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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 (unless there are
179 lookbehind assertions). However, this algorithm does not return captured
180 substrings. A description of the two matching algorithms and their advantages
181 and disadvantages is given in the
182 <a href="pcrematching.html"><b>pcrematching</b></a>
183 documentation.
184 </P>
185 <P>
186 In addition to the main compiling and matching functions, there are convenience
187 functions for extracting captured substrings from a subject string that is
188 matched by <b>pcre_exec()</b>. They are:
189 <pre>
190 <b>pcre_copy_substring()</b>
191 <b>pcre_copy_named_substring()</b>
192 <b>pcre_get_substring()</b>
193 <b>pcre_get_named_substring()</b>
194 <b>pcre_get_substring_list()</b>
195 <b>pcre_get_stringnumber()</b>
196 <b>pcre_get_stringtable_entries()</b>
197 </pre>
198 <b>pcre_free_substring()</b> and <b>pcre_free_substring_list()</b> are also
199 provided, to free the memory used for extracted strings.
200 </P>
201 <P>
202 The function <b>pcre_maketables()</b> is used to build a set of character tables
203 in the current locale for passing to <b>pcre_compile()</b>, <b>pcre_exec()</b>,
204 or <b>pcre_dfa_exec()</b>. This is an optional facility that is provided for
205 specialist use. Most commonly, no special tables are passed, in which case
206 internal tables that are generated when PCRE is built are used.
207 </P>
208 <P>
209 The function <b>pcre_fullinfo()</b> is used to find out information about a
210 compiled pattern; <b>pcre_info()</b> is an obsolete version that returns only
211 some of the available information, but is retained for backwards compatibility.
212 The function <b>pcre_version()</b> returns a pointer to a string containing the
213 version of PCRE and its date of release.
214 </P>
215 <P>
216 The function <b>pcre_refcount()</b> maintains a reference count in a data block
217 containing a compiled pattern. This is provided for the benefit of
218 object-oriented applications.
219 </P>
220 <P>
221 The global variables <b>pcre_malloc</b> and <b>pcre_free</b> initially contain
222 the entry points of the standard <b>malloc()</b> and <b>free()</b> functions,
223 respectively. PCRE calls the memory management functions via these variables,
224 so a calling program can replace them if it wishes to intercept the calls. This
225 should be done before calling any PCRE functions.
226 </P>
227 <P>
228 The global variables <b>pcre_stack_malloc</b> and <b>pcre_stack_free</b> are also
229 indirections to memory management functions. These special functions are used
230 only when PCRE is compiled to use the heap for remembering data, instead of
231 recursive function calls, when running the <b>pcre_exec()</b> function. See the
232 <a href="pcrebuild.html"><b>pcrebuild</b></a>
233 documentation for details of how to do this. It is a non-standard way of
234 building PCRE, for use in environments that have limited stacks. Because of the
235 greater use of memory management, it runs more slowly. Separate functions are
236 provided so that special-purpose external code can be used for this case. When
237 used, these functions are always called in a stack-like manner (last obtained,
238 first freed), and always for memory blocks of the same size. There is a
239 discussion about PCRE's stack usage in the
240 <a href="pcrestack.html"><b>pcrestack</b></a>
241 documentation.
242 </P>
243 <P>
244 The global variable <b>pcre_callout</b> initially contains NULL. It can be set
245 by the caller to a "callout" function, which PCRE will then call at specified
246 points during a matching operation. Details are given in the
247 <a href="pcrecallout.html"><b>pcrecallout</b></a>
248 documentation.
249 <a name="newlines"></a></P>
250 <br><a name="SEC3" href="#TOC1">NEWLINES</a><br>
251 <P>
252 PCRE supports five different conventions for indicating line breaks in
253 strings: a single CR (carriage return) character, a single LF (linefeed)
254 character, the two-character sequence CRLF, any of the three preceding, or any
255 Unicode newline sequence. The Unicode newline sequences are the three just
256 mentioned, plus the single characters VT (vertical tab, U+000B), FF (formfeed,
257 U+000C), NEL (next line, U+0085), LS (line separator, U+2028), and PS
258 (paragraph separator, U+2029).
259 </P>
260 <P>
261 Each of the first three conventions is used by at least one operating system as
262 its standard newline sequence. When PCRE is built, a default can be specified.
263 The default default is LF, which is the Unix standard. When PCRE is run, the
264 default can be overridden, either when a pattern is compiled, or when it is
265 matched.
266 </P>
267 <P>
268 At compile time, the newline convention can be specified by the <i>options</i>
269 argument of <b>pcre_compile()</b>, or it can be specified by special text at the
270 start of the pattern itself; this overrides any other settings. See the
271 <a href="pcrepattern.html"><b>pcrepattern</b></a>
272 page for details of the special character sequences.
273 </P>
274 <P>
275 In the PCRE documentation the word "newline" is used to mean "the character or
276 pair of characters that indicate a line break". The choice of newline
277 convention affects the handling of the dot, circumflex, and dollar
278 metacharacters, the handling of #-comments in /x mode, and, when CRLF is a
279 recognized line ending sequence, the match position advancement for a
280 non-anchored pattern. There is more detail about this in the
281 <a href="#execoptions">section on <b>pcre_exec()</b> options</a>
282 below.
283 </P>
284 <P>
285 The choice of newline convention does not affect the interpretation of
286 the \n or \r escape sequences, nor does it affect what \R matches, which is
287 controlled in a similar way, but by separate options.
288 </P>
289 <br><a name="SEC4" href="#TOC1">MULTITHREADING</a><br>
290 <P>
291 The PCRE functions can be used in multi-threading applications, with the
292 proviso that the memory management functions pointed to by <b>pcre_malloc</b>,
293 <b>pcre_free</b>, <b>pcre_stack_malloc</b>, and <b>pcre_stack_free</b>, and the
294 callout function pointed to by <b>pcre_callout</b>, are shared by all threads.
295 </P>
296 <P>
297 The compiled form of a regular expression is not altered during matching, so
298 the same compiled pattern can safely be used by several threads at once.
299 </P>
300 <br><a name="SEC5" href="#TOC1">SAVING PRECOMPILED PATTERNS FOR LATER USE</a><br>
301 <P>
302 The compiled form of a regular expression can be saved and re-used at a later
303 time, possibly by a different program, and even on a host other than the one on
304 which it was compiled. Details are given in the
305 <a href="pcreprecompile.html"><b>pcreprecompile</b></a>
306 documentation. However, compiling a regular expression with one version of PCRE
307 for use with a different version is not guaranteed to work and may cause
308 crashes.
309 </P>
310 <br><a name="SEC6" href="#TOC1">CHECKING BUILD-TIME OPTIONS</a><br>
311 <P>
312 <b>int pcre_config(int <i>what</i>, void *<i>where</i>);</b>
313 </P>
314 <P>
315 The function <b>pcre_config()</b> makes it possible for a PCRE client to
316 discover which optional features have been compiled into the PCRE library. The
317 <a href="pcrebuild.html"><b>pcrebuild</b></a>
318 documentation has more details about these optional features.
319 </P>
320 <P>
321 The first argument for <b>pcre_config()</b> is an integer, specifying which
322 information is required; the second argument is a pointer to a variable into
323 which the information is placed. The following information is available:
324 <pre>
326 </pre>
327 The output is an integer that is set to one if UTF-8 support is available;
328 otherwise it is set to zero.
329 <pre>
331 </pre>
332 The output is an integer that is set to one if support for Unicode character
333 properties is available; otherwise it is set to zero.
334 <pre>
336 </pre>
337 The output is an integer whose value specifies the default character sequence
338 that is recognized as meaning "newline". The four values that are supported
339 are: 10 for LF, 13 for CR, 3338 for CRLF, -2 for ANYCRLF, and -1 for ANY.
340 Though they are derived from ASCII, the same values are returned in EBCDIC
341 environments. The default should normally correspond to the standard sequence
342 for your operating system.
343 <pre>
345 </pre>
346 The output is an integer whose value indicates what character sequences the \R
347 escape sequence matches by default. A value of 0 means that \R matches any
348 Unicode line ending sequence; a value of 1 means that \R matches only CR, LF,
349 or CRLF. The default can be overridden when a pattern is compiled or matched.
350 <pre>
352 </pre>
353 The output is an integer that contains the number of bytes used for internal
354 linkage in compiled regular expressions. The value is 2, 3, or 4. Larger values
355 allow larger regular expressions to be compiled, at the expense of slower
356 matching. The default value of 2 is sufficient for all but the most massive
357 patterns, since it allows the compiled pattern to be up to 64K in size.
358 <pre>
360 </pre>
361 The output is an integer that contains the threshold above which the POSIX
362 interface uses <b>malloc()</b> for output vectors. Further details are given in
363 the
364 <a href="pcreposix.html"><b>pcreposix</b></a>
365 documentation.
366 <pre>
368 </pre>
369 The output is a long integer that gives the default limit for the number of
370 internal matching function calls in a <b>pcre_exec()</b> execution. Further
371 details are given with <b>pcre_exec()</b> below.
372 <pre>
374 </pre>
375 The output is a long integer that gives the default limit for the depth of
376 recursion when calling the internal matching function in a <b>pcre_exec()</b>
377 execution. Further details are given with <b>pcre_exec()</b> below.
378 <pre>
380 </pre>
381 The output is an integer that is set to one if internal recursion when running
382 <b>pcre_exec()</b> is implemented by recursive function calls that use the stack
383 to remember their state. This is the usual way that PCRE is compiled. The
384 output is zero if PCRE was compiled to use blocks of data on the heap instead
385 of recursive function calls. In this case, <b>pcre_stack_malloc</b> and
386 <b>pcre_stack_free</b> are called to manage memory blocks on the heap, thus
387 avoiding the use of the stack.
388 </P>
389 <br><a name="SEC7" href="#TOC1">COMPILING A PATTERN</a><br>
390 <P>
391 <b>pcre *pcre_compile(const char *<i>pattern</i>, int <i>options</i>,</b>
392 <b>const char **<i>errptr</i>, int *<i>erroffset</i>,</b>
393 <b>const unsigned char *<i>tableptr</i>);</b>
394 <b>pcre *pcre_compile2(const char *<i>pattern</i>, int <i>options</i>,</b>
395 <b>int *<i>errorcodeptr</i>,</b>
396 <b>const char **<i>errptr</i>, int *<i>erroffset</i>,</b>
397 <b>const unsigned char *<i>tableptr</i>);</b>
398 </P>
399 <P>
400 Either of the functions <b>pcre_compile()</b> or <b>pcre_compile2()</b> can be
401 called to compile a pattern into an internal form. The only difference between
402 the two interfaces is that <b>pcre_compile2()</b> has an additional argument,
403 <i>errorcodeptr</i>, via which a numerical error code can be returned.
