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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 offset from the start of the pattern to the character
438 where the error was discovered is placed in the variable pointed to by
439 <i>erroffset</i>, which must not be NULL. If it is, an immediate error is given.
440 </P>
441 <P>
442 If <b>pcre_compile2()</b> is used instead of <b>pcre_compile()</b>, and the
443 <i>errorcodeptr</i> argument is not NULL, a non-zero error code number is
444 returned via this argument in the event of an error. This is in addition to the
445 textual error message. Error codes and messages are listed below.
446 </P>
447 <P>
448 If the final argument, <i>tableptr</i>, is NULL, PCRE uses a default set of
449 character tables that are built when PCRE is compiled, using the default C
450 locale. Otherwise, <i>tableptr</i> must be an address that is the result of a
451 call to <b>pcre_maketables()</b>. This value is stored with the compiled
452 pattern, and used again by <b>pcre_exec()</b>, unless another table pointer is
453 passed to it. For more discussion, see the section on locale support below.
454 </P>
455 <P>
456 This code fragment shows a typical straightforward call to <b>pcre_compile()</b>:
457 <pre>
458 pcre *re;
459 const char *error;
460 int erroffset;
461 re = pcre_compile(
462 "^A.*Z", /* the pattern */
463 0, /* default options */
464 &error, /* for error message */
465 &erroffset, /* for error offset */
466 NULL); /* use default character tables */
467 </pre>
468 The following names for option bits are defined in the <b>pcre.h</b> header
469 file:
470 <pre>
472 </pre>
473 If this bit is set, the pattern is forced to be "anchored", that is, it is
474 constrained to match only at the first matching point in the string that is
475 being searched (the "subject string"). This effect can also be achieved by
476 appropriate constructs in the pattern itself, which is the only way to do it in
477 Perl.
478 <pre>
480 </pre>
481 If this bit is set, <b>pcre_compile()</b> automatically inserts callout items,
482 all with number 255, before each pattern item. For discussion of the callout
483 facility, see the
484 <a href="pcrecallout.html"><b>pcrecallout</b></a>
485 documentation.
486 <pre>
489 </pre>
490 These options (which are mutually exclusive) control what the \R escape
491 sequence matches. The choice is either to match only CR, LF, or CRLF, or to
492 match any Unicode newline sequence. The default is specified when PCRE is
493 built. It can be overridden from within the pattern, or by setting an option
494 when a compiled pattern is matched.
495 <pre>
497 </pre>
498 If this bit is set, letters in the pattern match both upper and lower case
499 letters. It is equivalent to Perl's /i option, and it can be changed within a
500 pattern by a (?i) option setting. In UTF-8 mode, PCRE always understands the
501 concept of case for characters whose values are less than 128, so caseless
502 matching is always possible. For characters with higher values, the concept of
503 case is supported if PCRE is compiled with Unicode property support, but not
504 otherwise. If you want to use caseless matching for characters 128 and above,
505 you must ensure that PCRE is compiled with Unicode property support as well as
506 with UTF-8 support.
507 <pre>
509 </pre>
510 If this bit is set, a dollar metacharacter in the pattern matches only at the
511 end of the subject string. Without this option, a dollar also matches
512 immediately before a newline at the end of the string (but not before any other
513 newlines). The PCRE_DOLLAR_ENDONLY option is ignored if PCRE_MULTILINE is set.
514 There is no equivalent to this option in Perl, and no way to set it within a
515 pattern.
516 <pre>
518 </pre>
519 If this bit is set, a dot metacharater in the pattern matches all characters,
520 including those that indicate newline. Without it, a dot does not match when
521 the current position is at a newline. This option is equivalent to Perl's /s
522 option, and it can be changed within a pattern by a (?s) option setting. A
523 negative class such as [^a] always matches newline characters, independent of
524 the setting of this option.
525 <pre>
527 </pre>
528 If this bit is set, names used to identify capturing subpatterns need not be
529 unique. This can be helpful for certain types of pattern when it is known that
530 only one instance of the named subpattern can ever be matched. There are more
531 details of named subpatterns below; see also the
532 <a href="pcrepattern.html"><b>pcrepattern</b></a>
533 documentation.
534 <pre>
536 </pre>
537 If this bit is set, whitespace data characters in the pattern are totally
538 ignored except when escaped or inside a character class. Whitespace does not
539 include the VT character (code 11). In addition, characters between an
540 unescaped # outside a character class and the next newline, inclusive, are also
541 ignored. This is equivalent to Perl's /x option, and it can be changed within a
542 pattern by a (?x) option setting.
543 </P>
544 <P>
545 This option makes it possible to include comments inside complicated patterns.
546 Note, however, that this applies only to data characters. Whitespace characters
547 may never appear within special character sequences in a pattern, for example
548 within the sequence (?( which introduces a conditional subpattern.
549 <pre>
551 </pre>
552 This option was invented in order to turn on additional functionality of PCRE
553 that is incompatible with Perl, but it is currently of very little use. When
554 set, any backslash in a pattern that is followed by a letter that has no
555 special meaning causes an error, thus reserving these combinations for future
556 expansion. By default, as in Perl, a backslash followed by a letter with no
557 special meaning is treated as a literal. (Perl can, however, be persuaded to
558 give a warning for this.) There are at present no other features controlled by
559 this option. It can also be set by a (?X) option setting within a pattern.
