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1 <html>
2 <head>
3 <title>pcreapi specification</title>
4 </head>
5 <body bgcolor="#FFFFFF" text="#00005A" link="#0066FF" alink="#3399FF" vlink="#2222BB">
6 <h1>pcreapi man page</h1>
7 <p>
8 Return to the <a href="index.html">PCRE index page</a>.
9 </p>
10 <p>
11 This page is part of the PCRE HTML documentation. It was generated automatically
12 from the original man page. If there is any nonsense in it, please consult the
13 man page, in case the conversion went wrong.
14 <br>
15 <ul>
16 <li><a name="TOC1" href="#SEC1">PCRE NATIVE API</a>
17 <li><a name="TOC2" href="#SEC2">PCRE API OVERVIEW</a>
18 <li><a name="TOC3" href="#SEC3">NEWLINES</a>
19 <li><a name="TOC4" href="#SEC4">MULTITHREADING</a>
21 <li><a name="TOC6" href="#SEC6">CHECKING BUILD-TIME OPTIONS</a>
22 <li><a name="TOC7" href="#SEC7">COMPILING A PATTERN</a>
23 <li><a name="TOC8" href="#SEC8">COMPILATION ERROR CODES</a>
24 <li><a name="TOC9" href="#SEC9">STUDYING A PATTERN</a>
25 <li><a name="TOC10" href="#SEC10">LOCALE SUPPORT</a>
26 <li><a name="TOC11" href="#SEC11">INFORMATION ABOUT A PATTERN</a>
27 <li><a name="TOC12" href="#SEC12">OBSOLETE INFO FUNCTION</a>
28 <li><a name="TOC13" href="#SEC13">REFERENCE COUNTS</a>
32 <li><a name="TOC17" href="#SEC17">DUPLICATE SUBPATTERN NAMES</a>
33 <li><a name="TOC18" href="#SEC18">FINDING ALL POSSIBLE MATCHES</a>
35 <li><a name="TOC20" href="#SEC20">SEE ALSO</a>
36 <li><a name="TOC21" href="#SEC21">AUTHOR</a>
37 <li><a name="TOC22" href="#SEC22">REVISION</a>
38 </ul>
39 <br><a name="SEC1" href="#TOC1">PCRE NATIVE API</a><br>
40 <P>
41 <b>#include &#60;pcre.h&#62;</b>
42 </P>
43 <P>
44 <b>pcre *pcre_compile(const char *<i>pattern</i>, int <i>options</i>,</b>
45 <b>const char **<i>errptr</i>, int *<i>erroffset</i>,</b>
46 <b>const unsigned char *<i>tableptr</i>);</b>
47 </P>
48 <P>
49 <b>pcre *pcre_compile2(const char *<i>pattern</i>, int <i>options</i>,</b>
50 <b>int *<i>errorcodeptr</i>,</b>
51 <b>const char **<i>errptr</i>, int *<i>erroffset</i>,</b>
52 <b>const unsigned char *<i>tableptr</i>);</b>
53 </P>
54 <P>
55 <b>pcre_extra *pcre_study(const pcre *<i>code</i>, int <i>options</i>,</b>
56 <b>const char **<i>errptr</i>);</b>
57 </P>
58 <P>
59 <b>int pcre_exec(const pcre *<i>code</i>, const pcre_extra *<i>extra</i>,</b>
60 <b>const char *<i>subject</i>, int <i>length</i>, int <i>startoffset</i>,</b>
61 <b>int <i>options</i>, int *<i>ovector</i>, int <i>ovecsize</i>);</b>
62 </P>
63 <P>
64 <b>int pcre_dfa_exec(const pcre *<i>code</i>, const pcre_extra *<i>extra</i>,</b>
65 <b>const char *<i>subject</i>, int <i>length</i>, int <i>startoffset</i>,</b>
66 <b>int <i>options</i>, int *<i>ovector</i>, int <i>ovecsize</i>,</b>
67 <b>int *<i>workspace</i>, int <i>wscount</i>);</b>
68 </P>
69 <P>
70 <b>int pcre_copy_named_substring(const pcre *<i>code</i>,</b>
71 <b>const char *<i>subject</i>, int *<i>ovector</i>,</b>
72 <b>int <i>stringcount</i>, const char *<i>stringname</i>,</b>
73 <b>char *<i>buffer</i>, int <i>buffersize</i>);</b>
74 </P>
75 <P>
76 <b>int pcre_copy_substring(const char *<i>subject</i>, int *<i>ovector</i>,</b>
77 <b>int <i>stringcount</i>, int <i>stringnumber</i>, char *<i>buffer</i>,</b>
78 <b>int <i>buffersize</i>);</b>
79 </P>
80 <P>
81 <b>int pcre_get_named_substring(const pcre *<i>code</i>,</b>
82 <b>const char *<i>subject</i>, int *<i>ovector</i>,</b>
83 <b>int <i>stringcount</i>, const char *<i>stringname</i>,</b>
84 <b>const char **<i>stringptr</i>);</b>
85 </P>
86 <P>
87 <b>int pcre_get_stringnumber(const pcre *<i>code</i>,</b>
88 <b>const char *<i>name</i>);</b>
89 </P>
90 <P>
91 <b>int pcre_get_stringtable_entries(const pcre *<i>code</i>,</b>
92 <b>const char *<i>name</i>, char **<i>first</i>, char **<i>last</i>);</b>
93 </P>
94 <P>
95 <b>int pcre_get_substring(const char *<i>subject</i>, int *<i>ovector</i>,</b>
96 <b>int <i>stringcount</i>, int <i>stringnumber</i>,</b>
97 <b>const char **<i>stringptr</i>);</b>
98 </P>
99 <P>
100 <b>int pcre_get_substring_list(const char *<i>subject</i>,</b>
101 <b>int *<i>ovector</i>, int <i>stringcount</i>, const char ***<i>listptr</i>);</b>
102 </P>
103 <P>
104 <b>void pcre_free_substring(const char *<i>stringptr</i>);</b>
105 </P>
106 <P>
107 <b>void pcre_free_substring_list(const char **<i>stringptr</i>);</b>
108 </P>
109 <P>
110 <b>const unsigned char *pcre_maketables(void);</b>
111 </P>
112 <P>
113 <b>int pcre_fullinfo(const pcre *<i>code</i>, const pcre_extra *<i>extra</i>,</b>
114 <b>int <i>what</i>, void *<i>where</i>);</b>
115 </P>
116 <P>
117 <b>int pcre_info(const pcre *<i>code</i>, int *<i>optptr</i>, int</b>
118 <b>*<i>firstcharptr</i>);</b>
119 </P>
120 <P>
121 <b>int pcre_refcount(pcre *<i>code</i>, int <i>adjust</i>);</b>
122 </P>
123 <P>
124 <b>int pcre_config(int <i>what</i>, void *<i>where</i>);</b>
125 </P>
126 <P>
127 <b>char *pcre_version(void);</b>
128 </P>
129 <P>
130 <b>void *(*pcre_malloc)(size_t);</b>
131 </P>
132 <P>
133 <b>void (*pcre_free)(void *);</b>
134 </P>
135 <P>
136 <b>void *(*pcre_stack_malloc)(size_t);</b>
137 </P>
138 <P>
139 <b>void (*pcre_stack_free)(void *);</b>
140 </P>
141 <P>
142 <b>int (*pcre_callout)(pcre_callout_block *);</b>
143 </P>
144 <br><a name="SEC2" href="#TOC1">PCRE API OVERVIEW</a><br>
145 <P>
146 PCRE has its own native API, which is described in this document. There are
147 also some wrapper functions that correspond to the POSIX regular expression
148 API. These are described in the
149 <a href="pcreposix.html"><b>pcreposix</b></a>
150 documentation. Both of these APIs define a set of C function calls. A C++
151 wrapper is distributed with PCRE. It is documented in the
152 <a href="pcrecpp.html"><b>pcrecpp</b></a>
153 page.
154 </P>
155 <P>
156 The native API C function prototypes are defined in the header file
157 <b>pcre.h</b>, and on Unix systems the library itself is called <b>libpcre</b>.
158 It can normally be accessed by adding <b>-lpcre</b> to the command for linking
159 an application that uses PCRE. The header file defines the macros PCRE_MAJOR
160 and PCRE_MINOR to contain the major and minor release numbers for the library.
161 Applications can use these to include support for different releases of PCRE.
162 </P>
163 <P>
164 The functions <b>pcre_compile()</b>, <b>pcre_compile2()</b>, <b>pcre_study()</b>,
165 and <b>pcre_exec()</b> are used for compiling and matching regular expressions
166 in a Perl-compatible manner. A sample program that demonstrates the simplest
167 way of using them is provided in the file called <i>pcredemo.c</i> in the PCRE
168 source distribution. A listing of this program is given in the
169 <a href="pcredemo.html"><b>pcredemo</b></a>
170 documentation, and the
171 <a href="pcresample.html"><b>pcresample</b></a>
172 documentation describes how to compile and run it.
173 </P>
174 <P>
175 A second matching function, <b>pcre_dfa_exec()</b>, which is not
176 Perl-compatible, is also provided. This uses a different algorithm for the
177 matching. The alternative algorithm finds all possible matches (at a given
178 point in the subject), and scans the subject just once. However, this algorithm
179 does not return captured substrings. A description of the two matching
180 algorithms and their advantages and disadvantages is given in the
181 <a href="pcrematching.html"><b>pcrematching</b></a>
182 documentation.
183 </P>
184 <P>
185 In addition to the main compiling and matching functions, there are convenience
186 functions for extracting captured substrings from a subject string that is
187 matched by <b>pcre_exec()</b>. They are:
188 <pre>
189 <b>pcre_copy_substring()</b>
190 <b>pcre_copy_named_substring()</b>
191 <b>pcre_get_substring()</b>
192 <b>pcre_get_named_substring()</b>
193 <b>pcre_get_substring_list()</b>
194 <b>pcre_get_stringnumber()</b>
195 <b>pcre_get_stringtable_entries()</b>
196 </pre>
197 <b>pcre_free_substring()</b> and <b>pcre_free_substring_list()</b> are also
198 provided, to free the memory used for extracted strings.
199 </P>
200 <P>
201 The function <b>pcre_maketables()</b> is used to build a set of character tables
202 in the current locale for passing to <b>pcre_compile()</b>, <b>pcre_exec()</b>,
203 or <b>pcre_dfa_exec()</b>. This is an optional facility that is provided for
204 specialist use. Most commonly, no special tables are passed, in which case
205 internal tables that are generated when PCRE is built are used.
206 </P>
207 <P>
208 The function <b>pcre_fullinfo()</b> is used to find out information about a
209 compiled pattern; <b>pcre_info()</b> is an obsolete version that returns only
210 some of the available information, but is retained for backwards compatibility.
211 The function <b>pcre_version()</b> returns a pointer to a string containing the
212 version of PCRE and its date of release.
213 </P>
214 <P>
215 The function <b>pcre_refcount()</b> maintains a reference count in a data block
216 containing a compiled pattern. This is provided for the benefit of
217 object-oriented applications.
218 </P>
219 <P>
220 The global variables <b>pcre_malloc</b> and <b>pcre_free</b> initially contain
221 the entry points of the standard <b>malloc()</b> and <b>free()</b> functions,
222 respectively. PCRE calls the memory management functions via these variables,
223 so a calling program can replace them if it wishes to intercept the calls. This
224 should be done before calling any PCRE functions.
225 </P>
226 <P>
227 The global variables <b>pcre_stack_malloc</b> and <b>pcre_stack_free</b> are also
228 indirections to memory management functions. These special functions are used
229 only when PCRE is compiled to use the heap for remembering data, instead of
230 recursive function calls, when running the <b>pcre_exec()</b> function. See the
231 <a href="pcrebuild.html"><b>pcrebuild</b></a>
232 documentation for details of how to do this. It is a non-standard way of
233 building PCRE, for use in environments that have limited stacks. Because of the
234 greater use of memory management, it runs more slowly. Separate functions are
235 provided so that special-purpose external code can be used for this case. When
236 used, these functions are always called in a stack-like manner (last obtained,
237 first freed), and always for memory blocks of the same size. There is a
238 discussion about PCRE's stack usage in the
239 <a href="pcrestack.html"><b>pcrestack</b></a>
240 documentation.
