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2  This file contains a concatenation of the PCRE man pages, converted to plain  This file contains a concatenation of the PCRE man pages, converted to plain
3  text format for ease of searching with a text editor, or for use on systems  text format for ease of searching with a text editor, or for use on systems
4  that do not have a man page processor. The small individual files that give  that do not have a man page processor. The small individual files that give
5  synopses of each function in the library have not been included. There are  synopses of each function in the library have not been included. Neither has
6  separate text files for the pcregrep and pcretest commands.  the pcredemo program. There are separate text files for the pcregrep and
7    pcretest commands.
8  -----------------------------------------------------------------------------  -----------------------------------------------------------------------------
9    
10    
11  PCRE(3)                                                                PCRE(3)  PCRE(3)                    Library Functions Manual                    PCRE(3)
12    
13    
14    
15  NAME  NAME
16         PCRE - Perl-compatible regular expressions         PCRE - Perl-compatible regular expressions
17    
   
18  INTRODUCTION  INTRODUCTION
19    
20         The  PCRE  library is a set of functions that implement regular expres-         The  PCRE  library is a set of functions that implement regular expres-
21         sion pattern matching using the same syntax and semantics as Perl, with         sion pattern matching using the same syntax and semantics as Perl, with
22         just  a  few  differences.  The current implementation of PCRE (release         just  a few differences. Some features that appeared in Python and PCRE
23         6.x) corresponds approximately with Perl  5.8,  including  support  for         before they appeared in Perl are also available using the  Python  syn-
24         UTF-8 encoded strings and Unicode general category properties. However,         tax,  there  is  some  support for one or two .NET and Oniguruma syntax
25         this support has to be explicitly enabled; it is not the default.         items, and there is an option for requesting some  minor  changes  that
26           give better JavaScript compatibility.
27         In addition to the Perl-compatible matching function,  PCRE  also  con-  
28         tains  an  alternative matching function that matches the same compiled         Starting with release 8.30, it is possible to compile two separate PCRE
29         patterns in a different way. In certain circumstances, the  alternative         libraries:  the  original,  which  supports  8-bit  character   strings
30         function  has  some  advantages.  For  a discussion of the two matching         (including  UTF-8  strings),  and a second library that supports 16-bit
31         algorithms, see the pcrematching page.         character strings (including UTF-16 strings). The build process  allows
32           either  one  or both to be built. The majority of the work to make this
33           possible was done by Zoltan Herczeg.
34    
35           Starting with release 8.32 it is possible to compile a  third  separate
36           PCRE library, which supports 32-bit character strings (including UTF-32
37           strings). The build process allows any set of the 8-,  16-  and  32-bit
38           libraries. The work to make this possible was done by Christian Persch.
39    
40           The  three  libraries  contain identical sets of functions, except that
41           the names in the 16-bit library start with pcre16_  instead  of  pcre_,
42           and  the  names  in  the  32-bit  library start with pcre32_ instead of
43           pcre_. To avoid over-complication and reduce the documentation  mainte-
44           nance load, most of the documentation describes the 8-bit library, with
45           the differences for the 16-bit and  32-bit  libraries  described  sepa-
46           rately  in  the  pcre16  and  pcre32  pages. References to functions or
47           structures of the  form  pcre[16|32]_xxx  should  be  read  as  meaning
48           "pcre_xxx  when  using  the  8-bit  library,  pcre16_xxx when using the
49           16-bit library, or pcre32_xxx when using the 32-bit library".
50    
51           The current implementation of PCRE corresponds approximately with  Perl
52           5.12,  including  support  for  UTF-8/16/32 encoded strings and Unicode
53           general category properties. However, UTF-8/16/32 and  Unicode  support
54           has to be explicitly enabled; it is not the default. The Unicode tables
55           correspond to Unicode release 6.2.0.
56    
57           In addition to the Perl-compatible matching function, PCRE contains  an
58           alternative  function that matches the same compiled patterns in a dif-
59           ferent way. In certain circumstances, the alternative function has some
60           advantages.   For  a discussion of the two matching algorithms, see the
61           pcrematching page.
62    
63         PCRE is written in C and released as a C library. A  number  of  people         PCRE is written in C and released as a C library. A  number  of  people
64         have  written  wrappers and interfaces of various kinds. In particular,         have  written  wrappers and interfaces of various kinds. In particular,
65         Google Inc.  have provided a comprehensive C++  wrapper.  This  is  now         Google Inc.  have provided a comprehensive C++ wrapper  for  the  8-bit
66         included as part of the PCRE distribution. The pcrecpp page has details         library.  This  is  now  included as part of the PCRE distribution. The
67         of this interface. Other people's contributions can  be  found  in  the         pcrecpp page has details of this interface.  Other  people's  contribu-
68         Contrib directory at the primary FTP site, which is:         tions  can  be  found in the Contrib directory at the primary FTP site,
69           which is:
70    
71         ftp://ftp.csx.cam.ac.uk/pub/software/programming/pcre         ftp://ftp.csx.cam.ac.uk/pub/software/programming/pcre
72    
73         Details  of  exactly which Perl regular expression features are and are         Details of exactly which Perl regular expression features are  and  are
74         not supported by PCRE are given in separate documents. See the pcrepat-         not supported by PCRE are given in separate documents. See the pcrepat-
75         tern and pcrecompat pages.         tern and pcrecompat pages. There is a syntax summary in the  pcresyntax
76           page.
77    
78         Some  features  of  PCRE can be included, excluded, or changed when the         Some  features  of  PCRE can be included, excluded, or changed when the
79         library is built. The pcre_config() function makes it  possible  for  a         library is built. The pcre_config() function makes it  possible  for  a
80         client  to  discover  which  features are available. The features them-         client  to  discover  which  features are available. The features them-
81         selves are described in the pcrebuild page. Documentation about  build-         selves are described in the pcrebuild page. Documentation about  build-
82         ing  PCRE for various operating systems can be found in the README file         ing  PCRE  for various operating systems can be found in the README and
83         in the source distribution.         NON-AUTOTOOLS_BUILD files in the source distribution.
84    
85         The library contains a number of undocumented  internal  functions  and         The libraries contains a number of undocumented internal functions  and
86         data  tables  that  are  used by more than one of the exported external         data  tables  that  are  used by more than one of the exported external
87         functions, but which are not intended  for  use  by  external  callers.         functions, but which are not intended  for  use  by  external  callers.
88         Their  names  all begin with "_pcre_", which hopefully will not provoke         Their  names all begin with "_pcre_" or "_pcre16_" or "_pcre32_", which
89         any name clashes. In some environments, it is possible to control which         hopefully will not provoke any name clashes. In some  environments,  it
90         external  symbols  are  exported when a shared library is built, and in         is  possible  to  control  which  external  symbols are exported when a
91         these cases the undocumented symbols are not exported.         shared library is built, and in these cases  the  undocumented  symbols
92           are not exported.
93    
94    
95    SECURITY CONSIDERATIONS
96    
97           If  you  are  using PCRE in a non-UTF application that permits users to
98           supply arbitrary patterns for compilation, you should  be  aware  of  a
99           feature that allows users to turn on UTF support from within a pattern,
100           provided that PCRE was built with UTF support. For  example,  an  8-bit
101           pattern  that  begins  with  "(*UTF8)" or "(*UTF)" turns on UTF-8 mode,
102           which interprets patterns and subjects as strings of  UTF-8  characters
103           instead  of  individual 8-bit characters.  This causes both the pattern
104           and any data against which it is matched to be checked for UTF-8 valid-
105           ity.  If  the  data  string is very long, such a check might use suffi-
106           ciently many resources as to cause your  application  to  lose  perfor-
107           mance.
108    
109           One   way   of   guarding  against  this  possibility  is  to  use  the
110           pcre_fullinfo() function to check the compiled  pattern's  options  for
111           UTF.   Alternatively, from release 8.33, you can set the PCRE_NEVER_UTF
112           option at compile time. This causes an compile time error if a  pattern
113           contains a UTF-setting sequence.
114    
115           If  your  application  is one that supports UTF, be aware that validity
116           checking can take time. If the same data string is to be  matched  many
117           times, you can use the PCRE_NO_UTF[8|16|32]_CHECK option for the second
118           and subsequent matches to save redundant checks.
119    
120           Another way that performance can be hit is by running  a  pattern  that
121           has  a  very  large search tree against a string that will never match.
122           Nested unlimited repeats in a pattern are a common example.  PCRE  pro-
123           vides some protection against this: see the PCRE_EXTRA_MATCH_LIMIT fea-
124           ture in the pcreapi page.
125    
126    
127  USER DOCUMENTATION  USER DOCUMENTATION
# Line 63  USER DOCUMENTATION Line 129  USER DOCUMENTATION
129         The user documentation for PCRE comprises a number  of  different  sec-         The user documentation for PCRE comprises a number  of  different  sec-
130         tions.  In the "man" format, each of these is a separate "man page". In         tions.  In the "man" format, each of these is a separate "man page". In
131         the HTML format, each is a separate page, linked from the  index  page.         the HTML format, each is a separate page, linked from the  index  page.
132         In  the  plain text format, all the sections are concatenated, for ease         In  the  plain  text format, all the sections, except the pcredemo sec-
133         of searching. The sections are as follows:         tion, are concatenated, for ease of searching. The sections are as fol-
134           lows:
135    
136           pcre              this document           pcre              this document
137             pcre16            details of the 16-bit library
138             pcre32            details of the 32-bit library
139             pcre-config       show PCRE installation configuration information
140           pcreapi           details of PCRE's native C API           pcreapi           details of PCRE's native C API
141           pcrebuild         options for building PCRE           pcrebuild         options for building PCRE
142           pcrecallout       details of the callout feature           pcrecallout       details of the callout feature
143           pcrecompat        discussion of Perl compatibility           pcrecompat        discussion of Perl compatibility
144           pcrecpp           details of the C++ wrapper           pcrecpp           details of the C++ wrapper for the 8-bit library
145           pcregrep          description of the pcregrep command           pcredemo          a demonstration C program that uses PCRE
146             pcregrep          description of the pcregrep command (8-bit only)
147             pcrejit           discussion of the just-in-time optimization support
148             pcrelimits        details of size and other limits
149           pcrematching      discussion of the two matching algorithms           pcrematching      discussion of the two matching algorithms
150           pcrepartial       details of the partial matching facility           pcrepartial       details of the partial matching facility
151           pcrepattern       syntax and semantics of supported           pcrepattern       syntax and semantics of supported
152                               regular expressions                               regular expressions
153           pcreperform       discussion of performance issues           pcreperform       discussion of performance issues
154           pcreposix         the POSIX-compatible C API           pcreposix         the POSIX-compatible C API for the 8-bit library
155           pcreprecompile    details of saving and re-using precompiled patterns           pcreprecompile    details of saving and re-using precompiled patterns
156           pcresample        discussion of the sample program           pcresample        discussion of the pcredemo program
157             pcrestack         discussion of stack usage
158             pcresyntax        quick syntax reference
159           pcretest          description of the pcretest testing command           pcretest          description of the pcretest testing command
160             pcreunicode       discussion of Unicode and UTF-8/16/32 support
161    
162         In  addition,  in the "man" and HTML formats, there is a short page for         In  addition,  in the "man" and HTML formats, there is a short page for
163         each C library function, listing its arguments and results.         each C library function, listing its arguments and results.
164    
165    
166  LIMITATIONS  AUTHOR
167    
168         There are some size limitations in PCRE but it is hoped that they  will         Philip Hazel
169         never in practice be relevant.         University Computing Service
170           Cambridge CB2 3QH, England.
171    
172         The  maximum  length of a compiled pattern is 65539 (sic) bytes if PCRE         Putting an actual email address here seems to have been a spam  magnet,
173         is compiled with the default internal linkage size of 2. If you want to         so  I've  taken  it away. If you want to email me, use my two initials,
174         process  regular  expressions  that are truly enormous, you can compile         followed by the two digits 10, at the domain cam.ac.uk.
        PCRE with an internal linkage size of 3 or 4 (see the  README  file  in  
        the  source  distribution and the pcrebuild documentation for details).  
        In these cases the limit is substantially larger.  However,  the  speed  
        of execution will be slower.  
   
        All values in repeating quantifiers must be less than 65536.  The maxi-  
        mum number of capturing subpatterns is 65535.  
   
        There is no limit to the number of non-capturing subpatterns,  but  the  
        maximum  depth  of  nesting  of  all kinds of parenthesized subpattern,  
        including capturing subpatterns, assertions, and other types of subpat-  
        tern, is 200.  
175    
        The  maximum  length of a subject string is the largest positive number  
        that an integer variable can hold. However, when using the  traditional  
        matching function, PCRE uses recursion to handle subpatterns and indef-  
        inite repetition.  This means that the available stack space may  limit  
        the size of a subject string that can be processed by certain patterns.  
176    
177    REVISION
178    
179  UTF-8 AND UNICODE PROPERTY SUPPORT         Last updated: 26 April 2013
180           Copyright (c) 1997-2013 University of Cambridge.
181    ------------------------------------------------------------------------------
182    
183    
184    PCRE(3)                    Library Functions Manual                    PCRE(3)
185    
        From release 3.3, PCRE has  had  some  support  for  character  strings  
        encoded  in the UTF-8 format. For release 4.0 this was greatly extended  
        to cover most common requirements, and in release 5.0  additional  sup-  
        port for Unicode general category properties was added.  
   
        In  order  process  UTF-8 strings, you must build PCRE to include UTF-8  
        support in the code, and, in addition,  you  must  call  pcre_compile()  
        with  the PCRE_UTF8 option flag. When you do this, both the pattern and  
        any subject strings that are matched against it are  treated  as  UTF-8  
        strings instead of just strings of bytes.  
   
        If  you compile PCRE with UTF-8 support, but do not use it at run time,  
        the library will be a bit bigger, but the additional run time  overhead  
        is  limited  to testing the PCRE_UTF8 flag in several places, so should  
        not be very large.  
186    
        If PCRE is built with Unicode character property support (which implies  
        UTF-8  support),  the  escape sequences \p{..}, \P{..}, and \X are sup-  
        ported.  The available properties that can be tested are limited to the  
        general  category  properties such as Lu for an upper case letter or Nd  
        for a decimal number. A full list is given in the pcrepattern  documen-  
        tation. The PCRE library is increased in size by about 90K when Unicode  
        property support is included.  
   
        The following comments apply when PCRE is running in UTF-8 mode:  
   
        1. When you set the PCRE_UTF8 flag, the strings passed as patterns  and  
        subjects  are  checked for validity on entry to the relevant functions.  
        If an invalid UTF-8 string is passed, an error return is given. In some  
        situations,  you  may  already  know  that  your strings are valid, and  
        therefore want to skip these checks in order to improve performance. If  
        you  set  the  PCRE_NO_UTF8_CHECK  flag at compile time or at run time,  
        PCRE assumes that the pattern or subject  it  is  given  (respectively)  
        contains  only valid UTF-8 codes. In this case, it does not diagnose an  
        invalid UTF-8 string. If you pass an invalid UTF-8 string to PCRE  when  
        PCRE_NO_UTF8_CHECK  is set, the results are undefined. Your program may  
        crash.  
   
        2. In a pattern, the escape sequence \x{...}, where the contents of the  
        braces  is  a  string  of hexadecimal digits, is interpreted as a UTF-8  
        character whose code number is the given hexadecimal number, for  exam-  
        ple:  \x{1234}.  If a non-hexadecimal digit appears between the braces,  
        the item is not recognized.  This escape sequence can be used either as  
        a literal, or within a character class.  
   
        3.  The  original hexadecimal escape sequence, \xhh, matches a two-byte  
        UTF-8 character if the value is greater than 127.  
   
        4. Repeat quantifiers apply to complete UTF-8 characters, not to  indi-  
        vidual bytes, for example: \x{100}{3}.  
   
        5.  The dot metacharacter matches one UTF-8 character instead of a sin-  
        gle byte.  
   
        6. The escape sequence \C can be used to match a single byte  in  UTF-8  
        mode,  but  its  use can lead to some strange effects. This facility is  
        not available in the alternative matching function, pcre_dfa_exec().  
   
