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2  This file contains a concatenation of the PCRE man pages, converted to plain  This file contains a concatenation of the PCRE man pages, converted to plain
3  text format for ease of searching with a text editor, or for use on systems  text format for ease of searching with a text editor, or for use on systems
4  that do not have a man page processor. The small individual files that give  that do not have a man page processor. The small individual files that give
5  synopses of each function in the library have not been included. There are  synopses of each function in the library have not been included. Neither has
6  separate text files for the pcregrep and pcretest commands.  the pcredemo program. There are separate text files for the pcregrep and
7    pcretest commands.
8  -----------------------------------------------------------------------------  -----------------------------------------------------------------------------
9    
10    
# Line 18  INTRODUCTION Line 19  INTRODUCTION
19    
20         The  PCRE  library is a set of functions that implement regular expres-         The  PCRE  library is a set of functions that implement regular expres-
21         sion pattern matching using the same syntax and semantics as Perl, with         sion pattern matching using the same syntax and semantics as Perl, with
22         just  a  few differences. (Certain features that appeared in Python and         just  a few differences. Some features that appeared in Python and PCRE
23         PCRE before they appeared in Perl are also available using  the  Python         before they appeared in Perl are also available using the  Python  syn-
24         syntax.)         tax,  there  is  some  support for one or two .NET and Oniguruma syntax
25           items, and there is an option for requesting some  minor  changes  that
26         The  current  implementation of PCRE (release 7.x) corresponds approxi-         give better JavaScript compatibility.
27         mately with Perl 5.10, including support for UTF-8 encoded strings  and  
28         Unicode general category properties. However, UTF-8 and Unicode support         Starting with release 8.30, it is possible to compile two separate PCRE
29         has to be explicitly enabled; it is not the default. The Unicode tables         libraries:  the  original,  which  supports  8-bit  character   strings
30         correspond to Unicode release 5.0.0.         (including  UTF-8  strings),  and a second library that supports 16-bit
31           character strings (including UTF-16 strings). The build process  allows
32           either  one  or both to be built. The majority of the work to make this
33           possible was done by Zoltan Herczeg.
34    
35           The two libraries contain identical sets of functions, except that  the
36           names  in  the  16-bit  library start with pcre16_ instead of pcre_. To
37           avoid over-complication and reduce the documentation maintenance  load,
38           most of the documentation describes the 8-bit library, with the differ-
39           ences for the 16-bit library described separately in the  pcre16  page.
40           References  to  functions or structures of the form pcre[16]_xxx should
41           be  read  as  meaning  "pcre_xxx  when  using  the  8-bit  library  and
42           pcre16_xxx when using the 16-bit library".
43    
44           The  current implementation of PCRE corresponds approximately with Perl
45           5.12, including support for UTF-8/16 encoded strings and  Unicode  gen-
46           eral  category properties. However, UTF-8/16 and Unicode support has to
47           be explicitly enabled; it is not the default. The Unicode tables corre-
48           spond to Unicode release 6.0.0.
49    
50         In  addition to the Perl-compatible matching function, PCRE contains an         In  addition to the Perl-compatible matching function, PCRE contains an
51         alternative matching function that matches the same  compiled  patterns         alternative function that matches the same compiled patterns in a  dif-
52         in  a different way. In certain circumstances, the alternative function         ferent way. In certain circumstances, the alternative function has some
53         has some advantages. For a discussion of the two  matching  algorithms,         advantages.  For a discussion of the two matching algorithms,  see  the
54         see the pcrematching page.         pcrematching page.
55    
56         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
57         have written wrappers and interfaces of various kinds.  In  particular,         have written wrappers and interfaces of various kinds.  In  particular,
58         Google  Inc.   have  provided  a comprehensive C++ wrapper. This is now         Google  Inc.   have  provided a comprehensive C++ wrapper for the 8-bit
59         included as part of the PCRE distribution. The pcrecpp page has details         library. This is now included as part of  the  PCRE  distribution.  The
60         of  this  interface.  Other  people's contributions can be found in the         pcrecpp  page  has  details of this interface. Other people's contribu-
61         Contrib directory at the primary FTP site, which is:         tions can be found in the Contrib directory at the  primary  FTP  site,
62           which is:
63    
64         ftp://ftp.csx.cam.ac.uk/pub/software/programming/pcre         ftp://ftp.csx.cam.ac.uk/pub/software/programming/pcre
65    
66         Details of exactly which Perl regular expression features are  and  are         Details  of  exactly which Perl regular expression features are and are
67         not supported by PCRE are given in separate documents. See the pcrepat-         not supported by PCRE are given in separate documents. See the pcrepat-
68         tern and pcrecompat pages. There is a syntax summary in the  pcresyntax         tern  and pcrecompat pages. There is a syntax summary in the pcresyntax
69         page.         page.
70    
71         Some  features  of  PCRE can be included, excluded, or changed when the         Some features of PCRE can be included, excluded, or  changed  when  the
72         library is built. The pcre_config() function makes it  possible  for  a         library  is  built.  The pcre_config() function makes it possible for a
73         client  to  discover  which  features are available. The features them-         client to discover which features are  available.  The  features  them-
74         selves are described in the pcrebuild page. Documentation about  build-         selves  are described in the pcrebuild page. Documentation about build-
75         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
76         in the source distribution.         NON-UNIX-USE files in the source distribution.
77    
78         The library contains a number of undocumented  internal  functions  and         The  libraries contains a number of undocumented internal functions and
79         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
80         functions, but which are not intended  for  use  by  external  callers.         functions,  but  which  are  not  intended for use by external callers.
81         Their  names  all begin with "_pcre_", which hopefully will not provoke         Their names all begin with "_pcre_" or "_pcre16_", which hopefully will
82         any name clashes. In some environments, it is possible to control which         not  provoke  any name clashes. In some environments, it is possible to
83         external  symbols  are  exported when a shared library is built, and in         control which external symbols are exported when a  shared  library  is
84         these cases the undocumented symbols are not exported.         built, and in these cases the undocumented symbols are not exported.
85    
86    
87  USER DOCUMENTATION  USER DOCUMENTATION
88    
89         The user documentation for PCRE comprises a number  of  different  sec-         The  user  documentation  for PCRE comprises a number of different sec-
90         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
91         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.
92         In  the  plain text format, all the sections are concatenated, for ease         In the plain text format, all the sections, except  the  pcredemo  sec-
93         of searching. The sections are as follows:         tion, are concatenated, for ease of searching. The sections are as fol-
94           lows:
95    
96           pcre              this document           pcre              this document
97             pcre16            details of the 16-bit library
98           pcre-config       show PCRE installation configuration information           pcre-config       show PCRE installation configuration information
99           pcreapi           details of PCRE's native C API           pcreapi           details of PCRE's native C API
100           pcrebuild         options for building PCRE           pcrebuild         options for building PCRE
101           pcrecallout       details of the callout feature           pcrecallout       details of the callout feature
102           pcrecompat        discussion of Perl compatibility           pcrecompat        discussion of Perl compatibility
103           pcrecpp           details of the C++ wrapper           pcrecpp           details of the C++ wrapper for the 8-bit library
104           pcregrep          description of the pcregrep command           pcredemo          a demonstration C program that uses PCRE
105             pcregrep          description of the pcregrep command (8-bit only)
106             pcrejit           discussion of the just-in-time optimization support
107             pcrelimits        details of size and other limits
108           pcrematching      discussion of the two matching algorithms           pcrematching      discussion of the two matching algorithms
109           pcrepartial       details of the partial matching facility           pcrepartial       details of the partial matching facility
110           pcrepattern       syntax and semantics of supported           pcrepattern       syntax and semantics of supported
111                               regular expressions                               regular expressions
          pcresyntax        quick syntax reference  
112           pcreperform       discussion of performance issues           pcreperform       discussion of performance issues
113           pcreposix         the POSIX-compatible C API           pcreposix         the POSIX-compatible C API for the 8-bit library
114           pcreprecompile    details of saving and re-using precompiled patterns           pcreprecompile    details of saving and re-using precompiled patterns
115           pcresample        discussion of the sample program           pcresample        discussion of the pcredemo program
116           pcrestack         discussion of stack usage           pcrestack         discussion of stack usage
117             pcresyntax        quick syntax reference
118           pcretest          description of the pcretest testing command           pcretest          description of the pcretest testing command
119             pcreunicode       discussion of Unicode and UTF-8/16 support
120    
121         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
122         each C library function, listing its arguments and results.         each 8-bit C library function, listing its arguments and results.
123    
124    
125  LIMITATIONS  AUTHOR
126    
127         There are some size limitations in PCRE but it is hoped that they  will         Philip Hazel
128         never in practice be relevant.         University Computing Service
129           Cambridge CB2 3QH, England.
130    
131         The  maximum  length of a compiled pattern is 65539 (sic) bytes if PCRE         Putting  an actual email address here seems to have been a spam magnet,
132         is compiled with the default internal linkage size of 2. If you want to         so I've taken it away. If you want to email me, use  my  two  initials,
133         process  regular  expressions  that are truly enormous, you can compile         followed by the two digits 10, at the domain cam.ac.uk.
        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.  
134    
        All values in repeating quantifiers must be less than 65536.  
135    
136         There is no limit to the number of parenthesized subpatterns, but there  REVISION
        can be no more than 65535 capturing subpatterns.  
137    
138         The maximum length of name for a named subpattern is 32 characters, and         Last updated: 10 January 2012
139         the maximum number of named subpatterns is 10000.         Copyright (c) 1997-2012 University of Cambridge.
140    ------------------------------------------------------------------------------
141    
        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.  
142    
143    PCRE(3)                                                                PCRE(3)
144    
 UTF-8 AND UNICODE PROPERTY SUPPORT  
145    
146         From release 3.3, PCRE has  had  some  support  for  character  strings  NAME
147         encoded  in the UTF-8 format. For release 4.0 this was greatly extended         PCRE - Perl-compatible regular expressions
        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.  
148    
149         If  you compile PCRE with UTF-8 support, but do not use it at run time,         #include <pcre.h>
        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.  
150    
        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.  
151    
152     Validity of UTF-8 strings  PCRE 16-BIT API BASIC FUNCTIONS
153    
154         When you set the PCRE_UTF8 flag, the strings  passed  as  patterns  and         pcre16 *pcre16_compile(PCRE_SPTR16 pattern, int options,
155         subjects are (by default) checked for validity on entry to the relevant              const char **errptr, int *erroffset,
156         functions. From release 7.3 of PCRE, the check is according  the  rules              const unsigned char *tableptr);
        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.  
157    
158         If you pass an invalid UTF-8 string  when  PCRE_NO_UTF8_CHECK  is  set,         pcre16 *pcre16_compile2(PCRE_SPTR16 pattern, int options,
159         what  happens  depends on why the string is invalid. If the string con-              int *errorcodeptr,
160         forms to the "old" definition of UTF-8 (RFC 2279), it is processed as a              const char **errptr, int *erroffset,
161         string  of  characters  in  the  range 0 to 0x7FFFFFFF. In other words,              const unsigned char *tableptr);
        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.  
162    
163         If  you  want  to  process  strings  of  values  in the full range 0 to         pcre16_extra *pcre16_study(const pcre16 *code, int options,
164         0x7FFFFFFF, encoded in a UTF-8-like manner as per the old RFC, you  can              const char **errptr);
        set PCRE_NO_UTF8_CHECK to bypass the more restrictive test. However, in  
        this situation, you will have to apply your own validity check.  
165    
166     General comments about UTF-8 mode         void pcre16_free_study(pcre16_extra *extra);
167    
168         1. An unbraced hexadecimal escape sequence (such  as  \xb3)  matches  a         int pcre16_exec(const pcre16 *code, const pcre16_extra *extra,
169         two-byte UTF-8 character if the value is greater than 127.              PCRE_SPTR16 subject, int length, int startoffset,
170                int options, int *ovector, int ovecsize);
171    
172         2.  Octal  numbers  up to \777 are recognized, and match two-byte UTF-8         int pcre16_dfa_exec(const pcre16 *code, const pcre16_extra *extra,
173         characters for values greater than \177.              PCRE_SPTR16 subject, int length, int startoffset,
174                int options, int *ovector, int ovecsize,
175                int *workspace, int wscount);
176    
        3. Repeat quantifiers apply to complete UTF-8 characters, not to  indi-  
        vidual bytes, for example: \x{100}{3}.  
177    
178         4.  The dot metacharacter matches one UTF-8 character instead of a sin-  PCRE 16-BIT API STRING EXTRACTION FUNCTIONS
        gle byte.  
179    
180         5. The escape sequence \C can be used to match a single byte  in  UTF-8         int pcre16_copy_named_substring(const pcre16 *code,
181         mode,  but  its  use can lead to some strange effects. This facility is              PCRE_SPTR16 subject, int *ovector,
182         not available in the alternative matching function, pcre_dfa_exec().              int stringcount, PCRE_SPTR16 stringname,
183                PCRE_UCHAR16 *buffer, int buffersize);
184    
185         6. The character escapes \b, \B, \d, \D, \s, \S, \w, and  \W  correctly         int pcre16_copy_substring(PCRE_SPTR16 subject, int *ovector,
186         test  characters of any code value, but the characters that PCRE recog-              int stringcount, int stringnumber, PCRE_UCHAR16 *buffer,
187         nizes as digits, spaces, or word characters  remain  the  same  set  as              int buffersize);
188         before, all with values less than 256. This remains true even when PCRE  
189         includes Unicode property support, because to do otherwise  would  slow         int pcre16_get_named_substring(const pcre16 *code,
190         down  PCRE in many common cases. If you really want to test for a wider              PCRE_SPTR16 subject, int *ovector,
191         sense of, say, "digit", you must use Unicode  property  tests  such  as              int stringcount, PCRE_SPTR16 stringname,
192         \p{Nd}.              PCRE_SPTR16 *stringptr);
193    
194         7.  Similarly,  characters that match the POSIX named character classes         int pcre16_get_stringnumber(const pcre16 *code,
195         are all low-valued characters.              PCRE_SPTR16 name);
196    
197         8. However, the Perl 5.10 horizontal and vertical  whitespace  matching         int pcre16_get_stringtable_entries(const pcre16 *code,
198         escapes (\h, \H, \v, and \V) do match all the appropriate Unicode char-              PCRE_SPTR16 name, PCRE_UCHAR16 **first, PCRE_UCHAR16 **last);
199         acters.  
200           int pcre16_get_substring(PCRE_SPTR16 subject, int *ovector,
201         9. Case-insensitive matching applies only to  characters  whose  values              int stringcount, int stringnumber,
202         are  less than 128, unless PCRE is built with Unicode property support.              PCRE_SPTR16 *stringptr);
203         Even when Unicode property support is available, PCRE  still  uses  its  
204         own  character  tables when checking the case of low-valued characters,         int pcre16_get_substring_list(PCRE_SPTR16 subject,
205         so as not to degrade performance.  The Unicode property information  is              int *ovector, int stringcount, PCRE_SPTR16 **listptr);
206         used only for characters with higher values. Even when Unicode property  
207         support is available, PCRE supports case-insensitive matching only when         void pcre16_free_substring(PCRE_SPTR16 stringptr);
208         there  is  a  one-to-one  mapping between a letter's cases. There are a  
209         small number of many-to-one mappings in Unicode;  these  are  not  sup-         void pcre16_free_substring_list(PCRE_SPTR16 *stringptr);
210         ported by PCRE.  
211    
212    PCRE 16-BIT API AUXILIARY FUNCTIONS
213    
214           pcre16_jit_stack *pcre16_jit_stack_alloc(int startsize, int maxsize);
215    
216           void pcre16_jit_stack_free(pcre16_jit_stack *stack);
217    
218           void pcre16_assign_jit_stack(pcre16_extra *extra,
219                pcre16_jit_callback callback, void *data);
220    
221           const unsigned char *pcre16_maketables(void);
222    
223           int pcre16_fullinfo(const pcre16 *code, const pcre16_extra *extra,
224                int what, void *where);
225    
226           int pcre16_refcount(pcre16 *code, int adjust);
227    
228           int pcre16_config(int what, void *where);
229    
230           const char *pcre16_version(void);
231    
232           int pcre16_pattern_to_host_byte_order(pcre16 *code,
233                pcre16_extra *extra, const unsigned char *tables);
234    
235    
236    PCRE 16-BIT API INDIRECTED FUNCTIONS
237    
238           void *(*pcre16_malloc)(size_t);
239    
240           void (*pcre16_free)(void *);
241    
242           void *(*pcre16_stack_malloc)(size_t);
243    
244           void (*pcre16_stack_free)(void *);
245    
246           int (*pcre16_callout)(pcre16_callout_block *);
247    
248    
249    PCRE 16-BIT API 16-BIT-ONLY FUNCTION
250    
251           int pcre16_utf16_to_host_byte_order(PCRE_UCHAR16 *output,
252                PCRE_SPTR16 input, int length, int *byte_order,
253                int keep_boms);
254    
255    
256    THE PCRE 16-BIT LIBRARY
257    
258           Starting  with  release  8.30, it is possible to compile a PCRE library
259           that supports 16-bit character strings, including  UTF-16  strings,  as
260           well  as  or instead of the original 8-bit library. The majority of the
261           work to make  this  possible  was  done  by  Zoltan  Herczeg.  The  two
262           libraries contain identical sets of functions, used in exactly the same
263           way. Only the names of the functions and the data types of their  argu-
264           ments  and results are different. To avoid over-complication and reduce
265           the documentation maintenance load,  most  of  the  PCRE  documentation
266           describes  the  8-bit  library,  with only occasional references to the
267           16-bit library. This page describes what is different when you use  the
268           16-bit library.
269    
270           WARNING:  A  single  application can be linked with both libraries, but
271           you must take care when processing any particular pattern to use  func-
272           tions  from  just one library. For example, if you want to study a pat-
273           tern that was compiled with  pcre16_compile(),  you  must  do  so  with
274           pcre16_study(), not pcre_study(), and you must free the study data with
275           pcre16_free_study().
276    
277    
278    THE HEADER FILE
279    
280           There is only one header file, pcre.h. It contains prototypes  for  all
281           the  functions  in  both  libraries,  as  well as definitions of flags,
282           structures, error codes, etc.
283    
284    
285    THE LIBRARY NAME
286    
287           In Unix-like systems, the 16-bit library is called libpcre16,  and  can
288           normally  be  accesss  by adding -lpcre16 to the command for linking an
289           application that uses PCRE.
290    
291    
292    STRING TYPES
293    
294           In the 8-bit library, strings are passed to PCRE library  functions  as
295           vectors  of  bytes  with  the  C  type "char *". In the 16-bit library,
296           strings are passed as vectors of unsigned 16-bit quantities. The  macro
297           PCRE_UCHAR16  specifies  an  appropriate  data type, and PCRE_SPTR16 is
298           defined as "const PCRE_UCHAR16 *". In very  many  environments,  "short
299           int" is a 16-bit data type. When PCRE is built, it defines PCRE_UCHAR16
300           as "short int", but checks that it really is a 16-bit data type. If  it
301           is not, the build fails with an error message telling the maintainer to
302           modify the definition appropriately.
303    
304    
305    STRUCTURE TYPES
306    
307           The types of the opaque structures that are used  for  compiled  16-bit
308           patterns  and  JIT stacks are pcre16 and pcre16_jit_stack respectively.
309           The  type  of  the  user-accessible  structure  that  is  returned   by
310           pcre16_study()  is  pcre16_extra, and the type of the structure that is
311           used for passing data to a callout  function  is  pcre16_callout_block.
312           These structures contain the same fields, with the same names, as their
313           8-bit counterparts. The only difference is that pointers  to  character
314           strings are 16-bit instead of 8-bit types.
315    
316    
317    16-BIT FUNCTIONS
318    
319           For  every function in the 8-bit library there is a corresponding func-
320           tion in the 16-bit library with a name that starts with pcre16_ instead
321           of  pcre_.  The  prototypes are listed above. In addition, there is one
322           extra function, pcre16_utf16_to_host_byte_order(). This  is  a  utility
323           function  that converts a UTF-16 character string to host byte order if
324           necessary. The other 16-bit  functions  expect  the  strings  they  are
325           passed to be in host byte order.
326    
327           The input and output arguments of pcre16_utf16_to_host_byte_order() may
328           point to the same address, that is, conversion in place  is  supported.
329           The output buffer must be at least as long as the input.
330    
331           The  length  argument  specifies the number of 16-bit data units in the
332           input string; a negative value specifies a zero-terminated string.
333    
334           If byte_order is NULL, it is assumed that the string starts off in host
335           byte  order. This may be changed by byte-order marks (BOMs) anywhere in
336           the string (commonly as the first character).
337    
338           If byte_order is not NULL, a non-zero value of the integer to which  it
339           points  means  that  the input starts off in host byte order, otherwise
340           the opposite order is assumed. Again, BOMs in  the  string  can  change
341           this. The final byte order is passed back at the end of processing.
342    
343           If  keep_boms  is  not  zero,  byte-order  mark characters (0xfeff) are
344           copied into the output string. Otherwise they are discarded.
345    
346           The result of the function is the number of 16-bit  units  placed  into
347           the  output  buffer,  including  the  zero terminator if the string was
348           zero-terminated.
349    
350    
351    SUBJECT STRING OFFSETS
352    
353           The offsets within subject strings that are returned  by  the  matching
354           functions are in 16-bit units rather than bytes.
355    
356    
357    NAMED SUBPATTERNS
358    
359           The  name-to-number translation table that is maintained for named sub-
360           patterns uses 16-bit characters.  The  pcre16_get_stringtable_entries()
361           function returns the length of each entry in the table as the number of
362           16-bit data units.
363    
364    
365    OPTION NAMES
366    
367           There   are   two   new   general   option   names,   PCRE_UTF16    and
368           PCRE_NO_UTF16_CHECK,     which     correspond    to    PCRE_UTF8    and
369           PCRE_NO_UTF8_CHECK in the 8-bit library. In  fact,  these  new  options
370           define the same bits in the options word.
371    
372           For  the  pcre16_config() function there is an option PCRE_CONFIG_UTF16
373           that returns 1 if UTF-16 support is configured, otherwise  0.  If  this
374           option  is given to pcre_config(), or if the PCRE_CONFIG_UTF8 option is
375           given to pcre16_config(), the result is the PCRE_ERROR_BADOPTION error.
