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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.  The current implementation of PCRE (release         just  a few differences. Some features that appeared in Python and PCRE
23         6.x) corresponds approximately with Perl  5.8,  including  support  for         before they appeared in Perl are also available using the  Python  syn-
24         UTF-8 encoded strings and Unicode general category properties. However,         tax,  there  is  some  support for one or two .NET and Oniguruma syntax
25         this support has to be explicitly enabled; it is not the default.         items, and there is an option for requesting some  minor  changes  that
26           give better JavaScript compatibility.
27         In addition to the Perl-compatible matching function,  PCRE  also  con-  
28         tains  an  alternative matching function that matches the same compiled         Starting with release 8.30, it is possible to compile two separate PCRE
29         patterns in a different way. In certain circumstances, the  alternative         libraries:  the  original,  which  supports  8-bit  character   strings
30         function  has  some  advantages.  For  a discussion of the two matching         (including  UTF-8  strings),  and a second library that supports 16-bit
31         algorithms, see the pcrematching page.         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         PCRE is written in C and released as a C library. A  number  of  people         possible was done by Zoltan Herczeg.
34         have  written  wrappers and interfaces of various kinds. In particular,  
35         Google Inc.  have provided a comprehensive C++  wrapper.  This  is  now         The two libraries contain identical sets of functions, except that  the
36         included as part of the PCRE distribution. The pcrecpp page has details         names  in  the  16-bit  library start with pcre16_ instead of pcre_. To
37         of this interface. Other people's contributions can  be  found  in  the         avoid over-complication and reduce the documentation maintenance  load,
38         Contrib directory at the primary FTP site, which is:         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
51           alternative function that matches the same compiled patterns in a  dif-
52           ferent way. In certain circumstances, the alternative function has some
53           advantages.  For a discussion of the two matching algorithms,  see  the
54           pcrematching page.
55    
56           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,
58           Google  Inc.   have  provided a comprehensive C++ wrapper for the 8-bit
59           library. This is now included as part of  the  PCRE  distribution.  The
60           pcrecpp  page  has  details of this interface. Other people's contribu-
61           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.         tern  and pcrecompat pages. There is a syntax summary in the pcresyntax
69           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
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
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
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 will be slower.  
   
        All values in repeating quantifiers must be less than 65536.  The maxi-  
        mum number of capturing subpatterns is 65535.  
   
        There is no limit to the number of non-capturing subpatterns,  but  the  
        maximum  depth  of  nesting  of  all kinds of parenthesized subpattern,  
        including capturing subpatterns, assertions, and other types of subpat-  
        tern, is 200.  
134    
        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.  
135    
136    REVISION
137    
138  UTF-8 AND UNICODE PROPERTY SUPPORT         Last updated: 10 January 2012
139           Copyright (c) 1997-2012 University of Cambridge.
140    ------------------------------------------------------------------------------
141    
        From release 3.3, PCRE has  had  some  support  for  character  strings  
        encoded  in the UTF-8 format. For release 4.0 this was greatly extended  
        to cover most common requirements, and in release 5.0  additional  sup-  
        port for Unicode general category properties was added.  
   
        In  order  process  UTF-8 strings, you must build PCRE to include UTF-8  
        support in the code, and, in addition,  you  must  call  pcre_compile()  
        with  the PCRE_UTF8 option flag. When you do this, both the pattern and  
        any subject strings that are matched against it are  treated  as  UTF-8  
        strings instead of just strings of bytes.  
142    
143         If  you compile PCRE with UTF-8 support, but do not use it at run time,  PCRE(3)                                                                PCRE(3)
        the library will be a bit bigger, but the additional run time  overhead  
        is  limited  to testing the PCRE_UTF8 flag in several places, so should  
        not be very large.  
144    
145         If PCRE is built with Unicode character property support (which implies  
146         UTF-8  support),  the  escape sequences \p{..}, \P{..}, and \X are sup-  NAME
147         ported.  The available properties that can be tested are limited to the         PCRE - Perl-compatible regular expressions
148         general  category  properties such as Lu for an upper case letter or Nd  
149         for a decimal number. A full list is given in the pcrepattern  documen-         #include <pcre.h>
150         tation. The PCRE library is increased in size by about 90K when Unicode  
151         property support is included.  
152    PCRE 16-BIT API BASIC FUNCTIONS
153         The following comments apply when PCRE is running in UTF-8 mode:  
154           pcre16 *pcre16_compile(PCRE_SPTR16 pattern, int options,
155         1. When you set the PCRE_UTF8 flag, the strings passed as patterns  and              const char **errptr, int *erroffset,
156         subjects  are  checked for validity on entry to the relevant functions.              const unsigned char *tableptr);
157         If an invalid UTF-8 string is passed, an error return is given. In some  
158         situations,  you  may  already  know  that  your strings are valid, and         pcre16 *pcre16_compile2(PCRE_SPTR16 pattern, int options,
159         therefore want to skip these checks in order to improve performance. If              int *errorcodeptr,
160         you  set  the  PCRE_NO_UTF8_CHECK  flag at compile time or at run time,              const char **errptr, int *erroffset,
161         PCRE assumes that the pattern or subject  it  is  given  (respectively)              const unsigned char *tableptr);
162         contains  only valid UTF-8 codes. In this case, it does not diagnose an  
163         invalid UTF-8 string. If you pass an invalid UTF-8 string to PCRE  when         pcre16_extra *pcre16_study(const pcre16 *code, int options,
164         PCRE_NO_UTF8_CHECK  is set, the results are undefined. Your program may              const char **errptr);
165         crash.  
166           void pcre16_free_study(pcre16_extra *extra);
167         2. In a pattern, the escape sequence \x{...}, where the contents of the  
168         braces  is  a  string  of hexadecimal digits, is interpreted as a UTF-8         int pcre16_exec(const pcre16 *code, const pcre16_extra *extra,
169         character whose code number is the given hexadecimal number, for  exam-              PCRE_SPTR16 subject, int length, int startoffset,
170         ple:  \x{1234}.  If a non-hexadecimal digit appears between the braces,              int options, int *ovector, int ovecsize);
171         the item is not recognized.  This escape sequence can be used either as  
172         a literal, or within a character class.         int pcre16_dfa_exec(const pcre16 *code, const pcre16_extra *extra,
173                PCRE_SPTR16 subject, int length, int startoffset,
174         3.  The  original hexadecimal escape sequence, \xhh, matches a two-byte              int options, int *ovector, int ovecsize,
175         UTF-8 character if the value is greater than 127.              int *workspace, int wscount);
176    
177         4. Repeat quantifiers apply to complete UTF-8 characters, not to  indi-  
178         vidual bytes, for example: \x{100}{3}.  PCRE 16-BIT API STRING EXTRACTION FUNCTIONS
179    
180         5.  The dot metacharacter matches one UTF-8 character instead of a sin-         int pcre16_copy_named_substring(const pcre16 *code,
181         gle byte.              PCRE_SPTR16 subject, int *ovector,
182                int stringcount, PCRE_SPTR16 stringname,
183         6. The escape sequence \C can be used to match a single byte  in  UTF-8              PCRE_UCHAR16 *buffer, int buffersize);
184         mode,  but  its  use can lead to some strange effects. This facility is  
185         not available in the alternative matching function, pcre_dfa_exec().         int pcre16_copy_substring(PCRE_SPTR16 subject, int *ovector,
186                int stringcount, int stringnumber, PCRE_UCHAR16 *buffer,
187         7. The character escapes \b, \B, \d, \D, \s, \S, \w, and  \W  correctly              int buffersize);
188         test  characters of any code value, but the characters that PCRE recog-  
189         nizes as digits, spaces, or word characters  remain  the  same  set  as         int pcre16_get_named_substring(const pcre16 *code,
190         before, all with values less than 256. This remains true even when PCRE              PCRE_SPTR16 subject, int *ovector,
191         includes Unicode property support, because to do otherwise  would  slow              int stringcount, PCRE_SPTR16 stringname,
192         down  PCRE in many common cases. If you really want to test for a wider              PCRE_SPTR16 *stringptr);
193         sense of, say, "digit", you must use Unicode  property  tests  such  as  
194         \p{Nd}.         int pcre16_get_stringnumber(const pcre16 *code,
195                PCRE_SPTR16 name);
196         8.  Similarly,  characters that match the POSIX named character classes  
197         are all low-valued characters.         int pcre16_get_stringtable_entries(const pcre16 *code,
198                PCRE_SPTR16 name, PCRE_UCHAR16 **first, PCRE_UCHAR16 **last);
199         9. Case-insensitive matching applies only to  characters  whose  values  
200         are  less than 128, unless PCRE is built with Unicode property support.         int pcre16_get_substring(PCRE_SPTR16 subject, int *ovector,
201         Even when Unicode property support is available, PCRE  still  uses  its              int stringcount, int stringnumber,
202         own  character  tables when checking the case of low-valued characters,              PCRE_SPTR16 *stringptr);
203         so as not to degrade performance.  The Unicode property information  is  
204         used only for characters with higher values.         int pcre16_get_substring_list(PCRE_SPTR16 subject,
205                int *ovector, int stringcount, PCRE_SPTR16 **listptr);
206    
207           void pcre16_free_substring(PCRE_SPTR16 stringptr);
208    
209           void pcre16_free_substring_list(PCRE_SPTR16 *stringptr);
210    
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
455    
456         Philip Hazel         Philip Hazel
457         University Computing Service,         University Computing Service
458         Cambridge CB2 3QG, 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 initial and sur-  
        name, separated by a dot, at the domain ucs.cam.ac.uk.  