        7. The character escapes \b, \B, \d, \D, \s, \S, \w, and  \W  correctly  
        test  characters of any code value, but the characters that PCRE recog-  
        nizes as digits, spaces, or word characters  remain  the  same  set  as  
        before, all with values less than 256. This remains true even when PCRE  
        includes Unicode property support, because to do otherwise  would  slow  
        down  PCRE in many common cases. If you really want to test for a wider  
        sense of, say, "digit", you must use Unicode  property  tests  such  as  
        \p{Nd}.  
187    
188         8.  Similarly,  characters that match the POSIX named character classes  NAME
189         are all low-valued characters.         PCRE - Perl-compatible regular expressions
190    
191           #include <pcre.h>
192    
193    
194    PCRE 16-BIT API BASIC FUNCTIONS
195    
196           pcre16 *pcre16_compile(PCRE_SPTR16 pattern, int options,
197                const char **errptr, int *erroffset,
198                const unsigned char *tableptr);
199    
200           pcre16 *pcre16_compile2(PCRE_SPTR16 pattern, int options,
201                int *errorcodeptr,
202                const char **errptr, int *erroffset,
203                const unsigned char *tableptr);
204    
205           pcre16_extra *pcre16_study(const pcre16 *code, int options,
206                const char **errptr);
207    
208           void pcre16_free_study(pcre16_extra *extra);
209    
210           int pcre16_exec(const pcre16 *code, const pcre16_extra *extra,
211                PCRE_SPTR16 subject, int length, int startoffset,
212                int options, int *ovector, int ovecsize);
213    
214           int pcre16_dfa_exec(const pcre16 *code, const pcre16_extra *extra,
215                PCRE_SPTR16 subject, int length, int startoffset,
216                int options, int *ovector, int ovecsize,
217                int *workspace, int wscount);
218    
219    
220    PCRE 16-BIT API STRING EXTRACTION FUNCTIONS
221    
222           int pcre16_copy_named_substring(const pcre16 *code,
223                PCRE_SPTR16 subject, int *ovector,
224                int stringcount, PCRE_SPTR16 stringname,
225                PCRE_UCHAR16 *buffer, int buffersize);
226    
227           int pcre16_copy_substring(PCRE_SPTR16 subject, int *ovector,
228                int stringcount, int stringnumber, PCRE_UCHAR16 *buffer,
229                int buffersize);
230    
231           int pcre16_get_named_substring(const pcre16 *code,
232                PCRE_SPTR16 subject, int *ovector,
233                int stringcount, PCRE_SPTR16 stringname,
234                PCRE_SPTR16 *stringptr);
235    
236           int pcre16_get_stringnumber(const pcre16 *code,
237                PCRE_SPTR16 name);
238    
239           int pcre16_get_stringtable_entries(const pcre16 *code,
240                PCRE_SPTR16 name, PCRE_UCHAR16 **first, PCRE_UCHAR16 **last);
241    
242           int pcre16_get_substring(PCRE_SPTR16 subject, int *ovector,
243                int stringcount, int stringnumber,
244                PCRE_SPTR16 *stringptr);
245    
246           int pcre16_get_substring_list(PCRE_SPTR16 subject,
247                int *ovector, int stringcount, PCRE_SPTR16 **listptr);
248    
249           void pcre16_free_substring(PCRE_SPTR16 stringptr);
250    
251           void pcre16_free_substring_list(PCRE_SPTR16 *stringptr);
252    
253         9. Case-insensitive matching applies only to  characters  whose  values  
254         are  less than 128, unless PCRE is built with Unicode property support.  PCRE 16-BIT API AUXILIARY FUNCTIONS
255         Even when Unicode property support is available, PCRE  still  uses  its  
256         own  character  tables when checking the case of low-valued characters,         pcre16_jit_stack *pcre16_jit_stack_alloc(int startsize, int maxsize);
257         so as not to degrade performance.  The Unicode property information  is  
258         used only for characters with higher values.         void pcre16_jit_stack_free(pcre16_jit_stack *stack);
259    
260           void pcre16_assign_jit_stack(pcre16_extra *extra,
261                pcre16_jit_callback callback, void *data);
262    
263           const unsigned char *pcre16_maketables(void);
264    
265           int pcre16_fullinfo(const pcre16 *code, const pcre16_extra *extra,
266                int what, void *where);
267    
268           int pcre16_refcount(pcre16 *code, int adjust);
269    
270           int pcre16_config(int what, void *where);
271    
272           const char *pcre16_version(void);
273    
274           int pcre16_pattern_to_host_byte_order(pcre16 *code,
275                pcre16_extra *extra, const unsigned char *tables);
276    
277    
278    PCRE 16-BIT API INDIRECTED FUNCTIONS
279    
280           void *(*pcre16_malloc)(size_t);
281    
282           void (*pcre16_free)(void *);
283    
284           void *(*pcre16_stack_malloc)(size_t);
285    
286           void (*pcre16_stack_free)(void *);
287    
288           int (*pcre16_callout)(pcre16_callout_block *);
289    
290    
291    PCRE 16-BIT API 16-BIT-ONLY FUNCTION
292    
293           int pcre16_utf16_to_host_byte_order(PCRE_UCHAR16 *output,
294                PCRE_SPTR16 input, int length, int *byte_order,
295                int keep_boms);
296    
297    
298    THE PCRE 16-BIT LIBRARY
299    
300           Starting  with  release  8.30, it is possible to compile a PCRE library
301           that supports 16-bit character strings, including  UTF-16  strings,  as
302           well  as  or instead of the original 8-bit library. The majority of the
303           work to make  this  possible  was  done  by  Zoltan  Herczeg.  The  two
304           libraries contain identical sets of functions, used in exactly the same
305           way. Only the names of the functions and the data types of their  argu-
306           ments  and results are different. To avoid over-complication and reduce
307           the documentation maintenance load,  most  of  the  PCRE  documentation
308           describes  the  8-bit  library,  with only occasional references to the
309           16-bit library. This page describes what is different when you use  the
310           16-bit library.
311    
312           WARNING:  A  single  application can be linked with both libraries, but
313           you must take care when processing any particular pattern to use  func-
314           tions  from  just one library. For example, if you want to study a pat-
315           tern that was compiled with  pcre16_compile(),  you  must  do  so  with
316           pcre16_study(), not pcre_study(), and you must free the study data with
317           pcre16_free_study().
318    
319    
320    THE HEADER FILE
321    
322           There is only one header file, pcre.h. It contains prototypes  for  all
323           the functions in all libraries, as well as definitions of flags, struc-
324           tures, error codes, etc.
325    
326    
327    THE LIBRARY NAME
328    
329           In Unix-like systems, the 16-bit library is called libpcre16,  and  can
330           normally  be  accesss  by adding -lpcre16 to the command for linking an
331           application that uses PCRE.
332    
333    
334    STRING TYPES
335    
336           In the 8-bit library, strings are passed to PCRE library  functions  as
337           vectors  of  bytes  with  the  C  type "char *". In the 16-bit library,
338           strings are passed as vectors of unsigned 16-bit quantities. The  macro
339           PCRE_UCHAR16  specifies  an  appropriate  data type, and PCRE_SPTR16 is
340           defined as "const PCRE_UCHAR16 *". In very  many  environments,  "short
341           int" is a 16-bit data type. When PCRE is built, it defines PCRE_UCHAR16
342           as "unsigned short int", but checks that it really  is  a  16-bit  data
343           type.  If  it is not, the build fails with an error message telling the
344           maintainer to modify the definition appropriately.
345    
346    
347    STRUCTURE TYPES
348    
349           The types of the opaque structures that are used  for  compiled  16-bit
350           patterns  and  JIT stacks are pcre16 and pcre16_jit_stack respectively.
351           The  type  of  the  user-accessible  structure  that  is  returned   by
352           pcre16_study()  is  pcre16_extra, and the type of the structure that is
353           used for passing data to a callout  function  is  pcre16_callout_block.
354           These structures contain the same fields, with the same names, as their
355           8-bit counterparts. The only difference is that pointers  to  character
356           strings are 16-bit instead of 8-bit types.
357    
358    
359    16-BIT FUNCTIONS
360    
361           For  every function in the 8-bit library there is a corresponding func-
362           tion in the 16-bit library with a name that starts with pcre16_ instead
363           of  pcre_.  The  prototypes are listed above. In addition, there is one
364           extra function, pcre16_utf16_to_host_byte_order(). This  is  a  utility
365           function  that converts a UTF-16 character string to host byte order if
366           necessary. The other 16-bit  functions  expect  the  strings  they  are
367           passed to be in host byte order.
368    
369           The input and output arguments of pcre16_utf16_to_host_byte_order() may
370           point to the same address, that is, conversion in place  is  supported.
371           The output buffer must be at least as long as the input.
372    
373           The  length  argument  specifies the number of 16-bit data units in the
374           input string; a negative value specifies a zero-terminated string.
375    
376           If byte_order is NULL, it is assumed that the string starts off in host
377           byte  order. This may be changed by byte-order marks (BOMs) anywhere in
378           the string (commonly as the first character).
379    
380           If byte_order is not NULL, a non-zero value of the integer to which  it
381           points  means  that  the input starts off in host byte order, otherwise
382           the opposite order is assumed. Again, BOMs in  the  string  can  change
383           this. The final byte order is passed back at the end of processing.
384    
385           If  keep_boms  is  not  zero,  byte-order  mark characters (0xfeff) are
386           copied into the output string. Otherwise they are discarded.
387    
388           The result of the function is the number of 16-bit  units  placed  into
389           the  output  buffer,  including  the  zero terminator if the string was
390           zero-terminated.
391    
392    
393    SUBJECT STRING OFFSETS
394    
395           The lengths and starting offsets of subject strings must  be  specified
396           in  16-bit  data units, and the offsets within subject strings that are
397           returned by the matching functions are in also 16-bit units rather than
398           bytes.
399    
400    
401    NAMED SUBPATTERNS
402    
403           The  name-to-number translation table that is maintained for named sub-
404           patterns uses 16-bit characters.  The  pcre16_get_stringtable_entries()
405           function returns the length of each entry in the table as the number of
406           16-bit data units.
407    
408    
409    OPTION NAMES
410    
411           There   are   two   new   general   option   names,   PCRE_UTF16    and
412           PCRE_NO_UTF16_CHECK,     which     correspond    to    PCRE_UTF8    and
413           PCRE_NO_UTF8_CHECK in the 8-bit library. In  fact,  these  new  options
414           define  the  same bits in the options word. There is a discussion about
415           the validity of UTF-16 strings in the pcreunicode page.
416    
417           For the pcre16_config() function there is an  option  PCRE_CONFIG_UTF16
418           that  returns  1  if UTF-16 support is configured, otherwise 0. If this
419           option  is  given  to  pcre_config()  or  pcre32_config(),  or  if  the
420           PCRE_CONFIG_UTF8  or  PCRE_CONFIG_UTF32  option is given to pcre16_con-
421           fig(), the result is the PCRE_ERROR_BADOPTION error.
422    
423    
424    CHARACTER CODES
425    
426           In 16-bit mode, when  PCRE_UTF16  is  not  set,  character  values  are
427           treated in the same way as in 8-bit, non UTF-8 mode, except, of course,
428           that they can range from 0 to 0xffff instead of 0  to  0xff.  Character
429           types  for characters less than 0xff can therefore be influenced by the
430           locale in the same way as before.  Characters greater  than  0xff  have
431           only one case, and no "type" (such as letter or digit).
432    
433           In  UTF-16  mode,  the  character  code  is  Unicode, in the range 0 to
434           0x10ffff, with the exception of values in the range  0xd800  to  0xdfff
435           because  those  are "surrogate" values that are used in pairs to encode
436           values greater than 0xffff.
437    
438           A UTF-16 string can indicate its endianness by special code knows as  a
439           byte-order mark (BOM). The PCRE functions do not handle this, expecting
440           strings  to  be  in  host  byte  order.  A  utility   function   called
441           pcre16_utf16_to_host_byte_order()  is  provided  to help with this (see
442           above).
443    
444    
445    ERROR NAMES
446    
447           The errors PCRE_ERROR_BADUTF16_OFFSET and PCRE_ERROR_SHORTUTF16  corre-
448           spond  to  their  8-bit  counterparts.  The error PCRE_ERROR_BADMODE is
449           given when a compiled pattern is passed to a  function  that  processes
450           patterns  in  the  other  mode, for example, if a pattern compiled with
451           pcre_compile() is passed to pcre16_exec().
452    
453           There are new error codes whose names  begin  with  PCRE_UTF16_ERR  for
454           invalid  UTF-16  strings,  corresponding to the PCRE_UTF8_ERR codes for
455           UTF-8 strings that are described in the section entitled "Reason  codes
456           for  invalid UTF-8 strings" in the main pcreapi page. The UTF-16 errors
457           are:
458    
459             PCRE_UTF16_ERR1  Missing low surrogate at end of string
460             PCRE_UTF16_ERR2  Invalid low surrogate follows high surrogate
461             PCRE_UTF16_ERR3  Isolated low surrogate
462             PCRE_UTF16_ERR4  Non-character
463    
464    
465    ERROR TEXTS
466    
467           If there is an error while compiling a pattern, the error text that  is
468           passed  back by pcre16_compile() or pcre16_compile2() is still an 8-bit
469           character string, zero-terminated.
470    
471    
472    CALLOUTS
473    
474           The subject and mark fields in the callout block that is  passed  to  a
475           callout function point to 16-bit vectors.
476    
477    
478    TESTING
479    
480           The  pcretest  program continues to operate with 8-bit input and output
481           files, but it can be used for testing the 16-bit library. If it is  run
482           with the command line option -16, patterns and subject strings are con-
483           verted from 8-bit to 16-bit before being passed to PCRE, and the 16-bit
484           library  functions  are used instead of the 8-bit ones. Returned 16-bit
485           strings are converted to 8-bit for output. If both the  8-bit  and  the
486           32-bit libraries were not compiled, pcretest defaults to 16-bit and the
487           -16 option is ignored.
488    
489           When PCRE is being built, the RunTest script that is  called  by  "make
490           check"  uses  the  pcretest  -C  option to discover which of the 8-bit,
491           16-bit and 32-bit libraries has been built, and runs the  tests  appro-
492           priately.
493    
494    
495    NOT SUPPORTED IN 16-BIT MODE
496    
497           Not all the features of the 8-bit library are available with the 16-bit
498           library. The C++ and POSIX wrapper functions  support  only  the  8-bit
499           library, and the pcregrep program is at present 8-bit only.
500    
501    
502  AUTHOR  AUTHOR
503    
504         Philip Hazel         Philip Hazel
505         University Computing Service,         University Computing Service
506         Cambridge CB2 3QG, England.         Cambridge CB2 3QH, England.
507    
        Putting  an actual email address here seems to have been a spam magnet,  
        so I've taken it away. If you want to email me, use my initial and sur-  
        name, separated by a dot, at the domain ucs.cam.ac.uk.  
508    
509  Last updated: 07 March 2005  REVISION
 Copyright (c) 1997-2005 University of Cambridge.  
 ------------------------------------------------------------------------------  
510    
511           Last updated: 12 May 2013
512           Copyright (c) 1997-2013 University of Cambridge.
513    ------------------------------------------------------------------------------
514    
515    
516    PCRE(3)                    Library Functions Manual                    PCRE(3)
517    
 PCREBUILD(3)                                                      PCREBUILD(3)  
518    
519    
520  NAME  NAME
521         PCRE - Perl-compatible regular expressions         PCRE - Perl-compatible regular expressions
522    
523           #include <pcre.h>
524    
525    
526    PCRE 32-BIT API BASIC FUNCTIONS
527    
528           pcre32 *pcre32_compile(PCRE_SPTR32 pattern, int options,
529                const char **errptr, int *erroffset,
530                const unsigned char *tableptr);
531    
532           pcre32 *pcre32_compile2(PCRE_SPTR32 pattern, int options,
533                int *errorcodeptr,
534                const char **errptr, int *erroffset,
535                const unsigned char *tableptr);
536    
537           pcre32_extra *pcre32_study(const pcre32 *code, int options,
538                const char **errptr);
539    
540           void pcre32_free_study(pcre32_extra *extra);
541    
542           int pcre32_exec(const pcre32 *code, const pcre32_extra *extra,
543                PCRE_SPTR32 subject, int length, int startoffset,
544                int options, int *ovector, int ovecsize);
545    
546           int pcre32_dfa_exec(const pcre32 *code, const pcre32_extra *extra,
547                PCRE_SPTR32 subject, int length, int startoffset,
548                int options, int *ovector, int ovecsize,
549                int *workspace, int wscount);
550    
551    
552    PCRE 32-BIT API STRING EXTRACTION FUNCTIONS
553    
554           int pcre32_copy_named_substring(const pcre32 *code,
555                PCRE_SPTR32 subject, int *ovector,
556                int stringcount, PCRE_SPTR32 stringname,
557                PCRE_UCHAR32 *buffer, int buffersize);
558    
559           int pcre32_copy_substring(PCRE_SPTR32 subject, int *ovector,
560                int stringcount, int stringnumber, PCRE_UCHAR32 *buffer,
561                int buffersize);
562    
563           int pcre32_get_named_substring(const pcre32 *code,
564                PCRE_SPTR32 subject, int *ovector,
565                int stringcount, PCRE_SPTR32 stringname,
566                PCRE_SPTR32 *stringptr);
567    
568           int pcre32_get_stringnumber(const pcre32 *code,
569                PCRE_SPTR32 name);
570    
571           int pcre32_get_stringtable_entries(const pcre32 *code,
572                PCRE_SPTR32 name, PCRE_UCHAR32 **first, PCRE_UCHAR32 **last);
573    
574           int pcre32_get_substring(PCRE_SPTR32 subject, int *ovector,
575                int stringcount, int stringnumber,
576                PCRE_SPTR32 *stringptr);
577    
578           int pcre32_get_substring_list(PCRE_SPTR32 subject,
579                int *ovector, int stringcount, PCRE_SPTR32 **listptr);
580    
581           void pcre32_free_substring(PCRE_SPTR32 stringptr);
582    
583           void pcre32_free_substring_list(PCRE_SPTR32 *stringptr);
584    
585    
586    PCRE 32-BIT API AUXILIARY FUNCTIONS
587    
588           pcre32_jit_stack *pcre32_jit_stack_alloc(int startsize, int maxsize);
589    
590           void pcre32_jit_stack_free(pcre32_jit_stack *stack);
591    
592           void pcre32_assign_jit_stack(pcre32_extra *extra,
593                pcre32_jit_callback callback, void *data);
594    
595           const unsigned char *pcre32_maketables(void);
596    
597           int pcre32_fullinfo(const pcre32 *code, const pcre32_extra *extra,
598                int what, void *where);
599    
600           int pcre32_refcount(pcre32 *code, int adjust);
601    
602           int pcre32_config(int what, void *where);
603    
604           const char *pcre32_version(void);
605    
606           int pcre32_pattern_to_host_byte_order(pcre32 *code,
607                pcre32_extra *extra, const unsigned char *tables);
608    
609    
610    PCRE 32-BIT API INDIRECTED FUNCTIONS
611    
612           void *(*pcre32_malloc)(size_t);
613    
614           void (*pcre32_free)(void *);
615    
616           void *(*pcre32_stack_malloc)(size_t);
617    
618           void (*pcre32_stack_free)(void *);
619    
620           int (*pcre32_callout)(pcre32_callout_block *);
621    
622    
623    PCRE 32-BIT API 32-BIT-ONLY FUNCTION
624    
625           int pcre32_utf32_to_host_byte_order(PCRE_UCHAR32 *output,
626                PCRE_SPTR32 input, int length, int *byte_order,
627                int keep_boms);
628    
629    
630    THE PCRE 32-BIT LIBRARY
631    
632           Starting  with  release  8.32, it is possible to compile a PCRE library
633           that supports 32-bit character strings, including  UTF-32  strings,  as
634           well as or instead of the original 8-bit library. This work was done by
635           Christian Persch, based on the work done  by  Zoltan  Herczeg  for  the
636           16-bit  library.  All  three  libraries contain identical sets of func-
637           tions, used in exactly the same way.  Only the names of  the  functions
638           and  the  data  types  of their arguments and results are different. To
639           avoid over-complication and reduce the documentation maintenance  load,
640           most  of  the PCRE documentation describes the 8-bit library, with only
641           occasional references to the 16-bit and  32-bit  libraries.  This  page
642           describes what is different when you use the 32-bit library.
643    
644           WARNING:  A  single  application  can  be linked with all or any of the
645           three libraries, but you must take care when processing any  particular
646           pattern  to  use  functions  from just one library. For example, if you
647           want to study a pattern that was compiled  with  pcre32_compile(),  you
648           must do so with pcre32_study(), not pcre_study(), and you must free the
649           study data with pcre32_free_study().
650    
651    
652    THE HEADER FILE
653    
654           There is only one header file, pcre.h. It contains prototypes  for  all
655           the functions in all libraries, as well as definitions of flags, struc-
656           tures, error codes, etc.
657    
658    
659    THE LIBRARY NAME
660    
661           In Unix-like systems, the 32-bit library is called libpcre32,  and  can
662           normally  be  accesss  by adding -lpcre32 to the command for linking an
663           application that uses PCRE.
664    
665    
666    STRING TYPES
667    
668           In the 8-bit library, strings are passed to PCRE library  functions  as
669           vectors  of  bytes  with  the  C  type "char *". In the 32-bit library,
670           strings are passed as vectors of unsigned 32-bit quantities. The  macro
671           PCRE_UCHAR32  specifies  an  appropriate  data type, and PCRE_SPTR32 is
672           defined as "const PCRE_UCHAR32 *". In very many environments, "unsigned
673           int" is a 32-bit data type. When PCRE is built, it defines PCRE_UCHAR32
674           as "unsigned int", but checks that it really is a 32-bit data type.  If
675           it is not, the build fails with an error message telling the maintainer
676           to modify the definition appropriately.
677    
678    
679    STRUCTURE TYPES
680    
681           The types of the opaque structures that are used  for  compiled  32-bit
682           patterns  and  JIT stacks are pcre32 and pcre32_jit_stack respectively.
683           The  type  of  the  user-accessible  structure  that  is  returned   by
684           pcre32_study()  is  pcre32_extra, and the type of the structure that is
685           used for passing data to a callout  function  is  pcre32_callout_block.
686           These structures contain the same fields, with the same names, as their
687           8-bit counterparts. The only difference is that pointers  to  character
688           strings are 32-bit instead of 8-bit types.
689    
690    
691    32-BIT FUNCTIONS
692    
693           For  every function in the 8-bit library there is a corresponding func-
694           tion in the 32-bit library with a name that starts with pcre32_ instead
695           of  pcre_.  The  prototypes are listed above. In addition, there is one
696           extra function, pcre32_utf32_to_host_byte_order(). This  is  a  utility
697           function  that converts a UTF-32 character string to host byte order if
698           necessary. The other 32-bit  functions  expect  the  strings  they  are
699           passed to be in host byte order.
700    
701           The input and output arguments of pcre32_utf32_to_host_byte_order() may
702           point to the same address, that is, conversion in place  is  supported.
703           The output buffer must be at least as long as the input.
704    
705           The  length  argument  specifies the number of 32-bit data units in the
706           input string; a negative value specifies a zero-terminated string.
707    
708           If byte_order is NULL, it is assumed that the string starts off in host
709           byte  order. This may be changed by byte-order marks (BOMs) anywhere in
710           the string (commonly as the first character).
711    
712           If byte_order is not NULL, a non-zero value of the integer to which  it
713           points  means  that  the input starts off in host byte order, otherwise
714           the opposite order is assumed. Again, BOMs in  the  string  can  change
715           this. The final byte order is passed back at the end of processing.
716    
717           If  keep_boms  is  not  zero,  byte-order  mark characters (0xfeff) are
718           copied into the output string. Otherwise they are discarded.
719    
720           The result of the function is the number of 32-bit  units  placed  into
721           the  output  buffer,  including  the  zero terminator if the string was
722           zero-terminated.
723    
724    
725    SUBJECT STRING OFFSETS
726    
727           The lengths and starting offsets of subject strings must  be  specified
728           in  32-bit  data units, and the offsets within subject strings that are
729           returned by the matching functions are in also 32-bit units rather than
730           bytes.
731    
732    
733    NAMED SUBPATTERNS
734    
735           The  name-to-number translation table that is maintained for named sub-
736           patterns uses 32-bit characters.  The  pcre32_get_stringtable_entries()
737           function returns the length of each entry in the table as the number of
738           32-bit data units.
739    
740    
741    OPTION NAMES
742    
743           There   are   two   new   general   option   names,   PCRE_UTF32    and
744           PCRE_NO_UTF32_CHECK,     which     correspond    to    PCRE_UTF8    and
745           PCRE_NO_UTF8_CHECK in the 8-bit library. In  fact,  these  new  options
746           define  the  same bits in the options word. There is a discussion about
747           the validity of UTF-32 strings in the pcreunicode page.
748    
749           For the pcre32_config() function there is an  option  PCRE_CONFIG_UTF32
750           that  returns  1  if UTF-32 support is configured, otherwise 0. If this
751           option  is  given  to  pcre_config()  or  pcre16_config(),  or  if  the
752           PCRE_CONFIG_UTF8  or  PCRE_CONFIG_UTF16  option is given to pcre32_con-
753           fig(), the result is the PCRE_ERROR_BADOPTION error.
754    
755    
756    CHARACTER CODES
757    
758           In 32-bit mode, when  PCRE_UTF32  is  not  set,  character  values  are
759           treated in the same way as in 8-bit, non UTF-8 mode, except, of course,
760           that they can range from 0 to 0x7fffffff instead of 0 to 0xff.  Charac-
761           ter  types for characters less than 0xff can therefore be influenced by
762           the locale in the same way as before.   Characters  greater  than  0xff
763           have only one case, and no "type" (such as letter or digit).
764    
765           In  UTF-32  mode,  the  character  code  is  Unicode, in the range 0 to
766           0x10ffff, with the exception of values in the range  0xd800  to  0xdfff
767           because those are "surrogate" values that are ill-formed in UTF-32.
768    
769           A  UTF-32 string can indicate its endianness by special code knows as a
770           byte-order mark (BOM). The PCRE functions do not handle this, expecting
771           strings   to   be  in  host  byte  order.  A  utility  function  called
772           pcre32_utf32_to_host_byte_order() is provided to help  with  this  (see
773           above).
774    
775    
776    ERROR NAMES
777    
778           The  error  PCRE_ERROR_BADUTF32  corresponds  to its 8-bit counterpart.
779           The error PCRE_ERROR_BADMODE is given when a compiled pattern is passed
780           to  a  function that processes patterns in the other mode, for example,
781           if a pattern compiled with pcre_compile() is passed to pcre32_exec().
782    
783           There are new error codes whose names  begin  with  PCRE_UTF32_ERR  for
784           invalid  UTF-32  strings,  corresponding to the PCRE_UTF8_ERR codes for
785           UTF-8 strings that are described in the section entitled "Reason  codes
786           for  invalid UTF-8 strings" in the main pcreapi page. The UTF-32 errors
787           are:
788    
789             PCRE_UTF32_ERR1  Surrogate character (range from 0xd800 to 0xdfff)
790             PCRE_UTF32_ERR2  Non-character
791             PCRE_UTF32_ERR3  Character > 0x10ffff
792    
793    
794    ERROR TEXTS
795    
796           If there is an error while compiling a pattern, the error text that  is
797           passed  back by pcre32_compile() or pcre32_compile2() is still an 8-bit
798           character string, zero-terminated.
799    
800    
801    CALLOUTS
802    
803           The subject and mark fields in the callout block that is  passed  to  a
804           callout function point to 32-bit vectors.
805    
806    
807    TESTING
808    
809           The  pcretest  program continues to operate with 8-bit input and output
810           files, but it can be used for testing the 32-bit library. If it is  run
811           with the command line option -32, patterns and subject strings are con-
812           verted from 8-bit to 32-bit before being passed to PCRE, and the 32-bit
813           library  functions  are used instead of the 8-bit ones. Returned 32-bit
814           strings are converted to 8-bit for output. If both the  8-bit  and  the
815           16-bit libraries were not compiled, pcretest defaults to 32-bit and the
816           -32 option is ignored.
817    
818           When PCRE is being built, the RunTest script that is  called  by  "make
819           check"  uses  the  pcretest  -C  option to discover which of the 8-bit,
820           16-bit and 32-bit libraries has been built, and runs the  tests  appro-
821           priately.
822    
823    