376    
377    
378    CHARACTER CODES
379    
380           In 16-bit mode, when  PCRE_UTF16  is  not  set,  character  values  are
381           treated in the same way as in 8-bit, non UTF-8 mode, except, of course,
382           that they can range from 0 to 0xffff instead of 0  to  0xff.  Character
383           types  for characters less than 0xff can therefore be influenced by the
384           locale in the same way as before.  Characters greater  than  0xff  have
385           only one case, and no "type" (such as letter or digit).
386    
387           In  UTF-16  mode,  the  character  code  is  Unicode, in the range 0 to
388           0x10ffff, with the exception of values in the range  0xd800  to  0xdfff
389           because  those  are "surrogate" values that are used in pairs to encode
390           values greater than 0xffff.
391    
392           A UTF-16 string can indicate its endianness by special code knows as  a
393           byte-order mark (BOM). The PCRE functions do not handle this, expecting
394           strings  to  be  in  host  byte  order.  A  utility   function   called
395           pcre16_utf16_to_host_byte_order()  is  provided  to help with this (see
396           above).
397    
398    
399    ERROR NAMES
400    
401           The errors PCRE_ERROR_BADUTF16_OFFSET and PCRE_ERROR_SHORTUTF16  corre-
402           spond  to  their  8-bit  counterparts.  The error PCRE_ERROR_BADMODE is
403           given when a compiled pattern is passed to a  function  that  processes
404           patterns  in  the  other  mode, for example, if a pattern compiled with
405           pcre_compile() is passed to pcre16_exec().
406    
407           There are new error codes whose names  begin  with  PCRE_UTF16_ERR  for
408           invalid  UTF-16  strings,  corresponding to the PCRE_UTF8_ERR codes for
409           UTF-8 strings that are described in the section entitled "Reason  codes
410           for  invalid UTF-8 strings" in the main pcreapi page. The UTF-16 errors
411           are:
412    
413             PCRE_UTF16_ERR1  Missing low surrogate at end of string
414             PCRE_UTF16_ERR2  Invalid low surrogate follows high surrogate
415             PCRE_UTF16_ERR3  Isolated low surrogate
416             PCRE_UTF16_ERR4  Invalid character 0xfffe
417    
418    
419    ERROR TEXTS
420    
421           If there is an error while compiling a pattern, the error text that  is
422           passed  back by pcre16_compile() or pcre16_compile2() is still an 8-bit
423           character string, zero-terminated.
424    
425    
426    CALLOUTS
427    
428           The subject and mark fields in the callout block that is  passed  to  a
429           callout function point to 16-bit vectors.
430    
431    
432    TESTING
433    
434           The  pcretest  program continues to operate with 8-bit input and output
435           files, but it can be used for testing the 16-bit library. If it is  run
436           with the command line option -16, patterns and subject strings are con-
437           verted from 8-bit to 16-bit before being passed to PCRE, and the 16-bit
438           library  functions  are used instead of the 8-bit ones. Returned 16-bit
439           strings are converted to 8-bit for output. If the 8-bit library was not
440           compiled, pcretest defaults to 16-bit and the -16 option is ignored.
441    
442           When  PCRE  is  being built, the RunTest script that is called by "make
443           check" uses the pcretest -C option to discover which of the  8-bit  and
444           16-bit libraries has been built, and runs the tests appropriately.
445    
446    
447    NOT SUPPORTED IN 16-BIT MODE
448    
449           Not all the features of the 8-bit library are available with the 16-bit
450           library. The C++ and POSIX wrapper functions  support  only  the  8-bit
451           library, and the pcregrep program is at present 8-bit only.
452    
453    
454  AUTHOR  AUTHOR
# Line 249  AUTHOR Line 457  AUTHOR
457         University Computing Service         University Computing Service
458         Cambridge CB2 3QH, England.         Cambridge CB2 3QH, England.
459    
        Putting  an actual email address here seems to have been a spam magnet,  
        so I've taken it away. If you want to email me, use  my  two  initials,  
        followed by the two digits 10, at the domain cam.ac.uk.  
   
460    
461  REVISION  REVISION
462    
463         Last updated: 09 August 2007         Last updated: 08 January 2012
464         Copyright (c) 1997-2007 University of Cambridge.         Copyright (c) 1997-2012 University of Cambridge.
465  ------------------------------------------------------------------------------  ------------------------------------------------------------------------------
466    
467    
# Line 271  NAME Line 475  NAME
475  PCRE BUILD-TIME OPTIONS  PCRE BUILD-TIME OPTIONS
476    
477         This  document  describes  the  optional  features  of PCRE that can be         This  document  describes  the  optional  features  of PCRE that can be
478         selected when the library is compiled. They are all selected, or  dese-         selected when the library is compiled. It assumes use of the  configure
479         lected, by providing options to the configure script that is run before         script,  where the optional features are selected or deselected by pro-
480         the make command. The complete list of  options  for  configure  (which         viding options to configure before running the make  command.  However,
481         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
482         directory) can be obtained by running         environments using the GUI facility of cmake-gui if you are using CMake
483           instead of configure to build PCRE.
484    
485           There  is  a  lot more information about building PCRE in non-Unix-like
486           environments in the file called NON_UNIX_USE, which is part of the PCRE
487           distribution.  You  should consult this file as well as the README file
488           if you are building in a non-Unix-like environment.
489    
490           The complete list of options for configure (which includes the standard
491           ones  such  as  the  selection  of  the  installation directory) can be
492           obtained by running
493    
494           ./configure --help           ./configure --help
495    
# Line 287  PCRE BUILD-TIME OPTIONS Line 501  PCRE BUILD-TIME OPTIONS
501         is not described.         is not described.
502    
503    
504    BUILDING 8-BIT and 16-BIT LIBRARIES
505    
506           By  default,  a  library  called libpcre is built, containing functions
507           that take string arguments contained in vectors  of  bytes,  either  as
508           single-byte  characters,  or interpreted as UTF-8 strings. You can also
509           build a separate library, called libpcre16, in which strings  are  con-
510           tained  in  vectors of 16-bit data units and interpreted either as sin-
511           gle-unit characters or UTF-16 strings, by adding
512    
513             --enable-pcre16
514    
515           to the configure command. If you do not want the 8-bit library, add
516    
517             --disable-pcre8
518    
519           as well. At least one of the two libraries must be built. Note that the
520           C++  and  POSIX wrappers are for the 8-bit library only, and that pcre-
521           grep is an 8-bit program. None of these are built if  you  select  only
522           the 16-bit library.
523    
524    
525    BUILDING SHARED AND STATIC LIBRARIES
526    
527           The  PCRE building process uses libtool to build both shared and static
528           Unix libraries by default. You can suppress one of these by adding  one
529           of
530    
531             --disable-shared
532             --disable-static
533    
534           to the configure command, as required.
535    
536    
537  C++ SUPPORT  C++ SUPPORT
538    
539         By default, the configure script will search for a C++ compiler and C++         By  default,  if the 8-bit library is being built, the configure script
540         header files. If it finds them, it automatically builds the C++ wrapper         will search for a C++ compiler and C++ header files. If it finds  them,
541         library for PCRE. You can disable this by adding         it  automatically  builds  the C++ wrapper library (which supports only
542           8-bit strings). You can disable this by adding
543    
544           --disable-cpp           --disable-cpp
545    
546         to the configure command.         to the configure command.
547    
548    
549  UTF-8 SUPPORT  UTF-8 and UTF-16 SUPPORT
550    
551         To build PCRE with support for UTF-8 character strings, add         To build PCRE with support for UTF Unicode character strings, add
552    
553           --enable-utf8           --enable-utf
554    
555         to  the  configure  command.  Of  itself, this does not make PCRE treat         to the configure command.  This  setting  applies  to  both  libraries,
556         strings as UTF-8. As well as compiling PCRE with this option, you  also         adding support for UTF-8 to the 8-bit library and support for UTF-16 to
557         have  have to set the PCRE_UTF8 option when you call the pcre_compile()         the 16-bit library. There are no separate options  for  enabling  UTF-8
558         function.         and  UTF-16  independently because that would allow ridiculous settings
559           such as  requesting  UTF-16  support  while  building  only  the  8-bit
560           library.  It  is not possible to build one library with UTF support and
561           the other without in the same configuration. (For backwards compatibil-
562           ity, --enable-utf8 is a synonym of --enable-utf.)
563    
564           Of  itself,  this  setting does not make PCRE treat strings as UTF-8 or
565           UTF-16. As well as compiling PCRE with this option, you also have  have
566           to set the PCRE_UTF8 or PCRE_UTF16 option when you call one of the pat-
567           tern compiling functions.
568    
569           If you set --enable-utf when compiling in an EBCDIC  environment,  PCRE
570           expects its input to be either ASCII or UTF-8 (depending on the runtime
571           option). It is not possible to support both EBCDIC and UTF-8  codes  in
572           the  same  version  of  the  library.  Consequently,  --enable-utf  and
573           --enable-ebcdic are mutually exclusive.
574    
575    
576  UNICODE CHARACTER PROPERTY SUPPORT  UNICODE CHARACTER PROPERTY SUPPORT
577    
578         UTF-8 support allows PCRE to process character values greater than  255         UTF support allows the libraries to process character codepoints up  to
579         in  the  strings that it handles. On its own, however, it does not pro-         0x10ffff  in the strings that they handle. On its own, however, it does
580         vide any facilities for accessing the properties of such characters. If         not provide any facilities for accessing the properties of such charac-
581         you  want  to  be able to use the pattern escapes \P, \p, and \X, which         ters. If you want to be able to use the pattern escapes \P, \p, and \X,
582         refer to Unicode character properties, you must add         which refer to Unicode character properties, you must add
583    
584           --enable-unicode-properties           --enable-unicode-properties
585    
586         to the configure command. This implies UTF-8 support, even if you  have         to the configure command. This implies UTF support, even  if  you  have
587         not explicitly requested it.         not explicitly requested it.
588    
589         Including  Unicode  property  support  adds around 30K of tables to the         Including  Unicode  property  support  adds around 30K of tables to the
# Line 328  UNICODE CHARACTER PROPERTY SUPPORT Line 591  UNICODE CHARACTER PROPERTY SUPPORT
591         are supported. Details are given in the pcrepattern documentation.         are supported. Details are given in the pcrepattern documentation.
592    
593    
594    JUST-IN-TIME COMPILER SUPPORT
595    
596           Just-in-time compiler support is included in the build by specifying
597    
598             --enable-jit
599    
600           This  support  is available only for certain hardware architectures. If
601           this option is set for an  unsupported  architecture,  a  compile  time
602           error  occurs.   See  the pcrejit documentation for a discussion of JIT
603           usage. When JIT support is enabled, pcregrep automatically makes use of
604           it, unless you add
605    
606             --disable-pcregrep-jit
607    
608           to the "configure" command.
609    
610    
611  CODE VALUE OF NEWLINE  CODE VALUE OF NEWLINE
612    
613         By  default,  PCRE interprets character 10 (linefeed, LF) as indicating         By  default,  PCRE interprets the linefeed (LF) character as indicating
614         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
615         systems. You can compile PCRE to use character 13 (carriage return, CR)         systems.  You  can compile PCRE to use carriage return (CR) instead, by
616         instead, by adding         adding
617    
618           --enable-newline-is-cr           --enable-newline-is-cr
619    
# Line 356  CODE VALUE OF NEWLINE Line 636  CODE VALUE OF NEWLINE
636    
637         causes PCRE to recognize any Unicode newline sequence.         causes PCRE to recognize any Unicode newline sequence.
638    
639         Whatever line ending convention is selected when PCRE is built  can  be         Whatever  line  ending convention is selected when PCRE is built can be
640         overridden  when  the library functions are called. At build time it is         overridden when the library functions are called. At build time  it  is
641         conventional to use the standard for your operating system.         conventional to use the standard for your operating system.
642    
643    
644  BUILDING SHARED AND STATIC LIBRARIES  WHAT \R MATCHES
645    
646         The PCRE building process uses libtool to build both shared and  static         By  default,  the  sequence \R in a pattern matches any Unicode newline
647         Unix  libraries by default. You can suppress one of these by adding one         sequence, whatever has been selected as the line  ending  sequence.  If
648         of         you specify
649    
650           --disable-shared           --enable-bsr-anycrlf
          --disable-static  
651    
652         to the configure command, as required.         the  default  is changed so that \R matches only CR, LF, or CRLF. What-
653           ever is selected when PCRE is built can be overridden when the  library
654           functions are called.
655    
656    
657  POSIX MALLOC USAGE  POSIX MALLOC USAGE
658    
659         When PCRE is called through the POSIX interface (see the pcreposix doc-         When  the  8-bit library is called through the POSIX interface (see the
660         umentation),  additional  working  storage  is required for holding the         pcreposix documentation), additional working storage  is  required  for
661         pointers to capturing substrings, because PCRE requires three  integers         holding  the  pointers  to  capturing substrings, because PCRE requires
662         per  substring,  whereas  the POSIX interface provides only two. If the         three integers per substring, whereas the POSIX interface provides only
663         number of expected substrings is small, the wrapper function uses space         two.  If  the number of expected substrings is small, the wrapper func-
664         on the stack, because this is faster than using malloc() for each call.         tion uses space on the stack, because this is faster  than  using  mal-
665         The default threshold above which the stack is no longer used is 10; it         loc()  for each call. The default threshold above which the stack is no
666         can be changed by adding a setting such as         longer used is 10; it can be changed by adding a setting such as
667    
668           --with-posix-malloc-threshold=20           --with-posix-malloc-threshold=20
669    
# Line 391  POSIX MALLOC USAGE Line 672  POSIX MALLOC USAGE
672    
673  HANDLING VERY LARGE PATTERNS  HANDLING VERY LARGE PATTERNS
674    
675         Within  a  compiled  pattern,  offset values are used to point from one         Within a compiled pattern, offset values are used  to  point  from  one
676         part to another (for example, from an opening parenthesis to an  alter-         part  to another (for example, from an opening parenthesis to an alter-
677         nation  metacharacter).  By default, two-byte values are used for these         nation metacharacter). By default, two-byte values are used  for  these
678         offsets, leading to a maximum size for a  compiled  pattern  of  around         offsets,  leading  to  a  maximum size for a compiled pattern of around
679         64K.  This  is sufficient to handle all but the most gigantic patterns.         64K. This is sufficient to handle all but the most  gigantic  patterns.
680         Nevertheless, some people do want to process enormous patterns,  so  it         Nevertheless,  some  people do want to process truly enormous patterns,
681         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-
682         adding a setting such as         sets by adding a setting such as
683    
684           --with-link-size=3           --with-link-size=3
685    
686         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. For the
687         longer  offsets slows down the operation of PCRE because it has to load         16-bit library, a value of 3 is rounded up to 4. Using  longer  offsets
688         additional bytes when handling them.         slows down the operation of PCRE because it has to load additional data
689           when handling them.
690    
691    
692  AVOIDING EXCESSIVE STACK USAGE  AVOIDING EXCESSIVE STACK USAGE
# Line 425  AVOIDING EXCESSIVE STACK USAGE Line 707  AVOIDING EXCESSIVE STACK USAGE
707         to  the  configure  command. With this configuration, PCRE will use the         to  the  configure  command. With this configuration, PCRE will use the
708         pcre_stack_malloc and pcre_stack_free variables to call memory  manage-         pcre_stack_malloc and pcre_stack_free variables to call memory  manage-
709         ment  functions. By default these point to malloc() and free(), but you         ment  functions. By default these point to malloc() and free(), but you
710         can replace the pointers so that your own functions are used.         can replace the pointers so that your own functions are used instead.
711    
712         Separate functions are  provided  rather  than  using  pcre_malloc  and         Separate functions are  provided  rather  than  using  pcre_malloc  and
713         pcre_free  because  the  usage  is  very  predictable:  the block sizes         pcre_free  because  the  usage  is  very  predictable:  the block sizes
# Line 433  AVOIDING EXCESSIVE STACK USAGE Line 715  AVOIDING EXCESSIVE STACK USAGE
715         reverse  order.  A calling program might be able to implement optimized         reverse  order.  A calling program might be able to implement optimized
716         functions that perform better  than  malloc()  and  free().  PCRE  runs         functions that perform better  than  malloc()  and  free().  PCRE  runs
717         noticeably more slowly when built in this way. This option affects only         noticeably more slowly when built in this way. This option affects only
718         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.  
719    
720    
721  LIMITING PCRE RESOURCE USAGE  LIMITING PCRE RESOURCE USAGE
722    
723         Internally,  PCRE has a function called match(), which it calls repeat-         Internally, PCRE has a function called match(), which it calls  repeat-
724         edly  (sometimes  recursively)  when  matching  a  pattern   with   the         edly   (sometimes   recursively)  when  matching  a  pattern  with  the
725         pcre_exec()  function.  By controlling the maximum number of times this         pcre_exec() function. By controlling the maximum number of  times  this
726         function may be called during a single matching operation, a limit  can         function  may be called during a single matching operation, a limit can
727         be  placed  on  the resources used by a single call to pcre_exec(). The         be placed on the resources used by a single call  to  pcre_exec().  The
728         limit can be changed at run time, as described in the pcreapi  documen-         limit  can be changed at run time, as described in the pcreapi documen-
729         tation.  The default is 10 million, but this can be changed by adding a         tation. The default is 10 million, but this can be changed by adding  a
730         setting such as         setting such as
731    
732           --with-match-limit=500000           --with-match-limit=500000
733    
734         to  the  configure  command.  This  setting  has  no  effect   on   the         to   the   configure  command.  This  setting  has  no  effect  on  the
735         pcre_dfa_exec() matching function.         pcre_dfa_exec() matching function.
736    
737         In  some  environments  it is desirable to limit the depth of recursive         In some environments it is desirable to limit the  depth  of  recursive
738         calls of match() more strictly than the total number of calls, in order         calls of match() more strictly than the total number of calls, in order
739         to  restrict  the maximum amount of stack (or heap, if --disable-stack-         to restrict the maximum amount of stack (or heap,  if  --disable-stack-
740         for-recursion is specified) that is used. A second limit controls this;         for-recursion is specified) that is used. A second limit controls this;
741         it  defaults  to  the  value  that is set for --with-match-limit, which         it defaults to the value that  is  set  for  --with-match-limit,  which
742         imposes no additional constraints. However, you can set a  lower  limit         imposes  no  additional constraints. However, you can set a lower limit
743         by adding, for example,         by adding, for example,
744    
745           --with-match-limit-recursion=10000           --with-match-limit-recursion=10000
746    
747         to  the  configure  command.  This  value can also be overridden at run         to the configure command. This value can  also  be  overridden  at  run
748         time.         time.
749    
750    
751  CREATING CHARACTER TABLES AT BUILD TIME  CREATING CHARACTER TABLES AT BUILD TIME
752    
753         PCRE uses fixed tables for processing characters whose code values  are         PCRE  uses fixed tables for processing characters whose code values are
754         less  than 256. By default, PCRE is built with a set of tables that are         less than 256. By default, PCRE is built with a set of tables that  are
755         distributed in the file pcre_chartables.c.dist. These  tables  are  for         distributed  in  the  file pcre_chartables.c.dist. These tables are for
756         ASCII codes only. If you add         ASCII codes only. If you add
757    
758           --enable-rebuild-chartables           --enable-rebuild-chartables
759    
760         to  the  configure  command, the distributed tables are no longer used.         to the configure command, the distributed tables are  no  longer  used.
761         Instead, a program called dftables is compiled and  run.  This  outputs         Instead,  a  program  called dftables is compiled and run. This outputs
762         the source for new set of tables, created in the default locale of your         the source for new set of tables, created in the default locale of your
763         C runtime system. (This method of replacing the tables does not work if         C runtime system. (This method of replacing the tables does not work if
764         you  are cross compiling, because dftables is run on the local host. If         you are cross compiling, because dftables is run on the local host.  If
765         you need to create alternative tables when cross  compiling,  you  will         you  need  to  create alternative tables when cross compiling, you will
766         have to do so "by hand".)         have to do so "by hand".)
767    
768    
769  USING EBCDIC CODE  USING EBCDIC CODE
770    
771         PCRE  assumes  by  default that it will run in an environment where the         PCRE assumes by default that it will run in an  environment  where  the
772         character code is ASCII (or Unicode, which is  a  superset  of  ASCII).         character  code  is  ASCII  (or Unicode, which is a superset of ASCII).
773         This  is  the  case for most computer operating systems. PCRE can, how-         This is the case for most computer operating systems.  PCRE  can,  how-
774         ever, be compiled to run in an EBCDIC environment by adding         ever, be compiled to run in an EBCDIC environment by adding
775    
776           --enable-ebcdic           --enable-ebcdic
777    
778         to the configure command. This setting implies --enable-rebuild-charta-         to the configure command. This setting implies --enable-rebuild-charta-
779         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
780         environment (for example, an IBM mainframe operating system).         environment  (for  example,  an  IBM  mainframe  operating system). The
781           --enable-ebcdic option is incompatible with --enable-utf.
782    
783    
784    PCREGREP OPTIONS FOR COMPRESSED FILE SUPPORT
785    
786           By default, pcregrep reads all files as plain text. You can build it so
787           that it recognizes files whose names end in .gz or .bz2, and reads them
788           with libz or libbz2, respectively, by adding one or both of
789    
790             --enable-pcregrep-libz
791             --enable-pcregrep-libbz2
792    
793           to the configure command. These options naturally require that the rel-
794           evant  libraries  are installed on your system. Configuration will fail
795           if they are not.
796    
797    
798    PCREGREP BUFFER SIZE
799    
800           pcregrep uses an internal buffer to hold a "window" on the file  it  is
801           scanning, in order to be able to output "before" and "after" lines when
802           it finds a match. The size of the buffer is controlled by  a  parameter
803           whose default value is 20K. The buffer itself is three times this size,
804           but because of the way it is used for holding "before" lines, the long-
805           est  line  that  is guaranteed to be processable is the parameter size.
806           You can change the default parameter value by adding, for example,
807    
808             --with-pcregrep-bufsize=50K
809    
810           to the configure command. The caller of pcregrep can, however, override
811           this value by specifying a run-time option.
812    
813    
814    PCRETEST OPTION FOR LIBREADLINE SUPPORT
815    
816           If you add
817    
818             --enable-pcretest-libreadline
819    
820           to  the  configure  command,  pcretest  is  linked with the libreadline
821           library, and when its input is from a terminal, it reads it  using  the
822           readline() function. This provides line-editing and history facilities.