560 <pre>
562 </pre>
563 If this option is set, an unanchored pattern is required to match before or at
564 the first newline in the subject string, though the matched text may continue
565 over the newline.
566 <pre>
568 </pre>
569 If this option is set, PCRE's behaviour is changed in some ways so that it is
570 compatible with JavaScript rather than Perl. The changes are as follows:
571 </P>
572 <P>
573 (1) A lone closing square bracket in a pattern causes a compile-time error,
574 because this is illegal in JavaScript (by default it is treated as a data
575 character). Thus, the pattern AB]CD becomes illegal when this option is set.
576 </P>
577 <P>
578 (2) At run time, a back reference to an unset subpattern group matches an empty
579 string (by default this causes the current matching alternative to fail). A
580 pattern such as (\1)(a) succeeds when this option is set (assuming it can find
581 an "a" in the subject), whereas it fails by default, for Perl compatibility.
582 <pre>
584 </pre>
585 By default, PCRE treats the subject string as consisting of a single line of
586 characters (even if it actually contains newlines). The "start of line"
587 metacharacter (^) matches only at the start of the string, while the "end of
588 line" metacharacter ($) matches only at the end of the string, or before a
589 terminating newline (unless PCRE_DOLLAR_ENDONLY is set). This is the same as
590 Perl.
591 </P>
592 <P>
593 When PCRE_MULTILINE it is set, the "start of line" and "end of line" constructs
594 match immediately following or immediately before internal newlines in the
595 subject string, respectively, as well as at the very start and end. This is
596 equivalent to Perl's /m option, and it can be changed within a pattern by a
597 (?m) option setting. If there are no newlines in a subject string, or no
598 occurrences of ^ or $ in a pattern, setting PCRE_MULTILINE has no effect.
599 <pre>
605 </pre>
606 These options override the default newline definition that was chosen when PCRE
607 was built. Setting the first or the second specifies that a newline is
608 indicated by a single character (CR or LF, respectively). Setting
609 PCRE_NEWLINE_CRLF specifies that a newline is indicated by the two-character
610 CRLF sequence. Setting PCRE_NEWLINE_ANYCRLF specifies that any of the three
611 preceding sequences should be recognized. Setting PCRE_NEWLINE_ANY specifies
612 that any Unicode newline sequence should be recognized. The Unicode newline
613 sequences are the three just mentioned, plus the single characters VT (vertical
614 tab, U+000B), FF (formfeed, U+000C), NEL (next line, U+0085), LS (line
615 separator, U+2028), and PS (paragraph separator, U+2029). The last two are
616 recognized only in UTF-8 mode.
617 </P>
618 <P>
619 The newline setting in the options word uses three bits that are treated
620 as a number, giving eight possibilities. Currently only six are used (default
621 plus the five values above). This means that if you set more than one newline
622 option, the combination may or may not be sensible. For example,
624 other combinations may yield unused numbers and cause an error.
625 </P>
626 <P>
627 The only time that a line break is specially recognized when compiling a
628 pattern is if PCRE_EXTENDED is set, and an unescaped # outside a character
629 class is encountered. This indicates a comment that lasts until after the next
630 line break sequence. In other circumstances, line break sequences are treated
631 as literal data, except that in PCRE_EXTENDED mode, both CR and LF are treated
632 as whitespace characters and are therefore ignored.
633 </P>
634 <P>
635 The newline option that is set at compile time becomes the default that is used
636 for <b>pcre_exec()</b> and <b>pcre_dfa_exec()</b>, but it can be overridden.
637 <pre>
639 </pre>
640 If this option is set, it disables the use of numbered capturing parentheses in
641 the pattern. Any opening parenthesis that is not followed by ? behaves as if it
642 were followed by ?: but named parentheses can still be used for capturing (and
643 they acquire numbers in the usual way). There is no equivalent of this option
644 in Perl.
645 <pre>
647 </pre>
648 This option inverts the "greediness" of the quantifiers so that they are not
649 greedy by default, but become greedy if followed by "?". It is not compatible
650 with Perl. It can also be set by a (?U) option setting within the pattern.
651 <pre>
653 </pre>
654 This option causes PCRE to regard both the pattern and the subject as strings
655 of UTF-8 characters instead of single-byte character strings. However, it is
656 available only when PCRE is built to include UTF-8 support. If not, the use
657 of this option provokes an error. Details of how this option changes the
658 behaviour of PCRE are given in the
659 <a href="pcre.html#utf8support">section on UTF-8 support</a>
660 in the main
661 <a href="pcre.html"><b>pcre</b></a>
662 page.
663 <pre>
665 </pre>
666 When PCRE_UTF8 is set, the validity of the pattern as a UTF-8 string is
667 automatically checked. There is a discussion about the
668 <a href="pcre.html#utf8strings">validity of UTF-8 strings</a>
669 in the main
670 <a href="pcre.html"><b>pcre</b></a>
671 page. If an invalid UTF-8 sequence of bytes is found, <b>pcre_compile()</b>
672 returns an error. If you already know that your pattern is valid, and you want
673 to skip this check for performance reasons, you can set the PCRE_NO_UTF8_CHECK
674 option. When it is set, the effect of passing an invalid UTF-8 string as a
675 pattern is undefined. It may cause your program to crash. Note that this option
676 can also be passed to <b>pcre_exec()</b> and <b>pcre_dfa_exec()</b>, to suppress
677 the UTF-8 validity checking of subject strings.