241 </P>
242 <P>
243 The global variable <b>pcre_callout</b> initially contains NULL. It can be set
244 by the caller to a "callout" function, which PCRE will then call at specified
245 points during a matching operation. Details are given in the
246 <a href="pcrecallout.html"><b>pcrecallout</b></a>
247 documentation.
248 <a name="newlines"></a></P>
249 <br><a name="SEC3" href="#TOC1">NEWLINES</a><br>
250 <P>
251 PCRE supports five different conventions for indicating line breaks in
252 strings: a single CR (carriage return) character, a single LF (linefeed)
253 character, the two-character sequence CRLF, any of the three preceding, or any
254 Unicode newline sequence. The Unicode newline sequences are the three just
255 mentioned, plus the single characters VT (vertical tab, U+000B), FF (formfeed,
256 U+000C), NEL (next line, U+0085), LS (line separator, U+2028), and PS
257 (paragraph separator, U+2029).
258 </P>
259 <P>
260 Each of the first three conventions is used by at least one operating system as
261 its standard newline sequence. When PCRE is built, a default can be specified.
262 The default default is LF, which is the Unix standard. When PCRE is run, the
263 default can be overridden, either when a pattern is compiled, or when it is
264 matched.
265 </P>
266 <P>
267 At compile time, the newline convention can be specified by the <i>options</i>
268 argument of <b>pcre_compile()</b>, or it can be specified by special text at the
269 start of the pattern itself; this overrides any other settings. See the
270 <a href="pcrepattern.html"><b>pcrepattern</b></a>
271 page for details of the special character sequences.
272 </P>
273 <P>
274 In the PCRE documentation the word "newline" is used to mean "the character or
275 pair of characters that indicate a line break". The choice of newline
276 convention affects the handling of the dot, circumflex, and dollar
277 metacharacters, the handling of #-comments in /x mode, and, when CRLF is a
278 recognized line ending sequence, the match position advancement for a
279 non-anchored pattern. There is more detail about this in the
280 <a href="#execoptions">section on <b>pcre_exec()</b> options</a>
281 below.
282 </P>
283 <P>
284 The choice of newline convention does not affect the interpretation of
285 the \n or \r escape sequences, nor does it affect what \R matches, which is
286 controlled in a similar way, but by separate options.
287 </P>
288 <br><a name="SEC4" href="#TOC1">MULTITHREADING</a><br>
289 <P>
290 The PCRE functions can be used in multi-threading applications, with the
291 proviso that the memory management functions pointed to by <b>pcre_malloc</b>,
292 <b>pcre_free</b>, <b>pcre_stack_malloc</b>, and <b>pcre_stack_free</b>, and the
293 callout function pointed to by <b>pcre_callout</b>, are shared by all threads.
294 </P>
295 <P>
296 The compiled form of a regular expression is not altered during matching, so
297 the same compiled pattern can safely be used by several threads at once.
298 </P>
299 <br><a name="SEC5" href="#TOC1">SAVING PRECOMPILED PATTERNS FOR LATER USE</a><br>
300 <P>
301 The compiled form of a regular expression can be saved and re-used at a later
302 time, possibly by a different program, and even on a host other than the one on
303 which it was compiled. Details are given in the
304 <a href="pcreprecompile.html"><b>pcreprecompile</b></a>
305 documentation. However, compiling a regular expression with one version of PCRE
306 for use with a different version is not guaranteed to work and may cause
307 crashes.
308 </P>
309 <br><a name="SEC6" href="#TOC1">CHECKING BUILD-TIME OPTIONS</a><br>
310 <P>
311 <b>int pcre_config(int <i>what</i>, void *<i>where</i>);</b>
312 </P>
313 <P>
314 The function <b>pcre_config()</b> makes it possible for a PCRE client to
315 discover which optional features have been compiled into the PCRE library. The
316 <a href="pcrebuild.html"><b>pcrebuild</b></a>
317 documentation has more details about these optional features.
318 </P>
319 <P>
320 The first argument for <b>pcre_config()</b> is an integer, specifying which
321 information is required; the second argument is a pointer to a variable into
322 which the information is placed. The following information is available:
323 <pre>
325 </pre>
326 The output is an integer that is set to one if UTF-8 support is available;
327 otherwise it is set to zero.
328 <pre>
330 </pre>
331 The output is an integer that is set to one if support for Unicode character
332 properties is available; otherwise it is set to zero.
333 <pre>
335 </pre>
336 The output is an integer whose value specifies the default character sequence
337 that is recognized as meaning "newline". The four values that are supported
338 are: 10 for LF, 13 for CR, 3338 for CRLF, -2 for ANYCRLF, and -1 for ANY.
339 Though they are derived from ASCII, the same values are returned in EBCDIC
340 environments. The default should normally correspond to the standard sequence
341 for your operating system.
342 <pre>
344 </pre>
345 The output is an integer whose value indicates what character sequences the \R
346 escape sequence matches by default. A value of 0 means that \R matches any
347 Unicode line ending sequence; a value of 1 means that \R matches only CR, LF,
348 or CRLF. The default can be overridden when a pattern is compiled or matched.
349 <pre>
351 </pre>
352 The output is an integer that contains the number of bytes used for internal
353 linkage in compiled regular expressions. The value is 2, 3, or 4. Larger values
354 allow larger regular expressions to be compiled, at the expense of slower
355 matching. The default value of 2 is sufficient for all but the most massive
356 patterns, since it allows the compiled pattern to be up to 64K in size.
357 <pre>
359 </pre>
360 The output is an integer that contains the threshold above which the POSIX
361 interface uses <b>malloc()</b> for output vectors. Further details are given in
362 the
363 <a href="pcreposix.html"><b>pcreposix</b></a>
364 documentation.
365 <pre>
367 </pre>
368 The output is a long integer that gives the default limit for the number of
369 internal matching function calls in a <b>pcre_exec()</b> execution. Further
370 details are given with <b>pcre_exec()</b> below.
371 <pre>
373 </pre>
374 The output is a long integer that gives the default limit for the depth of
375 recursion when calling the internal matching function in a <b>pcre_exec()</b>
376 execution. Further details are given with <b>pcre_exec()</b> below.
377 <pre>
379 </pre>
380 The output is an integer that is set to one if internal recursion when running
381 <b>pcre_exec()</b> is implemented by recursive function calls that use the stack
382 to remember their state. This is the usual way that PCRE is compiled. The
383 output is zero if PCRE was compiled to use blocks of data on the heap instead
384 of recursive function calls. In this case, <b>pcre_stack_malloc</b> and
385 <b>pcre_stack_free</b> are called to manage memory blocks on the heap, thus
386 avoiding the use of the stack.
387 </P>
388 <br><a name="SEC7" href="#TOC1">COMPILING A PATTERN</a><br>
389 <P>
390 <b>pcre *pcre_compile(const char *<i>pattern</i>, int <i>options</i>,</b>
391 <b>const char **<i>errptr</i>, int *<i>erroffset</i>,</b>
392 <b>const unsigned char *<i>tableptr</i>);</b>
393 <b>pcre *pcre_compile2(const char *<i>pattern</i>, int <i>options</i>,</b>
394 <b>int *<i>errorcodeptr</i>,</b>
395 <b>const char **<i>errptr</i>, int *<i>erroffset</i>,</b>
396 <b>const unsigned char *<i>tableptr</i>);</b>
397 </P>
398 <P>
399 Either of the functions <b>pcre_compile()</b> or <b>pcre_compile2()</b> can be
400 called to compile a pattern into an internal form. The only difference between
401 the two interfaces is that <b>pcre_compile2()</b> has an additional argument,
402 <i>errorcodeptr</i>, via which a numerical error code can be returned.
403 </P>
404 <P>
405 The pattern is a C string terminated by a binary zero, and is passed in the
406 <i>pattern</i> argument. A pointer to a single block of memory that is obtained
407 via <b>pcre_malloc</b> is returned. This contains the compiled code and related
408 data. The <b>pcre</b> type is defined for the returned block; this is a typedef
409 for a structure whose contents are not externally defined. It is up to the
410 caller to free the memory (via <b>pcre_free</b>) when it is no longer required.
411 </P>
412 <P>
413 Although the compiled code of a PCRE regex is relocatable, that is, it does not
414 depend on memory location, the complete <b>pcre</b> data block is not
415 fully relocatable, because it may contain a copy of the <i>tableptr</i>
416 argument, which is an address (see below).
417 </P>
418 <P>
419 The <i>options</i> argument contains various bit settings that affect the
420 compilation. It should be zero if no options are required. The available
421 options are described below. Some of them (in particular, those that are
422 compatible with Perl, but also some others) can also be set and unset from
423 within the pattern (see the detailed description in the
424 <a href="pcrepattern.html"><b>pcrepattern</b></a>
425 documentation). For those options that can be different in different parts of
426 the pattern, the contents of the <i>options</i> argument specifies their initial
427 settings at the start of compilation and execution. The PCRE_ANCHORED and
428 PCRE_NEWLINE_<i>xxx</i> options can be set at the time of matching as well as at
429 compile time.
430 </P>
431 <P>
432 If <i>errptr</i> is NULL, <b>pcre_compile()</b> returns NULL immediately.
433 Otherwise, if compilation of a pattern fails, <b>pcre_compile()</b> returns
434 NULL, and sets the variable pointed to by <i>errptr</i> to point to a textual
435 error message. This is a static string that is part of the library. You must
436 not try to free it. The offset from the start of the pattern to the character
437 where the error was discovered is placed in the variable pointed to by
438 <i>erroffset</i>, which must not be NULL. If it is, an immediate error is given.
439 </P>
440 <P>
441 If <b>pcre_compile2()</b> is used instead of <b>pcre_compile()</b>, and the
442 <i>errorcodeptr</i> argument is not NULL, a non-zero error code number is
443 returned via this argument in the event of an error. This is in addition to the
444 textual error message. Error codes and messages are listed below.
445 </P>
446 <P>
447 If the final argument, <i>tableptr</i>, is NULL, PCRE uses a default set of
448 character tables that are built when PCRE is compiled, using the default C
449 locale. Otherwise, <i>tableptr</i> must be an address that is the result of a
450 call to <b>pcre_maketables()</b>. This value is stored with the compiled
451 pattern, and used again by <b>pcre_exec()</b>, unless another table pointer is
452 passed to it. For more discussion, see the section on locale support below.
453 </P>
454 <P>
455 This code fragment shows a typical straightforward call to <b>pcre_compile()</b>:
456 <pre>
457 pcre *re;
458 const char *error;
459 int erroffset;
460 re = pcre_compile(
461 "^A.*Z", /* the pattern */
462 0, /* default options */
463 &error, /* for error message */
464 &erroffset, /* for error offset */
465 NULL); /* use default character tables */
466 </pre>
467 The following names for option bits are defined in the <b>pcre.h</b> header
468 file:
469 <pre>
471 </pre>
472 If this bit is set, the pattern is forced to be "anchored", that is, it is
473 constrained to match only at the first matching point in the string that is
474 being searched (the "subject string"). This effect can also be achieved by
475 appropriate constructs in the pattern itself, which is the only way to do it in
476 Perl.
477 <pre>
479 </pre>
480 If this bit is set, <b>pcre_compile()</b> automatically inserts callout items,
481 all with number 255, before each pattern item. For discussion of the callout
482 facility, see the
483 <a href="pcrecallout.html"><b>pcrecallout</b></a>
484 documentation.
485 <pre>
488 </pre>
489 These options (which are mutually exclusive) control what the \R escape
490 sequence matches. The choice is either to match only CR, LF, or CRLF, or to
491 match any Unicode newline sequence. The default is specified when PCRE is
492 built. It can be overridden from within the pattern, or by setting an option
493 when a compiled pattern is matched.