823           Note that libreadline is GPL-licensed, so if you distribute a binary of
824           pcretest linked in this way, there may be licensing issues.
825    
826           Setting  this  option  causes  the -lreadline option to be added to the
827           pcretest build. In many operating environments with  a  sytem-installed
828           libreadline this is sufficient. However, in some environments (e.g.  if
829           an unmodified distribution version of readline is in use),  some  extra
830           configuration  may  be necessary. The INSTALL file for libreadline says
831           this:
832    
833             "Readline uses the termcap functions, but does not link with the
834             termcap or curses library itself, allowing applications which link
835             with readline the to choose an appropriate library."
836    
837           If your environment has not been set up so that an appropriate  library
838           is automatically included, you may need to add something like
839    
840             LIBS="-ncurses"
841    
842           immediately before the configure command.
843    
844    
845  SEE ALSO  SEE ALSO
846    
847         pcreapi(3), pcre_config(3).         pcreapi(3), pcre16, pcre_config(3).
848    
849    
850  AUTHOR  AUTHOR
# Line 513  AUTHOR Line 856  AUTHOR
856    
857  REVISION  REVISION
858    
859         Last updated: 30 July 2007         Last updated: 07 January 2012
860         Copyright (c) 1997-2007 University of Cambridge.         Copyright (c) 1997-2012 University of Cambridge.
861  ------------------------------------------------------------------------------  ------------------------------------------------------------------------------
862    
863    
# Line 530  PCRE MATCHING ALGORITHMS Line 873  PCRE MATCHING ALGORITHMS
873         This document describes the two different algorithms that are available         This document describes the two different algorithms that are available
874         in PCRE for matching a compiled regular expression against a given sub-         in PCRE for matching a compiled regular expression against a given sub-
875         ject  string.  The  "standard"  algorithm  is  the  one provided by the         ject  string.  The  "standard"  algorithm  is  the  one provided by the
876         pcre_exec() function.  This works in the same was  as  Perl's  matching         pcre_exec() and pcre16_exec() functions. These work in the same was  as
877         function, and provides a Perl-compatible matching operation.         Perl's matching function, and provide a Perl-compatible matching opera-
878           tion. The just-in-time (JIT) optimization  that  is  described  in  the
879         An  alternative  algorithm is provided by the pcre_dfa_exec() function;         pcrejit documentation is compatible with these functions.
880         this operates in a different way, and is not  Perl-compatible.  It  has  
881         advantages  and disadvantages compared with the standard algorithm, and         An  alternative  algorithm  is  provided  by  the  pcre_dfa_exec()  and
882         these are described below.         pcre16_dfa_exec() functions; they operate in a different way,  and  are
883           not  Perl-compatible. This alternative has advantages and disadvantages
884           compared with the standard algorithm, and these are described below.
885    
886         When there is only one possible way in which a given subject string can         When there is only one possible way in which a given subject string can
887         match  a pattern, the two algorithms give the same answer. A difference         match  a pattern, the two algorithms give the same answer. A difference
# Line 601  THE ALTERNATIVE MATCHING ALGORITHM Line 946  THE ALTERNATIVE MATCHING ALGORITHM
946         though  it is not implemented as a traditional finite state machine (it         though  it is not implemented as a traditional finite state machine (it
947         keeps multiple states active simultaneously).         keeps multiple states active simultaneously).
948    
949           Although the general principle of this matching algorithm  is  that  it
950           scans  the subject string only once, without backtracking, there is one
951           exception: when a lookaround assertion is encountered,  the  characters
952           following  or  preceding  the  current  point  have to be independently
953           inspected.
954    
955         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
956         there  are  no more unterminated paths. At this point, terminated paths         there  are  no more unterminated paths. At this point, terminated paths
957         represent the different matching possibilities (if there are none,  the         represent the different matching possibilities (if there are none,  the
958         match  has  failed).   Thus,  if there is more than one possible match,         match  has  failed).   Thus,  if there is more than one possible match,
959         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-
960         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
961         match (which is necessarily the shortest) has been found.         an option to stop the algorithm after the first match (which is  neces-
962           sarily the shortest) is found.
963    
964         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
965         subject. If the pattern         subject. If the pattern
966    
967           cat(er(pillar)?)           cat(er(pillar)?)?
968    
969         is  matched  against the string "the caterpillar catchment", the result         is matched against the string "the caterpillar catchment",  the  result
970         will be the three strings "cat", "cater", and "caterpillar" that  start         will  be the three strings "caterpillar", "cater", and "cat" that start
971         at the fourth character of the subject. The algorithm does not automat-         at the fifth character of the subject. The algorithm does not automati-
972         ically move on to find matches that start at later positions.         cally move on to find matches that start at later positions.
973    
974         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
975         supported by the alternative matching algorithm. They are as follows:         supported by the alternative matching algorithm. They are as follows:
976    
977         1.  Because  the  algorithm  finds  all possible matches, the greedy or         1. Because the algorithm finds all  possible  matches,  the  greedy  or
978         ungreedy nature of repetition quantifiers is not relevant.  Greedy  and         ungreedy  nature  of repetition quantifiers is not relevant. Greedy and
979         ungreedy quantifiers are treated in exactly the same way. However, pos-         ungreedy quantifiers are treated in exactly the same way. However, pos-
980         sessive quantifiers can make a difference when what follows could  also         sessive  quantifiers can make a difference when what follows could also
981         match what is quantified, for example in a pattern like this:         match what is quantified, for example in a pattern like this:
982    
983           ^a++\w!           ^a++\w!
984    
985         This  pattern matches "aaab!" but not "aaa!", which would be matched by         This pattern matches "aaab!" but not "aaa!", which would be matched  by
986         a non-possessive quantifier. Similarly, if an atomic group is  present,         a  non-possessive quantifier. Similarly, if an atomic group is present,
987         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,
988         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
989         pattern.         pattern.
990    
991         2. When dealing with multiple paths through the tree simultaneously, it         2. When dealing with multiple paths through the tree simultaneously, it
992         is not straightforward to keep track of  captured  substrings  for  the         is  not  straightforward  to  keep track of captured substrings for the
993         different  matching  possibilities,  and  PCRE's implementation of this         different matching possibilities, and  PCRE's  implementation  of  this
994         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-
995         strings are available.         strings are available.
996    
997         3.  Because no substrings are captured, back references within the pat-         3. Because no substrings are captured, back references within the  pat-
998         tern are not supported, and cause errors if encountered.         tern are not supported, and cause errors if encountered.
999    
1000         4. For the same reason, conditional expressions that use  a  backrefer-         4.  For  the same reason, conditional expressions that use a backrefer-
1001         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
1002         supported.         supported.
1003    
1004         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
1005         sequence, which resets the start of the match when encountered (but may         sequence, which resets the start of the match when encountered (but may
1006         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
1007         error if encountered.         error if encountered.
1008    
1009         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
1010         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.
1011    
1012         7. The \C escape sequence, which (in the standard algorithm) matches  a         7.  The  \C  escape  sequence, which (in the standard algorithm) always
1013         single  byte, even in UTF-8 mode, is not supported because the alterna-         matches a single data unit, even in UTF-8 or UTF-16 modes, is not  sup-
1014         tive algorithm moves through the subject  string  one  character  at  a         ported  in these modes, because the alternative algorithm moves through
1015         time, for all active paths through the tree.         the subject string one character (not data unit) at  a  time,  for  all
1016           active paths through the tree.
1017         8.  None  of  the  backtracking control verbs such as (*PRUNE) are sup-  
1018         ported.         8.  Except for (*FAIL), the backtracking control verbs such as (*PRUNE)
1019           are not supported. (*FAIL) is supported, and  behaves  like  a  failing
1020           negative assertion.
1021    
1022    
1023  ADVANTAGES OF THE ALTERNATIVE ALGORITHM  ADVANTAGES OF THE ALTERNATIVE ALGORITHM
1024    
1025         Using the alternative matching algorithm provides the following  advan-         Using  the alternative matching algorithm provides the following advan-
1026         tages:         tages:
1027    
1028         1. All possible matches (at a single point in the subject) are automat-         1. All possible matches (at a single point in the subject) are automat-
1029         ically found, and in particular, the longest match is  found.  To  find         ically  found,  and  in particular, the longest match is found. To find
1030         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
1031         things with callouts.         things with callouts.
1032    
1033         2. There is much better support for partial matching. The  restrictions         2.  Because  the  alternative  algorithm  scans the subject string just
1034         on  the content of the pattern that apply when using the standard algo-         once, and never needs to backtrack (except for lookbehinds), it is pos-
1035         rithm for partial matching do not apply to the  alternative  algorithm.         sible  to  pass  very  long subject strings to the matching function in
1036         For  non-anchored patterns, the starting position of a partial match is         several pieces, checking for partial matching each time. Although it is
1037         available.         possible  to  do multi-segment matching using the standard algorithm by
1038           retaining partially matched substrings, it  is  more  complicated.  The
1039         3. Because the alternative algorithm  scans  the  subject  string  just         pcrepartial  documentation  gives  details of partial matching and dis-
1040         once,  and  never  needs to backtrack, it is possible to pass very long         cusses multi-segment matching.
        subject strings to the matching function in  several  pieces,  checking  
        for partial matching each time.  
1041    
1042    
1043  DISADVANTAGES OF THE ALTERNATIVE ALGORITHM  DISADVANTAGES OF THE ALTERNATIVE ALGORITHM
1044    
1045         The alternative algorithm suffers from a number of disadvantages:         The alternative algorithm suffers from a number of disadvantages:
1046    
1047         1.  It  is  substantially  slower  than the standard algorithm. This is         1. It is substantially slower than  the  standard  algorithm.  This  is
1048         partly because it has to search for all possible matches, but  is  also         partly  because  it has to search for all possible matches, but is also
1049         because it is less susceptible to optimization.         because it is less susceptible to optimization.
1050    
1051         2. Capturing parentheses and back references are not supported.         2. Capturing parentheses and back references are not supported.
# Line 711  AUTHOR Line 1063  AUTHOR
1063    
1064  REVISION  REVISION
1065    
1066         Last updated: 08 August 2007         Last updated: 08 January 2012
1067         Copyright (c) 1997-2007 University of Cambridge.         Copyright (c) 1997-2012 University of Cambridge.
1068  ------------------------------------------------------------------------------  ------------------------------------------------------------------------------
1069    
1070    
# Line 722  PCREAPI(3) Line 1074  PCREAPI(3)
1074  NAME  NAME
1075         PCRE - Perl-compatible regular expressions         PCRE - Perl-compatible regular expressions
1076    
1077           #include <pcre.h>
1078    
 PCRE NATIVE API  
1079    
1080         #include <pcre.h>  PCRE NATIVE API BASIC FUNCTIONS
1081    
1082         pcre *pcre_compile(const char *pattern, int options,         pcre *pcre_compile(const char *pattern, int options,
1083              const char **errptr, int *erroffset,              const char **errptr, int *erroffset,
# Line 739  PCRE NATIVE API Line 1091  PCRE NATIVE API
1091         pcre_extra *pcre_study(const pcre *code, int options,         pcre_extra *pcre_study(const pcre *code, int options,
1092              const char **errptr);              const char **errptr);
1093    
1094           void pcre_free_study(pcre_extra *extra);
1095    
1096         int pcre_exec(const pcre *code, const pcre_extra *extra,         int pcre_exec(const pcre *code, const pcre_extra *extra,
1097              const char *subject, int length, int startoffset,              const char *subject, int length, int startoffset,
1098              int options, int *ovector, int ovecsize);              int options, int *ovector, int ovecsize);
# Line 748  PCRE NATIVE API Line 1102  PCRE NATIVE API
1102              int options, int *ovector, int ovecsize,              int options, int *ovector, int ovecsize,
1103              int *workspace, int wscount);              int *workspace, int wscount);
1104    
1105    
1106    PCRE NATIVE API STRING EXTRACTION FUNCTIONS
1107    
1108         int pcre_copy_named_substring(const pcre *code,         int pcre_copy_named_substring(const pcre *code,
1109              const char *subject, int *ovector,              const char *subject, int *ovector,
1110              int stringcount, const char *stringname,              int stringcount, const char *stringname,
# Line 779  PCRE NATIVE API Line 1136  PCRE NATIVE API
1136    
1137         void pcre_free_substring_list(const char **stringptr);         void pcre_free_substring_list(const char **stringptr);
1138    
1139    
1140    PCRE NATIVE API AUXILIARY FUNCTIONS
1141    
1142           pcre_jit_stack *pcre_jit_stack_alloc(int startsize, int maxsize);
1143    
1144           void pcre_jit_stack_free(pcre_jit_stack *stack);
1145    
1146           void pcre_assign_jit_stack(pcre_extra *extra,
1147                pcre_jit_callback callback, void *data);
1148    
1149         const unsigned char *pcre_maketables(void);         const unsigned char *pcre_maketables(void);
1150    
1151         int pcre_fullinfo(const pcre *code, const pcre_extra *extra,         int pcre_fullinfo(const pcre *code, const pcre_extra *extra,
1152              int what, void *where);              int what, void *where);
1153    
        int pcre_info(const pcre *code, int *optptr, int *firstcharptr);  
   
1154         int pcre_refcount(pcre *code, int adjust);         int pcre_refcount(pcre *code, int adjust);
1155    
1156         int pcre_config(int what, void *where);         int pcre_config(int what, void *where);
1157    
1158         char *pcre_version(void);         const char *pcre_version(void);
1159    
1160           int pcre_pattern_to_host_byte_order(pcre *code,
1161                pcre_extra *extra, const unsigned char *tables);
1162    
1163    
1164    PCRE NATIVE API INDIRECTED FUNCTIONS
1165    
1166         void *(*pcre_malloc)(size_t);         void *(*pcre_malloc)(size_t);
1167    
# Line 803  PCRE NATIVE API Line 1174  PCRE NATIVE API
1174         int (*pcre_callout)(pcre_callout_block *);         int (*pcre_callout)(pcre_callout_block *);
1175    
1176    
1177    PCRE 8-BIT AND 16-BIT LIBRARIES
1178    
1179           From  release  8.30,  PCRE  can  be  compiled as a library for handling
1180           16-bit character strings as  well  as,  or  instead  of,  the  original
1181           library that handles 8-bit character strings. To avoid too much compli-
1182           cation, this document describes the 8-bit versions  of  the  functions,
1183           with only occasional references to the 16-bit library.
1184    
1185           The  16-bit  functions  operate in the same way as their 8-bit counter-
1186           parts; they just use different  data  types  for  their  arguments  and
1187           results, and their names start with pcre16_ instead of pcre_. For every
1188           option that has UTF8 in its name (for example, PCRE_UTF8), there  is  a
1189           corresponding 16-bit name with UTF8 replaced by UTF16. This facility is
1190           in fact just cosmetic; the 16-bit option names define the same bit val-
1191           ues.
1192    
1193           References to bytes and UTF-8 in this document should be read as refer-
1194           ences to 16-bit data  quantities  and  UTF-16  when  using  the  16-bit
1195           library,  unless specified otherwise. More details of the specific dif-
1196           ferences for the 16-bit library are given in the pcre16 page.
1197    
1198    
1199  PCRE API OVERVIEW  PCRE API OVERVIEW
1200    
1201         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
1202         are also some wrapper functions that correspond to  the  POSIX  regular         are  also some wrapper functions (for the 8-bit library only) that cor-
1203         expression  API.  These  are  described in the pcreposix documentation.         respond to the POSIX regular expression  API,  but  they  do  not  give
1204         Both of these APIs define a set of C function calls. A C++  wrapper  is         access  to  all  the functionality. They are described in the pcreposix
1205         distributed with PCRE. It is documented in the pcrecpp page.         documentation. Both of these APIs define a set of C function  calls.  A
1206           C++ wrapper (again for the 8-bit library only) is also distributed with
1207         The  native  API  C  function prototypes are defined in the header file         PCRE. It is documented in the pcrecpp page.
1208         pcre.h, and on Unix systems the library itself is called  libpcre.   It  
1209         can normally be accessed by adding -lpcre to the command for linking an         The native API C function prototypes are defined  in  the  header  file
1210         application  that  uses  PCRE.  The  header  file  defines  the  macros         pcre.h,  and  on Unix-like systems the (8-bit) library itself is called
1211         PCRE_MAJOR  and  PCRE_MINOR to contain the major and minor release num-         libpcre. It can normally be accessed by adding -lpcre  to  the  command
1212         bers for the library.  Applications can use these  to  include  support         for  linking an application that uses PCRE. The header file defines the
1213           macros PCRE_MAJOR and PCRE_MINOR to contain the major and minor release
1214           numbers  for the library. Applications can use these to include support
1215         for different releases of PCRE.         for different releases of PCRE.
1216    
1217         The   functions   pcre_compile(),  pcre_compile2(),  pcre_study(),  and         In a Windows environment, if you want to statically link an application
1218         pcre_exec() are used for compiling and matching regular expressions  in         program  against  a  non-dll  pcre.a  file, you must define PCRE_STATIC
1219         a  Perl-compatible  manner. A sample program that demonstrates the sim-         before including pcre.h or pcrecpp.h, because otherwise  the  pcre_mal-
1220         plest way of using them is provided in the file  called  pcredemo.c  in         loc()   and   pcre_free()   exported   functions   will   be   declared
1221         the  source distribution. The pcresample documentation describes how to         __declspec(dllimport), with unwanted results.
1222         run it.  
1223           The  functions  pcre_compile(),  pcre_compile2(),   pcre_study(),   and
1224           pcre_exec()  are used for compiling and matching regular expressions in
1225           a Perl-compatible manner. A sample program that demonstrates  the  sim-
1226           plest  way  of  using them is provided in the file called pcredemo.c in
1227           the PCRE source distribution. A listing of this program is given in the
1228           pcredemo  documentation, and the pcresample documentation describes how
1229           to compile and run it.
1230    
1231           Just-in-time compiler support is an optional feature of PCRE  that  can
1232           be built in appropriate hardware environments. It greatly speeds up the
1233           matching performance of  many  patterns.  Simple  programs  can  easily
1234           request  that  it  be  used  if available, by setting an option that is
1235           ignored when it is not relevant. More complicated programs  might  need
1236           to     make    use    of    the    functions    pcre_jit_stack_alloc(),
1237           pcre_jit_stack_free(), and pcre_assign_jit_stack() in order to  control
1238           the  JIT  code's  memory  usage.   These functions are discussed in the
1239           pcrejit documentation.
1240    
1241         A second matching function, pcre_dfa_exec(), which is not Perl-compati-         A second matching function, pcre_dfa_exec(), which is not Perl-compati-
1242         ble,  is  also provided. This uses a different algorithm for the match-         ble,  is  also provided. This uses a different algorithm for the match-
1243         ing. The alternative algorithm finds all possible matches (at  a  given         ing. The alternative algorithm finds all possible matches (at  a  given
1244         point  in  the subject), and scans the subject just once. However, this         point  in  the  subject), and scans the subject just once (unless there
1245         algorithm does not return captured substrings. A description of the two         are lookbehind assertions). However, this  algorithm  does  not  return
1246         matching  algorithms and their advantages and disadvantages is given in         captured  substrings.  A description of the two matching algorithms and
1247         the pcrematching documentation.         their advantages and disadvantages is given in the  pcrematching  docu-
1248           mentation.
1249    
1250         In addition to the main compiling and  matching  functions,  there  are         In  addition  to  the  main compiling and matching functions, there are
1251         convenience functions for extracting captured substrings from a subject         convenience functions for extracting captured substrings from a subject
1252         string that is matched by pcre_exec(). They are:         string that is matched by pcre_exec(). They are:
1253    
# Line 849  PCRE API OVERVIEW Line 1262  PCRE API OVERVIEW
1262         pcre_free_substring() and pcre_free_substring_list() are also provided,         pcre_free_substring() and pcre_free_substring_list() are also provided,
1263         to free the memory used for extracted strings.         to free the memory used for extracted strings.
1264    
1265         The  function  pcre_maketables()  is  used  to build a set of character         The function pcre_maketables() is used to  build  a  set  of  character
1266         tables  in  the  current  locale   for   passing   to   pcre_compile(),         tables   in   the   current   locale  for  passing  to  pcre_compile(),
1267         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
1268         provided for specialist use.  Most  commonly,  no  special  tables  are         provided  for  specialist  use.  Most  commonly,  no special tables are
1269         passed,  in  which case internal tables that are generated when PCRE is         passed, in which case internal tables that are generated when  PCRE  is
1270         built are used.         built are used.
1271    
1272         The function pcre_fullinfo() is used to find out  information  about  a         The  function  pcre_fullinfo()  is used to find out information about a
1273         compiled  pattern; pcre_info() is an obsolete version that returns only         compiled pattern. The function pcre_version() returns a  pointer  to  a
1274         some of the available information, but is retained for  backwards  com-         string containing the version of PCRE and its date of release.
        patibility.   The function pcre_version() returns a pointer to a string  
        containing the version of PCRE and its date of release.  
1275    
1276         The function pcre_refcount() maintains a  reference  count  in  a  data         The  function  pcre_refcount()  maintains  a  reference count in a data
1277         block  containing  a compiled pattern. This is provided for the benefit         block containing a compiled pattern. This is provided for  the  benefit
1278         of object-oriented applications.         of object-oriented applications.
1279    
1280         The global variables pcre_malloc and pcre_free  initially  contain  the         The  global  variables  pcre_malloc and pcre_free initially contain the
1281         entry  points  of  the  standard malloc() and free() functions, respec-         entry points of the standard malloc()  and  free()  functions,  respec-
1282         tively. PCRE calls the memory management functions via these variables,         tively. PCRE calls the memory management functions via these variables,
1283         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
1284         calls. This should be done before calling any PCRE functions.         calls. This should be done before calling any PCRE functions.
