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1    -----------------------------------------------------------------------------
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    
 NAME  
      PCRE - Perl-compatible regular expressions  
10    
11    PCRE(3)                    Library Functions Manual                    PCRE(3)
12    
13    
14    
15    NAME
16           PCRE - Perl-compatible regular expressions
17    
18    INTRODUCTION
19    
20           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
22           just  a few differences. Some features that appeared in Python and PCRE
23           before they appeared in Perl are also available using the  Python  syn-
24           tax,  there  is  some  support for one or two .NET and Oniguruma syntax
25           items, and there is an option for requesting some  minor  changes  that
26           give better JavaScript compatibility.
27    
28           Starting with release 8.30, it is possible to compile two separate PCRE
29           libraries:  the  original,  which  supports  8-bit  character   strings
30           (including  UTF-8  strings),  and a second library that supports 16-bit
31           character strings (including UTF-16 strings). The build process  allows
32           either  one  or both to be built. The majority of the work to make this
33           possible was done by Zoltan Herczeg.
34    
35           Starting with release 8.32 it is possible to compile a  third  separate
36           PCRE  library  that supports 32-bit character strings (including UTF-32
37           strings). The build process allows any combination of the 8-,  16-  and
38           32-bit  libraries. The work to make this possible was done by Christian
39           Persch.
40    
41           The three libraries contain identical sets of  functions,  except  that
42           the  names  in  the 16-bit library start with pcre16_ instead of pcre_,
43           and the names in the 32-bit  library  start  with  pcre32_  instead  of
44           pcre_.  To avoid over-complication and reduce the documentation mainte-
45           nance load, most of the documentation describes the 8-bit library, with
46           the  differences  for  the  16-bit and 32-bit libraries described sepa-
47           rately in the pcre16 and  pcre32  pages.  References  to  functions  or
48           structures  of  the  form  pcre[16|32]_xxx  should  be  read as meaning
49           "pcre_xxx when using the  8-bit  library,  pcre16_xxx  when  using  the
50           16-bit library, or pcre32_xxx when using the 32-bit library".
51    
52           The  current implementation of PCRE corresponds approximately with Perl
53           5.12, including support for UTF-8/16/32  encoded  strings  and  Unicode
54           general  category  properties. However, UTF-8/16/32 and Unicode support
55           has to be explicitly enabled; it is not the default. The Unicode tables
56           correspond to Unicode release 6.2.0.
57    
58           In  addition to the Perl-compatible matching function, PCRE contains an
59           alternative function that matches the same compiled patterns in a  dif-
60           ferent way. In certain circumstances, the alternative function has some
61           advantages.  For a discussion of the two matching algorithms,  see  the
62           pcrematching page.
63    
64           PCRE  is  written  in C and released as a C library. A number of people
65           have written wrappers and interfaces of various kinds.  In  particular,
66           Google  Inc.   have  provided a comprehensive C++ wrapper for the 8-bit
67           library. This is now included as part of  the  PCRE  distribution.  The
68           pcrecpp  page  has  details of this interface. Other people's contribu-
69           tions can be found in the Contrib directory at the  primary  FTP  site,
70           which is:
71    
72           ftp://ftp.csx.cam.ac.uk/pub/software/programming/pcre
73    
74           Details  of  exactly which Perl regular expression features are and are
75           not supported by PCRE are given in separate documents. See the pcrepat-
76           tern  and pcrecompat pages. There is a syntax summary in the pcresyntax
77           page.
78    
79           Some features of PCRE can be included, excluded, or  changed  when  the
80           library  is  built.  The pcre_config() function makes it possible for a
81           client to discover which features are  available.  The  features  them-
82           selves  are described in the pcrebuild page. Documentation about build-
83           ing PCRE for various operating systems can be found in the  README  and
84           NON-AUTOTOOLS_BUILD files in the source distribution.
85    
86           The  libraries contains a number of undocumented internal functions and
87           data tables that are used by more than one  of  the  exported  external
88           functions,  but  which  are  not  intended for use by external callers.
89           Their names all begin with "_pcre_" or "_pcre16_" or "_pcre32_",  which
90           hopefully  will  not provoke any name clashes. In some environments, it
91           is possible to control which  external  symbols  are  exported  when  a
92           shared  library  is  built, and in these cases the undocumented symbols
93           are not exported.
94    
95    
96    SECURITY CONSIDERATIONS
97    
98           If you are using PCRE in a non-UTF application that  permits  users  to
99           supply  arbitrary  patterns  for  compilation, you should be aware of a
100           feature that allows users to turn on UTF support from within a pattern,
101           provided  that  PCRE  was built with UTF support. For example, an 8-bit
102           pattern that begins with "(*UTF8)" or "(*UTF)"  turns  on  UTF-8  mode,
103           which  interprets  patterns and subjects as strings of UTF-8 characters
104           instead of individual 8-bit characters.  This causes both  the  pattern
105           and any data against which it is matched to be checked for UTF-8 valid-
106           ity. If the data string is very long, such a  check  might  use  suffi-
107           ciently  many  resources  as  to cause your application to lose perfor-
108           mance.
109    
110           One  way  of  guarding  against  this  possibility  is   to   use   the
111           pcre_fullinfo()  function  to  check the compiled pattern's options for
112           UTF.  Alternatively, from release 8.33, you can set the  PCRE_NEVER_UTF
113           option  at compile time. This causes an compile time error if a pattern
114           contains a UTF-setting sequence.
115    
116           If your application is one that supports UTF, be  aware  that  validity
117           checking  can  take time. If the same data string is to be matched many
118           times, you can use the PCRE_NO_UTF[8|16|32]_CHECK option for the second
119           and subsequent matches to save redundant checks.
120    
121           Another  way  that  performance can be hit is by running a pattern that
122           has a very large search tree against a string that  will  never  match.
123           Nested  unlimited  repeats in a pattern are a common example. PCRE pro-
124           vides some protection against this: see the PCRE_EXTRA_MATCH_LIMIT fea-
125           ture in the pcreapi page.
126    
127    
128    USER DOCUMENTATION
129    
130           The  user  documentation  for PCRE comprises a number of different sec-
131           tions. In the "man" format, each of these is a separate "man page".  In
132           the  HTML  format, each is a separate page, linked from the index page.
133           In the plain text format, all the sections, except  the  pcredemo  sec-
134           tion, are concatenated, for ease of searching. The sections are as fol-
135           lows:
136    
137             pcre              this document
138             pcre-config       show PCRE installation configuration information
139             pcre16            details of the 16-bit library
140             pcre32            details of the 32-bit library
141             pcreapi           details of PCRE's native C API
142             pcrebuild         building PCRE
143             pcrecallout       details of the callout feature
144             pcrecompat        discussion of Perl compatibility
145             pcrecpp           details of the C++ wrapper for the 8-bit library
146             pcredemo          a demonstration C program that uses PCRE
147             pcregrep          description of the pcregrep command (8-bit only)
148             pcrejit           discussion of the just-in-time optimization support
149             pcrelimits        details of size and other limits
150             pcrematching      discussion of the two matching algorithms
151             pcrepartial       details of the partial matching facility
152             pcrepattern       syntax and semantics of supported
153                                 regular expressions
154             pcreperform       discussion of performance issues
155             pcreposix         the POSIX-compatible C API for the 8-bit library
156             pcreprecompile    details of saving and re-using precompiled patterns
157             pcresample        discussion of the pcredemo program
158             pcrestack         discussion of stack usage
159             pcresyntax        quick syntax reference
160             pcretest          description of the pcretest testing command
161             pcreunicode       discussion of Unicode and UTF-8/16/32 support
162    
163           In addition, in the "man" and HTML formats, there is a short  page  for
164           each C library function, listing its arguments and results.
165    
166    
167    AUTHOR
168    
169           Philip Hazel
170           University Computing Service
171           Cambridge CB2 3QH, England.
172    
173           Putting  an actual email address here seems to have been a spam magnet,
174           so I've taken it away. If you want to email me, use  my  two  initials,
175           followed by the two digits 10, at the domain cam.ac.uk.
176    
177    
178    REVISION
179    
180           Last updated: 13 May 2013
181           Copyright (c) 1997-2013 University of Cambridge.
182    ------------------------------------------------------------------------------
183    
184    
185    PCRE(3)                    Library Functions Manual                    PCRE(3)
186    
187    
188    
189    NAME
190           PCRE - Perl-compatible regular expressions
191    
192           #include <pcre.h>
193    
194    
195    PCRE 16-BIT API BASIC FUNCTIONS
196    
197           pcre16 *pcre16_compile(PCRE_SPTR16 pattern, int options,
198                const char **errptr, int *erroffset,
199                const unsigned char *tableptr);
200    
201           pcre16 *pcre16_compile2(PCRE_SPTR16 pattern, int options,
202                int *errorcodeptr,
203                const char **errptr, int *erroffset,
204                const unsigned char *tableptr);
205    
206           pcre16_extra *pcre16_study(const pcre16 *code, int options,
207                const char **errptr);
208    
209           void pcre16_free_study(pcre16_extra *extra);
210    
211           int pcre16_exec(const pcre16 *code, const pcre16_extra *extra,
212                PCRE_SPTR16 subject, int length, int startoffset,
213                int options, int *ovector, int ovecsize);
214    
215           int pcre16_dfa_exec(const pcre16 *code, const pcre16_extra *extra,
216                PCRE_SPTR16 subject, int length, int startoffset,
217                int options, int *ovector, int ovecsize,
218                int *workspace, int wscount);
219    
220    
221    PCRE 16-BIT API STRING EXTRACTION FUNCTIONS
222    
223           int pcre16_copy_named_substring(const pcre16 *code,
224                PCRE_SPTR16 subject, int *ovector,
225                int stringcount, PCRE_SPTR16 stringname,
226                PCRE_UCHAR16 *buffer, int buffersize);
227    
228           int pcre16_copy_substring(PCRE_SPTR16 subject, int *ovector,
229                int stringcount, int stringnumber, PCRE_UCHAR16 *buffer,
230                int buffersize);
231    
232           int pcre16_get_named_substring(const pcre16 *code,
233                PCRE_SPTR16 subject, int *ovector,
234                int stringcount, PCRE_SPTR16 stringname,
235                PCRE_SPTR16 *stringptr);
236    
237           int pcre16_get_stringnumber(const pcre16 *code,
238                PCRE_SPTR16 name);
239    
240           int pcre16_get_stringtable_entries(const pcre16 *code,
241                PCRE_SPTR16 name, PCRE_UCHAR16 **first, PCRE_UCHAR16 **last);
242    
243           int pcre16_get_substring(PCRE_SPTR16 subject, int *ovector,
244                int stringcount, int stringnumber,
245                PCRE_SPTR16 *stringptr);
246    
247           int pcre16_get_substring_list(PCRE_SPTR16 subject,
248                int *ovector, int stringcount, PCRE_SPTR16 **listptr);
249    
250           void pcre16_free_substring(PCRE_SPTR16 stringptr);
251    
252           void pcre16_free_substring_list(PCRE_SPTR16 *stringptr);
253    
254    
255    PCRE 16-BIT API AUXILIARY FUNCTIONS
256    
257           pcre16_jit_stack *pcre16_jit_stack_alloc(int startsize, int maxsize);
258    
259           void pcre16_jit_stack_free(pcre16_jit_stack *stack);
260    
261           void pcre16_assign_jit_stack(pcre16_extra *extra,
262                pcre16_jit_callback callback, void *data);
263    
264           const unsigned char *pcre16_maketables(void);
265    
266           int pcre16_fullinfo(const pcre16 *code, const pcre16_extra *extra,
267                int what, void *where);
268    
269           int pcre16_refcount(pcre16 *code, int adjust);
270    
271           int pcre16_config(int what, void *where);
272    
273           const char *pcre16_version(void);
274    
275           int pcre16_pattern_to_host_byte_order(pcre16 *code,
276                pcre16_extra *extra, const unsigned char *tables);
277    
278    
279    PCRE 16-BIT API INDIRECTED FUNCTIONS
280    
281           void *(*pcre16_malloc)(size_t);
282    
283           void (*pcre16_free)(void *);
284    
285           void *(*pcre16_stack_malloc)(size_t);
286    
287           void (*pcre16_stack_free)(void *);
288    
289           int (*pcre16_callout)(pcre16_callout_block *);
290    
291    
292    PCRE 16-BIT API 16-BIT-ONLY FUNCTION
293    
294           int pcre16_utf16_to_host_byte_order(PCRE_UCHAR16 *output,
295                PCRE_SPTR16 input, int length, int *byte_order,
296                int keep_boms);
297    
298    
299    THE PCRE 16-BIT LIBRARY
300    
301           Starting  with  release  8.30, it is possible to compile a PCRE library
302           that supports 16-bit character strings, including  UTF-16  strings,  as
303           well  as  or instead of the original 8-bit library. The majority of the
304           work to make  this  possible  was  done  by  Zoltan  Herczeg.  The  two
305           libraries contain identical sets of functions, used in exactly the same
306           way. Only the names of the functions and the data types of their  argu-
307           ments  and results are different. To avoid over-complication and reduce
308           the documentation maintenance load,  most  of  the  PCRE  documentation
309           describes  the  8-bit  library,  with only occasional references to the
310           16-bit library. This page describes what is different when you use  the
311           16-bit library.
312    
313           WARNING:  A  single  application can be linked with both libraries, but
314           you must take care when processing any particular pattern to use  func-
315           tions  from  just one library. For example, if you want to study a pat-
316           tern that was compiled with  pcre16_compile(),  you  must  do  so  with
317           pcre16_study(), not pcre_study(), and you must free the study data with
318           pcre16_free_study().
319    
320    
321    THE HEADER FILE
322    
323           There is only one header file, pcre.h. It contains prototypes  for  all
324           the functions in all libraries, as well as definitions of flags, struc-
325           tures, error codes, etc.
326    
327    
328    THE LIBRARY NAME
329    
330           In Unix-like systems, the 16-bit library is called libpcre16,  and  can
331           normally  be  accesss  by adding -lpcre16 to the command for linking an
332           application that uses PCRE.
333    
334    
335    STRING TYPES
336    
337           In the 8-bit library, strings are passed to PCRE library  functions  as
338           vectors  of  bytes  with  the  C  type "char *". In the 16-bit library,
339           strings are passed as vectors of unsigned 16-bit quantities. The  macro
340           PCRE_UCHAR16  specifies  an  appropriate  data type, and PCRE_SPTR16 is
341           defined as "const PCRE_UCHAR16 *". In very  many  environments,  "short
342           int" is a 16-bit data type. When PCRE is built, it defines PCRE_UCHAR16
343           as "unsigned short int", but checks that it really  is  a  16-bit  data
344           type.  If  it is not, the build fails with an error message telling the
345           maintainer to modify the definition appropriately.
346    
347    
348    STRUCTURE TYPES
349    
350           The types of the opaque structures that are used  for  compiled  16-bit
351           patterns  and  JIT stacks are pcre16 and pcre16_jit_stack respectively.
352           The  type  of  the  user-accessible  structure  that  is  returned   by
353           pcre16_study()  is  pcre16_extra, and the type of the structure that is
354           used for passing data to a callout  function  is  pcre16_callout_block.
355           These structures contain the same fields, with the same names, as their
356           8-bit counterparts. The only difference is that pointers  to  character
357           strings are 16-bit instead of 8-bit types.
358    
359    
360    16-BIT FUNCTIONS
361    
362           For  every function in the 8-bit library there is a corresponding func-
363           tion in the 16-bit library with a name that starts with pcre16_ instead
364           of  pcre_.  The  prototypes are listed above. In addition, there is one
365           extra function, pcre16_utf16_to_host_byte_order(). This  is  a  utility
366           function  that converts a UTF-16 character string to host byte order if
367           necessary. The other 16-bit  functions  expect  the  strings  they  are
368           passed to be in host byte order.
369    
370           The input and output arguments of pcre16_utf16_to_host_byte_order() may
371           point to the same address, that is, conversion in place  is  supported.
372           The output buffer must be at least as long as the input.
373    
374           The  length  argument  specifies the number of 16-bit data units in the
375           input string; a negative value specifies a zero-terminated string.
376    
377           If byte_order is NULL, it is assumed that the string starts off in host
378           byte  order. This may be changed by byte-order marks (BOMs) anywhere in
379           the string (commonly as the first character).
380    
381           If byte_order is not NULL, a non-zero value of the integer to which  it
382           points  means  that  the input starts off in host byte order, otherwise
383           the opposite order is assumed. Again, BOMs in  the  string  can  change
384           this. The final byte order is passed back at the end of processing.
385    
386           If  keep_boms  is  not  zero,  byte-order  mark characters (0xfeff) are
387           copied into the output string. Otherwise they are discarded.
388    
389           The result of the function is the number of 16-bit  units  placed  into
390           the  output  buffer,  including  the  zero terminator if the string was
391           zero-terminated.
392    
393    
394    SUBJECT STRING OFFSETS
395    
396           The lengths and starting offsets of subject strings must  be  specified
397           in  16-bit  data units, and the offsets within subject strings that are
398           returned by the matching functions are in also 16-bit units rather than
399           bytes.
400    
401    
402    NAMED SUBPATTERNS
403    
404           The  name-to-number translation table that is maintained for named sub-
405           patterns uses 16-bit characters.  The  pcre16_get_stringtable_entries()
406           function returns the length of each entry in the table as the number of
407           16-bit data units.
408    
409    
410    OPTION NAMES
411    
412           There   are   two   new   general   option   names,   PCRE_UTF16    and
413           PCRE_NO_UTF16_CHECK,     which     correspond    to    PCRE_UTF8    and
414           PCRE_NO_UTF8_CHECK in the 8-bit library. In  fact,  these  new  options
415           define  the  same bits in the options word. There is a discussion about
416           the validity of UTF-16 strings in the pcreunicode page.
417    
418           For the pcre16_config() function there is an  option  PCRE_CONFIG_UTF16
419           that  returns  1  if UTF-16 support is configured, otherwise 0. If this
420           option  is  given  to  pcre_config()  or  pcre32_config(),  or  if  the
421           PCRE_CONFIG_UTF8  or  PCRE_CONFIG_UTF32  option is given to pcre16_con-
422           fig(), the result is the PCRE_ERROR_BADOPTION error.
423    
424    
425    CHARACTER CODES
426    
427           In 16-bit mode, when  PCRE_UTF16  is  not  set,  character  values  are
428           treated in the same way as in 8-bit, non UTF-8 mode, except, of course,
429           that they can range from 0 to 0xffff instead of 0  to  0xff.  Character
430           types  for characters less than 0xff can therefore be influenced by the
431           locale in the same way as before.  Characters greater  than  0xff  have
432           only one case, and no "type" (such as letter or digit).
433    
434           In  UTF-16  mode,  the  character  code  is  Unicode, in the range 0 to
435           0x10ffff, with the exception of values in the range  0xd800  to  0xdfff
436           because  those  are "surrogate" values that are used in pairs to encode
437           values greater than 0xffff.
438    
439           A UTF-16 string can indicate its endianness by special code knows as  a
440           byte-order mark (BOM). The PCRE functions do not handle this, expecting
441           strings  to  be  in  host  byte  order.  A  utility   function   called
442           pcre16_utf16_to_host_byte_order()  is  provided  to help with this (see
443           above).
444    
445    
446    ERROR NAMES
447    
448           The errors PCRE_ERROR_BADUTF16_OFFSET and PCRE_ERROR_SHORTUTF16  corre-
449           spond  to  their  8-bit  counterparts.  The error PCRE_ERROR_BADMODE is
450           given when a compiled pattern is passed to a  function  that  processes
451           patterns  in  the  other  mode, for example, if a pattern compiled with
452           pcre_compile() is passed to pcre16_exec().