404 </P>
405 <P>
406 The pattern is a C string terminated by a binary zero, and is passed in the
407 <i>pattern</i> argument. A pointer to a single block of memory that is obtained
408 via <b>pcre_malloc</b> is returned. This contains the compiled code and related
409 data. The <b>pcre</b> type is defined for the returned block; this is a typedef
410 for a structure whose contents are not externally defined. It is up to the
411 caller to free the memory (via <b>pcre_free</b>) when it is no longer required.
412 </P>
413 <P>
414 Although the compiled code of a PCRE regex is relocatable, that is, it does not
415 depend on memory location, the complete <b>pcre</b> data block is not
416 fully relocatable, because it may contain a copy of the <i>tableptr</i>
417 argument, which is an address (see below).
418 </P>
419 <P>
420 The <i>options</i> argument contains various bit settings that affect the
421 compilation. It should be zero if no options are required. The available
422 options are described below. Some of them (in particular, those that are
423 compatible with Perl, but also some others) can also be set and unset from
424 within the pattern (see the detailed description in the
425 <a href="pcrepattern.html"><b>pcrepattern</b></a>
426 documentation). For those options that can be different in different parts of
427 the pattern, the contents of the <i>options</i> argument specifies their initial
428 settings at the start of compilation and execution. The PCRE_ANCHORED and
429 PCRE_NEWLINE_<i>xxx</i> options can be set at the time of matching as well as at
430 compile time.
431 </P>
432 <P>
433 If <i>errptr</i> is NULL, <b>pcre_compile()</b> returns NULL immediately.
434 Otherwise, if compilation of a pattern fails, <b>pcre_compile()</b> returns
435 NULL, and sets the variable pointed to by <i>errptr</i> to point to a textual
436 error message. This is a static string that is part of the library. You must
437 not try to free it. The byte offset from the start of the pattern to the
438 character that was being processes when the error was discovered is placed in
439 the variable pointed to by <i>erroffset</i>, which must not be NULL. If it is,
440 an immediate error is given. Some errors are not detected until checks are
441 carried out when the whole pattern has been scanned; in this case the offset is
442 set to the end of the pattern.
443 </P>
444 <P>
445 If <b>pcre_compile2()</b> is used instead of <b>pcre_compile()</b>, and the
446 <i>errorcodeptr</i> argument is not NULL, a non-zero error code number is
447 returned via this argument in the event of an error. This is in addition to the
448 textual error message. Error codes and messages are listed below.
449 </P>
450 <P>
451 If the final argument, <i>tableptr</i>, is NULL, PCRE uses a default set of
452 character tables that are built when PCRE is compiled, using the default C
453 locale. Otherwise, <i>tableptr</i> must be an address that is the result of a
454 call to <b>pcre_maketables()</b>. This value is stored with the compiled
455 pattern, and used again by <b>pcre_exec()</b>, unless another table pointer is
456 passed to it. For more discussion, see the section on locale support below.
457 </P>
458 <P>
459 This code fragment shows a typical straightforward call to <b>pcre_compile()</b>:
460 <pre>
461 pcre *re;
462 const char *error;
463 int erroffset;
464 re = pcre_compile(
465 "^A.*Z", /* the pattern */
466 0, /* default options */
467 &error, /* for error message */
468 &erroffset, /* for error offset */
469 NULL); /* use default character tables */
470 </pre>
471 The following names for option bits are defined in the <b>pcre.h</b> header
472 file:
473 <pre>
475 </pre>
476 If this bit is set, the pattern is forced to be "anchored", that is, it is
477 constrained to match only at the first matching point in the string that is
478 being searched (the "subject string"). This effect can also be achieved by
479 appropriate constructs in the pattern itself, which is the only way to do it in
480 Perl.
481 <pre>
483 </pre>
484 If this bit is set, <b>pcre_compile()</b> automatically inserts callout items,
485 all with number 255, before each pattern item. For discussion of the callout
486 facility, see the
487 <a href="pcrecallout.html"><b>pcrecallout</b></a>
488 documentation.
489 <pre>
492 </pre>
493 These options (which are mutually exclusive) control what the \R escape
494 sequence matches. The choice is either to match only CR, LF, or CRLF, or to
495 match any Unicode newline sequence. The default is specified when PCRE is
496 built. It can be overridden from within the pattern, or by setting an option
497 when a compiled pattern is matched.
498 <pre>
500 </pre>
501 If this bit is set, letters in the pattern match both upper and lower case
502 letters. It is equivalent to Perl's /i option, and it can be changed within a
503 pattern by a (?i) option setting. In UTF-8 mode, PCRE always understands the
504 concept of case for characters whose values are less than 128, so caseless
505 matching is always possible. For characters with higher values, the concept of
506 case is supported if PCRE is compiled with Unicode property support, but not
507 otherwise. If you want to use caseless matching for characters 128 and above,
508 you must ensure that PCRE is compiled with Unicode property support as well as
509 with UTF-8 support.
510 <pre>
512 </pre>
513 If this bit is set, a dollar metacharacter in the pattern matches only at the
514 end of the subject string. Without this option, a dollar also matches
515 immediately before a newline at the end of the string (but not before any other
516 newlines). The PCRE_DOLLAR_ENDONLY option is ignored if PCRE_MULTILINE is set.
517 There is no equivalent to this option in Perl, and no way to set it within a
518 pattern.
519 <pre>
521 </pre>
522 If this bit is set, a dot metacharater in the pattern matches all characters,
523 including those that indicate newline. Without it, a dot does not match when
524 the current position is at a newline. This option is equivalent to Perl's /s
525 option, and it can be changed within a pattern by a (?s) option setting. A
526 negative class such as [^a] always matches newline characters, independent of
527 the setting of this option.
528 <pre>
530 </pre>
531 If this bit is set, names used to identify capturing subpatterns need not be
532 unique. This can be helpful for certain types of pattern when it is known that
533 only one instance of the named subpattern can ever be matched. There are more
534 details of named subpatterns below; see also the
535 <a href="pcrepattern.html"><b>pcrepattern</b></a>
536 documentation.
537 <pre>
539 </pre>
540 If this bit is set, whitespace data characters in the pattern are totally
541 ignored except when escaped or inside a character class. Whitespace does not
542 include the VT character (code 11). In addition, characters between an
543 unescaped # outside a character class and the next newline, inclusive, are also
544 ignored. This is equivalent to Perl's /x option, and it can be changed within a
545 pattern by a (?x) option setting.
546 </P>
547 <P>
548 This option makes it possible to include comments inside complicated patterns.
549 Note, however, that this applies only to data characters. Whitespace characters
550 may never appear within special character sequences in a pattern, for example
551 within the sequence (?( which introduces a conditional subpattern.
552 <pre>
554 </pre>
555 This option was invented in order to turn on additional functionality of PCRE
556 that is incompatible with Perl, but it is currently of very little use. When
557 set, any backslash in a pattern that is followed by a letter that has no
558 special meaning causes an error, thus reserving these combinations for future
559 expansion. By default, as in Perl, a backslash followed by a letter with no
560 special meaning is treated as a literal. (Perl can, however, be persuaded to
561 give a warning for this.) There are at present no other features controlled by
562 this option. It can also be set by a (?X) option setting within a pattern.
563 <pre>
565 </pre>
566 If this option is set, an unanchored pattern is required to match before or at
567 the first newline in the subject string, though the matched text may continue
568 over the newline.
569 <pre>
571 </pre>
572 If this option is set, PCRE's behaviour is changed in some ways so that it is
573 compatible with JavaScript rather than Perl. The changes are as follows:
574 </P>
575 <P>
576 (1) A lone closing square bracket in a pattern causes a compile-time error,
577 because this is illegal in JavaScript (by default it is treated as a data
578 character). Thus, the pattern AB]CD becomes illegal when this option is set.
579 </P>
580 <P>
581 (2) At run time, a back reference to an unset subpattern group matches an empty
582 string (by default this causes the current matching alternative to fail). A
583 pattern such as (\1)(a) succeeds when this option is set (assuming it can find
584 an "a" in the subject), whereas it fails by default, for Perl compatibility.
585 <pre>
587 </pre>
588 By default, PCRE treats the subject string as consisting of a single line of
589 characters (even if it actually contains newlines). The "start of line"
590 metacharacter (^) matches only at the start of the string, while the "end of
591 line" metacharacter ($) matches only at the end of the string, or before a
592 terminating newline (unless PCRE_DOLLAR_ENDONLY is set). This is the same as
593 Perl.
594 </P>
595 <P>
596 When PCRE_MULTILINE it is set, the "start of line" and "end of line" constructs
597 match immediately following or immediately before internal newlines in the
598 subject string, respectively, as well as at the very start and end. This is
599 equivalent to Perl's /m option, and it can be changed within a pattern by a
600 (?m) option setting. If there are no newlines in a subject string, or no
601 occurrences of ^ or $ in a pattern, setting PCRE_MULTILINE has no effect.
602 <pre>
608 </pre>
609 These options override the default newline definition that was chosen when PCRE
610 was built. Setting the first or the second specifies that a newline is
611 indicated by a single character (CR or LF, respectively). Setting
612 PCRE_NEWLINE_CRLF specifies that a newline is indicated by the two-character
613 CRLF sequence. Setting PCRE_NEWLINE_ANYCRLF specifies that any of the three
614 preceding sequences should be recognized. Setting PCRE_NEWLINE_ANY specifies
615 that any Unicode newline sequence should be recognized. The Unicode newline
616 sequences are the three just mentioned, plus the single characters VT (vertical
617 tab, U+000B), FF (formfeed, U+000C), NEL (next line, U+0085), LS (line
618 separator, U+2028), and PS (paragraph separator, U+2029). The last two are
619 recognized only in UTF-8 mode.
620 </P>
621 <P>
622 The newline setting in the options word uses three bits that are treated
623 as a number, giving eight possibilities. Currently only six are used (default
624 plus the five values above). This means that if you set more than one newline
625 option, the combination may or may not be sensible. For example,
627 other combinations may yield unused numbers and cause an error.
628 </P>
629 <P>
630 The only time that a line break is specially recognized when compiling a
631 pattern is if PCRE_EXTENDED is set, and an unescaped # outside a character
632 class is encountered. This indicates a comment that lasts until after the next
633 line break sequence. In other circumstances, line break sequences are treated
634 as literal data, except that in PCRE_EXTENDED mode, both CR and LF are treated
635 as whitespace characters and are therefore ignored.
636 </P>
637 <P>
638 The newline option that is set at compile time becomes the default that is used
639 for <b>pcre_exec()</b> and <b>pcre_dfa_exec()</b>, but it can be overridden.
640 <pre>
642 </pre>
643 If this option is set, it disables the use of numbered capturing parentheses in
644 the pattern. Any opening parenthesis that is not followed by ? behaves as if it
645 were followed by ?: but named parentheses can still be used for capturing (and
646 they acquire numbers in the usual way). There is no equivalent of this option
647 in Perl.
648 <pre>
650 </pre>
651 This option inverts the "greediness" of the quantifiers so that they are not
652 greedy by default, but become greedy if followed by "?". It is not compatible
653 with Perl. It can also be set by a (?U) option setting within the pattern.