1285    
1286         The global variables pcre_stack_malloc  and  pcre_stack_free  are  also         The  global  variables  pcre_stack_malloc  and pcre_stack_free are also
1287         indirections  to  memory  management functions. These special functions         indirections to memory management functions.  These  special  functions
1288         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
1289         data, instead of recursive function calls, when running the pcre_exec()         data, instead of recursive function calls, when running the pcre_exec()
1290         function. See the pcrebuild documentation for  details  of  how  to  do         function.  See  the  pcrebuild  documentation  for details of how to do
1291         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-
1292         ments that have limited stacks. Because of the greater  use  of  memory         ments  that  have  limited stacks. Because of the greater use of memory
1293         management,  it  runs  more  slowly. Separate functions are provided so         management, it runs more slowly. Separate  functions  are  provided  so
1294         that special-purpose external code can be  used  for  this  case.  When         that  special-purpose  external  code  can  be used for this case. When
1295         used,  these  functions  are always called in a stack-like manner (last         used, these functions are always called in a  stack-like  manner  (last
1296         obtained, first freed), and always for memory blocks of the same  size.         obtained,  first freed), and always for memory blocks of the same size.
1297         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-
1298         mentation.         mentation.
1299    
1300         The global variable pcre_callout initially contains NULL. It can be set         The global variable pcre_callout initially contains NULL. It can be set
1301         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
1302         specified points during a matching operation. Details are given in  the         specified  points during a matching operation. Details are given in the
1303         pcrecallout documentation.         pcrecallout documentation.
1304    
1305    
1306  NEWLINES  NEWLINES
1307    
1308         PCRE  supports five different conventions for indicating line breaks in         PCRE supports five different conventions for indicating line breaks  in
1309         strings: a single CR (carriage return) character, a  single  LF  (line-         strings:  a  single  CR (carriage return) character, a single LF (line-
1310         feed) character, the two-character sequence CRLF, any of the three pre-         feed) character, the two-character sequence CRLF, any of the three pre-
1311         ceding, or any Unicode newline sequence. The Unicode newline  sequences         ceding,  or any Unicode newline sequence. The Unicode newline sequences
1312         are  the  three just mentioned, plus the single characters VT (vertical         are the three just mentioned, plus the single characters  VT  (vertical
1313         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
1314         separator, U+2028), and PS (paragraph separator, U+2029).         separator, U+2028), and PS (paragraph separator, U+2029).
1315    
1316         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
1317         system as its standard newline sequence. When PCRE is built, a  default         system  as its standard newline sequence. When PCRE is built, a default
1318         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-
1319         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
1320         pattern is compiled, or when it is matched.         pattern is compiled, or when it is matched.
1321    
1322           At compile time, the newline convention can be specified by the options
1323           argument  of  pcre_compile(), or it can be specified by special text at
1324           the start of the pattern itself; this overrides any other settings. See
1325           the pcrepattern page for details of the special character sequences.
1326    
1327         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-
1328         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
1329         newline  convention  affects  the  handling of the dot, circumflex, and         newline  convention  affects  the  handling of the dot, circumflex, and
1330         dollar metacharacters, the handling of #-comments in /x mode, and, when         dollar metacharacters, the handling of #-comments in /x mode, and, when
1331         CRLF  is a recognized line ending sequence, the match position advance-         CRLF  is a recognized line ending sequence, the match position advance-
1332         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
1333         not affect the interpretation of the \n or \r escape sequences.         section on pcre_exec() options below.
1334    
1335           The  choice of newline convention does not affect the interpretation of
1336           the \n or \r escape sequences, nor does  it  affect  what  \R  matches,
1337           which is controlled in a similar way, but by separate options.
1338    
1339    
1340  MULTITHREADING  MULTITHREADING
# Line 924  MULTITHREADING Line 1344  MULTITHREADING
1344         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
1345         callout function pointed to by pcre_callout, are shared by all threads.         callout function pointed to by pcre_callout, are shared by all threads.
1346    
1347         The  compiled form of a regular expression is not altered during match-         The compiled form of a regular expression is not altered during  match-
1348         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
1349         at once.         at once.
1350    
1351           If the just-in-time optimization feature is being used, it needs  sepa-
1352           rate  memory stack areas for each thread. See the pcrejit documentation
1353           for more details.
1354    
1355    
1356  SAVING PRECOMPILED PATTERNS FOR LATER USE  SAVING PRECOMPILED PATTERNS FOR LATER USE
1357    
1358         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
1359         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
1360         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
1361         pcreprecompile documentation. However, compiling a  regular  expression         pcreprecompile  documentation,  which  includes  a  description  of the
1362         with  one version of PCRE for use with a different version is not guar-         pcre_pattern_to_host_byte_order() function. However, compiling a  regu-
1363         anteed to work and may cause crashes.         lar  expression  with one version of PCRE for use with a different ver-
1364           sion is not guaranteed to work and may cause crashes.
1365    
1366    
1367  CHECKING BUILD-TIME OPTIONS  CHECKING BUILD-TIME OPTIONS
# Line 950  CHECKING BUILD-TIME OPTIONS Line 1375  CHECKING BUILD-TIME OPTIONS
1375    
1376         The  first  argument  for pcre_config() is an integer, specifying which         The  first  argument  for pcre_config() is an integer, specifying which
1377         information is required; the second argument is a pointer to a variable         information is required; the second argument is a pointer to a variable
1378         into  which  the  information  is  placed. The following information is         into  which  the  information  is placed. The returned value is zero on
1379           success, or the negative error code PCRE_ERROR_BADOPTION if  the  value
1380           in  the  first argument is not recognized. The following information is
1381         available:         available:
1382    
1383           PCRE_CONFIG_UTF8           PCRE_CONFIG_UTF8
1384    
1385         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-
1386         able; otherwise it is set to zero.         able;  otherwise  it  is  set  to  zero. If this option is given to the
1387           16-bit  version  of  this  function,  pcre16_config(),  the  result  is
1388           PCRE_ERROR_BADOPTION.
1389    
1390             PCRE_CONFIG_UTF16
1391    
1392           The output is an integer that is set to one if UTF-16 support is avail-
1393           able; otherwise it is set to zero. This value should normally be  given
1394           to the 16-bit version of this function, pcre16_config(). If it is given
1395           to the 8-bit version of this function, the result is  PCRE_ERROR_BADOP-
1396           TION.
1397    
1398           PCRE_CONFIG_UNICODE_PROPERTIES           PCRE_CONFIG_UNICODE_PROPERTIES
1399    
1400         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
1401         character properties is available; otherwise it is set to zero.         character properties is available; otherwise it is set to zero.
1402    
1403             PCRE_CONFIG_JIT
1404    
1405           The output is an integer that is set to one if support for just-in-time
1406           compiling is available; otherwise it is set to zero.
1407    
1408             PCRE_CONFIG_JITTARGET
1409    
1410           The  output is a pointer to a zero-terminated "const char *" string. If
1411           JIT support is available, the string contains the name of the architec-
1412           ture  for  which the JIT compiler is configured, for example "x86 32bit
1413           (little endian + unaligned)". If JIT  support  is  not  available,  the
1414           result is NULL.
1415    
1416           PCRE_CONFIG_NEWLINE           PCRE_CONFIG_NEWLINE
1417    
1418         The output is an integer whose value specifies  the  default  character         The  output  is  an integer whose value specifies the default character
1419         sequence  that is recognized as meaning "newline". The four values that         sequence that is recognized as meaning "newline". The four values  that
1420         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,
1421         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
1422         for your operating system.         are returned in EBCDIC environments. The default should normally corre-
1423           spond to the standard sequence for your operating system.
1424    
1425             PCRE_CONFIG_BSR
1426    
1427           The output is an integer whose value indicates what character sequences
1428           the  \R  escape sequence matches by default. A value of 0 means that \R
1429           matches any Unicode line ending sequence; a value of 1  means  that  \R
1430           matches only CR, LF, or CRLF. The default can be overridden when a pat-
1431           tern is compiled or matched.
1432    
1433           PCRE_CONFIG_LINK_SIZE           PCRE_CONFIG_LINK_SIZE
1434    
1435         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
1436         internal linkage in compiled regular expressions. The value is 2, 3, or         internal  linkage  in  compiled  regular  expressions.  For  the  8-bit
1437         4. Larger values allow larger regular expressions to  be  compiled,  at         library, the value can be 2, 3, or 4. For the 16-bit library, the value
1438         the  expense  of  slower matching. The default value of 2 is sufficient         is either 2 or 4 and is still a number of bytes. The default value of 2
1439         for all but the most massive patterns, since  it  allows  the  compiled         is sufficient for all but the most massive patterns,  since  it  allows
1440         pattern to be up to 64K in size.         the  compiled  pattern  to  be  up to 64K in size.  Larger values allow
1441           larger regular expressions to be compiled, at  the  expense  of  slower
1442           matching.
1443    
1444           PCRE_CONFIG_POSIX_MALLOC_THRESHOLD           PCRE_CONFIG_POSIX_MALLOC_THRESHOLD
1445    
# Line 988  CHECKING BUILD-TIME OPTIONS Line 1449  CHECKING BUILD-TIME OPTIONS
1449    
1450           PCRE_CONFIG_MATCH_LIMIT           PCRE_CONFIG_MATCH_LIMIT
1451    
1452         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-
1453         internal matching function calls in a  pcre_exec()  execution.  Further         ber of internal matching function calls  in  a  pcre_exec()  execution.
1454         details are given with pcre_exec() below.         Further details are given with pcre_exec() below.
1455    
1456           PCRE_CONFIG_MATCH_LIMIT_RECURSION           PCRE_CONFIG_MATCH_LIMIT_RECURSION
1457    
1458         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
1459         recursion when calling the internal matching function in a  pcre_exec()         of  recursion  when  calling  the  internal  matching  function  in   a
1460         execution. Further details are given with pcre_exec() below.         pcre_exec()  execution.  Further  details  are  given  with pcre_exec()
1461           below.
1462    
1463           PCRE_CONFIG_STACKRECURSE           PCRE_CONFIG_STACKRECURSE
1464    
1465         The  output is an integer that is set to one if internal recursion when         The output is an integer that is set to one if internal recursion  when
1466         running pcre_exec() is implemented by recursive function calls that use         running pcre_exec() is implemented by recursive function calls that use
1467         the  stack  to remember their state. This is the usual way that PCRE is         the stack to remember their state. This is the usual way that  PCRE  is
1468         compiled. The output is zero if PCRE was compiled to use blocks of data         compiled. The output is zero if PCRE was compiled to use blocks of data
1469         on  the  heap  instead  of  recursive  function  calls.  In  this case,         on the  heap  instead  of  recursive  function  calls.  In  this  case,
1470         pcre_stack_malloc and  pcre_stack_free  are  called  to  manage  memory         pcre_stack_malloc  and  pcre_stack_free  are  called  to  manage memory
1471         blocks on the heap, thus avoiding the use of the stack.         blocks on the heap, thus avoiding the use of the stack.
1472    
1473    
# Line 1022  COMPILING A PATTERN Line 1484  COMPILING A PATTERN
1484    
1485         Either of the functions pcre_compile() or pcre_compile2() can be called         Either of the functions pcre_compile() or pcre_compile2() can be called
1486         to compile a pattern into an internal form. The only difference between         to compile a pattern into an internal form. The only difference between
1487         the  two interfaces is that pcre_compile2() has an additional argument,         the two interfaces is that pcre_compile2() has an additional  argument,
1488         errorcodeptr, via which a numerical error code can be returned.         errorcodeptr,  via  which  a  numerical  error code can be returned. To
1489           avoid too much repetition, we refer just to pcre_compile()  below,  but
1490           the information applies equally to pcre_compile2().
1491    
1492         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
1493         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
1494         obtained via pcre_malloc is returned. This contains the  compiled  code         obtained  via  pcre_malloc is returned. This contains the compiled code
1495         and related data. The pcre type is defined for the returned block; this         and related data. The pcre type is defined for the returned block; this
1496         is a typedef for a structure whose contents are not externally defined.         is a typedef for a structure whose contents are not externally defined.
1497         It is up to the caller to free the memory (via pcre_free) when it is no         It is up to the caller to free the memory (via pcre_free) when it is no
1498         longer required.         longer required.
1499    
1500         Although the compiled code of a PCRE regex is relocatable, that is,  it         Although  the compiled code of a PCRE regex is relocatable, that is, it
1501         does not depend on memory location, the complete pcre data block is not         does not depend on memory location, the complete pcre data block is not
1502         fully relocatable, because it may contain a copy of the tableptr  argu-         fully  relocatable, because it may contain a copy of the tableptr argu-
1503         ment, which is an address (see below).         ment, which is an address (see below).
1504    
1505         The options argument contains various bit settings that affect the com-         The options argument contains various bit settings that affect the com-
1506         pilation. It should be zero if no options are required.  The  available         pilation.  It  should be zero if no options are required. The available
1507         options  are  described  below. Some of them, in particular, those that         options are described below. Some of them (in  particular,  those  that
1508         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
1509         pattern  (see  the  detailed  description in the pcrepattern documenta-         unset from within the pattern (see  the  detailed  description  in  the
1510         tion). For these options, the contents of the options  argument  speci-         pcrepattern  documentation). For those options that can be different in
1511         fies  their initial settings at the start of compilation and execution.         different parts of the pattern, the contents of  the  options  argument
1512         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
1513         of matching as well as at compile time.         PCRE_ANCHORED, PCRE_BSR_xxx, PCRE_NEWLINE_xxx, PCRE_NO_UTF8_CHECK,  and
1514           PCRE_NO_START_OPT options can be set at the time of matching as well as
1515           at compile time.
1516    
1517         If errptr is NULL, pcre_compile() returns NULL immediately.  Otherwise,         If errptr is NULL, pcre_compile() returns NULL immediately.  Otherwise,
1518         if compilation of a pattern fails,  pcre_compile()  returns  NULL,  and         if  compilation  of  a  pattern fails, pcre_compile() returns NULL, and
1519         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-
1520         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
1521         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
1522         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
1523         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
1524         given.         (if  it is, an immediate error is given). However, for an invalid UTF-8
1525           string, the offset is that of the first byte of the failing character.
1526         If pcre_compile2() is used instead of pcre_compile(),  and  the  error-  
1527         codeptr  argument is not NULL, a non-zero error code number is returned         Some errors are not detected until the whole pattern has been  scanned;
1528         via this argument in the event of an error. This is in addition to  the         in  these  cases,  the offset passed back is the length of the pattern.
1529           Note that the offset is in bytes, not characters, even in  UTF-8  mode.
1530           It may sometimes point into the middle of a UTF-8 character.
1531    
1532           If  pcre_compile2()  is  used instead of pcre_compile(), and the error-
1533           codeptr argument is not NULL, a non-zero error code number is  returned
1534           via  this argument in the event of an error. This is in addition to the
1535         textual error message. Error codes and messages are listed below.         textual error message. Error codes and messages are listed below.
1536    
1537         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
1538         character tables that are  built  when  PCRE  is  compiled,  using  the         character  tables  that  are  built  when  PCRE  is compiled, using the
1539         default  C  locale.  Otherwise, tableptr must be an address that is the         default C locale. Otherwise, tableptr must be an address  that  is  the
1540         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
1541         compiled  pattern,  and used again by pcre_exec(), unless another table         compiled pattern, and used again by pcre_exec(), unless  another  table
1542         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
1543         support below.         support below.
1544    
1545         This  code  fragment  shows a typical straightforward call to pcre_com-         This code fragment shows a typical straightforward  call  to  pcre_com-
1546         pile():         pile():
1547    
1548           pcre *re;           pcre *re;
# Line 1083  COMPILING A PATTERN Line 1555  COMPILING A PATTERN
1555             &erroffset,       /* for error offset */             &erroffset,       /* for error offset */
1556             NULL);            /* use default character tables */             NULL);            /* use default character tables */
1557    
1558         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
1559         file:         file:
1560    
1561           PCRE_ANCHORED           PCRE_ANCHORED
1562    
1563         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
1564         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
1565         that  is being searched (the "subject string"). This effect can also be         that is being searched (the "subject string"). This effect can also  be
1566         achieved by appropriate constructs in the pattern itself, which is  the         achieved  by appropriate constructs in the pattern itself, which is the
1567         only way to do it in Perl.         only way to do it in Perl.
1568    
1569           PCRE_AUTO_CALLOUT           PCRE_AUTO_CALLOUT
1570    
1571         If this bit is set, pcre_compile() automatically inserts callout items,         If this bit is set, pcre_compile() automatically inserts callout items,
1572         all with number 255, before each pattern item. For  discussion  of  the         all  with  number  255, before each pattern item. For discussion of the
1573         callout facility, see the pcrecallout documentation.         callout facility, see the pcrecallout documentation.
1574    
1575             PCRE_BSR_ANYCRLF
1576             PCRE_BSR_UNICODE
1577    
1578           These options (which are mutually exclusive) control what the \R escape
1579           sequence  matches.  The choice is either to match only CR, LF, or CRLF,
1580           or to match any Unicode newline sequence. The default is specified when
1581           PCRE is built. It can be overridden from within the pattern, or by set-
1582           ting an option when a compiled pattern is matched.
1583    
1584           PCRE_CASELESS           PCRE_CASELESS
1585    
1586         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
1587         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
1588         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
1589         always understands the concept of case for characters whose values  are         always  understands the concept of case for characters whose values are
1590         less  than 128, so caseless matching is always possible. For characters         less than 128, so caseless matching is always possible. For  characters
1591         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-
1592         piled  with Unicode property support, but not otherwise. If you want to         piled with Unicode property support, but not otherwise. If you want  to
1593         use caseless matching for characters 128 and  above,  you  must  ensure         use  caseless  matching  for  characters 128 and above, you must ensure
1594         that  PCRE  is  compiled  with Unicode property support as well as with         that PCRE is compiled with Unicode property support  as  well  as  with
1595         UTF-8 support.         UTF-8 support.
1596    
1597           PCRE_DOLLAR_ENDONLY           PCRE_DOLLAR_ENDONLY
1598    
1599         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
1600         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
1601         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
1602         before  any  other newlines). The PCRE_DOLLAR_ENDONLY option is ignored         before any other newlines). The PCRE_DOLLAR_ENDONLY option  is  ignored
1603         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
1604         Perl, and no way to set it within a pattern.         Perl, and no way to set it within a pattern.
1605    
1606           PCRE_DOTALL           PCRE_DOTALL
1607    
1608         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-
1609         acters, including those that indicate newline. Without it, a  dot  does         acter of any value, including one that indicates a newline. However, it
1610         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.
1611         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
1612         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
1613         newline characters, independent of the setting of this option.         be  changed within a pattern by a (?s) option setting. A negative class
1614           such as [^a] always matches newline characters, independent of the set-
1615           ting of this option.
1616    
1617           PCRE_DUPNAMES           PCRE_DUPNAMES
1618    
1619         If this bit is set, names used to identify capturing  subpatterns  need         If  this  bit is set, names used to identify capturing subpatterns need
1620         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
1621         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
1622         matched.  There  are  more details of named subpatterns below; see also         matched. There are more details of named subpatterns  below;  see  also
1623         the pcrepattern documentation.         the pcrepattern documentation.
1624    
1625           PCRE_EXTENDED           PCRE_EXTENDED
1626    
1627         If this bit is set, whitespace  data  characters  in  the  pattern  are         If  this  bit  is  set,  whitespace  data characters in the pattern are
1628         totally ignored except when escaped or inside a character class. White-         totally ignored except when escaped or inside a character class. White-
1629         space does not include the VT character (code 11). In addition, charac-         space does not include the VT character (code 11). In addition, charac-
1630         ters between an unescaped # outside a character class and the next new-         ters between an unescaped # outside a character class and the next new-
1631         line, inclusive, are also ignored. This  is  equivalent  to  Perl's  /x         line,  inclusive,  are  also  ignored.  This is equivalent to Perl's /x
1632         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-
1633         ting.         ting.
1634    
1635           Which  characters  are  interpreted  as  newlines  is controlled by the
1636           options passed to pcre_compile() or by a special sequence at the  start
1637           of  the  pattern, as described in the section entitled "Newline conven-
1638           tions" in the pcrepattern documentation. Note that the end of this type
1639           of  comment  is  a  literal  newline  sequence  in  the pattern; escape
1640           sequences that happen to represent a newline do not count.
1641    
1642         This option makes it possible to include  comments  inside  complicated         This option makes it possible to include  comments  inside  complicated
1643         patterns.   Note,  however,  that this applies only to data characters.         patterns.   Note,  however,  that this applies only to data characters.
1644         Whitespace  characters  may  never  appear  within  special   character         Whitespace  characters  may  never  appear  within  special   character
1645         sequences  in  a  pattern,  for  example  within the sequence (?( which         sequences in a pattern, for example within the sequence (?( that intro-
1646         introduces a conditional subpattern.         duces a conditional subpattern.
1647    
1648           PCRE_EXTRA           PCRE_EXTRA
1649    
# Line 1163  COMPILING A PATTERN Line 1653  COMPILING A PATTERN
1653         letter  that  has  no  special  meaning causes an error, thus reserving         letter  that  has  no  special  meaning causes an error, thus reserving
1654         these combinations for future expansion. By  default,  as  in  Perl,  a         these combinations for future expansion. By  default,  as  in  Perl,  a
1655         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
1656         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
1657         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
1658         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
1659           within a pattern.
1660    
1661           PCRE_FIRSTLINE           PCRE_FIRSTLINE
1662    
1663         If this option is set, an  unanchored  pattern  is  required  to  match         If  this  option  is  set,  an  unanchored pattern is required to match
1664         before  or  at  the  first  newline  in  the subject string, though the         before or at the first  newline  in  the  subject  string,  though  the
1665         matched text may continue over the newline.         matched text may continue over the newline.
1666    
1667             PCRE_JAVASCRIPT_COMPAT
1668    
1669           If this option is set, PCRE's behaviour is changed in some ways so that
1670           it is compatible with JavaScript rather than Perl. The changes  are  as
1671           follows:
1672    
1673           (1)  A  lone  closing square bracket in a pattern causes a compile-time
1674           error, because this is illegal in JavaScript (by default it is  treated
1675           as a data character). Thus, the pattern AB]CD becomes illegal when this
1676           option is set.
1677    
1678           (2) At run time, a back reference to an unset subpattern group  matches
1679           an  empty  string (by default this causes the current matching alterna-
1680           tive to fail). A pattern such as (\1)(a) succeeds when this  option  is
1681           set  (assuming  it can find an "a" in the subject), whereas it fails by
1682           default, for Perl compatibility.
1683    
1684           (3) \U matches an upper case "U" character; by default \U causes a com-
1685           pile time error (Perl uses \U to upper case subsequent characters).