460    
461  Last updated: 07 March 2005  REVISION
462  Copyright (c) 1997-2005 University of Cambridge.  
463           Last updated: 08 January 2012
464           Copyright (c) 1997-2012 University of Cambridge.
465  ------------------------------------------------------------------------------  ------------------------------------------------------------------------------
466    
467    
# Line 220  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    
496         The following sections describe certain options whose names begin  with         The following sections include  descriptions  of  options  whose  names
497         --enable  or  --disable. These settings specify changes to the defaults         begin with --enable or --disable. These settings specify changes to the
498         for the configure command. Because of the  way  that  configure  works,         defaults for the configure command. Because of the way  that  configure
499         --enable  and  --disable  always  come  in  pairs, so the complementary         works,  --enable  and --disable always come in pairs, so the complemen-
500         option always exists as well, but as it specifies the  default,  it  is         tary option always exists as well, but as it specifies the default,  it
501         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 90K of tables to the         Including  Unicode  property  support  adds around 30K of tables to the
590         PCRE library, approximately doubling its size. Only the  general  cate-         PCRE library. Only the general category properties such as  Lu  and  Nd
591         gory  properties  such as Lu and Nd are supported. Details are given in         are supported. Details are given in the pcrepattern documentation.
592         the pcrepattern documentation.  
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 treats character 10 (linefeed) as the newline  charac-         By  default,  PCRE interprets the linefeed (LF) character as indicating
614         ter. This is the normal newline character on Unix-like systems. You can         the end of a line. This is the normal newline  character  on  Unix-like
615         compile PCRE to use character 13 (carriage return) instead by adding         systems.  You  can compile PCRE to use carriage return (CR) instead, by
616           adding
617    
618           --enable-newline-is-cr           --enable-newline-is-cr
619    
620         to the configure command. For completeness there is  also  a  --enable-         to the  configure  command.  There  is  also  a  --enable-newline-is-lf
621         newline-is-lf  option,  which explicitly specifies linefeed as the new-         option, which explicitly specifies linefeed as the newline character.
        line character.  
622    
623           Alternatively, you can specify that line endings are to be indicated by
624           the two character sequence CRLF. If you want this, add
625    
626  BUILDING SHARED AND STATIC LIBRARIES           --enable-newline-is-crlf
627    
628         The PCRE building process uses libtool to build both shared and  static         to the configure command. There is a fourth option, specified by
        Unix  libraries by default. You can suppress one of these by adding one  
        of  
629    
630           --disable-shared           --enable-newline-is-anycrlf
          --disable-static  
631    
632         to the configure command, as required.         which causes PCRE to recognize any of the three sequences  CR,  LF,  or
633           CRLF as indicating a line ending. Finally, a fifth option, specified by
634    
635             --enable-newline-is-any
636    
637  POSIX MALLOC USAGE         causes PCRE to recognize any Unicode newline sequence.
638    
639         When PCRE is called through the POSIX interface (see the pcreposix doc-         Whatever  line  ending convention is selected when PCRE is built can be
640         umentation),  additional  working  storage  is required for holding the         overridden when the library functions are called. At build time  it  is
641         pointers to capturing substrings, because PCRE requires three  integers         conventional to use the standard for your operating system.
        per  substring,  whereas  the POSIX interface provides only two. If the  
        number of expected substrings is small, the wrapper function uses space  
        on the stack, because this is faster than using malloc() for each call.  
        The default threshold above which the stack is no longer used is 10; it  
        can be changed by adding a setting such as  
642    
          --with-posix-malloc-threshold=20  
643    
644         to the configure command.  WHAT \R MATCHES
645    
646           By  default,  the  sequence \R in a pattern matches any Unicode newline
647           sequence, whatever has been selected as the line  ending  sequence.  If
648           you specify
649    
650  LIMITING PCRE RESOURCE USAGE           --enable-bsr-anycrlf
651    
652         Internally,  PCRE has a function called match(), which it calls repeat-         the  default  is changed so that \R matches only CR, LF, or CRLF. What-
653         edly  (possibly  recursively)  when  matching  a   pattern   with   the         ever is selected when PCRE is built can be overridden when the  library
654         pcre_exec()  function.  By controlling the maximum number of times this         functions are called.
        function may be called during a single matching operation, a limit  can  
        be  placed  on  the resources used by a single call to pcre_exec(). The  
        limit can be changed at run time, as described in the pcreapi  documen-  
        tation.  The default is 10 million, but this can be changed by adding a  
        setting such as  
655    
          --with-match-limit=500000  
656    
657         to  the  configure  command.  This  setting  has  no  effect   on   the  POSIX MALLOC USAGE
658         pcre_dfa_exec() matching function.  
659           When  the  8-bit library is called through the POSIX interface (see the
660           pcreposix documentation), additional working storage  is  required  for
661           holding  the  pointers  to  capturing substrings, because PCRE requires
662           three integers per substring, whereas the POSIX interface provides only
663           two.  If  the number of expected substrings is small, the wrapper func-
664           tion uses space on the stack, because this is faster  than  using  mal-
665           loc()  for each call. The default threshold above which the stack is no
666           longer used is 10; it can be changed by adding a setting such as
667    
668             --with-posix-malloc-threshold=20
669    
670           to the configure command.
671    
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.
        If you build PCRE with an increased link size, test 2 (and  test  5  if  
        you  are using UTF-8) will fail. Part of the output of these tests is a  
        representation of the compiled pattern, and this changes with the  link  
        size.  
690    
691    
692  AVOIDING EXCESSIVE STACK USAGE  AVOIDING EXCESSIVE STACK USAGE
693    
694         When matching with the pcre_exec() function, PCRE implements backtrack-         When matching with the pcre_exec() function, PCRE implements backtrack-
695         ing by making recursive calls to an internal function  called  match().         ing  by  making recursive calls to an internal function called match().
696         In  environments  where  the size of the stack is limited, this can se-         In environments where the size of the stack is limited,  this  can  se-
697         verely limit PCRE's operation. (The Unix environment does  not  usually         verely  limit  PCRE's operation. (The Unix environment does not usually
698         suffer  from  this  problem.)  An alternative approach that uses memory         suffer from this problem, but it may sometimes be necessary to increase
699         from the heap to remember data, instead  of  using  recursive  function         the  maximum  stack size.  There is a discussion in the pcrestack docu-
700         calls,  has been implemented to work round this problem. If you want to         mentation.) An alternative approach to recursion that uses memory  from
701         build a version of PCRE that works this way, add         the  heap  to remember data, instead of using recursive function calls,
702           has been implemented to work round the problem of limited  stack  size.