453    
454           There are new error codes whose names  begin  with  PCRE_UTF16_ERR  for
455           invalid  UTF-16  strings,  corresponding to the PCRE_UTF8_ERR codes for
456           UTF-8 strings that are described in the section entitled "Reason  codes
457           for  invalid UTF-8 strings" in the main pcreapi page. The UTF-16 errors
458           are:
459    
460             PCRE_UTF16_ERR1  Missing low surrogate at end of string
461             PCRE_UTF16_ERR2  Invalid low surrogate follows high surrogate
462             PCRE_UTF16_ERR3  Isolated low surrogate
463             PCRE_UTF16_ERR4  Non-character
464    
465    
466    ERROR TEXTS
467    
468           If there is an error while compiling a pattern, the error text that  is
469           passed  back by pcre16_compile() or pcre16_compile2() is still an 8-bit
470           character string, zero-terminated.
471    
472    
473    CALLOUTS
474    
475           The subject and mark fields in the callout block that is  passed  to  a
476           callout function point to 16-bit vectors.
477    
478    
479    TESTING
480    
481           The  pcretest  program continues to operate with 8-bit input and output
482           files, but it can be used for testing the 16-bit library. If it is  run
483           with the command line option -16, patterns and subject strings are con-
484           verted from 8-bit to 16-bit before being passed to PCRE, and the 16-bit
485           library  functions  are used instead of the 8-bit ones. Returned 16-bit
486           strings are converted to 8-bit for output. If both the  8-bit  and  the
487           32-bit libraries were not compiled, pcretest defaults to 16-bit and the
488           -16 option is ignored.
489    
490           When PCRE is being built, the RunTest script that is  called  by  "make
491           check"  uses  the  pcretest  -C  option to discover which of the 8-bit,
492           16-bit and 32-bit libraries has been built, and runs the  tests  appro-
493           priately.
494    
495    
496    NOT SUPPORTED IN 16-BIT MODE
497    
498           Not all the features of the 8-bit library are available with the 16-bit
499           library. The C++ and POSIX wrapper functions  support  only  the  8-bit
500           library, and the pcregrep program is at present 8-bit only.
501    
502    
503    AUTHOR
504    
505           Philip Hazel
506           University Computing Service
507           Cambridge CB2 3QH, England.
508    
509    
510    REVISION
511    
512           Last updated: 12 May 2013
513           Copyright (c) 1997-2013 University of Cambridge.
514    ------------------------------------------------------------------------------
515    
516    
517    PCRE(3)                    Library Functions Manual                    PCRE(3)
518    
519    
520    
521    NAME
522           PCRE - Perl-compatible regular expressions
523    
524           #include <pcre.h>
525    
526    
527    PCRE 32-BIT API BASIC FUNCTIONS
528    
529           pcre32 *pcre32_compile(PCRE_SPTR32 pattern, int options,
530                const char **errptr, int *erroffset,
531                const unsigned char *tableptr);
532    
533           pcre32 *pcre32_compile2(PCRE_SPTR32 pattern, int options,
534                int *errorcodeptr,
535                const char **errptr, int *erroffset,
536                const unsigned char *tableptr);
537    
538           pcre32_extra *pcre32_study(const pcre32 *code, int options,
539                const char **errptr);
540    
541           void pcre32_free_study(pcre32_extra *extra);
542    
543           int pcre32_exec(const pcre32 *code, const pcre32_extra *extra,
544                PCRE_SPTR32 subject, int length, int startoffset,
545                int options, int *ovector, int ovecsize);
546    
547           int pcre32_dfa_exec(const pcre32 *code, const pcre32_extra *extra,
548                PCRE_SPTR32 subject, int length, int startoffset,
549                int options, int *ovector, int ovecsize,
550                int *workspace, int wscount);
551    
552    
553    PCRE 32-BIT API STRING EXTRACTION FUNCTIONS
554    
555           int pcre32_copy_named_substring(const pcre32 *code,
556                PCRE_SPTR32 subject, int *ovector,
557                int stringcount, PCRE_SPTR32 stringname,
558                PCRE_UCHAR32 *buffer, int buffersize);
559    
560           int pcre32_copy_substring(PCRE_SPTR32 subject, int *ovector,
561                int stringcount, int stringnumber, PCRE_UCHAR32 *buffer,
562                int buffersize);
563    
564           int pcre32_get_named_substring(const pcre32 *code,
565                PCRE_SPTR32 subject, int *ovector,
566                int stringcount, PCRE_SPTR32 stringname,
567                PCRE_SPTR32 *stringptr);
568    
569           int pcre32_get_stringnumber(const pcre32 *code,
570                PCRE_SPTR32 name);
571    
572           int pcre32_get_stringtable_entries(const pcre32 *code,
573                PCRE_SPTR32 name, PCRE_UCHAR32 **first, PCRE_UCHAR32 **last);
574    
575           int pcre32_get_substring(PCRE_SPTR32 subject, int *ovector,
576                int stringcount, int stringnumber,
577                PCRE_SPTR32 *stringptr);
578    
579           int pcre32_get_substring_list(PCRE_SPTR32 subject,
580                int *ovector, int stringcount, PCRE_SPTR32 **listptr);
581    
582           void pcre32_free_substring(PCRE_SPTR32 stringptr);
583    
584           void pcre32_free_substring_list(PCRE_SPTR32 *stringptr);
585    
586    
587    PCRE 32-BIT API AUXILIARY FUNCTIONS
588    
589           pcre32_jit_stack *pcre32_jit_stack_alloc(int startsize, int maxsize);
590    
591           void pcre32_jit_stack_free(pcre32_jit_stack *stack);
592    
593           void pcre32_assign_jit_stack(pcre32_extra *extra,
594                pcre32_jit_callback callback, void *data);
595    
596           const unsigned char *pcre32_maketables(void);
597    
598           int pcre32_fullinfo(const pcre32 *code, const pcre32_extra *extra,
599                int what, void *where);
600    
601           int pcre32_refcount(pcre32 *code, int adjust);
602    
603           int pcre32_config(int what, void *where);
604    
605           const char *pcre32_version(void);
606    
607           int pcre32_pattern_to_host_byte_order(pcre32 *code,
608                pcre32_extra *extra, const unsigned char *tables);
609    
610    
611    PCRE 32-BIT API INDIRECTED FUNCTIONS
612    
613           void *(*pcre32_malloc)(size_t);
614    
615           void (*pcre32_free)(void *);
616    
617           void *(*pcre32_stack_malloc)(size_t);
618    
619           void (*pcre32_stack_free)(void *);
620    
621           int (*pcre32_callout)(pcre32_callout_block *);
622    
623    
624    PCRE 32-BIT API 32-BIT-ONLY FUNCTION
625    
626           int pcre32_utf32_to_host_byte_order(PCRE_UCHAR32 *output,
627                PCRE_SPTR32 input, int length, int *byte_order,
628                int keep_boms);
629    
630    
631    THE PCRE 32-BIT LIBRARY
632    
633           Starting  with  release  8.32, it is possible to compile a PCRE library
634           that supports 32-bit character strings, including  UTF-32  strings,  as
635           well as or instead of the original 8-bit library. This work was done by
636           Christian Persch, based on the work done  by  Zoltan  Herczeg  for  the
637           16-bit  library.  All  three  libraries contain identical sets of func-
638           tions, used in exactly the same way.  Only the names of  the  functions
639           and  the  data  types  of their arguments and results are different. To
640           avoid over-complication and reduce the documentation maintenance  load,
641           most  of  the PCRE documentation describes the 8-bit library, with only
642           occasional references to the 16-bit and  32-bit  libraries.  This  page
643           describes what is different when you use the 32-bit library.
644    
645           WARNING:  A  single  application  can  be linked with all or any of the
646           three libraries, but you must take care when processing any  particular
647           pattern  to  use  functions  from just one library. For example, if you
648           want to study a pattern that was compiled  with  pcre32_compile(),  you
649           must do so with pcre32_study(), not pcre_study(), and you must free the
650           study data with pcre32_free_study().
651    
652    
653    THE HEADER FILE
654    
655           There is only one header file, pcre.h. It contains prototypes  for  all
656           the functions in all libraries, as well as definitions of flags, struc-
657           tures, error codes, etc.
658    
659    
660    THE LIBRARY NAME
661    
662           In Unix-like systems, the 32-bit library is called libpcre32,  and  can
663           normally  be  accesss  by adding -lpcre32 to the command for linking an
664           application that uses PCRE.
665    
666    
667    STRING TYPES
668    
669           In the 8-bit library, strings are passed to PCRE library  functions  as
670           vectors  of  bytes  with  the  C  type "char *". In the 32-bit library,
671           strings are passed as vectors of unsigned 32-bit quantities. The  macro
672           PCRE_UCHAR32  specifies  an  appropriate  data type, and PCRE_SPTR32 is
673           defined as "const PCRE_UCHAR32 *". In very many environments, "unsigned
674           int" is a 32-bit data type. When PCRE is built, it defines PCRE_UCHAR32
675           as "unsigned int", but checks that it really is a 32-bit data type.  If
676           it is not, the build fails with an error message telling the maintainer
677           to modify the definition appropriately.
678    
679    
680    STRUCTURE TYPES
681    
682           The types of the opaque structures that are used  for  compiled  32-bit
683           patterns  and  JIT stacks are pcre32 and pcre32_jit_stack respectively.
684           The  type  of  the  user-accessible  structure  that  is  returned   by
685           pcre32_study()  is  pcre32_extra, and the type of the structure that is
686           used for passing data to a callout  function  is  pcre32_callout_block.
687           These structures contain the same fields, with the same names, as their
688           8-bit counterparts. The only difference is that pointers  to  character
689           strings are 32-bit instead of 8-bit types.
690    
691    
692    32-BIT FUNCTIONS
693    
694           For  every function in the 8-bit library there is a corresponding func-
695           tion in the 32-bit library with a name that starts with pcre32_ instead
696           of  pcre_.  The  prototypes are listed above. In addition, there is one
697           extra function, pcre32_utf32_to_host_byte_order(). This  is  a  utility
698           function  that converts a UTF-32 character string to host byte order if
699           necessary. The other 32-bit  functions  expect  the  strings  they  are
700           passed to be in host byte order.
701    
702           The input and output arguments of pcre32_utf32_to_host_byte_order() may
703           point to the same address, that is, conversion in place  is  supported.
704           The output buffer must be at least as long as the input.
705    
706           The  length  argument  specifies the number of 32-bit data units in the
707           input string; a negative value specifies a zero-terminated string.
708    
709           If byte_order is NULL, it is assumed that the string starts off in host
710           byte  order. This may be changed by byte-order marks (BOMs) anywhere in
711           the string (commonly as the first character).
712    
713           If byte_order is not NULL, a non-zero value of the integer to which  it
714           points  means  that  the input starts off in host byte order, otherwise
715           the opposite order is assumed. Again, BOMs in  the  string  can  change
716           this. The final byte order is passed back at the end of processing.
717    
718           If  keep_boms  is  not  zero,  byte-order  mark characters (0xfeff) are
719           copied into the output string. Otherwise they are discarded.
720    
721           The result of the function is the number of 32-bit  units  placed  into
722           the  output  buffer,  including  the  zero terminator if the string was
723           zero-terminated.
724    
725    
726    SUBJECT STRING OFFSETS
727    
728           The lengths and starting offsets of subject strings must  be  specified
729           in  32-bit  data units, and the offsets within subject strings that are
730           returned by the matching functions are in also 32-bit units rather than
731           bytes.
732    
733    
734    NAMED SUBPATTERNS
735    
736           The  name-to-number translation table that is maintained for named sub-
737           patterns uses 32-bit characters.  The  pcre32_get_stringtable_entries()
738           function returns the length of each entry in the table as the number of
739           32-bit data units.
740    
741    
742    OPTION NAMES
743    
744           There   are   two   new   general   option   names,   PCRE_UTF32    and
745           PCRE_NO_UTF32_CHECK,     which     correspond    to    PCRE_UTF8    and
746           PCRE_NO_UTF8_CHECK in the 8-bit library. In  fact,  these  new  options
747           define  the  same bits in the options word. There is a discussion about
748           the validity of UTF-32 strings in the pcreunicode page.
749    
750           For the pcre32_config() function there is an  option  PCRE_CONFIG_UTF32
751           that  returns  1  if UTF-32 support is configured, otherwise 0. If this
752           option  is  given  to  pcre_config()  or  pcre16_config(),  or  if  the
753           PCRE_CONFIG_UTF8  or  PCRE_CONFIG_UTF16  option is given to pcre32_con-
754           fig(), the result is the PCRE_ERROR_BADOPTION error.
755    
756    
757    CHARACTER CODES
758    
759           In 32-bit mode, when  PCRE_UTF32  is  not  set,  character  values  are
760           treated in the same way as in 8-bit, non UTF-8 mode, except, of course,
761           that they can range from 0 to 0x7fffffff instead of 0 to 0xff.  Charac-
762           ter  types for characters less than 0xff can therefore be influenced by
763           the locale in the same way as before.   Characters  greater  than  0xff
764           have only one case, and no "type" (such as letter or digit).
765    
766           In  UTF-32  mode,  the  character  code  is  Unicode, in the range 0 to
767           0x10ffff, with the exception of values in the range  0xd800  to  0xdfff
768           because those are "surrogate" values that are ill-formed in UTF-32.
769    
770           A  UTF-32 string can indicate its endianness by special code knows as a
771           byte-order mark (BOM). The PCRE functions do not handle this, expecting
772           strings   to   be  in  host  byte  order.  A  utility  function  called
773           pcre32_utf32_to_host_byte_order() is provided to help  with  this  (see
774           above).
775    
776    
777    ERROR NAMES
778    
779           The  error  PCRE_ERROR_BADUTF32  corresponds  to its 8-bit counterpart.
780           The error PCRE_ERROR_BADMODE is given when a compiled pattern is passed
781           to  a  function that processes patterns in the other mode, for example,
782           if a pattern compiled with pcre_compile() is passed to pcre32_exec().
783    
784           There are new error codes whose names  begin  with  PCRE_UTF32_ERR  for
785           invalid  UTF-32  strings,  corresponding to the PCRE_UTF8_ERR codes for
786           UTF-8 strings that are described in the section entitled "Reason  codes
787           for  invalid UTF-8 strings" in the main pcreapi page. The UTF-32 errors
788           are:
789    
790             PCRE_UTF32_ERR1  Surrogate character (range from 0xd800 to 0xdfff)
791             PCRE_UTF32_ERR2  Non-character
792             PCRE_UTF32_ERR3  Character > 0x10ffff
793    
794    
795    ERROR TEXTS
796    
797           If there is an error while compiling a pattern, the error text that  is
798           passed  back by pcre32_compile() or pcre32_compile2() is still an 8-bit
799           character string, zero-terminated.
800    
801    
802    CALLOUTS
803    
804           The subject and mark fields in the callout block that is  passed  to  a
805           callout function point to 32-bit vectors.
806    
807    
808    TESTING
809    
810           The  pcretest  program continues to operate with 8-bit input and output
811           files, but it can be used for testing the 32-bit library. If it is  run
812           with the command line option -32, patterns and subject strings are con-
813           verted from 8-bit to 32-bit before being passed to PCRE, and the 32-bit
814           library  functions  are used instead of the 8-bit ones. Returned 32-bit
815           strings are converted to 8-bit for output. If both the  8-bit  and  the
816           16-bit libraries were not compiled, pcretest defaults to 32-bit and the
817           -32 option is ignored.
818    
819           When PCRE is being built, the RunTest script that is  called  by  "make
820           check"  uses  the  pcretest  -C  option to discover which of the 8-bit,
821           16-bit and 32-bit libraries has been built, and runs the  tests  appro-
822           priately.
823    
824    
825    NOT SUPPORTED IN 32-BIT MODE
826    
827           Not all the features of the 8-bit library are available with the 32-bit
828           library. The C++ and POSIX wrapper functions  support  only  the  8-bit
829           library, and the pcregrep program is at present 8-bit only.
830    
831    
832    AUTHOR
833    
834           Philip Hazel
835           University Computing Service
836           Cambridge CB2 3QH, England.
837    
838    
839    REVISION
840    
841           Last updated: 12 May 2013
842           Copyright (c) 1997-2013 University of Cambridge.
843    ------------------------------------------------------------------------------
844    
845    
846    PCREBUILD(3)               Library Functions Manual               PCREBUILD(3)
847    
848    
849    
850    NAME
851           PCRE - Perl-compatible regular expressions
852    
853    BUILDING PCRE
854    
855           PCRE  is  distributed with a configure script that can be used to build
856           the library in Unix-like environments using the applications  known  as
857           Autotools.   Also  in  the  distribution  are files to support building
858           using CMake instead of configure. The text file README contains general
859           information  about  building  with Autotools (some of which is repeated
860           below), and also has some comments about building on various  operating
861           systems.  There  is  a lot more information about building PCRE without
862           using Autotools (including information about using CMake  and  building
863           "by  hand")  in  the  text file called NON-AUTOTOOLS-BUILD.  You should
864           consult this file as well as the README file if you are building  in  a
865           non-Unix-like environment.
866    
867    
868    PCRE BUILD-TIME OPTIONS
869    
870           The  rest of this document describes the optional features of PCRE that
871           can be selected when the library is compiled. It  assumes  use  of  the
872           configure  script,  where  the  optional features are selected or dese-
873           lected by providing options to configure before running the  make  com-
874           mand.  However,  the same options can be selected in both Unix-like and
875           non-Unix-like environments using the GUI facility of cmake-gui  if  you
876           are using CMake instead of configure to build PCRE.
877    
878           If  you  are not using Autotools or CMake, option selection can be done
879           by editing the config.h file, or by passing parameter settings  to  the
880           compiler, as described in NON-AUTOTOOLS-BUILD.
881    
882           The complete list of options for configure (which includes the standard
883           ones such as the  selection  of  the  installation  directory)  can  be
884           obtained by running
885    
886             ./configure --help
887    
888           The  following  sections  include  descriptions  of options whose names
889           begin with --enable or --disable. These settings specify changes to the
890           defaults  for  the configure command. Because of the way that configure
891           works, --enable and --disable always come in pairs, so  the  complemen-
892           tary  option always exists as well, but as it specifies the default, it
893           is not described.
894    
895    
896    BUILDING 8-BIT, 16-BIT AND 32-BIT LIBRARIES
897    
898           By default, a library called libpcre  is  built,  containing  functions
899           that  take  string  arguments  contained in vectors of bytes, either as
900           single-byte characters, or interpreted as UTF-8 strings. You  can  also
901           build  a  separate library, called libpcre16, in which strings are con-
902           tained in vectors of 16-bit data units and interpreted either  as  sin-
903           gle-unit characters or UTF-16 strings, by adding
904    
905             --enable-pcre16
906    
907           to  the  configure  command.  You  can  also build yet another separate
908           library, called libpcre32, in which strings are contained in vectors of
909           32-bit  data  units and interpreted either as single-unit characters or
910           UTF-32 strings, by adding
911    
912             --enable-pcre32
913    
914           to the configure command. If you do not want the 8-bit library, add
915    
916             --disable-pcre8
917    
918           as well. At least one of the three libraries must be built.  Note  that
919           the  C++  and  POSIX  wrappers are for the 8-bit library only, and that
920           pcregrep is an 8-bit program. None of these are  built  if  you  select
921           only the 16-bit or 32-bit libraries.
922    
923    
924    BUILDING SHARED AND STATIC LIBRARIES
925    
926           The  Autotools  PCRE building process uses libtool to build both shared
927           and static libraries by default. You  can  suppress  one  of  these  by
928           adding one of
929    
930             --disable-shared
931             --disable-static
932    
933           to the configure command, as required.