824    NOT SUPPORTED IN 32-BIT MODE
825    
826           Not all the features of the 8-bit library are available with the 32-bit
827           library. The C++ and POSIX wrapper functions  support  only  the  8-bit
828           library, and the pcregrep program is at present 8-bit only.
829    
830    
831    AUTHOR
832    
833           Philip Hazel
834           University Computing Service
835           Cambridge CB2 3QH, England.
836    
837    
838    REVISION
839    
840           Last updated: 12 May 2013
841           Copyright (c) 1997-2013 University of Cambridge.
842    ------------------------------------------------------------------------------
843    
844    
845    PCREBUILD(3)               Library Functions Manual               PCREBUILD(3)
846    
847    
848    
849    NAME
850           PCRE - Perl-compatible regular expressions
851    
852  PCRE BUILD-TIME OPTIONS  PCRE BUILD-TIME OPTIONS
853    
854         This  document  describes  the  optional  features  of PCRE that can be         This  document  describes  the  optional  features  of PCRE that can be
855         selected when the library is compiled. They are all selected, or  dese-         selected when the library is compiled. It assumes use of the  configure
856         lected, by providing options to the configure script that is run before         script,  where the optional features are selected or deselected by pro-
857         the make command. The complete list of  options  for  configure  (which         viding options to configure before running the make  command.  However,
858         includes  the  standard  ones such as the selection of the installation         the  same  options  can be selected in both Unix-like and non-Unix-like
859         directory) can be obtained by running         environments using the GUI facility of cmake-gui if you are using CMake
860           instead of configure to build PCRE.
861    
862           There  is a lot more information about building PCRE without using con-
863           figure (including information about using CMake or building "by  hand")
864           in  the file called NON-AUTOTOOLS-BUILD, which is part of the PCRE dis-
865           tribution. You should consult this file as well as the README  file  if
866           you are building in a non-Unix-like environment.
867    
868           The complete list of options for configure (which includes the standard
869           ones such as the  selection  of  the  installation  directory)  can  be
870           obtained by running
871    
872           ./configure --help           ./configure --help
873    
874         The following sections describe certain options whose names begin  with         The  following  sections  include  descriptions  of options whose names
875         --enable  or  --disable. These settings specify changes to the defaults         begin with --enable or --disable. These settings specify changes to the
876         for the configure command. Because of the  way  that  configure  works,         defaults  for  the configure command. Because of the way that configure
877         --enable  and  --disable  always  come  in  pairs, so the complementary         works, --enable and --disable always come in pairs, so  the  complemen-
878         option always exists as well, but as it specifies the  default,  it  is         tary  option always exists as well, but as it specifies the default, it
879         not described.         is not described.
880    
881    
882    BUILDING 8-BIT, 16-BIT AND 32-BIT LIBRARIES
883    
884           By default, a library called libpcre  is  built,  containing  functions
885           that  take  string  arguments  contained in vectors of bytes, either as
886           single-byte characters, or interpreted as UTF-8 strings. You  can  also
887           build  a  separate library, called libpcre16, in which strings are con-
888           tained in vectors of 16-bit data units and interpreted either  as  sin-
889           gle-unit characters or UTF-16 strings, by adding
890    
891             --enable-pcre16
892    
893           to the configure command. You can also build a separate library, called
894           libpcre32, in which strings are contained in  vectors  of  32-bit  data
895           units  and  interpreted  either  as  single-unit  characters  or UTF-32
896           strings, by adding
897    
898             --enable-pcre32
899    
900           to the configure command. If you do not want the 8-bit library, add
901    
902             --disable-pcre8
903    
904           as well. At least one of the three libraries must be built.  Note  that
905           the  C++  and  POSIX  wrappers are for the 8-bit library only, and that
906           pcregrep is an 8-bit program. None of these are  built  if  you  select
907           only the 16-bit or 32-bit libraries.
908    
909    
910    BUILDING SHARED AND STATIC LIBRARIES
911    
912           The  PCRE building process uses libtool to build both shared and static
913           Unix libraries by default. You can suppress one of these by adding  one
914           of
915    
916             --disable-shared
917             --disable-static
918    
919           to the configure command, as required.
920    
921    
922  C++ SUPPORT  C++ SUPPORT
923    
924         By default, the configure script will search for a C++ compiler and C++         By  default,  if the 8-bit library is being built, the configure script
925         header files. If it finds them, it automatically builds the C++ wrapper         will search for a C++ compiler and C++ header files. If it finds  them,
926         library for PCRE. You can disable this by adding         it  automatically  builds  the C++ wrapper library (which supports only
927           8-bit strings). You can disable this by adding
928    
929           --disable-cpp           --disable-cpp
930    
931         to the configure command.         to the configure command.
932    
933    
934  UTF-8 SUPPORT  UTF-8, UTF-16 AND UTF-32 SUPPORT
935    
936         To build PCRE with support for UTF-8 character strings, add         To build PCRE with support for UTF Unicode character strings, add
937    
938           --enable-utf8           --enable-utf
939    
940         to  the  configure  command.  Of  itself, this does not make PCRE treat         to the configure command. This setting applies to all three  libraries,
941         strings as UTF-8. As well as compiling PCRE with this option, you  also         adding  support  for  UTF-8 to the 8-bit library, support for UTF-16 to
942         have  have to set the PCRE_UTF8 option when you call the pcre_compile()         the 16-bit library, and  support  for  UTF-32  to  the  to  the  32-bit
943         function.         library.  There  are no separate options for enabling UTF-8, UTF-16 and
944           UTF-32 independently because that would allow ridiculous settings  such
945           as  requesting UTF-16 support while building only the 8-bit library. It
946           is not possible to build one library with UTF support and another with-
947           out  in the same configuration. (For backwards compatibility, --enable-
948           utf8 is a synonym of --enable-utf.)
949    
950           Of itself, this setting does not make  PCRE  treat  strings  as  UTF-8,
951           UTF-16  or UTF-32. As well as compiling PCRE with this option, you also
952           have have to set the PCRE_UTF8, PCRE_UTF16  or  PCRE_UTF32  option  (as
953           appropriate) when you call one of the pattern compiling functions.
954    
955           If  you  set --enable-utf when compiling in an EBCDIC environment, PCRE
956           expects its input to be either ASCII or UTF-8 (depending  on  the  run-
957           time option). It is not possible to support both EBCDIC and UTF-8 codes
958           in the same version of  the  library.  Consequently,  --enable-utf  and
959           --enable-ebcdic are mutually exclusive.
960    
961    
962  UNICODE CHARACTER PROPERTY SUPPORT  UNICODE CHARACTER PROPERTY SUPPORT
963    
964         UTF-8 support allows PCRE to process character values greater than  255         UTF  support allows the libraries to process character codepoints up to
965         in  the  strings that it handles. On its own, however, it does not pro-         0x10ffff in the strings that they handle. On its own, however, it  does
966         vide any facilities for accessing the properties of such characters. If         not provide any facilities for accessing the properties of such charac-
967         you  want  to  be able to use the pattern escapes \P, \p, and \X, which         ters. If you want to be able to use the pattern escapes \P, \p, and \X,
968         refer to Unicode character properties, you must add         which refer to Unicode character properties, you must add
969    
970           --enable-unicode-properties           --enable-unicode-properties
971    
972         to the configure command. This implies UTF-8 support, even if you  have         to  the  configure  command. This implies UTF support, even if you have
973         not explicitly requested it.         not explicitly requested it.
974    
975         Including  Unicode  property  support  adds around 90K of tables to the         Including Unicode property support adds around 30K  of  tables  to  the
976         PCRE library, approximately doubling its size. Only the  general  cate-         PCRE  library.  Only  the general category properties such as Lu and Nd
977         gory  properties  such as Lu and Nd are supported. Details are given in         are supported. Details are given in the pcrepattern documentation.
978         the pcrepattern documentation.  
979    
980    JUST-IN-TIME COMPILER SUPPORT
981    
982           Just-in-time compiler support is included in the build by specifying
983    
984             --enable-jit
985    
986           This support is available only for certain hardware  architectures.  If
987           this  option  is  set  for  an unsupported architecture, a compile time
988           error occurs.  See the pcrejit documentation for a  discussion  of  JIT
989           usage. When JIT support is enabled, pcregrep automatically makes use of
990           it, unless you add
991    
992             --disable-pcregrep-jit
993    
994           to the "configure" command.
995    
996    
997  CODE VALUE OF NEWLINE  CODE VALUE OF NEWLINE
998    
999         By default, PCRE treats character 10 (linefeed) as the newline  charac-         By default, PCRE interprets the linefeed (LF) character  as  indicating
1000         ter. This is the normal newline character on Unix-like systems. You can         the  end  of  a line. This is the normal newline character on Unix-like
1001         compile PCRE to use character 13 (carriage return) instead by adding         systems. You can compile PCRE to use carriage return (CR)  instead,  by
1002           adding
1003    
1004           --enable-newline-is-cr           --enable-newline-is-cr
1005    
1006         to the configure command. For completeness there is  also  a  --enable-         to  the  configure  command.  There  is  also  a --enable-newline-is-lf
1007         newline-is-lf  option,  which explicitly specifies linefeed as the new-         option, which explicitly specifies linefeed as the newline character.
        line character.  
1008    
1009           Alternatively, you can specify that line endings are to be indicated by
1010           the two character sequence CRLF. If you want this, add
1011    
1012  BUILDING SHARED AND STATIC LIBRARIES           --enable-newline-is-crlf
1013    
1014         The PCRE building process uses libtool to build both shared and  static         to the configure command. There is a fourth option, specified by
        Unix  libraries by default. You can suppress one of these by adding one  
        of  
1015    
1016           --disable-shared           --enable-newline-is-anycrlf
          --disable-static  
1017    
1018         to the configure command, as required.         which  causes  PCRE  to recognize any of the three sequences CR, LF, or
1019           CRLF as indicating a line ending. Finally, a fifth option, specified by
1020    
1021             --enable-newline-is-any
1022    
1023  POSIX MALLOC USAGE         causes PCRE to recognize any Unicode newline sequence.
1024    
1025         When PCRE is called through the POSIX interface (see the pcreposix doc-         Whatever line ending convention is selected when PCRE is built  can  be
1026         umentation),  additional  working  storage  is required for holding the         overridden  when  the library functions are called. At build time it is
1027         pointers to capturing substrings, because PCRE requires three  integers         conventional to use the standard for your operating system.
        per  substring,  whereas  the POSIX interface provides only two. If the  
        number of expected substrings is small, the wrapper function uses space  
        on the stack, because this is faster than using malloc() for each call.  
        The default threshold above which the stack is no longer used is 10; it  
        can be changed by adding a setting such as  
1028    
          --with-posix-malloc-threshold=20  
1029    
1030         to the configure command.  WHAT \R MATCHES
1031    
1032           By default, the sequence \R in a pattern matches  any  Unicode  newline
1033           sequence,  whatever  has  been selected as the line ending sequence. If
1034           you specify
1035    
1036  LIMITING PCRE RESOURCE USAGE           --enable-bsr-anycrlf
1037    
1038         Internally,  PCRE has a function called match(), which it calls repeat-         the default is changed so that \R matches only CR, LF, or  CRLF.  What-
1039         edly  (possibly  recursively)  when  matching  a   pattern   with   the         ever  is selected when PCRE is built can be overridden when the library
1040         pcre_exec()  function.  By controlling the maximum number of times this         functions are called.
        function may be called during a single matching operation, a limit  can  
        be  placed  on  the resources used by a single call to pcre_exec(). The  
        limit can be changed at run time, as described in the pcreapi  documen-  
        tation.  The default is 10 million, but this can be changed by adding a  
        setting such as  
1041    
          --with-match-limit=500000  
1042    
1043         to  the  configure  command.  This  setting  has  no  effect   on   the  POSIX MALLOC USAGE
1044         pcre_dfa_exec() matching function.  
1045           When the 8-bit library is called through the POSIX interface  (see  the
1046           pcreposix  documentation),  additional  working storage is required for
1047           holding the pointers to capturing  substrings,  because  PCRE  requires
1048           three integers per substring, whereas the POSIX interface provides only
1049           two. If the number of expected substrings is small, the  wrapper  func-
1050           tion  uses  space  on the stack, because this is faster than using mal-
1051           loc() for each call. The default threshold above which the stack is  no
1052           longer used is 10; it can be changed by adding a setting such as
1053    
1054             --with-posix-malloc-threshold=20
1055    
1056           to the configure command.
1057    
1058    
1059  HANDLING VERY LARGE PATTERNS  HANDLING VERY LARGE PATTERNS
1060    
1061         Within  a  compiled  pattern,  offset values are used to point from one         Within  a  compiled  pattern,  offset values are used to point from one
1062         part to another (for example, from an opening parenthesis to an  alter-         part to another (for example, from an opening parenthesis to an  alter-
1063         nation  metacharacter).  By default, two-byte values are used for these         nation  metacharacter).  By default, in the 8-bit and 16-bit libraries,
1064         offsets, leading to a maximum size for a  compiled  pattern  of  around         two-byte values are used for these offsets, leading to a  maximum  size
1065         64K.  This  is sufficient to handle all but the most gigantic patterns.         for  a compiled pattern of around 64K. This is sufficient to handle all
1066         Nevertheless, some people do want to process enormous patterns,  so  it         but the most gigantic patterns.  Nevertheless, some people do  want  to
1067         is  possible  to compile PCRE to use three-byte or four-byte offsets by         process  truly  enormous patterns, so it is possible to compile PCRE to
1068         adding a setting such as         use three-byte or four-byte offsets by adding a setting such as
1069    
1070           --with-link-size=3           --with-link-size=3
1071    
1072         to the configure command. The value given must be 2,  3,  or  4.  Using         to the configure command. The value given must be 2, 3, or 4.  For  the
1073         longer  offsets slows down the operation of PCRE because it has to load         16-bit  library,  a  value of 3 is rounded up to 4. In these libraries,
1074         additional bytes when handling them.         using longer offsets slows down the operation of PCRE because it has to
1075           load  additional  data  when  handling them. For the 32-bit library the
1076         If you build PCRE with an increased link size, test 2 (and  test  5  if         value is always 4 and cannot be overridden; the value  of  --with-link-
1077         you  are using UTF-8) will fail. Part of the output of these tests is a         size is ignored.
        representation of the compiled pattern, and this changes with the  link  
        size.  
1078    
1079    
1080  AVOIDING EXCESSIVE STACK USAGE  AVOIDING EXCESSIVE STACK USAGE
# Line 365  AVOIDING EXCESSIVE STACK USAGE Line 1083  AVOIDING EXCESSIVE STACK USAGE
1083         ing by making recursive calls to an internal function  called  match().         ing by making recursive calls to an internal function  called  match().
1084         In  environments  where  the size of the stack is limited, this can se-         In  environments  where  the size of the stack is limited, this can se-
1085         verely limit PCRE's operation. (The Unix environment does  not  usually         verely limit PCRE's operation. (The Unix environment does  not  usually
1086         suffer  from  this  problem.)  An alternative approach that uses memory         suffer from this problem, but it may sometimes be necessary to increase
1087         from the heap to remember data, instead  of  using  recursive  function         the maximum stack size.  There is a discussion in the  pcrestack  docu-
1088         calls,  has been implemented to work round this problem. If you want to         mentation.)  An alternative approach to recursion that uses memory from
1089         build a version of PCRE that works this way, add         the heap to remember data, instead of using recursive  function  calls,
1090           has  been  implemented to work round the problem of limited stack size.
1091           If you want to build a version of PCRE that works this way, add
1092    
1093           --disable-stack-for-recursion           --disable-stack-for-recursion
1094    
1095         to the configure command. With this configuration, PCRE  will  use  the         to the configure command. With this configuration, PCRE  will  use  the
1096         pcre_stack_malloc  and pcre_stack_free variables to call memory manage-         pcre_stack_malloc  and pcre_stack_free variables to call memory manage-
1097         ment functions. Separate functions are provided because  the  usage  is         ment functions. By default these point to malloc() and free(), but  you
1098         very  predictable:  the  block sizes requested are always the same, and         can replace the pointers so that your own functions are used instead.
1099         the blocks are always freed in reverse order. A calling  program  might  
1100         be  able  to implement optimized functions that perform better than the         Separate  functions  are  provided  rather  than  using pcre_malloc and
1101         standard malloc() and  free()  functions.  PCRE  runs  noticeably  more         pcre_free because the  usage  is  very  predictable:  the  block  sizes
1102         slowly when built in this way. This option affects only the pcre_exec()         requested  are  always  the  same,  and  the blocks are always freed in
1103         function; it is not relevant for the the pcre_dfa_exec() function.         reverse order. A calling program might be able to  implement  optimized
1104           functions  that  perform  better  than  malloc()  and free(). PCRE runs
1105           noticeably more slowly when built in this way. This option affects only
1106           the pcre_exec() function; it is not relevant for pcre_dfa_exec().
1107    
1108    
1109    LIMITING PCRE RESOURCE USAGE
1110    
1111           Internally,  PCRE has a function called match(), which it calls repeat-
1112           edly  (sometimes  recursively)  when  matching  a  pattern   with   the
1113           pcre_exec()  function.  By controlling the maximum number of times this
1114           function may be called during a single matching operation, a limit  can
1115           be  placed  on  the resources used by a single call to pcre_exec(). The
1116           limit can be changed at run time, as described in the pcreapi  documen-
1117           tation.  The default is 10 million, but this can be changed by adding a
1118           setting such as
1119    
1120             --with-match-limit=500000
1121    
1122           to  the  configure  command.  This  setting  has  no  effect   on   the
1123           pcre_dfa_exec() matching function.
1124    
1125           In  some  environments  it is desirable to limit the depth of recursive
1126           calls of match() more strictly than the total number of calls, in order
1127           to  restrict  the maximum amount of stack (or heap, if --disable-stack-
1128           for-recursion is specified) that is used. A second limit controls this;
1129           it  defaults  to  the  value  that is set for --with-match-limit, which
1130           imposes no additional constraints. However, you can set a  lower  limit
1131           by adding, for example,
1132    
1133             --with-match-limit-recursion=10000
1134    
1135           to  the  configure  command.  This  value can also be overridden at run
1136           time.
1137    
1138    
1139    CREATING CHARACTER TABLES AT BUILD TIME
1140    
1141           PCRE uses fixed tables for processing characters whose code values  are
1142           less  than 256. By default, PCRE is built with a set of tables that are
1143           distributed in the file pcre_chartables.c.dist. These  tables  are  for
1144           ASCII codes only. If you add
1145    
1146             --enable-rebuild-chartables
1147    
1148           to  the  configure  command, the distributed tables are no longer used.
1149           Instead, a program called dftables is compiled and  run.  This  outputs
1150           the source for new set of tables, created in the default locale of your
1151           C run-time system. (This method of replacing the tables does  not  work
1152           if  you are cross compiling, because dftables is run on the local host.
1153           If you need to create alternative tables when cross compiling, you will
1154           have to do so "by hand".)
1155    
1156    
1157  USING EBCDIC CODE  USING EBCDIC CODE
1158    
1159         PCRE assumes by default that it will run in an  environment  where  the         PCRE  assumes  by  default that it will run in an environment where the
1160         character  code  is  ASCII  (or Unicode, which is a superset of ASCII).         character code is ASCII (or Unicode, which is  a  superset  of  ASCII).
1161         PCRE can, however, be compiled to  run  in  an  EBCDIC  environment  by         This  is  the  case for most computer operating systems. PCRE can, how-
1162         adding         ever, be compiled to run in an EBCDIC environment by adding
1163    
1164           --enable-ebcdic           --enable-ebcdic
1165    
1166         to the configure command.         to the configure command. This setting implies --enable-rebuild-charta-
1167           bles.  You  should  only  use  it if you know that you are in an EBCDIC
1168           environment (for example,  an  IBM  mainframe  operating  system).  The
1169           --enable-ebcdic option is incompatible with --enable-utf.
1170    
1171           The EBCDIC character that corresponds to an ASCII LF is assumed to have
1172           the value 0x15 by default. However, in some EBCDIC  environments,  0x25
1173           is used. In such an environment you should use
1174    
1175             --enable-ebcdic-nl25
1176    
1177           as well as, or instead of, --enable-ebcdic. The EBCDIC character for CR
1178           has the same value as in ASCII, namely, 0x0d.  Whichever  of  0x15  and
1179           0x25 is not chosen as LF is made to correspond to the Unicode NEL char-
1180           acter (which, in Unicode, is 0x85).
1181    
1182           The options that select newline behaviour, such as --enable-newline-is-
1183           cr, and equivalent run-time options, refer to these character values in
1184           an EBCDIC environment.
1185    
1186    
1187    PCREGREP OPTIONS FOR COMPRESSED FILE SUPPORT
1188    
1189           By default, pcregrep reads all files as plain text. You can build it so
1190           that it recognizes files whose names end in .gz or .bz2, and reads them
1191           with libz or libbz2, respectively, by adding one or both of
1192    
1193             --enable-pcregrep-libz
1194             --enable-pcregrep-libbz2
1195    
1196           to the configure command. These options naturally require that the rel-
1197           evant  libraries  are installed on your system. Configuration will fail
1198           if they are not.
1199    
1200    
1201    PCREGREP BUFFER SIZE
1202    
1203           pcregrep uses an internal buffer to hold a "window" on the file  it  is
1204           scanning, in order to be able to output "before" and "after" lines when
1205           it finds a match. The size of the buffer is controlled by  a  parameter
1206           whose default value is 20K. The buffer itself is three times this size,
1207           but because of the way it is used for holding "before" lines, the long-
1208           est  line  that  is guaranteed to be processable is the parameter size.
1209           You can change the default parameter value by adding, for example,
1210    
1211             --with-pcregrep-bufsize=50K
1212    
1213           to the configure command. The caller of pcregrep can, however, override
1214           this value by specifying a run-time option.
1215    
1216    
1217    PCRETEST OPTION FOR LIBREADLINE SUPPORT
1218    
1219           If you add
1220    
1221             --enable-pcretest-libreadline
1222    
1223           to  the  configure  command,  pcretest  is  linked with the libreadline
1224           library, and when its input is from a terminal, it reads it  using  the
1225           readline() function. This provides line-editing and history facilities.
1226           Note that libreadline is GPL-licensed, so if you distribute a binary of
1227           pcretest linked in this way, there may be licensing issues.
1228    
1229           Setting  this  option  causes  the -lreadline option to be added to the
1230           pcretest build. In many operating environments with  a  sytem-installed
1231           libreadline this is sufficient. However, in some environments (e.g.  if
1232           an unmodified distribution version of readline is in use),  some  extra
1233           configuration  may  be necessary. The INSTALL file for libreadline says
1234           this:
1235    
1236             "Readline uses the termcap functions, but does not link with the
1237             termcap or curses library itself, allowing applications which link
1238             with readline the to choose an appropriate library."
1239    
1240           If your environment has not been set up so that an appropriate  library
1241           is automatically included, you may need to add something like
1242    
1243             LIBS="-ncurses"
1244    
1245           immediately before the configure command.
1246    
1247    
1248    DEBUGGING WITH VALGRIND SUPPORT
1249    
1250           By adding the
1251    
1252             --enable-valgrind
1253    
1254           option  to to the configure command, PCRE will use valgrind annotations
1255           to mark certain memory regions as  unaddressable.  This  allows  it  to
1256           detect invalid memory accesses, and is mostly useful for debugging PCRE
1257           itself.
1258    
1259    
1260    CODE COVERAGE REPORTING
1261    
1262           If your C compiler is gcc, you can build a version  of  PCRE  that  can
1263           generate a code coverage report for its test suite. To enable this, you
1264           must install lcov version 1.6 or above. Then specify
1265    
1266             --enable-coverage
1267    
1268           to the configure command and build PCRE in the usual way.
1269    
1270           Note that using ccache (a caching C compiler) is incompatible with code
1271           coverage  reporting. If you have configured ccache to run automatically
1272           on your system, you must set the environment variable
1273    
1274             CCACHE_DISABLE=1
1275    
1276           before running make to build PCRE, so that ccache is not used.
1277    
1278           When --enable-coverage is used,  the  following  addition  targets  are
1279           added to the Makefile:
1280    
1281             make coverage
1282    
1283           This  creates  a  fresh  coverage report for the PCRE test suite. It is
1284           equivalent to running "make coverage-reset", "make  coverage-baseline",
1285           "make check", and then "make coverage-report".
1286    
1287             make coverage-reset
1288    
1289           This zeroes the coverage counters, but does nothing else.
1290    
1291             make coverage-baseline
1292    
1293           This captures baseline coverage information.
1294    
1295             make coverage-report
1296    
1297           This creates the coverage report.
1298    
1299             make coverage-clean-report
1300    
1301           This  removes the generated coverage report without cleaning the cover-
1302           age data itself.
1303    
1304             make coverage-clean-data
1305    
1306           This removes the captured coverage data without removing  the  coverage
1307           files created at compile time (*.gcno).
1308    
1309             make coverage-clean
1310    
1311           This  cleans all coverage data including the generated coverage report.
1312           For more information about code coverage, see the gcov and  lcov  docu-
1313           mentation.
1314    
1315    
1316    SEE ALSO
1317    
1318           pcreapi(3), pcre16, pcre32, pcre_config(3).
1319    
1320    
1321    AUTHOR
1322    
1323           Philip Hazel
1324           University Computing Service
1325           Cambridge CB2 3QH, England.
1326    
1327    
1328    REVISION
1329    
1330  Last updated: 15 August 2005         Last updated: 30 October 2012
1331  Copyright (c) 1997-2005 University of Cambridge.         Copyright (c) 1997-2012 University of Cambridge.
1332  ------------------------------------------------------------------------------  ------------------------------------------------------------------------------
1333    
1334    
1335    PCREMATCHING(3)            Library Functions Manual            PCREMATCHING(3)
1336    
1337    
 PCREMATCHING(3)                                                PCREMATCHING(3)  
   