678 </P>
679 <br><a name="SEC8" href="#TOC1">COMPILATION ERROR CODES</a><br>
680 <P>
681 The following table lists the error codes than may be returned by
682 <b>pcre_compile2()</b>, along with the error messages that may be returned by
683 both compiling functions. As PCRE has developed, some error codes have fallen
684 out of use. To avoid confusion, they have not been re-used.
685 <pre>
686 0 no error
687 1 \ at end of pattern
688 2 \c at end of pattern
689 3 unrecognized character follows \
690 4 numbers out of order in {} quantifier
691 5 number too big in {} quantifier
692 6 missing terminating ] for character class
693 7 invalid escape sequence in character class
694 8 range out of order in character class
695 9 nothing to repeat
696 10 [this code is not in use]
697 11 internal error: unexpected repeat
698 12 unrecognized character after (? or (?-
699 13 POSIX named classes are supported only within a class
700 14 missing )
701 15 reference to non-existent subpattern
702 16 erroffset passed as NULL
703 17 unknown option bit(s) set
704 18 missing ) after comment
705 19 [this code is not in use]
706 20 regular expression is too large
707 21 failed to get memory
708 22 unmatched parentheses
709 23 internal error: code overflow
710 24 unrecognized character after (?&#60;
711 25 lookbehind assertion is not fixed length
712 26 malformed number or name after (?(
713 27 conditional group contains more than two branches
714 28 assertion expected after (?(
715 29 (?R or (?[+-]digits must be followed by )
716 30 unknown POSIX class name
717 31 POSIX collating elements are not supported
718 32 this version of PCRE is not compiled with PCRE_UTF8 support
719 33 [this code is not in use]
720 34 character value in \x{...} sequence is too large
721 35 invalid condition (?(0)
722 36 \C not allowed in lookbehind assertion
723 37 PCRE does not support \L, \l, \N, \U, or \u
724 38 number after (?C is &#62; 255
725 39 closing ) for (?C expected
726 40 recursive call could loop indefinitely
727 41 unrecognized character after (?P
728 42 syntax error in subpattern name (missing terminator)
729 43 two named subpatterns have the same name
730 44 invalid UTF-8 string
731 45 support for \P, \p, and \X has not been compiled
732 46 malformed \P or \p sequence
733 47 unknown property name after \P or \p
734 48 subpattern name is too long (maximum 32 characters)
735 49 too many named subpatterns (maximum 10000)
736 50 [this code is not in use]
737 51 octal value is greater than \377 (not in UTF-8 mode)
738 52 internal error: overran compiling workspace
739 53 internal error: previously-checked referenced subpattern not found
740 54 DEFINE group contains more than one branch
741 55 repeating a DEFINE group is not allowed
742 56 inconsistent NEWLINE options
743 57 \g is not followed by a braced, angle-bracketed, or quoted
744 name/number or by a plain number
745 58 a numbered reference must not be zero
746 59 (*VERB) with an argument is not supported
747 60 (*VERB) not recognized
748 61 number is too big
749 62 subpattern name expected
750 63 digit expected after (?+
751 64 ] is an invalid data character in JavaScript compatibility mode
752 </pre>
753 The numbers 32 and 10000 in errors 48 and 49 are defaults; different values may
754 be used if the limits were changed when PCRE was built.
755 </P>
756 <br><a name="SEC9" href="#TOC1">STUDYING A PATTERN</a><br>
757 <P>
758 <b>pcre_extra *pcre_study(const pcre *<i>code</i>, int <i>options</i></b>
759 <b>const char **<i>errptr</i>);</b>
760 </P>
761 <P>
762 If a compiled pattern is going to be used several times, it is worth spending
763 more time analyzing it in order to speed up the time taken for matching. The
764 function <b>pcre_study()</b> takes a pointer to a compiled pattern as its first
765 argument. If studying the pattern produces additional information that will
766 help speed up matching, <b>pcre_study()</b> returns a pointer to a
767 <b>pcre_extra</b> block, in which the <i>study_data</i> field points to the
768 results of the study.
769 </P>
770 <P>
771 The returned value from <b>pcre_study()</b> can be passed directly to
772 <b>pcre_exec()</b>. However, a <b>pcre_extra</b> block also contains other
773 fields that can be set by the caller before the block is passed; these are
774 described
775 <a href="#extradata">below</a>
776 in the section on matching a pattern.
777 </P>
778 <P>
779 If studying the pattern does not produce any additional information
780 <b>pcre_study()</b> returns NULL. In that circumstance, if the calling program
781 wants to pass any of the other fields to <b>pcre_exec()</b>, it must set up its
782 own <b>pcre_extra</b> block.
783 </P>
784 <P>
785 The second argument of <b>pcre_study()</b> contains option bits. At present, no
786 options are defined, and this argument should always be zero.
787 </P>
788 <P>
789 The third argument for <b>pcre_study()</b> is a pointer for an error message. If
790 studying succeeds (even if no data is returned), the variable it points to is
791 set to NULL. Otherwise it is set to point to a textual error message. This is a
792 static string that is part of the library. You must not try to free it. You
793 should test the error pointer for NULL after calling <b>pcre_study()</b>, to be
794 sure that it has run successfully.