654 <pre>
656 </pre>
657 This option causes PCRE to regard both the pattern and the subject as strings
658 of UTF-8 characters instead of single-byte character strings. However, it is
659 available only when PCRE is built to include UTF-8 support. If not, the use
660 of this option provokes an error. Details of how this option changes the
661 behaviour of PCRE are given in the
662 <a href="pcre.html#utf8support">section on UTF-8 support</a>
663 in the main
664 <a href="pcre.html"><b>pcre</b></a>
665 page.
666 <pre>
668 </pre>
669 When PCRE_UTF8 is set, the validity of the pattern as a UTF-8 string is
670 automatically checked. There is a discussion about the
671 <a href="pcre.html#utf8strings">validity of UTF-8 strings</a>
672 in the main
673 <a href="pcre.html"><b>pcre</b></a>
674 page. If an invalid UTF-8 sequence of bytes is found, <b>pcre_compile()</b>
675 returns an error. If you already know that your pattern is valid, and you want
676 to skip this check for performance reasons, you can set the PCRE_NO_UTF8_CHECK
677 option. When it is set, the effect of passing an invalid UTF-8 string as a
678 pattern is undefined. It may cause your program to crash. Note that this option
679 can also be passed to <b>pcre_exec()</b> and <b>pcre_dfa_exec()</b>, to suppress
680 the UTF-8 validity checking of subject strings.
681 </P>
682 <br><a name="SEC8" href="#TOC1">COMPILATION ERROR CODES</a><br>
683 <P>
684 The following table lists the error codes than may be returned by
685 <b>pcre_compile2()</b>, along with the error messages that may be returned by
686 both compiling functions. As PCRE has developed, some error codes have fallen
687 out of use. To avoid confusion, they have not been re-used.
688 <pre>
689 0 no error
690 1 \ at end of pattern
691 2 \c at end of pattern
692 3 unrecognized character follows \
693 4 numbers out of order in {} quantifier
694 5 number too big in {} quantifier
695 6 missing terminating ] for character class
696 7 invalid escape sequence in character class
697 8 range out of order in character class
698 9 nothing to repeat
699 10 [this code is not in use]
700 11 internal error: unexpected repeat
701 12 unrecognized character after (? or (?-
702 13 POSIX named classes are supported only within a class
703 14 missing )
704 15 reference to non-existent subpattern
705 16 erroffset passed as NULL
706 17 unknown option bit(s) set
707 18 missing ) after comment
708 19 [this code is not in use]
709 20 regular expression is too large
710 21 failed to get memory
711 22 unmatched parentheses
712 23 internal error: code overflow
713 24 unrecognized character after (?&#60;
714 25 lookbehind assertion is not fixed length
715 26 malformed number or name after (?(
716 27 conditional group contains more than two branches
717 28 assertion expected after (?(
718 29 (?R or (?[+-]digits must be followed by )
719 30 unknown POSIX class name
720 31 POSIX collating elements are not supported
721 32 this version of PCRE is not compiled with PCRE_UTF8 support
722 33 [this code is not in use]
723 34 character value in \x{...} sequence is too large
724 35 invalid condition (?(0)
725 36 \C not allowed in lookbehind assertion
726 37 PCRE does not support \L, \l, \N, \U, or \u
727 38 number after (?C is &#62; 255
728 39 closing ) for (?C expected
729 40 recursive call could loop indefinitely
730 41 unrecognized character after (?P
731 42 syntax error in subpattern name (missing terminator)
732 43 two named subpatterns have the same name
733 44 invalid UTF-8 string
734 45 support for \P, \p, and \X has not been compiled
735 46 malformed \P or \p sequence
736 47 unknown property name after \P or \p
737 48 subpattern name is too long (maximum 32 characters)
738 49 too many named subpatterns (maximum 10000)
739 50 [this code is not in use]
740 51 octal value is greater than \377 (not in UTF-8 mode)
741 52 internal error: overran compiling workspace
742 53 internal error: previously-checked referenced subpattern not found
743 54 DEFINE group contains more than one branch
744 55 repeating a DEFINE group is not allowed
745 56 inconsistent NEWLINE options
746 57 \g is not followed by a braced, angle-bracketed, or quoted
747 name/number or by a plain number
748 58 a numbered reference must not be zero
749 59 (*VERB) with an argument is not supported
750 60 (*VERB) not recognized
751 61 number is too big
752 62 subpattern name expected
753 63 digit expected after (?+
754 64 ] is an invalid data character in JavaScript compatibility mode
755 </pre>
756 The numbers 32 and 10000 in errors 48 and 49 are defaults; different values may
757 be used if the limits were changed when PCRE was built.
758 </P>
759 <br><a name="SEC9" href="#TOC1">STUDYING A PATTERN</a><br>
760 <P>
761 <b>pcre_extra *pcre_study(const pcre *<i>code</i>, int <i>options</i></b>
762 <b>const char **<i>errptr</i>);</b>
763 </P>
764 <P>
765 If a compiled pattern is going to be used several times, it is worth spending
766 more time analyzing it in order to speed up the time taken for matching. The
767 function <b>pcre_study()</b> takes a pointer to a compiled pattern as its first
768 argument. If studying the pattern produces additional information that will
769 help speed up matching, <b>pcre_study()</b> returns a pointer to a
770 <b>pcre_extra</b> block, in which the <i>study_data</i> field points to the
771 results of the study.
772 </P>
773 <P>
774 The returned value from <b>pcre_study()</b> can be passed directly to
775 <b>pcre_exec()</b>. However, a <b>pcre_extra</b> block also contains other
776 fields that can be set by the caller before the block is passed; these are
777 described
778 <a href="#extradata">below</a>
779 in the section on matching a pattern.
780 </P>
781 <P>
782 If studying the pattern does not produce any additional information
783 <b>pcre_study()</b> returns NULL. In that circumstance, if the calling program
784 wants to pass any of the other fields to <b>pcre_exec()</b>, it must set up its
785 own <b>pcre_extra</b> block.
786 </P>
787 <P>
788 The second argument of <b>pcre_study()</b> contains option bits. At present, no
789 options are defined, and this argument should always be zero.
790 </P>
791 <P>
792 The third argument for <b>pcre_study()</b> is a pointer for an error message. If
793 studying succeeds (even if no data is returned), the variable it points to is
794 set to NULL. Otherwise it is set to point to a textual error message. This is a
795 static string that is part of the library. You must not try to free it. You
796 should test the error pointer for NULL after calling <b>pcre_study()</b>, to be
797 sure that it has run successfully.
798 </P>
799 <P>
800 This is a typical call to <b>pcre_study</b>():
801 <pre>
802 pcre_extra *pe;
803 pe = pcre_study(
804 re, /* result of pcre_compile() */
805 0, /* no options exist */
806 &error); /* set to NULL or points to a message */
807 </pre>
808 At present, studying a pattern is useful only for non-anchored patterns that do
809 not have a single fixed starting character. A bitmap of possible starting
810 bytes is created.
811 <a name="localesupport"></a></P>
812 <br><a name="SEC10" href="#TOC1">LOCALE SUPPORT</a><br>
813 <P>
814 PCRE handles caseless matching, and determines whether characters are letters,
815 digits, or whatever, by reference to a set of tables, indexed by character
816 value. When running in UTF-8 mode, this applies only to characters with codes
817 less than 128. Higher-valued codes never match escapes such as \w or \d, but
818 can be tested with \p if PCRE is built with Unicode character property
819 support. The use of locales with Unicode is discouraged. If you are handling
820 characters with codes greater than 128, you should either use UTF-8 and
821 Unicode, or use locales, but not try to mix the two.
822 </P>
823 <P>
824 PCRE contains an internal set of tables that are used when the final argument
825 of <b>pcre_compile()</b> is NULL. These are sufficient for many applications.
826 Normally, the internal tables recognize only ASCII characters. However, when
827 PCRE is built, it is possible to cause the internal tables to be rebuilt in the
828 default "C" locale of the local system, which may cause them to be different.
829 </P>
830 <P>
831 The internal tables can always be overridden by tables supplied by the
832 application that calls PCRE. These may be created in a different locale from
833 the default. As more and more applications change to using Unicode, the need
834 for this locale support is expected to die away.
835 </P>
836 <P>
837 External tables are built by calling the <b>pcre_maketables()</b> function,
838 which has no arguments, in the relevant locale. The result can then be passed
839 to <b>pcre_compile()</b> or <b>pcre_exec()</b> as often as necessary. For
840 example, to build and use tables that are appropriate for the French locale
841 (where accented characters with values greater than 128 are treated as letters),
842 the following code could be used:
843 <pre>
844 setlocale(LC_CTYPE, "fr_FR");
845 tables = pcre_maketables();
846 re = pcre_compile(..., tables);
847 </pre>
848 The locale name "fr_FR" is used on Linux and other Unix-like systems; if you
849 are using Windows, the name for the French locale is "french".
850 </P>
851 <P>
852 When <b>pcre_maketables()</b> runs, the tables are built in memory that is
853 obtained via <b>pcre_malloc</b>. It is the caller's responsibility to ensure
854 that the memory containing the tables remains available for as long as it is
855 needed.
856 </P>
857 <P>
858 The pointer that is passed to <b>pcre_compile()</b> is saved with the compiled
859 pattern, and the same tables are used via this pointer by <b>pcre_study()</b>
860 and normally also by <b>pcre_exec()</b>. Thus, by default, for any single
861 pattern, compilation, studying and matching all happen in the same locale, but
862 different patterns can be compiled in different locales.
863 </P>
864 <P>
865 It is possible to pass a table pointer or NULL (indicating the use of the
866 internal tables) to <b>pcre_exec()</b>. Although not intended for this purpose,
867 this facility could be used to match a pattern in a different locale from the
868 one in which it was compiled. Passing table pointers at run time is discussed
869 below in the section on matching a pattern.
870 </P>
871 <br><a name="SEC11" href="#TOC1">INFORMATION ABOUT A PATTERN</a><br>
872 <P>
873 <b>int pcre_fullinfo(const pcre *<i>code</i>, const pcre_extra *<i>extra</i>,</b>
874 <b>int <i>what</i>, void *<i>where</i>);</b>
875 </P>
876 <P>
877 The <b>pcre_fullinfo()</b> function returns information about a compiled
878 pattern. It replaces the obsolete <b>pcre_info()</b> function, which is
879 nevertheless retained for backwards compability (and is documented below).