1686    
1687           (4) \u matches a lower case "u" character unless it is followed by four
1688           hexadecimal digits, in which case the hexadecimal  number  defines  the
1689           code  point  to match. By default, \u causes a compile time error (Perl
1690           uses it to upper case the following character).
1691    
1692           (5) \x matches a lower case "x" character unless it is followed by  two
1693           hexadecimal  digits,  in  which case the hexadecimal number defines the
1694           code point to match. By default, as in Perl, a  hexadecimal  number  is
1695           always expected after \x, but it may have zero, one, or two digits (so,
1696           for example, \xz matches a binary zero character followed by z).
1697    
1698           PCRE_MULTILINE           PCRE_MULTILINE
1699    
1700         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 1206  COMPILING A PATTERN Line 1728  COMPILING A PATTERN
1728         recognized. The Unicode newline sequences are the three just mentioned,         recognized. The Unicode newline sequences are the three just mentioned,
1729         plus  the  single  characters  VT (vertical tab, U+000B), FF (formfeed,         plus  the  single  characters  VT (vertical tab, U+000B), FF (formfeed,
1730         U+000C), NEL (next line, U+0085), LS (line separator, U+2028),  and  PS         U+000C), NEL (next line, U+0085), LS (line separator, U+2028),  and  PS
1731         (paragraph  separator,  U+2029).  The  last  two are recognized only in         (paragraph  separator, U+2029). For the 8-bit library, the last two are
1732         UTF-8 mode.         recognized only in UTF-8 mode.
1733    
1734         The newline setting in the  options  word  uses  three  bits  that  are         The newline setting in the  options  word  uses  three  bits  that  are
1735         treated as a number, giving eight possibilities. Currently only six are         treated as a number, giving eight possibilities. Currently only six are
# Line 1217  COMPILING A PATTERN Line 1739  COMPILING A PATTERN
1739         PCRE_NEWLINE_CRLF,  but other combinations may yield unused numbers and         PCRE_NEWLINE_CRLF,  but other combinations may yield unused numbers and
1740         cause an error.         cause an error.
1741    
1742         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
1743         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
1744         character class is encountered. This indicates  a  comment  that  lasts         characters, and so are ignored in this mode. Also, an unescaped #  out-
1745         until  after the next line break sequence. In other circumstances, line         side  a  character class indicates a comment that lasts until after the
1746         break  sequences  are  treated  as  literal  data,   except   that   in         next line break sequence. In other circumstances, line break  sequences
1747         PCRE_EXTENDED mode, both CR and LF are treated as whitespace characters         in patterns are treated as literal data.
        and are therefore ignored.  
1748    
1749         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
1750         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.
1751    
1752           PCRE_NO_AUTO_CAPTURE           PCRE_NO_AUTO_CAPTURE
1753    
# Line 1236  COMPILING A PATTERN Line 1757  COMPILING A PATTERN
1757         be  used  for  capturing  (and  they acquire numbers in the usual way).         be  used  for  capturing  (and  they acquire numbers in the usual way).
1758         There is no equivalent of this option in Perl.         There is no equivalent of this option in Perl.
1759    
1760             NO_START_OPTIMIZE
1761    
1762           This is an option that acts at matching time; that is, it is really  an
1763           option  for  pcre_exec()  or  pcre_dfa_exec().  If it is set at compile
1764           time, it is remembered with the compiled pattern and assumed at  match-
1765           ing  time.  For  details  see  the discussion of PCRE_NO_START_OPTIMIZE
1766           below.
1767    
1768             PCRE_UCP
1769    
1770           This option changes the way PCRE processes \B, \b, \D, \d, \S, \s,  \W,
1771           \w,  and  some  of  the POSIX character classes. By default, only ASCII
1772           characters are recognized, but if PCRE_UCP is set,  Unicode  properties
1773           are  used instead to classify characters. More details are given in the
1774           section on generic character types in the pcrepattern page. If you  set
1775           PCRE_UCP,  matching  one of the items it affects takes much longer. The
1776           option is available only if PCRE has been compiled with  Unicode  prop-
1777           erty support.
1778    
1779           PCRE_UNGREEDY           PCRE_UNGREEDY
1780    
1781         This option inverts the "greediness" of the quantifiers  so  that  they         This  option  inverts  the "greediness" of the quantifiers so that they
1782         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
1783         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
1784         within the pattern.         within the pattern.
1785    
1786           PCRE_UTF8           PCRE_UTF8
1787    
1788         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
1789         strings of UTF-8 characters instead of single-byte  character  strings.         strings of UTF-8 characters instead of single-byte strings. However, it
1790         However,  it is available only when PCRE is built to include UTF-8 sup-         is available only when PCRE is built to include UTF  support.  If  not,
1791         port. If not, the use of this option provokes an error. Details of  how         the  use  of  this option provokes an error. Details of how this option
1792         this  option  changes the behaviour of PCRE are given in the section on         changes the behaviour of PCRE are given in the pcreunicode page.
        UTF-8 support in the main pcre page.  
1793    
1794           PCRE_NO_UTF8_CHECK           PCRE_NO_UTF8_CHECK
1795    
1796         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
1797         automatically  checked.  There  is  a  discussion about the validity of         automatically  checked.  There  is  a  discussion about the validity of
1798         UTF-8 strings in the main pcre page. If an invalid  UTF-8  sequence  of         UTF-8 strings in the pcreunicode page. If an invalid UTF-8 sequence  is
1799         bytes  is  found,  pcre_compile() returns an error. If you already know         found,  pcre_compile()  returns an error. If you already know that your
1800         that your pattern is valid, and you want to skip this check for perfor-         pattern is valid, and you want to skip this check for performance  rea-
1801         mance  reasons,  you  can set the PCRE_NO_UTF8_CHECK option. When it is         sons,  you  can set the PCRE_NO_UTF8_CHECK option.  When it is set, the
1802         set, the effect of passing an invalid UTF-8  string  as  a  pattern  is         effect of passing an invalid UTF-8 string as a pattern is undefined. It
1803         undefined.  It  may  cause your program to crash. Note that this option         may  cause  your  program  to  crash. Note that this option can also be
1804         can also be passed to pcre_exec() and pcre_dfa_exec(), to suppress  the         passed to pcre_exec() and pcre_dfa_exec(),  to  suppress  the  validity
1805         UTF-8 validity checking of subject strings.         checking of subject strings.
1806    
1807    
1808  COMPILATION ERROR CODES  COMPILATION ERROR CODES
1809    
1810         The  following  table  lists  the  error  codes than may be returned by         The  following  table  lists  the  error  codes than may be returned by
1811         pcre_compile2(), along with the error messages that may be returned  by         pcre_compile2(), along with the error messages that may be returned  by
1812         both  compiling functions. As PCRE has developed, some error codes have         both  compiling  functions.  Note  that error messages are always 8-bit
1813         fallen out of use. To avoid confusion, they have not been re-used.         ASCII strings, even in 16-bit mode. As PCRE has developed,  some  error
1814           codes  have  fallen  out of use. To avoid confusion, they have not been
1815           re-used.
1816    
1817            0  no error            0  no error
1818            1  \ at end of pattern            1  \ at end of pattern
# Line 1285  COMPILATION ERROR CODES Line 1826  COMPILATION ERROR CODES
1826            9  nothing to repeat            9  nothing to repeat
1827           10  [this code is not in use]           10  [this code is not in use]
1828           11  internal error: unexpected repeat           11  internal error: unexpected repeat
1829           12  unrecognized character after (?           12  unrecognized character after (? or (?-
1830           13  POSIX named classes are supported only within a class           13  POSIX named classes are supported only within a class
1831           14  missing )           14  missing )
1832           15  reference to non-existent subpattern           15  reference to non-existent subpattern
# Line 1293  COMPILATION ERROR CODES Line 1834  COMPILATION ERROR CODES
1834           17  unknown option bit(s) set           17  unknown option bit(s) set
1835           18  missing ) after comment           18  missing ) after comment
1836           19  [this code is not in use]           19  [this code is not in use]
1837           20  regular expression too large           20  regular expression is too large
1838           21  failed to get memory           21  failed to get memory
1839           22  unmatched parentheses           22  unmatched parentheses
1840           23  internal error: code overflow           23  internal error: code overflow
# Line 1305  COMPILATION ERROR CODES Line 1846  COMPILATION ERROR CODES
1846           29  (?R or (?[+-]digits must be followed by )           29  (?R or (?[+-]digits must be followed by )
1847           30  unknown POSIX class name           30  unknown POSIX class name
1848           31  POSIX collating elements are not supported           31  POSIX collating elements are not supported
1849           32  this version of PCRE is not compiled with PCRE_UTF8 support           32  this version of PCRE is compiled without UTF support
1850           33  [this code is not in use]           33  [this code is not in use]
1851           34  character value in \x{...} sequence is too large           34  character value in \x{...} sequence is too large
1852           35  invalid condition (?(0)           35  invalid condition (?(0)
1853           36  \C not allowed in lookbehind assertion           36  \C not allowed in lookbehind assertion
1854           37  PCRE does not support \L, \l, \N, \U, or \u           37  PCRE does not support \L, \l, \N{name}, \U, or \u
1855           38  number after (?C is > 255           38  number after (?C is > 255
1856           39  closing ) for (?C expected           39  closing ) for (?C expected
1857           40  recursive call could loop indefinitely           40  recursive call could loop indefinitely
1858           41  unrecognized character after (?P           41  unrecognized character after (?P
1859           42  syntax error in subpattern name (missing terminator)           42  syntax error in subpattern name (missing terminator)
1860           43  two named subpatterns have the same name           43  two named subpatterns have the same name
1861           44  invalid UTF-8 string           44  invalid UTF-8 string (specifically UTF-8)
1862           45  support for \P, \p, and \X has not been compiled           45  support for \P, \p, and \X has not been compiled
1863           46  malformed \P or \p sequence           46  malformed \P or \p sequence
1864           47  unknown property name after \P or \p           47  unknown property name after \P or \p
1865           48  subpattern name is too long (maximum 32 characters)           48  subpattern name is too long (maximum 32 characters)
1866           49  too many named subpatterns (maximum 10,000)           49  too many named subpatterns (maximum 10000)
1867           50  [this code is not in use]           50  [this code is not in use]
1868           51  octal value is greater than \377 (not in UTF-8 mode)           51  octal value is greater than \377 in 8-bit non-UTF-8 mode
1869           52  internal error: overran compiling workspace           52  internal error: overran compiling workspace
1870           53  internal  error:  previously-checked  referenced  subpattern  not           53  internal error: previously-checked referenced subpattern
1871         found                 not found
1872           54  DEFINE group contains more than one branch           54  DEFINE group contains more than one branch
1873           55  repeating a DEFINE group is not allowed           55  repeating a DEFINE group is not allowed
1874           56  inconsistent NEWLINE options"           56  inconsistent NEWLINE options
1875           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
1876                 non-zero number                 name/number or by a plain number
1877           58  (?+ or (?- or (?(+ or (?(- must be followed by a non-zero number           58  a numbered reference must not be zero
1878             59  an argument is not allowed for (*ACCEPT), (*FAIL), or (*COMMIT)
1879             60  (*VERB) not recognized
1880             61  number is too big
1881             62  subpattern name expected
1882             63  digit expected after (?+
1883             64  ] is an invalid data character in JavaScript compatibility mode
1884             65  different names for subpatterns of the same number are
1885                   not allowed
1886             66  (*MARK) must have an argument
1887             67  this version of PCRE is not compiled with Unicode property
1888                   support
1889             68  \c must be followed by an ASCII character
1890             69  \k is not followed by a braced, angle-bracketed, or quoted name
1891             70  internal error: unknown opcode in find_fixedlength()
1892             71  \N is not supported in a class
1893             72  too many forward references
1894             73  disallowed Unicode code point (>= 0xd800 && <= 0xdfff)
1895             74  invalid UTF-16 string (specifically UTF-16)
1896    
1897           The numbers 32 and 10000 in errors 48 and 49  are  defaults;  different
1898           values may be used if the limits were changed when PCRE was built.
1899    
1900    
1901  STUDYING A PATTERN  STUDYING A PATTERN
# Line 1350  STUDYING A PATTERN Line 1912  STUDYING A PATTERN
1912         the results of the study.         the results of the study.
1913    
1914         The  returned  value  from  pcre_study()  can  be  passed  directly  to         The  returned  value  from  pcre_study()  can  be  passed  directly  to
1915         pcre_exec(). However, a pcre_extra block  also  contains  other  fields         pcre_exec() or pcre_dfa_exec(). However, a pcre_extra block  also  con-
1916         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
1917         described below in the section on matching a pattern.         passed; these are described below in the section on matching a pattern.
1918    
1919         If studying the pattern does not  produce  any  additional  information         If studying the  pattern  does  not  produce  any  useful  information,
1920         pcre_study() returns NULL. In that circumstance, if the calling program         pcre_study() returns NULL. In that circumstance, if the calling program
1921         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
1922         its own pcre_extra block.         pcre_dfa_exec(), it must set up its own pcre_extra block.
1923    
1924         The  second  argument of pcre_study() contains option bits. At present,         The second argument of pcre_study() contains option bits. There is only
1925         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-
1926           time  compiler  is  available,  the  pattern  is  further compiled into
1927           machine code that executes much faster than  the  pcre_exec()  matching
1928           function. If the just-in-time compiler is not available, this option is
1929           ignored. All other bits in the options argument must be zero.
1930    
1931           JIT compilation is a heavyweight optimization. It can  take  some  time
1932           for  patterns  to  be analyzed, and for one-off matches and simple pat-
1933           terns the benefit of faster execution might be offset by a much  slower
1934           study time.  Not all patterns can be optimized by the JIT compiler. For
1935           those that cannot be handled, matching automatically falls back to  the
1936           pcre_exec()  interpreter.  For more details, see the pcrejit documenta-
1937           tion.
1938    
1939         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.
1940         If  studying  succeeds  (even  if no data is returned), the variable it         If  studying  succeeds  (even  if no data is returned), the variable it
# Line 1369  STUDYING A PATTERN Line 1943  STUDYING A PATTERN
1943         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
1944         after calling pcre_study(), to be sure that it has run successfully.         after calling pcre_study(), to be sure that it has run successfully.
1945    
1946         This is a typical call to pcre_study():         When  you are finished with a pattern, you can free the memory used for
1947           the study data by calling pcre_free_study(). This function was added to
1948           the  API  for  release  8.20. For earlier versions, the memory could be
1949           freed with pcre_free(), just like the pattern itself. This  will  still
1950           work  in  cases  where  PCRE_STUDY_JIT_COMPILE  is  not used, but it is
1951           advisable to change to the new function when convenient.
1952    
1953           This is a typical way in which pcre_study() is used (except that  in  a
1954           real application there should be tests for errors):
1955    
1956           pcre_extra *pe;           int rc;
1957           pe = pcre_study(           pcre *re;
1958             pcre_extra *sd;
1959             re = pcre_compile("pattern", 0, &error, &erroroffset, NULL);
1960             sd = pcre_study(
1961             re,             /* result of pcre_compile() */             re,             /* result of pcre_compile() */
1962             0,              /* no options exist */             0,              /* no options */
1963             &error);        /* set to NULL or points to a message */             &error);        /* set to NULL or points to a message */
1964             rc = pcre_exec(   /* see below for details of pcre_exec() options */
1965         At present, studying a pattern is useful only for non-anchored patterns             re, sd, "subject", 7, 0, 0, ovector, 30);
1966         that do not have a single fixed starting character. A bitmap of  possi-           ...
1967         ble starting bytes is created.           pcre_free_study(sd);
1968             pcre_free(re);
1969    
1970           Studying a pattern does two things: first, a lower bound for the length
1971           of subject string that is needed to match the pattern is computed. This
1972           does not mean that there are any strings of that length that match, but
1973           it does guarantee that no shorter strings match. The value is  used  by
1974           pcre_exec()  and  pcre_dfa_exec()  to  avoid  wasting time by trying to
1975           match strings that are shorter than the lower bound. You can  find  out
1976           the value in a calling program via the pcre_fullinfo() function.
1977    
1978           Studying a pattern is also useful for non-anchored patterns that do not
1979           have a single fixed starting character. A bitmap of  possible  starting
1980           bytes  is  created. This speeds up finding a position in the subject at
1981           which to start matching. (In 16-bit mode, the bitmap is used for 16-bit
1982           values less than 256.)
1983    
1984           These  two optimizations apply to both pcre_exec() and pcre_dfa_exec().
1985           However, they are not used by pcre_exec()  if  pcre_study()  is  called
1986           with  the  PCRE_STUDY_JIT_COMPILE option, and just-in-time compiling is
1987           successful.  The  optimizations  can  be  disabled   by   setting   the
1988           PCRE_NO_START_OPTIMIZE    option    when    calling    pcre_exec()   or
1989           pcre_dfa_exec(). You might want to do this  if  your  pattern  contains
1990           callouts  or (*MARK) (which cannot be handled by the JIT compiler), and
1991           you want to make use of these facilities in cases where matching fails.
1992           See the discussion of PCRE_NO_START_OPTIMIZE below.
1993    
1994    
1995  LOCALE SUPPORT  LOCALE SUPPORT
# Line 1387  LOCALE SUPPORT Line 1997  LOCALE SUPPORT
1997         PCRE  handles  caseless matching, and determines whether characters are         PCRE  handles  caseless matching, and determines whether characters are
1998         letters, digits, or whatever, by reference to a set of tables,  indexed         letters, digits, or whatever, by reference to a set of tables,  indexed
1999         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
2000         characters with codes less than 128. Higher-valued  codes  never  match         characters with codes less than 128. By  default,  higher-valued  codes
2001         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
2002         with Unicode character property support. The use of locales  with  Uni-         PCRE is built with Unicode character property  support.  Alternatively,
2003         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
2004         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
2005         not try to mix the two.         use of locales with Unicode is discouraged. If you are handling charac-
2006           ters with codes greater than 128, you should either use UTF-8 and  Uni-
2007           code, or use locales, but not try to mix the two.
2008    
2009         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
2010         argument of pcre_compile() is  NULL.  These  are  sufficient  for  many         argument of pcre_compile() is  NULL.  These  are  sufficient  for  many
# Line 1444  INFORMATION ABOUT A PATTERN Line 2056  INFORMATION ABOUT A PATTERN
2056              int what, void *where);              int what, void *where);
2057    
2058         The pcre_fullinfo() function returns information about a compiled  pat-         The pcre_fullinfo() function returns information about a compiled  pat-
2059         tern. It replaces the obsolete pcre_info() function, which is neverthe-         tern.  It replaces the pcre_info() function, which was removed from the
2060         less retained for backwards compability (and is documented below).         library at version 8.30, after more than 10 years of obsolescence.
2061    
2062         The first argument for pcre_fullinfo() is a  pointer  to  the  compiled         The first argument for pcre_fullinfo() is a  pointer  to  the  compiled
2063         pattern.  The second argument is the result of pcre_study(), or NULL if         pattern.  The second argument is the result of pcre_study(), or NULL if
# Line 1454  INFORMATION ABOUT A PATTERN Line 2066  INFORMATION ABOUT A PATTERN
2066         variable to receive the data. The yield of the  function  is  zero  for         variable to receive the data. The yield of the  function  is  zero  for
2067         success, or one of the following negative numbers:         success, or one of the following negative numbers:
2068    
2069           PCRE_ERROR_NULL       the argument code was NULL           PCRE_ERROR_NULL           the argument code was NULL
2070                                 the argument where was NULL                                     the argument where was NULL
2071           PCRE_ERROR_BADMAGIC   the "magic number" was not found           PCRE_ERROR_BADMAGIC       the "magic number" was not found
2072           PCRE_ERROR_BADOPTION  the value of what was invalid           PCRE_ERROR_BADENDIANNESS  the pattern was compiled with different
2073                                       endianness
2074             PCRE_ERROR_BADOPTION      the value of what was invalid
2075    
2076         The  "magic  number" is placed at the start of each compiled pattern as         The  "magic  number" is placed at the start of each compiled pattern as
2077         an simple check against passing an arbitrary memory pointer. Here is  a         an simple check against passing an arbitrary memory pointer. The  endi-
2078         typical  call  of pcre_fullinfo(), to obtain the length of the compiled         anness error can occur if a compiled pattern is saved and reloaded on a
2079         pattern:         different host. Here is a typical call of  pcre_fullinfo(),  to  obtain
2080           the length of the compiled pattern:
2081    
2082           int rc;           int rc;
2083           size_t length;           size_t length;
2084           rc = pcre_fullinfo(           rc = pcre_fullinfo(
2085             re,               /* result of pcre_compile() */             re,               /* result of pcre_compile() */
2086             pe,               /* result of pcre_study(), or NULL */             sd,               /* result of pcre_study(), or NULL */
2087             PCRE_INFO_SIZE,   /* what is required */             PCRE_INFO_SIZE,   /* what is required */
2088             &length);         /* where to put the data */             &length);         /* where to put the data */
2089    
2090         The possible values for the third argument are defined in  pcre.h,  and         The  possible  values for the third argument are defined in pcre.h, and
2091         are as follows:         are as follows:
2092    
2093           PCRE_INFO_BACKREFMAX           PCRE_INFO_BACKREFMAX
2094    
2095         Return  the  number  of  the highest back reference in the pattern. The         Return the number of the highest back reference  in  the  pattern.  The
2096         fourth argument should point to an int variable. Zero  is  returned  if         fourth  argument  should  point to an int variable. Zero is returned if
2097         there are no back references.         there are no back references.
2098    
2099           PCRE_INFO_CAPTURECOUNT           PCRE_INFO_CAPTURECOUNT
2100    
2101         Return  the  number of capturing subpatterns in the pattern. The fourth         Return the number of capturing subpatterns in the pattern.  The  fourth
2102         argument should point to an int variable.         argument should point to an int variable.
2103    
2104           PCRE_INFO_DEFAULT_TABLES           PCRE_INFO_DEFAULT_TABLES
2105    
2106         Return a pointer to the internal default character tables within  PCRE.         Return  a pointer to the internal default character tables within PCRE.
2107         The  fourth  argument should point to an unsigned char * variable. This         The fourth argument should point to an unsigned char *  variable.  This
2108         information call is provided for internal use by the pcre_study() func-         information call is provided for internal use by the pcre_study() func-
2109         tion.  External  callers  can  cause PCRE to use its internal tables by         tion. External callers can cause PCRE to use  its  internal  tables  by
2110         passing a NULL table pointer.         passing a NULL table pointer.