494 <pre>
496 </pre>
497 If this bit is set, letters in the pattern match both upper and lower case
498 letters. It is equivalent to Perl's /i option, and it can be changed within a
499 pattern by a (?i) option setting. In UTF-8 mode, PCRE always understands the
500 concept of case for characters whose values are less than 128, so caseless
501 matching is always possible. For characters with higher values, the concept of
502 case is supported if PCRE is compiled with Unicode property support, but not
503 otherwise. If you want to use caseless matching for characters 128 and above,
504 you must ensure that PCRE is compiled with Unicode property support as well as
505 with UTF-8 support.
506 <pre>
508 </pre>
509 If this bit is set, a dollar metacharacter in the pattern matches only at the
510 end of the subject string. Without this option, a dollar also matches
511 immediately before a newline at the end of the string (but not before any other
512 newlines). The PCRE_DOLLAR_ENDONLY option is ignored if PCRE_MULTILINE is set.
513 There is no equivalent to this option in Perl, and no way to set it within a
514 pattern.
515 <pre>
517 </pre>
518 If this bit is set, a dot metacharater in the pattern matches all characters,
519 including those that indicate newline. Without it, a dot does not match when
520 the current position is at a newline. This option is equivalent to Perl's /s
521 option, and it can be changed within a pattern by a (?s) option setting. A
522 negative class such as [^a] always matches newline characters, independent of
523 the setting of this option.
524 <pre>
526 </pre>
527 If this bit is set, names used to identify capturing subpatterns need not be
528 unique. This can be helpful for certain types of pattern when it is known that
529 only one instance of the named subpattern can ever be matched. There are more
530 details of named subpatterns below; see also the
531 <a href="pcrepattern.html"><b>pcrepattern</b></a>
532 documentation.
533 <pre>
535 </pre>
536 If this bit is set, whitespace data characters in the pattern are totally
537 ignored except when escaped or inside a character class. Whitespace does not
538 include the VT character (code 11). In addition, characters between an
539 unescaped # outside a character class and the next newline, inclusive, are also
540 ignored. This is equivalent to Perl's /x option, and it can be changed within a
541 pattern by a (?x) option setting.
542 </P>
543 <P>
544 This option makes it possible to include comments inside complicated patterns.
545 Note, however, that this applies only to data characters. Whitespace characters
546 may never appear within special character sequences in a pattern, for example
547 within the sequence (?( which introduces a conditional subpattern.
548 <pre>
550 </pre>
551 This option was invented in order to turn on additional functionality of PCRE
552 that is incompatible with Perl, but it is currently of very little use. When
553 set, any backslash in a pattern that is followed by a letter that has no
554 special meaning causes an error, thus reserving these combinations for future
555 expansion. By default, as in Perl, a backslash followed by a letter with no
556 special meaning is treated as a literal. (Perl can, however, be persuaded to
557 give a warning for this.) There are at present no other features controlled by
558 this option. It can also be set by a (?X) option setting within a pattern.
559 <pre>
561 </pre>
562 If this option is set, an unanchored pattern is required to match before or at
563 the first newline in the subject string, though the matched text may continue
564 over the newline.
565 <pre>
567 </pre>
568 If this option is set, PCRE's behaviour is changed in some ways so that it is
569 compatible with JavaScript rather than Perl. The changes are as follows:
570 </P>
571 <P>
572 (1) A lone closing square bracket in a pattern causes a compile-time error,
573 because this is illegal in JavaScript (by default it is treated as a data
574 character). Thus, the pattern AB]CD becomes illegal when this option is set.
575 </P>
576 <P>
577 (2) At run time, a back reference to an unset subpattern group matches an empty
578 string (by default this causes the current matching alternative to fail). A
579 pattern such as (\1)(a) succeeds when this option is set (assuming it can find
580 an "a" in the subject), whereas it fails by default, for Perl compatibility.
581 <pre>
583 </pre>
584 By default, PCRE treats the subject string as consisting of a single line of
585 characters (even if it actually contains newlines). The "start of line"
586 metacharacter (^) matches only at the start of the string, while the "end of
587 line" metacharacter ($) matches only at the end of the string, or before a
588 terminating newline (unless PCRE_DOLLAR_ENDONLY is set). This is the same as
589 Perl.
590 </P>
591 <P>
592 When PCRE_MULTILINE it is set, the "start of line" and "end of line" constructs
593 match immediately following or immediately before internal newlines in the
594 subject string, respectively, as well as at the very start and end. This is
595 equivalent to Perl's /m option, and it can be changed within a pattern by a
596 (?m) option setting. If there are no newlines in a subject string, or no
597 occurrences of ^ or $ in a pattern, setting PCRE_MULTILINE has no effect.
598 <pre>
604 </pre>
605 These options override the default newline definition that was chosen when PCRE
606 was built. Setting the first or the second specifies that a newline is
607 indicated by a single character (CR or LF, respectively). Setting
608 PCRE_NEWLINE_CRLF specifies that a newline is indicated by the two-character
609 CRLF sequence. Setting PCRE_NEWLINE_ANYCRLF specifies that any of the three
610 preceding sequences should be recognized. Setting PCRE_NEWLINE_ANY specifies
611 that any Unicode newline sequence should be recognized. The Unicode newline
612 sequences are the three just mentioned, plus the single characters VT (vertical
613 tab, U+000B), FF (formfeed, U+000C), NEL (next line, U+0085), LS (line
614 separator, U+2028), and PS (paragraph separator, U+2029). The last two are
615 recognized only in UTF-8 mode.
616 </P>
617 <P>
618 The newline setting in the options word uses three bits that are treated
619 as a number, giving eight possibilities. Currently only six are used (default
620 plus the five values above). This means that if you set more than one newline
621 option, the combination may or may not be sensible. For example,
623 other combinations may yield unused numbers and cause an error.
624 </P>
625 <P>
626 The only time that a line break is specially recognized when compiling a
627 pattern is if PCRE_EXTENDED is set, and an unescaped # outside a character
628 class is encountered. This indicates a comment that lasts until after the next
629 line break sequence. In other circumstances, line break sequences are treated
630 as literal data, except that in PCRE_EXTENDED mode, both CR and LF are treated
631 as whitespace characters and are therefore ignored.
632 </P>
633 <P>
634 The newline option that is set at compile time becomes the default that is used
635 for <b>pcre_exec()</b> and <b>pcre_dfa_exec()</b>, but it can be overridden.
636 <pre>
638 </pre>
639 If this option is set, it disables the use of numbered capturing parentheses in
640 the pattern. Any opening parenthesis that is not followed by ? behaves as if it
641 were followed by ?: but named parentheses can still be used for capturing (and
642 they acquire numbers in the usual way). There is no equivalent of this option
643 in Perl.
644 <pre>
646 </pre>
647 This option inverts the "greediness" of the quantifiers so that they are not
648 greedy by default, but become greedy if followed by "?". It is not compatible
649 with Perl. It can also be set by a (?U) option setting within the pattern.
650 <pre>
652 </pre>
653 This option causes PCRE to regard both the pattern and the subject as strings
654 of UTF-8 characters instead of single-byte character strings. However, it is
655 available only when PCRE is built to include UTF-8 support. If not, the use
656 of this option provokes an error. Details of how this option changes the
657 behaviour of PCRE are given in the
658 <a href="pcre.html#utf8support">section on UTF-8 support</a>
659 in the main
660 <a href="pcre.html"><b>pcre</b></a>
661 page.
662 <pre>
664 </pre>
665 When PCRE_UTF8 is set, the validity of the pattern as a UTF-8 string is
666 automatically checked. There is a discussion about the
667 <a href="pcre.html#utf8strings">validity of UTF-8 strings</a>
668 in the main
669 <a href="pcre.html"><b>pcre</b></a>
670 page. If an invalid UTF-8 sequence of bytes is found, <b>pcre_compile()</b>
671 returns an error. If you already know that your pattern is valid, and you want
672 to skip this check for performance reasons, you can set the PCRE_NO_UTF8_CHECK
673 option. When it is set, the effect of passing an invalid UTF-8 string as a
674 pattern is undefined. It may cause your program to crash. Note that this option
675 can also be passed to <b>pcre_exec()</b> and <b>pcre_dfa_exec()</b>, to suppress
676 the UTF-8 validity checking of subject strings.
677 </P>
678 <br><a name="SEC8" href="#TOC1">COMPILATION ERROR CODES</a><br>
679 <P>
680 The following table lists the error codes than may be returned by
681 <b>pcre_compile2()</b>, along with the error messages that may be returned by
682 both compiling functions. As PCRE has developed, some error codes have fallen
683 out of use. To avoid confusion, they have not been re-used.
684 <pre>
685 0 no error
686 1 \ at end of pattern
687 2 \c at end of pattern
688 3 unrecognized character follows \
689 4 numbers out of order in {} quantifier
690 5 number too big in {} quantifier
691 6 missing terminating ] for character class
692 7 invalid escape sequence in character class
693 8 range out of order in character class
694 9 nothing to repeat
695 10 [this code is not in use]
696 11 internal error: unexpected repeat
697 12 unrecognized character after (? or (?-
698 13 POSIX named classes are supported only within a class
699 14 missing )
700 15 reference to non-existent subpattern
701 16 erroffset passed as NULL
702 17 unknown option bit(s) set
703 18 missing ) after comment
704 19 [this code is not in use]
705 20 regular expression is too large
706 21 failed to get memory
707 22 unmatched parentheses
708 23 internal error: code overflow
709 24 unrecognized character after (?&#60;
710 25 lookbehind assertion is not fixed length
711 26 malformed number or name after (?(
712 27 conditional group contains more than two branches
713 28 assertion expected after (?(
714 29 (?R or (?[+-]digits must be followed by )
715 30 unknown POSIX class name
716 31 POSIX collating elements are not supported
717 32 this version of PCRE is not compiled with PCRE_UTF8 support
718 33 [this code is not in use]
719 34 character value in \x{...} sequence is too large
720 35 invalid condition (?(0)
721 36 \C not allowed in lookbehind assertion
722 37 PCRE does not support \L, \l, \N, \U, or \u
723 38 number after (?C is &#62; 255
724 39 closing ) for (?C expected
725 40 recursive call could loop indefinitely
726 41 unrecognized character after (?P
727 42 syntax error in subpattern name (missing terminator)
728 43 two named subpatterns have the same name
729 44 invalid UTF-8 string
730 45 support for \P, \p, and \X has not been compiled
731 46 malformed \P or \p sequence
732 47 unknown property name after \P or \p
733 48 subpattern name is too long (maximum 32 characters)
734 49 too many named subpatterns (maximum 10000)
735 50 [this code is not in use]
736 51 octal value is greater than \377 (not in UTF-8 mode)
737 52 internal error: overran compiling workspace
738 53 internal error: previously-checked referenced subpattern not found
739 54 DEFINE group contains more than one branch
740 55 repeating a DEFINE group is not allowed
741 56 inconsistent NEWLINE options
742 57 \g is not followed by a braced, angle-bracketed, or quoted
743 name/number or by a plain number
744 58 a numbered reference must not be zero
745 59 (*VERB) with an argument is not supported
746 60 (*VERB) not recognized
747 61 number is too big
748 62 subpattern name expected
749 63 digit expected after (?+
750 64 ] is an invalid data character in JavaScript compatibility mode
751 </pre>
752 The numbers 32 and 10000 in errors 48 and 49 are defaults; different values may
753 be used if the limits were changed when PCRE was built.
754 </P>
755 <br><a name="SEC9" href="#TOC1">STUDYING A PATTERN</a><br>
756 <P>
757 <b>pcre_extra *pcre_study(const pcre *<i>code</i>, int <i>options</i></b>
758 <b>const char **<i>errptr</i>);</b>
759 </P>
760 <P>
761 If a compiled pattern is going to be used several times, it is worth spending
762 more time analyzing it in order to speed up the time taken for matching. The
763 function <b>pcre_study()</b> takes a pointer to a compiled pattern as its first
764 argument. If studying the pattern produces additional information that will
765 help speed up matching, <b>pcre_study()</b> returns a pointer to a
766 <b>pcre_extra</b> block, in which the <i>study_data</i> field points to the
767 results of the study.