880 </P>
881 <P>
882 The first argument for <b>pcre_fullinfo()</b> is a pointer to the compiled
883 pattern. The second argument is the result of <b>pcre_study()</b>, or NULL if
884 the pattern was not studied. The third argument specifies which piece of
885 information is required, and the fourth argument is a pointer to a variable
886 to receive the data. The yield of the function is zero for success, or one of
887 the following negative numbers:
888 <pre>
889 PCRE_ERROR_NULL the argument <i>code</i> was NULL
890 the argument <i>where</i> was NULL
891 PCRE_ERROR_BADMAGIC the "magic number" was not found
892 PCRE_ERROR_BADOPTION the value of <i>what</i> was invalid
893 </pre>
894 The "magic number" is placed at the start of each compiled pattern as an simple
895 check against passing an arbitrary memory pointer. Here is a typical call of
896 <b>pcre_fullinfo()</b>, to obtain the length of the compiled pattern:
897 <pre>
898 int rc;
899 size_t length;
900 rc = pcre_fullinfo(
901 re, /* result of pcre_compile() */
902 pe, /* result of pcre_study(), or NULL */
903 PCRE_INFO_SIZE, /* what is required */
904 &length); /* where to put the data */
905 </pre>
906 The possible values for the third argument are defined in <b>pcre.h</b>, and are
907 as follows:
908 <pre>
910 </pre>
911 Return the number of the highest back reference in the pattern. The fourth
912 argument should point to an <b>int</b> variable. Zero is returned if there are
913 no back references.
914 <pre>
916 </pre>
917 Return the number of capturing subpatterns in the pattern. The fourth argument
918 should point to an <b>int</b> variable.
919 <pre>
921 </pre>
922 Return a pointer to the internal default character tables within PCRE. The
923 fourth argument should point to an <b>unsigned char *</b> variable. This
924 information call is provided for internal use by the <b>pcre_study()</b>
925 function. External callers can cause PCRE to use its internal tables by passing
926 a NULL table pointer.
927 <pre>
929 </pre>
930 Return information about the first byte of any matched string, for a
931 non-anchored pattern. The fourth argument should point to an <b>int</b>
932 variable. (This option used to be called PCRE_INFO_FIRSTCHAR; the old name is
933 still recognized for backwards compatibility.)
934 </P>
935 <P>
936 If there is a fixed first byte, for example, from a pattern such as
937 (cat|cow|coyote), its value is returned. Otherwise, if either
938 <br>
939 <br>
940 (a) the pattern was compiled with the PCRE_MULTILINE option, and every branch
941 starts with "^", or
942 <br>
943 <br>
944 (b) every branch of the pattern starts with ".*" and PCRE_DOTALL is not set
945 (if it were set, the pattern would be anchored),
946 <br>
947 <br>
948 -1 is returned, indicating that the pattern matches only at the start of a
949 subject string or after any newline within the string. Otherwise -2 is
950 returned. For anchored patterns, -2 is returned.
951 <pre>
953 </pre>
954 If the pattern was studied, and this resulted in the construction of a 256-bit
955 table indicating a fixed set of bytes for the first byte in any matching
956 string, a pointer to the table is returned. Otherwise NULL is returned. The
957 fourth argument should point to an <b>unsigned char *</b> variable.
958 <pre>
960 </pre>
961 Return 1 if the pattern contains any explicit matches for CR or LF characters,
962 otherwise 0. The fourth argument should point to an <b>int</b> variable. An
963 explicit match is either a literal CR or LF character, or \r or \n.
964 <pre>
966 </pre>
967 Return 1 if the (?J) or (?-J) option setting is used in the pattern, otherwise
968 0. The fourth argument should point to an <b>int</b> variable. (?J) and
969 (?-J) set and unset the local PCRE_DUPNAMES option, respectively.
970 <pre>
972 </pre>
973 Return the value of the rightmost literal byte that must exist in any matched
974 string, other than at its start, if such a byte has been recorded. The fourth
975 argument should point to an <b>int</b> variable. If there is no such byte, -1 is
976 returned. For anchored patterns, a last literal byte is recorded only if it
977 follows something of variable length. For example, for the pattern
978 /^a\d+z\d+/ the returned value is "z", but for /^a\dz\d/ the returned value
979 is -1.
980 <pre>
984 </pre>
985 PCRE supports the use of named as well as numbered capturing parentheses. The
986 names are just an additional way of identifying the parentheses, which still
987 acquire numbers. Several convenience functions such as
988 <b>pcre_get_named_substring()</b> are provided for extracting captured
989 substrings by name. It is also possible to extract the data directly, by first
990 converting the name to a number in order to access the correct pointers in the
991 output vector (described with <b>pcre_exec()</b> below). To do the conversion,
992 you need to use the name-to-number map, which is described by these three
993 values.
994 </P>
995 <P>
996 The map consists of a number of fixed-size entries. PCRE_INFO_NAMECOUNT gives
997 the number of entries, and PCRE_INFO_NAMEENTRYSIZE gives the size of each
998 entry; both of these return an <b>int</b> value. The entry size depends on the
999 length of the longest name. PCRE_INFO_NAMETABLE returns a pointer to the first
1000 entry of the table (a pointer to <b>char</b>). The first two bytes of each entry
1001 are the number of the capturing parenthesis, most significant byte first. The
1002 rest of the entry is the corresponding name, zero terminated. The names are in
1003 alphabetical order. When PCRE_DUPNAMES is set, duplicate names are in order of
1004 their parentheses numbers. For example, consider the following pattern (assume
1005 PCRE_EXTENDED is set, so white space - including newlines - is ignored):
1006 <pre>
1007 (?&#60;date&#62; (?&#60;year&#62;(\d\d)?\d\d) - (?&#60;month&#62;\d\d) - (?&#60;day&#62;\d\d) )
1008 </pre>
1009 There are four named subpatterns, so the table has four entries, and each entry
1010 in the table is eight bytes long. The table is as follows, with non-printing
1011 bytes shows in hexadecimal, and undefined bytes shown as ??:
1012 <pre>
1013 00 01 d a t e 00 ??
1014 00 05 d a y 00 ?? ??
1015 00 04 m o n t h 00
1016 00 02 y e a r 00 ??
1017 </pre>
1018 When writing code to extract data from named subpatterns using the
1019 name-to-number map, remember that the length of the entries is likely to be
1020 different for each compiled pattern.
1021 <pre>
1023 </pre>
1024 Return 1 if the pattern can be used for partial matching with
1025 <b>pcre_exec()</b>, otherwise 0. The fourth argument should point to an
1026 <b>int</b> variable. From release 8.00, this always returns 1, because the
1027 restrictions that previously applied to partial matching have been lifted. The
1028 <a href="pcrepartial.html"><b>pcrepartial</b></a>
1029 documentation gives details of partial matching.
1030 <pre>
1032 </pre>
1033 Return a copy of the options with which the pattern was compiled. The fourth
1034 argument should point to an <b>unsigned long int</b> variable. These option bits
1035 are those specified in the call to <b>pcre_compile()</b>, modified by any
1036 top-level option settings at the start of the pattern itself. In other words,
1037 they are the options that will be in force when matching starts. For example,
1038 if the pattern /(?im)abc(?-i)d/ is compiled with the PCRE_EXTENDED option, the
1040 </P>
1041 <P>
1042 A pattern is automatically anchored by PCRE if all of its top-level
1043 alternatives begin with one of the following:
1044 <pre>
1045 ^ unless PCRE_MULTILINE is set
1046 \A always
1047 \G always
1048 .* if PCRE_DOTALL is set and there are no back references to the subpattern in which .* appears
1049 </pre>
1050 For such patterns, the PCRE_ANCHORED bit is set in the options returned by
1051 <b>pcre_fullinfo()</b>.
1052 <pre>
1054 </pre>
1055 Return the size of the compiled pattern, that is, the value that was passed as
1056 the argument to <b>pcre_malloc()</b> when PCRE was getting memory in which to
1057 place the compiled data. The fourth argument should point to a <b>size_t</b>
1058 variable.
1059 <pre>
1061 </pre>
1062 Return the size of the data block pointed to by the <i>study_data</i> field in
1063 a <b>pcre_extra</b> block. That is, it is the value that was passed to
1064 <b>pcre_malloc()</b> when PCRE was getting memory into which to place the data
1065 created by <b>pcre_study()</b>. The fourth argument should point to a
1066 <b>size_t</b> variable.
1067 </P>
1068 <br><a name="SEC12" href="#TOC1">OBSOLETE INFO FUNCTION</a><br>
1069 <P>
1070 <b>int pcre_info(const pcre *<i>code</i>, int *<i>optptr</i>, int</b>
1071 <b>*<i>firstcharptr</i>);</b>
1072 </P>
1073 <P>
1074 The <b>pcre_info()</b> function is now obsolete because its interface is too
1075 restrictive to return all the available data about a compiled pattern. New
1076 programs should use <b>pcre_fullinfo()</b> instead. The yield of
1077 <b>pcre_info()</b> is the number of capturing subpatterns, or one of the
1078 following negative numbers:
1079 <pre>
1080 PCRE_ERROR_NULL the argument <i>code</i> was NULL
1081 PCRE_ERROR_BADMAGIC the "magic number" was not found
1082 </pre>
1083 If the <i>optptr</i> argument is not NULL, a copy of the options with which the
1084 pattern was compiled is placed in the integer it points to (see
1085 PCRE_INFO_OPTIONS above).
1086 </P>
1087 <P>
1088 If the pattern is not anchored and the <i>firstcharptr</i> argument is not NULL,
1089 it is used to pass back information about the first character of any matched
1090 string (see PCRE_INFO_FIRSTBYTE above).
1091 </P>
1092 <br><a name="SEC13" href="#TOC1">REFERENCE COUNTS</a><br>
1093 <P>
1094 <b>int pcre_refcount(pcre *<i>code</i>, int <i>adjust</i>);</b>
1095 </P>
1096 <P>
1097 The <b>pcre_refcount()</b> function is used to maintain a reference count in the
1098 data block that contains a compiled pattern. It is provided for the benefit of
1099 applications that operate in an object-oriented manner, where different parts
1100 of the application may be using the same compiled pattern, but you want to free
1101 the block when they are all done.
1102 </P>
1103 <P>
1104 When a pattern is compiled, the reference count field is initialized to zero.
1105 It is changed only by calling this function, whose action is to add the
1106 <i>adjust</i> value (which may be positive or negative) to it. The yield of the
1107 function is the new value. However, the value of the count is constrained to
1108 lie between 0 and 65535, inclusive. If the new value is outside these limits,
1109 it is forced to the appropriate limit value.
1110 </P>
1111 <P>
1112 Except when it is zero, the reference count is not correctly preserved if a
1113 pattern is compiled on one host and then transferred to a host whose byte-order
1114 is different. (This seems a highly unlikely scenario.)
1115 </P>
1116 <br><a name="SEC14" href="#TOC1">MATCHING A PATTERN: THE TRADITIONAL FUNCTION</a><br>
1117 <P>
1118 <b>int pcre_exec(const pcre *<i>code</i>, const pcre_extra *<i>extra</i>,</b>
1119 <b>const char *<i>subject</i>, int <i>length</i>, int <i>startoffset</i>,</b>
1120 <b>int <i>options</i>, int *<i>ovector</i>, int <i>ovecsize</i>);</b>
1121 </P>
1122 <P>
1123 The function <b>pcre_exec()</b> is called to match a subject string against a
1124 compiled pattern, which is passed in the <i>code</i> argument. If the
1125 pattern has been studied, the result of the study should be passed in the
1126 <i>extra</i> argument. This function is the main matching facility of the
1127 library, and it operates in a Perl-like manner. For specialist use there is
1128 also an alternative matching function, which is described
1129 <a href="#dfamatch">below</a>
1130 in the section about the <b>pcre_dfa_exec()</b> function.