795 </P>
796 <P>
797 This is a typical call to <b>pcre_study</b>():
798 <pre>
799 pcre_extra *pe;
800 pe = pcre_study(
801 re, /* result of pcre_compile() */
802 0, /* no options exist */
803 &error); /* set to NULL or points to a message */
804 </pre>
805 At present, studying a pattern is useful only for non-anchored patterns that do
806 not have a single fixed starting character. A bitmap of possible starting
807 bytes is created.
808 <a name="localesupport"></a></P>
809 <br><a name="SEC10" href="#TOC1">LOCALE SUPPORT</a><br>
810 <P>
811 PCRE handles caseless matching, and determines whether characters are letters,
812 digits, or whatever, by reference to a set of tables, indexed by character
813 value. When running in UTF-8 mode, this applies only to characters with codes
814 less than 128. Higher-valued codes never match escapes such as \w or \d, but
815 can be tested with \p if PCRE is built with Unicode character property
816 support. The use of locales with Unicode is discouraged. If you are handling
817 characters with codes greater than 128, you should either use UTF-8 and
818 Unicode, or use locales, but not try to mix the two.
819 </P>
820 <P>
821 PCRE contains an internal set of tables that are used when the final argument
822 of <b>pcre_compile()</b> is NULL. These are sufficient for many applications.
823 Normally, the internal tables recognize only ASCII characters. However, when
824 PCRE is built, it is possible to cause the internal tables to be rebuilt in the
825 default "C" locale of the local system, which may cause them to be different.
826 </P>
827 <P>
828 The internal tables can always be overridden by tables supplied by the
829 application that calls PCRE. These may be created in a different locale from
830 the default. As more and more applications change to using Unicode, the need
831 for this locale support is expected to die away.
832 </P>
833 <P>
834 External tables are built by calling the <b>pcre_maketables()</b> function,
835 which has no arguments, in the relevant locale. The result can then be passed
836 to <b>pcre_compile()</b> or <b>pcre_exec()</b> as often as necessary. For
837 example, to build and use tables that are appropriate for the French locale
838 (where accented characters with values greater than 128 are treated as letters),
839 the following code could be used:
840 <pre>
841 setlocale(LC_CTYPE, "fr_FR");
842 tables = pcre_maketables();
843 re = pcre_compile(..., tables);
844 </pre>
845 The locale name "fr_FR" is used on Linux and other Unix-like systems; if you
846 are using Windows, the name for the French locale is "french".
847 </P>
848 <P>
849 When <b>pcre_maketables()</b> runs, the tables are built in memory that is
850 obtained via <b>pcre_malloc</b>. It is the caller's responsibility to ensure
851 that the memory containing the tables remains available for as long as it is
852 needed.
853 </P>
854 <P>
855 The pointer that is passed to <b>pcre_compile()</b> is saved with the compiled
856 pattern, and the same tables are used via this pointer by <b>pcre_study()</b>
857 and normally also by <b>pcre_exec()</b>. Thus, by default, for any single
858 pattern, compilation, studying and matching all happen in the same locale, but
859 different patterns can be compiled in different locales.
860 </P>
861 <P>
862 It is possible to pass a table pointer or NULL (indicating the use of the
863 internal tables) to <b>pcre_exec()</b>. Although not intended for this purpose,
864 this facility could be used to match a pattern in a different locale from the
865 one in which it was compiled. Passing table pointers at run time is discussed
866 below in the section on matching a pattern.
867 </P>
868 <br><a name="SEC11" href="#TOC1">INFORMATION ABOUT A PATTERN</a><br>
869 <P>
870 <b>int pcre_fullinfo(const pcre *<i>code</i>, const pcre_extra *<i>extra</i>,</b>
871 <b>int <i>what</i>, void *<i>where</i>);</b>
872 </P>
873 <P>
874 The <b>pcre_fullinfo()</b> function returns information about a compiled
875 pattern. It replaces the obsolete <b>pcre_info()</b> function, which is
876 nevertheless retained for backwards compability (and is documented below).
877 </P>
878 <P>
879 The first argument for <b>pcre_fullinfo()</b> is a pointer to the compiled
880 pattern. The second argument is the result of <b>pcre_study()</b>, or NULL if
881 the pattern was not studied. The third argument specifies which piece of
882 information is required, and the fourth argument is a pointer to a variable
883 to receive the data. The yield of the function is zero for success, or one of
884 the following negative numbers:
885 <pre>
886 PCRE_ERROR_NULL the argument <i>code</i> was NULL
887 the argument <i>where</i> was NULL
888 PCRE_ERROR_BADMAGIC the "magic number" was not found
889 PCRE_ERROR_BADOPTION the value of <i>what</i> was invalid
890 </pre>
891 The "magic number" is placed at the start of each compiled pattern as an simple
892 check against passing an arbitrary memory pointer. Here is a typical call of
893 <b>pcre_fullinfo()</b>, to obtain the length of the compiled pattern:
894 <pre>
895 int rc;
896 size_t length;
897 rc = pcre_fullinfo(
898 re, /* result of pcre_compile() */
899 pe, /* result of pcre_study(), or NULL */
900 PCRE_INFO_SIZE, /* what is required */
901 &length); /* where to put the data */
902 </pre>
903 The possible values for the third argument are defined in <b>pcre.h</b>, and are
904 as follows:
905 <pre>
907 </pre>
908 Return the number of the highest back reference in the pattern. The fourth
909 argument should point to an <b>int</b> variable. Zero is returned if there are
910 no back references.