768 </P>
769 <P>
770 The returned value from <b>pcre_study()</b> can be passed directly to
771 <b>pcre_exec()</b>. However, a <b>pcre_extra</b> block also contains other
772 fields that can be set by the caller before the block is passed; these are
773 described
774 <a href="#extradata">below</a>
775 in the section on matching a pattern.
776 </P>
777 <P>
778 If studying the pattern does not produce any additional information
779 <b>pcre_study()</b> returns NULL. In that circumstance, if the calling program
780 wants to pass any of the other fields to <b>pcre_exec()</b>, it must set up its
781 own <b>pcre_extra</b> block.
782 </P>
783 <P>
784 The second argument of <b>pcre_study()</b> contains option bits. At present, no
785 options are defined, and this argument should always be zero.
786 </P>
787 <P>
788 The third argument for <b>pcre_study()</b> is a pointer for an error message. If
789 studying succeeds (even if no data is returned), the variable it points to is
790 set to NULL. Otherwise it is set to point to a textual error message. This is a
791 static string that is part of the library. You must not try to free it. You
792 should test the error pointer for NULL after calling <b>pcre_study()</b>, to be
793 sure that it has run successfully.
794 </P>
795 <P>
796 This is a typical call to <b>pcre_study</b>():
797 <pre>
798 pcre_extra *pe;
799 pe = pcre_study(
800 re, /* result of pcre_compile() */
801 0, /* no options exist */
802 &error); /* set to NULL or points to a message */
803 </pre>
804 At present, studying a pattern is useful only for non-anchored patterns that do
805 not have a single fixed starting character. A bitmap of possible starting
806 bytes is created.
807 <a name="localesupport"></a></P>
808 <br><a name="SEC10" href="#TOC1">LOCALE SUPPORT</a><br>
809 <P>
810 PCRE handles caseless matching, and determines whether characters are letters,
811 digits, or whatever, by reference to a set of tables, indexed by character
812 value. When running in UTF-8 mode, this applies only to characters with codes
813 less than 128. Higher-valued codes never match escapes such as \w or \d, but
814 can be tested with \p if PCRE is built with Unicode character property
815 support. The use of locales with Unicode is discouraged. If you are handling
816 characters with codes greater than 128, you should either use UTF-8 and
817 Unicode, or use locales, but not try to mix the two.
818 </P>
819 <P>
820 PCRE contains an internal set of tables that are used when the final argument
821 of <b>pcre_compile()</b> is NULL. These are sufficient for many applications.
822 Normally, the internal tables recognize only ASCII characters. However, when
823 PCRE is built, it is possible to cause the internal tables to be rebuilt in the
824 default "C" locale of the local system, which may cause them to be different.
825 </P>
826 <P>
827 The internal tables can always be overridden by tables supplied by the
828 application that calls PCRE. These may be created in a different locale from
829 the default. As more and more applications change to using Unicode, the need
830 for this locale support is expected to die away.
831 </P>
832 <P>
833 External tables are built by calling the <b>pcre_maketables()</b> function,
834 which has no arguments, in the relevant locale. The result can then be passed
835 to <b>pcre_compile()</b> or <b>pcre_exec()</b> as often as necessary. For
836 example, to build and use tables that are appropriate for the French locale
837 (where accented characters with values greater than 128 are treated as letters),
838 the following code could be used:
839 <pre>
840 setlocale(LC_CTYPE, "fr_FR");
841 tables = pcre_maketables();
842 re = pcre_compile(..., tables);
843 </pre>
844 The locale name "fr_FR" is used on Linux and other Unix-like systems; if you
845 are using Windows, the name for the French locale is "french".
846 </P>
847 <P>
848 When <b>pcre_maketables()</b> runs, the tables are built in memory that is
849 obtained via <b>pcre_malloc</b>. It is the caller's responsibility to ensure
850 that the memory containing the tables remains available for as long as it is
851 needed.
852 </P>
853 <P>
854 The pointer that is passed to <b>pcre_compile()</b> is saved with the compiled
855 pattern, and the same tables are used via this pointer by <b>pcre_study()</b>
856 and normally also by <b>pcre_exec()</b>. Thus, by default, for any single
857 pattern, compilation, studying and matching all happen in the same locale, but
858 different patterns can be compiled in different locales.
859 </P>
860 <P>
861 It is possible to pass a table pointer or NULL (indicating the use of the
862 internal tables) to <b>pcre_exec()</b>. Although not intended for this purpose,
863 this facility could be used to match a pattern in a different locale from the
864 one in which it was compiled. Passing table pointers at run time is discussed
865 below in the section on matching a pattern.
866 </P>
867 <br><a name="SEC11" href="#TOC1">INFORMATION ABOUT A PATTERN</a><br>
868 <P>
869 <b>int pcre_fullinfo(const pcre *<i>code</i>, const pcre_extra *<i>extra</i>,</b>
870 <b>int <i>what</i>, void *<i>where</i>);</b>
871 </P>
872 <P>
873 The <b>pcre_fullinfo()</b> function returns information about a compiled
874 pattern. It replaces the obsolete <b>pcre_info()</b> function, which is
875 nevertheless retained for backwards compability (and is documented below).
876 </P>
877 <P>
878 The first argument for <b>pcre_fullinfo()</b> is a pointer to the compiled
879 pattern. The second argument is the result of <b>pcre_study()</b>, or NULL if
880 the pattern was not studied. The third argument specifies which piece of
881 information is required, and the fourth argument is a pointer to a variable
882 to receive the data. The yield of the function is zero for success, or one of
883 the following negative numbers:
884 <pre>
885 PCRE_ERROR_NULL the argument <i>code</i> was NULL
886 the argument <i>where</i> was NULL
887 PCRE_ERROR_BADMAGIC the "magic number" was not found
888 PCRE_ERROR_BADOPTION the value of <i>what</i> was invalid
889 </pre>
890 The "magic number" is placed at the start of each compiled pattern as an simple
891 check against passing an arbitrary memory pointer. Here is a typical call of
892 <b>pcre_fullinfo()</b>, to obtain the length of the compiled pattern:
893 <pre>
894 int rc;
895 size_t length;
896 rc = pcre_fullinfo(
897 re, /* result of pcre_compile() */
898 pe, /* result of pcre_study(), or NULL */
899 PCRE_INFO_SIZE, /* what is required */
900 &length); /* where to put the data */
901 </pre>
902 The possible values for the third argument are defined in <b>pcre.h</b>, and are
903 as follows:
904 <pre>
906 </pre>
907 Return the number of the highest back reference in the pattern. The fourth
908 argument should point to an <b>int</b> variable. Zero is returned if there are
909 no back references.
910 <pre>
912 </pre>
913 Return the number of capturing subpatterns in the pattern. The fourth argument
914 should point to an <b>int</b> variable.
915 <pre>
917 </pre>
918 Return a pointer to the internal default character tables within PCRE. The
919 fourth argument should point to an <b>unsigned char *</b> variable. This
920 information call is provided for internal use by the <b>pcre_study()</b>
921 function. External callers can cause PCRE to use its internal tables by passing
922 a NULL table pointer.
923 <pre>
925 </pre>
926 Return information about the first byte of any matched string, for a
927 non-anchored pattern. The fourth argument should point to an <b>int</b>
928 variable. (This option used to be called PCRE_INFO_FIRSTCHAR; the old name is
929 still recognized for backwards compatibility.)
930 </P>
931 <P>
932 If there is a fixed first byte, for example, from a pattern such as
933 (cat|cow|coyote), its value is returned. Otherwise, if either
934 <br>
935 <br>
936 (a) the pattern was compiled with the PCRE_MULTILINE option, and every branch
937 starts with "^", or
938 <br>
939 <br>
940 (b) every branch of the pattern starts with ".*" and PCRE_DOTALL is not set
941 (if it were set, the pattern would be anchored),
942 <br>
943 <br>
944 -1 is returned, indicating that the pattern matches only at the start of a
945 subject string or after any newline within the string. Otherwise -2 is
946 returned. For anchored patterns, -2 is returned.
947 <pre>
949 </pre>
950 If the pattern was studied, and this resulted in the construction of a 256-bit
951 table indicating a fixed set of bytes for the first byte in any matching
952 string, a pointer to the table is returned. Otherwise NULL is returned. The
953 fourth argument should point to an <b>unsigned char *</b> variable.
954 <pre>
956 </pre>
957 Return 1 if the pattern contains any explicit matches for CR or LF characters,
958 otherwise 0. The fourth argument should point to an <b>int</b> variable. An
959 explicit match is either a literal CR or LF character, or \r or \n.
960 <pre>
962 </pre>
963 Return 1 if the (?J) or (?-J) option setting is used in the pattern, otherwise
964 0. The fourth argument should point to an <b>int</b> variable. (?J) and
965 (?-J) set and unset the local PCRE_DUPNAMES option, respectively.
966 <pre>
968 </pre>
969 Return the value of the rightmost literal byte that must exist in any matched
970 string, other than at its start, if such a byte has been recorded. The fourth
971 argument should point to an <b>int</b> variable. If there is no such byte, -1 is
972 returned. For anchored patterns, a last literal byte is recorded only if it
973 follows something of variable length. For example, for the pattern
974 /^a\d+z\d+/ the returned value is "z", but for /^a\dz\d/ the returned value
975 is -1.
976 <pre>
980 </pre>
981 PCRE supports the use of named as well as numbered capturing parentheses. The
982 names are just an additional way of identifying the parentheses, which still
983 acquire numbers. Several convenience functions such as
984 <b>pcre_get_named_substring()</b> are provided for extracting captured
985 substrings by name. It is also possible to extract the data directly, by first
986 converting the name to a number in order to access the correct pointers in the
987 output vector (described with <b>pcre_exec()</b> below). To do the conversion,
988 you need to use the name-to-number map, which is described by these three
989 values.
990 </P>
991 <P>
992 The map consists of a number of fixed-size entries. PCRE_INFO_NAMECOUNT gives
993 the number of entries, and PCRE_INFO_NAMEENTRYSIZE gives the size of each
994 entry; both of these return an <b>int</b> value. The entry size depends on the
995 length of the longest name. PCRE_INFO_NAMETABLE returns a pointer to the first
996 entry of the table (a pointer to <b>char</b>). The first two bytes of each entry
997 are the number of the capturing parenthesis, most significant byte first. The
998 rest of the entry is the corresponding name, zero terminated. The names are in
999 alphabetical order. When PCRE_DUPNAMES is set, duplicate names are in order of
1000 their parentheses numbers. For example, consider the following pattern (assume
1001 PCRE_EXTENDED is set, so white space - including newlines - is ignored):
1002 <pre>
1003 (?&#60;date&#62; (?&#60;year&#62;(\d\d)?\d\d) - (?&#60;month&#62;\d\d) - (?&#60;day&#62;\d\d) )
1004 </pre>
1005 There are four named subpatterns, so the table has four entries, and each entry
1006 in the table is eight bytes long. The table is as follows, with non-printing
1007 bytes shows in hexadecimal, and undefined bytes shown as ??:
1008 <pre>
1009 00 01 d a t e 00 ??
1010 00 05 d a y 00 ?? ??
1011 00 04 m o n t h 00
1012 00 02 y e a r 00 ??
1013 </pre>
1014 When writing code to extract data from named subpatterns using the
1015 name-to-number map, remember that the length of the entries is likely to be
1016 different for each compiled pattern.
1017 <pre>
1019 </pre>
1020 Return 1 if the pattern can be used for partial matching, otherwise 0. The
1021 fourth argument should point to an <b>int</b> variable. From release 8.00, this
1022 always returns 1, because the restrictions that previously applied to partial
1023 matching have been lifted. The
1024 <a href="pcrepartial.html"><b>pcrepartial</b></a>
1025 documentation gives details of partial matching.