1131 </P>
1132 <P>
1133 In most applications, the pattern will have been compiled (and optionally
1134 studied) in the same process that calls <b>pcre_exec()</b>. However, it is
1135 possible to save compiled patterns and study data, and then use them later
1136 in different processes, possibly even on different hosts. For a discussion
1137 about this, see the
1138 <a href="pcreprecompile.html"><b>pcreprecompile</b></a>
1139 documentation.
1140 </P>
1141 <P>
1142 Here is an example of a simple call to <b>pcre_exec()</b>:
1143 <pre>
1144 int rc;
1145 int ovector[30];
1146 rc = pcre_exec(
1147 re, /* result of pcre_compile() */
1148 NULL, /* we didn't study the pattern */
1149 "some string", /* the subject string */
1150 11, /* the length of the subject string */
1151 0, /* start at offset 0 in the subject */
1152 0, /* default options */
1153 ovector, /* vector of integers for substring information */
1154 30); /* number of elements (NOT size in bytes) */
1155 <a name="extradata"></a></PRE>
1156 </P>
1157 <br><b>
1158 Extra data for <b>pcre_exec()</b>
1159 </b><br>
1160 <P>
1161 If the <i>extra</i> argument is not NULL, it must point to a <b>pcre_extra</b>
1162 data block. The <b>pcre_study()</b> function returns such a block (when it
1163 doesn't return NULL), but you can also create one for yourself, and pass
1164 additional information in it. The <b>pcre_extra</b> block contains the following
1165 fields (not necessarily in this order):
1166 <pre>
1167 unsigned long int <i>flags</i>;
1168 void *<i>study_data</i>;
1169 unsigned long int <i>match_limit</i>;
1170 unsigned long int <i>match_limit_recursion</i>;
1171 void *<i>callout_data</i>;
1172 const unsigned char *<i>tables</i>;
1173 </pre>
1174 The <i>flags</i> field is a bitmap that specifies which of the other fields
1175 are set. The flag bits are:
1176 <pre>
1182 </pre>
1183 Other flag bits should be set to zero. The <i>study_data</i> field is set in the
1184 <b>pcre_extra</b> block that is returned by <b>pcre_study()</b>, together with
1185 the appropriate flag bit. You should not set this yourself, but you may add to
1186 the block by setting the other fields and their corresponding flag bits.
1187 </P>
1188 <P>
1189 The <i>match_limit</i> field provides a means of preventing PCRE from using up a
1190 vast amount of resources when running patterns that are not going to match,
1191 but which have a very large number of possibilities in their search trees. The
1192 classic example is the use of nested unlimited repeats.
1193 </P>
1194 <P>
1195 Internally, PCRE uses a function called <b>match()</b> which it calls repeatedly
1196 (sometimes recursively). The limit set by <i>match_limit</i> is imposed on the
1197 number of times this function is called during a match, which has the effect of
1198 limiting the amount of backtracking that can take place. For patterns that are
1199 not anchored, the count restarts from zero for each position in the subject
1200 string.
1201 </P>
1202 <P>
1203 The default value for the limit can be set when PCRE is built; the default
1204 default is 10 million, which handles all but the most extreme cases. You can
1205 override the default by suppling <b>pcre_exec()</b> with a <b>pcre_extra</b>
1206 block in which <i>match_limit</i> is set, and PCRE_EXTRA_MATCH_LIMIT is set in
1207 the <i>flags</i> field. If the limit is exceeded, <b>pcre_exec()</b> returns
1209 </P>
1210 <P>
1211 The <i>match_limit_recursion</i> field is similar to <i>match_limit</i>, but
1212 instead of limiting the total number of times that <b>match()</b> is called, it
1213 limits the depth of recursion. The recursion depth is a smaller number than the
1214 total number of calls, because not all calls to <b>match()</b> are recursive.
1215 This limit is of use only if it is set smaller than <i>match_limit</i>.
1216 </P>
1217 <P>
1218 Limiting the recursion depth limits the amount of stack that can be used, or,
1219 when PCRE has been compiled to use memory on the heap instead of the stack, the
1220 amount of heap memory that can be used.
1221 </P>
1222 <P>
1223 The default value for <i>match_limit_recursion</i> can be set when PCRE is
1224 built; the default default is the same value as the default for
1225 <i>match_limit</i>. You can override the default by suppling <b>pcre_exec()</b>
1226 with a <b>pcre_extra</b> block in which <i>match_limit_recursion</i> is set, and
1227 PCRE_EXTRA_MATCH_LIMIT_RECURSION is set in the <i>flags</i> field. If the limit
1228 is exceeded, <b>pcre_exec()</b> returns PCRE_ERROR_RECURSIONLIMIT.
1229 </P>
1230 <P>
1231 The <i>callout_data</i> field is used in conjunction with the "callout" feature,
1232 and is described in the
1233 <a href="pcrecallout.html"><b>pcrecallout</b></a>
1234 documentation.
1235 </P>
1236 <P>
1237 The <i>tables</i> field is used to pass a character tables pointer to
1238 <b>pcre_exec()</b>; this overrides the value that is stored with the compiled
1239 pattern. A non-NULL value is stored with the compiled pattern only if custom
1240 tables were supplied to <b>pcre_compile()</b> via its <i>tableptr</i> argument.
1241 If NULL is passed to <b>pcre_exec()</b> using this mechanism, it forces PCRE's
1242 internal tables to be used. This facility is helpful when re-using patterns
1243 that have been saved after compiling with an external set of tables, because
1244 the external tables might be at a different address when <b>pcre_exec()</b> is
1245 called. See the
1246 <a href="pcreprecompile.html"><b>pcreprecompile</b></a>
1247 documentation for a discussion of saving compiled patterns for later use.
1248 <a name="execoptions"></a></P>
1249 <br><b>
1250 Option bits for <b>pcre_exec()</b>
1251 </b><br>
1252 <P>
1253 The unused bits of the <i>options</i> argument for <b>pcre_exec()</b> must be
1254 zero. The only bits that may be set are PCRE_ANCHORED, PCRE_NEWLINE_<i>xxx</i>,
1258 <pre>
1260 </pre>
1261 The PCRE_ANCHORED option limits <b>pcre_exec()</b> to matching at the first
1262 matching position. If a pattern was compiled with PCRE_ANCHORED, or turned out
1263 to be anchored by virtue of its contents, it cannot be made unachored at
1264 matching time.
1265 <pre>
1268 </pre>
1269 These options (which are mutually exclusive) control what the \R escape
1270 sequence matches. The choice is either to match only CR, LF, or CRLF, or to
1271 match any Unicode newline sequence. These options override the choice that was
1272 made or defaulted when the pattern was compiled.
1273 <pre>
1279 </pre>
1280 These options override the newline definition that was chosen or defaulted when
1281 the pattern was compiled. For details, see the description of
1282 <b>pcre_compile()</b> above. During matching, the newline choice affects the
1283 behaviour of the dot, circumflex, and dollar metacharacters. It may also alter
1284 the way the match position is advanced after a match failure for an unanchored
1285 pattern.
1286 </P>
1287 <P>
1289 match attempt for an unanchored pattern fails when the current position is at a
1290 CRLF sequence, and the pattern contains no explicit matches for CR or LF
1291 characters, the match position is advanced by two characters instead of one, in
1292 other words, to after the CRLF.
1293 </P>
1294 <P>
1295 The above rule is a compromise that makes the most common cases work as
1296 expected. For example, if the pattern is .+A (and the PCRE_DOTALL option is not
1297 set), it does not match the string "\r\nA" because, after failing at the
1298 start, it skips both the CR and the LF before retrying. However, the pattern
1299 [\r\n]A does match that string, because it contains an explicit CR or LF
1300 reference, and so advances only by one character after the first failure.
1301 </P>
1302 <P>
1303 An explicit match for CR of LF is either a literal appearance of one of those
1304 characters, or one of the \r or \n escape sequences. Implicit matches such as
1305 [^X] do not count, nor does \s (which includes CR and LF in the characters
1306 that it matches).
1307 </P>
1308 <P>
1309 Notwithstanding the above, anomalous effects may still occur when CRLF is a
1310 valid newline sequence and explicit \r or \n escapes appear in the pattern.
1311 <pre>
1313 </pre>
1314 This option specifies that first character of the subject string is not the
1315 beginning of a line, so the circumflex metacharacter should not match before
1316 it. Setting this without PCRE_MULTILINE (at compile time) causes circumflex
1317 never to match. This option affects only the behaviour of the circumflex
1318 metacharacter. It does not affect \A.
1319 <pre>
1321 </pre>
1322 This option specifies that the end of the subject string is not the end of a
1323 line, so the dollar metacharacter should not match it nor (except in multiline
1324 mode) a newline immediately before it. Setting this without PCRE_MULTILINE (at
1325 compile time) causes dollar never to match. This option affects only the
1326 behaviour of the dollar metacharacter. It does not affect \Z or \z.
1327 <pre>
1329 </pre>
1330 An empty string is not considered to be a valid match if this option is set. If
1331 there are alternatives in the pattern, they are tried. If all the alternatives
1332 match the empty string, the entire match fails. For example, if the pattern
1333 <pre>
1334 a?b?
1335 </pre>
1336 is applied to a string not beginning with "a" or "b", it matches an empty
1337 string at the start of the subject. With PCRE_NOTEMPTY set, this match is not
1338 valid, so PCRE searches further into the string for occurrences of "a" or "b".
1339 <pre>
1341 </pre>
1342 This is like PCRE_NOTEMPTY, except that an empty string match that is not at
1343 the start of the subject is permitted. If the pattern is anchored, such a match
1344 can occur only if the pattern contains \K.
1345 </P>
1346 <P>
1347 Perl has no direct equivalent of PCRE_NOTEMPTY or PCRE_NOTEMPTY_ATSTART, but it
1348 does make a special case of a pattern match of the empty string within its
1349 <b>split()</b> function, and when using the /g modifier. It is possible to
1350 emulate Perl's behaviour after matching a null string by first trying the match
1351 again at the same offset with PCRE_NOTEMPTY_ATSTART and PCRE_ANCHORED, and then
1352 if that fails, by advancing the starting offset (see below) and trying an
1353 ordinary match again. There is some code that demonstrates how to do this in
1354 the
1355 <a href="pcredemo.html"><b>pcredemo</b></a>
1356 sample program.
1357 <pre>
1359 </pre>
1360 There are a number of optimizations that <b>pcre_exec()</b> uses at the start of
1361 a match, in order to speed up the process. For example, if it is known that a
1362 match must start with a specific character, it searches the subject for that
1363 character, and fails immediately if it cannot find it, without actually running
1364 the main matching function. When callouts are in use, these optimizations can
1365 cause them to be skipped. This option disables the "start-up" optimizations,
1366 causing performance to suffer, but ensuring that the callouts do occur.