703           If you want to build a version of PCRE that works this way, add
704    
705           --disable-stack-for-recursion           --disable-stack-for-recursion
706    
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. Separate functions are provided because  the  usage  is         ment  functions. By default these point to malloc() and free(), but you
710         very  predictable:  the  block sizes requested are always the same, and         can replace the pointers so that your own functions are used instead.
711         the blocks are always freed in reverse order. A calling  program  might  
712         be  able  to implement optimized functions that perform better than the         Separate functions are  provided  rather  than  using  pcre_malloc  and
713         standard malloc() and  free()  functions.  PCRE  runs  noticeably  more         pcre_free  because  the  usage  is  very  predictable:  the block sizes
714         slowly when built in this way. This option affects only the pcre_exec()         requested are always the same, and  the  blocks  are  always  freed  in
715         function; it is not relevant for the the pcre_dfa_exec() function.         reverse  order.  A calling program might be able to implement optimized
716           functions that perform better  than  malloc()  and  free().  PCRE  runs
717           noticeably more slowly when built in this way. This option affects only
718           the pcre_exec() function; it is not relevant for pcre_dfa_exec().
719    
720    
721    LIMITING PCRE RESOURCE USAGE
722    
723           Internally, PCRE has a function called match(), which it calls  repeat-
724           edly   (sometimes   recursively)  when  matching  a  pattern  with  the
725           pcre_exec() function. By controlling the maximum number of  times  this
726           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
728           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
730           setting such as
731    
732             --with-match-limit=500000
733    
734           to   the   configure  command.  This  setting  has  no  effect  on  the
735           pcre_dfa_exec() matching function.
736    
737           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
739           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;
741           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
743           by adding, for example,
744    
745             --with-match-limit-recursion=10000
746    
747           to the configure command. This value can  also  be  overridden  at  run
748           time.
749    
750    
751    CREATING CHARACTER TABLES AT BUILD TIME
752    
753           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
755           distributed  in  the  file pcre_chartables.c.dist. These tables are for
756           ASCII codes only. If you add
757    
758             --enable-rebuild-chartables
759    
760           to the configure command, the distributed tables are  no  longer  used.
761           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
763           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
765           you  need  to  create alternative tables when cross compiling, you will
766           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         PCRE can, however, be compiled to  run  in  an  EBCDIC  environment  by         This is the case for most computer operating systems.  PCRE  can,  how-
774         adding         ever, be compiled to run in an EBCDIC environment by adding
775    
776           --enable-ebcdic           --enable-ebcdic
777    
778         to the configure command.         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
780           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  Last updated: 15 August 2005           --enable-pcregrep-libz
791  Copyright (c) 1997-2005 University of Cambridge.           --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
846    
847           pcreapi(3), pcre16, pcre_config(3).
848    
849    
850    AUTHOR
851    
852           Philip Hazel
853           University Computing Service
854           Cambridge CB2 3QH, England.
855    
856    
857    REVISION
858    
859           Last updated: 07 January 2012
860           Copyright (c) 1997-2012 University of Cambridge.
861  ------------------------------------------------------------------------------  ------------------------------------------------------------------------------
862    
863    
# Line 411  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 431  PCRE MATCHING ALGORITHMS Line 895  PCRE MATCHING ALGORITHMS
895           <something> <something else> <something further>           <something> <something else> <something further>
896    
897         there are three possible answers. The standard algorithm finds only one         there are three possible answers. The standard algorithm finds only one
898         of them, whereas the DFA algorithm finds all three.         of them, whereas the alternative algorithm finds all three.
899    
900    
901  REGULAR EXPRESSIONS AS TREES  REGULAR EXPRESSIONS AS TREES
# Line 440  REGULAR EXPRESSIONS AS TREES Line 904  REGULAR EXPRESSIONS AS TREES
904         resented  as  a  tree structure. An unlimited repetition in the pattern         resented  as  a  tree structure. An unlimited repetition in the pattern
905         makes the tree of infinite size, but it is still a tree.  Matching  the         makes the tree of infinite size, but it is still a tree.  Matching  the
906         pattern  to a given subject string (from a given starting point) can be         pattern  to a given subject string (from a given starting point) can be
907         thought of as a search of the tree.  There are  two  standard  ways  to         thought of as a search of the tree.  There are two  ways  to  search  a
908         search  a  tree: depth-first and breadth-first, and these correspond to         tree:  depth-first  and  breadth-first, and these correspond to the two
909         the two matching algorithms provided by PCRE.         matching algorithms provided by PCRE.
910    
911    
912  THE STANDARD MATCHING ALGORITHM  THE STANDARD MATCHING ALGORITHM
913    
914         In the terminology of Jeffrey Friedl's book Mastering  Regular  Expres-         In the terminology of Jeffrey Friedl's book "Mastering Regular  Expres-
915         sions,  the  standard  algorithm  is  an "NFA algorithm". It conducts a         sions",  the  standard  algorithm  is an "NFA algorithm". It conducts a
916         depth-first search of the pattern tree. That is, it  proceeds  along  a         depth-first search of the pattern tree. That is, it  proceeds  along  a
917         single path through the tree, checking that the subject matches what is         single path through the tree, checking that the subject matches what is
918         required. When there is a mismatch, the algorithm  tries  any  alterna-         required. When there is a mismatch, the algorithm  tries  any  alterna-
# Line 472  THE STANDARD MATCHING ALGORITHM Line 936  THE STANDARD MATCHING ALGORITHM
936         This provides support for capturing parentheses and back references.         This provides support for capturing parentheses and back references.
937    
938    
939  THE DFA MATCHING ALGORITHM  THE ALTERNATIVE MATCHING ALGORITHM
940    
941         DFA stands for "deterministic finite automaton", but you do not need to         This algorithm conducts a breadth-first search of  the  tree.  Starting
942         understand the origins of that name. This algorithm conducts a breadth-         from  the  first  matching  point  in the subject, it scans the subject
943         first search of the tree. Starting from the first matching point in the         string from left to right, once, character by character, and as it does
944         subject,  it scans the subject string from left to right, once, charac-         this,  it remembers all the paths through the tree that represent valid
945         ter by character, and as it does  this,  it  remembers  all  the  paths         matches. In Friedl's terminology, this is a kind  of  "DFA  algorithm",
946         through the tree that represent valid matches.         though  it is not implemented as a traditional finite state machine (it
947           keeps multiple states active simultaneously).
948         The  scan  continues until either the end of the subject is reached, or  
949         there are no more unterminated paths. At this point,  terminated  paths         Although the general principle of this matching algorithm  is  that  it
950         represent  the different matching possibilities (if there are none, the         scans  the subject string only once, without backtracking, there is one
951         match has failed).  Thus, if there is more  than  one  possible  match,         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
956           there  are  no more unterminated paths. At this point, terminated paths
957           represent the different matching possibilities (if there are none,  the
958           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 DFA 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.         ungreedy quantifiers are treated in exactly the same way. However, pos-
980           sessive  quantifiers can make a difference when what follows could also
981           match what is quantified, for example in a pattern like this:
982    
983             ^a++\w!
984    
985           This pattern matches "aaab!" but not "aaa!", which would be matched  by
986           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,
988           and  the  longest match is then "locked in" for the rest of the overall
989           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
# Line 516  THE DFA MATCHING ALGORITHM Line 998  THE DFA MATCHING ALGORITHM
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 are not supported.         ence as the condition or test for a specific group  recursion  are  not
1002           supported.
1003    
1004         5. Callouts are supported, but the value of the  capture_top  field  is         5.  Because  many  paths  through the tree may be active, the \K escape
1005           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
1007           error if encountered.
1008    
1009           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         6.  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 DFA algo-         matches a single data unit, even in UTF-8 or UTF-16 modes, is not  sup-
1014         rithm moves through the subject string one character at a time, for all         ported  in these modes, because the alternative algorithm moves through
1015           the subject string one character (not data unit) at  a  time,  for  all
1016         active paths through the tree.         active paths through the tree.