1338    
1339  NAME  NAME
1340         PCRE - Perl-compatible regular expressions         PCRE - Perl-compatible regular expressions
1341    
   
1342  PCRE MATCHING ALGORITHMS  PCRE MATCHING ALGORITHMS
1343    
1344         This document describes the two different algorithms that are available         This document describes the two different algorithms that are available
1345         in PCRE for matching a compiled regular expression against a given sub-         in PCRE for matching a compiled regular expression against a given sub-
1346         ject  string.  The  "standard"  algorithm  is  the  one provided by the         ject  string.  The  "standard"  algorithm  is  the  one provided by the
1347         pcre_exec() function.  This works in the same was  as  Perl's  matching         pcre_exec(), pcre16_exec() and pcre32_exec() functions. These  work  in
1348         function, and provides a Perl-compatible matching operation.         the  same as as Perl's matching function, and provide a Perl-compatible
1349           matching  operation.   The  just-in-time  (JIT)  optimization  that  is
1350         An  alternative  algorithm is provided by the pcre_dfa_exec() function;         described  in  the pcrejit documentation is compatible with these func-
1351         this operates in a different way, and is not  Perl-compatible.  It  has         tions.
1352         advantages  and disadvantages compared with the standard algorithm, and  
1353         these are described below.         An  alternative  algorithm  is   provided   by   the   pcre_dfa_exec(),
1354           pcre16_dfa_exec()  and  pcre32_dfa_exec()  functions; they operate in a
1355           different way, and are not Perl-compatible. This alternative has advan-
1356           tages and disadvantages compared with the standard algorithm, and these
1357           are described below.
1358    
1359         When there is only one possible way in which a given subject string can         When there is only one possible way in which a given subject string can
1360         match  a pattern, the two algorithms give the same answer. A difference         match  a pattern, the two algorithms give the same answer. A difference
# Line 431  PCRE MATCHING ALGORITHMS Line 1368  PCRE MATCHING ALGORITHMS
1368           <something> <something else> <something further>           <something> <something else> <something further>
1369    
1370         there are three possible answers. The standard algorithm finds only one         there are three possible answers. The standard algorithm finds only one
1371         of them, whereas the DFA algorithm finds all three.         of them, whereas the alternative algorithm finds all three.
1372    
1373    
1374  REGULAR EXPRESSIONS AS TREES  REGULAR EXPRESSIONS AS TREES
# Line 440  REGULAR EXPRESSIONS AS TREES Line 1377  REGULAR EXPRESSIONS AS TREES
1377         resented  as  a  tree structure. An unlimited repetition in the pattern         resented  as  a  tree structure. An unlimited repetition in the pattern
1378         makes the tree of infinite size, but it is still a tree.  Matching  the         makes the tree of infinite size, but it is still a tree.  Matching  the
1379         pattern  to a given subject string (from a given starting point) can be         pattern  to a given subject string (from a given starting point) can be
1380         thought of as a search of the tree.  There are  two  standard  ways  to         thought of as a search of the tree.  There are two  ways  to  search  a
1381         search  a  tree: depth-first and breadth-first, and these correspond to         tree:  depth-first  and  breadth-first, and these correspond to the two
1382         the two matching algorithms provided by PCRE.         matching algorithms provided by PCRE.
1383    
1384    
1385  THE STANDARD MATCHING ALGORITHM  THE STANDARD MATCHING ALGORITHM
1386    
1387         In the terminology of Jeffrey Friedl's book Mastering  Regular  Expres-         In the terminology of Jeffrey Friedl's book "Mastering Regular  Expres-
1388         sions,  the  standard  algorithm  is  an "NFA algorithm". It conducts a         sions",  the  standard  algorithm  is an "NFA algorithm". It conducts a
1389         depth-first search of the pattern tree. That is, it  proceeds  along  a         depth-first search of the pattern tree. That is, it  proceeds  along  a
1390         single path through the tree, checking that the subject matches what is         single path through the tree, checking that the subject matches what is
1391         required. When there is a mismatch, the algorithm  tries  any  alterna-         required. When there is a mismatch, the algorithm  tries  any  alterna-
# Line 472  THE STANDARD MATCHING ALGORITHM Line 1409  THE STANDARD MATCHING ALGORITHM
1409         This provides support for capturing parentheses and back references.         This provides support for capturing parentheses and back references.
1410    
1411    
1412  THE DFA MATCHING ALGORITHM  THE ALTERNATIVE MATCHING ALGORITHM
1413    
1414         DFA stands for "deterministic finite automaton", but you do not need to         This algorithm conducts a breadth-first search of  the  tree.  Starting
1415         understand the origins of that name. This algorithm conducts a breadth-         from  the  first  matching  point  in the subject, it scans the subject
1416         first search of the tree. Starting from the first matching point in the         string from left to right, once, character by character, and as it does
1417         subject,  it scans the subject string from left to right, once, charac-         this,  it remembers all the paths through the tree that represent valid
1418         ter by character, and as it does  this,  it  remembers  all  the  paths         matches. In Friedl's terminology, this is a kind  of  "DFA  algorithm",
1419         through the tree that represent valid matches.         though  it is not implemented as a traditional finite state machine (it
1420           keeps multiple states active simultaneously).
1421         The  scan  continues until either the end of the subject is reached, or  
1422         there are no more unterminated paths. At this point,  terminated  paths         Although the general principle of this matching algorithm  is  that  it
1423         represent  the different matching possibilities (if there are none, the         scans  the subject string only once, without backtracking, there is one
1424         match has failed).  Thus, if there is more  than  one  possible  match,         exception: when a lookaround assertion is encountered,  the  characters
1425           following  or  preceding  the  current  point  have to be independently
1426           inspected.
1427    
1428           The scan continues until either the end of the subject is  reached,  or
1429           there  are  no more unterminated paths. At this point, terminated paths
1430           represent the different matching possibilities (if there are none,  the
1431           match  has  failed).   Thus,  if there is more than one possible match,
1432         this algorithm finds all of them, and in particular, it finds the long-         this algorithm finds all of them, and in particular, it finds the long-
1433         est. In PCRE, there is an option to stop the algorithm after the  first         est.  The  matches are returned in decreasing order of length. There is
1434         match (which is necessarily the shortest) has been found.         an option to stop the algorithm after the first match (which is  neces-
1435           sarily the shortest) is found.
1436    
1437         Note that all the matches that are found start at the same point in the         Note that all the matches that are found start at the same point in the
1438         subject. If the pattern         subject. If the pattern
1439    
1440           cat(er(pillar)?)           cat(er(pillar)?)?
1441    
1442         is matched against the string "the caterpillar catchment",  the  result         is matched against the string "the caterpillar catchment",  the  result
1443         will  be the three strings "cat", "cater", and "caterpillar" that start         will  be the three strings "caterpillar", "cater", and "cat" that start
1444         at the fourth character of the subject. The algorithm does not automat-         at the fifth character of the subject. The algorithm does not automati-
1445         ically move on to find matches that start at later positions.         cally move on to find matches that start at later positions.
1446    
1447         There are a number of features of PCRE regular expressions that are not         There are a number of features of PCRE regular expressions that are not
1448         supported by the DFA matching algorithm. They are as follows:         supported by the alternative matching algorithm. They are as follows:
1449    
1450         1. Because the algorithm finds all  possible  matches,  the  greedy  or         1. Because the algorithm finds all  possible  matches,  the  greedy  or
1451         ungreedy  nature  of repetition quantifiers is not relevant. Greedy and         ungreedy  nature  of repetition quantifiers is not relevant. Greedy and
1452         ungreedy quantifiers are treated in exactly the same way.         ungreedy quantifiers are treated in exactly the same way. However, pos-
1453           sessive  quantifiers can make a difference when what follows could also
1454           match what is quantified, for example in a pattern like this:
1455    
1456             ^a++\w!
1457    
1458           This pattern matches "aaab!" but not "aaa!", which would be matched  by
1459           a  non-possessive quantifier. Similarly, if an atomic group is present,
1460           it is matched as if it were a standalone pattern at the current  point,
1461           and  the  longest match is then "locked in" for the rest of the overall
1462           pattern.
1463    
1464         2. When dealing with multiple paths through the tree simultaneously, it         2. When dealing with multiple paths through the tree simultaneously, it
1465         is  not  straightforward  to  keep track of captured substrings for the         is  not  straightforward  to  keep track of captured substrings for the
# Line 516  THE DFA MATCHING ALGORITHM Line 1471  THE DFA MATCHING ALGORITHM
1471         tern are not supported, and cause errors if encountered.         tern are not supported, and cause errors if encountered.
1472    
1473         4.  For  the same reason, conditional expressions that use a backrefer-         4.  For  the same reason, conditional expressions that use a backrefer-
1474         ence as the condition are not supported.         ence as the condition or test for a specific group  recursion  are  not
1475           supported.
1476    
1477         5. Callouts are supported, but the value of the  capture_top  field  is         5.  Because  many  paths  through the tree may be active, the \K escape
1478           sequence, which resets the start of the match when encountered (but may
1479           be  on  some  paths  and not on others), is not supported. It causes an
1480           error if encountered.
1481    
1482           6. Callouts are supported, but the value of the  capture_top  field  is
1483         always 1, and the value of the capture_last field is always -1.         always 1, and the value of the capture_last field is always -1.
1484    
1485         6.  The \C escape sequence, which (in the standard algorithm) matches a         7.  The  \C  escape  sequence, which (in the standard algorithm) always
1486         single byte, even in UTF-8 mode, is not supported because the DFA algo-         matches a single data unit, even in UTF-8, UTF-16 or UTF-32  modes,  is
1487         rithm moves through the subject string one character at a time, for all         not  supported  in these modes, because the alternative algorithm moves
1488         active paths through the tree.         through the subject string one character (not data unit) at a time, for
1489           all active paths through the tree.
1490    
1491           8.  Except for (*FAIL), the backtracking control verbs such as (*PRUNE)
1492           are not supported. (*FAIL) is supported, and  behaves  like  a  failing
1493           negative assertion.
1494    
1495    
1496  ADVANTAGES OF THE DFA ALGORITHM  ADVANTAGES OF THE ALTERNATIVE ALGORITHM
1497    
1498         Using the DFA matching algorithm provides the following advantages:         Using  the alternative matching algorithm provides the following advan-
1499           tages:
1500    
1501         1. All possible matches (at a single point in the subject) are automat-         1. All possible matches (at a single point in the subject) are automat-
1502         ically  found,  and  in particular, the longest match is found. To find         ically  found,  and  in particular, the longest match is found. To find
1503         more than one match using the standard algorithm, you have to do kludgy         more than one match using the standard algorithm, you have to do kludgy
1504         things with callouts.         things with callouts.
1505    
1506         2.  There is much better support for partial matching. The restrictions         2.  Because  the  alternative  algorithm  scans the subject string just
1507         on the content of the pattern that apply when using the standard  algo-         once, and never needs to backtrack (except for lookbehinds), it is pos-
1508         rithm  for partial matching do not apply to the DFA algorithm. For non-         sible  to  pass  very  long subject strings to the matching function in
1509         anchored patterns, the starting position of a partial match  is  avail-         several pieces, checking for partial matching each time. Although it is
1510         able.         possible  to  do multi-segment matching using the standard algorithm by
1511           retaining partially matched substrings, it  is  more  complicated.  The
1512           pcrepartial  documentation  gives  details of partial matching and dis-
1513           cusses multi-segment matching.
1514    
        3.  Because  the  DFA algorithm scans the subject string just once, and  
        never needs to backtrack, it is possible  to  pass  very  long  subject  
        strings  to  the matching function in several pieces, checking for par-  
        tial matching each time.  
1515    
1516    DISADVANTAGES OF THE ALTERNATIVE ALGORITHM
1517    
1518  DISADVANTAGES OF THE DFA ALGORITHM         The alternative algorithm suffers from a number of disadvantages:
   
        The DFA algorithm suffers from a number of disadvantages:  
1519    
1520         1. It is substantially slower than  the  standard  algorithm.  This  is         1. It is substantially slower than  the  standard  algorithm.  This  is
1521         partly  because  it has to search for all possible matches, but is also         partly  because  it has to search for all possible matches, but is also
# Line 558  DISADVANTAGES OF THE DFA ALGORITHM Line 1523  DISADVANTAGES OF THE DFA ALGORITHM
1523    
1524         2. Capturing parentheses and back references are not supported.         2. Capturing parentheses and back references are not supported.
1525    
1526         3. The "atomic group" feature of PCRE regular expressions is supported,         3. Although atomic groups are supported, their use does not provide the
1527         but  does not provide the advantage that it does for the standard algo-         performance advantage that it does for the standard algorithm.
        rithm.  
1528    
 Last updated: 28 February 2005  
 Copyright (c) 1997-2005 University of Cambridge.  
 ------------------------------------------------------------------------------  
1529    
1530    AUTHOR
1531    
1532           Philip Hazel
1533           University Computing Service
1534           Cambridge CB2 3QH, England.
1535    
1536    
1537    REVISION
1538    
1539           Last updated: 08 January 2012
1540           Copyright (c) 1997-2012 University of Cambridge.
1541    ------------------------------------------------------------------------------
1542    
1543    
1544    PCREAPI(3)                 Library Functions Manual                 PCREAPI(3)
1545    
 PCREAPI(3)                                                          PCREAPI(3)  
1546    
1547    
1548  NAME  NAME
1549         PCRE - Perl-compatible regular expressions         PCRE - Perl-compatible regular expressions
1550    
1551           #include <pcre.h>
1552    
 PCRE NATIVE API  
1553    
1554         #include <pcre.h>  PCRE NATIVE API BASIC FUNCTIONS
1555    
1556         pcre *pcre_compile(const char *pattern, int options,         pcre *pcre_compile(const char *pattern, int options,
1557              const char **errptr, int *erroffset,              const char **errptr, int *erroffset,
# Line 590  PCRE NATIVE API Line 1565  PCRE NATIVE API
1565         pcre_extra *pcre_study(const pcre *code, int options,         pcre_extra *pcre_study(const pcre *code, int options,
1566              const char **errptr);              const char **errptr);
1567    
1568           void pcre_free_study(pcre_extra *extra);
1569    
1570         int pcre_exec(const pcre *code, const pcre_extra *extra,         int pcre_exec(const pcre *code, const pcre_extra *extra,
1571              const char *subject, int length, int startoffset,              const char *subject, int length, int startoffset,
1572              int options, int *ovector, int ovecsize);              int options, int *ovector, int ovecsize);
# Line 599  PCRE NATIVE API Line 1576  PCRE NATIVE API
1576              int options, int *ovector, int ovecsize,              int options, int *ovector, int ovecsize,
1577              int *workspace, int wscount);              int *workspace, int wscount);
1578    
1579    
1580    PCRE NATIVE API STRING EXTRACTION FUNCTIONS
1581    
1582         int pcre_copy_named_substring(const pcre *code,         int pcre_copy_named_substring(const pcre *code,
1583              const char *subject, int *ovector,              const char *subject, int *ovector,
1584              int stringcount, const char *stringname,              int stringcount, const char *stringname,
# Line 616  PCRE NATIVE API Line 1596  PCRE NATIVE API
1596         int pcre_get_stringnumber(const pcre *code,         int pcre_get_stringnumber(const pcre *code,
1597              const char *name);              const char *name);
1598    
1599           int pcre_get_stringtable_entries(const pcre *code,
1600                const char *name, char **first, char **last);
1601    
1602         int pcre_get_substring(const char *subject, int *ovector,         int pcre_get_substring(const char *subject, int *ovector,
1603              int stringcount, int stringnumber,              int stringcount, int stringnumber,
1604              const char **stringptr);              const char **stringptr);
# Line 627  PCRE NATIVE API Line 1610  PCRE NATIVE API
1610    
1611         void pcre_free_substring_list(const char **stringptr);         void pcre_free_substring_list(const char **stringptr);
1612    
1613    
1614    PCRE NATIVE API AUXILIARY FUNCTIONS
1615    
1616           int pcre_jit_exec(const pcre *code, const pcre_extra *extra,
1617                const char *subject, int length, int startoffset,
1618                int options, int *ovector, int ovecsize,
1619                pcre_jit_stack *jstack);
1620    
1621           pcre_jit_stack *pcre_jit_stack_alloc(int startsize, int maxsize);
1622    
1623           void pcre_jit_stack_free(pcre_jit_stack *stack);
1624    
1625           void pcre_assign_jit_stack(pcre_extra *extra,
1626                pcre_jit_callback callback, void *data);
1627    
1628         const unsigned char *pcre_maketables(void);         const unsigned char *pcre_maketables(void);
1629    
1630         int pcre_fullinfo(const pcre *code, const pcre_extra *extra,         int pcre_fullinfo(const pcre *code, const pcre_extra *extra,
1631              int what, void *where);              int what, void *where);
1632    
        int pcre_info(const pcre *code, int *optptr, int *firstcharptr);  
   
