430           changes the convention to CR. That pattern matches "a\nb" because LF is
3431           no  longer  a  newline. Note that these special settings, which are not
3432           Perl-compatible, are recognized only at the very start  of  a  pattern,
3433           and  that  they  must  be  in  upper  case. If more than one of them is
3434           present, the last one is used.
3435    
3436           The newline convention affects the interpretation of the dot  metachar-
3437           acter  when  PCRE_DOTALL is not set, and also the behaviour of \N. How-
3438           ever, it does not affect  what  the  \R  escape  sequence  matches.  By
3439           default,  this is any Unicode newline sequence, for Perl compatibility.
3440           However, this can be changed; see the description of \R in the  section
3441           entitled  "Newline sequences" below. A change of \R setting can be com-
3442           bined with a change of newline convention.
3443    
3444    
3445  CHARACTERS AND METACHARACTERS  CHARACTERS AND METACHARACTERS
3446    
3447         A  regular  expression  is  a pattern that is matched against a subject         A regular expression is a pattern that is  matched  against  a  subject
3448         string from left to right. Most characters stand for  themselves  in  a         string  from  left  to right. Most characters stand for themselves in a
3449         pattern,  and  match  the corresponding characters in the subject. As a         pattern, and match the corresponding characters in the  subject.  As  a
3450         trivial example, the pattern         trivial example, the pattern
3451    
3452           The quick brown fox           The quick brown fox
3453    
3454         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
3455         caseless  matching is specified (the PCRE_CASELESS option), letters are         caseless matching is specified (the PCRE_CASELESS option), letters  are
3456         matched independently of case. In UTF-8 mode, PCRE  always  understands         matched  independently  of case. In UTF-8 mode, PCRE always understands
3457         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
3458         caseless matching is always possible. For characters with  higher  val-         caseless  matching  is always possible. For characters with higher val-
3459         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
3460         property support, but not otherwise.   If  you  want  to  use  caseless         property  support,  but  not  otherwise.   If  you want to use caseless
3461         matching  for  characters  128  and above, you must ensure that PCRE is         matching for characters 128 and above, you must  ensure  that  PCRE  is
3462         compiled with Unicode property support as well as with UTF-8 support.         compiled with Unicode property support as well as with UTF-8 support.
3463    
3464         The power of regular expressions comes  from  the  ability  to  include         The  power  of  regular  expressions  comes from the ability to include
3465         alternatives  and  repetitions in the pattern. These are encoded in the         alternatives and repetitions in the pattern. These are encoded  in  the
3466         pattern by the use of metacharacters, which do not stand for themselves         pattern by the use of metacharacters, which do not stand for themselves
3467         but instead are interpreted in some special way.         but instead are interpreted in some special way.
3468    
3469         There  are  two different sets of metacharacters: those that are recog-         There are two different sets of metacharacters: those that  are  recog-
3470         nized anywhere in the pattern except within square brackets, and  those         nized  anywhere in the pattern except within square brackets, and those
3471         that  are  recognized  within square brackets. Outside square brackets,         that are recognized within square brackets.  Outside  square  brackets,
3472         the metacharacters are as follows:         the metacharacters are as follows:
3473    
3474           \      general escape character with several uses           \      general escape character with several uses
# Line 2842  CHARACTERS AND METACHARACTERS Line 3487  CHARACTERS AND METACHARACTERS
3487                  also "possessive quantifier"                  also "possessive quantifier"
3488           {      start min/max quantifier           {      start min/max quantifier
3489    
3490         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
3491         class". In a character class the only metacharacters are:         class". In a character class the only metacharacters are:
3492    
3493           \      general escape character           \      general escape character
# Line 2852  CHARACTERS AND METACHARACTERS Line 3497  CHARACTERS AND METACHARACTERS
3497                    syntax)                    syntax)
3498           ]      terminates the character class           ]      terminates the character class
3499    
3500         The  following sections describe the use of each of the metacharacters.         The following sections describe the use of each of the metacharacters.
3501    
3502    
3503  BACKSLASH  BACKSLASH
3504    
3505         The backslash character has several uses. Firstly, if it is followed by         The backslash character has several uses. Firstly, if it is followed by
3506         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
3507         character may have. This  use  of  backslash  as  an  escape  character         meaning that character may have. This use of  backslash  as  an  escape
3508         applies both inside and outside character classes.         character applies both inside and outside character classes.
3509    
3510         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
3511         pattern.  This escaping action applies whether  or  not  the  following         pattern.  This escaping action applies whether  or  not  the  following
# Line 2869  BACKSLASH Line 3514  BACKSLASH
3514         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-
3515         slash, you write \\.         slash, you write \\.
3516    
3517           In UTF-8 mode, only ASCII numbers and letters have any special  meaning
3518           after  a  backslash.  All  other characters (in particular, those whose
3519           codepoints are greater than 127) are treated as literals.