1017    
1018           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 DFA ALGORITHM  ADVANTAGES OF THE ALTERNATIVE ALGORITHM
1024    
1025         Using the DFA matching algorithm provides the following advantages:         Using  the alternative matching algorithm provides the following advan-
1026           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 DFA algorithm. For non-         sible  to  pass  very  long subject strings to the matching function in
1036         anchored patterns, the starting position of a partial match  is  avail-         several pieces, checking for partial matching each time. Although it is
1037         able.         possible  to  do multi-segment matching using the standard algorithm by
1038           retaining partially matched substrings, it  is  more  complicated.  The
1039           pcrepartial  documentation  gives  details of partial matching and dis-
1040           cusses multi-segment matching.
1041    
        3.  Because  the  DFA algorithm scans the subject string just once, and  
        never needs to backtrack, it is possible  to  pass  very  long  subject  
        strings  to  the matching function in several pieces, checking for par-  
        tial matching each time.  
1042    
1043    DISADVANTAGES OF THE ALTERNATIVE ALGORITHM
1044    
1045  DISADVANTAGES OF THE DFA ALGORITHM         The alternative algorithm suffers from a number of disadvantages:
   
        The DFA 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
# Line 558  DISADVANTAGES OF THE DFA ALGORITHM Line 1050  DISADVANTAGES OF THE DFA ALGORITHM
1050    
1051         2. Capturing parentheses and back references are not supported.         2. Capturing parentheses and back references are not supported.
1052    
1053         3. The "atomic group" feature of PCRE regular expressions is supported,         3. Although atomic groups are supported, their use does not provide the
1054         but  does not provide the advantage that it does for the standard algo-         performance advantage that it does for the standard algorithm.
1055         rithm.  
1056    
1057    AUTHOR
1058    
1059           Philip Hazel
1060           University Computing Service
1061           Cambridge CB2 3QH, England.
1062    
1063    
1064    REVISION
1065    
1066  Last updated: 28 February 2005         Last updated: 08 January 2012
1067  Copyright (c) 1997-2005 University of Cambridge.         Copyright (c) 1997-2012 University of Cambridge.
1068  ------------------------------------------------------------------------------  ------------------------------------------------------------------------------
1069    
1070    
# Line 573  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 590  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 599  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 616  PCRE NATIVE API Line 1122  PCRE NATIVE API
1122         int pcre_get_stringnumber(const pcre *code,         int pcre_get_stringnumber(const pcre *code,
1123              const char *name);              const char *name);
1124    
1125           int pcre_get_stringtable_entries(const pcre *code,
1126                const char *name, char **first, char **last);
1127    
1128         int pcre_get_substring(const char *subject, int *ovector,         int pcre_get_substring(const char *subject, int *ovector,
1129              int stringcount, int stringnumber,              int stringcount, int stringnumber,
1130              const char **stringptr);              const char **stringptr);
# Line 627  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 651  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         is also a set of 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. This allows it to find all possible matches (at a given  point  in         ing. The alternative algorithm finds all possible matches (at  a  given
1244         the  subject),  not  just  one. However, this algorithm does not return         point  in  the  subject), and scans the subject just once (unless there
1245         captured substrings. A description of the two matching  algorithms  and         are lookbehind assertions). However, this  algorithm  does  not  return
1246         their  advantages  and disadvantages is given in the pcrematching docu-         captured  substrings.  A description of the two matching algorithms and
1247           their advantages and disadvantages is given in the  pcrematching  docu-
1248         mentation.         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 692  PCRE API OVERVIEW Line 1257  PCRE API OVERVIEW
1257           pcre_get_named_substring()           pcre_get_named_substring()
1258           pcre_get_substring_list()           pcre_get_substring_list()
1259           pcre_get_stringnumber()           pcre_get_stringnumber()
1260             pcre_get_stringtable_entries()
1261    
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. This is a non-standard way of building PCRE, for use in envi-         function.  See  the  pcrebuild  documentation  for details of how to do
1291         ronments that have limited stacks. Because of the greater use of memory         this. It is a non-standard way of building PCRE, for  use  in  environ-
1292         management, it runs more slowly.  Separate functions  are  provided  so         ments  that  have  limited stacks. Because of the greater use of memory
1293           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-
1298           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
1307    
1308           PCRE supports five different conventions for indicating line breaks  in
1309           strings:  a  single  CR (carriage return) character, a single LF (line-
1310           feed) character, the two-character sequence CRLF, any of the three pre-
1311           ceding,  or any Unicode newline sequence. The Unicode newline sequences
1312           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
1314           separator, U+2028), and PS (paragraph separator, U+2029).
1315    
1316           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
1318           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
1320           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-
1328           acter or pair of characters that indicate a line break". The choice  of
1329           newline  convention  affects  the  handling of the dot, circumflex, and
1330           dollar metacharacters, the handling of #-comments in /x mode, and, when
1331           CRLF  is a recognized line ending sequence, the match position advance-
1332           ment for a non-anchored pattern. There is more detail about this in the
1333           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
1341    
1342         The  PCRE  functions  can be used in multi-threading applications, with         The  PCRE  functions  can be used in multi-threading applications, with
# Line 743  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.         pcreprecompile  documentation,  which  includes  a  description  of the
1362           pcre_pattern_to_host_byte_order() function. However, compiling a  regu-
1363           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 767  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_NEWLINE           PCRE_CONFIG_JIT
1404    
1405         The output is an integer that is set to the value of the code  that  is         The output is an integer that is set to one if support for just-in-time
1406         used  for the newline character. It is either linefeed (10) or carriage         compiling is available; otherwise it is set to zero.
1407         return (13), and should normally be the  standard  character  for  your  
1408         operating system.           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
1417    
1418           The  output  is  an integer whose value specifies the default character
1419           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,
1421           and -1 for ANY.  Though they are derived from ASCII,  the  same  values
1422           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    
1446         The output is an integer that contains the threshold  above  which  the         The  output  is  an integer that contains the threshold above which the
1447         POSIX  interface  uses malloc() for output vectors. Further details are         POSIX interface uses malloc() for output vectors. Further  details  are
1448         given in the pcreposix documentation.         given in the pcreposix documentation.
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
1457    
1458           The output is a long integer that gives the default limit for the depth
1459           of  recursion  when  calling  the  internal  matching  function  in   a
1460           pcre_exec()  execution.  Further  details  are  given  with pcre_exec()
1461           below.
1462    
1463           PCRE_CONFIG_STACKRECURSE           PCRE_CONFIG_STACKRECURSE
1464    
# Line 833  COMPILING A PATTERN Line 1485  COMPILING A PATTERN
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  when  it  is  no  longer         It is up to the caller to free the memory (via pcre_free) when it is no
1498         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 independent bits that affect the compila-         The options argument contains various bit settings that affect the com-
1506         tion.  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 option can be set at the time of matching as well as         specifies their settings at the start of compilation and execution. The
1513           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.         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.  The  offset from the start of the pattern to the character where         sage. This is a static string that is part of the library. You must not
1521         the error was discovered is  placed  in  the  variable  pointed  to  by         try to free it. Normally, the offset from the start of the  pattern  to
1522         erroffset,  which  must  not  be  NULL. If it is, an immediate error is         the  byte  that  was  being  processed when the error was discovered is
1523         given.         placed in the variable pointed to by erroffset, which must not be  NULL
1524           (if  it is, an immediate error is given). However, for an invalid UTF-8
1525         If pcre_compile2() is used instead of pcre_compile(),  and  the  error-         string, the offset is that of the first byte of the failing character.
1526         codeptr  argument is not NULL, a non-zero error code number is returned  
1527         via this argument in the event of an error. This is in addition to  the         Some errors are not detected until the whole pattern has been  scanned;
1528           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 892  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 the final character if it is a newline  (but         matches  immediately before a newline at the end of the string (but not
1602         not  before  any  other  newlines).  The  PCRE_DOLLAR_ENDONLY option is         before any other newlines). The PCRE_DOLLAR_ENDONLY option  is  ignored
1603         ignored if PCRE_MULTILINE is set. There is no equivalent to this option         if  PCRE_MULTILINE  is  set.   There is no equivalent to this option in
1604         in 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 newlines. Without it,  newlines  are  excluded.  This         acter of any value, including one that indicates a newline. However, it
1610         option  is equivalent to Perl's /s option, and it can be changed within         only ever matches one character, even if newlines are  coded  as  CRLF.