911 <pre>
913 </pre>
914 Return the number of capturing subpatterns in the pattern. The fourth argument
915 should point to an <b>int</b> variable.
916 <pre>
918 </pre>
919 Return a pointer to the internal default character tables within PCRE. The
920 fourth argument should point to an <b>unsigned char *</b> variable. This
921 information call is provided for internal use by the <b>pcre_study()</b>
922 function. External callers can cause PCRE to use its internal tables by passing
923 a NULL table pointer.
924 <pre>
926 </pre>
927 Return information about the first byte of any matched string, for a
928 non-anchored pattern. The fourth argument should point to an <b>int</b>
929 variable. (This option used to be called PCRE_INFO_FIRSTCHAR; the old name is
930 still recognized for backwards compatibility.)
931 </P>
932 <P>
933 If there is a fixed first byte, for example, from a pattern such as
934 (cat|cow|coyote), its value is returned. Otherwise, if either
935 <br>
936 <br>
937 (a) the pattern was compiled with the PCRE_MULTILINE option, and every branch
938 starts with "^", or
939 <br>
940 <br>
941 (b) every branch of the pattern starts with ".*" and PCRE_DOTALL is not set
942 (if it were set, the pattern would be anchored),
943 <br>
944 <br>
945 -1 is returned, indicating that the pattern matches only at the start of a
946 subject string or after any newline within the string. Otherwise -2 is
947 returned. For anchored patterns, -2 is returned.
948 <pre>
950 </pre>
951 If the pattern was studied, and this resulted in the construction of a 256-bit
952 table indicating a fixed set of bytes for the first byte in any matching
953 string, a pointer to the table is returned. Otherwise NULL is returned. The
954 fourth argument should point to an <b>unsigned char *</b> variable.
955 <pre>
957 </pre>
958 Return 1 if the pattern contains any explicit matches for CR or LF characters,
959 otherwise 0. The fourth argument should point to an <b>int</b> variable. An
960 explicit match is either a literal CR or LF character, or \r or \n.
961 <pre>
963 </pre>
964 Return 1 if the (?J) or (?-J) option setting is used in the pattern, otherwise
965 0. The fourth argument should point to an <b>int</b> variable. (?J) and
966 (?-J) set and unset the local PCRE_DUPNAMES option, respectively.
967 <pre>
969 </pre>
970 Return the value of the rightmost literal byte that must exist in any matched
971 string, other than at its start, if such a byte has been recorded. The fourth
972 argument should point to an <b>int</b> variable. If there is no such byte, -1 is
973 returned. For anchored patterns, a last literal byte is recorded only if it
974 follows something of variable length. For example, for the pattern
975 /^a\d+z\d+/ the returned value is "z", but for /^a\dz\d/ the returned value
976 is -1.
977 <pre>
981 </pre>
982 PCRE supports the use of named as well as numbered capturing parentheses. The
983 names are just an additional way of identifying the parentheses, which still
984 acquire numbers. Several convenience functions such as
985 <b>pcre_get_named_substring()</b> are provided for extracting captured
986 substrings by name. It is also possible to extract the data directly, by first
987 converting the name to a number in order to access the correct pointers in the
988 output vector (described with <b>pcre_exec()</b> below). To do the conversion,
989 you need to use the name-to-number map, which is described by these three
990 values.
991 </P>
992 <P>
993 The map consists of a number of fixed-size entries. PCRE_INFO_NAMECOUNT gives
994 the number of entries, and PCRE_INFO_NAMEENTRYSIZE gives the size of each
995 entry; both of these return an <b>int</b> value. The entry size depends on the
996 length of the longest name. PCRE_INFO_NAMETABLE returns a pointer to the first
997 entry of the table (a pointer to <b>char</b>). The first two bytes of each entry
998 are the number of the capturing parenthesis, most significant byte first. The
999 rest of the entry is the corresponding name, zero terminated. The names are in
1000 alphabetical order. When PCRE_DUPNAMES is set, duplicate names are in order of
1001 their parentheses numbers. For example, consider the following pattern (assume
1002 PCRE_EXTENDED is set, so white space - including newlines - is ignored):
1003 <pre>
1004 (?&#60;date&#62; (?&#60;year&#62;(\d\d)?\d\d) - (?&#60;month&#62;\d\d) - (?&#60;day&#62;\d\d) )
1005 </pre>
1006 There are four named subpatterns, so the table has four entries, and each entry
1007 in the table is eight bytes long. The table is as follows, with non-printing
1008 bytes shows in hexadecimal, and undefined bytes shown as ??:
1009 <pre>
1010 00 01 d a t e 00 ??
1011 00 05 d a y 00 ?? ??
1012 00 04 m o n t h 00
1013 00 02 y e a r 00 ??
1014 </pre>
1015 When writing code to extract data from named subpatterns using the
1016 name-to-number map, remember that the length of the entries is likely to be
1017 different for each compiled pattern.
1018 <pre>
1020 </pre>
1021 Return 1 if the pattern can be used for partial matching with
1022 <b>pcre_exec()</b>, otherwise 0. The fourth argument should point to an
1023 <b>int</b> variable. From release 8.00, this always returns 1, because the
1024 restrictions that previously applied to partial matching have been lifted. The
1025 <a href="pcrepartial.html"><b>pcrepartial</b></a>
1026 documentation gives details of partial matching.