1367 <pre>
1369 </pre>
1370 When PCRE_UTF8 is set at compile time, the validity of the subject as a UTF-8
1371 string is automatically checked when <b>pcre_exec()</b> is subsequently called.
1372 The value of <i>startoffset</i> is also checked to ensure that it points to the
1373 start of a UTF-8 character. There is a discussion about the validity of UTF-8
1374 strings in the
1375 <a href="pcre.html#utf8strings">section on UTF-8 support</a>
1376 in the main
1377 <a href="pcre.html"><b>pcre</b></a>
1378 page. If an invalid UTF-8 sequence of bytes is found, <b>pcre_exec()</b> returns
1379 the error PCRE_ERROR_BADUTF8. If <i>startoffset</i> contains an invalid value,
1380 PCRE_ERROR_BADUTF8_OFFSET is returned.
1381 </P>
1382 <P>
1383 If you already know that your subject is valid, and you want to skip these
1384 checks for performance reasons, you can set the PCRE_NO_UTF8_CHECK option when
1385 calling <b>pcre_exec()</b>. You might want to do this for the second and
1386 subsequent calls to <b>pcre_exec()</b> if you are making repeated calls to find
1387 all the matches in a single subject string. However, you should be sure that
1388 the value of <i>startoffset</i> points to the start of a UTF-8 character. When
1389 PCRE_NO_UTF8_CHECK is set, the effect of passing an invalid UTF-8 string as a
1390 subject, or a value of <i>startoffset</i> that does not point to the start of a
1391 UTF-8 character, is undefined. Your program may crash.
1392 <pre>
1395 </pre>
1396 These options turn on the partial matching feature. For backwards
1397 compatibility, PCRE_PARTIAL is a synonym for PCRE_PARTIAL_SOFT. A partial match
1398 occurs if the end of the subject string is reached successfully, but there are
1399 not enough subject characters to complete the match. If this happens when
1400 PCRE_PARTIAL_HARD is set, <b>pcre_exec()</b> immediately returns
1401 PCRE_ERROR_PARTIAL. Otherwise, if PCRE_PARTIAL_SOFT is set, matching continues
1402 by testing any other alternatives. Only if they all fail is PCRE_ERROR_PARTIAL
1403 returned (instead of PCRE_ERROR_NOMATCH). The portion of the string that
1404 was inspected when the partial match was found is set as the first matching
1405 string. There is a more detailed discussion in the
1406 <a href="pcrepartial.html"><b>pcrepartial</b></a>
1407 documentation.
1408 </P>
1409 <br><b>
1410 The string to be matched by <b>pcre_exec()</b>
1411 </b><br>
1412 <P>
1413 The subject string is passed to <b>pcre_exec()</b> as a pointer in
1414 <i>subject</i>, a length (in bytes) in <i>length</i>, and a starting byte offset
1415 in <i>startoffset</i>. In UTF-8 mode, the byte offset must point to the start of
1416 a UTF-8 character. Unlike the pattern string, the subject may contain binary
1417 zero bytes. When the starting offset is zero, the search for a match starts at
1418 the beginning of the subject, and this is by far the most common case.
1419 </P>
1420 <P>
1421 A non-zero starting offset is useful when searching for another match in the
1422 same subject by calling <b>pcre_exec()</b> again after a previous success.
1423 Setting <i>startoffset</i> differs from just passing over a shortened string and
1424 setting PCRE_NOTBOL in the case of a pattern that begins with any kind of
1425 lookbehind. For example, consider the pattern
1426 <pre>
1427 \Biss\B
1428 </pre>
1429 which finds occurrences of "iss" in the middle of words. (\B matches only if
1430 the current position in the subject is not a word boundary.) When applied to
1431 the string "Mississipi" the first call to <b>pcre_exec()</b> finds the first
1432 occurrence. If <b>pcre_exec()</b> is called again with just the remainder of the
1433 subject, namely "issipi", it does not match, because \B is always false at the
1434 start of the subject, which is deemed to be a word boundary. However, if
1435 <b>pcre_exec()</b> is passed the entire string again, but with <i>startoffset</i>
1436 set to 4, it finds the second occurrence of "iss" because it is able to look
1437 behind the starting point to discover that it is preceded by a letter.
1438 </P>
1439 <P>
1440 If a non-zero starting offset is passed when the pattern is anchored, one
1441 attempt to match at the given offset is made. This can only succeed if the
1442 pattern does not require the match to be at the start of the subject.
1443 </P>
1444 <br><b>
1445 How <b>pcre_exec()</b> returns captured substrings
1446 </b><br>
1447 <P>
1448 In general, a pattern matches a certain portion of the subject, and in
1449 addition, further substrings from the subject may be picked out by parts of the
1450 pattern. Following the usage in Jeffrey Friedl's book, this is called
1451 "capturing" in what follows, and the phrase "capturing subpattern" is used for
1452 a fragment of a pattern that picks out a substring. PCRE supports several other
1453 kinds of parenthesized subpattern that do not cause substrings to be captured.
1454 </P>
1455 <P>
1456 Captured substrings are returned to the caller via a vector of integers whose
1457 address is passed in <i>ovector</i>. The number of elements in the vector is
1458 passed in <i>ovecsize</i>, which must be a non-negative number. <b>Note</b>: this
1459 argument is NOT the size of <i>ovector</i> in bytes.
1460 </P>
1461 <P>
1462 The first two-thirds of the vector is used to pass back captured substrings,
1463 each substring using a pair of integers. The remaining third of the vector is
1464 used as workspace by <b>pcre_exec()</b> while matching capturing subpatterns,
1465 and is not available for passing back information. The number passed in
1466 <i>ovecsize</i> should always be a multiple of three. If it is not, it is
1467 rounded down.
1468 </P>
1469 <P>
1470 When a match is successful, information about captured substrings is returned
1471 in pairs of integers, starting at the beginning of <i>ovector</i>, and
1472 continuing up to two-thirds of its length at the most. The first element of
1473 each pair is set to the byte offset of the first character in a substring, and
1474 the second is set to the byte offset of the first character after the end of a
1475 substring. <b>Note</b>: these values are always byte offsets, even in UTF-8
1476 mode. They are not character counts.
1477 </P>
1478 <P>
1479 The first pair of integers, <i>ovector[0]</i> and <i>ovector[1]</i>, identify the
1480 portion of the subject string matched by the entire pattern. The next pair is
1481 used for the first capturing subpattern, and so on. The value returned by
1482 <b>pcre_exec()</b> is one more than the highest numbered pair that has been set.
1483 For example, if two substrings have been captured, the returned value is 3. If
1484 there are no capturing subpatterns, the return value from a successful match is
1485 1, indicating that just the first pair of offsets has been set.
1486 </P>
1487 <P>
1488 If a capturing subpattern is matched repeatedly, it is the last portion of the
1489 string that it matched that is returned.
1490 </P>
1491 <P>
1492 If the vector is too small to hold all the captured substring offsets, it is
1493 used as far as possible (up to two-thirds of its length), and the function
1494 returns a value of zero. If the substring offsets are not of interest,
1495 <b>pcre_exec()</b> may be called with <i>ovector</i> passed as NULL and
1496 <i>ovecsize</i> as zero. However, if the pattern contains back references and
1497 the <i>ovector</i> is not big enough to remember the related substrings, PCRE
1498 has to get additional memory for use during matching. Thus it is usually
1499 advisable to supply an <i>ovector</i>.
1500 </P>
1501 <P>
1502 The <b>pcre_info()</b> function can be used to find out how many capturing
1503 subpatterns there are in a compiled pattern. The smallest size for
1504 <i>ovector</i> that will allow for <i>n</i> captured substrings, in addition to
1505 the offsets of the substring matched by the whole pattern, is (<i>n</i>+1)*3.
1506 </P>
1507 <P>
1508 It is possible for capturing subpattern number <i>n+1</i> to match some part of
1509 the subject when subpattern <i>n</i> has not been used at all. For example, if
1510 the string "abc" is matched against the pattern (a|(z))(bc) the return from the
1511 function is 4, and subpatterns 1 and 3 are matched, but 2 is not. When this
1512 happens, both values in the offset pairs corresponding to unused subpatterns
1513 are set to -1.
1514 </P>
1515 <P>
1516 Offset values that correspond to unused subpatterns at the end of the
1517 expression are also set to -1. For example, if the string "abc" is matched
1518 against the pattern (abc)(x(yz)?)? subpatterns 2 and 3 are not matched. The
1519 return from the function is 2, because the highest used capturing subpattern
1520 number is 1. However, you can refer to the offsets for the second and third
1521 capturing subpatterns if you wish (assuming the vector is large enough, of
1522 course).
1523 </P>
1524 <P>
1525 Some convenience functions are provided for extracting the captured substrings
1526 as separate strings. These are described below.
1527 <a name="errorlist"></a></P>
1528 <br><b>
1529 Error return values from <b>pcre_exec()</b>
1530 </b><br>
1531 <P>
1532 If <b>pcre_exec()</b> fails, it returns a negative number. The following are
1533 defined in the header file:
1534 <pre>
1536 </pre>
1537 The subject string did not match the pattern.
1538 <pre>
1540 </pre>
1541 Either <i>code</i> or <i>subject</i> was passed as NULL, or <i>ovector</i> was
1542 NULL and <i>ovecsize</i> was not zero.
1543 <pre>
1545 </pre>
1546 An unrecognized bit was set in the <i>options</i> argument.
1547 <pre>
1549 </pre>
1550 PCRE stores a 4-byte "magic number" at the start of the compiled code, to catch
1551 the case when it is passed a junk pointer and to detect when a pattern that was
1552 compiled in an environment of one endianness is run in an environment with the
1553 other endianness. This is the error that PCRE gives when the magic number is
1554 not present.
1555 <pre>
1557 </pre>
1558 While running the pattern match, an unknown item was encountered in the
1559 compiled pattern. This error could be caused by a bug in PCRE or by overwriting
1560 of the compiled pattern.
1561 <pre>
1563 </pre>
1564 If a pattern contains back references, but the <i>ovector</i> that is passed to
1565 <b>pcre_exec()</b> is not big enough to remember the referenced substrings, PCRE
1566 gets a block of memory at the start of matching to use for this purpose. If the
1567 call via <b>pcre_malloc()</b> fails, this error is given. The memory is
1568 automatically freed at the end of matching.
1569 <pre>
1571 </pre>
1572 This error is used by the <b>pcre_copy_substring()</b>,
1573 <b>pcre_get_substring()</b>, and <b>pcre_get_substring_list()</b> functions (see
1574 below). It is never returned by <b>pcre_exec()</b>.
1575 <pre>
1577 </pre>
1578 The backtracking limit, as specified by the <i>match_limit</i> field in a
1579 <b>pcre_extra</b> structure (or defaulted) was reached. See the description
1580 above.