1611         a pattern by a (?s) option setting.  A  negative  class  such  as  [^a]         Without  this option, a dot does not match when the current position is
1612         always  matches a newline character, independent of the setting of this         at a newline. This option is equivalent to Perl's /s option, and it can
1613         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
1618    
1619           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
1621           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
1623           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 character, inclusive, are also  ignored.  This  is  equivalent  to         line,  inclusive,  are  also  ignored.  This is equivalent to Perl's /x
1632         Perl's  /x  option,  and  it  can be changed within a pattern by a (?x)         option, and it can be changed within a pattern by a  (?x)  option  set-
1633         option setting.         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 964  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. There are at present no  other  features  controlled  by  this         literal. (Perl can, however, be persuaded to give an error for this, by
1657         option. It can also be set by a (?X) option setting within a pattern.         running  it with the -w option.) There are at present no other features
1658           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 character in the subject string,  though         before or at the first  newline  in  the  subject  string,  though  the
1665         the 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
1701         line of characters (even if it actually contains newlines). The  "start         line  of characters (even if it actually contains newlines). The "start
1702         of  line"  metacharacter  (^)  matches only at the start of the string,         of line" metacharacter (^) matches only at the  start  of  the  string,
1703         while the "end of line" metacharacter ($) matches only at  the  end  of         while  the  "end  of line" metacharacter ($) matches only at the end of
1704         the string, or before a terminating newline (unless PCRE_DOLLAR_ENDONLY         the string, or before a terminating newline (unless PCRE_DOLLAR_ENDONLY
1705         is set). This is the same as Perl.         is set). This is the same as Perl.
1706    
1707         When PCRE_MULTILINE it is set, the "start of line" and  "end  of  line"         When  PCRE_MULTILINE  it  is set, the "start of line" and "end of line"
1708         constructs  match  immediately following or immediately before any new-         constructs match immediately following or immediately  before  internal
1709         line in the subject string, respectively, as well as at the very  start         newlines  in  the  subject string, respectively, as well as at the very
1710         and  end. This is equivalent to Perl's /m option, and it can be changed         start and end. This is equivalent to Perl's /m option, and  it  can  be
1711         within a pattern by a (?m) option setting. If there are no "\n" charac-         changed within a pattern by a (?m) option setting. If there are no new-
1712         ters  in  a  subject  string, or no occurrences of ^ or $ in a pattern,         lines in a subject string, or no occurrences of ^ or $  in  a  pattern,
1713         setting PCRE_MULTILINE has no effect.         setting PCRE_MULTILINE has no effect.
1714    
1715             PCRE_NEWLINE_CR
1716             PCRE_NEWLINE_LF
1717             PCRE_NEWLINE_CRLF
1718             PCRE_NEWLINE_ANYCRLF
1719             PCRE_NEWLINE_ANY
1720    
1721           These  options  override the default newline definition that was chosen
1722           when PCRE was built. Setting the first or the second specifies  that  a
1723           newline  is  indicated  by a single character (CR or LF, respectively).
1724           Setting PCRE_NEWLINE_CRLF specifies that a newline is indicated by  the
1725           two-character  CRLF  sequence.  Setting  PCRE_NEWLINE_ANYCRLF specifies
1726           that any of the three preceding sequences should be recognized. Setting
1727           PCRE_NEWLINE_ANY  specifies that any Unicode newline sequence should be
1728           recognized. The Unicode newline sequences are the three just mentioned,
1729           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
1731           (paragraph  separator, U+2029). For the 8-bit library, the last two are
1732           recognized only in UTF-8 mode.
1733    
1734           The newline setting in the  options  word  uses  three  bits  that  are
1735           treated as a number, giving eight possibilities. Currently only six are
1736           used (default plus the five values above). This means that if  you  set
1737           more  than one newline option, the combination may or may not be sensi-
1738           ble. For example, PCRE_NEWLINE_CR with PCRE_NEWLINE_LF is equivalent to
1739           PCRE_NEWLINE_CRLF,  but other combinations may yield unused numbers and
1740           cause an error.
1741    
1742           The only time that a line break in a pattern  is  specially  recognized
1743           when  compiling  is when PCRE_EXTENDED is set. CR and LF are whitespace
1744           characters, and so are ignored in this mode. Also, an unescaped #  out-
1745           side  a  character class indicates a comment that lasts until after the
1746           next line break sequence. In other circumstances, line break  sequences
1747           in patterns are treated as literal data.
1748    
1749           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.
1751    
1752           PCRE_NO_AUTO_CAPTURE           PCRE_NO_AUTO_CAPTURE
1753    
1754         If this option is set, it disables the use of numbered capturing paren-         If this option is set, it disables the use of numbered capturing paren-
# Line 998  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. If an invalid UTF-8 sequence of bytes is found,         automatically  checked.  There  is  a  discussion about the validity of
1798         pcre_compile() returns an error. If you already know that your  pattern         UTF-8 strings in the pcreunicode page. If an invalid UTF-8 sequence  is
1799         is  valid, and you want to skip this check for performance reasons, you         found,  pcre_compile()  returns an error. If you already know that your
1800         can set the PCRE_NO_UTF8_CHECK option. When it is set,  the  effect  of         pattern is valid, and you want to skip this check for performance  rea-
1801         passing an invalid UTF-8 string as a pattern is undefined. It may cause         sons,  you  can set the PCRE_NO_UTF8_CHECK option.  When it is set, the
1802         your program to crash.  Note that this option can  also  be  passed  to         effect of passing an invalid UTF-8 string as a pattern is undefined. It
1803         pcre_exec()  and pcre_dfa_exec(), to suppress the UTF-8 validity check-         may  cause  your  program  to  crash. Note that this option can also be
1804         ing of subject strings.         passed to pcre_exec() and pcre_dfa_exec(),  to  suppress  the  validity
1805           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.         both  compiling  functions.  Note  that error messages are always 8-bit
1813           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 1043  COMPILATION ERROR CODES Line 1824  COMPILATION ERROR CODES
1824            7  invalid escape sequence in character class            7  invalid escape sequence in character class
1825            8  range out of order in character class            8  range out of order in character class
1826            9  nothing to repeat            9  nothing to repeat
1827           10  operand of unlimited repeat could match the empty string           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
1833           16  erroffset passed as NULL           16  erroffset passed as NULL
1834           17  unknown option bit(s) set           17  unknown option bit(s) set
1835           18  missing ) after comment           18  missing ) after comment
1836           19  parentheses nested too deeply           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
1841           24  unrecognized character after (?<           24  unrecognized character after (?<
1842           25  lookbehind assertion is not fixed length           25  lookbehind assertion is not fixed length
1843           26  malformed number after (?(           26  malformed number or name after (?(
1844           27  conditional group contains more than two branches           27  conditional group contains more than two branches
1845           28  assertion expected after (?(           28  assertion expected after (?(
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  spare error           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 after (?P           42  syntax error in subpattern name (missing terminator)
1860           43  two named groups 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)
1866             49  too many named subpatterns (maximum 10000)
1867             50  [this code is not in use]
1868             51  octal value is greater than \377 in 8-bit non-UTF-8 mode
1869             52  internal error: overran compiling workspace
1870             53  internal error: previously-checked referenced subpattern
1871                   not found
1872             54  DEFINE group contains more than one branch
1873             55  repeating a DEFINE group is not allowed
1874             56  inconsistent NEWLINE options
1875             57  \g is not followed by a braced, angle-bracketed, or quoted
1876                   name/number or by a plain number
1877             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 1088  STUDYING A PATTERN Line 1903  STUDYING A PATTERN
1903         pcre_extra *pcre_study(const pcre *code, int options         pcre_extra *pcre_study(const pcre *code, int options
1904              const char **errptr);              const char **errptr);
1905    
1906         If a compiled pattern is going to be used several times,  it  is  worth         If  a  compiled  pattern is going to be used several times, it is worth
1907         spending more time analyzing it in order to speed up the time taken for         spending more time analyzing it in order to speed up the time taken for
1908         matching. The function pcre_study() takes a pointer to a compiled  pat-         matching.  The function pcre_study() takes a pointer to a compiled pat-
1909         tern as its first argument. If studying the pattern produces additional         tern as its first argument. If studying the pattern produces additional
1910         information that will help speed up matching,  pcre_study()  returns  a         information  that  will  help speed up matching, pcre_study() returns a
1911         pointer  to a pcre_extra block, in which the study_data field points to         pointer to a pcre_extra block, in which the study_data field points  to
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
1941         points  to  is set to NULL. Otherwise it points to a textual error mes-         points to is set to NULL. Otherwise it is set to  point  to  a  textual
1942         sage. You should therefore test the error pointer for NULL after  call-         error message. This is a static string that is part of the library. You
1943         ing pcre_study(), to be sure that it has run successfully.         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.