1027 <pre>
1029 </pre>
1030 Return a copy of the options with which the pattern was compiled. The fourth
1031 argument should point to an <b>unsigned long int</b> variable. These option bits
1032 are those specified in the call to <b>pcre_compile()</b>, modified by any
1033 top-level option settings at the start of the pattern itself. In other words,
1034 they are the options that will be in force when matching starts. For example,
1035 if the pattern /(?im)abc(?-i)d/ is compiled with the PCRE_EXTENDED option, the
1037 </P>
1038 <P>
1039 A pattern is automatically anchored by PCRE if all of its top-level
1040 alternatives begin with one of the following:
1041 <pre>
1042 ^ unless PCRE_MULTILINE is set
1043 \A always
1044 \G always
1045 .* if PCRE_DOTALL is set and there are no back references to the subpattern in which .* appears
1046 </pre>
1047 For such patterns, the PCRE_ANCHORED bit is set in the options returned by
1048 <b>pcre_fullinfo()</b>.
1049 <pre>
1051 </pre>
1052 Return the size of the compiled pattern, that is, the value that was passed as
1053 the argument to <b>pcre_malloc()</b> when PCRE was getting memory in which to
1054 place the compiled data. The fourth argument should point to a <b>size_t</b>
1055 variable.
1056 <pre>
1058 </pre>
1059 Return the size of the data block pointed to by the <i>study_data</i> field in
1060 a <b>pcre_extra</b> block. That is, it is the value that was passed to
1061 <b>pcre_malloc()</b> when PCRE was getting memory into which to place the data
1062 created by <b>pcre_study()</b>. The fourth argument should point to a
1063 <b>size_t</b> variable.
1064 </P>
1065 <br><a name="SEC12" href="#TOC1">OBSOLETE INFO FUNCTION</a><br>
1066 <P>
1067 <b>int pcre_info(const pcre *<i>code</i>, int *<i>optptr</i>, int</b>
1068 <b>*<i>firstcharptr</i>);</b>
1069 </P>
1070 <P>
1071 The <b>pcre_info()</b> function is now obsolete because its interface is too
1072 restrictive to return all the available data about a compiled pattern. New
1073 programs should use <b>pcre_fullinfo()</b> instead. The yield of
1074 <b>pcre_info()</b> is the number of capturing subpatterns, or one of the
1075 following negative numbers:
1076 <pre>
1077 PCRE_ERROR_NULL the argument <i>code</i> was NULL
1078 PCRE_ERROR_BADMAGIC the "magic number" was not found
1079 </pre>
1080 If the <i>optptr</i> argument is not NULL, a copy of the options with which the
1081 pattern was compiled is placed in the integer it points to (see
1082 PCRE_INFO_OPTIONS above).
1083 </P>
1084 <P>
1085 If the pattern is not anchored and the <i>firstcharptr</i> argument is not NULL,
1086 it is used to pass back information about the first character of any matched
1087 string (see PCRE_INFO_FIRSTBYTE above).
1088 </P>
1089 <br><a name="SEC13" href="#TOC1">REFERENCE COUNTS</a><br>
1090 <P>
1091 <b>int pcre_refcount(pcre *<i>code</i>, int <i>adjust</i>);</b>
1092 </P>
1093 <P>
1094 The <b>pcre_refcount()</b> function is used to maintain a reference count in the
1095 data block that contains a compiled pattern. It is provided for the benefit of
1096 applications that operate in an object-oriented manner, where different parts
1097 of the application may be using the same compiled pattern, but you want to free
1098 the block when they are all done.
1099 </P>
1100 <P>
1101 When a pattern is compiled, the reference count field is initialized to zero.
1102 It is changed only by calling this function, whose action is to add the
1103 <i>adjust</i> value (which may be positive or negative) to it. The yield of the
1104 function is the new value. However, the value of the count is constrained to
1105 lie between 0 and 65535, inclusive. If the new value is outside these limits,
1106 it is forced to the appropriate limit value.
1107 </P>
1108 <P>
1109 Except when it is zero, the reference count is not correctly preserved if a
1110 pattern is compiled on one host and then transferred to a host whose byte-order
1111 is different. (This seems a highly unlikely scenario.)
1112 </P>
1113 <br><a name="SEC14" href="#TOC1">MATCHING A PATTERN: THE TRADITIONAL FUNCTION</a><br>
1114 <P>
1115 <b>int pcre_exec(const pcre *<i>code</i>, const pcre_extra *<i>extra</i>,</b>
1116 <b>const char *<i>subject</i>, int <i>length</i>, int <i>startoffset</i>,</b>
1117 <b>int <i>options</i>, int *<i>ovector</i>, int <i>ovecsize</i>);</b>
1118 </P>
1119 <P>
1120 The function <b>pcre_exec()</b> is called to match a subject string against a
1121 compiled pattern, which is passed in the <i>code</i> argument. If the
1122 pattern has been studied, the result of the study should be passed in the
1123 <i>extra</i> argument. This function is the main matching facility of the
1124 library, and it operates in a Perl-like manner. For specialist use there is
1125 also an alternative matching function, which is described
1126 <a href="#dfamatch">below</a>
1127 in the section about the <b>pcre_dfa_exec()</b> function.