934    
935    
936    C++ SUPPORT
937    
938           By  default,  if the 8-bit library is being built, the configure script
939           will search for a C++ compiler and C++ header files. If it finds  them,
940           it  automatically  builds  the C++ wrapper library (which supports only
941           8-bit strings). You can disable this by adding
942    
943             --disable-cpp
944    
945           to the configure command.
946    
947    
948    UTF-8, UTF-16 AND UTF-32 SUPPORT
949    
950           To build PCRE with support for UTF Unicode character strings, add
951    
952             --enable-utf
953    
954           to the configure command. This setting applies to all three  libraries,
955           adding  support  for  UTF-8 to the 8-bit library, support for UTF-16 to
956           the 16-bit library, and  support  for  UTF-32  to  the  to  the  32-bit
957           library.  There  are no separate options for enabling UTF-8, UTF-16 and
958           UTF-32 independently because that would allow ridiculous settings  such
959           as  requesting UTF-16 support while building only the 8-bit library. It
960           is not possible to build one library with UTF support and another with-
961           out  in the same configuration. (For backwards compatibility, --enable-
962           utf8 is a synonym of --enable-utf.)
963    
964           Of itself, this setting does not make  PCRE  treat  strings  as  UTF-8,
965           UTF-16  or UTF-32. As well as compiling PCRE with this option, you also
966           have have to set the PCRE_UTF8, PCRE_UTF16  or  PCRE_UTF32  option  (as
967           appropriate) when you call one of the pattern compiling functions.
968    
969           If  you  set --enable-utf when compiling in an EBCDIC environment, PCRE
970           expects its input to be either ASCII or UTF-8 (depending  on  the  run-
971           time option). It is not possible to support both EBCDIC and UTF-8 codes
972           in the same version of  the  library.  Consequently,  --enable-utf  and
973           --enable-ebcdic are mutually exclusive.
974    
975    
976    UNICODE CHARACTER PROPERTY SUPPORT
977    
978           UTF  support allows the libraries to process character codepoints up to
979           0x10ffff in the strings that they handle. On its own, however, it  does
980           not provide any facilities for accessing the properties of such charac-
981           ters. If you want to be able to use the pattern escapes \P, \p, and \X,
982           which refer to Unicode character properties, you must add
983    
984             --enable-unicode-properties
985    
986           to  the  configure  command. This implies UTF support, even if you have
987           not explicitly requested it.
988    
989           Including Unicode property support adds around 30K  of  tables  to  the
990           PCRE  library.  Only  the general category properties such as Lu and Nd
991           are supported. Details are given in the pcrepattern documentation.
992    
993    
994    JUST-IN-TIME COMPILER SUPPORT
995    
996           Just-in-time compiler support is included in the build by specifying
997    
998             --enable-jit
999    
1000           This support is available only for certain hardware  architectures.  If
1001           this  option  is  set  for  an unsupported architecture, a compile time
1002           error occurs.  See the pcrejit documentation for a  discussion  of  JIT
1003           usage. When JIT support is enabled, pcregrep automatically makes use of
1004           it, unless you add
1005    
1006             --disable-pcregrep-jit
1007    
1008           to the "configure" command.
1009    
1010    
1011    CODE VALUE OF NEWLINE
1012    
1013           By default, PCRE interprets the linefeed (LF) character  as  indicating
1014           the  end  of  a line. This is the normal newline character on Unix-like
1015           systems. You can compile PCRE to use carriage return (CR)  instead,  by
1016           adding
1017    
1018             --enable-newline-is-cr
1019    
1020           to  the  configure  command.  There  is  also  a --enable-newline-is-lf
1021           option, which explicitly specifies linefeed as the newline character.
1022    
1023           Alternatively, you can specify that line endings are to be indicated by
1024           the two character sequence CRLF. If you want this, add
1025    
1026             --enable-newline-is-crlf
1027    
1028           to the configure command. There is a fourth option, specified by
1029    
1030             --enable-newline-is-anycrlf
1031    
1032           which  causes  PCRE  to recognize any of the three sequences CR, LF, or
1033           CRLF as indicating a line ending. Finally, a fifth option, specified by
1034    
1035             --enable-newline-is-any
1036    
1037           causes PCRE to recognize any Unicode newline sequence.
1038    
1039           Whatever line ending convention is selected when PCRE is built  can  be
1040           overridden  when  the library functions are called. At build time it is
1041           conventional to use the standard for your operating system.
1042    
1043    
1044    WHAT \R MATCHES
1045    
1046           By default, the sequence \R in a pattern matches  any  Unicode  newline
1047           sequence,  whatever  has  been selected as the line ending sequence. If
1048           you specify
1049    
1050             --enable-bsr-anycrlf
1051    
1052           the default is changed so that \R matches only CR, LF, or  CRLF.  What-
1053           ever  is selected when PCRE is built can be overridden when the library
1054           functions are called.
1055    
1056    
1057    POSIX MALLOC USAGE
1058    
1059           When the 8-bit library is called through the POSIX interface  (see  the
1060           pcreposix  documentation),  additional  working storage is required for
1061           holding the pointers to capturing  substrings,  because  PCRE  requires
1062           three integers per substring, whereas the POSIX interface provides only
1063           two. If the number of expected substrings is small, the  wrapper  func-
1064           tion  uses  space  on the stack, because this is faster than using mal-
1065           loc() for each call. The default threshold above which the stack is  no
1066           longer used is 10; it can be changed by adding a setting such as
1067    
1068             --with-posix-malloc-threshold=20
1069    
1070           to the configure command.
1071    
1072    
1073    HANDLING VERY LARGE PATTERNS
1074    
1075           Within  a  compiled  pattern,  offset values are used to point from one
1076           part to another (for example, from an opening parenthesis to an  alter-
1077           nation  metacharacter).  By default, in the 8-bit and 16-bit libraries,
1078           two-byte values are used for these offsets, leading to a  maximum  size
1079           for  a compiled pattern of around 64K. This is sufficient to handle all
1080           but the most gigantic patterns.  Nevertheless, some people do  want  to
1081           process  truly  enormous patterns, so it is possible to compile PCRE to
1082           use three-byte or four-byte offsets by adding a setting such as
1083    
1084             --with-link-size=3
1085    
1086           to the configure command. The value given must be 2, 3, or 4.  For  the
1087           16-bit  library,  a  value of 3 is rounded up to 4. In these libraries,
1088           using longer offsets slows down the operation of PCRE because it has to
1089           load  additional  data  when  handling them. For the 32-bit library the
1090           value is always 4 and cannot be overridden; the value  of  --with-link-
1091           size is ignored.
1092    
1093    
1094    AVOIDING EXCESSIVE STACK USAGE
1095    
1096           When matching with the pcre_exec() function, PCRE implements backtrack-
1097           ing by making recursive calls to an internal function  called  match().
1098           In  environments  where  the size of the stack is limited, this can se-
1099           verely limit PCRE's operation. (The Unix environment does  not  usually
1100           suffer from this problem, but it may sometimes be necessary to increase
1101           the maximum stack size.  There is a discussion in the  pcrestack  docu-
1102           mentation.)  An alternative approach to recursion that uses memory from
1103           the heap to remember data, instead of using recursive  function  calls,
1104           has  been  implemented to work round the problem of limited stack size.
1105           If you want to build a version of PCRE that works this way, add
1106    
1107             --disable-stack-for-recursion
1108    
1109           to the configure command. With this configuration, PCRE  will  use  the
1110           pcre_stack_malloc  and pcre_stack_free variables to call memory manage-
1111           ment functions. By default these point to malloc() and free(), but  you
1112           can replace the pointers so that your own functions are used instead.
1113    
1114           Separate  functions  are  provided  rather  than  using pcre_malloc and
1115           pcre_free because the  usage  is  very  predictable:  the  block  sizes
1116           requested  are  always  the  same,  and  the blocks are always freed in
1117           reverse order. A calling program might be able to  implement  optimized
1118           functions  that  perform  better  than  malloc()  and free(). PCRE runs
1119           noticeably more slowly when built in this way. This option affects only
1120           the pcre_exec() function; it is not relevant for pcre_dfa_exec().
1121    
1122    
1123    LIMITING PCRE RESOURCE USAGE
1124    
1125           Internally,  PCRE has a function called match(), which it calls repeat-
1126           edly  (sometimes  recursively)  when  matching  a  pattern   with   the
1127           pcre_exec()  function.  By controlling the maximum number of times this
1128           function may be called during a single matching operation, a limit  can
1129           be  placed  on  the resources used by a single call to pcre_exec(). The
1130           limit can be changed at run time, as described in the pcreapi  documen-
1131           tation.  The default is 10 million, but this can be changed by adding a
1132           setting such as
1133    
1134             --with-match-limit=500000
1135    
1136           to  the  configure  command.  This  setting  has  no  effect   on   the
1137           pcre_dfa_exec() matching function.
1138    
1139           In  some  environments  it is desirable to limit the depth of recursive
1140           calls of match() more strictly than the total number of calls, in order
1141           to  restrict  the maximum amount of stack (or heap, if --disable-stack-
1142           for-recursion is specified) that is used. A second limit controls this;
1143           it  defaults  to  the  value  that is set for --with-match-limit, which
1144           imposes no additional constraints. However, you can set a  lower  limit
1145           by adding, for example,
1146    
1147             --with-match-limit-recursion=10000
1148    
1149           to  the  configure  command.  This  value can also be overridden at run
1150           time.
1151    
1152    
1153    CREATING CHARACTER TABLES AT BUILD TIME
1154    
1155           PCRE uses fixed tables for processing characters whose code values  are
1156           less  than 256. By default, PCRE is built with a set of tables that are
1157           distributed in the file pcre_chartables.c.dist. These  tables  are  for
1158           ASCII codes only. If you add
1159    
1160             --enable-rebuild-chartables
1161    
1162           to  the  configure  command, the distributed tables are no longer used.
1163           Instead, a program called dftables is compiled and  run.  This  outputs
1164           the source for new set of tables, created in the default locale of your
1165           C run-time system. (This method of replacing the tables does  not  work
1166           if  you are cross compiling, because dftables is run on the local host.
1167           If you need to create alternative tables when cross compiling, you will
1168           have to do so "by hand".)
1169    
1170    
1171    USING EBCDIC CODE
1172    
1173           PCRE  assumes  by  default that it will run in an environment where the
1174           character code is ASCII (or Unicode, which is  a  superset  of  ASCII).
1175           This  is  the  case for most computer operating systems. PCRE can, how-
1176           ever, be compiled to run in an EBCDIC environment by adding
1177    
1178             --enable-ebcdic
1179    
1180           to the configure command. This setting implies --enable-rebuild-charta-
1181           bles.  You  should  only  use  it if you know that you are in an EBCDIC
1182           environment (for example,  an  IBM  mainframe  operating  system).  The
1183           --enable-ebcdic option is incompatible with --enable-utf.
1184    
1185           The EBCDIC character that corresponds to an ASCII LF is assumed to have
1186           the value 0x15 by default. However, in some EBCDIC  environments,  0x25
1187           is used. In such an environment you should use
1188    
1189             --enable-ebcdic-nl25
1190    
1191           as well as, or instead of, --enable-ebcdic. The EBCDIC character for CR
1192           has the same value as in ASCII, namely, 0x0d.  Whichever  of  0x15  and
1193           0x25 is not chosen as LF is made to correspond to the Unicode NEL char-
1194           acter (which, in Unicode, is 0x85).
1195    
1196           The options that select newline behaviour, such as --enable-newline-is-
1197           cr, and equivalent run-time options, refer to these character values in
1198           an EBCDIC environment.
1199    
1200    
1201    PCREGREP OPTIONS FOR COMPRESSED FILE SUPPORT
1202    
1203           By default, pcregrep reads all files as plain text. You can build it so
1204           that it recognizes files whose names end in .gz or .bz2, and reads them
1205           with libz or libbz2, respectively, by adding one or both of
1206    
1207             --enable-pcregrep-libz
1208             --enable-pcregrep-libbz2
1209    
1210           to the configure command. These options naturally require that the rel-
1211           evant  libraries  are installed on your system. Configuration will fail
1212           if they are not.
1213    
1214    
1215    PCREGREP BUFFER SIZE
1216    
1217           pcregrep uses an internal buffer to hold a "window" on the file  it  is
1218           scanning, in order to be able to output "before" and "after" lines when
1219           it finds a match. The size of the buffer is controlled by  a  parameter
1220           whose default value is 20K. The buffer itself is three times this size,
1221           but because of the way it is used for holding "before" lines, the long-
1222           est  line  that  is guaranteed to be processable is the parameter size.
1223           You can change the default parameter value by adding, for example,
1224    
1225             --with-pcregrep-bufsize=50K
1226    
1227           to the configure command. The caller of pcregrep can, however, override
1228           this value by specifying a run-time option.
1229    
1230    
1231    PCRETEST OPTION FOR LIBREADLINE SUPPORT
1232    
1233           If you add
1234    
1235             --enable-pcretest-libreadline
1236    
1237           to  the  configure  command,  pcretest  is  linked with the libreadline
1238           library, and when its input is from a terminal, it reads it  using  the
1239           readline() function. This provides line-editing and history facilities.
1240           Note that libreadline is GPL-licensed, so if you distribute a binary of
1241           pcretest linked in this way, there may be licensing issues.
1242    
1243           Setting  this  option  causes  the -lreadline option to be added to the
1244           pcretest build. In many operating environments with  a  sytem-installed
1245           libreadline this is sufficient. However, in some environments (e.g.  if
1246           an unmodified distribution version of readline is in use),  some  extra
1247           configuration  may  be necessary. The INSTALL file for libreadline says
1248           this:
1249    
1250             "Readline uses the termcap functions, but does not link with the
1251             termcap or curses library itself, allowing applications which link
1252             with readline the to choose an appropriate library."
1253    
1254           If your environment has not been set up so that an appropriate  library
1255           is automatically included, you may need to add something like
1256    
1257             LIBS="-ncurses"
1258    
1259           immediately before the configure command.
1260    
1261    
1262    DEBUGGING WITH VALGRIND SUPPORT
1263    
1264           By adding the
1265    
1266             --enable-valgrind
1267    
1268           option  to to the configure command, PCRE will use valgrind annotations
1269           to mark certain memory regions as  unaddressable.  This  allows  it  to
1270           detect invalid memory accesses, and is mostly useful for debugging PCRE
1271           itself.
1272    
1273    
1274    CODE COVERAGE REPORTING
1275    
1276           If your C compiler is gcc, you can build a version  of  PCRE  that  can
1277           generate a code coverage report for its test suite. To enable this, you
1278           must install lcov version 1.6 or above. Then specify
1279    
1280             --enable-coverage
1281    
1282           to the configure command and build PCRE in the usual way.
1283    
1284           Note that using ccache (a caching C compiler) is incompatible with code
1285           coverage  reporting. If you have configured ccache to run automatically
1286           on your system, you must set the environment variable
1287    
1288             CCACHE_DISABLE=1
1289    
1290           before running make to build PCRE, so that ccache is not used.
1291    
1292           When --enable-coverage is used,  the  following  addition  targets  are
1293           added to the Makefile:
1294    
1295             make coverage
1296    
1297           This  creates  a  fresh  coverage report for the PCRE test suite. It is
1298           equivalent to running "make coverage-reset", "make  coverage-baseline",
1299           "make check", and then "make coverage-report".
1300    
1301             make coverage-reset
1302    
1303           This zeroes the coverage counters, but does nothing else.
1304    
1305             make coverage-baseline
1306    
1307           This captures baseline coverage information.
1308    
1309             make coverage-report
1310    
1311           This creates the coverage report.
1312    
1313             make coverage-clean-report
1314    
1315           This  removes the generated coverage report without cleaning the cover-
1316           age data itself.
1317    
1318             make coverage-clean-data
1319    
1320           This removes the captured coverage data without removing  the  coverage
1321           files created at compile time (*.gcno).
1322    
1323             make coverage-clean
1324    
1325           This  cleans all coverage data including the generated coverage report.
1326           For more information about code coverage, see the gcov and  lcov  docu-
1327           mentation.
1328    
1329    
1330    SEE ALSO
1331    
1332           pcreapi(3), pcre16, pcre32, pcre_config(3).
1333    
1334    
1335    AUTHOR
1336    
1337           Philip Hazel
1338           University Computing Service
1339           Cambridge CB2 3QH, England.
1340    
1341    
1342    REVISION
1343    
1344           Last updated: 12 May 2013
1345           Copyright (c) 1997-2013 University of Cambridge.
1346    ------------------------------------------------------------------------------
1347    
1348    
1349    PCREMATCHING(3)            Library Functions Manual            PCREMATCHING(3)
1350    
1351    
1352    
1353    NAME
1354           PCRE - Perl-compatible regular expressions
1355    
1356    PCRE MATCHING ALGORITHMS
1357    
1358           This document describes the two different algorithms that are available
1359           in PCRE for matching a compiled regular expression against a given sub-
1360           ject  string.  The  "standard"  algorithm  is  the  one provided by the
1361           pcre_exec(), pcre16_exec() and pcre32_exec() functions. These  work  in
1362           the  same as as Perl's matching function, and provide a Perl-compatible
1363           matching  operation.   The  just-in-time  (JIT)  optimization  that  is
1364           described  in  the pcrejit documentation is compatible with these func-
1365           tions.
1366    
1367           An  alternative  algorithm  is   provided   by   the   pcre_dfa_exec(),
1368           pcre16_dfa_exec()  and  pcre32_dfa_exec()  functions; they operate in a
1369           different way, and are not Perl-compatible. This alternative has advan-
1370           tages and disadvantages compared with the standard algorithm, and these
1371           are described below.
1372    
1373           When there is only one possible way in which a given subject string can
1374           match  a pattern, the two algorithms give the same answer. A difference
1375           arises, however, when there are multiple possibilities. For example, if
1376           the pattern
1377    
1378             ^<.*>
1379    
1380           is matched against the string
1381    
1382             <something> <something else> <something further>
1383    
1384           there are three possible answers. The standard algorithm finds only one
1385           of them, whereas the alternative algorithm finds all three.
1386    
1387    
1388    REGULAR EXPRESSIONS AS TREES
1389    
1390           The set of strings that are matched by a regular expression can be rep-
1391           resented  as  a  tree structure. An unlimited repetition in the pattern
1392           makes the tree of infinite size, but it is still a tree.  Matching  the
1393           pattern  to a given subject string (from a given starting point) can be
1394           thought of as a search of the tree.  There are two  ways  to  search  a
1395           tree:  depth-first  and  breadth-first, and these correspond to the two
1396           matching algorithms provided by PCRE.
1397    
1398    
1399    THE STANDARD MATCHING ALGORITHM
1400    
1401           In the terminology of Jeffrey Friedl's book "Mastering Regular  Expres-
1402           sions",  the  standard  algorithm  is an "NFA algorithm". It conducts a
1403           depth-first search of the pattern tree. That is, it  proceeds  along  a
1404           single path through the tree, checking that the subject matches what is
1405           required. When there is a mismatch, the algorithm  tries  any  alterna-
1406           tives  at  the  current point, and if they all fail, it backs up to the
1407           previous branch point in the  tree,  and  tries  the  next  alternative
1408           branch  at  that  level.  This often involves backing up (moving to the
1409           left) in the subject string as well.  The  order  in  which  repetition
1410           branches  are  tried  is controlled by the greedy or ungreedy nature of
1411           the quantifier.
1412    
1413           If a leaf node is reached, a matching string has  been  found,  and  at
1414           that  point the algorithm stops. Thus, if there is more than one possi-
1415           ble match, this algorithm returns the first one that it finds.  Whether
1416           this  is the shortest, the longest, or some intermediate length depends
1417           on the way the greedy and ungreedy repetition quantifiers are specified
1418           in the pattern.