1945    
1946           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 call to pcre_study():         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
1996    
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.         PCRE is built with Unicode character property  support.  Alternatively,
2003           the  PCRE_UCP  option  can  be  set at compile time; this causes \w and
2004         An internal set of tables is created in the default C locale when  PCRE         friends to use Unicode property support instead of built-in tables. The
2005         is  built.  This  is  used when the final argument of pcre_compile() is         use of locales with Unicode is discouraged. If you are handling charac-
2006         NULL, and is sufficient for many applications. An  alternative  set  of         ters with codes greater than 128, you should either use UTF-8 and  Uni-
2007         tables  can,  however, be supplied. These may be created in a different         code, or use locales, but not try to mix the two.
2008         locale from the default. As more and more applications change to  using  
2009         Unicode, the need for this locale support is expected to die away.         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
2011           applications.  Normally, the internal tables recognize only ASCII char-
2012           acters. However, when PCRE is built, it is possible to cause the inter-
2013           nal tables to be rebuilt in the default "C" locale of the local system,
2014           which may cause them to be different.
2015    
2016           The internal tables can always be overridden by tables supplied by  the
2017           application that calls PCRE. These may be created in a different locale
2018           from the default. As more and more applications change  to  using  Uni-
2019           code, the need for this locale support is expected to die away.
2020    
2021         External  tables  are  built by calling the pcre_maketables() function,         External  tables  are  built by calling the pcre_maketables() function,
2022         which has no arguments, in the relevant locale. The result can then  be         which has no arguments, in the relevant locale. The result can then  be
# Line 1155  LOCALE SUPPORT Line 2029  LOCALE SUPPORT
2029           tables = pcre_maketables();           tables = pcre_maketables();
2030           re = pcre_compile(..., tables);           re = pcre_compile(..., tables);
2031    
2032         When pcre_maketables() runs, the tables are built  in  memory  that  is         The locale name "fr_FR" is used on Linux and other  Unix-like  systems;
2033         obtained  via  pcre_malloc. It is the caller's responsibility to ensure         if you are using Windows, the name for the French locale is "french".
2034         that the memory containing the tables remains available for as long  as  
2035           When  pcre_maketables()  runs,  the  tables are built in memory that is
2036           obtained via pcre_malloc. It is the caller's responsibility  to  ensure
2037           that  the memory containing the tables remains available for as long as
2038         it is needed.         it is needed.
2039    
2040         The pointer that is passed to pcre_compile() is saved with the compiled         The pointer that is passed to pcre_compile() is saved with the compiled
2041         pattern, and the same tables are used via this pointer by  pcre_study()         pattern,  and the same tables are used via this pointer by pcre_study()
2042         and normally also by pcre_exec(). Thus, by default, for any single pat-         and normally also by pcre_exec(). Thus, by default, for any single pat-
2043         tern, compilation, studying and matching all happen in the same locale,         tern, compilation, studying and matching all happen in the same locale,
2044         but different patterns can be compiled in different locales.         but different patterns can be compiled in different locales.
2045    
2046         It  is  possible to pass a table pointer or NULL (indicating the use of         It is possible to pass a table pointer or NULL (indicating the  use  of
2047         the internal tables) to pcre_exec(). Although  not  intended  for  this         the  internal  tables)  to  pcre_exec(). Although not intended for this
2048         purpose,  this facility could be used to match a pattern in a different         purpose, this facility could be used to match a pattern in a  different
2049         locale from the one in which it was compiled. Passing table pointers at         locale from the one in which it was compiled. Passing table pointers at
2050         run time is discussed below in the section on matching a pattern.         run time is discussed below in the section on matching a pattern.
2051    
# Line 1178  INFORMATION ABOUT A PATTERN Line 2055  INFORMATION ABOUT A PATTERN
2055         int pcre_fullinfo(const pcre *code, const pcre_extra *extra,         int pcre_fullinfo(const pcre *code, const pcre_extra *extra,
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
2064         the  pattern  was not studied. The third argument specifies which piece         the pattern was not studied. The third argument specifies  which  piece
2065         of information is required, and the fourth argument is a pointer  to  a         of  information  is required, and the fourth argument is a pointer to a
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         The "magic number" is placed at the start of each compiled  pattern  as           PCRE_ERROR_BADOPTION      the value of what was invalid
2075         an  simple check against passing an arbitrary memory pointer. Here is a  
2076         typical call of pcre_fullinfo(), to obtain the length of  the  compiled         The  "magic  number" is placed at the start of each compiled pattern as
2077         pattern:         an simple check against passing an arbitrary memory pointer. The  endi-
2078           anness error can occur if a compiled pattern is saved and reloaded on a
2079           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           unsigned long int 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    
# Line 1231  INFORMATION ABOUT A PATTERN Line 2111  INFORMATION ABOUT A PATTERN
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.   (This    option    used    to    be    called         a non-anchored pattern. (The name of this option refers  to  the  8-bit
2116         PCRE_INFO_FIRSTCHAR;  the  old  name  is still recognized for backwards         library,  where data units are bytes.) The fourth argument should point
2117         compatibility.)         to an int variable.
2118    
2119         If there is a fixed first byte, for example, from  a  pattern  such  as         If there is a fixed first value, for example, the  letter  "c"  from  a
2120         (cat|cow|coyote),  it  is  returned in the integer pointed to by where.         pattern  such  as (cat|cow|coyote), its value is returned. In the 8-bit
2121         Otherwise, if either         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 no fixed first value, and 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
2152    
2153           Return 1 if the (?J) or (?-J) option setting is used  in  the  pattern,
2154           otherwise  0. The fourth argument should point to an int variable. (?J)
2155           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.  A  convenience  function  called         ses, which still acquire numbers. Several convenience functions such as
2201         pcre_get_named_substring()  is  provided  for  extracting an individual         pcre_get_named_substring() are provided for  extracting  captured  sub-
2202         captured substring by name. It is also possible  to  extract  the  data         strings  by  name. It is also possible to extract the data directly, by
2203         directly,  by  first converting the name to a number in order to access         first converting the name to a number in order to  access  the  correct
2204         the correct pointers in the output vector (described  with  pcre_exec()         pointers in the output vector (described with pcre_exec() below). To do
2205         below).  To  do the conversion, you need to use the name-to-number map,         the conversion, you need  to  use  the  name-to-number  map,  which  is
2206         which is 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         For example, consider the following pattern  (assume  PCRE_EXTENDED  is         which  contains  the  parenthesis  number. The rest of the entry is the
2217           corresponding name, zero terminated.
2218    
2219           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):         set, so white space - including newlines - is ignored):
2232    
2233           (?P<date> (?P<year>(\d\d)?\d\d) -           (?<date> (?<year>(\d\d)?\d\d) -
2234           (?P<month>\d\d) - (?P<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 1306  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 each entry is likely to         name-to-number map, remember that the length of the entries  is  likely
2248         be different for each compiled pattern.         to be different for each compiled pattern.