2111    
2112           PCRE_INFO_FIRSTBYTE           PCRE_INFO_FIRSTBYTE
2113    
2114         Return information about the first byte of any matched  string,  for  a         Return information about the first data unit of any matched string, for
2115         non-anchored  pattern. The fourth argument should point to an int vari-         a non-anchored pattern. (The name of this option refers  to  the  8-bit
2116         able. (This option used to be called PCRE_INFO_FIRSTCHAR; the old  name         library,  where data units are bytes.) The fourth argument should point
2117         is still recognized for backwards compatibility.)         to an int variable.
2118    
2119           If there is a fixed first value, for example, the  letter  "c"  from  a
2120           pattern  such  as (cat|cow|coyote), its value is returned. In the 8-bit
2121           library, the value is always less than 256; in the 16-bit  library  the
2122           value can be up to 0xffff.
2123    
2124         If  there  is  a  fixed first byte, for example, from a pattern such as         If there is no fixed first value, and if either
        (cat|cow|coyote), its value is returned. Otherwise, if either  
2125    
2126         (a) the pattern was compiled with the PCRE_MULTILINE option, and  every         (a)  the pattern was compiled with the PCRE_MULTILINE option, and every
2127         branch starts with "^", or         branch starts with "^", or
2128    
2129         (b) every branch of the pattern starts with ".*" and PCRE_DOTALL is not         (b) every branch of the pattern starts with ".*" and PCRE_DOTALL is not
2130         set (if it were set, the pattern would be anchored),         set (if it were set, the pattern would be anchored),
2131    
2132         -1 is returned, indicating that the pattern matches only at  the  start         -1  is  returned, indicating that the pattern matches only at the start
2133         of  a  subject string or after any newline within the string. Otherwise         of a subject string or after any newline within the  string.  Otherwise
2134         -2 is returned. For anchored patterns, -2 is returned.         -2 is returned. For anchored patterns, -2 is returned.
2135    
2136           PCRE_INFO_FIRSTTABLE           PCRE_INFO_FIRSTTABLE
2137    
2138         If the pattern was studied, and this resulted in the construction of  a         If  the pattern was studied, and this resulted in the construction of a
2139         256-bit table indicating a fixed set of bytes for the first byte in any         256-bit table indicating a fixed set of values for the first data  unit
2140         matching string, a pointer to the table is returned. Otherwise NULL  is         in  any  matching string, a pointer to the table is returned. Otherwise
2141         returned.  The fourth argument should point to an unsigned char * vari-         NULL is returned. The fourth argument should point to an unsigned  char
2142         able.         * variable.
2143    
2144             PCRE_INFO_HASCRORLF
2145    
2146           Return  1  if  the  pattern  contains any explicit matches for CR or LF
2147           characters, otherwise 0. The fourth argument should  point  to  an  int
2148           variable.  An explicit match is either a literal CR or LF character, or
2149           \r or \n.
2150    
2151           PCRE_INFO_JCHANGED           PCRE_INFO_JCHANGED
2152    
2153         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,
2154         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)
2155         nal option setting changes the local PCRE_DUPNAMES option.         and (?-J) set and unset the local PCRE_DUPNAMES option, respectively.
2156    
2157             PCRE_INFO_JIT
2158    
2159           Return 1 if the pattern was  studied  with  the  PCRE_STUDY_JIT_COMPILE
2160           option,  and just-in-time compiling was successful. The fourth argument
2161           should point to an int variable. A return value of  0  means  that  JIT
2162           support  is  not available in this version of PCRE, or that the pattern
2163           was not studied with the PCRE_STUDY_JIT_COMPILE option, or that the JIT
2164           compiler could not handle this particular pattern. See the pcrejit doc-
2165           umentation for details of what can and cannot be handled.
2166    
2167             PCRE_INFO_JITSIZE
2168    
2169           If the pattern was successfully studied with the PCRE_STUDY_JIT_COMPILE
2170           option,  return  the  size  of  the JIT compiled code, otherwise return
2171           zero. The fourth argument should point to a size_t variable.
2172    
2173           PCRE_INFO_LASTLITERAL           PCRE_INFO_LASTLITERAL
2174    
2175         Return the value of the rightmost literal byte that must exist  in  any         Return the value of the rightmost literal data unit that must exist  in
2176         matched  string,  other  than  at  its  start,  if such a byte has been         any  matched  string, other than at its start, if such a value has been
2177         recorded. The fourth argument should point to an int variable. If there         recorded. The fourth argument should point to an int variable. If there
2178         is  no such byte, -1 is returned. For anchored patterns, a last literal         is no such value, -1 is returned. For anchored patterns, a last literal
2179         byte is recorded only if it follows something of variable  length.  For         value is recorded only if it follows something of variable length.  For
2180         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
2181         /^a\dz\d/ the returned value is -1.         /^a\dz\d/ the returned value is -1.
2182    
2183             PCRE_INFO_MINLENGTH
2184    
2185           If the pattern was studied and a minimum length  for  matching  subject
2186           strings  was  computed,  its  value is returned. Otherwise the returned
2187           value is -1. The value is a number of characters, which in  UTF-8  mode
2188           may  be  different from the number of bytes. The fourth argument should
2189           point to an int variable. A non-negative value is a lower bound to  the
2190           length  of  any  matching  string. There may not be any strings of that
2191           length that do actually match, but every string that does match  is  at
2192           least that long.
2193    
2194           PCRE_INFO_NAMECOUNT           PCRE_INFO_NAMECOUNT
2195           PCRE_INFO_NAMEENTRYSIZE           PCRE_INFO_NAMEENTRYSIZE
2196           PCRE_INFO_NAMETABLE           PCRE_INFO_NAMETABLE
2197    
2198         PCRE supports the use of named as well as numbered capturing  parenthe-         PCRE  supports the use of named as well as numbered capturing parenthe-
2199         ses.  The names are just an additional way of identifying the parenthe-         ses. The names are just an additional way of identifying the  parenthe-
2200         ses, which still acquire numbers. Several convenience functions such as         ses, which still acquire numbers. Several convenience functions such as
2201         pcre_get_named_substring()  are  provided  for extracting captured sub-         pcre_get_named_substring() are provided for  extracting  captured  sub-
2202         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
2203         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
2204         pointers in the output vector (described with pcre_exec() below). To do         pointers in the output vector (described with pcre_exec() below). To do
2205         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
2206         described by these three values.         described by these three values.
2207    
2208         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
2209         gives the number of entries, and PCRE_INFO_NAMEENTRYSIZE gives the size         gives the number of entries, and PCRE_INFO_NAMEENTRYSIZE gives the size
2210         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
2211         depends  on the length of the longest name. PCRE_INFO_NAMETABLE returns         depends on the length of the longest name. PCRE_INFO_NAMETABLE  returns
2212         a pointer to the first entry of the table  (a  pointer  to  char).  The         a pointer to the first entry of the table. This is a pointer to char in
2213         first two bytes of each entry are the number of the capturing parenthe-         the 8-bit library, where the first two bytes of each entry are the num-
2214         sis, most significant byte first. The rest of the entry is  the  corre-         ber  of  the capturing parenthesis, most significant byte first. In the
2215         sponding  name,  zero  terminated. The names are in alphabetical order.         16-bit library, the pointer points to 16-bit data units, the  first  of
2216         When PCRE_DUPNAMES is set, duplicate names are in order of their paren-         which  contains  the  parenthesis  number. The rest of the entry is the
2217         theses  numbers.  For  example,  consider the following pattern (assume         corresponding name, zero terminated.
2218         PCRE_EXTENDED is  set,  so  white  space  -  including  newlines  -  is  
2219         ignored):         The names are in alphabetical order. Duplicate names may appear if  (?|
2220           is used to create multiple groups with the same number, as described in
2221           the section on duplicate subpattern numbers in  the  pcrepattern  page.
2222           Duplicate  names  for  subpatterns with different numbers are permitted
2223           only if PCRE_DUPNAMES is set. In all cases  of  duplicate  names,  they
2224           appear  in  the table in the order in which they were found in the pat-
2225           tern. In the absence of (?| this is the  order  of  increasing  number;
2226           when (?| is used this is not necessarily the case because later subpat-
2227           terns may have lower numbers.
2228    
2229           As a simple example of the name/number table,  consider  the  following
2230           pattern after compilation by the 8-bit library (assume PCRE_EXTENDED is
2231           set, so white space - including newlines - is ignored):
2232    
2233           (?<date> (?<year>(\d\d)?\d\d) -           (?<date> (?<year>(\d\d)?\d\d) -
2234           (?<month>\d\d) - (?<day>\d\d) )           (?<month>\d\d) - (?<day>\d\d) )
2235    
2236         There  are  four  named subpatterns, so the table has four entries, and         There are four named subpatterns, so the table has  four  entries,  and
2237         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,
2238         with non-printing bytes shows in hexadecimal, and undefined bytes shown         with non-printing bytes shows in hexadecimal, and undefined bytes shown
2239         as ??:         as ??:
2240    
# Line 1578  INFORMATION ABOUT A PATTERN Line 2243  INFORMATION ABOUT A PATTERN
2243           00 04 m  o  n  t  h  00           00 04 m  o  n  t  h  00
2244           00 02 y  e  a  r  00 ??           00 02 y  e  a  r  00 ??
2245    
2246         When writing code to extract data  from  named  subpatterns  using  the         When  writing  code  to  extract  data from named subpatterns using the
2247         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
2248         to be different for each compiled pattern.         to be different for each compiled pattern.
2249    
2250           PCRE_INFO_OKPARTIAL           PCRE_INFO_OKPARTIAL
2251    
2252         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
2253         The  fourth  argument  should point to an int variable. The pcrepartial         pcre_exec(), otherwise 0. The fourth argument should point  to  an  int
2254         documentation lists the restrictions that apply to patterns  when  par-         variable.  From  release  8.00,  this  always  returns  1,  because the
2255         tial matching is used.         restrictions that previously applied  to  partial  matching  have  been
2256           lifted.  The  pcrepartial documentation gives details of partial match-
2257           ing.
2258    
2259           PCRE_INFO_OPTIONS           PCRE_INFO_OPTIONS
2260    
2261         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
2262         fourth argument should point to an unsigned long  int  variable.  These         fourth  argument  should  point to an unsigned long int variable. These
2263         option bits are those specified in the call to pcre_compile(), modified         option bits are those specified in the call to pcre_compile(), modified
2264         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
2265         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
2266         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
2267         the  PCRE_EXTENDED option, the result is PCRE_CASELESS, PCRE_MULTILINE,         the PCRE_EXTENDED option, the result is PCRE_CASELESS,  PCRE_MULTILINE,
2268         and PCRE_EXTENDED.         and PCRE_EXTENDED.
2269    
2270         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
2271         alternatives begin with one of the following:         alternatives begin with one of the following:
2272    
2273           ^     unless PCRE_MULTILINE is set           ^     unless PCRE_MULTILINE is set
# Line 1614  INFORMATION ABOUT A PATTERN Line 2281  INFORMATION ABOUT A PATTERN
2281    
2282           PCRE_INFO_SIZE           PCRE_INFO_SIZE
2283    
2284         Return the size of the compiled pattern, that is, the  value  that  was         Return  the size of the compiled pattern in bytes (for both libraries).
2285         passed as the argument to pcre_malloc() when PCRE was getting memory in         The fourth argument should point to a size_t variable. This value  does
2286         which to place the compiled data. The fourth argument should point to a         not  include  the  size  of  the  pcre  structure  that  is returned by
2287         size_t variable.         pcre_compile(). The value that is passed as the argument  to  pcre_mal-
2288           loc()  when pcre_compile() is getting memory in which to place the com-
2289           piled data is the value returned by this option plus the  size  of  the
2290           pcre  structure. Studying a compiled pattern, with or without JIT, does
2291           not alter the value returned by this option.
2292    
2293           PCRE_INFO_STUDYSIZE           PCRE_INFO_STUDYSIZE
2294    
2295         Return the size of the data block pointed to by the study_data field in         Return the size in bytes of the data block pointed to by the study_data
2296         a pcre_extra block. That is,  it  is  the  value  that  was  passed  to         field  in  a  pcre_extra  block.  If pcre_extra is NULL, or there is no
2297         pcre_malloc() when PCRE was getting memory into which to place the data         study data, zero is returned. The fourth argument  should  point  to  a
2298         created by pcre_study(). The fourth argument should point to  a  size_t         size_t  variable. The study_data field is set by pcre_study() to record
2299         variable.         information that will speed  up  matching  (see  the  section  entitled
2300           "Studying a pattern" above). The format of the study_data block is pri-
2301           vate, but its length is made available via this option so that  it  can
2302  OBSOLETE INFO FUNCTION         be  saved  and  restored  (see  the  pcreprecompile  documentation  for
2303           details).
        int pcre_info(const pcre *code, int *optptr, int *firstcharptr);  
   
        The  pcre_info()  function is now obsolete because its interface is too  
        restrictive to return all the available data about a compiled  pattern.  
        New   programs   should  use  pcre_fullinfo()  instead.  The  yield  of  
        pcre_info() is the number of capturing subpatterns, or one of the  fol-  
        lowing negative numbers:  
   
          PCRE_ERROR_NULL       the argument code was NULL  
          PCRE_ERROR_BADMAGIC   the "magic number" was not found  
   
        If  the  optptr  argument is not NULL, a copy of the options with which  
        the pattern was compiled is placed in the integer  it  points  to  (see  
        PCRE_INFO_OPTIONS above).  
   
        If  the  pattern  is  not anchored and the firstcharptr argument is not  
        NULL, it is used to pass back information about the first character  of  
        any matched string (see PCRE_INFO_FIRSTBYTE above).  
2304    
2305    
2306  REFERENCE COUNTS  REFERENCE COUNTS
2307    
2308         int pcre_refcount(pcre *code, int adjust);         int pcre_refcount(pcre *code, int adjust);
2309    
2310         The  pcre_refcount()  function is used to maintain a reference count in         The pcre_refcount() function is used to maintain a reference  count  in
2311         the data block that contains a compiled pattern. It is provided for the         the data block that contains a compiled pattern. It is provided for the
2312         benefit  of  applications  that  operate  in an object-oriented manner,         benefit of applications that  operate  in  an  object-oriented  manner,
2313         where different parts of the application may be using the same compiled         where different parts of the application may be using the same compiled
2314         pattern, but you want to free the block when they are all done.         pattern, but you want to free the block when they are all done.
2315    
2316         When a pattern is compiled, the reference count field is initialized to         When a pattern is compiled, the reference count field is initialized to
2317         zero.  It is changed only by calling this function, whose action is  to         zero.   It is changed only by calling this function, whose action is to
2318         add  the  adjust  value  (which may be positive or negative) to it. The         add the adjust value (which may be positive or  negative)  to  it.  The
2319         yield of the function is the new value. However, the value of the count         yield of the function is the new value. However, the value of the count
2320         is  constrained to lie between 0 and 65535, inclusive. If the new value         is constrained to lie between 0 and 65535, inclusive. If the new  value
2321         is outside these limits, it is forced to the appropriate limit value.         is outside these limits, it is forced to the appropriate limit value.
2322    
2323         Except when it is zero, the reference count is not correctly  preserved         Except  when it is zero, the reference count is not correctly preserved
2324         if  a  pattern  is  compiled on one host and then transferred to a host         if a pattern is compiled on one host and then  transferred  to  a  host
2325         whose byte-order is different. (This seems a highly unlikely scenario.)         whose byte-order is different. (This seems a highly unlikely scenario.)
2326    
2327    
# Line 1680  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 2333  MATCHING A PATTERN: THE TRADITIONAL FUNC
2333    
2334         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
2335         compiled pattern, which is passed in the code argument. If the  pattern         compiled pattern, which is passed in the code argument. If the  pattern
2336         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
2337         argument. This function is the main matching facility of  the  library,         argument. You can call pcre_exec() with the same code and  extra  argu-
2338         and it operates in a Perl-like manner. For specialist use there is also         ments  as  many  times as you like, in order to match different subject
2339         an alternative matching function, which is described below in the  sec-         strings with the same pattern.
2340         tion about the pcre_dfa_exec() function.  
2341           This function is the main matching facility  of  the  library,  and  it
2342           operates  in  a  Perl-like  manner. For specialist use there is also an
2343           alternative matching function, which is described below in the  section
2344           about the pcre_dfa_exec() function.
2345    
2346         In  most applications, the pattern will have been compiled (and option-         In  most applications, the pattern will have been compiled (and option-
2347         ally studied) in the same process that calls pcre_exec().  However,  it         ally studied) in the same process that calls pcre_exec().  However,  it
# Line 1716  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 2373  MATCHING A PATTERN: THE TRADITIONAL FUNC
2373    
2374           unsigned long int flags;           unsigned long int flags;
2375           void *study_data;           void *study_data;
2376             void *executable_jit;
2377           unsigned long int match_limit;           unsigned long int match_limit;
2378           unsigned long int match_limit_recursion;           unsigned long int match_limit_recursion;
2379           void *callout_data;           void *callout_data;
2380           const unsigned char *tables;           const unsigned char *tables;
2381             unsigned char **mark;
2382    
2383           In  the  16-bit  version  of  this  structure,  the mark field has type
2384           "PCRE_UCHAR16 **".
2385    
2386         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
2387         are set. The flag bits are:         are set. The flag bits are:
2388    
2389           PCRE_EXTRA_STUDY_DATA           PCRE_EXTRA_STUDY_DATA
2390             PCRE_EXTRA_EXECUTABLE_JIT
2391           PCRE_EXTRA_MATCH_LIMIT           PCRE_EXTRA_MATCH_LIMIT
2392           PCRE_EXTRA_MATCH_LIMIT_RECURSION           PCRE_EXTRA_MATCH_LIMIT_RECURSION
2393           PCRE_EXTRA_CALLOUT_DATA           PCRE_EXTRA_CALLOUT_DATA
2394           PCRE_EXTRA_TABLES           PCRE_EXTRA_TABLES
2395             PCRE_EXTRA_MARK
2396    
2397         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-
2398         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
2399         the appropriate flag bit. You should not set this yourself, but you may         returned  by pcre_study(), together with the appropriate flag bits. You
2400         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
2401         flag bits.         the other fields and their corresponding flag bits.
2402    
2403         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
2404         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
2405         match, but which have a very large number  of  possibilities  in  their         match,  but  which  have  a very large number of possibilities in their
2406         search  trees.  The  classic  example  is  the  use of nested unlimited         search trees. The classic example is a pattern that uses nested  unlim-
2407         repeats.         ited repeats.
2408    
2409         Internally, PCRE uses a function called match() which it calls  repeat-         Internally,  pcre_exec() uses a function called match(), which it calls
2410         edly  (sometimes  recursively). The limit set by match_limit is imposed         repeatedly (sometimes recursively). The limit  set  by  match_limit  is
2411         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,
2412         has  the  effect  of  limiting the amount of backtracking that can take         which has the effect of limiting the amount of  backtracking  that  can
2413         place. For patterns that are not anchored, the count restarts from zero         take place. For patterns that are not anchored, the count restarts from
2414         for each position in the subject string.         zero for each position in the subject string.
2415    
2416           When pcre_exec() is called with a pattern that was successfully studied
2417           with  the  PCRE_STUDY_JIT_COMPILE  option, the way that the matching is
2418           executed is entirely different. However, there is still the possibility
2419           of  runaway  matching  that  goes  on  for a very long time, and so the
2420           match_limit value is also used in this case (but in a different way) to
2421           limit how long the matching can continue.
2422    
2423         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
2424         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 2433  MATCHING A PATTERN: THE TRADITIONAL FUNC
2433         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-
2434         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.
2435    
2436         Limiting  the  recursion  depth  limits the amount of stack that can be         Limiting the recursion depth limits the amount of  machine  stack  that
2437         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
2438         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
2439           limit  is not relevant, and is ignored, if the pattern was successfully
2440         The  default  value  for  match_limit_recursion can be set when PCRE is         studied with PCRE_STUDY_JIT_COMPILE.
2441         built; the default default  is  the  same  value  as  the  default  for  
2442         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
2443         a  pcre_extra  block  in  which  match_limit_recursion  is   set,   and         built;  the  default  default  is  the  same  value  as the default for
2444         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
2445           a   pcre_extra   block  in  which  match_limit_recursion  is  set,  and
2446           PCRE_EXTRA_MATCH_LIMIT_RECURSION is set in  the  flags  field.  If  the
2447         limit is exceeded, pcre_exec() returns PCRE_ERROR_RECURSIONLIMIT.         limit is exceeded, pcre_exec() returns PCRE_ERROR_RECURSIONLIMIT.
2448    
2449         The pcre_callout field is used in conjunction with the  "callout"  fea-         The  callout_data  field is used in conjunction with the "callout" fea-
2450         ture, which is described in the pcrecallout documentation.         ture, and is described in the pcrecallout documentation.
2451    
2452         The  tables  field  is  used  to  pass  a  character  tables pointer to         The tables field  is  used  to  pass  a  character  tables  pointer  to
2453         pcre_exec(); this overrides the value that is stored with the  compiled         pcre_exec();  this overrides the value that is stored with the compiled
2454         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
2455         custom tables were supplied to pcre_compile() via  its  tableptr  argu-         custom  tables  were  supplied to pcre_compile() via its tableptr argu-
2456         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
2457         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-
2458         using  patterns  that  have been saved after compiling with an external         using patterns that have been saved after compiling  with  an  external
2459         set of tables, because the external tables  might  be  at  a  different         set  of  tables,  because  the  external tables might be at a different
2460         address  when  pcre_exec() is called. See the pcreprecompile documenta-         address when pcre_exec() is called. See the  pcreprecompile  documenta-
2461         tion for a discussion of saving compiled patterns for later use.         tion for a discussion of saving compiled patterns for later use.
2462    
2463           If  PCRE_EXTRA_MARK  is  set in the flags field, the mark field must be
2464           set to point to a suitable variable. If the pattern contains any  back-
2465           tracking  control verbs such as (*MARK:NAME), and the execution ends up
2466           with a name to pass back, a pointer to the  name  string  (zero  termi-
2467           nated)  is  placed  in  the  variable pointed to by the mark field. The
2468           names are within the compiled pattern; if you wish  to  retain  such  a
2469           name  you must copy it before freeing the memory of a compiled pattern.