1633         int pcre_refcount(pcre *code, int adjust);         int pcre_refcount(pcre *code, int adjust);
1634    
1635         int pcre_config(int what, void *where);         int pcre_config(int what, void *where);
1636    
1637         char *pcre_version(void);         const char *pcre_version(void);
1638    
1639           int pcre_pattern_to_host_byte_order(pcre *code,
1640                pcre_extra *extra, const unsigned char *tables);
1641    
1642    
1643    PCRE NATIVE API INDIRECTED FUNCTIONS
1644    
1645         void *(*pcre_malloc)(size_t);         void *(*pcre_malloc)(size_t);
1646    
# Line 651  PCRE NATIVE API Line 1653  PCRE NATIVE API
1653         int (*pcre_callout)(pcre_callout_block *);         int (*pcre_callout)(pcre_callout_block *);
1654    
1655    
1656    PCRE 8-BIT, 16-BIT, AND 32-BIT LIBRARIES
1657    
1658           As  well  as  support  for  8-bit character strings, PCRE also supports
1659           16-bit strings (from release 8.30) and  32-bit  strings  (from  release
1660           8.32),  by means of two additional libraries. They can be built as well
1661           as, or instead of, the 8-bit library. To avoid too  much  complication,
1662           this  document describes the 8-bit versions of the functions, with only
1663           occasional references to the 16-bit and 32-bit libraries.
1664    
1665           The 16-bit and 32-bit functions operate in the same way as their  8-bit
1666           counterparts;  they  just  use different data types for their arguments
1667           and results, and their names start with pcre16_ or pcre32_  instead  of
1668           pcre_.  For  every  option  that  has  UTF8  in  its name (for example,
1669           PCRE_UTF8), there are corresponding 16-bit and 32-bit names  with  UTF8
1670           replaced by UTF16 or UTF32, respectively. This facility is in fact just
1671           cosmetic; the 16-bit and 32-bit option names define the same  bit  val-
1672           ues.
1673    
1674           References to bytes and UTF-8 in this document should be read as refer-
1675           ences to 16-bit data units and UTF-16 when using the 16-bit library, or
1676           32-bit  data  units  and  UTF-32  when using the 32-bit library, unless
1677           specified otherwise.  More details of the specific differences for  the
1678           16-bit and 32-bit libraries are given in the pcre16 and pcre32 pages.
1679    
1680    
1681  PCRE API OVERVIEW  PCRE API OVERVIEW
1682    
1683         PCRE has its own native API, which is described in this document. There         PCRE has its own native API, which is described in this document. There
1684         is also a set of wrapper functions that correspond to the POSIX regular         are also some wrapper functions (for the 8-bit library only) that  cor-
1685         expression  API.  These  are  described in the pcreposix documentation.         respond  to  the  POSIX  regular  expression  API, but they do not give
1686         Both of these APIs define a set of C function calls. A C++  wrapper  is         access to all the functionality. They are described  in  the  pcreposix
1687         distributed with PCRE. It is documented in the pcrecpp page.         documentation.  Both  of these APIs define a set of C function calls. A
1688           C++ wrapper (again for the 8-bit library only) is also distributed with
1689           PCRE. It is documented in the pcrecpp page.
1690    
1691         The  native  API  C  function prototypes are defined in the header file         The  native  API  C  function prototypes are defined in the header file
1692         pcre.h, and on Unix systems the library itself is called  libpcre.   It         pcre.h, and on Unix-like systems the (8-bit) library itself  is  called
1693         can normally be accessed by adding -lpcre to the command for linking an         libpcre.  It  can  normally be accessed by adding -lpcre to the command
1694         application  that  uses  PCRE.  The  header  file  defines  the  macros         for linking an application that uses PCRE. The header file defines  the
1695         PCRE_MAJOR  and  PCRE_MINOR to contain the major and minor release num-         macros PCRE_MAJOR and PCRE_MINOR to contain the major and minor release
1696         bers for the library.  Applications can use these  to  include  support         numbers for the library. Applications can use these to include  support
1697         for different releases of PCRE.         for different releases of PCRE.
1698    
1699           In a Windows environment, if you want to statically link an application
1700           program against a non-dll pcre.a  file,  you  must  define  PCRE_STATIC
1701           before  including  pcre.h or pcrecpp.h, because otherwise the pcre_mal-
1702           loc()   and   pcre_free()   exported   functions   will   be   declared
1703           __declspec(dllimport), with unwanted results.
1704    
1705         The   functions   pcre_compile(),  pcre_compile2(),  pcre_study(),  and         The   functions   pcre_compile(),  pcre_compile2(),  pcre_study(),  and
1706         pcre_exec() are used for compiling and matching regular expressions  in         pcre_exec() are used for compiling and matching regular expressions  in
1707         a  Perl-compatible  manner. A sample program that demonstrates the sim-         a  Perl-compatible  manner. A sample program that demonstrates the sim-
1708         plest way of using them is provided in the file  called  pcredemo.c  in         plest way of using them is provided in the file  called  pcredemo.c  in
1709         the  source distribution. The pcresample documentation describes how to         the PCRE source distribution. A listing of this program is given in the
1710         run it.         pcredemo documentation, and the pcresample documentation describes  how
1711           to compile and run it.
1712    
1713           Just-in-time  compiler  support is an optional feature of PCRE that can
1714           be built in appropriate hardware environments. It greatly speeds up the
1715           matching  performance  of  many  patterns.  Simple  programs can easily
1716           request that it be used if available, by  setting  an  option  that  is
1717           ignored  when  it is not relevant. More complicated programs might need
1718           to    make    use    of    the    functions     pcre_jit_stack_alloc(),
1719           pcre_jit_stack_free(),  and pcre_assign_jit_stack() in order to control
1720           the JIT code's memory usage.
1721    
1722           From release 8.32 there is also a direct interface for  JIT  execution,
1723           which  gives  improved performance. The JIT-specific functions are dis-
1724           cussed in the pcrejit documentation.
1725    
1726         A second matching function, pcre_dfa_exec(), which is not Perl-compati-         A second matching function, pcre_dfa_exec(), which is not Perl-compati-
1727         ble,  is  also provided. This uses a different algorithm for the match-         ble,  is  also provided. This uses a different algorithm for the match-
1728         ing. This allows it to find all possible matches (at a given  point  in         ing. The alternative algorithm finds all possible matches (at  a  given
1729         the  subject),  not  just  one. However, this algorithm does not return         point  in  the  subject), and scans the subject just once (unless there
1730         captured substrings. A description of the two matching  algorithms  and         are lookbehind assertions). However, this  algorithm  does  not  return
1731         their  advantages  and disadvantages is given in the pcrematching docu-         captured  substrings.  A description of the two matching algorithms and
1732           their advantages and disadvantages is given in the  pcrematching  docu-
1733         mentation.         mentation.
1734    
1735         In addition to the main compiling and  matching  functions,  there  are         In  addition  to  the  main compiling and matching functions, there are
1736         convenience functions for extracting captured substrings from a subject         convenience functions for extracting captured substrings from a subject
1737         string that is matched by pcre_exec(). They are:         string that is matched by pcre_exec(). They are:
1738    
# Line 692  PCRE API OVERVIEW Line 1742  PCRE API OVERVIEW
1742           pcre_get_named_substring()           pcre_get_named_substring()
1743           pcre_get_substring_list()           pcre_get_substring_list()
1744           pcre_get_stringnumber()           pcre_get_stringnumber()
1745             pcre_get_stringtable_entries()
1746    
1747         pcre_free_substring() and pcre_free_substring_list() are also provided,         pcre_free_substring() and pcre_free_substring_list() are also provided,
1748         to free the memory used for extracted strings.         to free the memory used for extracted strings.
1749    
1750         The  function  pcre_maketables()  is  used  to build a set of character         The function pcre_maketables() is used to  build  a  set  of  character
1751         tables  in  the  current  locale   for   passing   to   pcre_compile(),         tables   in   the   current   locale  for  passing  to  pcre_compile(),
1752         pcre_exec(),  or  pcre_dfa_exec(). This is an optional facility that is         pcre_exec(), or pcre_dfa_exec(). This is an optional facility  that  is
1753         provided for specialist use.  Most  commonly,  no  special  tables  are         provided  for  specialist  use.  Most  commonly,  no special tables are
1754         passed,  in  which case internal tables that are generated when PCRE is         passed, in which case internal tables that are generated when  PCRE  is
1755         built are used.         built are used.
1756    
1757         The function pcre_fullinfo() is used to find out  information  about  a         The  function  pcre_fullinfo()  is used to find out information about a
1758         compiled  pattern; pcre_info() is an obsolete version that returns only         compiled pattern. The function pcre_version() returns a  pointer  to  a
1759         some of the available information, but is retained for  backwards  com-         string containing the version of PCRE and its date of release.
        patibility.   The function pcre_version() returns a pointer to a string  
        containing the version of PCRE and its date of release.  
1760    
1761         The function pcre_refcount() maintains a  reference  count  in  a  data         The  function  pcre_refcount()  maintains  a  reference count in a data
1762         block  containing  a compiled pattern. This is provided for the benefit         block containing a compiled pattern. This is provided for  the  benefit
1763         of object-oriented applications.         of object-oriented applications.
1764    
1765         The global variables pcre_malloc and pcre_free  initially  contain  the         The  global  variables  pcre_malloc and pcre_free initially contain the
1766         entry  points  of  the  standard malloc() and free() functions, respec-         entry points of the standard malloc()  and  free()  functions,  respec-
1767         tively. PCRE calls the memory management functions via these variables,         tively. PCRE calls the memory management functions via these variables,
1768         so  a  calling  program  can replace them if it wishes to intercept the         so a calling program can replace them if it  wishes  to  intercept  the
1769         calls. This should be done before calling any PCRE functions.         calls. This should be done before calling any PCRE functions.
1770    
1771         The global variables pcre_stack_malloc  and  pcre_stack_free  are  also         The  global  variables  pcre_stack_malloc  and pcre_stack_free are also
1772         indirections  to  memory  management functions. These special functions         indirections to memory management functions.  These  special  functions
1773         are used only when PCRE is compiled to use  the  heap  for  remembering         are  used  only  when  PCRE is compiled to use the heap for remembering
1774         data, instead of recursive function calls, when running the pcre_exec()         data, instead of recursive function calls, when running the pcre_exec()
1775         function. This is a non-standard way of building PCRE, for use in envi-         function.  See  the  pcrebuild  documentation  for details of how to do
1776         ronments that have limited stacks. Because of the greater use of memory         this. It is a non-standard way of building PCRE, for  use  in  environ-
1777         management, it runs more slowly.  Separate functions  are  provided  so         ments  that  have  limited stacks. Because of the greater use of memory
1778           management, it runs more slowly. Separate  functions  are  provided  so
1779         that  special-purpose  external  code  can  be used for this case. When         that  special-purpose  external  code  can  be used for this case. When
1780         used, these functions are always called in a  stack-like  manner  (last         used, these functions are always called in a  stack-like  manner  (last
1781         obtained,  first freed), and always for memory blocks of the same size.         obtained,  first freed), and always for memory blocks of the same size.
1782           There is a discussion about PCRE's stack usage in the  pcrestack  docu-
1783           mentation.
1784    
1785         The global variable pcre_callout initially contains NULL. It can be set         The global variable pcre_callout initially contains NULL. It can be set
1786         by  the  caller  to  a "callout" function, which PCRE will then call at         by the caller to a "callout" function, which PCRE  will  then  call  at
1787         specified points during a matching operation. Details are given in  the         specified  points during a matching operation. Details are given in the
1788         pcrecallout documentation.         pcrecallout documentation.
1789    
1790    
1791    NEWLINES
1792    
1793           PCRE supports five different conventions for indicating line breaks  in
1794           strings:  a  single  CR (carriage return) character, a single LF (line-
1795           feed) character, the two-character sequence CRLF, any of the three pre-
1796           ceding,  or any Unicode newline sequence. The Unicode newline sequences
1797           are the three just mentioned, plus the single characters  VT  (vertical
1798           tab, U+000B), FF (form feed, U+000C), NEL (next line, U+0085), LS (line
1799           separator, U+2028), and PS (paragraph separator, U+2029).
1800    
1801           Each of the first three conventions is used by at least  one  operating
1802           system  as its standard newline sequence. When PCRE is built, a default
1803           can be specified.  The default default is LF, which is the  Unix  stan-
1804           dard.  When  PCRE  is run, the default can be overridden, either when a
1805           pattern is compiled, or when it is matched.
1806    
1807           At compile time, the newline convention can be specified by the options
1808           argument  of  pcre_compile(), or it can be specified by special text at
1809           the start of the pattern itself; this overrides any other settings. See
1810           the pcrepattern page for details of the special character sequences.
1811    
1812           In the PCRE documentation the word "newline" is used to mean "the char-
1813           acter or pair of characters that indicate a line break". The choice  of
1814           newline  convention  affects  the  handling of the dot, circumflex, and
1815           dollar metacharacters, the handling of #-comments in /x mode, and, when
1816           CRLF  is a recognized line ending sequence, the match position advance-
1817           ment for a non-anchored pattern. There is more detail about this in the
1818           section on pcre_exec() options below.
1819    
1820           The  choice of newline convention does not affect the interpretation of
1821           the \n or \r escape sequences, nor does  it  affect  what  \R  matches,
1822           which is controlled in a similar way, but by separate options.
1823    
1824    
1825  MULTITHREADING  MULTITHREADING
1826    
1827         The  PCRE  functions  can be used in multi-threading applications, with         The  PCRE  functions  can be used in multi-threading applications, with
# Line 743  MULTITHREADING Line 1829  MULTITHREADING
1829         pcre_malloc, pcre_free, pcre_stack_malloc, and pcre_stack_free, and the         pcre_malloc, pcre_free, pcre_stack_malloc, and pcre_stack_free, and the
1830         callout function pointed to by pcre_callout, are shared by all threads.         callout function pointed to by pcre_callout, are shared by all threads.
1831    
1832         The  compiled form of a regular expression is not altered during match-         The compiled form of a regular expression is not altered during  match-
1833         ing, so the same compiled pattern can safely be used by several threads         ing, so the same compiled pattern can safely be used by several threads
1834         at once.         at once.
1835    
1836           If the just-in-time optimization feature is being used, it needs  sepa-
1837           rate  memory stack areas for each thread. See the pcrejit documentation
1838           for more details.
1839    
1840    
1841  SAVING PRECOMPILED PATTERNS FOR LATER USE  SAVING PRECOMPILED PATTERNS FOR LATER USE
1842    
1843         The compiled form of a regular expression can be saved and re-used at a         The compiled form of a regular expression can be saved and re-used at a
1844         later time, possibly by a different program, and even on a  host  other         later  time,  possibly by a different program, and even on a host other
1845         than  the  one  on  which  it  was  compiled.  Details are given in the         than the one on which  it  was  compiled.  Details  are  given  in  the
1846         pcreprecompile documentation.         pcreprecompile  documentation,  which  includes  a  description  of the
1847           pcre_pattern_to_host_byte_order() function. However, compiling a  regu-
1848           lar  expression  with one version of PCRE for use with a different ver-
1849           sion is not guaranteed to work and may cause crashes.
1850    
1851    
1852  CHECKING BUILD-TIME OPTIONS  CHECKING BUILD-TIME OPTIONS
# Line 767  CHECKING BUILD-TIME OPTIONS Line 1860  CHECKING BUILD-TIME OPTIONS
1860    
1861         The  first  argument  for pcre_config() is an integer, specifying which         The  first  argument  for pcre_config() is an integer, specifying which
1862         information is required; the second argument is a pointer to a variable         information is required; the second argument is a pointer to a variable
1863         into  which  the  information  is  placed. The following information is         into  which  the  information  is placed. The returned value is zero on
1864           success, or the negative error code PCRE_ERROR_BADOPTION if  the  value
1865           in  the  first argument is not recognized. The following information is
1866         available:         available:
1867    
1868           PCRE_CONFIG_UTF8           PCRE_CONFIG_UTF8
1869    
1870         The output is an integer that is set to one if UTF-8 support is  avail-         The output is an integer that is set to one if UTF-8 support is  avail-
1871         able; otherwise it is set to zero.         able;  otherwise it is set to zero. This value should normally be given
1872           to the 8-bit version of this function, pcre_config(). If it is given to
1873           the   16-bit  or  32-bit  version  of  this  function,  the  result  is
1874           PCRE_ERROR_BADOPTION.
1875    
1876             PCRE_CONFIG_UTF16
1877    
1878           The output is an integer that is set to one if UTF-16 support is avail-
1879           able;  otherwise it is set to zero. This value should normally be given
1880           to the 16-bit version of this function, pcre16_config(). If it is given
1881           to  the  8-bit  or  32-bit  version  of  this  function,  the result is
1882           PCRE_ERROR_BADOPTION.
1883    
1884             PCRE_CONFIG_UTF32
1885    
1886           The output is an integer that is set to one if UTF-32 support is avail-
1887           able;  otherwise it is set to zero. This value should normally be given
1888           to the 32-bit version of this function, pcre32_config(). If it is given
1889           to  the  8-bit  or  16-bit  version  of  this  function,  the result is
1890           PCRE_ERROR_BADOPTION.
1891    
1892           PCRE_CONFIG_UNICODE_PROPERTIES           PCRE_CONFIG_UNICODE_PROPERTIES
1893    
1894         The  output  is  an  integer  that is set to one if support for Unicode         The output is an integer that is set to  one  if  support  for  Unicode
1895         character properties is available; otherwise it is set to zero.         character properties is available; otherwise it is set to zero.
1896    
1897             PCRE_CONFIG_JIT
1898    
1899           The output is an integer that is set to one if support for just-in-time
1900           compiling is available; otherwise it is set to zero.
1901    
1902             PCRE_CONFIG_JITTARGET
1903    
1904           The output is a pointer to a zero-terminated "const char *" string.  If
1905           JIT support is available, the string contains the name of the architec-
1906           ture for which the JIT compiler is configured, for example  "x86  32bit
1907           (little  endian  +  unaligned)".  If  JIT support is not available, the
1908           result is NULL.
1909    
1910           PCRE_CONFIG_NEWLINE           PCRE_CONFIG_NEWLINE
1911    
1912         The output is an integer that is set to the value of the code  that  is         The output is an integer whose value specifies  the  default  character
1913         used  for the newline character. It is either linefeed (10) or carriage         sequence  that  is recognized as meaning "newline". The values that are
1914         return (13), and should normally be the  standard  character  for  your         supported in ASCII/Unicode environments are: 10 for LF, 13 for CR, 3338
1915         operating system.         for  CRLF,  -2 for ANYCRLF, and -1 for ANY. In EBCDIC environments, CR,
1916           ANYCRLF, and ANY yield the same values. However, the value  for  LF  is
1917           normally  21, though some EBCDIC environments use 37. The corresponding
1918           values for CRLF are 3349 and 3365. The default should  normally  corre-
1919           spond to the standard sequence for your operating system.
1920    
1921             PCRE_CONFIG_BSR
1922    
1923           The output is an integer whose value indicates what character sequences
1924           the \R escape sequence matches by default. A value of 0 means  that  \R
1925           matches  any  Unicode  line ending sequence; a value of 1 means that \R
1926           matches only CR, LF, or CRLF. The default can be overridden when a pat-
1927           tern is compiled or matched.
1928    
1929           PCRE_CONFIG_LINK_SIZE           PCRE_CONFIG_LINK_SIZE
1930    
1931         The  output  is  an  integer that contains the number of bytes used for         The  output  is  an  integer that contains the number of bytes used for
1932         internal linkage in compiled regular expressions. The value is 2, 3, or         internal  linkage  in  compiled  regular  expressions.  For  the  8-bit
1933         4.  Larger  values  allow larger regular expressions to be compiled, at         library, the value can be 2, 3, or 4. For the 16-bit library, the value
1934         the expense of slower matching. The default value of  2  is  sufficient         is either 2 or 4 and is  still  a  number  of  bytes.  For  the  32-bit
1935         for  all  but  the  most massive patterns, since it allows the compiled         library, the value is either 2 or 4 and is still a number of bytes. The
1936         pattern to be up to 64K in size.         default value of 2 is sufficient for all but the most massive patterns,
1937           since  it  allows  the compiled pattern to be up to 64K in size. Larger
1938           values allow larger regular expressions to be compiled, at the  expense
1939           of slower matching.
1940    
1941           PCRE_CONFIG_POSIX_MALLOC_THRESHOLD           PCRE_CONFIG_POSIX_MALLOC_THRESHOLD
1942    
1943         The output is an integer that contains the threshold  above  which  the         The  output  is  an integer that contains the threshold above which the
1944         POSIX  interface  uses malloc() for output vectors. Further details are         POSIX interface uses malloc() for output vectors. Further  details  are
1945         given in the pcreposix documentation.         given in the pcreposix documentation.
1946    
1947           PCRE_CONFIG_MATCH_LIMIT           PCRE_CONFIG_MATCH_LIMIT
1948    
1949         The output is an integer that gives the default limit for the number of         The  output is a long integer that gives the default limit for the num-
1950         internal  matching  function  calls in a pcre_exec() execution. Further         ber of internal matching function calls  in  a  pcre_exec()  execution.
1951         details are given with pcre_exec() below.         Further details are given with pcre_exec() below.
1952    
1953             PCRE_CONFIG_MATCH_LIMIT_RECURSION
1954    
1955           The output is a long integer that gives the default limit for the depth
1956           of  recursion  when  calling  the  internal  matching  function  in   a
1957           pcre_exec()  execution.  Further  details  are  given  with pcre_exec()
1958           below.
1959    
1960           PCRE_CONFIG_STACKRECURSE           PCRE_CONFIG_STACKRECURSE
1961    
# Line 833  COMPILING A PATTERN Line 1982  COMPILING A PATTERN
1982         Either of the functions pcre_compile() or pcre_compile2() can be called         Either of the functions pcre_compile() or pcre_compile2() can be called
1983         to compile a pattern into an internal form. The only difference between         to compile a pattern into an internal form. The only difference between
1984         the two interfaces is that pcre_compile2() has an additional  argument,         the two interfaces is that pcre_compile2() has an additional  argument,
1985         errorcodeptr, via which a numerical error code can be returned.         errorcodeptr,  via  which  a  numerical  error code can be returned. To
1986           avoid too much repetition, we refer just to pcre_compile()  below,  but
1987           the information applies equally to pcre_compile2().
1988    
1989         The pattern is a C string terminated by a binary zero, and is passed in         The pattern is a C string terminated by a binary zero, and is passed in
1990         the pattern argument. A pointer to a single block  of  memory  that  is         the pattern argument. A pointer to a single block  of  memory  that  is
1991         obtained  via  pcre_malloc is returned. This contains the compiled code         obtained  via  pcre_malloc is returned. This contains the compiled code
1992         and related data. The pcre type is defined for the returned block; this         and related data. The pcre type is defined for the returned block; this
1993         is a typedef for a structure whose contents are not externally defined.         is a typedef for a structure whose contents are not externally defined.
1994         It is up to the caller  to  free  the  memory  when  it  is  no  longer         It is up to the caller to free the memory (via pcre_free) when it is no
1995         required.         longer required.
1996    
1997         Although  the compiled code of a PCRE regex is relocatable, that is, it         Although  the compiled code of a PCRE regex is relocatable, that is, it
1998         does not depend on memory location, the complete pcre data block is not         does not depend on memory location, the complete pcre data block is not
1999         fully  relocatable, because it may contain a copy of the tableptr argu-         fully  relocatable, because it may contain a copy of the tableptr argu-
2000         ment, which is an address (see below).         ment, which is an address (see below).
2001    
2002         The options argument contains independent bits that affect the compila-         The options argument contains various bit settings that affect the com-
2003         tion.  It  should  be  zero  if  no options are required. The available         pilation.  It  should be zero if no options are required. The available
2004         options are described below. Some of them, in  particular,  those  that         options are described below. Some of them (in  particular,  those  that
2005         are  compatible  with  Perl,  can also be set and unset from within the         are  compatible with Perl, but some others as well) can also be set and
2006         pattern (see the detailed description  in  the  pcrepattern  documenta-         unset from within the pattern (see  the  detailed  description  in  the
2007         tion).  For  these options, the contents of the options argument speci-         pcrepattern  documentation). For those options that can be different in
2008         fies their initial settings at the start of compilation and  execution.         different parts of the pattern, the contents of  the  options  argument
2009         The  PCRE_ANCHORED option can be set at the time of matching as well as         specifies their settings at the start of compilation and execution. The