1419    
1420           Because  it  ends  up  with a single path through the tree, it is rela-
1421           tively straightforward for this algorithm to keep  track  of  the  sub-
1422           strings  that  are  matched  by portions of the pattern in parentheses.
1423           This provides support for capturing parentheses and back references.
1424    
1425    
1426    THE ALTERNATIVE MATCHING ALGORITHM
1427    
1428           This algorithm conducts a breadth-first search of  the  tree.  Starting
1429           from  the  first  matching  point  in the subject, it scans the subject
1430           string from left to right, once, character by character, and as it does
1431           this,  it remembers all the paths through the tree that represent valid
1432           matches. In Friedl's terminology, this is a kind  of  "DFA  algorithm",
1433           though  it is not implemented as a traditional finite state machine (it
1434           keeps multiple states active simultaneously).
1435    
1436           Although the general principle of this matching algorithm  is  that  it
1437           scans  the subject string only once, without backtracking, there is one
1438           exception: when a lookaround assertion is encountered,  the  characters
1439           following  or  preceding  the  current  point  have to be independently
1440           inspected.
1441    
1442           The scan continues until either the end of the subject is  reached,  or
1443           there  are  no more unterminated paths. At this point, terminated paths
1444           represent the different matching possibilities (if there are none,  the
1445           match  has  failed).   Thus,  if there is more than one possible match,
1446           this algorithm finds all of them, and in particular, it finds the long-
1447           est.  The  matches are returned in decreasing order of length. There is
1448           an option to stop the algorithm after the first match (which is  neces-
1449           sarily the shortest) is found.
1450    
1451           Note that all the matches that are found start at the same point in the
1452           subject. If the pattern
1453    
1454             cat(er(pillar)?)?
1455    
1456           is matched against the string "the caterpillar catchment",  the  result
1457           will  be the three strings "caterpillar", "cater", and "cat" that start
1458           at the fifth character of the subject. The algorithm does not automati-
1459           cally move on to find matches that start at later positions.
1460    
1461           There are a number of features of PCRE regular expressions that are not
1462           supported by the alternative matching algorithm. They are as follows:
1463    
1464           1. Because the algorithm finds all  possible  matches,  the  greedy  or
1465           ungreedy  nature  of repetition quantifiers is not relevant. Greedy and
1466           ungreedy quantifiers are treated in exactly the same way. However, pos-
1467           sessive  quantifiers can make a difference when what follows could also
1468           match what is quantified, for example in a pattern like this:
1469    
1470             ^a++\w!
1471    
1472           This pattern matches "aaab!" but not "aaa!", which would be matched  by
1473           a  non-possessive quantifier. Similarly, if an atomic group is present,
1474           it is matched as if it were a standalone pattern at the current  point,
1475           and  the  longest match is then "locked in" for the rest of the overall
1476           pattern.
1477    
1478           2. When dealing with multiple paths through the tree simultaneously, it
1479           is  not  straightforward  to  keep track of captured substrings for the
1480           different matching possibilities, and  PCRE's  implementation  of  this
1481           algorithm does not attempt to do this. This means that no captured sub-
1482           strings are available.
1483    
1484           3. Because no substrings are captured, back references within the  pat-
1485           tern are not supported, and cause errors if encountered.
1486    
1487           4.  For  the same reason, conditional expressions that use a backrefer-
1488           ence as the condition or test for a specific group  recursion  are  not
1489           supported.
1490    
1491           5.  Because  many  paths  through the tree may be active, the \K escape
1492           sequence, which resets the start of the match when encountered (but may
1493           be  on  some  paths  and not on others), is not supported. It causes an
1494           error if encountered.
1495    
1496           6. Callouts are supported, but the value of the  capture_top  field  is
1497           always 1, and the value of the capture_last field is always -1.
1498    
1499           7.  The  \C  escape  sequence, which (in the standard algorithm) always
1500           matches a single data unit, even in UTF-8, UTF-16 or UTF-32  modes,  is
1501           not  supported  in these modes, because the alternative algorithm moves
1502           through the subject string one character (not data unit) at a time, for
1503           all active paths through the tree.
1504    
1505           8.  Except for (*FAIL), the backtracking control verbs such as (*PRUNE)
1506           are not supported. (*FAIL) is supported, and  behaves  like  a  failing
1507           negative assertion.
1508    
1509    
1510    ADVANTAGES OF THE ALTERNATIVE ALGORITHM
1511    
1512           Using  the alternative matching algorithm provides the following advan-
1513           tages:
1514    
1515           1. All possible matches (at a single point in the subject) are automat-
1516           ically  found,  and  in particular, the longest match is found. To find
1517           more than one match using the standard algorithm, you have to do kludgy
1518           things with callouts.
1519    
1520           2.  Because  the  alternative  algorithm  scans the subject string just
1521           once, and never needs to backtrack (except for lookbehinds), it is pos-
1522           sible  to  pass  very  long subject strings to the matching function in
1523           several pieces, checking for partial matching each time. Although it is
1524           possible  to  do multi-segment matching using the standard algorithm by
1525           retaining partially matched substrings, it  is  more  complicated.  The
1526           pcrepartial  documentation  gives  details of partial matching and dis-
1527           cusses multi-segment matching.
1528    
1529    
1530    DISADVANTAGES OF THE ALTERNATIVE ALGORITHM
1531    
1532           The alternative algorithm suffers from a number of disadvantages:
1533    
1534           1. It is substantially slower than  the  standard  algorithm.  This  is
1535           partly  because  it has to search for all possible matches, but is also
1536           because it is less susceptible to optimization.
1537    
1538           2. Capturing parentheses and back references are not supported.
1539    
1540           3. Although atomic groups are supported, their use does not provide the
1541           performance advantage that it does for the standard algorithm.
1542    
1543    
1544    AUTHOR
1545    
1546           Philip Hazel
1547           University Computing Service
1548           Cambridge CB2 3QH, England.
1549    
1550    
1551    REVISION
1552    
1553           Last updated: 08 January 2012
1554           Copyright (c) 1997-2012 University of Cambridge.
1555    ------------------------------------------------------------------------------
1556    
1557    
1558    PCREAPI(3)                 Library Functions Manual                 PCREAPI(3)
1559    
1560    
1561    
1562    NAME
1563           PCRE - Perl-compatible regular expressions
1564    
1565           #include <pcre.h>
1566    
1567    
1568    PCRE NATIVE API BASIC FUNCTIONS
1569    
1570           pcre *pcre_compile(const char *pattern, int options,
1571                const char **errptr, int *erroffset,
1572                const unsigned char *tableptr);
1573    
1574           pcre *pcre_compile2(const char *pattern, int options,
1575                int *errorcodeptr,
1576                const char **errptr, int *erroffset,
1577                const unsigned char *tableptr);
1578    
1579           pcre_extra *pcre_study(const pcre *code, int options,
1580                const char **errptr);
1581    
1582           void pcre_free_study(pcre_extra *extra);
1583    
1584           int pcre_exec(const pcre *code, const pcre_extra *extra,
1585                const char *subject, int length, int startoffset,
1586                int options, int *ovector, int ovecsize);
1587    
1588           int pcre_dfa_exec(const pcre *code, const pcre_extra *extra,
1589                const char *subject, int length, int startoffset,
1590                int options, int *ovector, int ovecsize,
1591                int *workspace, int wscount);
1592    
1593    
1594    PCRE NATIVE API STRING EXTRACTION FUNCTIONS
1595    
1596           int pcre_copy_named_substring(const pcre *code,
1597                const char *subject, int *ovector,
1598                int stringcount, const char *stringname,
1599                char *buffer, int buffersize);
1600    
1601           int pcre_copy_substring(const char *subject, int *ovector,
1602                int stringcount, int stringnumber, char *buffer,
1603                int buffersize);
1604    
1605           int pcre_get_named_substring(const pcre *code,
1606                const char *subject, int *ovector,
1607                int stringcount, const char *stringname,
1608                const char **stringptr);
1609    
1610           int pcre_get_stringnumber(const pcre *code,
1611                const char *name);
1612    
1613           int pcre_get_stringtable_entries(const pcre *code,
1614                const char *name, char **first, char **last);
1615    
1616           int pcre_get_substring(const char *subject, int *ovector,
1617                int stringcount, int stringnumber,
1618                const char **stringptr);
1619    
1620           int pcre_get_substring_list(const char *subject,
1621                int *ovector, int stringcount, const char ***listptr);
1622    
1623           void pcre_free_substring(const char *stringptr);
1624    
1625           void pcre_free_substring_list(const char **stringptr);
1626    
1627    
1628    PCRE NATIVE API AUXILIARY FUNCTIONS
1629    
1630           int pcre_jit_exec(const pcre *code, const pcre_extra *extra,
1631                const char *subject, int length, int startoffset,
1632                int options, int *ovector, int ovecsize,
1633                pcre_jit_stack *jstack);
1634    
1635           pcre_jit_stack *pcre_jit_stack_alloc(int startsize, int maxsize);
1636    
1637           void pcre_jit_stack_free(pcre_jit_stack *stack);
1638    
1639           void pcre_assign_jit_stack(pcre_extra *extra,
1640                pcre_jit_callback callback, void *data);
1641    
1642           const unsigned char *pcre_maketables(void);
1643    
1644           int pcre_fullinfo(const pcre *code, const pcre_extra *extra,
1645                int what, void *where);
1646    
1647           int pcre_refcount(pcre *code, int adjust);
1648    
1649           int pcre_config(int what, void *where);
1650    
1651           const char *pcre_version(void);
1652    
1653           int pcre_pattern_to_host_byte_order(pcre *code,
1654                pcre_extra *extra, const unsigned char *tables);
1655    
1656    
1657    PCRE NATIVE API INDIRECTED FUNCTIONS
1658    
1659           void *(*pcre_malloc)(size_t);
1660    
1661           void (*pcre_free)(void *);
1662    
1663           void *(*pcre_stack_malloc)(size_t);
1664    
1665           void (*pcre_stack_free)(void *);
1666    
1667           int (*pcre_callout)(pcre_callout_block *);
1668    
1669    
1670    PCRE 8-BIT, 16-BIT, AND 32-BIT LIBRARIES
1671    
1672           As  well  as  support  for  8-bit character strings, PCRE also supports
1673           16-bit strings (from release 8.30) and  32-bit  strings  (from  release
1674           8.32),  by means of two additional libraries. They can be built as well
1675           as, or instead of, the 8-bit library. To avoid too  much  complication,
1676           this  document describes the 8-bit versions of the functions, with only
1677           occasional references to the 16-bit and 32-bit libraries.
1678    
1679           The 16-bit and 32-bit functions operate in the same way as their  8-bit
1680           counterparts;  they  just  use different data types for their arguments
1681           and results, and their names start with pcre16_ or pcre32_  instead  of
1682           pcre_.  For  every  option  that  has  UTF8  in  its name (for example,
1683           PCRE_UTF8), there are corresponding 16-bit and 32-bit names  with  UTF8
1684           replaced by UTF16 or UTF32, respectively. This facility is in fact just
1685           cosmetic; the 16-bit and 32-bit option names define the same  bit  val-
1686           ues.
1687    
1688           References to bytes and UTF-8 in this document should be read as refer-
1689           ences to 16-bit data units and UTF-16 when using the 16-bit library, or
1690           32-bit  data  units  and  UTF-32  when using the 32-bit library, unless
1691           specified otherwise.  More details of the specific differences for  the
1692           16-bit and 32-bit libraries are given in the pcre16 and pcre32 pages.
1693    
1694    
1695    PCRE API OVERVIEW
1696    
1697           PCRE has its own native API, which is described in this document. There
1698           are also some wrapper functions (for the 8-bit library only) that  cor-
1699           respond  to  the  POSIX  regular  expression  API, but they do not give
1700           access to all the functionality. They are described  in  the  pcreposix
1701           documentation.  Both  of these APIs define a set of C function calls. A
1702           C++ wrapper (again for the 8-bit library only) is also distributed with
1703           PCRE. It is documented in the pcrecpp page.
1704    
1705           The  native  API  C  function prototypes are defined in the header file
1706           pcre.h, and on Unix-like systems the (8-bit) library itself  is  called
1707           libpcre.  It  can  normally be accessed by adding -lpcre to the command
1708           for linking an application that uses PCRE. The header file defines  the
1709           macros PCRE_MAJOR and PCRE_MINOR to contain the major and minor release
1710           numbers for the library. Applications can use these to include  support
1711           for different releases of PCRE.
1712    
1713           In a Windows environment, if you want to statically link an application
1714           program against a non-dll pcre.a  file,  you  must  define  PCRE_STATIC
1715           before  including  pcre.h or pcrecpp.h, because otherwise the pcre_mal-
1716           loc()   and   pcre_free()   exported   functions   will   be   declared
1717           __declspec(dllimport), with unwanted results.
1718    
1719           The   functions   pcre_compile(),  pcre_compile2(),  pcre_study(),  and
1720           pcre_exec() are used for compiling and matching regular expressions  in
1721           a  Perl-compatible  manner. A sample program that demonstrates the sim-
1722           plest way of using them is provided in the file  called  pcredemo.c  in
1723           the PCRE source distribution. A listing of this program is given in the
1724           pcredemo documentation, and the pcresample documentation describes  how
1725           to compile and run it.
1726    
1727           Just-in-time  compiler  support is an optional feature of PCRE that can
1728           be built in appropriate hardware environments. It greatly speeds up the
1729           matching  performance  of  many  patterns.  Simple  programs can easily
1730           request that it be used if available, by  setting  an  option  that  is
1731           ignored  when  it is not relevant. More complicated programs might need
1732           to    make    use    of    the    functions     pcre_jit_stack_alloc(),
1733           pcre_jit_stack_free(),  and pcre_assign_jit_stack() in order to control
1734           the JIT code's memory usage.
1735    
1736           From release 8.32 there is also a direct interface for  JIT  execution,
1737           which  gives  improved performance. The JIT-specific functions are dis-
1738           cussed in the pcrejit documentation.
1739    
1740           A second matching function, pcre_dfa_exec(), which is not Perl-compati-
1741           ble,  is  also provided. This uses a different algorithm for the match-
1742           ing. The alternative algorithm finds all possible matches (at  a  given
1743           point  in  the  subject), and scans the subject just once (unless there
1744           are lookbehind assertions). However, this  algorithm  does  not  return
1745           captured  substrings.  A description of the two matching algorithms and
1746           their advantages and disadvantages is given in the  pcrematching  docu-
1747           mentation.
1748    
1749           In  addition  to  the  main compiling and matching functions, there are
1750           convenience functions for extracting captured substrings from a subject
1751           string that is matched by pcre_exec(). They are:
1752    
1753             pcre_copy_substring()
1754             pcre_copy_named_substring()
1755             pcre_get_substring()
1756             pcre_get_named_substring()
1757             pcre_get_substring_list()
1758             pcre_get_stringnumber()
1759             pcre_get_stringtable_entries()
1760    
1761           pcre_free_substring() and pcre_free_substring_list() are also provided,
1762           to free the memory used for extracted strings.
1763    
1764           The function pcre_maketables() is used to  build  a  set  of  character
1765           tables   in   the   current   locale  for  passing  to  pcre_compile(),
1766           pcre_exec(), or pcre_dfa_exec(). This is an optional facility  that  is
1767           provided  for  specialist  use.  Most  commonly,  no special tables are
1768           passed, in which case internal tables that are generated when  PCRE  is
1769           built are used.
1770    
1771           The  function  pcre_fullinfo()  is used to find out information about a
1772           compiled pattern. The function pcre_version() returns a  pointer  to  a
1773           string containing the version of PCRE and its date of release.
1774    
1775           The  function  pcre_refcount()  maintains  a  reference count in a data
1776           block containing a compiled pattern. This is provided for  the  benefit
1777           of object-oriented applications.
1778    
1779           The  global  variables  pcre_malloc and pcre_free initially contain the
1780           entry points of the standard malloc()  and  free()  functions,  respec-
1781           tively. PCRE calls the memory management functions via these variables,
1782           so a calling program can replace them if it  wishes  to  intercept  the
1783           calls. This should be done before calling any PCRE functions.
1784    
1785           The  global  variables  pcre_stack_malloc  and pcre_stack_free are also
1786           indirections to memory management functions.  These  special  functions
1787           are  used  only  when  PCRE is compiled to use the heap for remembering
1788           data, instead of recursive function calls, when running the pcre_exec()
1789           function.  See  the  pcrebuild  documentation  for details of how to do
1790           this. It is a non-standard way of building PCRE, for  use  in  environ-
1791           ments  that  have  limited stacks. Because of the greater use of memory
1792           management, it runs more slowly. Separate  functions  are  provided  so
1793           that  special-purpose  external  code  can  be used for this case. When
1794           used, these functions are always called in a  stack-like  manner  (last
1795           obtained,  first freed), and always for memory blocks of the same size.
1796           There is a discussion about PCRE's stack usage in the  pcrestack  docu-
1797           mentation.
1798    
1799           The global variable pcre_callout initially contains NULL. It can be set
1800           by the caller to a "callout" function, which PCRE  will  then  call  at
1801           specified  points during a matching operation. Details are given in the
1802           pcrecallout documentation.
1803    
1804    
1805    NEWLINES
1806    
1807           PCRE supports five different conventions for indicating line breaks  in
1808           strings:  a  single  CR (carriage return) character, a single LF (line-
1809           feed) character, the two-character sequence CRLF, any of the three pre-
1810           ceding,  or any Unicode newline sequence. The Unicode newline sequences
1811           are the three just mentioned, plus the single characters  VT  (vertical
1812           tab, U+000B), FF (form feed, U+000C), NEL (next line, U+0085), LS (line
1813           separator, U+2028), and PS (paragraph separator, U+2029).
1814    
1815           Each of the first three conventions is used by at least  one  operating
1816           system  as its standard newline sequence. When PCRE is built, a default
1817           can be specified.  The default default is LF, which is the  Unix  stan-
1818           dard.  When  PCRE  is run, the default can be overridden, either when a
1819           pattern is compiled, or when it is matched.
1820    
1821           At compile time, the newline convention can be specified by the options
1822           argument  of  pcre_compile(), or it can be specified by special text at
1823           the start of the pattern itself; this overrides any other settings. See
1824           the pcrepattern page for details of the special character sequences.
1825    
1826           In the PCRE documentation the word "newline" is used to mean "the char-
1827           acter or pair of characters that indicate a line break". The choice  of
1828           newline  convention  affects  the  handling of the dot, circumflex, and
1829           dollar metacharacters, the handling of #-comments in /x mode, and, when
1830           CRLF  is a recognized line ending sequence, the match position advance-
1831           ment for a non-anchored pattern. There is more detail about this in the
1832           section on pcre_exec() options below.
1833    
1834           The  choice of newline convention does not affect the interpretation of
1835           the \n or \r escape sequences, nor does  it  affect  what  \R  matches,
1836           which is controlled in a similar way, but by separate options.
1837    
1838    
1839    MULTITHREADING
1840    
1841           The  PCRE  functions  can be used in multi-threading applications, with
1842           the  proviso  that  the  memory  management  functions  pointed  to  by
1843           pcre_malloc, pcre_free, pcre_stack_malloc, and pcre_stack_free, and the
1844           callout function pointed to by pcre_callout, are shared by all threads.
1845    
1846           The compiled form of a regular expression is not altered during  match-
1847           ing, so the same compiled pattern can safely be used by several threads
1848           at once.
1849    
1850           If the just-in-time optimization feature is being used, it needs  sepa-
1851           rate  memory stack areas for each thread. See the pcrejit documentation
1852           for more details.