1128 </P>
1129 <P>
1130 In most applications, the pattern will have been compiled (and optionally
1131 studied) in the same process that calls <b>pcre_exec()</b>. However, it is
1132 possible to save compiled patterns and study data, and then use them later
1133 in different processes, possibly even on different hosts. For a discussion
1134 about this, see the
1135 <a href="pcreprecompile.html"><b>pcreprecompile</b></a>
1136 documentation.
1137 </P>
1138 <P>
1139 Here is an example of a simple call to <b>pcre_exec()</b>:
1140 <pre>
1141 int rc;
1142 int ovector[30];
1143 rc = pcre_exec(
1144 re, /* result of pcre_compile() */
1145 NULL, /* we didn't study the pattern */
1146 "some string", /* the subject string */
1147 11, /* the length of the subject string */
1148 0, /* start at offset 0 in the subject */
1149 0, /* default options */
1150 ovector, /* vector of integers for substring information */
1151 30); /* number of elements (NOT size in bytes) */
1152 <a name="extradata"></a></PRE>
1153 </P>
1154 <br><b>
1155 Extra data for <b>pcre_exec()</b>
1156 </b><br>
1157 <P>
1158 If the <i>extra</i> argument is not NULL, it must point to a <b>pcre_extra</b>
1159 data block. The <b>pcre_study()</b> function returns such a block (when it
1160 doesn't return NULL), but you can also create one for yourself, and pass
1161 additional information in it. The <b>pcre_extra</b> block contains the following
1162 fields (not necessarily in this order):
1163 <pre>
1164 unsigned long int <i>flags</i>;
1165 void *<i>study_data</i>;
1166 unsigned long int <i>match_limit</i>;
1167 unsigned long int <i>match_limit_recursion</i>;
1168 void *<i>callout_data</i>;
1169 const unsigned char *<i>tables</i>;
1170 </pre>
1171 The <i>flags</i> field is a bitmap that specifies which of the other fields
1172 are set. The flag bits are:
1173 <pre>
1179 </pre>
1180 Other flag bits should be set to zero. The <i>study_data</i> field is set in the
1181 <b>pcre_extra</b> block that is returned by <b>pcre_study()</b>, together with
1182 the appropriate flag bit. You should not set this yourself, but you may add to
1183 the block by setting the other fields and their corresponding flag bits.
1184 </P>
1185 <P>
1186 The <i>match_limit</i> field provides a means of preventing PCRE from using up a
1187 vast amount of resources when running patterns that are not going to match,
1188 but which have a very large number of possibilities in their search trees. The
1189 classic example is the use of nested unlimited repeats.
1190 </P>
1191 <P>
1192 Internally, PCRE uses a function called <b>match()</b> which it calls repeatedly
1193 (sometimes recursively). The limit set by <i>match_limit</i> is imposed on the
1194 number of times this function is called during a match, which has the effect of
1195 limiting the amount of backtracking that can take place. For patterns that are
1196 not anchored, the count restarts from zero for each position in the subject
1197 string.
1198 </P>
1199 <P>
1200 The default value for the limit can be set when PCRE is built; the default
1201 default is 10 million, which handles all but the most extreme cases. You can
1202 override the default by suppling <b>pcre_exec()</b> with a <b>pcre_extra</b>
1203 block in which <i>match_limit</i> is set, and PCRE_EXTRA_MATCH_LIMIT is set in
1204 the <i>flags</i> field. If the limit is exceeded, <b>pcre_exec()</b> returns
1206 </P>
1207 <P>
1208 The <i>match_limit_recursion</i> field is similar to <i>match_limit</i>, but
1209 instead of limiting the total number of times that <b>match()</b> is called, it
1210 limits the depth of recursion. The recursion depth is a smaller number than the
1211 total number of calls, because not all calls to <b>match()</b> are recursive.
1212 This limit is of use only if it is set smaller than <i>match_limit</i>.
1213 </P>
1214 <P>
1215 Limiting the recursion depth limits the amount of stack that can be used, or,
1216 when PCRE has been compiled to use memory on the heap instead of the stack, the
1217 amount of heap memory that can be used.
1218 </P>
1219 <P>
1220 The default value for <i>match_limit_recursion</i> can be set when PCRE is
1221 built; the default default is the same value as the default for
1222 <i>match_limit</i>. You can override the default by suppling <b>pcre_exec()</b>
1223 with a <b>pcre_extra</b> block in which <i>match_limit_recursion</i> is set, and
1224 PCRE_EXTRA_MATCH_LIMIT_RECURSION is set in the <i>flags</i> field. If the limit
1225 is exceeded, <b>pcre_exec()</b> returns PCRE_ERROR_RECURSIONLIMIT.
1226 </P>
1227 <P>
1228 The <i>callout_data</i> field is used in conjunction with the "callout" feature,
1229 and is described in the
1230 <a href="pcrecallout.html"><b>pcrecallout</b></a>
1231 documentation.
1232 </P>
1233 <P>
1234 The <i>tables</i> field is used to pass a character tables pointer to
1235 <b>pcre_exec()</b>; this overrides the value that is stored with the compiled
1236 pattern. A non-NULL value is stored with the compiled pattern only if custom
1237 tables were supplied to <b>pcre_compile()</b> via its <i>tableptr</i> argument.