2010         at compile time.         PCRE_ANCHORED, PCRE_BSR_xxx, PCRE_NEWLINE_xxx, PCRE_NO_UTF8_CHECK,  and
2011           PCRE_NO_START_OPTIMIZE  options  can  be set at the time of matching as
2012           well as at compile time.
2013    
2014         If errptr is NULL, pcre_compile() returns NULL immediately.  Otherwise,         If errptr is NULL, pcre_compile() returns NULL immediately.  Otherwise,
2015         if  compilation  of  a  pattern fails, pcre_compile() returns NULL, and         if  compilation  of  a  pattern fails, pcre_compile() returns NULL, and
2016         sets the variable pointed to by errptr to point to a textual error mes-         sets the variable pointed to by errptr to point to a textual error mes-
2017         sage.  The  offset from the start of the pattern to the character where         sage. This is a static string that is part of the library. You must not
2018         the error was discovered is  placed  in  the  variable  pointed  to  by         try to free it. Normally, the offset from the start of the  pattern  to
2019         erroffset,  which  must  not  be  NULL. If it is, an immediate error is         the data unit that was being processed when the error was discovered is
2020         given.         placed in the variable pointed to by erroffset, which must not be  NULL
2021           (if  it is, an immediate error is given). However, for an invalid UTF-8
2022         If pcre_compile2() is used instead of pcre_compile(),  and  the  error-         or UTF-16 string, the offset is that of the  first  data  unit  of  the
2023         codeptr  argument is not NULL, a non-zero error code number is returned         failing character.
2024         via this argument in the event of an error. This is in addition to  the  
2025           Some  errors are not detected until the whole pattern has been scanned;
2026           in these cases, the offset passed back is the length  of  the  pattern.
2027           Note  that  the  offset is in data units, not characters, even in a UTF
2028           mode. It may sometimes point into the middle of a UTF-8 or UTF-16 char-
2029           acter.
2030    
2031           If  pcre_compile2()  is  used instead of pcre_compile(), and the error-
2032           codeptr argument is not NULL, a non-zero error code number is  returned
2033           via  this argument in the event of an error. This is in addition to the
2034         textual error message. Error codes and messages are listed below.         textual error message. Error codes and messages are listed below.
2035    
2036         If  the  final  argument, tableptr, is NULL, PCRE uses a default set of         If the final argument, tableptr, is NULL, PCRE uses a  default  set  of
2037         character tables that are  built  when  PCRE  is  compiled,  using  the         character  tables  that  are  built  when  PCRE  is compiled, using the
2038         default  C  locale.  Otherwise, tableptr must be an address that is the         default C locale. Otherwise, tableptr must be an address  that  is  the
2039         result of a call to pcre_maketables(). This value is  stored  with  the         result  of  a  call to pcre_maketables(). This value is stored with the
2040         compiled  pattern,  and used again by pcre_exec(), unless another table         compiled pattern, and used again by pcre_exec(), unless  another  table
2041         pointer is passed to it. For more discussion, see the section on locale         pointer is passed to it. For more discussion, see the section on locale
2042         support below.         support below.
2043    
2044         This  code  fragment  shows a typical straightforward call to pcre_com-         This code fragment shows a typical straightforward  call  to  pcre_com-
2045         pile():         pile():
2046    
2047           pcre *re;           pcre *re;
# Line 892  COMPILING A PATTERN Line 2054  COMPILING A PATTERN
2054             &erroffset,       /* for error offset */             &erroffset,       /* for error offset */
2055             NULL);            /* use default character tables */             NULL);            /* use default character tables */
2056    
2057         The following names for option bits are defined in  the  pcre.h  header         The  following  names  for option bits are defined in the pcre.h header
2058         file:         file:
2059    
2060           PCRE_ANCHORED           PCRE_ANCHORED
2061    
2062         If this bit is set, the pattern is forced to be "anchored", that is, it         If this bit is set, the pattern is forced to be "anchored", that is, it
2063         is constrained to match only at the first matching point in the  string         is  constrained to match only at the first matching point in the string
2064         that  is being searched (the "subject string"). This effect can also be         that is being searched (the "subject string"). This effect can also  be
2065         achieved by appropriate constructs in the pattern itself, which is  the         achieved  by appropriate constructs in the pattern itself, which is the
2066         only way to do it in Perl.         only way to do it in Perl.
2067    
2068           PCRE_AUTO_CALLOUT           PCRE_AUTO_CALLOUT
2069    
2070         If this bit is set, pcre_compile() automatically inserts callout items,         If this bit is set, pcre_compile() automatically inserts callout items,
2071         all with number 255, before each pattern item. For  discussion  of  the         all  with  number  255, before each pattern item. For discussion of the
2072         callout facility, see the pcrecallout documentation.         callout facility, see the pcrecallout documentation.
2073    
2074             PCRE_BSR_ANYCRLF
2075             PCRE_BSR_UNICODE
2076    
2077           These options (which are mutually exclusive) control what the \R escape
2078           sequence  matches.  The choice is either to match only CR, LF, or CRLF,
2079           or to match any Unicode newline sequence. The default is specified when
2080           PCRE is built. It can be overridden from within the pattern, or by set-
2081           ting an option when a compiled pattern is matched.
2082    
2083           PCRE_CASELESS           PCRE_CASELESS
2084    
2085         If  this  bit is set, letters in the pattern match both upper and lower         If this bit is set, letters in the pattern match both upper  and  lower
2086         case letters. It is equivalent to Perl's  /i  option,  and  it  can  be         case  letters.  It  is  equivalent  to  Perl's /i option, and it can be
2087         changed  within a pattern by a (?i) option setting. In UTF-8 mode, PCRE         changed within a pattern by a (?i) option setting. In UTF-8 mode,  PCRE
2088         always understands the concept of case for characters whose values  are         always  understands the concept of case for characters whose values are
2089         less  than 128, so caseless matching is always possible. For characters         less than 128, so caseless matching is always possible. For  characters
2090         with higher values, the concept of case is supported if  PCRE  is  com-         with  higher  values,  the concept of case is supported if PCRE is com-
2091         piled  with Unicode property support, but not otherwise. If you want to         piled with Unicode property support, but not otherwise. If you want  to
2092         use caseless matching for characters 128 and  above,  you  must  ensure         use  caseless  matching  for  characters 128 and above, you must ensure
2093         that  PCRE  is  compiled  with Unicode property support as well as with         that PCRE is compiled with Unicode property support  as  well  as  with
2094         UTF-8 support.         UTF-8 support.
2095    
2096           PCRE_DOLLAR_ENDONLY           PCRE_DOLLAR_ENDONLY
2097    
2098         If this bit is set, a dollar metacharacter in the pattern matches  only         If  this bit is set, a dollar metacharacter in the pattern matches only
2099         at  the  end  of the subject string. Without this option, a dollar also         at the end of the subject string. Without this option,  a  dollar  also
2100         matches immediately before the final character if it is a newline  (but         matches  immediately before a newline at the end of the string (but not
2101         not  before  any  other  newlines).  The  PCRE_DOLLAR_ENDONLY option is         before any other newlines). The PCRE_DOLLAR_ENDONLY option  is  ignored
2102         ignored if PCRE_MULTILINE is set. There is no equivalent to this option         if  PCRE_MULTILINE  is  set.   There is no equivalent to this option in
2103         in Perl, and no way to set it within a pattern.         Perl, and no way to set it within a pattern.
2104    
2105           PCRE_DOTALL           PCRE_DOTALL
2106    
2107         If this bit is set, a dot metacharater in the pattern matches all char-         If this bit is set, a dot metacharacter in the pattern matches a  char-
2108         acters, including newlines. Without it,  newlines  are  excluded.  This         acter of any value, including one that indicates a newline. However, it
2109         option  is equivalent to Perl's /s option, and it can be changed within         only ever matches one character, even if newlines are  coded  as  CRLF.
2110         a pattern by a (?s) option setting.  A  negative  class  such  as  [^a]         Without  this option, a dot does not match when the current position is
2111         always  matches a newline character, independent of the setting of this         at a newline. This option is equivalent to Perl's /s option, and it can
2112         option.         be  changed within a pattern by a (?s) option setting. A negative class
2113           such as [^a] always matches newline characters, independent of the set-
2114           ting of this option.
2115    
2116             PCRE_DUPNAMES
2117    
2118           If  this  bit is set, names used to identify capturing subpatterns need
2119           not be unique. This can be helpful for certain types of pattern when it
2120           is  known  that  only  one instance of the named subpattern can ever be
2121           matched. There are more details of named subpatterns  below;  see  also
2122           the pcrepattern documentation.
2123    
2124           PCRE_EXTENDED           PCRE_EXTENDED
2125    
2126         If this bit is set, whitespace  data  characters  in  the  pattern  are         If  this  bit  is  set,  white space data characters in the pattern are
2127         totally ignored except when escaped or inside a character class. White-         totally ignored except when escaped or inside a character class.  White
2128         space does not include the VT character (code 11). In addition, charac-         space does not include the VT character (code 11). In addition, charac-
2129         ters between an unescaped # outside a character class and the next new-         ters between an unescaped # outside a character class and the next new-
2130         line character, inclusive, are also  ignored.  This  is  equivalent  to         line,  inclusive,  are  also  ignored.  This is equivalent to Perl's /x
2131         Perl's  /x  option,  and  it  can be changed within a pattern by a (?x)         option, and it can be changed within a pattern by a  (?x)  option  set-
2132         option setting.         ting.
2133    
2134           Which  characters  are  interpreted  as  newlines  is controlled by the
2135           options passed to pcre_compile() or by a special sequence at the  start
2136           of  the  pattern, as described in the section entitled "Newline conven-
2137           tions" in the pcrepattern documentation. Note that the end of this type
2138           of  comment  is  a  literal  newline  sequence  in  the pattern; escape
2139           sequences that happen to represent a newline do not count.
2140    
2141         This option makes it possible to include  comments  inside  complicated         This option makes it possible to include  comments  inside  complicated
2142         patterns.   Note,  however,  that this applies only to data characters.         patterns.   Note,  however,  that this applies only to data characters.
2143         Whitespace  characters  may  never  appear  within  special   character         White space  characters  may  never  appear  within  special  character
2144         sequences  in  a  pattern,  for  example  within the sequence (?( which         sequences in a pattern, for example within the sequence (?( that intro-
2145         introduces a conditional subpattern.         duces a conditional subpattern.
2146    
2147           PCRE_EXTRA           PCRE_EXTRA
2148    
# Line 964  COMPILING A PATTERN Line 2152  COMPILING A PATTERN
2152         letter  that  has  no  special  meaning causes an error, thus reserving         letter  that  has  no  special  meaning causes an error, thus reserving
2153         these combinations for future expansion. By  default,  as  in  Perl,  a         these combinations for future expansion. By  default,  as  in  Perl,  a
2154         backslash  followed by a letter with no special meaning is treated as a         backslash  followed by a letter with no special meaning is treated as a
2155         literal. There are at present no  other  features  controlled  by  this         literal. (Perl can, however, be persuaded to give an error for this, by
2156         option. It can also be set by a (?X) option setting within a pattern.         running  it with the -w option.) There are at present no other features
2157           controlled by this option. It can also be set by a (?X) option  setting
2158           within a pattern.
2159    
2160           PCRE_FIRSTLINE           PCRE_FIRSTLINE
2161    
2162         If  this  option  is  set,  an  unanchored pattern is required to match         If  this  option  is  set,  an  unanchored pattern is required to match
2163         before or at the first newline character in the subject string,  though         before or at the first  newline  in  the  subject  string,  though  the
2164         the matched text may continue over the newline.         matched text may continue over the newline.
2165    
2166             PCRE_JAVASCRIPT_COMPAT
2167    
2168           If this option is set, PCRE's behaviour is changed in some ways so that
2169           it is compatible with JavaScript rather than Perl. The changes  are  as
2170           follows:
2171    
2172           (1)  A  lone  closing square bracket in a pattern causes a compile-time
2173           error, because this is illegal in JavaScript (by default it is  treated
2174           as a data character). Thus, the pattern AB]CD becomes illegal when this
2175           option is set.
2176    
2177           (2) At run time, a back reference to an unset subpattern group  matches
2178           an  empty  string (by default this causes the current matching alterna-
2179           tive to fail). A pattern such as (\1)(a) succeeds when this  option  is
2180           set  (assuming  it can find an "a" in the subject), whereas it fails by
2181           default, for Perl compatibility.
2182    
2183           (3) \U matches an upper case "U" character; by default \U causes a com-
2184           pile time error (Perl uses \U to upper case subsequent characters).
2185    
2186           (4) \u matches a lower case "u" character unless it is followed by four
2187           hexadecimal digits, in which case the hexadecimal  number  defines  the
2188           code  point  to match. By default, \u causes a compile time error (Perl
2189           uses it to upper case the following character).
2190    
2191           (5) \x matches a lower case "x" character unless it is followed by  two
2192           hexadecimal  digits,  in  which case the hexadecimal number defines the
2193           code point to match. By default, as in Perl, a  hexadecimal  number  is
2194           always expected after \x, but it may have zero, one, or two digits (so,
2195           for example, \xz matches a binary zero character followed by z).
2196    
2197           PCRE_MULTILINE           PCRE_MULTILINE
2198    
2199         By  default,  PCRE  treats the subject string as consisting of a single         By default, for the purposes of matching "start of line"  and  "end  of
2200         line of characters (even if it actually contains newlines). The  "start         line", PCRE treats the subject string as consisting of a single line of
2201         of  line"  metacharacter  (^)  matches only at the start of the string,         characters, even if it actually contains newlines. The "start of  line"
2202         while the "end of line" metacharacter ($) matches only at  the  end  of         metacharacter (^) matches only at the start of the string, and the "end
2203         the string, or before a terminating newline (unless PCRE_DOLLAR_ENDONLY         of line" metacharacter ($) matches only at the end of  the  string,  or
2204         is set). This is the same as Perl.         before  a terminating newline (except when PCRE_DOLLAR_ENDONLY is set).
2205           Note, however, that unless PCRE_DOTALL  is  set,  the  "any  character"
2206           metacharacter  (.)  does not match at a newline. This behaviour (for ^,
2207           $, and dot) is the same as Perl.
2208    
2209         When PCRE_MULTILINE it is set, the "start of line" and  "end  of  line"         When PCRE_MULTILINE it is set, the "start of line" and  "end  of  line"
2210         constructs  match  immediately following or immediately before any new-         constructs  match  immediately following or immediately before internal
2211         line in the subject string, respectively, as well as at the very  start         newlines in the subject string, respectively, as well as  at  the  very
2212         and  end. This is equivalent to Perl's /m option, and it can be changed         start  and  end.  This is equivalent to Perl's /m option, and it can be
2213         within a pattern by a (?m) option setting. If there are no "\n" charac-         changed within a pattern by a (?m) option setting. If there are no new-
2214         ters  in  a  subject  string, or no occurrences of ^ or $ in a pattern,         lines  in  a  subject string, or no occurrences of ^ or $ in a pattern,
2215         setting PCRE_MULTILINE has no effect.         setting PCRE_MULTILINE has no effect.
2216    
2217             PCRE_NEVER_UTF
2218    
2219           This option locks out interpretation of the pattern as UTF-8 (or UTF-16
2220           or  UTF-32  in the 16-bit and 32-bit libraries). In particular, it pre-
2221           vents the creator of the pattern from switching to  UTF  interpretation
2222           by starting the pattern with (*UTF). This may be useful in applications
2223           that  process  patterns  from  external  sources.  The  combination  of
2224           PCRE_UTF8 and PCRE_NEVER_UTF also causes an error.
2225    
2226             PCRE_NEWLINE_CR
2227             PCRE_NEWLINE_LF
2228             PCRE_NEWLINE_CRLF
2229             PCRE_NEWLINE_ANYCRLF
2230             PCRE_NEWLINE_ANY
2231    
2232           These  options  override the default newline definition that was chosen
2233           when PCRE was built. Setting the first or the second specifies  that  a
2234           newline  is  indicated  by a single character (CR or LF, respectively).
2235           Setting PCRE_NEWLINE_CRLF specifies that a newline is indicated by  the
2236           two-character  CRLF  sequence.  Setting  PCRE_NEWLINE_ANYCRLF specifies
2237           that any of the three preceding sequences should be recognized. Setting
2238           PCRE_NEWLINE_ANY  specifies that any Unicode newline sequence should be
2239           recognized.
2240    
2241           In an ASCII/Unicode environment, the Unicode newline sequences are  the
2242           three  just  mentioned,  plus  the  single characters VT (vertical tab,
2243           U+000B), FF (form feed, U+000C), NEL (next line, U+0085), LS (line sep-
2244           arator,  U+2028),  and  PS (paragraph separator, U+2029). For the 8-bit
2245           library, the last two are recognized only in UTF-8 mode.
2246    
2247           When PCRE is compiled to run in an EBCDIC (mainframe) environment,  the
2248           code for CR is 0x0d, the same as ASCII. However, the character code for
2249           LF is normally 0x15, though in some EBCDIC environments 0x25  is  used.
2250           Whichever  of  these  is  not LF is made to correspond to Unicode's NEL
2251           character. EBCDIC codes are all less than 256. For  more  details,  see
2252           the pcrebuild documentation.
2253    
2254           The  newline  setting  in  the  options  word  uses three bits that are
2255           treated as a number, giving eight possibilities. Currently only six are
2256           used  (default  plus the five values above). This means that if you set
2257           more than one newline option, the combination may or may not be  sensi-
2258           ble. For example, PCRE_NEWLINE_CR with PCRE_NEWLINE_LF is equivalent to
2259           PCRE_NEWLINE_CRLF, but other combinations may yield unused numbers  and
2260           cause an error.
2261    
2262           The  only  time  that a line break in a pattern is specially recognized
2263           when compiling is when PCRE_EXTENDED is set. CR and LF are white  space
2264           characters,  and so are ignored in this mode. Also, an unescaped # out-
2265           side a character class indicates a comment that lasts until  after  the
2266           next  line break sequence. In other circumstances, line break sequences
2267           in patterns are treated as literal data.
2268    
2269           The newline option that is set at compile time becomes the default that
2270           is used for pcre_exec() and pcre_dfa_exec(), but it can be overridden.
2271    
2272           PCRE_NO_AUTO_CAPTURE           PCRE_NO_AUTO_CAPTURE
2273    
2274         If this option is set, it disables the use of numbered capturing paren-         If this option is set, it disables the use of numbered capturing paren-
2275         theses  in the pattern. Any opening parenthesis that is not followed by         theses in the pattern. Any opening parenthesis that is not followed  by
2276         ? behaves as if it were followed by ?: but named parentheses can  still         ?  behaves as if it were followed by ?: but named parentheses can still
2277         be  used  for  capturing  (and  they acquire numbers in the usual way).         be used for capturing (and they acquire  numbers  in  the  usual  way).
2278         There is no equivalent of this option in Perl.         There is no equivalent of this option in Perl.
2279    
2280             PCRE_NO_START_OPTIMIZE
2281    
2282           This  is an option that acts at matching time; that is, it is really an
2283           option for pcre_exec() or pcre_dfa_exec(). If  it  is  set  at  compile
2284           time,  it is remembered with the compiled pattern and assumed at match-
2285           ing time. This is necessary if you want to use JIT  execution,  because
2286           the  JIT  compiler needs to know whether or not this option is set. For
2287           details see the discussion of PCRE_NO_START_OPTIMIZE below.
2288    
2289             PCRE_UCP
2290    
2291           This option changes the way PCRE processes \B, \b, \D, \d, \S, \s,  \W,
2292           \w,  and  some  of  the POSIX character classes. By default, only ASCII
2293           characters are recognized, but if PCRE_UCP is set,  Unicode  properties
2294           are  used instead to classify characters. More details are given in the
2295           section on generic character types in the pcrepattern page. If you  set
2296           PCRE_UCP,  matching  one of the items it affects takes much longer. The
2297           option is available only if PCRE has been compiled with  Unicode  prop-
2298           erty support.
2299    
2300           PCRE_UNGREEDY           PCRE_UNGREEDY
2301    
2302         This option inverts the "greediness" of the quantifiers  so  that  they         This  option  inverts  the "greediness" of the quantifiers so that they
2303         are  not greedy by default, but become greedy if followed by "?". It is         are not greedy by default, but become greedy if followed by "?". It  is
2304         not compatible with Perl. It can also be set by a (?U)  option  setting         not  compatible  with Perl. It can also be set by a (?U) option setting
2305         within the pattern.         within the pattern.
2306    
2307           PCRE_UTF8           PCRE_UTF8
2308    
2309         This  option  causes PCRE to regard both the pattern and the subject as         This option causes PCRE to regard both the pattern and the  subject  as
2310         strings of UTF-8 characters instead of single-byte  character  strings.         strings of UTF-8 characters instead of single-byte strings. However, it
2311         However,  it is available only when PCRE is built to include UTF-8 sup-         is available only when PCRE is built to include UTF  support.  If  not,
2312         port. If not, the use of this option provokes an error. Details of  how         the  use  of  this option provokes an error. Details of how this option
2313         this  option  changes the behaviour of PCRE are given in the section on         changes the behaviour of PCRE are given in the pcreunicode page.
        UTF-8 support in the main pcre page.  
2314    
2315           PCRE_NO_UTF8_CHECK           PCRE_NO_UTF8_CHECK
2316    
2317         When PCRE_UTF8 is set, the validity of the pattern as a UTF-8 string is         When PCRE_UTF8 is set, the validity of the pattern as a UTF-8 string is
2318         automatically  checked. If an invalid UTF-8 sequence of bytes is found,         automatically  checked.  There  is  a  discussion about the validity of
2319         pcre_compile() returns an error. If you already know that your  pattern         UTF-8 strings in the pcreunicode page. If an invalid UTF-8 sequence  is
2320         is  valid, and you want to skip this check for performance reasons, you         found,  pcre_compile()  returns an error. If you already know that your
2321         can set the PCRE_NO_UTF8_CHECK option. When it is set,  the  effect  of         pattern is valid, and you want to skip this check for performance  rea-
2322         passing an invalid UTF-8 string as a pattern is undefined. It may cause         sons,  you  can set the PCRE_NO_UTF8_CHECK option.  When it is set, the
2323         your program to crash.  Note that this option can  also  be  passed  to         effect of passing an invalid UTF-8 string as a pattern is undefined. It
2324         pcre_exec()  and pcre_dfa_exec(), to suppress the UTF-8 validity check-         may  cause  your  program  to  crash. Note that this option can also be
2325         ing of subject strings.         passed to pcre_exec() and pcre_dfa_exec(),  to  suppress  the  validity
2326           checking  of  subject strings only. If the same string is being matched
2327           many times, the option can be safely set for the second and  subsequent
2328           matchings to improve performance.
2329    
2330    
2331  COMPILATION ERROR CODES  COMPILATION ERROR CODES
2332    
2333         The following table lists the error  codes  than  may  be  returned  by         The  following  table  lists  the  error  codes than may be returned by
2334         pcre_compile2(),  along with the error messages that may be returned by         pcre_compile2(), along with the error messages that may be returned  by
2335         both compiling functions.         both  compiling  functions.  Note  that error messages are always 8-bit
2336           ASCII strings, even in 16-bit or 32-bit mode. As  PCRE  has  developed,
2337           some  error codes have fallen out of use. To avoid confusion, they have
2338           not been re-used.
2339    
2340            0  no error            0  no error
2341            1  \ at end of pattern            1  \ at end of pattern
# Line 1043  COMPILATION ERROR CODES Line 2347  COMPILATION ERROR CODES
2347            7  invalid escape sequence in character class            7  invalid escape sequence in character class
2348            8  range out of order in character class            8  range out of order in character class
2349            9  nothing to repeat            9  nothing to repeat
2350           10  operand of unlimited repeat could match the empty string           10  [this code is not in use]
2351           11  internal error: unexpected repeat           11  internal error: unexpected repeat
2352           12  unrecognized character after (?           12  unrecognized character after (? or (?-
2353           13  POSIX named classes are supported only within a class           13  POSIX named classes are supported only within a class
2354           14  missing )           14  missing )
2355           15  reference to non-existent subpattern           15  reference to non-existent subpattern
2356           16  erroffset passed as NULL           16  erroffset passed as NULL
2357           17  unknown option bit(s) set           17  unknown option bit(s) set
2358           18  missing ) after comment           18  missing ) after comment
2359           19  parentheses nested too deeply           19  [this code is not in use]
2360           20  regular expression too large           20  regular expression is too large
2361           21  failed to get memory           21  failed to get memory
2362           22  unmatched parentheses           22  unmatched parentheses