2249    
2250             PCRE_INFO_OKPARTIAL
2251    
2252           Return  1  if  the  pattern  can  be  used  for  partial  matching with
2253           pcre_exec(), otherwise 0. The fourth argument should point  to  an  int
2254           variable.  From  release  8.00,  this  always  returns  1,  because the
2255           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 within the pattern itself.         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
2266           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,
2268           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:
# Line 1331  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
# Line 1395  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 2331  MATCHING A PATTERN: THE TRADITIONAL FUNC
2331              const char *subject, int length, int startoffset,              const char *subject, int length, int startoffset,
2332              int options, int *ovector, int ovecsize);              int options, int *ovector, int ovecsize);
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
2348         is possible to save compiled patterns and study data, and then use them         is possible to save compiled patterns and study data, and then use them
2349         later  in  different processes, possibly even on different hosts. For a         later in different processes, possibly even on different hosts.  For  a
2350         discussion about this, see the pcreprecompile documentation.         discussion about this, see the pcreprecompile documentation.
2351    
2352         Here is an example of a simple call to pcre_exec():         Here is an example of a simple call to pcre_exec():
# Line 1425  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 2365  MATCHING A PATTERN: THE TRADITIONAL FUNC
2365    
2366     Extra data for pcre_exec()     Extra data for pcre_exec()
2367    
2368         If the extra argument is not NULL, it must point to a  pcre_extra  data         If  the  extra argument is not NULL, it must point to a pcre_extra data
2369         block.  The pcre_study() function returns such a block (when it doesn't         block. The pcre_study() function returns such a block (when it  doesn't
2370         return NULL), but you can also create one for yourself, and pass  addi-         return  NULL), but you can also create one for yourself, and pass addi-
2371         tional  information in it. The fields in a pcre_extra block are as fol-         tional information in it. The pcre_extra block contains  the  following
2372         lows:         fields (not necessarily in this order):
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;
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
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 is imposed  on  the  number  of         repeatedly (sometimes recursively). The limit  set  by  match_limit  is
2411         times  this  function is called during a match, which has the effect of         imposed  on the number of times this function is called during a match,
2412         limiting the amount of recursion and backtracking that can take  place.         which has the effect of limiting the amount of  backtracking  that  can
2413         For patterns that are not anchored, the count starts from zero for each         take place. For patterns that are not anchored, the count restarts from
2414         position in the subject string.         zero for each position in the subject string.
2415    
2416         The default limit for the library can be set when PCRE  is  built;  the         When pcre_exec() is called with a pattern that was successfully studied
2417         default  default  is 10 million, which handles all but the most extreme         with  the  PCRE_STUDY_JIT_COMPILE  option, the way that the matching is
2418         cases. You can reduce  the  default  by  suppling  pcre_exec()  with  a         executed is entirely different. However, there is still the possibility
2419         pcre_extra  block  in  which match_limit is set to a smaller value, and         of  runaway  matching  that  goes  on  for a very long time, and so the
2420         PCRE_EXTRA_MATCH_LIMIT is set in the  flags  field.  If  the  limit  is         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
2424           default default is 10 million, which handles all but the  most  extreme
2425           cases.  You  can  override  the  default by suppling pcre_exec() with a
2426           pcre_extra    block    in    which    match_limit    is    set,     and
2427           PCRE_EXTRA_MATCH_LIMIT  is  set  in  the  flags  field. If the limit is
2428         exceeded, pcre_exec() returns PCRE_ERROR_MATCHLIMIT.         exceeded, pcre_exec() returns PCRE_ERROR_MATCHLIMIT.
2429    
2430         The  pcre_callout  field is used in conjunction with the "callout" fea-         The match_limit_recursion field is similar to match_limit, but  instead
2431         ture, which is described in the pcrecallout documentation.         of limiting the total number of times that match() is called, it limits
2432           the depth of recursion. The recursion depth is a  smaller  number  than
2433           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.
2435    
2436           Limiting the recursion depth limits the amount of  machine  stack  that
2437           can  be used, or, when PCRE has been compiled to use memory on the heap
2438           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           studied with PCRE_STUDY_JIT_COMPILE.
2441    
2442           The default value for match_limit_recursion can be  set  when  PCRE  is
2443           built;  the  default  default  is  the  same  value  as the default for
2444           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.
2448    
2449           The  callout_data  field is used in conjunction with the "callout" fea-
2450           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
# Line 1485  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 2460  MATCHING A PATTERN: THE TRADITIONAL FUNC
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_NOTBOL,         The only bits that may  be  set  are  PCRE_ANCHORED,  PCRE_NEWLINE_xxx,
2479         PCRE_NOTEOL, PCRE_NOTEMPTY, PCRE_NO_UTF8_CHECK and PCRE_PARTIAL.         PCRE_NOTBOL,    PCRE_NOTEOL,    PCRE_NOTEMPTY,   PCRE_NOTEMPTY_ATSTART,
2480           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
2506             PCRE_NEWLINE_LF
2507             PCRE_NEWLINE_CRLF
2508             PCRE_NEWLINE_ANYCRLF
2509             PCRE_NEWLINE_ANY
2510    
2511           These options override  the  newline  definition  that  was  chosen  or
2512           defaulted  when the pattern was compiled. For details, see the descrip-
2513           tion of pcre_compile()  above.  During  matching,  the  newline  choice
2514           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
2516           match failure for an unanchored pattern.
2517    
2518           When  PCRE_NEWLINE_CRLF,  PCRE_NEWLINE_ANYCRLF,  or PCRE_NEWLINE_ANY is
2519           set, and a match attempt for an unanchored pattern fails when the  cur-
2520           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    
2544         This option specifies that first character of the subject string is not         This option specifies that first character of the subject string is not
2545         the  beginning  of  a  line, so the circumflex metacharacter should not         the beginning of a line, so the  circumflex  metacharacter  should  not
2546         match before it. Setting this without PCRE_MULTILINE (at compile  time)         match  before it. Setting this without PCRE_MULTILINE (at compile time)
2547         causes  circumflex  never to match. This option affects only the behav-         causes circumflex never to match. This option affects only  the  behav-
2548         iour of the circumflex metacharacter. It does not affect \A.         iour of the circumflex metacharacter. It does not affect \A.
2549    
2550           PCRE_NOTEOL           PCRE_NOTEOL
2551    
2552         This option specifies that the end of the subject string is not the end         This option specifies that the end of the subject string is not the end
2553         of  a line, so the dollar metacharacter should not match it nor (except         of a line, so the dollar metacharacter should not match it nor  (except
2554         in multiline mode) a newline immediately before it. Setting this  with-         in  multiline mode) a newline immediately before it. Setting this with-
2555         out PCRE_MULTILINE (at compile time) causes dollar never to match. This         out PCRE_MULTILINE (at compile time) causes dollar never to match. This
2556         option affects only the behaviour of the dollar metacharacter. It  does         option  affects only the behaviour of the dollar metacharacter. It does
2557         not affect \Z or \z.         not affect \Z or \z.
2558    
2559           PCRE_NOTEMPTY           PCRE_NOTEMPTY
2560    
2561         An empty string is not considered to be a valid match if this option is         An empty string is not considered to be a valid match if this option is
2562         set. If there are alternatives in the pattern, they are tried.  If  all         set.  If  there are alternatives in the pattern, they are tried. If all
2563         the  alternatives  match  the empty string, the entire match fails. For         the alternatives match the empty string, the entire  match  fails.  For
2564         example, if the pattern         example, if the pattern
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. If an invalid UTF-8 sequence         points  to  the start of a UTF-8 character. There is a discussion about
2647         of bytes is found, pcre_exec() returns the error PCRE_ERROR_BADUTF8. If         the validity of UTF-8 strings in the pcreunicode page.  If  an  invalid
2648         startoffset  contains  an  invalid  value, PCRE_ERROR_BADUTF8_OFFSET is         sequence   of   bytes   is   found,   pcre_exec()   returns  the  error
2649         returned.         PCRE_ERROR_BADUTF8 or, if PCRE_PARTIAL_HARD is set and the problem is a
2650           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 1554  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 1598  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 the number of         The first pair of integers, ovector[0]  and  ovector[1],  identify  the
2771         pairs that have been set. If there are no  capturing  subpatterns,  the         portion  of  the subject string matched by the entire pattern. The next
2772         return  value  from  a  successful match is 1, indicating that just the         pair is used for the first capturing subpattern, and so on.  The  value
2773         first pair of offsets has been set.         returned by pcre_exec() is one more than the highest numbered pair that
2774           has been set.  For example, if two substrings have been  captured,  the
2775         Some convenience functions are provided  for  extracting  the  captured         returned  value is 3. If there are no capturing subpatterns, the return
2776         substrings  as  separate  strings. These are described in the following         value from a successful match is 1, indicating that just the first pair
2777         section.         of offsets has been set.