1581 <pre>
1583 </pre>
1584 This error is never generated by <b>pcre_exec()</b> itself. It is provided for
1585 use by callout functions that want to yield a distinctive error code. See the
1586 <a href="pcrecallout.html"><b>pcrecallout</b></a>
1587 documentation for details.
1588 <pre>
1590 </pre>
1591 A string that contains an invalid UTF-8 byte sequence was passed as a subject.
1592 <pre>
1594 </pre>
1595 The UTF-8 byte sequence that was passed as a subject was valid, but the value
1596 of <i>startoffset</i> did not point to the beginning of a UTF-8 character.
1597 <pre>
1599 </pre>
1600 The subject string did not match, but it did match partially. See the
1601 <a href="pcrepartial.html"><b>pcrepartial</b></a>
1602 documentation for details of partial matching.
1603 <pre>
1605 </pre>
1606 This code is no longer in use. It was formerly returned when the PCRE_PARTIAL
1607 option was used with a compiled pattern containing items that were not
1608 supported for partial matching. From release 8.00 onwards, there are no
1609 restrictions on partial matching.
1610 <pre>
1612 </pre>
1613 An unexpected internal error has occurred. This error could be caused by a bug
1614 in PCRE or by overwriting of the compiled pattern.
1615 <pre>
1617 </pre>
1618 This error is given if the value of the <i>ovecsize</i> argument is negative.
1619 <pre>
1621 </pre>
1622 The internal recursion limit, as specified by the <i>match_limit_recursion</i>
1623 field in a <b>pcre_extra</b> structure (or defaulted) was reached. See the
1624 description above.
1625 <pre>
1627 </pre>
1628 An invalid combination of PCRE_NEWLINE_<i>xxx</i> options was given.
1629 </P>
1630 <P>
1631 Error numbers -16 to -20 and -22 are not used by <b>pcre_exec()</b>.
1632 </P>
1633 <br><a name="SEC15" href="#TOC1">EXTRACTING CAPTURED SUBSTRINGS BY NUMBER</a><br>
1634 <P>
1635 <b>int pcre_copy_substring(const char *<i>subject</i>, int *<i>ovector</i>,</b>
1636 <b>int <i>stringcount</i>, int <i>stringnumber</i>, char *<i>buffer</i>,</b>
1637 <b>int <i>buffersize</i>);</b>
1638 </P>
1639 <P>
1640 <b>int pcre_get_substring(const char *<i>subject</i>, int *<i>ovector</i>,</b>
1641 <b>int <i>stringcount</i>, int <i>stringnumber</i>,</b>
1642 <b>const char **<i>stringptr</i>);</b>
1643 </P>
1644 <P>
1645 <b>int pcre_get_substring_list(const char *<i>subject</i>,</b>
1646 <b>int *<i>ovector</i>, int <i>stringcount</i>, const char ***<i>listptr</i>);</b>
1647 </P>
1648 <P>
1649 Captured substrings can be accessed directly by using the offsets returned by
1650 <b>pcre_exec()</b> in <i>ovector</i>. For convenience, the functions
1651 <b>pcre_copy_substring()</b>, <b>pcre_get_substring()</b>, and
1652 <b>pcre_get_substring_list()</b> are provided for extracting captured substrings
1653 as new, separate, zero-terminated strings. These functions identify substrings
1654 by number. The next section describes functions for extracting named
1655 substrings.
1656 </P>
1657 <P>
1658 A substring that contains a binary zero is correctly extracted and has a
1659 further zero added on the end, but the result is not, of course, a C string.
1660 However, you can process such a string by referring to the length that is
1661 returned by <b>pcre_copy_substring()</b> and <b>pcre_get_substring()</b>.
1662 Unfortunately, the interface to <b>pcre_get_substring_list()</b> is not adequate
1663 for handling strings containing binary zeros, because the end of the final
1664 string is not independently indicated.
1665 </P>
1666 <P>
1667 The first three arguments are the same for all three of these functions:
1668 <i>subject</i> is the subject string that has just been successfully matched,
1669 <i>ovector</i> is a pointer to the vector of integer offsets that was passed to
1670 <b>pcre_exec()</b>, and <i>stringcount</i> is the number of substrings that were
1671 captured by the match, including the substring that matched the entire regular
1672 expression. This is the value returned by <b>pcre_exec()</b> if it is greater
1673 than zero. If <b>pcre_exec()</b> returned zero, indicating that it ran out of
1674 space in <i>ovector</i>, the value passed as <i>stringcount</i> should be the
1675 number of elements in the vector divided by three.
1676 </P>
1677 <P>
1678 The functions <b>pcre_copy_substring()</b> and <b>pcre_get_substring()</b>
1679 extract a single substring, whose number is given as <i>stringnumber</i>. A
1680 value of zero extracts the substring that matched the entire pattern, whereas
1681 higher values extract the captured substrings. For <b>pcre_copy_substring()</b>,
1682 the string is placed in <i>buffer</i>, whose length is given by
1683 <i>buffersize</i>, while for <b>pcre_get_substring()</b> a new block of memory is
1684 obtained via <b>pcre_malloc</b>, and its address is returned via
1685 <i>stringptr</i>. The yield of the function is the length of the string, not
1686 including the terminating zero, or one of these error codes:
1687 <pre>
1689 </pre>
1690 The buffer was too small for <b>pcre_copy_substring()</b>, or the attempt to get
1691 memory failed for <b>pcre_get_substring()</b>.
1692 <pre>
1694 </pre>
1695 There is no substring whose number is <i>stringnumber</i>.
1696 </P>
1697 <P>
1698 The <b>pcre_get_substring_list()</b> function extracts all available substrings
1699 and builds a list of pointers to them. All this is done in a single block of
1700 memory that is obtained via <b>pcre_malloc</b>. The address of the memory block
1701 is returned via <i>listptr</i>, which is also the start of the list of string
1702 pointers. The end of the list is marked by a NULL pointer. The yield of the
1703 function is zero if all went well, or the error code
1704 <pre>
1706 </pre>
1707 if the attempt to get the memory block failed.
1708 </P>
1709 <P>
1710 When any of these functions encounter a substring that is unset, which can
1711 happen when capturing subpattern number <i>n+1</i> matches some part of the
1712 subject, but subpattern <i>n</i> has not been used at all, they return an empty
1713 string. This can be distinguished from a genuine zero-length substring by
1714 inspecting the appropriate offset in <i>ovector</i>, which is negative for unset
1715 substrings.
1716 </P>
1717 <P>
1718 The two convenience functions <b>pcre_free_substring()</b> and
1719 <b>pcre_free_substring_list()</b> can be used to free the memory returned by
1720 a previous call of <b>pcre_get_substring()</b> or
1721 <b>pcre_get_substring_list()</b>, respectively. They do nothing more than call
1722 the function pointed to by <b>pcre_free</b>, which of course could be called
1723 directly from a C program. However, PCRE is used in some situations where it is
1724 linked via a special interface to another programming language that cannot use
1725 <b>pcre_free</b> directly; it is for these cases that the functions are
1726 provided.
1727 </P>
1728 <br><a name="SEC16" href="#TOC1">EXTRACTING CAPTURED SUBSTRINGS BY NAME</a><br>
1729 <P>
1730 <b>int pcre_get_stringnumber(const pcre *<i>code</i>,</b>
1731 <b>const char *<i>name</i>);</b>
1732 </P>
1733 <P>
1734 <b>int pcre_copy_named_substring(const pcre *<i>code</i>,</b>
1735 <b>const char *<i>subject</i>, int *<i>ovector</i>,</b>
1736 <b>int <i>stringcount</i>, const char *<i>stringname</i>,</b>
1737 <b>char *<i>buffer</i>, int <i>buffersize</i>);</b>
1738 </P>
1739 <P>
1740 <b>int pcre_get_named_substring(const pcre *<i>code</i>,</b>
1741 <b>const char *<i>subject</i>, int *<i>ovector</i>,</b>
1742 <b>int <i>stringcount</i>, const char *<i>stringname</i>,</b>
1743 <b>const char **<i>stringptr</i>);</b>
1744 </P>
1745 <P>
1746 To extract a substring by name, you first have to find associated number.
1747 For example, for this pattern
1748 <pre>
1749 (a+)b(?&#60;xxx&#62;\d+)...
1750 </pre>
1751 the number of the subpattern called "xxx" is 2. If the name is known to be
1752 unique (PCRE_DUPNAMES was not set), you can find the number from the name by
1753 calling <b>pcre_get_stringnumber()</b>. The first argument is the compiled
1754 pattern, and the second is the name. The yield of the function is the
1755 subpattern number, or PCRE_ERROR_NOSUBSTRING (-7) if there is no subpattern of
1756 that name.
1757 </P>
1758 <P>
1759 Given the number, you can extract the substring directly, or use one of the
1760 functions described in the previous section. For convenience, there are also
1761 two functions that do the whole job.
1762 </P>
1763 <P>
1764 Most of the arguments of <b>pcre_copy_named_substring()</b> and
1765 <b>pcre_get_named_substring()</b> are the same as those for the similarly named
1766 functions that extract by number. As these are described in the previous
1767 section, they are not re-described here. There are just two differences:
1768 </P>
1769 <P>
1770 First, instead of a substring number, a substring name is given. Second, there
1771 is an extra argument, given at the start, which is a pointer to the compiled
1772 pattern. This is needed in order to gain access to the name-to-number
1773 translation table.
1774 </P>
1775 <P>
1776 These functions call <b>pcre_get_stringnumber()</b>, and if it succeeds, they
1777 then call <b>pcre_copy_substring()</b> or <b>pcre_get_substring()</b>, as
1778 appropriate. <b>NOTE:</b> If PCRE_DUPNAMES is set and there are duplicate names,
1779 the behaviour may not be what you want (see the next section).
1780 </P>
1781 <P>
1782 <b>Warning:</b> If the pattern uses the "(?|" feature to set up multiple
1783 subpatterns with the same number, you cannot use names to distinguish them,
1784 because names are not included in the compiled code. The matching process uses
1785 only numbers.
1786 </P>
1787 <br><a name="SEC17" href="#TOC1">DUPLICATE SUBPATTERN NAMES</a><br>
1788 <P>
1789 <b>int pcre_get_stringtable_entries(const pcre *<i>code</i>,</b>
1790 <b>const char *<i>name</i>, char **<i>first</i>, char **<i>last</i>);</b>
1791 </P>
1792 <P>
1793 When a pattern is compiled with the PCRE_DUPNAMES option, names for subpatterns
1794 are not required to be unique. Normally, patterns with duplicate names are such
1795 that in any one match, only one of the named subpatterns participates. An
1796 example is shown in the
1797 <a href="pcrepattern.html"><b>pcrepattern</b></a>
1798 documentation.