1026 <pre>
1028 </pre>
1029 Return a copy of the options with which the pattern was compiled. The fourth
1030 argument should point to an <b>unsigned long int</b> variable. These option bits
1031 are those specified in the call to <b>pcre_compile()</b>, modified by any
1032 top-level option settings at the start of the pattern itself. In other words,
1033 they are the options that will be in force when matching starts. For example,
1034 if the pattern /(?im)abc(?-i)d/ is compiled with the PCRE_EXTENDED option, the
1036 </P>
1037 <P>
1038 A pattern is automatically anchored by PCRE if all of its top-level
1039 alternatives begin with one of the following:
1040 <pre>
1041 ^ unless PCRE_MULTILINE is set
1042 \A always
1043 \G always
1044 .* if PCRE_DOTALL is set and there are no back references to the subpattern in which .* appears
1045 </pre>
1046 For such patterns, the PCRE_ANCHORED bit is set in the options returned by
1047 <b>pcre_fullinfo()</b>.
1048 <pre>
1050 </pre>
1051 Return the size of the compiled pattern, that is, the value that was passed as
1052 the argument to <b>pcre_malloc()</b> when PCRE was getting memory in which to
1053 place the compiled data. The fourth argument should point to a <b>size_t</b>
1054 variable.
1055 <pre>
1057 </pre>
1058 Return the size of the data block pointed to by the <i>study_data</i> field in
1059 a <b>pcre_extra</b> block. That is, it is the value that was passed to
1060 <b>pcre_malloc()</b> when PCRE was getting memory into which to place the data
1061 created by <b>pcre_study()</b>. The fourth argument should point to a
1062 <b>size_t</b> variable.
1063 </P>
1064 <br><a name="SEC12" href="#TOC1">OBSOLETE INFO FUNCTION</a><br>
1065 <P>
1066 <b>int pcre_info(const pcre *<i>code</i>, int *<i>optptr</i>, int</b>
1067 <b>*<i>firstcharptr</i>);</b>
1068 </P>
1069 <P>
1070 The <b>pcre_info()</b> function is now obsolete because its interface is too
1071 restrictive to return all the available data about a compiled pattern. New
1072 programs should use <b>pcre_fullinfo()</b> instead. The yield of
1073 <b>pcre_info()</b> is the number of capturing subpatterns, or one of the
1074 following negative numbers:
1075 <pre>
1076 PCRE_ERROR_NULL the argument <i>code</i> was NULL
1077 PCRE_ERROR_BADMAGIC the "magic number" was not found
1078 </pre>
1079 If the <i>optptr</i> argument is not NULL, a copy of the options with which the
1080 pattern was compiled is placed in the integer it points to (see
1081 PCRE_INFO_OPTIONS above).
1082 </P>
1083 <P>
1084 If the pattern is not anchored and the <i>firstcharptr</i> argument is not NULL,
1085 it is used to pass back information about the first character of any matched
1086 string (see PCRE_INFO_FIRSTBYTE above).
1087 </P>
1088 <br><a name="SEC13" href="#TOC1">REFERENCE COUNTS</a><br>
1089 <P>
1090 <b>int pcre_refcount(pcre *<i>code</i>, int <i>adjust</i>);</b>
1091 </P>
1092 <P>
1093 The <b>pcre_refcount()</b> function is used to maintain a reference count in the
1094 data block that contains a compiled pattern. It is provided for the benefit of
1095 applications that operate in an object-oriented manner, where different parts
1096 of the application may be using the same compiled pattern, but you want to free
1097 the block when they are all done.
1098 </P>
1099 <P>
1100 When a pattern is compiled, the reference count field is initialized to zero.
1101 It is changed only by calling this function, whose action is to add the
1102 <i>adjust</i> value (which may be positive or negative) to it. The yield of the
1103 function is the new value. However, the value of the count is constrained to
1104 lie between 0 and 65535, inclusive. If the new value is outside these limits,
1105 it is forced to the appropriate limit value.
1106 </P>
1107 <P>
1108 Except when it is zero, the reference count is not correctly preserved if a
1109 pattern is compiled on one host and then transferred to a host whose byte-order
1110 is different. (This seems a highly unlikely scenario.)
1111 </P>
1112 <br><a name="SEC14" href="#TOC1">MATCHING A PATTERN: THE TRADITIONAL FUNCTION</a><br>
1113 <P>
1114 <b>int pcre_exec(const pcre *<i>code</i>, const pcre_extra *<i>extra</i>,</b>
1115 <b>const char *<i>subject</i>, int <i>length</i>, int <i>startoffset</i>,</b>
1116 <b>int <i>options</i>, int *<i>ovector</i>, int <i>ovecsize</i>);</b>
1117 </P>
1118 <P>
1119 The function <b>pcre_exec()</b> is called to match a subject string against a
1120 compiled pattern, which is passed in the <i>code</i> argument. If the
1121 pattern has been studied, the result of the study should be passed in the
1122 <i>extra</i> argument. This function is the main matching facility of the
1123 library, and it operates in a Perl-like manner. For specialist use there is
1124 also an alternative matching function, which is described
1125 <a href="#dfamatch">below</a>
1126 in the section about the <b>pcre_dfa_exec()</b> function.
1127 </P>
1128 <P>
1129 In most applications, the pattern will have been compiled (and optionally
1130 studied) in the same process that calls <b>pcre_exec()</b>. However, it is
1131 possible to save compiled patterns and study data, and then use them later
1132 in different processes, possibly even on different hosts. For a discussion
1133 about this, see the
1134 <a href="pcreprecompile.html"><b>pcreprecompile</b></a>
1135 documentation.
1136 </P>
1137 <P>
1138 Here is an example of a simple call to <b>pcre_exec()</b>:
1139 <pre>
1140 int rc;
1141 int ovector[30];
1142 rc = pcre_exec(
1143 re, /* result of pcre_compile() */
1144 NULL, /* we didn't study the pattern */
1145 "some string", /* the subject string */
1146 11, /* the length of the subject string */
1147 0, /* start at offset 0 in the subject */
1148 0, /* default options */
1149 ovector, /* vector of integers for substring information */
1150 30); /* number of elements (NOT size in bytes) */
1151 <a name="extradata"></a></PRE>
1152 </P>
1153 <br><b>
1154 Extra data for <b>pcre_exec()</b>
1155 </b><br>
1156 <P>
1157 If the <i>extra</i> argument is not NULL, it must point to a <b>pcre_extra</b>
1158 data block. The <b>pcre_study()</b> function returns such a block (when it
1159 doesn't return NULL), but you can also create one for yourself, and pass
1160 additional information in it. The <b>pcre_extra</b> block contains the following
1161 fields (not necessarily in this order):
1162 <pre>
1163 unsigned long int <i>flags</i>;
1164 void *<i>study_data</i>;
1165 unsigned long int <i>match_limit</i>;
1166 unsigned long int <i>match_limit_recursion</i>;
1167 void *<i>callout_data</i>;
1168 const unsigned char *<i>tables</i>;
1169 </pre>
1170 The <i>flags</i> field is a bitmap that specifies which of the other fields
1171 are set. The flag bits are:
1172 <pre>
1178 </pre>
1179 Other flag bits should be set to zero. The <i>study_data</i> field is set in the
1180 <b>pcre_extra</b> block that is returned by <b>pcre_study()</b>, together with
1181 the appropriate flag bit. You should not set this yourself, but you may add to
1182 the block by setting the other fields and their corresponding flag bits.
1183 </P>
1184 <P>
1185 The <i>match_limit</i> field provides a means of preventing PCRE from using up a
1186 vast amount of resources when running patterns that are not going to match,
1187 but which have a very large number of possibilities in their search trees. The
1188 classic example is the use of nested unlimited repeats.
1189 </P>
1190 <P>
1191 Internally, PCRE uses a function called <b>match()</b> which it calls repeatedly
1192 (sometimes recursively). The limit set by <i>match_limit</i> is imposed on the
1193 number of times this function is called during a match, which has the effect of
1194 limiting the amount of backtracking that can take place. For patterns that are
1195 not anchored, the count restarts from zero for each position in the subject
1196 string.
1197 </P>
1198 <P>
1199 The default value for the limit can be set when PCRE is built; the default
1200 default is 10 million, which handles all but the most extreme cases. You can
1201 override the default by suppling <b>pcre_exec()</b> with a <b>pcre_extra</b>
1202 block in which <i>match_limit</i> is set, and PCRE_EXTRA_MATCH_LIMIT is set in
1203 the <i>flags</i> field. If the limit is exceeded, <b>pcre_exec()</b> returns
1205 </P>
1206 <P>
1207 The <i>match_limit_recursion</i> field is similar to <i>match_limit</i>, but
1208 instead of limiting the total number of times that <b>match()</b> is called, it
1209 limits the depth of recursion. The recursion depth is a smaller number than the
1210 total number of calls, because not all calls to <b>match()</b> are recursive.
1211 This limit is of use only if it is set smaller than <i>match_limit</i>.
1212 </P>
1213 <P>
1214 Limiting the recursion depth limits the amount of stack that can be used, or,
1215 when PCRE has been compiled to use memory on the heap instead of the stack, the
1216 amount of heap memory that can be used.
1217 </P>
1218 <P>
1219 The default value for <i>match_limit_recursion</i> can be set when PCRE is
1220 built; the default default is the same value as the default for
1221 <i>match_limit</i>. You can override the default by suppling <b>pcre_exec()</b>
1222 with a <b>pcre_extra</b> block in which <i>match_limit_recursion</i> is set, and
1223 PCRE_EXTRA_MATCH_LIMIT_RECURSION is set in the <i>flags</i> field. If the limit
1224 is exceeded, <b>pcre_exec()</b> returns PCRE_ERROR_RECURSIONLIMIT.
1225 </P>
1226 <P>
1227 The <i>pcre_callout</i> field is used in conjunction with the "callout" feature,
1228 which is described in the
1229 <a href="pcrecallout.html"><b>pcrecallout</b></a>
1230 documentation.
1231 </P>
1232 <P>
1233 The <i>tables</i> field is used to pass a character tables pointer to
1234 <b>pcre_exec()</b>; this overrides the value that is stored with the compiled
1235 pattern. A non-NULL value is stored with the compiled pattern only if custom
1236 tables were supplied to <b>pcre_compile()</b> via its <i>tableptr</i> argument.
1237 If NULL is passed to <b>pcre_exec()</b> using this mechanism, it forces PCRE's
1238 internal tables to be used. This facility is helpful when re-using patterns
1239 that have been saved after compiling with an external set of tables, because
1240 the external tables might be at a different address when <b>pcre_exec()</b> is
1241 called. See the
1242 <a href="pcreprecompile.html"><b>pcreprecompile</b></a>
1243 documentation for a discussion of saving compiled patterns for later use.
1244 <a name="execoptions"></a></P>
1245 <br><b>
1246 Option bits for <b>pcre_exec()</b>
1247 </b><br>
1248 <P>
1249 The unused bits of the <i>options</i> argument for <b>pcre_exec()</b> must be
1250 zero. The only bits that may be set are PCRE_ANCHORED, PCRE_NEWLINE_<i>xxx</i>,
1253 <pre>
1255 </pre>
1256 The PCRE_ANCHORED option limits <b>pcre_exec()</b> to matching at the first
1257 matching position. If a pattern was compiled with PCRE_ANCHORED, or turned out
1258 to be anchored by virtue of its contents, it cannot be made unachored at
1259 matching time.
1260 <pre>
1263 </pre>
1264 These options (which are mutually exclusive) control what the \R escape
1265 sequence matches. The choice is either to match only CR, LF, or CRLF, or to
1266 match any Unicode newline sequence. These options override the choice that was
1267 made or defaulted when the pattern was compiled.
1268 <pre>
1274 </pre>
1275 These options override the newline definition that was chosen or defaulted when
1276 the pattern was compiled. For details, see the description of
1277 <b>pcre_compile()</b> above. During matching, the newline choice affects the
1278 behaviour of the dot, circumflex, and dollar metacharacters. It may also alter
1279 the way the match position is advanced after a match failure for an unanchored
1280 pattern.