1853    
1854    
1855    SAVING PRECOMPILED PATTERNS FOR LATER USE
1856    
1857           The compiled form of a regular expression can be saved and re-used at a
1858           later  time,  possibly by a different program, and even on a host other
1859           than the one on which  it  was  compiled.  Details  are  given  in  the
1860           pcreprecompile  documentation,  which  includes  a  description  of the
1861           pcre_pattern_to_host_byte_order() function. However, compiling a  regu-
1862           lar  expression  with one version of PCRE for use with a different ver-
1863           sion is not guaranteed to work and may cause crashes.
1864    
1865    
1866    CHECKING BUILD-TIME OPTIONS
1867    
1868           int pcre_config(int what, void *where);
1869    
1870           The function pcre_config() makes it possible for a PCRE client to  dis-
1871           cover which optional features have been compiled into the PCRE library.
1872           The pcrebuild documentation has more details about these optional  fea-
1873           tures.
1874    
1875           The  first  argument  for pcre_config() is an integer, specifying which
1876           information is required; the second argument is a pointer to a variable
1877           into  which  the  information  is placed. The returned value is zero on
1878           success, or the negative error code PCRE_ERROR_BADOPTION if  the  value
1879           in  the  first argument is not recognized. The following information is
1880           available:
1881    
1882             PCRE_CONFIG_UTF8
1883    
1884           The output is an integer that is set to one if UTF-8 support is  avail-
1885           able;  otherwise it is set to zero. This value should normally be given
1886           to the 8-bit version of this function, pcre_config(). If it is given to
1887           the   16-bit  or  32-bit  version  of  this  function,  the  result  is
1888           PCRE_ERROR_BADOPTION.
1889    
1890             PCRE_CONFIG_UTF16
1891    
1892           The output is an integer that is set to one if UTF-16 support is avail-
1893           able;  otherwise it is set to zero. This value should normally be given
1894           to the 16-bit version of this function, pcre16_config(). If it is given
1895           to  the  8-bit  or  32-bit  version  of  this  function,  the result is
1896           PCRE_ERROR_BADOPTION.
1897    
1898             PCRE_CONFIG_UTF32
1899    
1900           The output is an integer that is set to one if UTF-32 support is avail-
1901           able;  otherwise it is set to zero. This value should normally be given
1902           to the 32-bit version of this function, pcre32_config(). If it is given
1903           to  the  8-bit  or  16-bit  version  of  this  function,  the result is
1904           PCRE_ERROR_BADOPTION.
1905    
1906             PCRE_CONFIG_UNICODE_PROPERTIES
1907    
1908           The output is an integer that is set to  one  if  support  for  Unicode
1909           character properties is available; otherwise it is set to zero.
1910    
1911             PCRE_CONFIG_JIT
1912    
1913           The output is an integer that is set to one if support for just-in-time
1914           compiling is available; otherwise it is set to zero.
1915    
1916             PCRE_CONFIG_JITTARGET
1917    
1918           The output is a pointer to a zero-terminated "const char *" string.  If
1919           JIT support is available, the string contains the name of the architec-
1920           ture for which the JIT compiler is configured, for example  "x86  32bit
1921           (little  endian  +  unaligned)".  If  JIT support is not available, the
1922           result is NULL.
1923    
1924             PCRE_CONFIG_NEWLINE
1925    
1926           The output is an integer whose value specifies  the  default  character
1927           sequence  that  is recognized as meaning "newline". The values that are
1928           supported in ASCII/Unicode environments are: 10 for LF, 13 for CR, 3338
1929           for  CRLF,  -2 for ANYCRLF, and -1 for ANY. In EBCDIC environments, CR,
1930           ANYCRLF, and ANY yield the same values. However, the value  for  LF  is
1931           normally  21, though some EBCDIC environments use 37. The corresponding
1932           values for CRLF are 3349 and 3365. The default should  normally  corre-
1933           spond to the standard sequence for your operating system.
1934    
1935             PCRE_CONFIG_BSR
1936    
1937           The output is an integer whose value indicates what character sequences
1938           the \R escape sequence matches by default. A value of 0 means  that  \R
1939           matches  any  Unicode  line ending sequence; a value of 1 means that \R
1940           matches only CR, LF, or CRLF. The default can be overridden when a pat-
1941           tern is compiled or matched.
1942    
1943             PCRE_CONFIG_LINK_SIZE
1944    
1945           The  output  is  an  integer that contains the number of bytes used for
1946           internal  linkage  in  compiled  regular  expressions.  For  the  8-bit
1947           library, the value can be 2, 3, or 4. For the 16-bit library, the value
1948           is either 2 or 4 and is  still  a  number  of  bytes.  For  the  32-bit
1949           library, the value is either 2 or 4 and is still a number of bytes. The
1950           default value of 2 is sufficient for all but the most massive patterns,
1951           since  it  allows  the compiled pattern to be up to 64K in size. Larger
1952           values allow larger regular expressions to be compiled, at the  expense
1953           of slower matching.
1954    
1955             PCRE_CONFIG_POSIX_MALLOC_THRESHOLD
1956    
1957           The  output  is  an integer that contains the threshold above which the
1958           POSIX interface uses malloc() for output vectors. Further  details  are
1959           given in the pcreposix documentation.
1960    
1961             PCRE_CONFIG_MATCH_LIMIT
1962    
1963           The  output is a long integer that gives the default limit for the num-
1964           ber of internal matching function calls  in  a  pcre_exec()  execution.
1965           Further details are given with pcre_exec() below.
1966    
1967             PCRE_CONFIG_MATCH_LIMIT_RECURSION
1968    
1969           The output is a long integer that gives the default limit for the depth
1970           of  recursion  when  calling  the  internal  matching  function  in   a
1971           pcre_exec()  execution.  Further  details  are  given  with pcre_exec()
1972           below.
1973    
1974             PCRE_CONFIG_STACKRECURSE
1975    
1976           The output is an integer that is set to one if internal recursion  when
1977           running pcre_exec() is implemented by recursive function calls that use
1978           the stack to remember their state. This is the usual way that  PCRE  is
1979           compiled. The output is zero if PCRE was compiled to use blocks of data
1980           on the  heap  instead  of  recursive  function  calls.  In  this  case,
1981           pcre_stack_malloc  and  pcre_stack_free  are  called  to  manage memory
1982           blocks on the heap, thus avoiding the use of the stack.
1983    
1984    
1985    COMPILING A PATTERN
1986    
1987           pcre *pcre_compile(const char *pattern, int options,
1988                const char **errptr, int *erroffset,
1989                const unsigned char *tableptr);
1990    
1991           pcre *pcre_compile2(const char *pattern, int options,
1992                int *errorcodeptr,
1993                const char **errptr, int *erroffset,
1994                const unsigned char *tableptr);
1995    
1996           Either of the functions pcre_compile() or pcre_compile2() can be called
1997           to compile a pattern into an internal form. The only difference between
1998           the two interfaces is that pcre_compile2() has an additional  argument,
1999           errorcodeptr,  via  which  a  numerical  error code can be returned. To
2000           avoid too much repetition, we refer just to pcre_compile()  below,  but
2001           the information applies equally to pcre_compile2().
2002    
2003           The pattern is a C string terminated by a binary zero, and is passed in
2004           the pattern argument. A pointer to a single block  of  memory  that  is
2005           obtained  via  pcre_malloc is returned. This contains the compiled code
2006           and related data. The pcre type is defined for the returned block; this
2007           is a typedef for a structure whose contents are not externally defined.
2008           It is up to the caller to free the memory (via pcre_free) when it is no
2009           longer required.
2010    
2011           Although  the compiled code of a PCRE regex is relocatable, that is, it
2012           does not depend on memory location, the complete pcre data block is not
2013           fully  relocatable, because it may contain a copy of the tableptr argu-
2014           ment, which is an address (see below).
2015    
2016           The options argument contains various bit settings that affect the com-
2017           pilation.  It  should be zero if no options are required. The available
2018           options are described below. Some of them (in  particular,  those  that
2019           are  compatible with Perl, but some others as well) can also be set and
2020           unset from within the pattern (see  the  detailed  description  in  the
2021           pcrepattern  documentation). For those options that can be different in
2022           different parts of the pattern, the contents of  the  options  argument
2023           specifies their settings at the start of compilation and execution. The
2024           PCRE_ANCHORED, PCRE_BSR_xxx, PCRE_NEWLINE_xxx, PCRE_NO_UTF8_CHECK,  and
2025           PCRE_NO_START_OPTIMIZE  options  can  be set at the time of matching as
2026           well as at compile time.
2027    
2028           If errptr is NULL, pcre_compile() returns NULL immediately.  Otherwise,
2029           if  compilation  of  a  pattern fails, pcre_compile() returns NULL, and
2030           sets the variable pointed to by errptr to point to a textual error mes-
2031           sage. This is a static string that is part of the library. You must not
2032           try to free it. Normally, the offset from the start of the  pattern  to
2033           the data unit that was being processed when the error was discovered is
2034           placed in the variable pointed to by erroffset, which must not be  NULL
2035           (if  it is, an immediate error is given). However, for an invalid UTF-8
2036           or UTF-16 string, the offset is that of the  first  data  unit  of  the
2037           failing character.
2038    
2039           Some  errors are not detected until the whole pattern has been scanned;
2040           in these cases, the offset passed back is the length  of  the  pattern.
2041           Note  that  the  offset is in data units, not characters, even in a UTF
2042           mode. It may sometimes point into the middle of a UTF-8 or UTF-16 char-
2043           acter.
2044    
2045           If  pcre_compile2()  is  used instead of pcre_compile(), and the error-
2046           codeptr argument is not NULL, a non-zero error code number is  returned
2047           via  this argument in the event of an error. This is in addition to the
2048           textual error message. Error codes and messages are listed below.
2049    
2050           If the final argument, tableptr, is NULL, PCRE uses a  default  set  of
2051           character  tables  that  are  built  when  PCRE  is compiled, using the
2052           default C locale. Otherwise, tableptr must be an address  that  is  the
2053           result  of  a  call to pcre_maketables(). This value is stored with the
2054           compiled pattern, and used again by pcre_exec(), unless  another  table
2055           pointer is passed to it. For more discussion, see the section on locale
2056           support below.
2057    
2058           This code fragment shows a typical straightforward  call  to  pcre_com-
2059           pile():
2060    
2061             pcre *re;
2062             const char *error;
2063             int erroffset;
2064             re = pcre_compile(
2065               "^A.*Z",          /* the pattern */
2066               0,                /* default options */
2067               &error,           /* for error message */
2068               &erroffset,       /* for error offset */
2069               NULL);            /* use default character tables */
2070    
2071           The  following  names  for option bits are defined in the pcre.h header
2072           file:
2073    
2074             PCRE_ANCHORED
2075    
2076           If this bit is set, the pattern is forced to be "anchored", that is, it
2077           is  constrained to match only at the first matching point in the string
2078           that is being searched (the "subject string"). This effect can also  be
2079           achieved  by appropriate constructs in the pattern itself, which is the
2080           only way to do it in Perl.
2081    
2082             PCRE_AUTO_CALLOUT
2083    
2084           If this bit is set, pcre_compile() automatically inserts callout items,
2085           all  with  number  255, before each pattern item. For discussion of the
2086           callout facility, see the pcrecallout documentation.
2087    
2088             PCRE_BSR_ANYCRLF
2089             PCRE_BSR_UNICODE
2090    
2091           These options (which are mutually exclusive) control what the \R escape
2092           sequence  matches.  The choice is either to match only CR, LF, or CRLF,
2093           or to match any Unicode newline sequence. The default is specified when
2094           PCRE is built. It can be overridden from within the pattern, or by set-
2095           ting an option when a compiled pattern is matched.
2096    
2097             PCRE_CASELESS
2098    
2099           If this bit is set, letters in the pattern match both upper  and  lower
2100           case  letters.  It  is  equivalent  to  Perl's /i option, and it can be
2101           changed within a pattern by a (?i) option setting. In UTF-8 mode,  PCRE
2102           always  understands the concept of case for characters whose values are
2103           less than 128, so caseless matching is always possible. For  characters
2104           with  higher  values,  the concept of case is supported if PCRE is com-
2105           piled with Unicode property support, but not otherwise. If you want  to
2106           use  caseless  matching  for  characters 128 and above, you must ensure
2107           that PCRE is compiled with Unicode property support  as  well  as  with
2108           UTF-8 support.
2109    
2110             PCRE_DOLLAR_ENDONLY
2111    
2112           If  this bit is set, a dollar metacharacter in the pattern matches only
2113           at the end of the subject string. Without this option,  a  dollar  also
2114           matches  immediately before a newline at the end of the string (but not
2115           before any other newlines). The PCRE_DOLLAR_ENDONLY option  is  ignored
2116           if  PCRE_MULTILINE  is  set.   There is no equivalent to this option in
2117           Perl, and no way to set it within a pattern.
2118    
2119             PCRE_DOTALL
2120    
2121           If this bit is set, a dot metacharacter in the pattern matches a  char-
2122           acter of any value, including one that indicates a newline. However, it
2123           only ever matches one character, even if newlines are  coded  as  CRLF.
2124           Without  this option, a dot does not match when the current position is
2125           at a newline. This option is equivalent to Perl's /s option, and it can
2126           be  changed within a pattern by a (?s) option setting. A negative class
2127           such as [^a] always matches newline characters, independent of the set-
2128           ting of this option.
2129    
2130             PCRE_DUPNAMES
2131    
2132           If  this  bit is set, names used to identify capturing subpatterns need
2133           not be unique. This can be helpful for certain types of pattern when it
2134           is  known  that  only  one instance of the named subpattern can ever be
2135           matched. There are more details of named subpatterns  below;  see  also
2136           the pcrepattern documentation.
2137    
2138             PCRE_EXTENDED
2139    
2140           If  this  bit  is  set,  white space data characters in the pattern are
2141           totally ignored except when escaped or inside a character class.  White
2142           space does not include the VT character (code 11). In addition, charac-
2143           ters between an unescaped # outside a character class and the next new-
2144           line,  inclusive,  are  also  ignored.  This is equivalent to Perl's /x
2145           option, and it can be changed within a pattern by a  (?x)  option  set-
2146           ting.
2147    
2148           Which  characters  are  interpreted  as  newlines  is controlled by the
2149           options passed to pcre_compile() or by a special sequence at the  start
2150           of  the  pattern, as described in the section entitled "Newline conven-
2151           tions" in the pcrepattern documentation. Note that the end of this type
2152           of  comment  is  a  literal  newline  sequence  in  the pattern; escape
2153           sequences that happen to represent a newline do not count.
2154    
2155           This option makes it possible to include  comments  inside  complicated
2156           patterns.   Note,  however,  that this applies only to data characters.
2157           White space  characters  may  never  appear  within  special  character
2158           sequences in a pattern, for example within the sequence (?( that intro-
2159           duces a conditional subpattern.
2160    
2161             PCRE_EXTRA
2162    
2163           This option was invented in order to turn on  additional  functionality
2164           of  PCRE  that  is  incompatible with Perl, but it is currently of very
2165           little use. When set, any backslash in a pattern that is followed by  a
2166           letter  that  has  no  special  meaning causes an error, thus reserving
2167           these combinations for future expansion. By  default,  as  in  Perl,  a
2168           backslash  followed by a letter with no special meaning is treated as a
2169           literal. (Perl can, however, be persuaded to give an error for this, by
2170           running  it with the -w option.) There are at present no other features
2171           controlled by this option. It can also be set by a (?X) option  setting
2172           within a pattern.
2173    
2174             PCRE_FIRSTLINE
2175    
2176           If  this  option  is  set,  an  unanchored pattern is required to match
2177           before or at the first  newline  in  the  subject  string,  though  the
2178           matched text may continue over the newline.
2179    
2180             PCRE_JAVASCRIPT_COMPAT
2181    
2182           If this option is set, PCRE's behaviour is changed in some ways so that
2183           it is compatible with JavaScript rather than Perl. The changes  are  as
2184           follows:
2185    
2186           (1)  A  lone  closing square bracket in a pattern causes a compile-time
2187           error, because this is illegal in JavaScript (by default it is  treated
2188           as a data character). Thus, the pattern AB]CD becomes illegal when this
2189           option is set.
2190    
2191           (2) At run time, a back reference to an unset subpattern group  matches
2192           an  empty  string (by default this causes the current matching alterna-
2193           tive to fail). A pattern such as (\1)(a) succeeds when this  option  is
2194           set  (assuming  it can find an "a" in the subject), whereas it fails by
2195           default, for Perl compatibility.
2196    
2197           (3) \U matches an upper case "U" character; by default \U causes a com-
2198           pile time error (Perl uses \U to upper case subsequent characters).
2199    
2200           (4) \u matches a lower case "u" character unless it is followed by four
2201           hexadecimal digits, in which case the hexadecimal  number  defines  the
2202           code  point  to match. By default, \u causes a compile time error (Perl
2203           uses it to upper case the following character).
2204    
2205           (5) \x matches a lower case "x" character unless it is followed by  two
2206           hexadecimal  digits,  in  which case the hexadecimal number defines the
2207           code point to match. By default, as in Perl, a  hexadecimal  number  is
2208           always expected after \x, but it may have zero, one, or two digits (so,
2209           for example, \xz matches a binary zero character followed by z).
2210    
2211             PCRE_MULTILINE
2212    
2213           By default, for the purposes of matching "start of line"  and  "end  of
2214           line", PCRE treats the subject string as consisting of a single line of
2215           characters, even if it actually contains newlines. The "start of  line"
2216           metacharacter (^) matches only at the start of the string, and the "end
2217           of line" metacharacter ($) matches only at the end of  the  string,  or
2218           before  a terminating newline (except when PCRE_DOLLAR_ENDONLY is set).
2219           Note, however, that unless PCRE_DOTALL  is  set,  the  "any  character"
2220           metacharacter  (.)  does not match at a newline. This behaviour (for ^,
2221           $, and dot) is the same as Perl.
2222    
2223           When PCRE_MULTILINE it is set, the "start of line" and  "end  of  line"
2224           constructs  match  immediately following or immediately before internal
2225           newlines in the subject string, respectively, as well as  at  the  very
2226           start  and  end.  This is equivalent to Perl's /m option, and it can be
2227           changed within a pattern by a (?m) option setting. If there are no new-
2228           lines  in  a  subject string, or no occurrences of ^ or $ in a pattern,
2229           setting PCRE_MULTILINE has no effect.
2230    
2231             PCRE_NEVER_UTF
2232    
2233           This option locks out interpretation of the pattern as UTF-8 (or UTF-16
2234           or  UTF-32  in the 16-bit and 32-bit libraries). In particular, it pre-
2235           vents the creator of the pattern from switching to  UTF  interpretation
2236           by starting the pattern with (*UTF). This may be useful in applications
2237           that  process  patterns  from  external  sources.  The  combination  of
2238           PCRE_UTF8 and PCRE_NEVER_UTF also causes an error.
2239    
2240             PCRE_NEWLINE_CR
2241             PCRE_NEWLINE_LF
2242             PCRE_NEWLINE_CRLF
2243             PCRE_NEWLINE_ANYCRLF
2244             PCRE_NEWLINE_ANY
2245    
2246           These  options  override the default newline definition that was chosen
2247           when PCRE was built. Setting the first or the second specifies  that  a
2248           newline  is  indicated  by a single character (CR or LF, respectively).
2249           Setting PCRE_NEWLINE_CRLF specifies that a newline is indicated by  the
2250           two-character  CRLF  sequence.  Setting  PCRE_NEWLINE_ANYCRLF specifies
2251           that any of the three preceding sequences should be recognized. Setting
2252           PCRE_NEWLINE_ANY  specifies that any Unicode newline sequence should be
2253           recognized.