1799 </P>
1800 <P>
1801 When duplicates are present, <b>pcre_copy_named_substring()</b> and
1802 <b>pcre_get_named_substring()</b> return the first substring corresponding to
1803 the given name that is set. If none are set, PCRE_ERROR_NOSUBSTRING (-7) is
1804 returned; no data is returned. The <b>pcre_get_stringnumber()</b> function
1805 returns one of the numbers that are associated with the name, but it is not
1806 defined which it is.
1807 </P>
1808 <P>
1809 If you want to get full details of all captured substrings for a given name,
1810 you must use the <b>pcre_get_stringtable_entries()</b> function. The first
1811 argument is the compiled pattern, and the second is the name. The third and
1812 fourth are pointers to variables which are updated by the function. After it
1813 has run, they point to the first and last entries in the name-to-number table
1814 for the given name. The function itself returns the length of each entry, or
1815 PCRE_ERROR_NOSUBSTRING (-7) if there are none. The format of the table is
1816 described above in the section entitled <i>Information about a pattern</i>.
1817 Given all the relevant entries for the name, you can extract each of their
1818 numbers, and hence the captured data, if any.
1819 </P>
1820 <br><a name="SEC18" href="#TOC1">FINDING ALL POSSIBLE MATCHES</a><br>
1821 <P>
1822 The traditional matching function uses a similar algorithm to Perl, which stops
1823 when it finds the first match, starting at a given point in the subject. If you
1824 want to find all possible matches, or the longest possible match, consider
1825 using the alternative matching function (see below) instead. If you cannot use
1826 the alternative function, but still need to find all possible matches, you
1827 can kludge it up by making use of the callout facility, which is described in
1828 the
1829 <a href="pcrecallout.html"><b>pcrecallout</b></a>
1830 documentation.
1831 </P>
1832 <P>
1833 What you have to do is to insert a callout right at the end of the pattern.
1834 When your callout function is called, extract and save the current matched
1835 substring. Then return 1, which forces <b>pcre_exec()</b> to backtrack and try
1836 other alternatives. Ultimately, when it runs out of matches, <b>pcre_exec()</b>
1837 will yield PCRE_ERROR_NOMATCH.
1838 <a name="dfamatch"></a></P>
1839 <br><a name="SEC19" href="#TOC1">MATCHING A PATTERN: THE ALTERNATIVE FUNCTION</a><br>
1840 <P>
1841 <b>int pcre_dfa_exec(const pcre *<i>code</i>, const pcre_extra *<i>extra</i>,</b>
1842 <b>const char *<i>subject</i>, int <i>length</i>, int <i>startoffset</i>,</b>
1843 <b>int <i>options</i>, int *<i>ovector</i>, int <i>ovecsize</i>,</b>
1844 <b>int *<i>workspace</i>, int <i>wscount</i>);</b>
1845 </P>
1846 <P>
1847 The function <b>pcre_dfa_exec()</b> is called to match a subject string against
1848 a compiled pattern, using a matching algorithm that scans the subject string
1849 just once, and does not backtrack. This has different characteristics to the
1850 normal algorithm, and is not compatible with Perl. Some of the features of PCRE
1851 patterns are not supported. Nevertheless, there are times when this kind of
1852 matching can be useful. For a discussion of the two matching algorithms, and a
1853 list of features that <b>pcre_dfa_exec()</b> does not support, see the
1854 <a href="pcrematching.html"><b>pcrematching</b></a>
1855 documentation.
1856 </P>
1857 <P>
1858 The arguments for the <b>pcre_dfa_exec()</b> function are the same as for
1859 <b>pcre_exec()</b>, plus two extras. The <i>ovector</i> argument is used in a
1860 different way, and this is described below. The other common arguments are used
1861 in the same way as for <b>pcre_exec()</b>, so their description is not repeated
1862 here.
1863 </P>
1864 <P>
1865 The two additional arguments provide workspace for the function. The workspace
1866 vector should contain at least 20 elements. It is used for keeping track of
1867 multiple paths through the pattern tree. More workspace will be needed for
1868 patterns and subjects where there are a lot of potential matches.
1869 </P>
1870 <P>
1871 Here is an example of a simple call to <b>pcre_dfa_exec()</b>:
1872 <pre>
1873 int rc;
1874 int ovector[10];
1875 int wspace[20];
1876 rc = pcre_dfa_exec(
1877 re, /* result of pcre_compile() */
1878 NULL, /* we didn't study the pattern */
1879 "some string", /* the subject string */
1880 11, /* the length of the subject string */
1881 0, /* start at offset 0 in the subject */
1882 0, /* default options */
1883 ovector, /* vector of integers for substring information */
1884 10, /* number of elements (NOT size in bytes) */
1885 wspace, /* working space vector */
1886 20); /* number of elements (NOT size in bytes) */
1887 </PRE>
1888 </P>
1889 <br><b>
1890 Option bits for <b>pcre_dfa_exec()</b>
1891 </b><br>
1892 <P>
1893 The unused bits of the <i>options</i> argument for <b>pcre_dfa_exec()</b> must be
1894 zero. The only bits that may be set are PCRE_ANCHORED, PCRE_NEWLINE_<i>xxx</i>,
1897 and PCRE_DFA_RESTART. All but the last four of these are exactly the same as
1898 for <b>pcre_exec()</b>, so their description is not repeated here.
1899 <pre>
1902 </pre>
1903 These have the same general effect as they do for <b>pcre_exec()</b>, but the
1904 details are slightly different. When PCRE_PARTIAL_HARD is set for
1905 <b>pcre_dfa_exec()</b>, it returns PCRE_ERROR_PARTIAL if the end of the subject
1906 is reached and there is still at least one matching possibility that requires
1907 additional characters. This happens even if some complete matches have also
1908 been found. When PCRE_PARTIAL_SOFT is set, the return code PCRE_ERROR_NOMATCH
1909 is converted into PCRE_ERROR_PARTIAL if the end of the subject is reached,
1910 there have been no complete matches, but there is still at least one matching
1911 possibility. The portion of the string that was inspected when the longest
1912 partial match was found is set as the first matching string in both cases.
1913 <pre>
1915 </pre>
1916 Setting the PCRE_DFA_SHORTEST option causes the matching algorithm to stop as
1917 soon as it has found one match. Because of the way the alternative algorithm
1918 works, this is necessarily the shortest possible match at the first possible
1919 matching point in the subject string.
1920 <pre>
1922 </pre>
1923 When <b>pcre_dfa_exec()</b> returns a partial match, it is possible to call it
1924 again, with additional subject characters, and have it continue with the same
1925 match. The PCRE_DFA_RESTART option requests this action; when it is set, the
1926 <i>workspace</i> and <i>wscount</i> options must reference the same vector as
1927 before because data about the match so far is left in them after a partial
1928 match. There is more discussion of this facility in the
1929 <a href="pcrepartial.html"><b>pcrepartial</b></a>
1930 documentation.
1931 </P>
1932 <br><b>
1933 Successful returns from <b>pcre_dfa_exec()</b>
1934 </b><br>
1935 <P>
1936 When <b>pcre_dfa_exec()</b> succeeds, it may have matched more than one
1937 substring in the subject. Note, however, that all the matches from one run of
1938 the function start at the same point in the subject. The shorter matches are
1939 all initial substrings of the longer matches. For example, if the pattern
1940 <pre>
1941 &#60;.*&#62;
1942 </pre>
1943 is matched against the string
1944 <pre>
1945 This is &#60;something&#62; &#60;something else&#62; &#60;something further&#62; no more
1946 </pre>
1947 the three matched strings are
1948 <pre>
1949 &#60;something&#62;
1950 &#60;something&#62; &#60;something else&#62;
1951 &#60;something&#62; &#60;something else&#62; &#60;something further&#62;
1952 </pre>
1953 On success, the yield of the function is a number greater than zero, which is
1954 the number of matched substrings. The substrings themselves are returned in
1955 <i>ovector</i>. Each string uses two elements; the first is the offset to the
1956 start, and the second is the offset to the end. In fact, all the strings have
1957 the same start offset. (Space could have been saved by giving this only once,
1958 but it was decided to retain some compatibility with the way <b>pcre_exec()</b>
1959 returns data, even though the meaning of the strings is different.)
1960 </P>
1961 <P>
1962 The strings are returned in reverse order of length; that is, the longest
1963 matching string is given first. If there were too many matches to fit into
1964 <i>ovector</i>, the yield of the function is zero, and the vector is filled with
1965 the longest matches.
1966 </P>
1967 <br><b>
1968 Error returns from <b>pcre_dfa_exec()</b>
1969 </b><br>
1970 <P>
1971 The <b>pcre_dfa_exec()</b> function returns a negative number when it fails.
1972 Many of the errors are the same as for <b>pcre_exec()</b>, and these are
1973 described
1974 <a href="#errorlist">above.</a>
1975 There are in addition the following errors that are specific to
1976 <b>pcre_dfa_exec()</b>:
1977 <pre>
1979 </pre>
1980 This return is given if <b>pcre_dfa_exec()</b> encounters an item in the pattern
1981 that it does not support, for instance, the use of \C or a back reference.
1982 <pre>
1984 </pre>
1985 This return is given if <b>pcre_dfa_exec()</b> encounters a condition item that
1986 uses a back reference for the condition, or a test for recursion in a specific
1987 group. These are not supported.
1988 <pre>
1990 </pre>
1991 This return is given if <b>pcre_dfa_exec()</b> is called with an <i>extra</i>
1992 block that contains a setting of the <i>match_limit</i> field. This is not
1993 supported (it is meaningless).
1994 <pre>
1996 </pre>
1997 This return is given if <b>pcre_dfa_exec()</b> runs out of space in the
1998 <i>workspace</i> vector.
1999 <pre>
2001 </pre>
2002 When a recursive subpattern is processed, the matching function calls itself
2003 recursively, using private vectors for <i>ovector</i> and <i>workspace</i>. This
2004 error is given if the output vector is not large enough. This should be
2005 extremely rare, as a vector of size 1000 is used.
2006 </P>
2007 <br><a name="SEC20" href="#TOC1">SEE ALSO</a><br>
2008 <P>
2009 <b>pcrebuild</b>(3), <b>pcrecallout</b>(3), <b>pcrecpp(3)</b>(3),
2010 <b>pcrematching</b>(3), <b>pcrepartial</b>(3), <b>pcreposix</b>(3),
2011 <b>pcreprecompile</b>(3), <b>pcresample</b>(3), <b>pcrestack</b>(3).
2012 </P>
2013 <br><a name="SEC21" href="#TOC1">AUTHOR</a><br>
2014 <P>
2015 Philip Hazel
2016 <br>
2017 University Computing Service
2018 <br>
2019 Cambridge CB2 3QH, England.
2020 <br>
2021 </P>
2022 <br><a name="SEC22" href="#TOC1">REVISION</a><br>
2023 <P>
2024 Last updated: 22 September 2009
2025 <br>
2026 Copyright &copy; 1997-2009 University of Cambridge.
2027 <br>
2028 <p>
2029 Return to the <a href="index.html">PCRE index page</a>.
2030 </p>


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