2470           If there is no name to pass back, the variable pointed to by  the  mark
2471           field  is  set  to NULL. For details of the backtracking control verbs,
2472           see the section entitled "Backtracking control" in the pcrepattern doc-
2473           umentation.
2474    
2475     Option bits for pcre_exec()     Option bits for pcre_exec()
2476    
2477         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.
2478         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,
2479         PCRE_NOTBOL,   PCRE_NOTEOL,   PCRE_NOTEMPTY,   PCRE_NO_UTF8_CHECK   and         PCRE_NOTBOL,    PCRE_NOTEOL,    PCRE_NOTEMPTY,   PCRE_NOTEMPTY_ATSTART,
2480         PCRE_PARTIAL.         PCRE_NO_START_OPTIMIZE,  PCRE_NO_UTF8_CHECK,   PCRE_PARTIAL_SOFT,   and
2481           PCRE_PARTIAL_HARD.
2482    
2483           If the pattern was successfully studied with the PCRE_STUDY_JIT_COMPILE
2484           option,  the   only   supported   options   for   JIT   execution   are
2485           PCRE_NO_UTF8_CHECK,   PCRE_NOTBOL,   PCRE_NOTEOL,   PCRE_NOTEMPTY,  and
2486           PCRE_NOTEMPTY_ATSTART. Note in particular that partial matching is  not
2487           supported.  If an unsupported option is used, JIT execution is disabled
2488           and the normal interpretive code in pcre_exec() is run.
2489    
2490           PCRE_ANCHORED           PCRE_ANCHORED
2491    
2492         The  PCRE_ANCHORED  option  limits pcre_exec() to matching at the first         The PCRE_ANCHORED option limits pcre_exec() to matching  at  the  first
2493         matching position. If a pattern was  compiled  with  PCRE_ANCHORED,  or         matching  position.  If  a  pattern was compiled with PCRE_ANCHORED, or
2494         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
2495         unachored at matching time.         unachored at matching time.
2496    
2497             PCRE_BSR_ANYCRLF
2498             PCRE_BSR_UNICODE
2499    
2500           These options (which are mutually exclusive) control what the \R escape
2501           sequence matches. The choice is either to match only CR, LF,  or  CRLF,
2502           or  to  match  any Unicode newline sequence. These options override the
2503           choice that was made or defaulted when the pattern was compiled.
2504    
2505           PCRE_NEWLINE_CR           PCRE_NEWLINE_CR
2506           PCRE_NEWLINE_LF           PCRE_NEWLINE_LF
2507           PCRE_NEWLINE_CRLF           PCRE_NEWLINE_CRLF
# Line 1812  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 2513  MATCHING A PATTERN: THE TRADITIONAL FUNC
2513         tion of pcre_compile()  above.  During  matching,  the  newline  choice         tion of pcre_compile()  above.  During  matching,  the  newline  choice
2514         affects  the  behaviour  of the dot, circumflex, and dollar metacharac-         affects  the  behaviour  of the dot, circumflex, and dollar metacharac-
2515         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
2516         match  failure  for  an  unanchored  pattern.  When  PCRE_NEWLINE_CRLF,         match failure for an unanchored pattern.
2517         PCRE_NEWLINE_ANYCRLF, or PCRE_NEWLINE_ANY is set, and a  match  attempt  
2518         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
2519         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-
2520         after the CRLF.         rent  position  is  at  a  CRLF  sequence,  and the pattern contains no
2521           explicit matches for  CR  or  LF  characters,  the  match  position  is
2522           advanced by two characters instead of one, in other words, to after the
2523           CRLF.
2524    
2525           The above rule is a compromise that makes the most common cases work as
2526           expected.  For  example,  if  the  pattern  is .+A (and the PCRE_DOTALL
2527           option is not set), it does not match the string "\r\nA" because, after
2528           failing  at the start, it skips both the CR and the LF before retrying.
2529           However, the pattern [\r\n]A does match that string,  because  it  con-
2530           tains an explicit CR or LF reference, and so advances only by one char-
2531           acter after the first failure.
2532    
2533           An explicit match for CR of LF is either a literal appearance of one of
2534           those  characters,  or  one  of the \r or \n escape sequences. Implicit
2535           matches such as [^X] do not count, nor does \s (which includes  CR  and
2536           LF in the characters that it matches).
2537    
2538           Notwithstanding  the above, anomalous effects may still occur when CRLF
2539           is a valid newline sequence and explicit \r or \n escapes appear in the
2540           pattern.
2541    
2542           PCRE_NOTBOL           PCRE_NOTBOL
2543    
# Line 1844  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 2565  MATCHING A PATTERN: THE TRADITIONAL FUNC
2565    
2566           a?b?           a?b?
2567    
2568         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
2569         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
2570         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-
2571         rences of "a" or "b".         rences of "a" or "b".
2572    
2573         Perl has no direct equivalent of PCRE_NOTEMPTY, but it does make a spe-           PCRE_NOTEMPTY_ATSTART
2574         cial  case  of  a  pattern match of the empty string within its split()  
2575         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
2576         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
2577         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.
2578         if  that  fails by advancing the starting offset (see below) and trying  
2579         an ordinary match again. There is some code that demonstrates how to do         Perl    has    no    direct    equivalent    of    PCRE_NOTEMPTY     or
2580         this in the pcredemo.c sample program.         PCRE_NOTEMPTY_ATSTART,  but  it  does  make a special case of a pattern
2581           match of the empty string within its split() function, and  when  using
2582           the  /g  modifier.  It  is  possible  to emulate Perl's behaviour after
2583           matching a null string by first trying the match again at the same off-
2584           set  with  PCRE_NOTEMPTY_ATSTART  and  PCRE_ANCHORED,  and then if that
2585           fails, by advancing the starting offset (see below) and trying an ordi-
2586           nary  match  again. There is some code that demonstrates how to do this
2587           in the pcredemo sample program. In the most general case, you  have  to
2588           check  to  see  if the newline convention recognizes CRLF as a newline,
2589           and if so, and the current character is CR followed by LF, advance  the
2590           starting offset by two characters instead of one.
2591    
2592             PCRE_NO_START_OPTIMIZE
2593    
2594           There  are a number of optimizations that pcre_exec() uses at the start
2595           of a match, in order to speed up the process. For  example,  if  it  is
2596           known that an unanchored match must start with a specific character, it
2597           searches the subject for that character, and fails  immediately  if  it
2598           cannot  find  it,  without actually running the main matching function.
2599           This means that a special item such as (*COMMIT) at the start of a pat-
2600           tern  is  not  considered until after a suitable starting point for the
2601           match has been found. When callouts or (*MARK) items are in use,  these
2602           "start-up" optimizations can cause them to be skipped if the pattern is
2603           never actually used. The start-up optimizations are in  effect  a  pre-
2604           scan of the subject that takes place before the pattern is run.
2605    
2606           The  PCRE_NO_START_OPTIMIZE option disables the start-up optimizations,
2607           possibly causing performance to suffer,  but  ensuring  that  in  cases
2608           where  the  result is "no match", the callouts do occur, and that items
2609           such as (*COMMIT) and (*MARK) are considered at every possible starting
2610           position  in  the  subject  string. If PCRE_NO_START_OPTIMIZE is set at
2611           compile time, it cannot be unset at matching time.
2612    
2613           Setting PCRE_NO_START_OPTIMIZE can change the  outcome  of  a  matching
2614           operation.  Consider the pattern
2615    
2616             (*COMMIT)ABC
2617    
2618           When  this  is  compiled, PCRE records the fact that a match must start
2619           with the character "A". Suppose the subject  string  is  "DEFABC".  The
2620           start-up  optimization  scans along the subject, finds "A" and runs the
2621           first match attempt from there. The (*COMMIT) item means that the  pat-
2622           tern  must  match the current starting position, which in this case, it
2623           does. However, if the same match  is  run  with  PCRE_NO_START_OPTIMIZE
2624           set,  the  initial  scan  along the subject string does not happen. The
2625           first match attempt is run starting  from  "D"  and  when  this  fails,
2626           (*COMMIT)  prevents  any  further  matches  being tried, so the overall
2627           result is "no match". If the pattern is studied,  more  start-up  opti-
2628           mizations  may  be  used. For example, a minimum length for the subject
2629           may be recorded. Consider the pattern
2630    
2631             (*MARK:A)(X|Y)
2632    
2633           The minimum length for a match is one  character.  If  the  subject  is
2634           "ABC",  there  will  be  attempts  to  match "ABC", "BC", "C", and then
2635           finally an empty string.  If the pattern is studied, the final  attempt
2636           does  not take place, because PCRE knows that the subject is too short,
2637           and so the (*MARK) is never encountered.  In this  case,  studying  the
2638           pattern  does  not  affect the overall match result, which is still "no
2639           match", but it does affect the auxiliary information that is returned.
2640    
2641           PCRE_NO_UTF8_CHECK           PCRE_NO_UTF8_CHECK
2642    
2643         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
2644         UTF-8 string is automatically checked when pcre_exec() is  subsequently         UTF-8  string is automatically checked when pcre_exec() is subsequently
2645         called.   The  value  of  startoffset is also checked to ensure that it         called.  The value of startoffset is also checked  to  ensure  that  it
2646         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
2647         the  validity  of  UTF-8 strings in the section on UTF-8 support in the         the validity of UTF-8 strings in the pcreunicode page.  If  an  invalid
2648         main pcre page. If  an  invalid  UTF-8  sequence  of  bytes  is  found,         sequence   of   bytes   is   found,   pcre_exec()   returns  the  error
2649         pcre_exec()  returns  the error PCRE_ERROR_BADUTF8. If startoffset con-         PCRE_ERROR_BADUTF8 or, if PCRE_PARTIAL_HARD is set and the problem is a
2650         tains an invalid value, PCRE_ERROR_BADUTF8_OFFSET is returned.         truncated character at the end of the subject, PCRE_ERROR_SHORTUTF8. In
2651           both cases, information about the precise nature of the error may  also
2652           be  returned (see the descriptions of these errors in the section enti-
2653           tled Error return values from pcre_exec() below).  If startoffset  con-
2654           tains a value that does not point to the start of a UTF-8 character (or
2655           to the end of the subject), PCRE_ERROR_BADUTF8_OFFSET is returned.
2656    
2657         If you already know that your subject is valid, and you  want  to  skip         If you already know that your subject is valid, and you  want  to  skip
2658         these    checks    for   performance   reasons,   you   can   set   the         these    checks    for   performance   reasons,   you   can   set   the
# Line 1875  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 2660  MATCHING A PATTERN: THE TRADITIONAL FUNC
2660         do  this  for the second and subsequent calls to pcre_exec() if you are         do  this  for the second and subsequent calls to pcre_exec() if you are
2661         making repeated calls to find all  the  matches  in  a  single  subject         making repeated calls to find all  the  matches  in  a  single  subject
2662         string.  However,  you  should  be  sure  that the value of startoffset         string.  However,  you  should  be  sure  that the value of startoffset
2663         points to the start of a UTF-8 character.  When  PCRE_NO_UTF8_CHECK  is         points to the start of a character (or the end of  the  subject).  When
2664         set,  the  effect of passing an invalid UTF-8 string as a subject, or a         PCRE_NO_UTF8_CHECK is set, the effect of passing an invalid string as a
2665         value of startoffset that does not point to the start of a UTF-8  char-         subject or an invalid value of startoffset is undefined.  Your  program
2666         acter, is undefined. Your program may crash.         may crash.
2667    
2668           PCRE_PARTIAL           PCRE_PARTIAL_HARD
2669             PCRE_PARTIAL_SOFT
2670         This  option  turns  on  the  partial  matching feature. If the subject  
2671         string fails to match the pattern, but at some point during the  match-         These  options turn on the partial matching feature. For backwards com-
2672         ing  process  the  end of the subject was reached (that is, the subject         patibility, PCRE_PARTIAL is a synonym for PCRE_PARTIAL_SOFT. A  partial
2673         partially matches the pattern and the failure to  match  occurred  only         match  occurs if the end of the subject string is reached successfully,
2674         because  there were not enough subject characters), pcre_exec() returns         but there are not enough subject characters to complete the  match.  If
2675         PCRE_ERROR_PARTIAL instead of PCRE_ERROR_NOMATCH. When PCRE_PARTIAL  is         this happens when PCRE_PARTIAL_SOFT (but not PCRE_PARTIAL_HARD) is set,
2676         used,  there  are restrictions on what may appear in the pattern. These         matching continues by testing any remaining alternatives.  Only  if  no
2677         are discussed in the pcrepartial documentation.         complete  match  can be found is PCRE_ERROR_PARTIAL returned instead of
2678           PCRE_ERROR_NOMATCH. In other words,  PCRE_PARTIAL_SOFT  says  that  the
2679           caller  is  prepared to handle a partial match, but only if no complete
2680           match can be found.
2681    
2682           If PCRE_PARTIAL_HARD is set, it overrides  PCRE_PARTIAL_SOFT.  In  this
2683           case,  if  a  partial  match  is found, pcre_exec() immediately returns
2684           PCRE_ERROR_PARTIAL, without  considering  any  other  alternatives.  In
2685           other  words, when PCRE_PARTIAL_HARD is set, a partial match is consid-
2686           ered to be more important that an alternative complete match.
2687    
2688           In both cases, the portion of the string that was  inspected  when  the
2689           partial match was found is set as the first matching string. There is a
2690           more detailed discussion of partial and  multi-segment  matching,  with
2691           examples, in the pcrepartial documentation.
2692    
2693     The string to be matched by pcre_exec()     The string to be matched by pcre_exec()
2694    
2695         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
2696         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.
2697         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,
2698         Unlike  the  pattern string, the subject may contain binary zero bytes.         pcre_exec() returns PCRE_ERROR_BADOFFSET. When the starting  offset  is
2699         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,
2700         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
2701           must  point  to  the start of a UTF-8 character (or the end of the sub-
2702           ject). Unlike the pattern string, the subject may contain  binary  zero
2703           bytes.
2704    
2705         A  non-zero  starting offset is useful when searching for another match         A  non-zero  starting offset is useful when searching for another match
2706         in the same subject by calling pcre_exec() again after a previous  suc-         in the same subject by calling pcre_exec() again after a previous  suc-
# Line 1919  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 2721  MATCHING A PATTERN: THE TRADITIONAL FUNC
2721         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
2722         discover that it is preceded by a letter.         discover that it is preceded by a letter.
2723    
2724         If a non-zero starting offset is passed when the pattern  is  anchored,         Finding all the matches in a subject is tricky  when  the  pattern  can
2725           match an empty string. It is possible to emulate Perl's /g behaviour by
2726           first  trying  the  match  again  at  the   same   offset,   with   the
2727           PCRE_NOTEMPTY_ATSTART  and  PCRE_ANCHORED  options,  and  then  if that
2728           fails, advancing the starting  offset  and  trying  an  ordinary  match
2729           again. There is some code that demonstrates how to do this in the pcre-
2730           demo sample program. In the most general case, you have to check to see
2731           if  the newline convention recognizes CRLF as a newline, and if so, and
2732           the current character is CR followed by LF, advance the starting offset
2733           by two characters instead of one.
2734    
2735           If  a  non-zero starting offset is passed when the pattern is anchored,
2736         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
2737         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
2738         subject.         subject.
2739    
2740     How pcre_exec() returns captured substrings     How pcre_exec() returns captured substrings
2741    
2742         In  general, a pattern matches a certain portion of the subject, and in         In general, a pattern matches a certain portion of the subject, and  in
2743         addition, further substrings from the subject  may  be  picked  out  by         addition,  further  substrings  from  the  subject may be picked out by
2744         parts  of  the  pattern.  Following the usage in Jeffrey Friedl's book,         parts of the pattern. Following the usage  in  Jeffrey  Friedl's  book,
2745         this is called "capturing" in what follows, and the  phrase  "capturing         this  is  called "capturing" in what follows, and the phrase "capturing
2746         subpattern"  is  used for a fragment of a pattern that picks out a sub-         subpattern" is used for a fragment of a pattern that picks out  a  sub-
2747         string. PCRE supports several other kinds of  parenthesized  subpattern         string.  PCRE  supports several other kinds of parenthesized subpattern
2748         that do not cause substrings to be captured.         that do not cause substrings to be captured.
2749    
2750         Captured  substrings are returned to the caller via a vector of integer         Captured substrings are returned to the caller via a vector of integers
2751         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-
2752         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:
2753         Note: this argument is NOT the size of ovector in bytes.         this argument is NOT the size of ovector in bytes.
2754    
2755         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-
2756         strings,  each  substring using a pair of integers. The remaining third         strings, each substring using a pair of integers. The  remaining  third
2757         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-
2758         turing  subpatterns, and is not available for passing back information.         turing subpatterns, and is not available for passing back  information.
2759         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
2760         it is not, it is rounded down.         it is not, it is rounded down.
2761    
2762         When  a  match  is successful, information about captured substrings is         When a match is successful, information about  captured  substrings  is
2763         returned in pairs of integers, starting at the  beginning  of  ovector,         returned  in  pairs  of integers, starting at the beginning of ovector,
2764         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
2765         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
2766         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
2767         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
2768         tor[1],  identify  the  portion  of  the  subject string matched by the         byte offsets, even in UTF-8 mode. They are not character counts.
2769         entire pattern. The next pair is used for the first  capturing  subpat-  
2770         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
2771         highest numbered pair that has been set. For example, if two substrings         portion  of  the subject string matched by the entire pattern. The next
2772         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
2773         subpatterns, the return value from a successful match is 1,  indicating         returned by pcre_exec() is one more than the highest numbered pair that
2774         that just the first pair of offsets has been set.         has been set.  For example, if two substrings have been  captured,  the
2775           returned  value is 3. If there are no capturing subpatterns, the return
2776           value from a successful match is 1, indicating that just the first pair
2777           of offsets has been set.
2778    
2779         If a capturing subpattern is matched repeatedly, it is the last portion         If a capturing subpattern is matched repeatedly, it is the last portion
2780         of the string that it matched that is returned.         of the string that it matched that is returned.
2781    
2782         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,
2783         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
2784         function returns a value of zero. In particular, if the substring  off-         function returns a value of zero. If neither the actual string  matched
2785         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
2786         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-
2787         references  and  the  ovector is not big enough to remember the related         tern  contains  back  references  and  the ovector is not big enough to
2788         substrings, PCRE has to get additional memory for use during  matching.         remember the related substrings, PCRE has to get additional memory  for
2789         Thus it is usually advisable to supply an ovector.         use  during matching. Thus it is usually advisable to supply an ovector
2790           of reasonable size.
2791    
2792           There are some cases where zero is returned  (indicating  vector  over-
2793           flow)  when  in fact the vector is exactly the right size for the final
2794           match. For example, consider the pattern
2795    
2796             (a)(?:(b)c|bd)
2797    
2798           If a vector of 6 elements (allowing for only 1 captured  substring)  is
2799           given with subject string "abd", pcre_exec() will try to set the second
2800           captured string, thereby recording a vector overflow, before failing to
2801           match  "c"  and  backing  up  to  try  the second alternative. The zero
2802           return, however, does correctly indicate that  the  maximum  number  of
2803           slots (namely 2) have been filled. In similar cases where there is tem-
2804           porary overflow, but the final number of used slots  is  actually  less
2805           than the maximum, a non-zero value is returned.
2806    
2807         The  pcre_info()  function  can  be used to find out how many capturing         The pcre_fullinfo() function can be used to find out how many capturing
2808         subpatterns there are in a compiled  pattern.  The  smallest  size  for         subpatterns there are in a compiled  pattern.  The  smallest  size  for
2809         ovector  that  will allow for n captured substrings, in addition to the         ovector  that  will allow for n captured substrings, in addition to the
2810         offsets of the substring matched by the whole pattern, is (n+1)*3.         offsets of the substring matched by the whole pattern, is (n+1)*3.
# Line 1988  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 2820  MATCHING A PATTERN: THE TRADITIONAL FUNC
2820         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
2821         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
2822         matched. The return from the function is 2, because  the  highest  used         matched. The return from the function is 2, because  the  highest  used
2823         capturing subpattern number is 1. However, you can refer to the offsets         capturing  subpattern  number  is 1, and the offsets for for the second
2824         for the second and third capturing subpatterns if  you  wish  (assuming         and third capturing subpatterns (assuming the vector is  large  enough,
2825         the vector is large enough, of course).         of course) are set to -1.
2826    
2827           Note:  Elements  in  the first two-thirds of ovector that do not corre-
2828           spond to capturing parentheses in the pattern are never  changed.  That
2829           is,  if  a pattern contains n capturing parentheses, no more than ovec-
2830           tor[0] to ovector[2n+1] are set by pcre_exec(). The other elements  (in
2831           the first two-thirds) retain whatever values they previously had.
2832    
2833         Some  convenience  functions  are  provided for extracting the captured         Some  convenience  functions  are  provided for extracting the captured
2834         substrings as separate strings. These are described below.         substrings as separate strings. These are described below.
# Line 2035  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 2873  MATCHING A PATTERN: THE TRADITIONAL FUNC
2873         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
2874         memory is automatically freed at the end of matching.         memory is automatically freed at the end of matching.
2875    
2876           This error is also given if pcre_stack_malloc() fails  in  pcre_exec().
2877           This  can happen only when PCRE has been compiled with --disable-stack-
2878           for-recursion.
2879    
2880           PCRE_ERROR_NOSUBSTRING    (-7)           PCRE_ERROR_NOSUBSTRING    (-7)
2881    
2882         This error is used by the pcre_copy_substring(),  pcre_get_substring(),         This error is used by the pcre_copy_substring(),  pcre_get_substring(),
# Line 2056  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 2898  MATCHING A PATTERN: THE TRADITIONAL FUNC
2898           PCRE_ERROR_BADUTF8        (-10)           PCRE_ERROR_BADUTF8        (-10)
2899    
2900         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
2901         subject.         subject,  and the PCRE_NO_UTF8_CHECK option was not set. If the size of
2902           the output vector (ovecsize) is at least 2,  the  byte  offset  to  the
2903           start  of  the  the invalid UTF-8 character is placed in the first ele-
2904           ment, and a reason code is placed in the  second  element.  The  reason
2905           codes are listed in the following section.  For backward compatibility,
2906           if PCRE_PARTIAL_HARD is set and the problem is a truncated UTF-8  char-
2907           acter   at   the   end   of   the   subject  (reason  codes  1  to  5),
2908           PCRE_ERROR_SHORTUTF8 is returned instead of PCRE_ERROR_BADUTF8.
2909    
2910           PCRE_ERROR_BADUTF8_OFFSET (-11)           PCRE_ERROR_BADUTF8_OFFSET (-11)
2911    
2912         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
2913           found  to be valid (the PCRE_NO_UTF8_CHECK option was not set), but the
2914         value of startoffset did not point to the beginning of a UTF-8  charac-         value of startoffset did not point to the beginning of a UTF-8  charac-
2915         ter.         ter or the end of the subject.