2254    
2255           In an ASCII/Unicode environment, the Unicode newline sequences are  the
2256           three  just  mentioned,  plus  the  single characters VT (vertical tab,
2257           U+000B), FF (form feed, U+000C), NEL (next line, U+0085), LS (line sep-
2258           arator,  U+2028),  and  PS (paragraph separator, U+2029). For the 8-bit
2259           library, the last two are recognized only in UTF-8 mode.
2260    
2261           When PCRE is compiled to run in an EBCDIC (mainframe) environment,  the
2262           code for CR is 0x0d, the same as ASCII. However, the character code for
2263           LF is normally 0x15, though in some EBCDIC environments 0x25  is  used.
2264           Whichever  of  these  is  not LF is made to correspond to Unicode's NEL
2265           character. EBCDIC codes are all less than 256. For  more  details,  see
2266           the pcrebuild documentation.
2267    
2268           The  newline  setting  in  the  options  word  uses three bits that are
2269           treated as a number, giving eight possibilities. Currently only six are
2270           used  (default  plus the five values above). This means that if you set
2271           more than one newline option, the combination may or may not be  sensi-
2272           ble. For example, PCRE_NEWLINE_CR with PCRE_NEWLINE_LF is equivalent to
2273           PCRE_NEWLINE_CRLF, but other combinations may yield unused numbers  and
2274           cause an error.
2275    
2276           The  only  time  that a line break in a pattern is specially recognized
2277           when compiling is when PCRE_EXTENDED is set. CR and LF are white  space
2278           characters,  and so are ignored in this mode. Also, an unescaped # out-
2279           side a character class indicates a comment that lasts until  after  the
2280           next  line break sequence. In other circumstances, line break sequences
2281           in patterns are treated as literal data.
2282    
2283           The newline option that is set at compile time becomes the default that
2284           is used for pcre_exec() and pcre_dfa_exec(), but it can be overridden.
2285    
2286             PCRE_NO_AUTO_CAPTURE
2287    
2288           If this option is set, it disables the use of numbered capturing paren-
2289           theses in the pattern. Any opening parenthesis that is not followed  by
2290           ?  behaves as if it were followed by ?: but named parentheses can still
2291           be used for capturing (and they acquire  numbers  in  the  usual  way).
2292           There is no equivalent of this option in Perl.
2293    
2294             PCRE_NO_START_OPTIMIZE
2295    
2296           This  is an option that acts at matching time; that is, it is really an
2297           option for pcre_exec() or pcre_dfa_exec(). If  it  is  set  at  compile
2298           time,  it is remembered with the compiled pattern and assumed at match-
2299           ing time. This is necessary if you want to use JIT  execution,  because
2300           the  JIT  compiler needs to know whether or not this option is set. For
2301           details see the discussion of PCRE_NO_START_OPTIMIZE below.
2302    
2303             PCRE_UCP
2304    
2305           This option changes the way PCRE processes \B, \b, \D, \d, \S, \s,  \W,
2306           \w,  and  some  of  the POSIX character classes. By default, only ASCII
2307           characters are recognized, but if PCRE_UCP is set,  Unicode  properties
2308           are  used instead to classify characters. More details are given in the
2309           section on generic character types in the pcrepattern page. If you  set
2310           PCRE_UCP,  matching  one of the items it affects takes much longer. The
2311           option is available only if PCRE has been compiled with  Unicode  prop-
2312           erty support.
2313    
2314             PCRE_UNGREEDY
2315    
2316           This  option  inverts  the "greediness" of the quantifiers so that they
2317           are not greedy by default, but become greedy if followed by "?". It  is
2318           not  compatible  with Perl. It can also be set by a (?U) option setting
2319           within the pattern.
2320    
2321             PCRE_UTF8
2322    
2323           This option causes PCRE to regard both the pattern and the  subject  as
2324           strings of UTF-8 characters instead of single-byte strings. However, it
2325           is available only when PCRE is built to include UTF  support.  If  not,
2326           the  use  of  this option provokes an error. Details of how this option
2327           changes the behaviour of PCRE are given in the pcreunicode page.
2328    
2329             PCRE_NO_UTF8_CHECK
2330    
2331           When PCRE_UTF8 is set, the validity of the pattern as a UTF-8 string is
2332           automatically  checked.  There  is  a  discussion about the validity of
2333           UTF-8 strings in the pcreunicode page. If an invalid UTF-8 sequence  is
2334           found,  pcre_compile()  returns an error. If you already know that your
2335           pattern is valid, and you want to skip this check for performance  rea-
2336           sons,  you  can set the PCRE_NO_UTF8_CHECK option.  When it is set, the
2337           effect of passing an invalid UTF-8 string as a pattern is undefined. It
2338           may  cause  your  program  to  crash. Note that this option can also be
2339           passed to pcre_exec() and pcre_dfa_exec(),  to  suppress  the  validity
2340           checking  of  subject strings only. If the same string is being matched
2341           many times, the option can be safely set for the second and  subsequent
2342           matchings to improve performance.
2343    
2344    
2345    COMPILATION ERROR CODES
2346    
2347           The  following  table  lists  the  error  codes than may be returned by
2348           pcre_compile2(), along with the error messages that may be returned  by
2349           both  compiling  functions.  Note  that error messages are always 8-bit
2350           ASCII strings, even in 16-bit or 32-bit mode. As  PCRE  has  developed,
2351           some  error codes have fallen out of use. To avoid confusion, they have
2352           not been re-used.
2353    
2354              0  no error
2355              1  \ at end of pattern
2356              2  \c at end of pattern
2357              3  unrecognized character follows \
2358              4  numbers out of order in {} quantifier
2359              5  number too big in {} quantifier
2360              6  missing terminating ] for character class
2361              7  invalid escape sequence in character class
2362              8  range out of order in character class
2363              9  nothing to repeat
2364             10  [this code is not in use]
2365             11  internal error: unexpected repeat
2366             12  unrecognized character after (? or (?-
2367             13  POSIX named classes are supported only within a class
2368             14  missing )
2369             15  reference to non-existent subpattern
2370             16  erroffset passed as NULL
2371             17  unknown option bit(s) set
2372             18  missing ) after comment
2373             19  [this code is not in use]
2374             20  regular expression is too large
2375             21  failed to get memory
2376             22  unmatched parentheses
2377             23  internal error: code overflow
2378             24  unrecognized character after (?<
2379             25  lookbehind assertion is not fixed length
2380             26  malformed number or name after (?(
2381             27  conditional group contains more than two branches
2382             28  assertion expected after (?(
2383             29  (?R or (?[+-]digits must be followed by )
2384             30  unknown POSIX class name
2385             31  POSIX collating elements are not supported
2386             32  this version of PCRE is compiled without UTF support
2387             33  [this code is not in use]
2388             34  character value in \x{...} sequence is too large
2389             35  invalid condition (?(0)
2390             36  \C not allowed in lookbehind assertion
2391             37  PCRE does not support \L, \l, \N{name}, \U, or \u
2392             38  number after (?C is > 255
2393             39  closing ) for (?C expected
2394             40  recursive call could loop indefinitely
2395             41  unrecognized character after (?P
2396             42  syntax error in subpattern name (missing terminator)
2397             43  two named subpatterns have the same name
2398             44  invalid UTF-8 string (specifically UTF-8)
2399             45  support for \P, \p, and \X has not been compiled
2400             46  malformed \P or \p sequence
2401             47  unknown property name after \P or \p
2402             48  subpattern name is too long (maximum 32 characters)
2403             49  too many named subpatterns (maximum 10000)
2404             50  [this code is not in use]
2405             51  octal value is greater than \377 in 8-bit non-UTF-8 mode
2406             52  internal error: overran compiling workspace
2407             53  internal error: previously-checked referenced subpattern
2408                   not found
2409             54  DEFINE group contains more than one branch
2410             55  repeating a DEFINE group is not allowed
2411             56  inconsistent NEWLINE options
2412             57  \g is not followed by a braced, angle-bracketed, or quoted
2413                   name/number or by a plain number
2414             58  a numbered reference must not be zero
2415             59  an argument is not allowed for (*ACCEPT), (*FAIL), or (*COMMIT)
2416             60  (*VERB) not recognized or malformed
2417             61  number is too big
2418             62  subpattern name expected
2419             63  digit expected after (?+
2420             64  ] is an invalid data character in JavaScript compatibility mode
2421             65  different names for subpatterns of the same number are
2422                   not allowed
2423             66  (*MARK) must have an argument
2424             67  this version of PCRE is not compiled with Unicode property
2425                   support
2426             68  \c must be followed by an ASCII character
2427             69  \k is not followed by a braced, angle-bracketed, or quoted name
2428             70  internal error: unknown opcode in find_fixedlength()
2429             71  \N is not supported in a class
2430             72  too many forward references
2431             73  disallowed Unicode code point (>= 0xd800 && <= 0xdfff)
2432             74  invalid UTF-16 string (specifically UTF-16)
2433             75  name is too long in (*MARK), (*PRUNE), (*SKIP), or (*THEN)
2434             76  character value in \u.... sequence is too large
2435             77  invalid UTF-32 string (specifically UTF-32)
2436    
2437           The numbers 32 and 10000 in errors 48 and 49  are  defaults;  different
2438           values may be used if the limits were changed when PCRE was built.
2439    
2440    
2441    STUDYING A PATTERN
2442    
2443           pcre_extra *pcre_study(const pcre *code, int options
2444                const char **errptr);
2445    
2446           If  a  compiled  pattern is going to be used several times, it is worth
2447           spending more time analyzing it in order to speed up the time taken for
2448           matching.  The function pcre_study() takes a pointer to a compiled pat-
2449           tern as its first argument. If studying the pattern produces additional
2450           information  that  will  help speed up matching, pcre_study() returns a
2451           pointer to a pcre_extra block, in which the study_data field points  to
2452           the results of the study.
2453    
2454           The  returned  value  from  pcre_study()  can  be  passed  directly  to
2455           pcre_exec() or pcre_dfa_exec(). However, a pcre_extra block  also  con-
2456           tains  other  fields  that can be set by the caller before the block is
2457           passed; these are described below in the section on matching a pattern.
2458    
2459           If studying the  pattern  does  not  produce  any  useful  information,
2460           pcre_study()  returns  NULL  by  default.  In that circumstance, if the
2461           calling program wants to pass any of the other fields to pcre_exec() or
2462           pcre_dfa_exec(),  it  must set up its own pcre_extra block. However, if
2463           pcre_study() is called  with  the  PCRE_STUDY_EXTRA_NEEDED  option,  it
2464           returns a pcre_extra block even if studying did not find any additional
2465           information. It may still return NULL, however, if an error  occurs  in
2466           pcre_study().
2467    
2468           The  second  argument  of  pcre_study() contains option bits. There are
2469           three further options in addition to PCRE_STUDY_EXTRA_NEEDED:
2470    
2471             PCRE_STUDY_JIT_COMPILE
2472             PCRE_STUDY_JIT_PARTIAL_HARD_COMPILE
2473             PCRE_STUDY_JIT_PARTIAL_SOFT_COMPILE
2474    
2475           If any of these are set, and the just-in-time  compiler  is  available,
2476           the  pattern  is  further compiled into machine code that executes much
2477           faster than the pcre_exec()  interpretive  matching  function.  If  the
2478           just-in-time  compiler is not available, these options are ignored. All
2479           undefined bits in the options argument must be zero.
2480    
2481           JIT compilation is a heavyweight optimization. It can  take  some  time
2482           for  patterns  to  be analyzed, and for one-off matches and simple pat-
2483           terns the benefit of faster execution might be offset by a much  slower
2484           study time.  Not all patterns can be optimized by the JIT compiler. For
2485           those that cannot be handled, matching automatically falls back to  the
2486           pcre_exec()  interpreter.  For more details, see the pcrejit documenta-
2487           tion.
2488    
2489           The third argument for pcre_study() is a pointer for an error  message.
2490           If  studying  succeeds  (even  if no data is returned), the variable it
2491           points to is set to NULL. Otherwise it is set to  point  to  a  textual
2492           error message. This is a static string that is part of the library. You
2493           must not try to free it. You should test the  error  pointer  for  NULL
2494           after calling pcre_study(), to be sure that it has run successfully.
2495    
2496           When  you are finished with a pattern, you can free the memory used for
2497           the study data by calling pcre_free_study(). This function was added to
2498           the  API  for  release  8.20. For earlier versions, the memory could be
2499           freed with pcre_free(), just like the pattern itself. This  will  still
2500           work  in  cases where JIT optimization is not used, but it is advisable
2501           to change to the new function when convenient.
2502    
2503           This is a typical way in which pcre_study() is used (except that  in  a
2504           real application there should be tests for errors):
2505    
2506             int rc;
2507             pcre *re;
2508             pcre_extra *sd;
2509             re = pcre_compile("pattern", 0, &error, &erroroffset, NULL);
2510             sd = pcre_study(
2511               re,             /* result of pcre_compile() */
2512               0,              /* no options */
2513               &error);        /* set to NULL or points to a message */
2514             rc = pcre_exec(   /* see below for details of pcre_exec() options */
2515               re, sd, "subject", 7, 0, 0, ovector, 30);
2516             ...
2517             pcre_free_study(sd);
2518             pcre_free(re);
2519    
2520           Studying a pattern does two things: first, a lower bound for the length
2521           of subject string that is needed to match the pattern is computed. This
2522           does not mean that there are any strings of that length that match, but
2523           it does guarantee that no shorter strings match. The value is  used  to
2524           avoid wasting time by trying to match strings that are shorter than the
2525           lower bound. You can find out the value in a calling  program  via  the
2526           pcre_fullinfo() function.
2527    
2528           Studying a pattern is also useful for non-anchored patterns that do not
2529           have a single fixed starting character. A bitmap of  possible  starting
2530           bytes  is  created. This speeds up finding a position in the subject at
2531           which to start matching. (In 16-bit mode, the bitmap is used for 16-bit
2532           values  less  than  256.  In 32-bit mode, the bitmap is used for 32-bit
2533           values less than 256.)
2534    
2535           These two optimizations apply to both pcre_exec() and  pcre_dfa_exec(),
2536           and  the  information  is also used by the JIT compiler.  The optimiza-
2537           tions can be disabled by  setting  the  PCRE_NO_START_OPTIMIZE  option.
2538           You  might want to do this if your pattern contains callouts or (*MARK)
2539           and you want to make use of these facilities in  cases  where  matching
2540           fails.
2541    
2542           PCRE_NO_START_OPTIMIZE  can be specified at either compile time or exe-
2543           cution  time.  However,  if   PCRE_NO_START_OPTIMIZE   is   passed   to
2544           pcre_exec(), (that is, after any JIT compilation has happened) JIT exe-
2545           cution is disabled. For JIT execution to work with  PCRE_NO_START_OPTI-
2546           MIZE, the option must be set at compile time.
2547    
2548           There is a longer discussion of PCRE_NO_START_OPTIMIZE below.
2549    
2550    
2551    LOCALE SUPPORT
2552    
2553           PCRE  handles  caseless matching, and determines whether characters are
2554           letters, digits, or whatever, by reference to a set of tables,  indexed
2555           by  character  value.  When running in UTF-8 mode, this applies only to
2556           characters with codes less than 128. By  default,  higher-valued  codes
2557           never match escapes such as \w or \d, but they can be tested with \p if
2558           PCRE is built with Unicode character property  support.  Alternatively,
2559           the  PCRE_UCP  option  can  be  set at compile time; this causes \w and
2560           friends to use Unicode property support instead of built-in tables. The
2561           use of locales with Unicode is discouraged. If you are handling charac-
2562           ters with codes greater than 128, you should either use UTF-8 and  Uni-
2563           code, or use locales, but not try to mix the two.
2564    
2565           PCRE  contains  an  internal set of tables that are used when the final
2566           argument of pcre_compile() is  NULL.  These  are  sufficient  for  many
2567           applications.  Normally, the internal tables recognize only ASCII char-
2568           acters. However, when PCRE is built, it is possible to cause the inter-
2569           nal tables to be rebuilt in the default "C" locale of the local system,
2570           which may cause them to be different.
2571    
2572           The internal tables can always be overridden by tables supplied by  the
2573           application that calls PCRE. These may be created in a different locale
2574           from the default. As more and more applications change  to  using  Uni-
2575           code, the need for this locale support is expected to die away.
2576    
2577           External  tables  are  built by calling the pcre_maketables() function,
2578           which has no arguments, in the relevant locale. The result can then  be
2579           passed  to  pcre_compile()  or  pcre_exec()  as often as necessary. For
2580           example, to build and use tables that are appropriate  for  the  French
2581           locale  (where  accented  characters  with  values greater than 128 are
2582           treated as letters), the following code could be used:
2583    
2584             setlocale(LC_CTYPE, "fr_FR");
2585             tables = pcre_maketables();
2586             re = pcre_compile(..., tables);
2587    
2588           The locale name "fr_FR" is used on Linux and other  Unix-like  systems;
2589           if you are using Windows, the name for the French locale is "french".
2590    
2591           When  pcre_maketables()  runs,  the  tables are built in memory that is
2592           obtained via pcre_malloc. It is the caller's responsibility  to  ensure
2593           that  the memory containing the tables remains available for as long as
2594           it is needed.
2595    
2596           The pointer that is passed to pcre_compile() is saved with the compiled
2597           pattern,  and the same tables are used via this pointer by pcre_study()
2598           and normally also by pcre_exec(). Thus, by default, for any single pat-
2599           tern, compilation, studying and matching all happen in the same locale,
2600           but different patterns can be compiled in different locales.
2601    
2602           It is possible to pass a table pointer or NULL (indicating the  use  of
2603           the  internal  tables)  to  pcre_exec(). Although not intended for this
2604           purpose, this facility could be used to match a pattern in a  different
2605           locale from the one in which it was compiled. Passing table pointers at
2606           run time is discussed below in the section on matching a pattern.
2607    
2608    
2609    INFORMATION ABOUT A PATTERN
2610    
2611           int pcre_fullinfo(const pcre *code, const pcre_extra *extra,
2612                int what, void *where);
2613    
2614           The pcre_fullinfo() function returns information about a compiled  pat-
2615           tern.  It replaces the pcre_info() function, which was removed from the
2616           library at version 8.30, after more than 10 years of obsolescence.
2617    
2618           The first argument for pcre_fullinfo() is a  pointer  to  the  compiled
2619           pattern.  The second argument is the result of pcre_study(), or NULL if
2620           the pattern was not studied. The third argument specifies  which  piece
2621           of  information  is required, and the fourth argument is a pointer to a
2622           variable to receive the data. The yield of the  function  is  zero  for
2623           success, or one of the following negative numbers:
2624    
2625             PCRE_ERROR_NULL           the argument code was NULL
2626                                       the argument where was NULL
2627             PCRE_ERROR_BADMAGIC       the "magic number" was not found
2628             PCRE_ERROR_BADENDIANNESS  the pattern was compiled with different
2629                                       endianness
2630             PCRE_ERROR_BADOPTION      the value of what was invalid
2631             PCRE_ERROR_UNSET          the requested field is not set
2632    
2633           The  "magic  number" is placed at the start of each compiled pattern as
2634           an simple check against passing an arbitrary memory pointer. The  endi-
2635           anness error can occur if a compiled pattern is saved and reloaded on a
2636           different host. Here is a typical call of  pcre_fullinfo(),  to  obtain
2637           the length of the compiled pattern:
2638    
2639             int rc;
2640             size_t length;
2641             rc = pcre_fullinfo(
2642               re,               /* result of pcre_compile() */
2643               sd,               /* result of pcre_study(), or NULL */
2644               PCRE_INFO_SIZE,   /* what is required */
2645               &length);         /* where to put the data */
2646    
2647           The  possible  values for the third argument are defined in pcre.h, and
2648           are as follows:
2649    
2650             PCRE_INFO_BACKREFMAX
2651    
2652           Return the number of the highest back reference  in  the  pattern.  The
2653           fourth  argument  should  point to an int variable. Zero is returned if
2654           there are no back references.