2363           23  internal error: code overflow           23  internal error: code overflow
2364           24  unrecognized character after (?<           24  unrecognized character after (?<
2365           25  lookbehind assertion is not fixed length           25  lookbehind assertion is not fixed length
2366           26  malformed number after (?(           26  malformed number or name after (?(
2367           27  conditional group contains more than two branches           27  conditional group contains more than two branches
2368           28  assertion expected after (?(           28  assertion expected after (?(
2369           29  (?R or (?digits must be followed by )           29  (?R or (?[+-]digits must be followed by )
2370           30  unknown POSIX class name           30  unknown POSIX class name
2371           31  POSIX collating elements are not supported           31  POSIX collating elements are not supported
2372           32  this version of PCRE is not compiled with PCRE_UTF8 support           32  this version of PCRE is compiled without UTF support
2373           33  spare error           33  [this code is not in use]
2374           34  character value in \x{...} sequence is too large           34  character value in \x{...} sequence is too large
2375           35  invalid condition (?(0)           35  invalid condition (?(0)
2376           36  \C not allowed in lookbehind assertion           36  \C not allowed in lookbehind assertion
2377           37  PCRE does not support \L, \l, \N, \U, or \u           37  PCRE does not support \L, \l, \N{name}, \U, or \u
2378           38  number after (?C is > 255           38  number after (?C is > 255
2379           39  closing ) for (?C expected           39  closing ) for (?C expected
2380           40  recursive call could loop indefinitely           40  recursive call could loop indefinitely
2381           41  unrecognized character after (?P           41  unrecognized character after (?P
2382           42  syntax error after (?P           42  syntax error in subpattern name (missing terminator)
2383           43  two named groups have the same name           43  two named subpatterns have the same name
2384           44  invalid UTF-8 string           44  invalid UTF-8 string (specifically UTF-8)
2385           45  support for \P, \p, and \X has not been compiled           45  support for \P, \p, and \X has not been compiled
2386           46  malformed \P or \p sequence           46  malformed \P or \p sequence
2387           47  unknown property name after \P or \p           47  unknown property name after \P or \p
2388             48  subpattern name is too long (maximum 32 characters)
2389             49  too many named subpatterns (maximum 10000)
2390             50  [this code is not in use]
2391             51  octal value is greater than \377 in 8-bit non-UTF-8 mode
2392             52  internal error: overran compiling workspace
2393             53  internal error: previously-checked referenced subpattern
2394                   not found
2395             54  DEFINE group contains more than one branch
2396             55  repeating a DEFINE group is not allowed
2397             56  inconsistent NEWLINE options
2398             57  \g is not followed by a braced, angle-bracketed, or quoted
2399                   name/number or by a plain number
2400             58  a numbered reference must not be zero
2401             59  an argument is not allowed for (*ACCEPT), (*FAIL), or (*COMMIT)
2402             60  (*VERB) not recognized or malformed
2403             61  number is too big
2404             62  subpattern name expected
2405             63  digit expected after (?+
2406             64  ] is an invalid data character in JavaScript compatibility mode
2407             65  different names for subpatterns of the same number are
2408                   not allowed
2409             66  (*MARK) must have an argument
2410             67  this version of PCRE is not compiled with Unicode property
2411                   support
2412             68  \c must be followed by an ASCII character
2413             69  \k is not followed by a braced, angle-bracketed, or quoted name
2414             70  internal error: unknown opcode in find_fixedlength()
2415             71  \N is not supported in a class
2416             72  too many forward references
2417             73  disallowed Unicode code point (>= 0xd800 && <= 0xdfff)
2418             74  invalid UTF-16 string (specifically UTF-16)
2419             75  name is too long in (*MARK), (*PRUNE), (*SKIP), or (*THEN)
2420             76  character value in \u.... sequence is too large
2421             77  invalid UTF-32 string (specifically UTF-32)
2422    
2423           The numbers 32 and 10000 in errors 48 and 49  are  defaults;  different
2424           values may be used if the limits were changed when PCRE was built.
2425    
2426    
2427  STUDYING A PATTERN  STUDYING A PATTERN
# Line 1088  STUDYING A PATTERN Line 2429  STUDYING A PATTERN
2429         pcre_extra *pcre_study(const pcre *code, int options         pcre_extra *pcre_study(const pcre *code, int options
2430              const char **errptr);              const char **errptr);
2431    
2432         If a compiled pattern is going to be used several times,  it  is  worth         If  a  compiled  pattern is going to be used several times, it is worth
2433         spending more time analyzing it in order to speed up the time taken for         spending more time analyzing it in order to speed up the time taken for
2434         matching. The function pcre_study() takes a pointer to a compiled  pat-         matching.  The function pcre_study() takes a pointer to a compiled pat-
2435         tern as its first argument. If studying the pattern produces additional         tern as its first argument. If studying the pattern produces additional
2436         information that will help speed up matching,  pcre_study()  returns  a         information  that  will  help speed up matching, pcre_study() returns a
2437         pointer  to a pcre_extra block, in which the study_data field points to         pointer to a pcre_extra block, in which the study_data field points  to
2438         the results of the study.         the results of the study.
2439    
2440         The  returned  value  from  pcre_study()  can  be  passed  directly  to         The  returned  value  from  pcre_study()  can  be  passed  directly  to
2441         pcre_exec().  However,  a  pcre_extra  block also contains other fields         pcre_exec() or pcre_dfa_exec(). However, a pcre_extra block  also  con-
2442         that can be set by the caller before the block  is  passed;  these  are         tains  other  fields  that can be set by the caller before the block is
2443         described below in the section on matching a pattern.         passed; these are described below in the section on matching a pattern.
2444    
2445         If  studying  the  pattern  does not produce any additional information         If studying the  pattern  does  not  produce  any  useful  information,
2446         pcre_study() returns NULL. In that circumstance, if the calling program         pcre_study()  returns  NULL  by  default.  In that circumstance, if the
2447         wants  to  pass  any of the other fields to pcre_exec(), it must set up         calling program wants to pass any of the other fields to pcre_exec() or
2448         its own pcre_extra block.         pcre_dfa_exec(),  it  must set up its own pcre_extra block. However, if
2449           pcre_study() is called  with  the  PCRE_STUDY_EXTRA_NEEDED  option,  it
2450         The second argument of pcre_study() contains option bits.  At  present,         returns a pcre_extra block even if studying did not find any additional
2451         no options are defined, and this argument should always be zero.         information. It may still return NULL, however, if an error  occurs  in
2452           pcre_study().
2453         The  third argument for pcre_study() is a pointer for an error message.  
2454         If studying succeeds (even if no data is  returned),  the  variable  it         The  second  argument  of  pcre_study() contains option bits. There are
2455         points  to  is set to NULL. Otherwise it points to a textual error mes-         three further options in addition to PCRE_STUDY_EXTRA_NEEDED:
2456         sage. You should therefore test the error pointer for NULL after  call-  
2457         ing pcre_study(), to be sure that it has run successfully.           PCRE_STUDY_JIT_COMPILE
2458             PCRE_STUDY_JIT_PARTIAL_HARD_COMPILE
2459             PCRE_STUDY_JIT_PARTIAL_SOFT_COMPILE
2460    
2461           If any of these are set, and the just-in-time  compiler  is  available,
2462           the  pattern  is  further compiled into machine code that executes much
2463           faster than the pcre_exec()  interpretive  matching  function.  If  the
2464           just-in-time  compiler is not available, these options are ignored. All
2465           undefined bits in the options argument must be zero.
2466    
2467           JIT compilation is a heavyweight optimization. It can  take  some  time
2468           for  patterns  to  be analyzed, and for one-off matches and simple pat-
2469           terns the benefit of faster execution might be offset by a much  slower
2470           study time.  Not all patterns can be optimized by the JIT compiler. For
2471           those that cannot be handled, matching automatically falls back to  the
2472           pcre_exec()  interpreter.  For more details, see the pcrejit documenta-
2473           tion.
2474    
2475         This is a typical call to pcre_study():         The third argument for pcre_study() is a pointer for an error  message.
2476           If  studying  succeeds  (even  if no data is returned), the variable it
2477           points to is set to NULL. Otherwise it is set to  point  to  a  textual
2478           error message. This is a static string that is part of the library. You
2479           must not try to free it. You should test the  error  pointer  for  NULL
2480           after calling pcre_study(), to be sure that it has run successfully.
2481    
2482           When  you are finished with a pattern, you can free the memory used for
2483           the study data by calling pcre_free_study(). This function was added to
2484           the  API  for  release  8.20. For earlier versions, the memory could be
2485           freed with pcre_free(), just like the pattern itself. This  will  still
2486           work  in  cases where JIT optimization is not used, but it is advisable
2487           to change to the new function when convenient.
2488    
2489           pcre_extra *pe;         This is a typical way in which pcre_study() is used (except that  in  a
2490           pe = pcre_study(         real application there should be tests for errors):
2491    
2492             int rc;
2493             pcre *re;
2494             pcre_extra *sd;
2495             re = pcre_compile("pattern", 0, &error, &erroroffset, NULL);
2496             sd = pcre_study(
2497             re,             /* result of pcre_compile() */             re,             /* result of pcre_compile() */
2498             0,              /* no options exist */             0,              /* no options */
2499             &error);        /* set to NULL or points to a message */             &error);        /* set to NULL or points to a message */
2500             rc = pcre_exec(   /* see below for details of pcre_exec() options */
2501               re, sd, "subject", 7, 0, 0, ovector, 30);
2502             ...
2503             pcre_free_study(sd);
2504             pcre_free(re);
2505    
2506           Studying a pattern does two things: first, a lower bound for the length
2507           of subject string that is needed to match the pattern is computed. This
2508           does not mean that there are any strings of that length that match, but
2509           it does guarantee that no shorter strings match. The value is  used  to
2510           avoid wasting time by trying to match strings that are shorter than the
2511           lower bound. You can find out the value in a calling  program  via  the
2512           pcre_fullinfo() function.
2513    
2514           Studying a pattern is also useful for non-anchored patterns that do not
2515           have a single fixed starting character. A bitmap of  possible  starting
2516           bytes  is  created. This speeds up finding a position in the subject at
2517           which to start matching. (In 16-bit mode, the bitmap is used for 16-bit
2518           values  less  than  256.  In 32-bit mode, the bitmap is used for 32-bit
2519           values less than 256.)
2520    
2521           These two optimizations apply to both pcre_exec() and  pcre_dfa_exec(),
2522           and  the  information  is also used by the JIT compiler.  The optimiza-
2523           tions can be disabled by  setting  the  PCRE_NO_START_OPTIMIZE  option.
2524           You  might want to do this if your pattern contains callouts or (*MARK)
2525           and you want to make use of these facilities in  cases  where  matching
2526           fails.
2527    
2528           PCRE_NO_START_OPTIMIZE  can be specified at either compile time or exe-
2529           cution  time.  However,  if   PCRE_NO_START_OPTIMIZE   is   passed   to
2530           pcre_exec(), (that is, after any JIT compilation has happened) JIT exe-
2531           cution is disabled. For JIT execution to work with  PCRE_NO_START_OPTI-
2532           MIZE, the option must be set at compile time.
2533    
2534         At present, studying a pattern is useful only for non-anchored patterns         There is a longer discussion of PCRE_NO_START_OPTIMIZE below.
        that do not have a single fixed starting character. A bitmap of  possi-  
        ble starting bytes is created.  
2535    
2536    
2537  LOCALE SUPPORT  LOCALE SUPPORT
2538    
2539         PCRE  handles  caseless matching, and determines whether characters are         PCRE  handles  caseless matching, and determines whether characters are
2540         letters digits, or whatever, by reference to a set of  tables,  indexed         letters, digits, or whatever, by reference to a set of tables,  indexed
2541         by  character  value.  When running in UTF-8 mode, this applies only to         by  character  value.  When running in UTF-8 mode, this applies only to
2542         characters with codes less than 128. Higher-valued  codes  never  match         characters with codes less than 128. By  default,  higher-valued  codes
2543         escapes  such  as  \w or \d, but can be tested with \p if PCRE is built         never match escapes such as \w or \d, but they can be tested with \p if
2544         with Unicode character property support.         PCRE is built with Unicode character property  support.  Alternatively,
2545           the  PCRE_UCP  option  can  be  set at compile time; this causes \w and
2546         An internal set of tables is created in the default C locale when  PCRE         friends to use Unicode property support instead of built-in tables. The
2547         is  built.  This  is  used when the final argument of pcre_compile() is         use of locales with Unicode is discouraged. If you are handling charac-
2548         NULL, and is sufficient for many applications. An  alternative  set  of         ters with codes greater than 128, you should either use UTF-8 and  Uni-
2549         tables  can,  however, be supplied. These may be created in a different         code, or use locales, but not try to mix the two.
2550         locale from the default. As more and more applications change to  using  
2551         Unicode, the need for this locale support is expected to die away.         PCRE  contains  an  internal set of tables that are used when the final
2552           argument of pcre_compile() is  NULL.  These  are  sufficient  for  many
2553           applications.  Normally, the internal tables recognize only ASCII char-
2554           acters. However, when PCRE is built, it is possible to cause the inter-
2555           nal tables to be rebuilt in the default "C" locale of the local system,
2556           which may cause them to be different.
2557    
2558           The internal tables can always be overridden by tables supplied by  the
2559           application that calls PCRE. These may be created in a different locale
2560           from the default. As more and more applications change  to  using  Uni-
2561           code, the need for this locale support is expected to die away.
2562    
2563         External  tables  are  built by calling the pcre_maketables() function,         External  tables  are  built by calling the pcre_maketables() function,
2564         which has no arguments, in the relevant locale. The result can then  be         which has no arguments, in the relevant locale. The result can then  be
# Line 1155  LOCALE SUPPORT Line 2571  LOCALE SUPPORT
2571           tables = pcre_maketables();           tables = pcre_maketables();
2572           re = pcre_compile(..., tables);           re = pcre_compile(..., tables);
2573    
2574         When pcre_maketables() runs, the tables are built  in  memory  that  is         The locale name "fr_FR" is used on Linux and other  Unix-like  systems;
2575         obtained  via  pcre_malloc. It is the caller's responsibility to ensure         if you are using Windows, the name for the French locale is "french".
2576         that the memory containing the tables remains available for as long  as  
2577           When  pcre_maketables()  runs,  the  tables are built in memory that is
2578           obtained via pcre_malloc. It is the caller's responsibility  to  ensure
2579           that  the memory containing the tables remains available for as long as
2580         it is needed.         it is needed.
2581    
2582         The pointer that is passed to pcre_compile() is saved with the compiled         The pointer that is passed to pcre_compile() is saved with the compiled
2583         pattern, and the same tables are used via this pointer by  pcre_study()         pattern,  and the same tables are used via this pointer by pcre_study()
2584         and normally also by pcre_exec(). Thus, by default, for any single pat-         and normally also by pcre_exec(). Thus, by default, for any single pat-
2585         tern, compilation, studying and matching all happen in the same locale,         tern, compilation, studying and matching all happen in the same locale,
2586         but different patterns can be compiled in different locales.         but different patterns can be compiled in different locales.
2587    
2588         It  is  possible to pass a table pointer or NULL (indicating the use of         It is possible to pass a table pointer or NULL (indicating the  use  of
2589         the internal tables) to pcre_exec(). Although  not  intended  for  this         the  internal  tables)  to  pcre_exec(). Although not intended for this
2590         purpose,  this facility could be used to match a pattern in a different         purpose, this facility could be used to match a pattern in a  different
2591         locale from the one in which it was compiled. Passing table pointers at         locale from the one in which it was compiled. Passing table pointers at
2592         run time is discussed below in the section on matching a pattern.         run time is discussed below in the section on matching a pattern.
2593    
# Line 1178  INFORMATION ABOUT A PATTERN Line 2597  INFORMATION ABOUT A PATTERN
2597         int pcre_fullinfo(const pcre *code, const pcre_extra *extra,         int pcre_fullinfo(const pcre *code, const pcre_extra *extra,
2598              int what, void *where);              int what, void *where);
2599    
2600         The  pcre_fullinfo() function returns information about a compiled pat-         The pcre_fullinfo() function returns information about a compiled  pat-
2601         tern. It replaces the obsolete pcre_info() function, which is neverthe-         tern.  It replaces the pcre_info() function, which was removed from the
2602         less retained for backwards compability (and is documented below).         library at version 8.30, after more than 10 years of obsolescence.
2603    
2604         The  first  argument  for  pcre_fullinfo() is a pointer to the compiled         The first argument for pcre_fullinfo() is a  pointer  to  the  compiled
2605         pattern. The second argument is the result of pcre_study(), or NULL  if         pattern.  The second argument is the result of pcre_study(), or NULL if
2606         the  pattern  was not studied. The third argument specifies which piece         the pattern was not studied. The third argument specifies  which  piece
2607         of information is required, and the fourth argument is a pointer  to  a         of  information  is required, and the fourth argument is a pointer to a
2608         variable  to  receive  the  data. The yield of the function is zero for         variable to receive the data. The yield of the  function  is  zero  for
2609         success, or one of the following negative numbers:         success, or one of the following negative numbers:
2610    
2611           PCRE_ERROR_NULL       the argument code was NULL           PCRE_ERROR_NULL           the argument code was NULL
2612                                 the argument where was NULL                                     the argument where was NULL
2613           PCRE_ERROR_BADMAGIC   the "magic number" was not found           PCRE_ERROR_BADMAGIC       the "magic number" was not found
2614           PCRE_ERROR_BADOPTION  the value of what was invalid           PCRE_ERROR_BADENDIANNESS  the pattern was compiled with different
2615                                       endianness
2616         The "magic number" is placed at the start of each compiled  pattern  as           PCRE_ERROR_BADOPTION      the value of what was invalid
2617         an  simple check against passing an arbitrary memory pointer. Here is a           PCRE_ERROR_UNSET          the requested field is not set
2618         typical call of pcre_fullinfo(), to obtain the length of  the  compiled  
2619         pattern:         The  "magic  number" is placed at the start of each compiled pattern as
2620           an simple check against passing an arbitrary memory pointer. The  endi-
2621           anness error can occur if a compiled pattern is saved and reloaded on a
2622           different host. Here is a typical call of  pcre_fullinfo(),  to  obtain
2623           the length of the compiled pattern:
2624    
2625           int rc;           int rc;
2626           unsigned long int length;           size_t length;
2627           rc = pcre_fullinfo(           rc = pcre_fullinfo(
2628             re,               /* result of pcre_compile() */             re,               /* result of pcre_compile() */
2629             pe,               /* result of pcre_study(), or NULL */             sd,               /* result of pcre_study(), or NULL */
2630             PCRE_INFO_SIZE,   /* what is required */             PCRE_INFO_SIZE,   /* what is required */
2631             &length);         /* where to put the data */             &length);         /* where to put the data */
2632    
# Line 1231  INFORMATION ABOUT A PATTERN Line 2654  INFORMATION ABOUT A PATTERN
2654    
2655           PCRE_INFO_FIRSTBYTE           PCRE_INFO_FIRSTBYTE
2656    
2657         Return  information  about  the first byte of any matched string, for a         Return information about the first data unit of any matched string, for
2658         non-anchored   pattern.   (This    option    used    to    be    called         a non-anchored pattern. (The name of this option refers  to  the  8-bit
2659         PCRE_INFO_FIRSTCHAR;  the  old  name  is still recognized for backwards         library,  where data units are bytes.) The fourth argument should point
2660         compatibility.)         to an int variable.
2661    
2662         If there is a fixed first byte, for example, from  a  pattern  such  as         If there is a fixed first value, for example, the  letter  "c"  from  a
2663         (cat|cow|coyote),  it  is  returned in the integer pointed to by where.         pattern  such  as (cat|cow|coyote), its value is returned. In the 8-bit
2664         Otherwise, if either         library, the value is always less than 256. In the 16-bit  library  the
2665           value can be up to 0xffff. In the 32-bit library the value can be up to
2666           0x10ffff.
2667    
2668           If there is no fixed first value, and if either
2669    
2670         (a) the pattern was compiled with the PCRE_MULTILINE option, and  every         (a) the pattern was compiled with the PCRE_MULTILINE option, and  every
2671         branch starts with "^", or         branch starts with "^", or
# Line 1250  INFORMATION ABOUT A PATTERN Line 2677  INFORMATION ABOUT A PATTERN
2677         of  a  subject string or after any newline within the string. Otherwise         of  a  subject string or after any newline within the string. Otherwise
2678         -2 is returned. For anchored patterns, -2 is returned.         -2 is returned. For anchored patterns, -2 is returned.
2679    
2680           Since for the 32-bit library using the non-UTF-32 mode,  this  function
2681           is  unable to return the full 32-bit range of the character, this value
2682           is   deprecated;   instead   the   PCRE_INFO_FIRSTCHARACTERFLAGS    and
2683           PCRE_INFO_FIRSTCHARACTER values should be used.
2684    
2685           PCRE_INFO_FIRSTTABLE           PCRE_INFO_FIRSTTABLE
2686    
2687         If the pattern was studied, and this resulted in the construction of  a         If  the pattern was studied, and this resulted in the construction of a
2688         256-bit table indicating a fixed set of bytes for the first byte in any         256-bit table indicating a fixed set of values for the first data  unit
2689         matching string, a pointer to the table is returned. Otherwise NULL  is         in  any  matching string, a pointer to the table is returned. Otherwise
2690         returned.  The fourth argument should point to an unsigned char * vari-         NULL is returned. The fourth argument should point to an unsigned  char
2691         able.         * variable.
2692    
2693             PCRE_INFO_HASCRORLF
2694    
2695           Return  1  if  the  pattern  contains any explicit matches for CR or LF
2696           characters, otherwise 0. The fourth argument should  point  to  an  int
2697           variable.  An explicit match is either a literal CR or LF character, or
2698           \r or \n.
2699    
2700             PCRE_INFO_JCHANGED
2701    
2702           Return 1 if the (?J) or (?-J) option setting is used  in  the  pattern,
2703           otherwise  0. The fourth argument should point to an int variable. (?J)
2704           and (?-J) set and unset the local PCRE_DUPNAMES option, respectively.
2705    
2706             PCRE_INFO_JIT
2707    
2708           Return 1 if the pattern was studied with one of the  JIT  options,  and
2709           just-in-time compiling was successful. The fourth argument should point
2710           to an int variable. A return value of 0 means that JIT support  is  not
2711           available  in this version of PCRE, or that the pattern was not studied
2712           with a JIT option, or that the JIT compiler could not handle this  par-
2713           ticular  pattern. See the pcrejit documentation for details of what can
2714           and cannot be handled.
2715    
2716             PCRE_INFO_JITSIZE
2717    
2718           If the pattern was successfully studied with a JIT option,  return  the
2719           size  of the JIT compiled code, otherwise return zero. The fourth argu-
2720           ment should point to a size_t variable.
2721    
2722           PCRE_INFO_LASTLITERAL           PCRE_INFO_LASTLITERAL
2723    
2724         Return the value of the rightmost literal byte that must exist  in  any         Return the value of the rightmost literal data unit that must exist  in
2725         matched  string,  other  than  at  its  start,  if such a byte has been         any  matched  string, other than at its start, if such a value has been
2726         recorded. The fourth argument should point to an int variable. If there         recorded. The fourth argument should point to an int variable. If there
2727         is  no such byte, -1 is returned. For anchored patterns, a last literal         is no such value, -1 is returned. For anchored patterns, a last literal
2728         byte is recorded only if it follows something of variable  length.  For         value is recorded only if it follows something of variable length.  For
2729         example, for the pattern /^a\d+z\d+/ the returned value is "z", but for         example, for the pattern /^a\d+z\d+/ the returned value is "z", but for
2730         /^a\dz\d/ the returned value is -1.         /^a\dz\d/ the returned value is -1.
2731    
2732           Since for the 32-bit library using the non-UTF-32 mode,  this  function
2733           is  unable to return the full 32-bit range of the character, this value
2734           is   deprecated;   instead    the    PCRE_INFO_REQUIREDCHARFLAGS    and
2735           PCRE_INFO_REQUIREDCHAR values should be used.
2736    
2737             PCRE_INFO_MATCHLIMIT
2738    
2739           If  the  pattern  set  a  match  limit by including an item of the form
2740           (*LIMIT_MATCH=nnnn) at the start, the value  is  returned.  The  fourth
2741           argument  should  point to an unsigned 32-bit integer. If no such value
2742           has  been  set,  the  call  to  pcre_fullinfo()   returns   the   error