1281 </P>
1282 <P>
1284 match attempt for an unanchored pattern fails when the current position is at a
1285 CRLF sequence, and the pattern contains no explicit matches for CR or LF
1286 characters, the match position is advanced by two characters instead of one, in
1287 other words, to after the CRLF.
1288 </P>
1289 <P>
1290 The above rule is a compromise that makes the most common cases work as
1291 expected. For example, if the pattern is .+A (and the PCRE_DOTALL option is not
1292 set), it does not match the string "\r\nA" because, after failing at the
1293 start, it skips both the CR and the LF before retrying. However, the pattern
1294 [\r\n]A does match that string, because it contains an explicit CR or LF
1295 reference, and so advances only by one character after the first failure.
1296 </P>
1297 <P>
1298 An explicit match for CR of LF is either a literal appearance of one of those
1299 characters, or one of the \r or \n escape sequences. Implicit matches such as
1300 [^X] do not count, nor does \s (which includes CR and LF in the characters
1301 that it matches).
1302 </P>
1303 <P>
1304 Notwithstanding the above, anomalous effects may still occur when CRLF is a
1305 valid newline sequence and explicit \r or \n escapes appear in the pattern.
1306 <pre>
1308 </pre>
1309 This option specifies that first character of the subject string is not the
1310 beginning of a line, so the circumflex metacharacter should not match before
1311 it. Setting this without PCRE_MULTILINE (at compile time) causes circumflex
1312 never to match. This option affects only the behaviour of the circumflex
1313 metacharacter. It does not affect \A.
1314 <pre>
1316 </pre>
1317 This option specifies that the end of the subject string is not the end of a
1318 line, so the dollar metacharacter should not match it nor (except in multiline
1319 mode) a newline immediately before it. Setting this without PCRE_MULTILINE (at
1320 compile time) causes dollar never to match. This option affects only the
1321 behaviour of the dollar metacharacter. It does not affect \Z or \z.
1322 <pre>
1324 </pre>
1325 An empty string is not considered to be a valid match if this option is set. If
1326 there are alternatives in the pattern, they are tried. If all the alternatives
1327 match the empty string, the entire match fails. For example, if the pattern
1328 <pre>
1329 a?b?
1330 </pre>
1331 is applied to a string not beginning with "a" or "b", it matches the empty
1332 string at the start of the subject. With PCRE_NOTEMPTY set, this match is not
1333 valid, so PCRE searches further into the string for occurrences of "a" or "b".
1334 </P>
1335 <P>
1336 Perl has no direct equivalent of PCRE_NOTEMPTY, but it does make a special case
1337 of a pattern match of the empty string within its <b>split()</b> function, and
1338 when using the /g modifier. It is possible to emulate Perl's behaviour after
1339 matching a null string by first trying the match again at the same offset with
1340 PCRE_NOTEMPTY and PCRE_ANCHORED, and then if that fails by advancing the
1341 starting offset (see below) and trying an ordinary match again. There is some
1342 code that demonstrates how to do this in the
1343 <a href="pcredemo.html"><b>pcredemo</b></a>
1344 sample program.
1345 <pre>
1347 </pre>
1348 There are a number of optimizations that <b>pcre_exec()</b> uses at the start of
1349 a match, in order to speed up the process. For example, if it is known that a
1350 match must start with a specific character, it searches the subject for that
1351 character, and fails immediately if it cannot find it, without actually running
1352 the main matching function. When callouts are in use, these optimizations can
1353 cause them to be skipped. This option disables the "start-up" optimizations,
1354 causing performance to suffer, but ensuring that the callouts do occur.
1355 <pre>
1357 </pre>
1358 When PCRE_UTF8 is set at compile time, the validity of the subject as a UTF-8
1359 string is automatically checked when <b>pcre_exec()</b> is subsequently called.
1360 The value of <i>startoffset</i> is also checked to ensure that it points to the
1361 start of a UTF-8 character. There is a discussion about the validity of UTF-8
1362 strings in the
1363 <a href="pcre.html#utf8strings">section on UTF-8 support</a>
1364 in the main
1365 <a href="pcre.html"><b>pcre</b></a>
1366 page. If an invalid UTF-8 sequence of bytes is found, <b>pcre_exec()</b> returns
1367 the error PCRE_ERROR_BADUTF8. If <i>startoffset</i> contains an invalid value,
1368 PCRE_ERROR_BADUTF8_OFFSET is returned.
1369 </P>
1370 <P>
1371 If you already know that your subject is valid, and you want to skip these
1372 checks for performance reasons, you can set the PCRE_NO_UTF8_CHECK option when
1373 calling <b>pcre_exec()</b>. You might want to do this for the second and
1374 subsequent calls to <b>pcre_exec()</b> if you are making repeated calls to find
1375 all the matches in a single subject string. However, you should be sure that
1376 the value of <i>startoffset</i> points to the start of a UTF-8 character. When
1377 PCRE_NO_UTF8_CHECK is set, the effect of passing an invalid UTF-8 string as a
1378 subject, or a value of <i>startoffset</i> that does not point to the start of a
1379 UTF-8 character, is undefined. Your program may crash.
1380 <pre>
1383 </pre>
1384 These options turn on the partial matching feature. For backwards
1385 compatibility, PCRE_PARTIAL is a synonym for PCRE_PARTIAL_SOFT. A partial match
1386 occurs if the end of the subject string is reached successfully, but there are
1387 not enough subject characters to complete the match. If this happens when
1388 PCRE_PARTIAL_HARD is set, <b>pcre_exec()</b> immediately returns
1389 PCRE_ERROR_PARTIAL. Otherwise, if PCRE_PARTIAL_SOFT is set, matching continues
1390 by testing any other alternatives. Only if they all fail is PCRE_ERROR_PARTIAL
1391 returned (instead of PCRE_ERROR_NOMATCH). The portion of the string that
1392 provided the partial match is set as the first matching string. There is a more
1393 detailed discussion in the
1394 <a href="pcrepartial.html"><b>pcrepartial</b></a>
1395 documentation.
1396 </P>
1397 <br><b>
1398 The string to be matched by <b>pcre_exec()</b>
1399 </b><br>
1400 <P>
1401 The subject string is passed to <b>pcre_exec()</b> as a pointer in
1402 <i>subject</i>, a length (in bytes) in <i>length</i>, and a starting byte offset
1403 in <i>startoffset</i>. In UTF-8 mode, the byte offset must point to the start of
1404 a UTF-8 character. Unlike the pattern string, the subject may contain binary
1405 zero bytes. When the starting offset is zero, the search for a match starts at
1406 the beginning of the subject, and this is by far the most common case.
1407 </P>
1408 <P>
1409 A non-zero starting offset is useful when searching for another match in the
1410 same subject by calling <b>pcre_exec()</b> again after a previous success.
1411 Setting <i>startoffset</i> differs from just passing over a shortened string and
1412 setting PCRE_NOTBOL in the case of a pattern that begins with any kind of
1413 lookbehind. For example, consider the pattern
1414 <pre>
1415 \Biss\B
1416 </pre>
1417 which finds occurrences of "iss" in the middle of words. (\B matches only if
1418 the current position in the subject is not a word boundary.) When applied to
1419 the string "Mississipi" the first call to <b>pcre_exec()</b> finds the first
1420 occurrence. If <b>pcre_exec()</b> is called again with just the remainder of the
1421 subject, namely "issipi", it does not match, because \B is always false at the
1422 start of the subject, which is deemed to be a word boundary. However, if
1423 <b>pcre_exec()</b> is passed the entire string again, but with <i>startoffset</i>
1424 set to 4, it finds the second occurrence of "iss" because it is able to look
1425 behind the starting point to discover that it is preceded by a letter.
1426 </P>
1427 <P>
1428 If a non-zero starting offset is passed when the pattern is anchored, one
1429 attempt to match at the given offset is made. This can only succeed if the
1430 pattern does not require the match to be at the start of the subject.
1431 </P>
1432 <br><b>
1433 How <b>pcre_exec()</b> returns captured substrings
1434 </b><br>
1435 <P>
1436 In general, a pattern matches a certain portion of the subject, and in
1437 addition, further substrings from the subject may be picked out by parts of the
1438 pattern. Following the usage in Jeffrey Friedl's book, this is called
1439 "capturing" in what follows, and the phrase "capturing subpattern" is used for
1440 a fragment of a pattern that picks out a substring. PCRE supports several other
1441 kinds of parenthesized subpattern that do not cause substrings to be captured.
1442 </P>
1443 <P>
1444 Captured substrings are returned to the caller via a vector of integers whose
1445 address is passed in <i>ovector</i>. The number of elements in the vector is
1446 passed in <i>ovecsize</i>, which must be a non-negative number. <b>Note</b>: this
1447 argument is NOT the size of <i>ovector</i> in bytes.
1448 </P>
1449 <P>
1450 The first two-thirds of the vector is used to pass back captured substrings,
1451 each substring using a pair of integers. The remaining third of the vector is
1452 used as workspace by <b>pcre_exec()</b> while matching capturing subpatterns,
1453 and is not available for passing back information. The number passed in
1454 <i>ovecsize</i> should always be a multiple of three. If it is not, it is
1455 rounded down.
1456 </P>
1457 <P>
1458 When a match is successful, information about captured substrings is returned
1459 in pairs of integers, starting at the beginning of <i>ovector</i>, and
1460 continuing up to two-thirds of its length at the most. The first element of
1461 each pair is set to the byte offset of the first character in a substring, and
1462 the second is set to the byte offset of the first character after the end of a
1463 substring. <b>Note</b>: these values are always byte offsets, even in UTF-8
1464 mode. They are not character counts.
1465 </P>
1466 <P>
1467 The first pair of integers, <i>ovector[0]</i> and <i>ovector[1]</i>, identify the
1468 portion of the subject string matched by the entire pattern. The next pair is
1469 used for the first capturing subpattern, and so on. The value returned by
1470 <b>pcre_exec()</b> is one more than the highest numbered pair that has been set.
1471 For example, if two substrings have been captured, the returned value is 3. If
1472 there are no capturing subpatterns, the return value from a successful match is
1473 1, indicating that just the first pair of offsets has been set.
1474 </P>
1475 <P>
1476 If a capturing subpattern is matched repeatedly, it is the last portion of the
1477 string that it matched that is returned.
1478 </P>
1479 <P>
1480 If the vector is too small to hold all the captured substring offsets, it is
1481 used as far as possible (up to two-thirds of its length), and the function
1482 returns a value of zero. If the substring offsets are not of interest,
1483 <b>pcre_exec()</b> may be called with <i>ovector</i> passed as NULL and
1484 <i>ovecsize</i> as zero. However, if the pattern contains back references and
1485 the <i>ovector</i> is not big enough to remember the related substrings, PCRE
1486 has to get additional memory for use during matching. Thus it is usually
1487 advisable to supply an <i>ovector</i>.
1488 </P>
1489 <P>
1490 The <b>pcre_info()</b> function can be used to find out how many capturing
1491 subpatterns there are in a compiled pattern. The smallest size for
1492 <i>ovector</i> that will allow for <i>n</i> captured substrings, in addition to
1493 the offsets of the substring matched by the whole pattern, is (<i>n</i>+1)*3.
1494 </P>
1495 <P>
1496 It is possible for capturing subpattern number <i>n+1</i> to match some part of
1497 the subject when subpattern <i>n</i> has not been used at all. For example, if
1498 the string "abc" is matched against the pattern (a|(z))(bc) the return from the
1499 function is 4, and subpatterns 1 and 3 are matched, but 2 is not. When this
1500 happens, both values in the offset pairs corresponding to unused subpatterns
1501 are set to -1.
1502 </P>
1503 <P>
1504 Offset values that correspond to unused subpatterns at the end of the
1505 expression are also set to -1. For example, if the string "abc" is matched
1506 against the pattern (abc)(x(yz)?)? subpatterns 2 and 3 are not matched. The
1507 return from the function is 2, because the highest used capturing subpattern
1508 number is 1. However, you can refer to the offsets for the second and third
1509 capturing subpatterns if you wish (assuming the vector is large enough, of
1510 course).