2916    
2917           PCRE_ERROR_PARTIAL        (-12)           PCRE_ERROR_PARTIAL        (-12)
2918    
# Line 2071  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 2921  MATCHING A PATTERN: THE TRADITIONAL FUNC
2921    
2922           PCRE_ERROR_BADPARTIAL     (-13)           PCRE_ERROR_BADPARTIAL     (-13)
2923    
2924         The PCRE_PARTIAL option was used with  a  compiled  pattern  containing         This code is no longer in  use.  It  was  formerly  returned  when  the
2925         items  that are not supported for partial matching. See the pcrepartial         PCRE_PARTIAL  option  was used with a compiled pattern containing items
2926         documentation for details of partial matching.         that were  not  supported  for  partial  matching.  From  release  8.00
2927           onwards, there are no restrictions on partial matching.
2928    
2929           PCRE_ERROR_INTERNAL       (-14)           PCRE_ERROR_INTERNAL       (-14)
2930    
2931         An unexpected internal error has occurred. This error could  be  caused         An  unexpected  internal error has occurred. This error could be caused
2932         by a bug in PCRE or by overwriting of the compiled pattern.         by a bug in PCRE or by overwriting of the compiled pattern.
2933    
2934           PCRE_ERROR_BADCOUNT       (-15)           PCRE_ERROR_BADCOUNT       (-15)
2935    
2936         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.
2937    
2938           PCRE_ERROR_RECURSIONLIMIT (-21)           PCRE_ERROR_RECURSIONLIMIT (-21)
2939    
# Line 2094  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 2945  MATCHING A PATTERN: THE TRADITIONAL FUNC
2945    
2946         An invalid combination of PCRE_NEWLINE_xxx options was given.         An invalid combination of PCRE_NEWLINE_xxx options was given.
2947    
2948             PCRE_ERROR_BADOFFSET      (-24)
2949    
2950           The value of startoffset was negative or greater than the length of the
2951           subject, that is, the value in length.
2952    
2953             PCRE_ERROR_SHORTUTF8      (-25)
2954    
2955           This  error  is returned instead of PCRE_ERROR_BADUTF8 when the subject
2956           string ends with a truncated UTF-8 character and the  PCRE_PARTIAL_HARD
2957           option  is  set.   Information  about  the  failure  is returned as for
2958           PCRE_ERROR_BADUTF8. It is in fact sufficient to detect this  case,  but
2959           this  special error code for PCRE_PARTIAL_HARD precedes the implementa-
2960           tion of returned information; it is retained for backwards  compatibil-
2961           ity.
2962    
2963             PCRE_ERROR_RECURSELOOP    (-26)
2964    
2965           This error is returned when pcre_exec() detects a recursion loop within
2966           the pattern. Specifically, it means that either the whole pattern or  a
2967           subpattern  has been called recursively for the second time at the same
2968           position in the subject string. Some simple patterns that might do this
2969           are  detected  and faulted at compile time, but more complicated cases,
2970           in particular mutual recursions between two different subpatterns, can-
2971           not be detected until run time.
2972    
2973             PCRE_ERROR_JIT_STACKLIMIT (-27)
2974    
2975           This  error  is  returned  when a pattern that was successfully studied
2976           using the PCRE_STUDY_JIT_COMPILE option is being matched, but the  mem-
2977           ory  available  for  the  just-in-time  processing  stack  is not large
2978           enough. See the pcrejit documentation for more details.
2979    
2980             PCRE_ERROR_BADMODE (-28)
2981    
2982           This error is given if a pattern that was compiled by the 8-bit library
2983           is passed to a 16-bit library function, or vice versa.
2984    
2985             PCRE_ERROR_BADENDIANNESS (-29)
2986    
2987           This  error  is  given  if  a  pattern  that  was compiled and saved is
2988           reloaded on a host with  different  endianness.  The  utility  function
2989           pcre_pattern_to_host_byte_order() can be used to convert such a pattern
2990           so that it runs on the new host.
2991    
2992         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().
2993    
2994       Reason codes for invalid UTF-8 strings
2995    
2996           This section applies only  to  the  8-bit  library.  The  corresponding
2997           information for the 16-bit library is given in the pcre16 page.
2998    
2999           When pcre_exec() returns either PCRE_ERROR_BADUTF8 or PCRE_ERROR_SHORT-
3000           UTF8, and the size of the output vector (ovecsize) is at least  2,  the
3001           offset  of  the  start  of the invalid UTF-8 character is placed in the
3002           first output vector element (ovector[0]) and a reason code is placed in
3003           the  second  element  (ovector[1]). The reason codes are given names in
3004           the pcre.h header file:
3005    
3006             PCRE_UTF8_ERR1
3007             PCRE_UTF8_ERR2
3008             PCRE_UTF8_ERR3
3009             PCRE_UTF8_ERR4
3010             PCRE_UTF8_ERR5
3011    
3012           The string ends with a truncated UTF-8 character;  the  code  specifies
3013           how  many bytes are missing (1 to 5). Although RFC 3629 restricts UTF-8
3014           characters to be no longer than 4 bytes, the  encoding  scheme  (origi-
3015           nally  defined  by  RFC  2279)  allows  for  up to 6 bytes, and this is
3016           checked first; hence the possibility of 4 or 5 missing bytes.
3017    
3018             PCRE_UTF8_ERR6
3019             PCRE_UTF8_ERR7
3020             PCRE_UTF8_ERR8
3021             PCRE_UTF8_ERR9
3022             PCRE_UTF8_ERR10
3023    
3024           The two most significant bits of the 2nd, 3rd, 4th, 5th, or 6th byte of
3025           the  character  do  not have the binary value 0b10 (that is, either the
3026           most significant bit is 0, or the next bit is 1).
3027    
3028             PCRE_UTF8_ERR11
3029             PCRE_UTF8_ERR12
3030    
3031           A character that is valid by the RFC 2279 rules is either 5 or 6  bytes
3032           long; these code points are excluded by RFC 3629.
3033    
3034             PCRE_UTF8_ERR13
3035    
3036           A  4-byte character has a value greater than 0x10fff; these code points
3037           are excluded by RFC 3629.
3038    
3039             PCRE_UTF8_ERR14
3040    
3041           A 3-byte character has a value in the  range  0xd800  to  0xdfff;  this
3042           range  of code points are reserved by RFC 3629 for use with UTF-16, and
3043           so are excluded from UTF-8.
3044    
3045             PCRE_UTF8_ERR15
3046             PCRE_UTF8_ERR16
3047             PCRE_UTF8_ERR17
3048             PCRE_UTF8_ERR18
3049             PCRE_UTF8_ERR19
3050    
3051           A 2-, 3-, 4-, 5-, or 6-byte character is "overlong", that is, it  codes
3052           for  a  value that can be represented by fewer bytes, which is invalid.
3053           For example, the two bytes 0xc0, 0xae give the value 0x2e,  whose  cor-
3054           rect coding uses just one byte.
3055    
3056             PCRE_UTF8_ERR20
3057    
3058           The two most significant bits of the first byte of a character have the
3059           binary value 0b10 (that is, the most significant bit is 1 and the  sec-
3060           ond  is  0). Such a byte can only validly occur as the second or subse-
3061           quent byte of a multi-byte character.
3062    
3063             PCRE_UTF8_ERR21
3064    
3065           The first byte of a character has the value 0xfe or 0xff. These  values
3066           can never occur in a valid UTF-8 string.
3067    
3068    
3069  EXTRACTING CAPTURED SUBSTRINGS BY NUMBER  EXTRACTING CAPTURED SUBSTRINGS BY NUMBER
3070    
# Line 2110  EXTRACTING CAPTURED SUBSTRINGS BY NUMBER Line 3079  EXTRACTING CAPTURED SUBSTRINGS BY NUMBER
3079         int pcre_get_substring_list(const char *subject,         int pcre_get_substring_list(const char *subject,
3080              int *ovector, int stringcount, const char ***listptr);              int *ovector, int stringcount, const char ***listptr);
3081    
3082         Captured substrings can be  accessed  directly  by  using  the  offsets         Captured  substrings  can  be  accessed  directly  by using the offsets
3083         returned  by  pcre_exec()  in  ovector.  For convenience, the functions         returned by pcre_exec() in  ovector.  For  convenience,  the  functions
3084         pcre_copy_substring(),    pcre_get_substring(),    and    pcre_get_sub-         pcre_copy_substring(),    pcre_get_substring(),    and    pcre_get_sub-
3085         string_list()  are  provided for extracting captured substrings as new,         string_list() are provided for extracting captured substrings  as  new,
3086         separate, zero-terminated strings. These functions identify  substrings         separate,  zero-terminated strings. These functions identify substrings
3087         by  number.  The  next section describes functions for extracting named         by number. The next section describes functions  for  extracting  named
3088         substrings.         substrings.
3089    
3090         A substring that contains a binary zero is correctly extracted and  has         A  substring that contains a binary zero is correctly extracted and has
3091         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
3092         string.  However, you can process such a string  by  referring  to  the         string.   However,  you  can  process such a string by referring to the
3093         length  that  is  returned  by  pcre_copy_substring() and pcre_get_sub-         length that is  returned  by  pcre_copy_substring()  and  pcre_get_sub-
3094         string().  Unfortunately, the interface to pcre_get_substring_list() is         string().  Unfortunately, the interface to pcre_get_substring_list() is
3095         not  adequate for handling strings containing binary zeros, because the         not adequate for handling strings containing binary zeros, because  the
3096         end of the final string is not independently indicated.         end of the final string is not independently indicated.
3097    
3098         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-
3099         tions:  subject  is  the subject string that has just been successfully         tions: subject is the subject string that has  just  been  successfully
3100         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
3101         passed to pcre_exec(), and stringcount is the number of substrings that         passed to pcre_exec(), and stringcount is the number of substrings that
3102         were captured by the match, including the substring  that  matched  the         were  captured  by  the match, including the substring that matched the
3103         entire regular expression. This is the value returned by pcre_exec() if         entire regular expression. This is the value returned by pcre_exec() if
3104         it is greater than zero. If pcre_exec() returned zero, indicating  that         it  is greater than zero. If pcre_exec() returned zero, indicating that
3105         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
3106         be the number of elements in the vector divided by three.         be the number of elements in the vector divided by three.
3107    
3108         The functions pcre_copy_substring() and pcre_get_substring() extract  a         The  functions pcre_copy_substring() and pcre_get_substring() extract a
3109         single  substring,  whose  number  is given as stringnumber. A value of         single substring, whose number is given as  stringnumber.  A  value  of
3110         zero extracts the substring that matched the  entire  pattern,  whereas         zero  extracts  the  substring that matched the entire pattern, whereas
3111         higher  values  extract  the  captured  substrings.  For pcre_copy_sub-         higher values  extract  the  captured  substrings.  For  pcre_copy_sub-
3112         string(), the string is placed in buffer,  whose  length  is  given  by         string(),  the  string  is  placed  in buffer, whose length is given by
3113         buffersize,  while  for  pcre_get_substring()  a new block of memory is         buffersize, while for pcre_get_substring() a new  block  of  memory  is
3114         obtained via pcre_malloc, and its address is  returned  via  stringptr.         obtained  via  pcre_malloc,  and its address is returned via stringptr.
3115         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
3116         the terminating zero, or one of these error codes:         the terminating zero, or one of these error codes:
3117    
3118           PCRE_ERROR_NOMEMORY       (-6)           PCRE_ERROR_NOMEMORY       (-6)
3119    
3120         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
3121         get memory failed for pcre_get_substring().         get memory failed for pcre_get_substring().
3122    
3123           PCRE_ERROR_NOSUBSTRING    (-7)           PCRE_ERROR_NOSUBSTRING    (-7)
3124    
3125         There is no substring whose number is stringnumber.         There is no substring whose number is stringnumber.
3126    
3127         The  pcre_get_substring_list()  function  extracts  all  available sub-         The pcre_get_substring_list()  function  extracts  all  available  sub-
3128         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
3129         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
3130         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
3131         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
3132         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
3133         error code         error code
3134    
3135           PCRE_ERROR_NOMEMORY       (-6)           PCRE_ERROR_NOMEMORY       (-6)
3136    
3137         if the attempt to get the memory block failed.         if the attempt to get the memory block failed.
3138    
3139         When  any of these functions encounter a substring that is unset, which         When any of these functions encounter a substring that is unset,  which
3140         can happen when capturing subpattern number n+1 matches  some  part  of         can  happen  when  capturing subpattern number n+1 matches some part of
3141         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
3142         empty string. This can be distinguished from a genuine zero-length sub-         empty string. This can be distinguished from a genuine zero-length sub-
3143         string  by inspecting the appropriate offset in ovector, which is nega-         string by inspecting the appropriate offset in ovector, which is  nega-
3144         tive for unset substrings.         tive for unset substrings.
3145    
3146         The two convenience functions pcre_free_substring() and  pcre_free_sub-         The  two convenience functions pcre_free_substring() and pcre_free_sub-
3147         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
3148         call  of  pcre_get_substring()  or  pcre_get_substring_list(),  respec-         call  of  pcre_get_substring()  or  pcre_get_substring_list(),  respec-
3149         tively.  They  do  nothing  more  than  call the function pointed to by         tively. They do nothing more than  call  the  function  pointed  to  by
3150         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.
3151         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-
3152         cial  interface  to  another  programming  language  that  cannot   use         cial   interface  to  another  programming  language  that  cannot  use
3153         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-
3154         vided.         vided.
3155    
3156    
# Line 2200  EXTRACTING CAPTURED SUBSTRINGS BY NAME Line 3169  EXTRACTING CAPTURED SUBSTRINGS BY NAME
3169              int stringcount, const char *stringname,              int stringcount, const char *stringname,
3170              const char **stringptr);              const char **stringptr);
3171    
3172         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-
3173         ber.  For example, for this pattern         ber.  For example, for this pattern
3174    
3175           (a+)b(?<xxx>\d+)...           (a+)b(?<xxx>\d+)...
# Line 2209  EXTRACTING CAPTURED SUBSTRINGS BY NAME Line 3178  EXTRACTING CAPTURED SUBSTRINGS BY NAME
3178         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
3179         name by calling pcre_get_stringnumber(). The first argument is the com-         name by calling pcre_get_stringnumber(). The first argument is the com-
3180         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
3181         the  subpattern  number,  or PCRE_ERROR_NOSUBSTRING (-7) if there is no         the subpattern number, or PCRE_ERROR_NOSUBSTRING (-7) if  there  is  no
3182         subpattern of that name.         subpattern of that name.
3183    
3184         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
3185         the functions described in the previous section. For convenience, there         the functions described in the previous section. For convenience, there
3186         are also two functions that do the whole job.         are also two functions that do the whole job.
3187    
3188         Most   of   the   arguments    of    pcre_copy_named_substring()    and         Most    of    the    arguments   of   pcre_copy_named_substring()   and
3189         pcre_get_named_substring()  are  the  same  as  those for the similarly         pcre_get_named_substring() are the same  as  those  for  the  similarly
3190         named functions that extract by number. As these are described  in  the         named  functions  that extract by number. As these are described in the
3191         previous  section,  they  are not re-described here. There are just two         previous section, they are not re-described here. There  are  just  two
3192         differences:         differences:
3193    
3194         First, instead of a substring number, a substring name is  given.  Sec-         First,  instead  of a substring number, a substring name is given. Sec-
3195         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
3196         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
3197         name-to-number translation table.         name-to-number translation table.
3198    
3199         These  functions call pcre_get_stringnumber(), and if it succeeds, they         These functions call pcre_get_stringnumber(), and if it succeeds,  they
3200         then call pcre_copy_substring() or pcre_get_substring(),  as  appropri-         then  call  pcre_copy_substring() or pcre_get_substring(), as appropri-
3201         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
3202         behaviour may not be what you want (see the next section).         behaviour may not be what you want (see the next section).
3203    
3204           Warning: If the pattern uses the (?| feature to set up multiple subpat-
3205           terns with the same number, as described in the  section  on  duplicate
3206           subpattern  numbers  in  the  pcrepattern page, you cannot use names to
3207           distinguish the different subpatterns, because names are  not  included
3208           in  the compiled code. The matching process uses only numbers. For this
3209           reason, the use of different names for subpatterns of the  same  number
3210           causes an error at compile time.
3211    
3212    
3213  DUPLICATE SUBPATTERN NAMES  DUPLICATE SUBPATTERN NAMES
3214    
3215         int pcre_get_stringtable_entries(const pcre *code,         int pcre_get_stringtable_entries(const pcre *code,
3216              const char *name, char **first, char **last);              const char *name, char **first, char **last);
3217    
3218         When a pattern is compiled with the  PCRE_DUPNAMES  option,  names  for         When  a  pattern  is  compiled with the PCRE_DUPNAMES option, names for
3219         subpatterns  are  not  required  to  be unique. Normally, patterns with         subpatterns are not required to be unique. (Duplicate names are  always
3220         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 (?|
3221         subpatterns  participates. An example is shown in the pcrepattern docu-         feature. Indeed, if such subpatterns are named, they  are  required  to
3222         mentation.         use the same names.)
3223    
3224         When   duplicates   are   present,   pcre_copy_named_substring()    and         Normally, patterns with duplicate names are such that in any one match,
3225         pcre_get_named_substring()  return the first substring corresponding to         only one of the named subpatterns participates. An example is shown  in
3226         the given name that is set. If  none  are  set,  PCRE_ERROR_NOSUBSTRING         the pcrepattern documentation.
3227         (-7)  is  returned;  no  data  is returned. The pcre_get_stringnumber()  
3228         function returns one of the numbers that are associated with the  name,         When    duplicates   are   present,   pcre_copy_named_substring()   and
3229           pcre_get_named_substring() return the first substring corresponding  to
3230           the  given  name  that  is set. If none are set, PCRE_ERROR_NOSUBSTRING
3231           (-7) is returned; no  data  is  returned.  The  pcre_get_stringnumber()
3232           function  returns one of the numbers that are associated with the name,
3233         but it is not defined which it is.         but it is not defined which it is.
3234    
3235         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
3236         name, you must use  the  pcre_get_stringtable_entries()  function.  The         name,  you  must  use  the pcre_get_stringtable_entries() function. The
3237         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
3238         third and fourth are pointers to variables which  are  updated  by  the         third  and  fourth  are  pointers to variables which are updated by the
3239         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
3240         the name-to-number table  for  the  given  name.  The  function  itself         the  name-to-number  table  for  the  given  name.  The function itself
3241         returns  the  length  of  each entry, or PCRE_ERROR_NOSUBSTRING (-7) if         returns the length of each entry,  or  PCRE_ERROR_NOSUBSTRING  (-7)  if
3242         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-
3243         tion  entitled  Information  about  a  pattern.  Given all the relevant         tion entitled Information about a pattern above.  Given all  the  rele-
3244         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
3245         the captured data, if any.         hence the captured data, if any.
3246    
3247    
3248  FINDING ALL POSSIBLE MATCHES  FINDING ALL POSSIBLE MATCHES
3249    
3250         The  traditional  matching  function  uses a similar algorithm to Perl,         The traditional matching function uses a  similar  algorithm  to  Perl,
3251         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
3252         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
3253         possible match, consider using the alternative matching  function  (see         possible  match,  consider using the alternative matching function (see
3254         below)  instead.  If you cannot use the alternative function, but still         below) instead. If you cannot use the alternative function,  but  still
3255         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
3256         of the callout facility, which is described in the pcrecallout documen-         of the callout facility, which is described in the pcrecallout documen-
3257         tation.         tation.
3258    
3259         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-
3260         tern.   When your callout function is called, extract and save the cur-         tern.  When your callout function is called, extract and save the  cur-
3261         rent matched substring. Then return  1,  which  forces  pcre_exec()  to         rent  matched  substring.  Then  return  1, which forces pcre_exec() to
3262         backtrack  and  try other alternatives. Ultimately, when it runs out of         backtrack and try other alternatives. Ultimately, when it runs  out  of
3263         matches, pcre_exec() will yield PCRE_ERROR_NOMATCH.         matches, pcre_exec() will yield PCRE_ERROR_NOMATCH.
3264    
3265    
3266    OBTAINING AN ESTIMATE OF STACK USAGE
3267    
3268           Matching  certain  patterns  using pcre_exec() can use a lot of process
3269           stack, which in certain environments can be  rather  limited  in  size.
3270           Some  users  find it helpful to have an estimate of the amount of stack
3271           that is used by pcre_exec(), to help  them  set  recursion  limits,  as
3272           described  in  the pcrestack documentation. The estimate that is output
3273           by pcretest when called with the -m and -C options is obtained by call-
3274           ing  pcre_exec with the values NULL, NULL, NULL, -999, and -999 for its
3275           first five arguments.
3276    
3277           Normally, if  its  first  argument  is  NULL,  pcre_exec()  immediately
3278           returns  the negative error code PCRE_ERROR_NULL, but with this special
3279           combination of arguments, it returns instead a  negative  number  whose
3280           absolute  value  is the approximate stack frame size in bytes. (A nega-
3281           tive number is used so that it is clear that no  match  has  happened.)
3282           The  value  is  approximate  because  in some cases, recursive calls to
3283           pcre_exec() occur when there are one or two additional variables on the
3284           stack.
3285    
3286           If  PCRE  has  been  compiled  to use the heap instead of the stack for
3287           recursion, the value returned  is  the  size  of  each  block  that  is
3288           obtained from the heap.
3289    
3290    
3291  MATCHING A PATTERN: THE ALTERNATIVE FUNCTION  MATCHING A PATTERN: THE ALTERNATIVE FUNCTION