2743           PCRE_ERROR_UNSET.
2744    
2745             PCRE_INFO_MAXLOOKBEHIND
2746    
2747           Return  the  number  of  characters  (NB not data units) in the longest
2748           lookbehind assertion in the pattern. This information  is  useful  when
2749           doing  multi-segment  matching  using  the partial matching facilities.
2750           Note that the simple assertions \b and \B require a one-character look-
2751           behind.  \A  also  registers a one-character lookbehind, though it does
2752           not actually inspect the previous character. This is to ensure that  at
2753           least one character from the old segment is retained when a new segment
2754           is processed. Otherwise, if there are no lookbehinds in the pattern, \A
2755           might match incorrectly at the start of a new segment.
2756    
2757             PCRE_INFO_MINLENGTH
2758    
2759           If  the  pattern  was studied and a minimum length for matching subject
2760           strings was computed, its value is  returned.  Otherwise  the  returned
2761           value is -1. The value is a number of characters, which in UTF mode may
2762           be different from the number of data units. The fourth argument  should
2763           point  to an int variable. A non-negative value is a lower bound to the
2764           length of any matching string. There may not be  any  strings  of  that
2765           length  that  do actually match, but every string that does match is at
2766           least that long.
2767    
2768           PCRE_INFO_NAMECOUNT           PCRE_INFO_NAMECOUNT
2769           PCRE_INFO_NAMEENTRYSIZE           PCRE_INFO_NAMEENTRYSIZE
2770           PCRE_INFO_NAMETABLE           PCRE_INFO_NAMETABLE
2771    
2772         PCRE supports the use of named as well as numbered capturing  parenthe-         PCRE supports the use of named as well as numbered capturing  parenthe-
2773         ses.  The names are just an additional way of identifying the parenthe-         ses.  The names are just an additional way of identifying the parenthe-
2774         ses,  which  still  acquire  numbers.  A  convenience  function  called         ses, which still acquire numbers. Several convenience functions such as
2775         pcre_get_named_substring()  is  provided  for  extracting an individual         pcre_get_named_substring()  are  provided  for extracting captured sub-
2776         captured substring by name. It is also possible  to  extract  the  data         strings by name. It is also possible to extract the data  directly,  by
2777         directly,  by  first converting the name to a number in order to access         first  converting  the  name to a number in order to access the correct
2778         the correct pointers in the output vector (described  with  pcre_exec()         pointers in the output vector (described with pcre_exec() below). To do
2779         below).  To  do the conversion, you need to use the name-to-number map,         the  conversion,  you  need  to  use  the  name-to-number map, which is
2780         which is described by these three values.         described by these three values.
2781    
2782         The map consists of a number of fixed-size entries. PCRE_INFO_NAMECOUNT         The map consists of a number of fixed-size entries. PCRE_INFO_NAMECOUNT
2783         gives the number of entries, and PCRE_INFO_NAMEENTRYSIZE gives the size         gives the number of entries, and PCRE_INFO_NAMEENTRYSIZE gives the size
2784         of each entry; both of these  return  an  int  value.  The  entry  size         of each entry; both of these  return  an  int  value.  The  entry  size
2785         depends  on the length of the longest name. PCRE_INFO_NAMETABLE returns         depends  on the length of the longest name. PCRE_INFO_NAMETABLE returns
2786         a pointer to the first entry of the table  (a  pointer  to  char).  The         a pointer to the first entry of the table. This is a pointer to char in
2787         first two bytes of each entry are the number of the capturing parenthe-         the 8-bit library, where the first two bytes of each entry are the num-
2788         sis, most significant byte first. The rest of the entry is  the  corre-         ber of the capturing parenthesis, most significant byte first.  In  the
2789         sponding  name,  zero  terminated. The names are in alphabetical order.         16-bit  library,  the pointer points to 16-bit data units, the first of
2790         For example, consider the following pattern  (assume  PCRE_EXTENDED  is         which contains the parenthesis  number.  In  the  32-bit  library,  the
2791           pointer  points  to  32-bit data units, the first of which contains the
2792           parenthesis number. The rest of the entry is  the  corresponding  name,
2793           zero terminated.
2794    
2795           The  names are in alphabetical order. Duplicate names may appear if (?|
2796           is used to create multiple groups with the same number, as described in
2797           the  section  on  duplicate subpattern numbers in the pcrepattern page.
2798           Duplicate names for subpatterns with different  numbers  are  permitted
2799           only  if  PCRE_DUPNAMES  is  set. In all cases of duplicate names, they
2800           appear in the table in the order in which they were found in  the  pat-
2801           tern.  In  the  absence  of (?| this is the order of increasing number;
2802           when (?| is used this is not necessarily the case because later subpat-
2803           terns may have lower numbers.
2804    
2805           As  a  simple  example of the name/number table, consider the following
2806           pattern after compilation by the 8-bit library (assume PCRE_EXTENDED is
2807         set, so white space - including newlines - is ignored):         set, so white space - including newlines - is ignored):
2808    
2809           (?P<date> (?P<year>(\d\d)?\d\d) -           (?<date> (?<year>(\d\d)?\d\d) -
2810           (?P<month>\d\d) - (?P<day>\d\d) )           (?<month>\d\d) - (?<day>\d\d) )
2811    
2812         There  are  four  named subpatterns, so the table has four entries, and         There  are  four  named subpatterns, so the table has four entries, and
2813         each entry in the table is eight bytes long. The table is  as  follows,         each entry in the table is eight bytes long. The table is  as  follows,
# Line 1307  INFORMATION ABOUT A PATTERN Line 2820  INFORMATION ABOUT A PATTERN
2820           00 02 y  e  a  r  00 ??           00 02 y  e  a  r  00 ??
2821    
2822         When writing code to extract data  from  named  subpatterns  using  the         When writing code to extract data  from  named  subpatterns  using  the
2823         name-to-number map, remember that the length of each entry is likely to         name-to-number  map,  remember that the length of the entries is likely
2824         be different for each compiled pattern.         to be different for each compiled pattern.
2825    
2826             PCRE_INFO_OKPARTIAL
2827    
2828           Return 1  if  the  pattern  can  be  used  for  partial  matching  with
2829           pcre_exec(),  otherwise  0.  The fourth argument should point to an int
2830           variable. From  release  8.00,  this  always  returns  1,  because  the
2831           restrictions  that  previously  applied  to  partial matching have been
2832           lifted. The pcrepartial documentation gives details of  partial  match-
2833           ing.
2834    
2835           PCRE_INFO_OPTIONS           PCRE_INFO_OPTIONS
2836    
2837         Return a copy of the options with which the pattern was  compiled.  The         Return  a  copy of the options with which the pattern was compiled. The
2838         fourth  argument  should  point to an unsigned long int variable. These         fourth argument should point to an unsigned long  int  variable.  These
2839         option bits are those specified in the call to pcre_compile(), modified         option bits are those specified in the call to pcre_compile(), modified
2840         by any top-level option settings within the pattern itself.         by any top-level option settings at the start of the pattern itself. In
2841           other  words,  they are the options that will be in force when matching
2842           starts. For example, if the pattern /(?im)abc(?-i)d/ is  compiled  with
2843           the  PCRE_EXTENDED option, the result is PCRE_CASELESS, PCRE_MULTILINE,
2844           and PCRE_EXTENDED.
2845    
2846         A  pattern  is  automatically  anchored by PCRE if all of its top-level         A pattern is automatically anchored by PCRE if  all  of  its  top-level
2847         alternatives begin with one of the following:         alternatives begin with one of the following:
2848    
2849           ^     unless PCRE_MULTILINE is set           ^     unless PCRE_MULTILINE is set
# Line 1329  INFORMATION ABOUT A PATTERN Line 2855  INFORMATION ABOUT A PATTERN
2855         For such patterns, the PCRE_ANCHORED bit is set in the options returned         For such patterns, the PCRE_ANCHORED bit is set in the options returned
2856         by pcre_fullinfo().         by pcre_fullinfo().
2857    
2858             PCRE_INFO_RECURSIONLIMIT
2859    
2860           If the pattern set a recursion limit by including an item of  the  form
2861           (*LIMIT_RECURSION=nnnn) at the start, the value is returned. The fourth
2862           argument should point to an unsigned 32-bit integer. If no  such  value
2863           has   been   set,   the  call  to  pcre_fullinfo()  returns  the  error
2864           PCRE_ERROR_UNSET.
2865    
2866           PCRE_INFO_SIZE           PCRE_INFO_SIZE
2867    
2868         Return  the  size  of the compiled pattern, that is, the value that was         Return the size of  the  compiled  pattern  in  bytes  (for  all  three
2869         passed as the argument to pcre_malloc() when PCRE was getting memory in         libraries). The fourth argument should point to a size_t variable. This
2870         which to place the compiled data. The fourth argument should point to a         value does not include the size of the pcre structure that is  returned
2871         size_t variable.         by  pcre_compile().  The  value  that  is  passed  as  the  argument to
2872           pcre_malloc() when pcre_compile() is getting memory in which  to  place
2873           the compiled data is the value returned by this option plus the size of
2874           the pcre structure. Studying a compiled pattern, with or  without  JIT,
2875           does not alter the value returned by this option.
2876    
2877           PCRE_INFO_STUDYSIZE           PCRE_INFO_STUDYSIZE
2878    
2879         Return the size of the data block pointed to by the study_data field in         Return  the  size  in bytes (for all three libraries) of the data block
2880         a  pcre_extra  block.  That  is,  it  is  the  value that was passed to         pointed to by the study_data field in a pcre_extra block. If pcre_extra
2881         pcre_malloc() when PCRE was getting memory into which to place the data         is  NULL, or there is no study data, zero is returned. The fourth argu-
2882         created  by  pcre_study(). The fourth argument should point to a size_t         ment should point to a size_t variable. The study_data field is set  by
2883           pcre_study() to record information that will speed up matching (see the
2884           section entitled  "Studying  a  pattern"  above).  The  format  of  the
2885           study_data  block is private, but its length is made available via this
2886           option so that it can be saved and  restored  (see  the  pcreprecompile
2887           documentation for details).
2888    
2889             PCRE_INFO_FIRSTCHARACTERFLAGS
2890    
2891           Return information about the first data unit of any matched string, for
2892           a non-anchored pattern. The fourth argument  should  point  to  an  int
2893         variable.         variable.
2894    
2895           If  there  is  a  fixed first value, for example, the letter "c" from a
2896           pattern such as (cat|cow|coyote), 1  is  returned,  and  the  character
2897           value can be retrieved using PCRE_INFO_FIRSTCHARACTER.
2898    
2899           If there is no fixed first value, and if either
2900    
2901           (a)  the pattern was compiled with the PCRE_MULTILINE option, and every
2902           branch starts with "^", or
2903    
2904           (b) every branch of the pattern starts with ".*" and PCRE_DOTALL is not
2905           set (if it were set, the pattern would be anchored),
2906    
2907           2 is returned, indicating that the pattern matches only at the start of
2908           a subject string or after any newline within the string. Otherwise 0 is
2909           returned. For anchored patterns, 0 is returned.
2910    
2911             PCRE_INFO_FIRSTCHARACTER
2912    
2913           Return  the  fixed  first character value, if PCRE_INFO_FIRSTCHARACTER-
2914           FLAGS returned 1; otherwise returns 0. The fourth argument should point
2915           to an uint_t variable.
2916    
2917           In  the 8-bit library, the value is always less than 256. In the 16-bit
2918           library the value can be up to 0xffff. In the 32-bit library in  UTF-32
2919           mode  the  value  can  be up to 0x10ffff, and up to 0xffffffff when not
2920           using UTF-32 mode.
2921    
2922           If there is no fixed first value, and if either
2923    
2924           (a) the pattern was compiled with the PCRE_MULTILINE option, and  every
2925           branch starts with "^", or
2926    
2927           (b) every branch of the pattern starts with ".*" and PCRE_DOTALL is not
2928           set (if it were set, the pattern would be anchored),
2929    
2930  OBSOLETE INFO FUNCTION         -1 is returned, indicating that the pattern matches only at  the  start
2931           of  a  subject string or after any newline within the string. Otherwise
2932           -2 is returned. For anchored patterns, -2 is returned.
2933    
2934         int pcre_info(const pcre *code, int *optptr, int *firstcharptr);           PCRE_INFO_REQUIREDCHARFLAGS
2935    
2936         The pcre_info() function is now obsolete because its interface  is  too         Returns 1 if there is a rightmost literal data unit that must exist  in
2937         restrictive  to return all the available data about a compiled pattern.         any matched string, other than at its start. The fourth argument should
2938         New  programs  should  use  pcre_fullinfo()  instead.  The   yield   of         point to an int variable. If there is no such value, 0 is returned.  If
2939         pcre_info()  is the number of capturing subpatterns, or one of the fol-         returning  1,  the  character  value  itself  can  be  retrieved  using
2940         lowing negative numbers:         PCRE_INFO_REQUIREDCHAR.
2941    
2942           PCRE_ERROR_NULL       the argument code was NULL         For anchored patterns, a last literal value is recorded only if it fol-
2943           PCRE_ERROR_BADMAGIC   the "magic number" was not found         lows  something  of  variable  length.  For  example,  for  the pattern
2944           /^a\d+z\d+/  the   returned   value   1   (with   "z"   returned   from
2945         If the optptr argument is not NULL, a copy of the  options  with  which         PCRE_INFO_REQUIREDCHAR), but for /^a\dz\d/ the returned value is 0.
2946         the  pattern  was  compiled  is placed in the integer it points to (see  
2947         PCRE_INFO_OPTIONS above).           PCRE_INFO_REQUIREDCHAR
2948    
2949         If the pattern is not anchored and the  firstcharptr  argument  is  not         Return  the value of the rightmost literal data unit that must exist in
2950         NULL,  it is used to pass back information about the first character of         any matched string, other than at its start, if such a value  has  been
2951         any matched string (see PCRE_INFO_FIRSTBYTE above).         recorded.  The fourth argument should point to an uint32_t variable. If
2952           there is no such value, 0 is returned.
2953    
2954    
2955  REFERENCE COUNTS  REFERENCE COUNTS
# Line 1395  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 2980  MATCHING A PATTERN: THE TRADITIONAL FUNC
2980              const char *subject, int length, int startoffset,              const char *subject, int length, int startoffset,
2981              int options, int *ovector, int ovecsize);              int options, int *ovector, int ovecsize);
2982    
2983         The function pcre_exec() is called to match a subject string against  a         The  function pcre_exec() is called to match a subject string against a
2984         compiled  pattern, which is passed in the code argument. If the pattern         compiled pattern, which is passed in the code argument. If the  pattern
2985         has been studied, the result of the study should be passed in the extra         was  studied,  the  result  of  the study should be passed in the extra
2986         argument.  This  function is the main matching facility of the library,         argument. You can call pcre_exec() with the same code and  extra  argu-
2987         and it operates in a Perl-like manner. For specialist use there is also         ments  as  many  times as you like, in order to match different subject
2988         an  alternative matching function, which is described below in the sec-         strings with the same pattern.
2989         tion about the pcre_dfa_exec() function.  
2990           This function is the main matching facility  of  the  library,  and  it
2991           operates  in  a  Perl-like  manner. For specialist use there is also an
2992           alternative matching function, which is described below in the  section
2993           about the pcre_dfa_exec() function.
2994    
2995         In most applications, the pattern will have been compiled (and  option-         In  most applications, the pattern will have been compiled (and option-
2996         ally  studied)  in the same process that calls pcre_exec(). However, it         ally studied) in the same process that calls pcre_exec().  However,  it
2997         is possible to save compiled patterns and study data, and then use them         is possible to save compiled patterns and study data, and then use them
2998         later  in  different processes, possibly even on different hosts. For a         later in different processes, possibly even on different hosts.  For  a
2999         discussion about this, see the pcreprecompile documentation.         discussion about this, see the pcreprecompile documentation.
3000    
3001         Here is an example of a simple call to pcre_exec():         Here is an example of a simple call to pcre_exec():
# Line 1425  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 3014  MATCHING A PATTERN: THE TRADITIONAL FUNC
3014    
3015     Extra data for pcre_exec()     Extra data for pcre_exec()
3016    
3017         If the extra argument is not NULL, it must point to a  pcre_extra  data         If  the  extra argument is not NULL, it must point to a pcre_extra data
3018         block.  The pcre_study() function returns such a block (when it doesn't         block. The pcre_study() function returns such a block (when it  doesn't
3019         return NULL), but you can also create one for yourself, and pass  addi-         return  NULL), but you can also create one for yourself, and pass addi-
3020         tional  information in it. The fields in a pcre_extra block are as fol-         tional information in it. The pcre_extra block contains  the  following
3021         lows:         fields (not necessarily in this order):
3022    
3023           unsigned long int flags;           unsigned long int flags;
3024           void *study_data;           void *study_data;
3025             void *executable_jit;
3026           unsigned long int match_limit;           unsigned long int match_limit;
3027             unsigned long int match_limit_recursion;
3028           void *callout_data;           void *callout_data;
3029           const unsigned char *tables;           const unsigned char *tables;
3030             unsigned char **mark;
3031    
3032         The flags field is a bitmap that specifies which of  the  other  fields         In  the  16-bit  version  of  this  structure,  the mark field has type
3033         are set. The flag bits are:         "PCRE_UCHAR16 **".
3034    
3035           In the 32-bit version of  this  structure,  the  mark  field  has  type
3036           "PCRE_UCHAR32 **".
3037    
3038           The  flags  field is used to specify which of the other fields are set.
3039           The flag bits are:
3040    
          PCRE_EXTRA_STUDY_DATA  
          PCRE_EXTRA_MATCH_LIMIT  
3041           PCRE_EXTRA_CALLOUT_DATA           PCRE_EXTRA_CALLOUT_DATA
3042             PCRE_EXTRA_EXECUTABLE_JIT
3043             PCRE_EXTRA_MARK
3044             PCRE_EXTRA_MATCH_LIMIT
3045             PCRE_EXTRA_MATCH_LIMIT_RECURSION
3046             PCRE_EXTRA_STUDY_DATA
3047           PCRE_EXTRA_TABLES           PCRE_EXTRA_TABLES
3048    
3049         Other  flag  bits should be set to zero. The study_data field is set in         Other flag bits should be set to zero. The study_data field  and  some-
3050         the pcre_extra block that is returned by  pcre_study(),  together  with         times  the executable_jit field are set in the pcre_extra block that is
3051         the appropriate flag bit. You should not set this yourself, but you may         returned by pcre_study(), together with the appropriate flag bits.  You
3052         add to the block by setting the other fields  and  their  corresponding         should  not set these yourself, but you may add to the block by setting
3053         flag bits.         other fields and their corresponding flag bits.
3054    
3055         The match_limit field provides a means of preventing PCRE from using up         The match_limit field provides a means of preventing PCRE from using up
3056         a vast amount of resources when running patterns that are not going  to         a  vast amount of resources when running patterns that are not going to
3057         match,  but  which  have  a very large number of possibilities in their         match, but which have a very large number  of  possibilities  in  their
3058         search trees. The classic  example  is  the  use  of  nested  unlimited         search  trees. The classic example is a pattern that uses nested unlim-
3059         repeats.         ited repeats.
3060    
3061         Internally,  PCRE uses a function called match() which it calls repeat-         Internally, pcre_exec() uses a function called match(), which it  calls
3062         edly (sometimes recursively). The limit is imposed  on  the  number  of         repeatedly  (sometimes  recursively).  The  limit set by match_limit is
3063         times  this  function is called during a match, which has the effect of         imposed on the number of times this function is called during a  match,
3064         limiting the amount of recursion and backtracking that can take  place.         which  has  the  effect of limiting the amount of backtracking that can
3065         For patterns that are not anchored, the count starts from zero for each         take place. For patterns that are not anchored, the count restarts from
3066         position in the subject string.         zero for each position in the subject string.
3067    
3068           When pcre_exec() is called with a pattern that was successfully studied
3069           with a JIT option, the way that the matching is  executed  is  entirely
3070           different.  However, there is still the possibility of runaway matching
3071           that goes on for a very long time, and so the match_limit value is also
3072           used in this case (but in a different way) to limit how long the match-
3073           ing can continue.
3074    
3075         The default limit for the library can be set when PCRE  is  built;  the         The default value for the limit can be set  when  PCRE  is  built;  the
3076         default  default  is 10 million, which handles all but the most extreme         default  default  is 10 million, which handles all but the most extreme
3077         cases. You can reduce  the  default  by  suppling  pcre_exec()  with  a         cases. You can override the default  by  suppling  pcre_exec()  with  a
3078         pcre_extra  block  in  which match_limit is set to a smaller value, and         pcre_extra     block    in    which    match_limit    is    set,    and
3079         PCRE_EXTRA_MATCH_LIMIT is set in the  flags  field.  If  the  limit  is         PCRE_EXTRA_MATCH_LIMIT is set in the  flags  field.  If  the  limit  is
3080         exceeded, pcre_exec() returns PCRE_ERROR_MATCHLIMIT.         exceeded, pcre_exec() returns PCRE_ERROR_MATCHLIMIT.
3081    
3082         The  pcre_callout  field is used in conjunction with the "callout" fea-         A  value  for  the  match  limit may also be supplied by an item at the
3083         ture, which is described in the pcrecallout documentation.         start of a pattern of the form
3084    
3085             (*LIMIT_MATCH=d)
3086    
3087         The tables field  is  used  to  pass  a  character  tables  pointer  to         where d is a decimal number. However, such a setting is ignored  unless
3088         pcre_exec();  this overrides the value that is stored with the compiled         d  is  less  than  the limit set by the caller of pcre_exec() or, if no
3089         pattern. A non-NULL value is stored with the compiled pattern  only  if         such limit is set, less than the default.
3090         custom  tables  were  supplied to pcre_compile() via its tableptr argu-  
3091           The match_limit_recursion field is similar to match_limit, but  instead
3092           of limiting the total number of times that match() is called, it limits
3093           the depth of recursion. The recursion depth is a  smaller  number  than
3094           the  total number of calls, because not all calls to match() are recur-
3095           sive.  This limit is of use only if it is set smaller than match_limit.
3096    
3097           Limiting the recursion depth limits the amount of  machine  stack  that
3098           can  be used, or, when PCRE has been compiled to use memory on the heap
3099           instead of the stack, the amount of heap memory that can be used.  This
3100           limit  is not relevant, and is ignored, when matching is done using JIT
3101           compiled code.
3102    
3103           The default value for match_limit_recursion can be  set  when  PCRE  is
3104           built;  the  default  default  is  the  same  value  as the default for
3105           match_limit. You can override the default by suppling pcre_exec()  with
3106           a   pcre_extra   block  in  which  match_limit_recursion  is  set,  and
3107           PCRE_EXTRA_MATCH_LIMIT_RECURSION is set in  the  flags  field.  If  the
3108           limit is exceeded, pcre_exec() returns PCRE_ERROR_RECURSIONLIMIT.
3109    
3110           A  value for the recursion limit may also be supplied by an item at the
3111           start of a pattern of the form
3112    
3113             (*LIMIT_RECURSION=d)
3114    
3115           where d is a decimal number. However, such a setting is ignored  unless
3116           d  is  less  than  the limit set by the caller of pcre_exec() or, if no
3117           such limit is set, less than the default.
3118    
3119           The callout_data field is used in conjunction with the  "callout"  fea-
3120           ture, and is described in the pcrecallout documentation.
3121    
3122           The  tables  field  is  used  to  pass  a  character  tables pointer to
3123           pcre_exec(); this overrides the value that is stored with the  compiled
3124           pattern.  A  non-NULL value is stored with the compiled pattern only if
3125           custom tables were supplied to pcre_compile() via  its  tableptr  argu-
3126         ment.  If NULL is passed to pcre_exec() using this mechanism, it forces         ment.  If NULL is passed to pcre_exec() using this mechanism, it forces
3127         PCRE's  internal  tables  to be used. This facility is helpful when re-         PCRE's internal tables to be used. This facility is  helpful  when  re-
3128         using patterns that have been saved after compiling  with  an  external         using  patterns  that  have been saved after compiling with an external
3129         set  of  tables,  because  the  external tables might be at a different         set of tables, because the external tables  might  be  at  a  different
3130         address when pcre_exec() is called. See the  pcreprecompile  documenta-         address  when  pcre_exec() is called. See the pcreprecompile documenta-
3131         tion for a discussion of saving compiled patterns for later use.         tion for a discussion of saving compiled patterns for later use.
3132    
3133           If PCRE_EXTRA_MARK is set in the flags field, the mark  field  must  be
3134           set  to point to a suitable variable. If the pattern contains any back-
3135           tracking control verbs such as (*MARK:NAME), and the execution ends  up
3136           with  a  name  to  pass back, a pointer to the name string (zero termi-
3137           nated) is placed in the variable pointed to  by  the  mark  field.  The
3138           names  are  within  the  compiled pattern; if you wish to retain such a
3139           name you must copy it before freeing the memory of a compiled  pattern.
3140           If  there  is no name to pass back, the variable pointed t