1511 </P>
1512 <P>
1513 Some convenience functions are provided for extracting the captured substrings
1514 as separate strings. These are described below.
1515 <a name="errorlist"></a></P>
1516 <br><b>
1517 Error return values from <b>pcre_exec()</b>
1518 </b><br>
1519 <P>
1520 If <b>pcre_exec()</b> fails, it returns a negative number. The following are
1521 defined in the header file:
1522 <pre>
1524 </pre>
1525 The subject string did not match the pattern.
1526 <pre>
1528 </pre>
1529 Either <i>code</i> or <i>subject</i> was passed as NULL, or <i>ovector</i> was
1530 NULL and <i>ovecsize</i> was not zero.
1531 <pre>
1533 </pre>
1534 An unrecognized bit was set in the <i>options</i> argument.
1535 <pre>
1537 </pre>
1538 PCRE stores a 4-byte "magic number" at the start of the compiled code, to catch
1539 the case when it is passed a junk pointer and to detect when a pattern that was
1540 compiled in an environment of one endianness is run in an environment with the
1541 other endianness. This is the error that PCRE gives when the magic number is
1542 not present.
1543 <pre>
1545 </pre>
1546 While running the pattern match, an unknown item was encountered in the
1547 compiled pattern. This error could be caused by a bug in PCRE or by overwriting
1548 of the compiled pattern.
1549 <pre>
1551 </pre>
1552 If a pattern contains back references, but the <i>ovector</i> that is passed to
1553 <b>pcre_exec()</b> is not big enough to remember the referenced substrings, PCRE
1554 gets a block of memory at the start of matching to use for this purpose. If the
1555 call via <b>pcre_malloc()</b> fails, this error is given. The memory is
1556 automatically freed at the end of matching.
1557 <pre>
1559 </pre>
1560 This error is used by the <b>pcre_copy_substring()</b>,
1561 <b>pcre_get_substring()</b>, and <b>pcre_get_substring_list()</b> functions (see
1562 below). It is never returned by <b>pcre_exec()</b>.
1563 <pre>
1565 </pre>
1566 The backtracking limit, as specified by the <i>match_limit</i> field in a
1567 <b>pcre_extra</b> structure (or defaulted) was reached. See the description
1568 above.
1569 <pre>
1571 </pre>
1572 This error is never generated by <b>pcre_exec()</b> itself. It is provided for
1573 use by callout functions that want to yield a distinctive error code. See the
1574 <a href="pcrecallout.html"><b>pcrecallout</b></a>
1575 documentation for details.
1576 <pre>
1578 </pre>
1579 A string that contains an invalid UTF-8 byte sequence was passed as a subject.
1580 <pre>
1582 </pre>
1583 The UTF-8 byte sequence that was passed as a subject was valid, but the value
1584 of <i>startoffset</i> did not point to the beginning of a UTF-8 character.
1585 <pre>
1587 </pre>
1588 The subject string did not match, but it did match partially. See the
1589 <a href="pcrepartial.html"><b>pcrepartial</b></a>
1590 documentation for details of partial matching.
1591 <pre>
1593 </pre>
1594 This code is no longer in use. It was formerly returned when the PCRE_PARTIAL
1595 option was used with a compiled pattern containing items that were not
1596 supported for partial matching. From release 8.00 onwards, there are no
1597 restrictions on partial matching.
1598 <pre>
1600 </pre>
1601 An unexpected internal error has occurred. This error could be caused by a bug
1602 in PCRE or by overwriting of the compiled pattern.
1603 <pre>
1605 </pre>
1606 This error is given if the value of the <i>ovecsize</i> argument is negative.
1607 <pre>
1609 </pre>
1610 The internal recursion limit, as specified by the <i>match_limit_recursion</i>
1611 field in a <b>pcre_extra</b> structure (or defaulted) was reached. See the
1612 description above.
1613 <pre>
1615 </pre>
1616 An invalid combination of PCRE_NEWLINE_<i>xxx</i> options was given.
1617 </P>
1618 <P>
1619 Error numbers -16 to -20 and -22 are not used by <b>pcre_exec()</b>.
1620 </P>
1621 <br><a name="SEC15" href="#TOC1">EXTRACTING CAPTURED SUBSTRINGS BY NUMBER</a><br>
1622 <P>
1623 <b>int pcre_copy_substring(const char *<i>subject</i>, int *<i>ovector</i>,</b>
1624 <b>int <i>stringcount</i>, int <i>stringnumber</i>, char *<i>buffer</i>,</b>
1625 <b>int <i>buffersize</i>);</b>
1626 </P>
1627 <P>
1628 <b>int pcre_get_substring(const char *<i>subject</i>, int *<i>ovector</i>,</b>
1629 <b>int <i>stringcount</i>, int <i>stringnumber</i>,</b>
1630 <b>const char **<i>stringptr</i>);</b>
1631 </P>
1632 <P>
1633 <b>int pcre_get_substring_list(const char *<i>subject</i>,</b>
1634 <b>int *<i>ovector</i>, int <i>stringcount</i>, const char ***<i>listptr</i>);</b>
1635 </P>
1636 <P>
1637 Captured substrings can be accessed directly by using the offsets returned by
1638 <b>pcre_exec()</b> in <i>ovector</i>. For convenience, the functions
1639 <b>pcre_copy_substring()</b>, <b>pcre_get_substring()</b>, and
1640 <b>pcre_get_substring_list()</b> are provided for extracting captured substrings
1641 as new, separate, zero-terminated strings. These functions identify substrings
1642 by number. The next section describes functions for extracting named
1643 substrings.
1644 </P>
1645 <P>
1646 A substring that contains a binary zero is correctly extracted and has a
1647 further zero added on the end, but the result is not, of course, a C string.
1648 However, you can process such a string by referring to the length that is
1649 returned by <b>pcre_copy_substring()</b> and <b>pcre_get_substring()</b>.
1650 Unfortunately, the interface to <b>pcre_get_substring_list()</b> is not adequate
1651 for handling strings containing binary zeros, because the end of the final
1652 string is not independently indicated.
1653 </P>
1654 <P>
1655 The first three arguments are the same for all three of these functions:
1656 <i>subject</i> is the subject string that has just been successfully matched,
1657 <i>ovector</i> is a pointer to the vector of integer offsets that was passed to
1658 <b>pcre_exec()</b>, and <i>stringcount</i> is the number of substrings that were
1659 captured by the match, including the substring that matched the entire regular
1660 expression. This is the value returned by <b>pcre_exec()</b> if it is greater
1661 than zero. If <b>pcre_exec()</b> returned zero, indicating that it ran out of
1662 space in <i>ovector</i>, the value passed as <i>stringcount</i> should be the
1663 number of elements in the vector divided by three.
1664 </P>
1665 <P>
1666 The functions <b>pcre_copy_substring()</b> and <b>pcre_get_substring()</b>
1667 extract a single substring, whose number is given as <i>stringnumber</i>. A
1668 value of zero extracts the substring that matched the entire pattern, whereas
1669 higher values extract the captured substrings. For <b>pcre_copy_substring()</b>,
1670 the string is placed in <i>buffer</i>, whose length is given by
1671 <i>buffersize</i>, while for <b>pcre_get_substring()</b> a new block of memory is
1672 obtained via <b>pcre_malloc</b>, and its address is returned via
1673 <i>stringptr</i>. The yield of the function is the length of the string, not
1674 including the terminating zero, or one of these error codes:
1675 <pre>
1677 </pre>
1678 The buffer was too small for <b>pcre_copy_substring()</b>, or the attempt to get
1679 memory failed for <b>pcre_get_substring()</b>.
1680 <pre>
1682 </pre>
1683 There is no substring whose number is <i>stringnumber</i>.
1684 </P>
1685 <P>
1686 The <b>pcre_get_substring_list()</b> function extracts all available substrings
1687 and builds a list of pointers to them. All this is done in a single block of
1688 memory that is obtained via <b>pcre_malloc</b>. The address of the memory block
1689 is returned via <i>listptr</i>, which is also the start of the list of string
1690 pointers. The end of the list is marked by a NULL pointer. The yield of the
1691 function is zero if all went well, or the error code
1692 <pre>
1694 </pre>
1695 if the attempt to get the memory block failed.
1696 </P>
1697 <P>
1698 When any of these functions encounter a substring that is unset, which can
1699 happen when capturing subpattern number <i>n+1</i> matches some part of the
1700 subject, but subpattern <i>n</i> has not been used at all, they return an empty
1701 string. This can be distinguished from a genuine zero-length substring by
1702 inspecting the appropriate offset in <i>ovector</i>, which is negative for unset
1703 substrings.
1704 </P>
1705 <P>
1706 The two convenience functions <b>pcre_free_substring()</b> and
1707 <b>pcre_free_substring_list()</b> can be used to free the memory returned by
1708 a previous call of <b>pcre_get_substring()</b> or
1709 <b>pcre_get_substring_list()</b>, respectively. They do nothing more than call
1710 the function pointed to by <b>pcre_free</b>, which of course could be called
1711 directly from a C program. However, PCRE is used in some situations where it is
1712 linked via a special interface to another programming language that cannot use
1713 <b>pcre_free</b> directly; it is for these cases that the functions are
1714 provided.
1715 </P>
1716 <br><a name="SEC16" href="#TOC1">EXTRACTING CAPTURED SUBSTRINGS BY NAME</a><br>
1717 <P>
1718 <b>int pcre_get_stringnumber(const pcre *<i>code</i>,</b>
1719 <b>const char *<i>name</i>);</b>
1720 </P>
1721 <P>
1722 <b>int pcre_copy_named_substring(const pcre *<i>code</i>,</b>
1723 <b>const char *<i>subject</i>, int *<i>ovector</i>,</b>
1724 <b>int <i>stringcount</i>, const char *<i>stringname</i>,</b>
1725 <b>char *<i>buffer</i>, int <i>buffersize</i>);</b>
1726 </P>
1727 <P>
1728 <b>int pcre_get_named_substring(const pcre *<i>code</i>,</b>
1729 <b>const char *<i>subject</i>, int *<i>ovector</i>,</b>
1730 <b>int <i>stringcount</i>, const char *<i>stringname</i>,</b>
1731 <b>const char **<i>stringptr</i>);</b>
1732 </P>
1733 <P>
1734 To extract a substring by name, you first have to find associated number.
1735 For example, for this pattern
1736 <pre>
1737 (a+)b(?&#60;xxx&#62;\d+)...
1738 </pre>
1739 the number of the subpattern called "xxx" is 2. If the name is known to be
1740 unique (PCRE_DUPNAMES was not set), you can find the number from the name by
1741 calling <b>pcre_get_stringnumber()</b>. The first argument is the compiled
1742 pattern, and the second is the name. The yield of the function is the
1743 subpattern number, or PCRE_ERROR_NOSUBSTRING (-7) if there is no subpattern of
1744 that name.
1745 </P>
1746 <P>
1747 Given the number, you can extract the substring directly, or use one of the
1748 functions described in the previous section. For convenience, there are also
1749 two functions that do the whole job.
1750 </P>
1751 <P>
1752 Most of the arguments of <b>pcre_copy_named_substring()</b> and
1753 <b>pcre_get_named_substring()</b> are the same as those for the similarly named
1754 functions that extract by number. As these are described in the previous
1755 section, they are not re-described here. There are just two differences:
1756 </P>
1757 <P>
1758 First, instead of a substring number, a substring name is given. Second, there
1759 is an extra argument, given at the start, which is a pointer to the compiled
1760 pattern. This is needed in order to gain access to the name-to-number
1761 translation table.
1762 </P>
1763 <P>
1764 These functions call <b>pcre_get_stringnumber()</b>, and if it succeeds, they
1765 then call <b>pcre_copy_substring()</b> or <b>pcre_get_substring()</b>, as
1766 appropriate. <b>NOTE:</b> If PCRE_DUPNAMES is set and there are duplicate names,
1767 the behaviour may not be what you want (see the next section).