3520    
3521         If a pattern is compiled with the PCRE_EXTENDED option,  whitespace  in         If a pattern is compiled with the PCRE_EXTENDED option,  whitespace  in
3522         the  pattern (other than in a character class) and characters between a         the  pattern (other than in a character class) and characters between a
3523         # outside a character class and the next newline are ignored. An escap-         # outside a character class and the next newline are ignored. An escap-
# Line 2889  BACKSLASH Line 3538  BACKSLASH
3538           \Qabc\E\$\Qxyz\E   abc$xyz        abc$xyz           \Qabc\E\$\Qxyz\E   abc$xyz        abc$xyz
3539    
3540         The \Q...\E sequence is recognized both inside  and  outside  character         The \Q...\E sequence is recognized both inside  and  outside  character
3541         classes.         classes.   An  isolated \E that is not preceded by \Q is ignored. If \Q
3542           is not followed by \E later in the pattern, the literal  interpretation
3543           continues  to  the  end  of  the pattern (that is, \E is assumed at the
3544           end). If the isolated \Q is inside a character class,  this  causes  an
3545           error, because the character class is not terminated.
3546    
3547     Non-printing characters     Non-printing characters
3548    
# Line 2897  BACKSLASH Line 3550  BACKSLASH
3550         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
3551         appearance  of non-printing characters, apart from the binary zero that         appearance  of non-printing characters, apart from the binary zero that
3552         terminates a pattern, but when a pattern  is  being  prepared  by  text         terminates a pattern, but when a pattern  is  being  prepared  by  text
3553         editing,  it  is  usually  easier  to  use  one of the following escape         editing,  it  is  often  easier  to  use  one  of  the following escape
3554         sequences than the binary character it represents:         sequences than the binary character it represents:
3555    
3556           \a        alarm, that is, the BEL character (hex 07)           \a        alarm, that is, the BEL character (hex 07)
3557           \cx       "control-x", where x is any character           \cx       "control-x", where x is any ASCII character
3558           \e        escape (hex 1B)           \e        escape (hex 1B)
3559           \f        formfeed (hex 0C)           \f        formfeed (hex 0C)
3560           \n        newline (hex 0A)           \n        linefeed (hex 0A)
3561           \r        carriage return (hex 0D)           \r        carriage return (hex 0D)
3562           \t        tab (hex 09)           \t        tab (hex 09)
3563           \ddd      character with octal code ddd, or backreference           \ddd      character with octal code ddd, or back reference
3564           \xhh      character with hex code hh           \xhh      character with hex code hh
3565           \x{hhh..} character with hex code hhh..           \x{hhh..} character with hex code hhh..
3566    
3567         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,
3568         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
3569         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 ({
3570         becomes hex 7B.         is  7B),  while  \c; becomes hex 7B (; is 3B). If the byte following \c
3571           has a value greater than 127, a compile-time error occurs.  This  locks
3572           out  non-ASCII  characters in both byte mode and UTF-8 mode. (When PCRE
3573           is compiled in EBCDIC mode, all byte values are  valid.  A  lower  case
3574           letter is converted to upper case, and then the 0xc0 bits are flipped.)
3575    
3576         After  \x, from zero to two hexadecimal digits are read (letters can be         After  \x, from zero to two hexadecimal digits are read (letters can be
3577         in upper or lower case). Any number of hexadecimal  digits  may  appear         in upper or lower case). Any number of hexadecimal  digits  may  appear
# Line 2976  BACKSLASH Line 3633  BACKSLASH
3633         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
3634         inside and outside character classes. In addition, inside  a  character         inside and outside character classes. In addition, inside  a  character
3635         class,  the  sequence \b is interpreted as the backspace character (hex         class,  the  sequence \b is interpreted as the backspace character (hex
3636         08), and the sequences \R and \X are interpreted as the characters  "R"         08). The sequences \B, \N, \R, and \X are not special inside a  charac-
3637         and  "X", respectively. Outside a character class, these sequences have         ter  class.  Like  any  other  unrecognized  escape sequences, they are
3638         different meanings (see below).         treated as the literal characters "B", "N", "R", and  "X"  by  default,
3639           but cause an error if the PCRE_EXTRA option is set. Outside a character
3640           class, these sequences have different meanings.
3641    
3642     Absolute and relative back references     Absolute and relative back references
3643    
# Line 2987  BACKSLASH Line 3646  BACKSLASH
3646         named back reference can be coded as \g{name}. Back references are dis-         named back reference can be coded as \g{name}. Back references are dis-
3647         cussed later, following the discussion of parenthesized subpatterns.         cussed later, following the discussion of parenthesized subpatterns.
3648    
3649       Absolute and relative subroutine calls
3650    
3651           For  compatibility with Oniguruma, the non-Perl syntax \g followed by a
3652           name or a number enclosed either in angle brackets or single quotes, is
3653           an  alternative  syntax for referencing a subpattern as a "subroutine".
3654           Details are discussed later.   Note  that  \g{...}  (Perl  syntax)  and
3655           \g<...>  (Oniguruma  syntax)  are  not synonymous. The former is a back
3656           reference; the latter is a subroutine call.
3657    
3658     Generic character types     Generic character types
3659    
3660         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:  
3661    
3662           \d     any decimal digit           \d     any decimal digit
3663           \D     any character that is not a decimal digit           \D     any character that is not a decimal digit
# Line 3003