2655    
2656             PCRE_INFO_CAPTURECOUNT
2657    
2658           Return the number of capturing subpatterns in the pattern.  The  fourth
2659           argument should point to an int variable.
2660    
2661             PCRE_INFO_DEFAULT_TABLES
2662    
2663           Return  a pointer to the internal default character tables within PCRE.
2664           The fourth argument should point to an unsigned char *  variable.  This
2665           information call is provided for internal use by the pcre_study() func-
2666           tion. External callers can cause PCRE to use  its  internal  tables  by
2667           passing a NULL table pointer.
2668    
2669             PCRE_INFO_FIRSTBYTE
2670    
2671           Return information about the first data unit of any matched string, for
2672           a non-anchored pattern. (The name of this option refers  to  the  8-bit
2673           library,  where data units are bytes.) The fourth argument should point
2674           to an int variable.
2675    
2676           If there is a fixed first value, for example, the  letter  "c"  from  a
2677           pattern  such  as (cat|cow|coyote), its value is returned. In the 8-bit
2678           library, the value is always less than 256. In the 16-bit  library  the
2679           value can be up to 0xffff. In the 32-bit library the value can be up to
2680           0x10ffff.
2681    
2682           If there is no fixed first value, and if either
2683    
2684           (a) the pattern was compiled with the PCRE_MULTILINE option, and  every
2685           branch starts with "^", or
2686    
2687           (b) every branch of the pattern starts with ".*" and PCRE_DOTALL is not
2688           set (if it were set, the pattern would be anchored),
2689    
2690           -1 is returned, indicating that the pattern matches only at  the  start
2691           of  a  subject string or after any newline within the string. Otherwise
2692           -2 is returned. For anchored patterns, -2 is returned.
2693    
2694           Since for the 32-bit library using the non-UTF-32 mode,  this  function
2695           is  unable to return the full 32-bit range of the character, this value
2696           is   deprecated;   instead   the   PCRE_INFO_FIRSTCHARACTERFLAGS    and
2697           PCRE_INFO_FIRSTCHARACTER values should be used.
2698    
2699             PCRE_INFO_FIRSTTABLE
2700    
2701           If  the pattern was studied, and this resulted in the construction of a
2702           256-bit table indicating a fixed set of values for the first data  unit
2703           in  any  matching string, a pointer to the table is returned. Otherwise
2704           NULL is returned. The fourth argument should point to an unsigned  char
2705           * variable.
2706    
2707             PCRE_INFO_HASCRORLF
2708    
2709           Return  1  if  the  pattern  contains any explicit matches for CR or LF
2710           characters, otherwise 0. The fourth argument should  point  to  an  int
2711           variable.  An explicit match is either a literal CR or LF character, or
2712           \r or \n.
2713    
2714             PCRE_INFO_JCHANGED
2715    
2716           Return 1 if the (?J) or (?-J) option setting is used  in  the  pattern,
2717           otherwise  0. The fourth argument should point to an int variable. (?J)
2718           and (?-J) set and unset the local PCRE_DUPNAMES option, respectively.
2719    
2720             PCRE_INFO_JIT
2721    
2722           Return 1 if the pattern was studied with one of the  JIT  options,  and
2723           just-in-time compiling was successful. The fourth argument should point
2724           to an int variable. A return value of 0 means that JIT support  is  not
2725           available  in this version of PCRE, or that the pattern was not studied
2726           with a JIT option, or that the JIT compiler could not handle this  par-
2727           ticular  pattern. See the pcrejit documentation for details of what can
2728           and cannot be handled.
2729    
2730             PCRE_INFO_JITSIZE
2731    
2732           If the pattern was successfully studied with a JIT option,  return  the
2733           size  of the JIT compiled code, otherwise return zero. The fourth argu-
2734           ment should point to a size_t variable.
2735    
2736             PCRE_INFO_LASTLITERAL
2737    
2738           Return the value of the rightmost literal data unit that must exist  in
2739           any  matched  string, other than at its start, if such a value has been
2740           recorded. The fourth argument should point to an int variable. If there
2741           is no such value, -1 is returned. For anchored patterns, a last literal
2742           value is recorded only if it follows something of variable length.  For
2743           example, for the pattern /^a\d+z\d+/ the returned value is "z", but for
2744           /^a\dz\d/ the returned value is -1.
2745    
2746           Since for the 32-bit library using the non-UTF-32 mode,  this  function
2747           is  unable to return the full 32-bit range of the character, this value
2748           is   deprecated;   instead    the    PCRE_INFO_REQUIREDCHARFLAGS    and
2749           PCRE_INFO_REQUIREDCHAR values should be used.
2750    
2751             PCRE_INFO_MATCHLIMIT
2752    
2753           If  the  pattern  set  a  match  limit by including an item of the form
2754           (*LIMIT_MATCH=nnnn) at the start, the value  is  returned.  The  fourth
2755           argument  should  point to an unsigned 32-bit integer. If no such value
2756           has  been  set,  the  call  to  pcre_fullinfo()   returns   the   error
2757           PCRE_ERROR_UNSET.
2758    
2759             PCRE_INFO_MAXLOOKBEHIND
2760    
2761           Return  the  number  of  characters  (NB not data units) in the longest
2762           lookbehind assertion in the pattern. This information  is  useful  when
2763           doing  multi-segment  matching  using  the partial matching facilities.
2764           Note that the simple assertions \b and \B require a one-character look-
2765           behind.  \A  also  registers a one-character lookbehind, though it does
2766           not actually inspect the previous character. This is to ensure that  at
2767           least one character from the old segment is retained when a new segment
2768           is processed. Otherwise, if there are no lookbehinds in the pattern, \A
2769           might match incorrectly at the start of a new segment.
2770    
2771             PCRE_INFO_MINLENGTH
2772    
2773           If  the  pattern  was studied and a minimum length for matching subject
2774           strings was computed, its value is  returned.  Otherwise  the  returned
2775           value is -1. The value is a number of characters, which in UTF mode may
2776           be different from the number of data units. The fourth argument  should
2777           point  to an int variable. A non-negative value is a lower bound to the
2778           length of any matching string. There may not be  any  strings  of  that
2779           length  that  do actually match, but every string that does match is at
2780           least that long.
2781    
2782             PCRE_INFO_NAMECOUNT
2783             PCRE_INFO_NAMEENTRYSIZE
2784             PCRE_INFO_NAMETABLE
2785    
2786           PCRE supports the use of named as well as numbered capturing  parenthe-
2787           ses.  The names are just an additional way of identifying the parenthe-
2788           ses, which still acquire numbers. Several convenience functions such as
2789           pcre_get_named_substring()  are  provided  for extracting captured sub-
2790           strings by name. It is also possible to extract the data  directly,  by
2791           first  converting  the  name to a number in order to access the correct
2792           pointers in the output vector (described with pcre_exec() below). To do
2793           the  conversion,  you  need  to  use  the  name-to-number map, which is
2794           described by these three values.
2795    
2796           The map consists of a number of fixed-size entries. PCRE_INFO_NAMECOUNT
2797           gives the number of entries, and PCRE_INFO_NAMEENTRYSIZE gives the size
2798           of each entry; both of these  return  an  int  value.  The  entry  size
2799           depends  on the length of the longest name. PCRE_INFO_NAMETABLE returns
2800           a pointer to the first entry of the table. This is a pointer to char in
2801           the 8-bit library, where the first two bytes of each entry are the num-
2802           ber of the capturing parenthesis, most significant byte first.  In  the
2803           16-bit  library,  the pointer points to 16-bit data units, the first of
2804           which contains the parenthesis  number.  In  the  32-bit  library,  the
2805           pointer  points  to  32-bit data units, the first of which contains the
2806           parenthesis number. The rest of the entry is  the  corresponding  name,
2807           zero terminated.
2808    
2809           The  names are in alphabetical order. Duplicate names may appear if (?|
2810           is used to create multiple groups with the same number, as described in
2811           the  section  on  duplicate subpattern numbers in the pcrepattern page.
2812           Duplicate names for subpatterns with different  numbers  are  permitted
2813           only  if  PCRE_DUPNAMES  is  set. In all cases of duplicate names, they
2814           appear in the table in the order in which they were found in  the  pat-
2815           tern.  In  the  absence  of (?| this is the order of increasing number;
2816           when (?| is used this is not necessarily the case because later subpat-
2817           terns may have lower numbers.
2818    
2819           As  a  simple  example of the name/number table, consider the following
2820           pattern after compilation by the 8-bit library (assume PCRE_EXTENDED is
2821           set, so white space - including newlines - is ignored):
2822    
2823             (?<date> (?<year>(\d\d)?\d\d) -
2824             (?<month>\d\d) - (?<day>\d\d) )
2825    
2826           There  are  four  named subpatterns, so the table has four entries, and
2827           each entry in the table is eight bytes long. The table is  as  follows,
2828           with non-printing bytes shows in hexadecimal, and undefined bytes shown
2829           as ??:
2830    
2831             00 01 d  a  t  e  00 ??
2832             00 05 d  a  y  00 ?? ??
2833             00 04 m  o  n  t  h  00
2834             00 02 y  e  a  r  00 ??
2835    
2836           When writing code to extract data  from  named  subpatterns  using  the
2837           name-to-number  map,  remember that the length of the entries is likely
2838           to be different for each compiled pattern.
2839    
2840             PCRE_INFO_OKPARTIAL
2841    
2842           Return 1  if  the  pattern  can  be  used  for  partial  matching  with
2843           pcre_exec(),  otherwise  0.  The fourth argument should point to an int
2844           variable. From  release  8.00,  this  always  returns  1,  because  the
2845           restrictions  that  previously  applied  to  partial matching have been
2846           lifted. The pcrepartial documentation gives details of  partial  match-
2847           ing.
2848    
2849             PCRE_INFO_OPTIONS
2850    
2851           Return  a  copy of the options with which the pattern was compiled. The
2852           fourth argument should point to an unsigned long  int  variable.  These
2853           option bits are those specified in the call to pcre_compile(), modified
2854           by any top-level option settings at the start of the pattern itself. In
2855           other  words,  they are the options that will be in force when matching
2856           starts. For example, if the pattern /(?im)abc(?-i)d/ is  compiled  with
2857           the  PCRE_EXTENDED option, the result is PCRE_CASELESS, PCRE_MULTILINE,
2858           and PCRE_EXTENDED.
2859    
2860           A pattern is automatically anchored by PCRE if  all  of  its  top-level
2861           alternatives begin with one of the following:
2862    
2863             ^     unless PCRE_MULTILINE is set
2864             \A    always
2865             \G    always
2866             .*    if PCRE_DOTALL is set and there are no back
2867                     references to the subpattern in which .* appears
2868    
2869           For such patterns, the PCRE_ANCHORED bit is set in the options returned
2870           by pcre_fullinfo().
2871    
2872             PCRE_INFO_RECURSIONLIMIT
2873    
2874           If the pattern set a recursion limit by including an item of  the  form
2875           (*LIMIT_RECURSION=nnnn) at the start, the value is returned. The fourth
2876           argument should point to an unsigned 32-bit integer. If no  such  value
2877           has   been   set,   the  call  to  pcre_fullinfo()  returns  the  error
2878           PCRE_ERROR_UNSET.
2879    
2880             PCRE_INFO_SIZE
2881    
2882           Return the size of  the  compiled  pattern  in  bytes  (for  all  three
2883           libraries). The fourth argument should point to a size_t variable. This
2884           value does not include the size of the pcre structure that is  returned
2885           by  pcre_compile().  The  value  that  is  passed  as  the  argument to
2886           pcre_malloc() when pcre_compile() is getting memory in which  to  place
2887           the compiled data is the value returned by this option plus the size of
2888           the pcre structure. Studying a compiled pattern, with or  without  JIT,
2889           does not alter the value returned by this option.
2890    
2891             PCRE_INFO_STUDYSIZE
2892    
2893           Return  the  size  in bytes (for all three libraries) of the data block
2894           pointed to by the study_data field in a pcre_extra block. If pcre_extra
2895           is  NULL, or there is no study data, zero is returned. The fourth argu-
2896           ment should point to a size_t variable. The study_data field is set  by
2897           pcre_study() to record information that will speed up matching (see the
2898           section entitled  "Studying  a  pattern"  above).  The  format  of  the
2899           study_data  block is private, but its length is made available via this
2900           option so that it can be saved and  restored  (see  the  pcreprecompile
2901           documentation for details).
2902    
2903             PCRE_INFO_FIRSTCHARACTERFLAGS
2904    
2905           Return information about the first data unit of any matched string, for
2906           a non-anchored pattern. The fourth argument  should  point  to  an  int
2907           variable.
2908    
2909           If  there  is  a  fixed first value, for example, the letter "c" from a
2910           pattern such as (cat|cow|coyote), 1  is  returned,  and  the  character
2911           value can be retrieved using PCRE_INFO_FIRSTCHARACTER.
2912    
2913           If there is no fixed first value, and if either
2914    
2915           (a)  the pattern was compiled with the PCRE_MULTILINE option, and every
2916           branch starts with "^", or
2917    
2918           (b) every branch of the pattern starts with ".*" and PCRE_DOTALL is not
2919           set (if it were set, the pattern would be anchored),
2920    
2921           2 is returned, indicating that the pattern matches only at the start of
2922           a subject string or after any newline within the string. Otherwise 0 is
2923           returned. For anchored patterns, 0 is returned.
2924    
2925             PCRE_INFO_FIRSTCHARACTER
2926    
2927           Return  the  fixed  first character value, if PCRE_INFO_FIRSTCHARACTER-
2928           FLAGS returned 1; otherwise returns 0. The fourth argument should point
2929           to an uint_t variable.
2930    
2931           In  the 8-bit library, the value is always less than 256. In the 16-bit
2932           library the value can be up to 0xffff. In the 32-bit library in  UTF-32
2933           mode  the  value  can  be up to 0x10ffff, and up to 0xffffffff when not
2934           using UTF-32 mode.
2935    
2936           If there is no fixed first value, and if either
2937    
2938           (a) the pattern was compiled with the PCRE_MULTILINE option, and  every
2939           branch starts with "^", or
2940    
2941           (b) every branch of the pattern starts with ".*" and PCRE_DOTALL is not
2942           set (if it were set, the pattern would be anchored),
2943    
2944           -1 is returned, indicating that the pattern matches only at  the  start
2945           of  a  subject string or after any newline within the string. Otherwise
2946           -2 is returned. For anchored patterns, -2 is returned.
2947    
2948             PCRE_INFO_REQUIREDCHARFLAGS
2949    
2950           Returns 1 if there is a rightmost literal data unit that must exist  in
2951           any matched string, other than at its start. The fourth argument should
2952           point to an int variable. If there is no such value, 0 is returned.  If
2953           returning  1,  the  character  value  itself  can  be  retrieved  using
2954           PCRE_INFO_REQUIREDCHAR.
2955    
2956           For anchored patterns, a last literal value is recorded only if it fol-
2957           lows  something  of  variable  length.  For  example,  for  the pattern
2958           /^a\d+z\d+/  the   returned   value   1   (with   "z"   returned   from
2959           PCRE_INFO_REQUIREDCHAR), but for /^a\dz\d/ the returned value is 0.
2960    
2961             PCRE_INFO_REQUIREDCHAR
2962    
2963           Return  the value of the rightmost literal data unit that must exist in
2964           any matched string, other than at its start, if such a value  has  been
2965           recorded.  The fourth argument should point to an uint32_t variable. If
2966           there is no such value, 0 is returned.
2967    
2968    
2969    REFERENCE COUNTS
2970    
2971           int pcre_refcount(pcre *code, int adjust);
2972    
2973           The pcre_refcount() function is used to maintain a reference  count  in
2974           the data block that contains a compiled pattern. It is provided for the
2975           benefit of applications that  operate  in  an  object-oriented  manner,
2976           where different parts of the application may be using the same compiled
2977           pattern, but you want to free the block when they are all done.
2978    
2979           When a pattern is compiled, the reference count field is initialized to
2980           zero.   It is changed only by calling this function, whose action is to
2981           add the adjust value (which may be positive or  negative)  to  it.  The
2982           yield of the function is the new value. However, the value of the count
2983           is constrained to lie between 0 and 65535, inclusive. If the new  value
2984           is outside these limits, it is forced to the appropriate limit value.
2985    
2986           Except  when it is zero, the reference count is not correctly preserved
2987           if a pattern is compiled on one host and then  transferred  to  a  host
2988           whose byte-order is different. (This seems a highly unlikely scenario.)
2989    
2990    
2991    MATCHING A PATTERN: THE TRADITIONAL FUNCTION
2992    
2993           int pcre_exec(const pcre *code, const pcre_extra *extra,
2994                const char *subject, int length, int startoffset,
2995                int options, int *ovector, int ovecsize);
2996    
2997           The  function pcre_exec() is called to match a subject string against a
2998           compiled pattern, which is passed in the code argument. If the  pattern
2999           was  studied,  the  result  of  the study should be passed in the extra
3000           argument. You can call pcre_exec() with the same code and  extra  argu-
3001           ments  as  many  times as you like, in order to match different subject
3002           strings with the same pattern.
3003    
3004           This function is the main matching facility  of  the  library,  and  it
3005           operates  in  a  Perl-like  manner. For specialist use there is also an
3006           alternative matching function, which is described below in the  section
3007           about the pcre_dfa_exec() function.
3008    
3009           In  most applications, the pattern will have been compiled (and option-
3010           ally studied) in the same process that calls pcre_exec().  However,  it
3011           is possible to save compiled patterns and study data, and then use them
3012           later in different processes, possibly even on different hosts.  For  a
3013           discussion about this, see the pcreprecompile documentation.
3014    
3015           Here is an example of a simple call to pcre_exec():
3016    
3017             int rc;
3018             int ovector[30];
3019             rc = pcre_exec(
3020               re,             /* result of pcre_compile() */
3021               NULL,           /* we didn't study the pattern */
3022               "some string",  /* the subject string */
3023               11,             /* the length of the subject string */
3024               0,              /* start at offset 0 in the subject */
3025               0,              /* default options */
3026               ovector,        /* vector of integers for substring information */
3027               30);            /* number of elements (NOT size in bytes) */
3028    
3029       Extra data for pcre_exec()
3030    
3031           If  the  extra argument is not NULL, it must point to a pcre_extra data
3032           block. The pcre_study() function returns such a block (when it  doesn't
3033           return  NULL), but you can also create one for yourself, and pass addi-
3034           tional information in it. The pcre_extra block contains  the  following
3035           fields (not necessarily in this order):
3036    
3037             unsigned long int flags;
3038             void *study_data;
3039             void *executable_jit;
3040             unsigned long int match_limit;
3041             unsigned long int match_limit_recursion;
3042             void *callout_data;
3043             const unsigned char *tables;
3044             unsigned char **mark;
3045    
3046           In  the  16-bit  version  of  this  structure,  the mark field has type
3047           "PCRE_UCHAR16 **".
3048    
3049           In the 32-bit version of  this  structure,  the  mark  field  has  type
3050           "PCRE_UCHAR32 **".
3051    
3052           The  flags  field is used to specify which of the other fields are set.
3053           The flag bits are:
3054    
3055             PCRE_EXTRA_CALLOUT_DATA
3056             PCRE_EXTRA_EXECUTABLE_JIT
3057             PCRE_EXTRA_MARK
3058             PCRE_EXTRA_MATCH_LIMIT
3059             PCRE_EXTRA_MATCH_LIMIT_RECURSION
3060             PCRE_EXTRA_STUDY_DATA
3061             PCRE_EXTRA_TABLES
3062    
3063           Other flag bits should be set to zero. The study_data field  and  some-
3064           times  the executable_jit field are set in the pcre_extra block that is
3065           returned by pcre_study(), together with the appropriate flag bits.  You
3066           should  not set these yourself, but you may add to the block by setting
3067           other fields and their corresponding flag bits.