   
        It is possible for an capturing subpattern number  n+1  to  match  some  
        part  of  the  subject  when subpattern n has not been used at all. For  
        example, if the string "abc" is matched against the pattern (a|(z))(bc)  
        subpatterns  1 and 3 are matched, but 2 is not. When this happens, both  
        offset values corresponding to the unused subpattern are set to -1.  
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         Note that pcre_info() can be used to find out how many  capturing  sub-  
2792         patterns there are in a compiled pattern. The smallest size for ovector         There are some cases where zero is returned  (indicating  vector  over-
2793         that will allow for n captured substrings, in addition to  the  offsets         flow)  when  in fact the vector is exactly the right size for the final
2794         of the substring matched by the whole pattern, is (n+1)*3.         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_fullinfo() function can be used to find out how many capturing
2808           subpatterns there are in a compiled  pattern.  The  smallest  size  for
2809           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.
2811    
2812           It is possible for capturing subpattern number n+1 to match  some  part
2813           of the subject when subpattern n has not been used at all. For example,
2814           if the string "abc" is matched  against  the  pattern  (a|(z))(bc)  the
2815           return from the function is 4, and subpatterns 1 and 3 are matched, but
2816           2 is not. When this happens, both values in  the  offset  pairs  corre-
2817           sponding to unused subpatterns are set to -1.
2818    
2819           Offset  values  that correspond to unused subpatterns at the end of the
2820           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
2822           matched. The return from the function is 2, because  the  highest  used
2823           capturing  subpattern  number  is 1, and the offsets for for the second
2824           and third capturing subpatterns (assuming the vector is  large  enough,
2825           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
2834           substrings as separate strings. These are described below.
2835    
2836     Return values from pcre_exec()     Error return values from pcre_exec()
2837    
2838         If  pcre_exec()  fails, it returns a negative number. The following are         If pcre_exec() fails, it returns a negative number. The  following  are
2839         defined in the header file:         defined in the header file:
2840    
2841           PCRE_ERROR_NOMATCH        (-1)           PCRE_ERROR_NOMATCH        (-1)
# Line 1676  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 2844  MATCHING A PATTERN: THE TRADITIONAL FUNC
2844    
2845           PCRE_ERROR_NULL           (-2)           PCRE_ERROR_NULL           (-2)
2846    
2847         Either code or subject was passed as NULL,  or  ovector  was  NULL  and         Either  code  or  subject  was  passed as NULL, or ovector was NULL and
2848         ovecsize was not zero.         ovecsize was not zero.
2849    
2850           PCRE_ERROR_BADOPTION      (-3)           PCRE_ERROR_BADOPTION      (-3)
# Line 1685  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 2853  MATCHING A PATTERN: THE TRADITIONAL FUNC
2853    
2854           PCRE_ERROR_BADMAGIC       (-4)           PCRE_ERROR_BADMAGIC       (-4)
2855    
2856         PCRE  stores a 4-byte "magic number" at the start of the compiled code,         PCRE stores a 4-byte "magic number" at the start of the compiled  code,
2857         to catch the case when it is passed a junk pointer and to detect when a         to catch the case when it is passed a junk pointer and to detect when a
2858         pattern that was compiled in an environment of one endianness is run in         pattern that was compiled in an environment of one endianness is run in
2859         an environment with the other endianness. This is the error  that  PCRE         an  environment  with the other endianness. This is the error that PCRE
2860         gives when the magic number is not present.         gives when the magic number is not present.
2861    
2862           PCRE_ERROR_UNKNOWN_NODE   (-5)           PCRE_ERROR_UNKNOWN_OPCODE (-5)
2863    
2864         While running the pattern match, an unknown item was encountered in the         While running the pattern match, an unknown item was encountered in the
2865         compiled pattern. This error could be caused by a bug  in  PCRE  or  by         compiled  pattern.  This  error  could be caused by a bug in PCRE or by
2866         overwriting of the compiled pattern.         overwriting of the compiled pattern.
2867    
2868           PCRE_ERROR_NOMEMORY       (-6)           PCRE_ERROR_NOMEMORY       (-6)
2869    
2870         If  a  pattern contains back references, but the ovector that is passed         If a pattern contains back references, but the ovector that  is  passed
2871         to pcre_exec() is not big enough to remember the referenced substrings,         to pcre_exec() is not big enough to remember the referenced substrings,
2872         PCRE  gets  a  block of memory at the start of matching to use for this         PCRE gets a block of memory at the start of matching to  use  for  this
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(),
2883         and  pcre_get_substring_list()  functions  (see  below).  It  is  never         and  pcre_get_substring_list()  functions  (see  below).  It  is  never
2884         returned by pcre_exec().         returned by pcre_exec().
2885    
2886           PCRE_ERROR_MATCHLIMIT     (-8)           PCRE_ERROR_MATCHLIMIT     (-8)
2887    
2888         The  recursion  and backtracking limit, as specified by the match_limit         The backtracking limit, as specified by  the  match_limit  field  in  a
2889         field in a pcre_extra structure (or defaulted)  was  reached.  See  the         pcre_extra  structure  (or  defaulted) was reached. See the description
2890         description above.         above.
2891    
2892           PCRE_ERROR_CALLOUT        (-9)           PCRE_ERROR_CALLOUT        (-9)
2893    
2894         This error is never generated by pcre_exec() itself. It is provided for         This error is never generated by pcre_exec() itself. It is provided for
2895         use by callout functions that want to yield a distinctive  error  code.         use  by  callout functions that want to yield a distinctive error code.
2896         See the pcrecallout documentation for details.         See the pcrecallout documentation for details.
2897    
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         value  of startoffset did not point to the beginning of a UTF-8 charac-         found  to be valid (the PCRE_NO_UTF8_CHECK option was not set), but the
2914         ter.         value of startoffset did not point to the beginning of a UTF-8  charac-
2915           ter or the end of the subject.
2916    
2917           PCRE_ERROR_PARTIAL        (-12)           PCRE_ERROR_PARTIAL        (-12)
2918    
2919         The subject string did not match, but it did match partially.  See  the         The  subject  string did not match, but it did match partially. See the
2920         pcrepartial documentation for details of partial matching.         pcrepartial documentation for details of partial matching.
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    
# Line 1752  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 2933  MATCHING A PATTERN: THE TRADITIONAL FUNC
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)
2939    
2940           The internal recursion limit, as specified by the match_limit_recursion
2941           field  in  a  pcre_extra  structure (or defaulted) was reached. See the
2942           description above.
2943    
2944             PCRE_ERROR_BADNEWLINE     (-23)
2945    
2946           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().
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
# Line 1774  EXTRACTING CAPTURED SUBSTRINGS BY NUMBER Line 3085  EXTRACTING CAPTURED SUBSTRINGS BY NUMBER
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.  A  substring  that  contains  a  binary  zero is correctly         substrings.
3089         extracted and has a further zero added on the end, but  the  result  is  
3090         not, of course, a C string.         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
3092           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-
3094           string().  Unfortunately, the interface to pcre_get_substring_list() is
3095           not adequate for handling strings containing binary zeros, because  the
3096           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
# Line 1796  EXTRACTING CAPTURED SUBSTRINGS BY NUMBER Line 3113  EXTRACTING CAPTURED SUBSTRINGS BY NUMBER
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         the terminating zero, or one of these error codes:
3117    
3118           PCRE_ERROR_NOMEMORY       (-6)           PCRE_ERROR_NOMEMORY       (-6)
3119    
# Line 1812  EXTRACTING CAPTURED SUBSTRINGS BY NUMBER Line 3129  EXTRACTING CAPTURED SUBSTRINGS BY NUMBER
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         pointer.  The  yield  of  the function is zero if all went well, or the
3133           error code
3134