1768 </P>
1769 <P>
1770 <b>Warning:</b> If the pattern uses the "(?|" feature to set up multiple
1771 subpatterns with the same number, you cannot use names to distinguish them,
1772 because names are not included in the compiled code. The matching process uses
1773 only numbers.
1774 </P>
1775 <br><a name="SEC17" href="#TOC1">DUPLICATE SUBPATTERN NAMES</a><br>
1776 <P>
1777 <b>int pcre_get_stringtable_entries(const pcre *<i>code</i>,</b>
1778 <b>const char *<i>name</i>, char **<i>first</i>, char **<i>last</i>);</b>
1779 </P>
1780 <P>
1781 When a pattern is compiled with the PCRE_DUPNAMES option, names for subpatterns
1782 are not required to be unique. Normally, patterns with duplicate names are such
1783 that in any one match, only one of the named subpatterns participates. An
1784 example is shown in the
1785 <a href="pcrepattern.html"><b>pcrepattern</b></a>
1786 documentation.
1787 </P>
1788 <P>
1789 When duplicates are present, <b>pcre_copy_named_substring()</b> and
1790 <b>pcre_get_named_substring()</b> return the first substring corresponding to
1791 the given name that is set. If none are set, PCRE_ERROR_NOSUBSTRING (-7) is
1792 returned; no data is returned. The <b>pcre_get_stringnumber()</b> function
1793 returns one of the numbers that are associated with the name, but it is not
1794 defined which it is.
1795 </P>
1796 <P>
1797 If you want to get full details of all captured substrings for a given name,
1798 you must use the <b>pcre_get_stringtable_entries()</b> function. The first
1799 argument is the compiled pattern, and the second is the name. The third and
1800 fourth are pointers to variables which are updated by the function. After it
1801 has run, they point to the first and last entries in the name-to-number table
1802 for the given name. The function itself returns the length of each entry, or
1803 PCRE_ERROR_NOSUBSTRING (-7) if there are none. The format of the table is
1804 described above in the section entitled <i>Information about a pattern</i>.
1805 Given all the relevant entries for the name, you can extract each of their
1806 numbers, and hence the captured data, if any.
1807 </P>
1808 <br><a name="SEC18" href="#TOC1">FINDING ALL POSSIBLE MATCHES</a><br>
1809 <P>
1810 The traditional matching function uses a similar algorithm to Perl, which stops
1811 when it finds the first match, starting at a given point in the subject. If you
1812 want to find all possible matches, or the longest possible match, consider
1813 using the alternative matching function (see below) instead. If you cannot use
1814 the alternative function, but still need to find all possible matches, you
1815 can kludge it up by making use of the callout facility, which is described in
1816 the
1817 <a href="pcrecallout.html"><b>pcrecallout</b></a>
1818 documentation.
1819 </P>
1820 <P>
1821 What you have to do is to insert a callout right at the end of the pattern.
1822 When your callout function is called, extract and save the current matched
1823 substring. Then return 1, which forces <b>pcre_exec()</b> to backtrack and try
1824 other alternatives. Ultimately, when it runs out of matches, <b>pcre_exec()</b>
1825 will yield PCRE_ERROR_NOMATCH.
1826 <a name="dfamatch"></a></P>
1827 <br><a name="SEC19" href="#TOC1">MATCHING A PATTERN: THE ALTERNATIVE FUNCTION</a><br>
1828 <P>
1829 <b>int pcre_dfa_exec(const pcre *<i>code</i>, const pcre_extra *<i>extra</i>,</b>
1830 <b>const char *<i>subject</i>, int <i>length</i>, int <i>startoffset</i>,</b>
1831 <b>int <i>options</i>, int *<i>ovector</i>, int <i>ovecsize</i>,</b>
1832 <b>int *<i>workspace</i>, int <i>wscount</i>);</b>
1833 </P>
1834 <P>
1835 The function <b>pcre_dfa_exec()</b> is called to match a subject string against
1836 a compiled pattern, using a matching algorithm that scans the subject string
1837 just once, and does not backtrack. This has different characteristics to the
1838 normal algorithm, and is not compatible with Perl. Some of the features of PCRE
1839 patterns are not supported. Nevertheless, there are times when this kind of
1840 matching can be useful. For a discussion of the two matching algorithms, see
1841 the
1842 <a href="pcrematching.html"><b>pcrematching</b></a>
1843 documentation.
1844 </P>
1845 <P>
1846 The arguments for the <b>pcre_dfa_exec()</b> function are the same as for
1847 <b>pcre_exec()</b>, plus two extras. The <i>ovector</i> argument is used in a
1848 different way, and this is described below. The other common arguments are used
1849 in the same way as for <b>pcre_exec()</b>, so their description is not repeated
1850 here.
1851 </P>
1852 <P>
1853 The two additional arguments provide workspace for the function. The workspace
1854 vector should contain at least 20 elements. It is used for keeping track of
1855 multiple paths through the pattern tree. More workspace will be needed for
1856 patterns and subjects where there are a lot of potential matches.
1857 </P>
1858 <P>
1859 Here is an example of a simple call to <b>pcre_dfa_exec()</b>:
1860 <pre>
1861 int rc;
1862 int ovector[10];
1863 int wspace[20];
1864 rc = pcre_dfa_exec(
1865 re, /* result of pcre_compile() */
1866 NULL, /* we didn't study the pattern */
1867 "some string", /* the subject string */
1868 11, /* the length of the subject string */
1869 0, /* start at offset 0 in the subject */
1870 0, /* default options */
1871 ovector, /* vector of integers for substring information */
1872 10, /* number of elements (NOT size in bytes) */
1873 wspace, /* working space vector */
1874 20); /* number of elements (NOT size in bytes) */
1875 </PRE>
1876 </P>
1877 <br><b>
1878 Option bits for <b>pcre_dfa_exec()</b>
1879 </b><br>
1880 <P>
1881 The unused bits of the <i>options</i> argument for <b>pcre_dfa_exec()</b> must be
1882 zero. The only bits that may be set are PCRE_ANCHORED, PCRE_NEWLINE_<i>xxx</i>,
1885 four of these are exactly the same as for <b>pcre_exec()</b>, so their
1886 description is not repeated here.
1887 <pre>
1890 </pre>
1891 These have the same general effect as they do for <b>pcre_exec()</b>, but the
1892 details are slightly different. When PCRE_PARTIAL_HARD is set for
1893 <b>pcre_dfa_exec()</b>, it returns PCRE_ERROR_PARTIAL if the end of the subject
1894 is reached and there is still at least one matching possibility that requires
1895 additional characters. This happens even if some complete matches have also
1896 been found. When PCRE_PARTIAL_SOFT is set, the return code PCRE_ERROR_NOMATCH
1897 is converted into PCRE_ERROR_PARTIAL if the end of the subject is reached,
1898 there have been no complete matches, but there is still at least one matching
1899 possibility. The portion of the string that provided the longest partial match
1900 is set as the first matching string in both cases.
1901 <pre>
1903 </pre>
1904 Setting the PCRE_DFA_SHORTEST option causes the matching algorithm to stop as
1905 soon as it has found one match. Because of the way the alternative algorithm
1906 works, this is necessarily the shortest possible match at the first possible
1907 matching point in the subject string.
1908 <pre>
1910 </pre>
1911 When <b>pcre_dfa_exec()</b> returns a partial match, it is possible to call it
1912 again, with additional subject characters, and have it continue with the same
1913 match. The PCRE_DFA_RESTART option requests this action; when it is set, the
1914 <i>workspace</i> and <i>wscount</i> options must reference the same vector as
1915 before because data about the match so far is left in them after a partial
1916 match. There is more discussion of this facility in the
1917 <a href="pcrepartial.html"><b>pcrepartial</b></a>
1918 documentation.
1919 </P>
1920 <br><b>
1921 Successful returns from <b>pcre_dfa_exec()</b>
1922 </b><br>
1923 <P>
1924 When <b>pcre_dfa_exec()</b> succeeds, it may have matched more than one
1925 substring in the subject. Note, however, that all the matches from one run of
1926 the function start at the same point in the subject. The shorter matches are
1927 all initial substrings of the longer matches. For example, if the pattern
1928 <pre>
1929 &#60;.*&#62;
1930 </pre>
1931 is matched against the string
1932 <pre>
1933 This is &#60;something&#62; &#60;something else&#62; &#60;something further&#62; no more
1934 </pre>
1935 the three matched strings are
1936 <pre>
1937 &#60;something&#62;
1938 &#60;something&#62; &#60;something else&#62;
1939 &#60;something&#62; &#60;something else&#62; &#60;something further&#62;
1940 </pre>
1941 On success, the yield of the function is a number greater than zero, which is
1942 the number of matched substrings. The substrings themselves are returned in
1943 <i>ovector</i>. Each string uses two elements; the first is the offset to the
1944 start, and the second is the offset to the end. In fact, all the strings have
1945 the same start offset. (Space could have been saved by giving this only once,
1946 but it was decided to retain some compatibility with the way <b>pcre_exec()</b>
1947 returns data, even though the meaning of the strings is different.)
1948 </P>
1949 <P>
1950 The strings are returned in reverse order of length; that is, the longest
1951 matching string is given first. If there were too many matches to fit into
1952 <i>ovector</i>, the yield of the function is zero, and the vector is filled with
1953 the longest matches.
1954 </P>
1955 <br><b>
1956 Error returns from <b>pcre_dfa_exec()</b>
1957 </b><br>
1958 <P>
1959 The <b>pcre_dfa_exec()</b> function returns a negative number when it fails.
1960 Many of the errors are the same as for <b>pcre_exec()</b>, and these are
1961 described
1962 <a href="#errorlist">above.</a>
1963 There are in addition the following errors that are specific to
1964 <b>pcre_dfa_exec()</b>:
1965 <pre>
1967 </pre>
1968 This return is given if <b>pcre_dfa_exec()</b> encounters an item in the pattern
1969 that it does not support, for instance, the use of \C or a back reference.
1970 <pre>
1972 </pre>
1973 This return is given if <b>pcre_dfa_exec()</b> encounters a condition item that
1974 uses a back reference for the condition, or a test for recursion in a specific
1975 group. These are not supported.
1976 <pre>
1978 </pre>
1979 This return is given if <b>pcre_dfa_exec()</b> is called with an <i>extra</i>
1980 block that contains a setting of the <i>match_limit</i> field. This is not
1981 supported (it is meaningless).
1982 <pre>
1984 </pre>
1985 This return is given if <b>pcre_dfa_exec()</b> runs out of space in the
1986 <i>workspace</i> vector.
1987 <pre>
1989 </pre>
1990 When a recursive subpattern is processed, the matching function calls itself
1991 recursively, using private vectors for <i>ovector</i> and <i>workspace</i>. This
1992 error is given if the output vector is not large enough. This should be
1993 extremely rare, as a vector of size 1000 is used.
1994 </P>
1995 <br><a name="SEC20" href="#TOC1">SEE ALSO</a><br>
1996 <P>
1997 <b>pcrebuild</b>(3), <b>pcrecallout</b>(3), <b>pcrecpp(3)</b>(3),
1998 <b>pcrematching</b>(3), <b>pcrepartial</b>(3), <b>pcreposix</b>(3),
1999 <b>pcreprecompile</b>(3), <b>pcresample</b>(3), <b>pcrestack</b>(3).
2000 </P>
2001 <br><a name="SEC21" href="#TOC1">AUTHOR</a><br>
2002 <P>
2003 Philip Hazel
2004 <br>
2005 University Computing Service
2006 <br>
2007 Cambridge CB2 3QH, England.
2008 <br>
2009 </P>
2010 <br><a name="SEC22" href="#TOC1">REVISION</a><br>
2011 <P>
2012 Last updated: 01 September 2009
2013 <br>
2014 Copyright &copy; 1997-2009 University of Cambridge.
2015 <br>
2016 <p>
2017 Return to the <a href="index.html">PCRE index page</a>.
2018 </p>


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