3068    
3069           The match_limit field provides a means of preventing PCRE from using up
3070           a  vast amount of resources when running patterns that are not going to
3071           match, but which have a very large number  of  possibilities  in  their
3072           search  trees. The classic example is a pattern that uses nested unlim-
3073           ited repeats.
3074    
3075           Internally, pcre_exec() uses a function called match(), which it  calls
3076           repeatedly  (sometimes  recursively).  The  limit set by match_limit is
3077           imposed on the number of times this function is called during a  match,
3078           which  has  the  effect of limiting the amount of backtracking that can
3079           take place. For patterns that are not anchored, the count restarts from
3080           zero for each position in the subject string.
3081    
3082           When pcre_exec() is called with a pattern that was successfully studied
3083           with a JIT option, the way that the matching is  executed  is  entirely
3084           different.  However, there is still the possibility of runaway matching
3085           that goes on for a very long time, and so the match_limit value is also
3086           used in this case (but in a different way) to limit how long the match-
3087           ing can continue.
3088    
3089           The default value for the limit can be set  when  PCRE  is  built;  the
3090           default  default  is 10 million, which handles all but the most extreme
3091           cases. You can override the default  by  suppling  pcre_exec()  with  a
3092           pcre_extra     block    in    which    match_limit    is    set,    and
3093           PCRE_EXTRA_MATCH_LIMIT is set in the  flags  field.  If  the  limit  is
3094           exceeded, pcre_exec() returns PCRE_ERROR_MATCHLIMIT.
3095    
3096           A  value  for  the  match  limit may also be supplied by an item at the
3097           start of a pattern of the form
3098    
3099             (*LIMIT_MATCH=d)
3100    
3101           where d is a decimal number. However, such a setting is ignored  unless
3102           d  is  less  than  the limit set by the caller of pcre_exec() or, if no
3103           such limit is set, less than the default.
3104    
3105           The match_limit_recursion field is similar to match_limit, but  instead
3106           of limiting the total number of times that match() is called, it limits
3107           the depth of recursion. The recursion depth is a  smaller  number  than
3108           the  total number of calls, because not all calls to match() are recur-
3109           sive.  This limit is of use only if it is set smaller than match_limit.
3110    
3111           Limiting the recursion depth limits the amount of  machine  stack  that
3112           can  be used, or, when PCRE has been compiled to use memory on the heap
3113           instead of the stack, the amount of heap memory that can be used.  This
3114           limit  is not relevant, and is ignored, when matching is done using JIT
3115           compiled code.
3116    
3117           The default value for match_limit_recursion can be  set  when  PCRE  is
3118           built;  the  default  default  is  the  same  value  as the default for
3119           match_limit. You can override the default by suppling pcre_exec()  with
3120           a   pcre_extra   block  in  which  match_limit_recursion  is  set,  and
3121           PCRE_EXTRA_MATCH_LIMIT_RECURSION is set in  the  flags  field.  If  the
3122           limit is exceeded, pcre_exec() returns PCRE_ERROR_RECURSIONLIMIT.
3123    
3124           A  value for the recursion limit may also be supplied by an item at the
3125           start of a pattern of the form
3126    
3127             (*LIMIT_RECURSION=d)
3128    
3129           where d is a decimal number. However, such a setting is ignored  unless
3130           d  is  less  than  the limit set by the caller of pcre_exec() or, if no
3131           such limit is set, less than the default.
3132    
3133           The callout_data field is used in conjunction with the  "callout"  fea-
3134           ture, and is described in the pcrecallout documentation.
3135    
3136           The  tables  field  is  used  to  pass  a  character  tables pointer to
3137           pcre_exec(); this overrides the value that is stored with the  compiled
3138           pattern.  A  non-NULL value is stored with the compiled pattern only if
3139           custom tables were supplied to pcre_compile() via  its  tableptr  argu-
3140           ment.  If NULL is passed to pcre_exec() using this mechanism, it forces
3141           PCRE's internal tables to be used. This facility is  helpful  when  re-
3142           using  patterns  that  have been saved after compiling with an external
3143           set of tables, because the external tables  might  be  at  a  different
3144           address  when  pcre_exec() is called. See the pcreprecompile documenta-
3145           tion for a discussion of saving compiled patterns for later use.
3146    
3147           If PCRE_EXTRA_MARK is set in the flags field, the mark  field  must  be
3148           set  to point to a suitable variable. If the pattern contains any back-
3149           tracking control verbs such as (*MARK:NAME), and the execution ends  up
3150           with  a  name  to  pass back, a pointer to the name string (zero termi-
3151           nated) is placed in the variable pointed to  by  the  mark  field.  The
3152           names  are  within  the  compiled pattern; if you wish to retain such a
3153           name you must copy it before freeing the memory of a compiled  pattern.
3154           If  there  is no name to pass back, the variable pointed to by the mark
3155           field is set to NULL. For details of the  backtracking  control  verbs,
3156           see the section entitled "Backtracking control" in the pcrepattern doc-
3157           umentation.
3158    
3159       Option bits for pcre_exec()
3160    
3161           The unused bits of the options argument for pcre_exec() must  be  zero.
3162           The  only  bits  that  may  be set are PCRE_ANCHORED, PCRE_NEWLINE_xxx,
3163           PCRE_NOTBOL,   PCRE_NOTEOL,    PCRE_NOTEMPTY,    PCRE_NOTEMPTY_ATSTART,
3164           PCRE_NO_START_OPTIMIZE,   PCRE_NO_UTF8_CHECK,   PCRE_PARTIAL_HARD,  and
3165           PCRE_PARTIAL_SOFT.
3166    
3167           If the pattern was successfully studied with one  of  the  just-in-time
3168           (JIT) compile options, the only supported options for JIT execution are
3169           PCRE_NO_UTF8_CHECK,    PCRE_NOTBOL,     PCRE_NOTEOL,     PCRE_NOTEMPTY,
3170           PCRE_NOTEMPTY_ATSTART,  PCRE_PARTIAL_HARD, and PCRE_PARTIAL_SOFT. If an
3171           unsupported option is used, JIT execution is disabled  and  the  normal
3172           interpretive code in pcre_exec() is run.
3173    
3174             PCRE_ANCHORED
3175    
3176           The  PCRE_ANCHORED  option  limits pcre_exec() to matching at the first
3177           matching position. If a pattern was  compiled  with  PCRE_ANCHORED,  or
3178           turned  out to be anchored by virtue of its contents, it cannot be made
3179           unachored at matching time.
3180    
3181             PCRE_BSR_ANYCRLF
3182             PCRE_BSR_UNICODE
3183    
3184           These options (which are mutually exclusive) control what the \R escape
3185           sequence  matches.  The choice is either to match only CR, LF, or CRLF,
3186           or to match any Unicode newline sequence. These  options  override  the
3187           choice that was made or defaulted when the pattern was compiled.
3188    
3189             PCRE_NEWLINE_CR
3190             PCRE_NEWLINE_LF
3191             PCRE_NEWLINE_CRLF
3192             PCRE_NEWLINE_ANYCRLF
3193             PCRE_NEWLINE_ANY
3194    
3195           These  options  override  the  newline  definition  that  was chosen or
3196           defaulted when the pattern was compiled. For details, see the  descrip-
3197           tion  of  pcre_compile()  above.  During  matching,  the newline choice
3198           affects the behaviour of the dot, circumflex,  and  dollar  metacharac-
3199           ters.  It may also alter the way the match position is advanced after a
3200           match failure for an unanchored pattern.
3201    
3202           When PCRE_NEWLINE_CRLF, PCRE_NEWLINE_ANYCRLF,  or  PCRE_NEWLINE_ANY  is
3203           set,  and a match attempt for an unanchored pattern fails when the cur-
3204           rent position is at a  CRLF  sequence,  and  the  pattern  contains  no
3205           explicit  matches  for  CR  or  LF  characters,  the  match position is
3206           advanced by two characters instead of one, in other words, to after the
3207           CRLF.
3208    
3209           The above rule is a compromise that makes the most common cases work as
3210           expected. For example, if the  pattern  is  .+A  (and  the  PCRE_DOTALL
3211           option is not set), it does not match the string "\r\nA" because, after
3212           failing at the start, it skips both the CR and the LF before  retrying.
3213           However,  the  pattern  [\r\n]A does match that string, because it con-
3214           tains an explicit CR or LF reference, and so advances only by one char-
3215           acter after the first failure.
3216    
3217           An explicit match for CR of LF is either a literal appearance of one of
3218           those characters, or one of the \r or  \n  escape  sequences.  Implicit
3219           matches  such  as [^X] do not count, nor does \s (which includes CR and
3220           LF in the characters that it matches).
3221    
3222           Notwithstanding the above, anomalous effects may still occur when  CRLF
3223           is a valid newline sequence and explicit \r or \n escapes appear in the
3224           pattern.
3225    
3226             PCRE_NOTBOL
3227    
3228           This option specifies that first character of the subject string is not
3229           the  beginning  of  a  line, so the circumflex metacharacter should not
3230           match before it. Setting this without PCRE_MULTILINE (at compile  time)
3231           causes  circumflex  never to match. This option affects only the behav-
3232           iour of the circumflex metacharacter. It does not affect \A.
3233    
3234             PCRE_NOTEOL
3235    
3236           This option specifies that the end of the subject string is not the end
3237           of  a line, so the dollar metacharacter should not match it nor (except
3238           in multiline mode) a newline immediately before it. Setting this  with-
3239           out PCRE_MULTILINE (at compile time) causes dollar never to match. This
3240           option affects only the behaviour of the dollar metacharacter. It  does
3241           not affect \Z or \z.
3242    
3243             PCRE_NOTEMPTY
3244    
3245           An empty string is not considered to be a valid match if this option is
3246           set. If there are alternatives in the pattern, they are tried.  If  all
3247           the  alternatives  match  the empty string, the entire match fails. For
3248           example, if the pattern
3249    
3250             a?b?
3251    
3252           is applied to a string not beginning with "a" or  "b",  it  matches  an
3253           empty  string at the start of the subject. With PCRE_NOTEMPTY set, this
3254           match is not valid, so PCRE searches further into the string for occur-
3255           rences of "a" or "b".
3256    
3257             PCRE_NOTEMPTY_ATSTART
3258    
3259           This  is  like PCRE_NOTEMPTY, except that an empty string match that is
3260           not at the start of  the  subject  is  permitted.  If  the  pattern  is
3261           anchored, such a match can occur only if the pattern contains \K.
3262    
3263           Perl     has    no    direct    equivalent    of    PCRE_NOTEMPTY    or
3264           PCRE_NOTEMPTY_ATSTART, but it does make a special  case  of  a  pattern
3265           match  of  the empty string within its split() function, and when using
3266           the /g modifier. It is  possible  to  emulate  Perl's  behaviour  after
3267           matching a null string by first trying the match again at the same off-
3268           set with PCRE_NOTEMPTY_ATSTART and  PCRE_ANCHORED,  and  then  if  that
3269           fails, by advancing the starting offset (see below) and trying an ordi-
3270           nary match again. There is some code that demonstrates how to  do  this
3271           in  the  pcredemo sample program. In the most general case, you have to
3272           check to see if the newline convention recognizes CRLF  as  a  newline,
3273           and  if so, and the current character is CR followed by LF, advance the
3274           starting offset by two characters instead of one.
3275    
3276             PCRE_NO_START_OPTIMIZE
3277    
3278           There are a number of optimizations that pcre_exec() uses at the  start
3279           of  a  match,  in  order to speed up the process. For example, if it is
3280           known that an unanchored match must start with a specific character, it
3281           searches  the  subject  for that character, and fails immediately if it
3282           cannot find it, without actually running the  main  matching  function.
3283           This means that a special item such as (*COMMIT) at the start of a pat-
3284           tern is not considered until after a suitable starting  point  for  the
3285           match  has been found. Also, when callouts or (*MARK) items are in use,
3286           these "start-up" optimizations can cause them to be skipped if the pat-
3287           tern is never actually used. The start-up optimizations are in effect a
3288           pre-scan of the subject that takes place before the pattern is run.
3289    
3290           The PCRE_NO_START_OPTIMIZE option disables the start-up  optimizations,
3291           possibly  causing  performance  to  suffer,  but ensuring that in cases
3292           where the result is "no match", the callouts do occur, and  that  items
3293           such as (*COMMIT) and (*MARK) are considered at every possible starting
3294           position in the subject string. If  PCRE_NO_START_OPTIMIZE  is  set  at
3295           compile  time,  it  cannot  be  unset  at  matching  time.  The  use of
3296           PCRE_NO_START_OPTIMIZE  at  matching  time  (that  is,  passing  it  to
3297           pcre_exec())  disables  JIT  execution;  in this situation, matching is
3298           always done using interpretively.
3299    
3300           Setting PCRE_NO_START_OPTIMIZE can change the  outcome  of  a  matching
3301           operation.  Consider the pattern
3302    
3303             (*COMMIT)ABC
3304    
3305           When  this  is  compiled, PCRE records the fact that a match must start
3306           with the character "A". Suppose the subject  string  is  "DEFABC".  The
3307           start-up  optimization  scans along the subject, finds "A" and runs the
3308           first match attempt from there. The (*COMMIT) item means that the  pat-
3309           tern  must  match the current starting position, which in this case, it
3310           does. However, if the same match  is  run  with  PCRE_NO_START_OPTIMIZE
3311           set,  the  initial  scan  along the subject string does not happen. The
3312           first match attempt is run starting  from  "D"  and  when  this  fails,
3313           (*COMMIT)  prevents  any  further  matches  being tried, so the overall
3314           result is "no match". If the pattern is studied,  more  start-up  opti-
3315           mizations  may  be  used. For example, a minimum length for the subject
3316           may be recorded. Consider the pattern
3317    
3318             (*MARK:A)(X|Y)
3319    
3320           The minimum length for a match is one  character.  If  the  subject  is
3321           "ABC",  there  will  be  attempts  to  match "ABC", "BC", "C", and then
3322           finally an empty string.  If the pattern is studied, the final  attempt
3323           does  not take place, because PCRE knows that the subject is too short,
3324           and so the (*MARK) is never encountered.  In this  case,  studying  the
3325           pattern  does  not  affect the overall match result, which is still "no
3326           match", but it does affect the auxiliary information that is returned.
3327    
3328             PCRE_NO_UTF8_CHECK
3329    
3330           When PCRE_UTF8 is set at compile time, the validity of the subject as a
3331           UTF-8  string is automatically checked when pcre_exec() is subsequently
3332           called.  The entire string is checked before any other processing takes
3333           place.  The  value  of  startoffset  is  also checked to ensure that it
3334           points to the start of a UTF-8 character. There is a  discussion  about
3335           the  validity  of  UTF-8 strings in the pcreunicode page. If an invalid
3336           sequence  of  bytes   is   found,   pcre_exec()   returns   the   error
3337           PCRE_ERROR_BADUTF8 or, if PCRE_PARTIAL_HARD is set and the problem is a
3338           truncated character at the end of the subject, PCRE_ERROR_SHORTUTF8. In
3339           both  cases, information about the precise nature of the error may also
3340           be returned (see the descriptions of these errors in the section  enti-
3341           tled  Error return values from pcre_exec() below).  If startoffset con-
3342           tains a value that does not point to the start of a UTF-8 character (or
3343           to the end of the subject), PCRE_ERROR_BADUTF8_OFFSET is returned.
3344    
3345           If  you  already  know that your subject is valid, and you want to skip
3346           these   checks   for   performance   reasons,   you   can    set    the
3347           PCRE_NO_UTF8_CHECK  option  when calling pcre_exec(). You might want to
3348           do this for the second and subsequent calls to pcre_exec() if  you  are
3349           making  repeated  calls  to  find  all  the matches in a single subject
3350           string. However, you should be  sure  that  the  value  of  startoffset
3351           points  to  the  start of a character (or the end of the subject). When
3352           PCRE_NO_UTF8_CHECK is set, the effect of passing an invalid string as a
3353           subject  or  an invalid value of startoffset is undefined. Your program
3354           may crash.
3355    
3356             PCRE_PARTIAL_HARD
3357             PCRE_PARTIAL_SOFT
3358    
3359           These options turn on the partial matching feature. For backwards  com-
3360           patibility,  PCRE_PARTIAL is a synonym for PCRE_PARTIAL_SOFT. A partial
3361           match occurs if the end of the subject string is reached  successfully,
3362           but  there  are not enough subject characters to complete the match. If
3363           this happens when PCRE_PARTIAL_SOFT (but not PCRE_PARTIAL_HARD) is set,
3364           matching  continues  by  testing any remaining alternatives. Only if no
3365           complete match can be found is PCRE_ERROR_PARTIAL returned  instead  of
3366           PCRE_ERROR_NOMATCH.  In  other  words,  PCRE_PARTIAL_SOFT says that the
3367           caller is prepared to handle a partial match, but only if  no  complete
3368           match can be found.
3369    
3370           If  PCRE_PARTIAL_HARD  is  set, it overrides PCRE_PARTIAL_SOFT. In this
3371           case, if a partial match  is  found,  pcre_exec()  immediately  returns
3372           PCRE_ERROR_PARTIAL,  without  considering  any  other  alternatives. In
3373           other words, when PCRE_PARTIAL_HARD is set, a partial match is  consid-
3374           ered to be more important that an alternative complete match.
3375    
3376           In  both  cases,  the portion of the string that was inspected when the
3377           partial match was found is set as the first matching string. There is a
3378           more  detailed  discussion  of partial and multi-segment matching, with
3379           examples, in the pcrepartial documentation.
3380    
3381       The string to be matched by pcre_exec()
3382    
3383           The subject string is passed to pcre_exec() as a pointer in subject,  a
3384           length  in  length, and a starting offset in startoffset. The units for
3385           length and startoffset are bytes for the  8-bit  library,  16-bit  data
3386           items  for  the  16-bit  library,  and 32-bit data items for the 32-bit
3387           library.
3388    
3389           If startoffset is negative or greater than the length of  the  subject,
3390           pcre_exec()  returns  PCRE_ERROR_BADOFFSET. When the starting offset is
3391           zero, the search for a match starts at the beginning  of  the  subject,
3392           and  this  is by far the most common case. In UTF-8 or UTF-16 mode, the
3393           offset must point to the start of a character, or the end of  the  sub-
3394           ject  (in  UTF-32 mode, one data unit equals one character, so all off-
3395           sets are valid). Unlike the pattern string,  the  subject  may  contain
3396           binary zeroes.
3397    
3398           A  non-zero  starting offset is useful when searching for another match
3399           in the same subject by calling pcre_exec() again after a previous  suc-
3400           cess.   Setting  startoffset differs from just passing over a shortened
3401           string and setting PCRE_NOTBOL in the case of  a  pattern  that  begins
3402           with any kind of lookbehind. For example, consider the pattern
3403    
3404             \Biss\B
3405    
3406           which  finds  occurrences  of "iss" in the middle of words. (\B matches
3407           only if the current position in the subject is not  a  word  boundary.)
3408           When  applied  to the string "Mississipi" the first call to pcre_exec()
3409           finds the first occurrence. If pcre_exec() is called  again  with  just
3410           the  remainder  of  the  subject,  namely  "issipi", it does not match,
3411           because \B is always false at the start of the subject, which is deemed
3412           to  be  a  word  boundary. However, if pcre_exec() is passed the entire
3413           string again, but with startoffset set to 4, it finds the second occur-
3414           rence  of "iss" because it is able to look behind the starting point to
3415           discover that it is preceded by a letter.
3416