1238 If NULL is passed to <b>pcre_exec()</b> using this mechanism, it forces PCRE's
1239 internal tables to be used. This facility is helpful when re-using patterns
1240 that have been saved after compiling with an external set of tables, because
1241 the external tables might be at a different address when <b>pcre_exec()</b> is
1242 called. See the
1243 <a href="pcreprecompile.html"><b>pcreprecompile</b></a>
1244 documentation for a discussion of saving compiled patterns for later use.
1245 <a name="execoptions"></a></P>
1246 <br><b>
1247 Option bits for <b>pcre_exec()</b>
1248 </b><br>
1249 <P>
1250 The unused bits of the <i>options</i> argument for <b>pcre_exec()</b> must be
1251 zero. The only bits that may be set are PCRE_ANCHORED, PCRE_NEWLINE_<i>xxx</i>,
1255 <pre>
1257 </pre>
1258 The PCRE_ANCHORED option limits <b>pcre_exec()</b> to matching at the first
1259 matching position. If a pattern was compiled with PCRE_ANCHORED, or turned out
1260 to be anchored by virtue of its contents, it cannot be made unachored at
1261 matching time.
1262 <pre>
1265 </pre>
1266 These options (which are mutually exclusive) control what the \R escape
1267 sequence matches. The choice is either to match only CR, LF, or CRLF, or to
1268 match any Unicode newline sequence. These options override the choice that was
1269 made or defaulted when the pattern was compiled.
1270 <pre>
1276 </pre>
1277 These options override the newline definition that was chosen or defaulted when
1278 the pattern was compiled. For details, see the description of
1279 <b>pcre_compile()</b> above. During matching, the newline choice affects the
1280 behaviour of the dot, circumflex, and dollar metacharacters. It may also alter
1281 the way the match position is advanced after a match failure for an unanchored
1282 pattern.
1283 </P>
1284 <P>
1286 match attempt for an unanchored pattern fails when the current position is at a
1287 CRLF sequence, and the pattern contains no explicit matches for CR or LF
1288 characters, the match position is advanced by two characters instead of one, in
1289 other words, to after the CRLF.
1290 </P>
1291 <P>
1292 The above rule is a compromise that makes the most common cases work as
1293 expected. For example, if the pattern is .+A (and the PCRE_DOTALL option is not
1294 set), it does not match the string "\r\nA" because, after failing at the
1295 start, it skips both the CR and the LF before retrying. However, the pattern
1296 [\r\n]A does match that string, because it contains an explicit CR or LF
1297 reference, and so advances only by one character after the first failure.
1298 </P>
1299 <P>
1300 An explicit match for CR of LF is either a literal appearance of one of those
1301 characters, or one of the \r or \n escape sequences. Implicit matches such as
1302 [^X] do not count, nor does \s (which includes CR and LF in the characters
1303 that it matches).
1304 </P>
1305 <P>
1306 Notwithstanding the above, anomalous effects may still occur when CRLF is a
1307 valid newline sequence and explicit \r or \n escapes appear in the pattern.
1308 <pre>
1310 </pre>
1311 This option specifies that first character of the subject string is not the
1312 beginning of a line, so the circumflex metacharacter should not match before
1313 it. Setting this without PCRE_MULTILINE (at compile time) causes circumflex
1314 never to match. This option affects only the behaviour of the circumflex
1315 metacharacter. It does not affect \A.
1316 <pre>
1318 </pre>
1319 This option specifies that the end of the subject string is not the end of a
1320 line, so the dollar metacharacter should not match it nor (except in multiline
1321 mode) a newline immediately before it. Setting this without PCRE_MULTILINE (at
1322 compile time) causes dollar never to match. This option affects only the
1323 behaviour of the dollar metacharacter. It does not affect \Z or \z.
1324 <pre>
1326 </pre>
1327 An empty string is not considered to be a valid match if this option is set. If
1328 there are alternatives in the pattern, they are tried. If all the alternatives
1329 match the empty string, the entire match fails. For example, if the pattern
1330 <pre>
1331 a?b?
1332 </pre>
1333 is applied to a string not beginning with "a" or "b", it matches an empty
1334 string at the start of the subject. With PCRE_NOTEMPTY set, this match is not
1335 valid, so PCRE searches further into the string for occurrences of "a" or "b".
1336 <pre>
1338 </pre>
1339 This is like PCRE_NOTEMPTY, except that an empty string match that is not at
1340 the start of the subject is permitted. If the pattern is anchored, such a match
1341 can occur only if the pattern contains \K.
1342 </P>
1343 <P>
1344 Perl has no direct equivalent of PCRE_NOTEMPTY or PCRE_NOTEMPTY_ATSTART, but it
1345 does make a special case of a pattern match of the empty string within its
1346 <b>split()</b> function, and when using the /g modifier. It is possible to
1347 emulate Perl's behaviour after matching a null string by first trying the match
1348 again at the same offset with PCRE_NOTEMPTY_ATSTART and PCRE_ANCHORED, and then
1349 if that fails, by advancing the starting offset (see below) and trying an
1350 ordinary match again. There is some code that demonstrates how to do this in
1351 the
1352 <a href="pcredemo.html"><b>pcredemo</b></a>
1353 sample program.
1354 <pre>
1356 </pre>
1357 There are a number of optimizations that <b>pcre_exec()</b> uses at the start of
1358 a match, in order to speed up the process. For example, if it is known that a
1359 match must start with a specific character, it searches the subject for that
1360 character, and fails immediately if it cannot find it, without actually running
1361 the main matching function. When callouts are in use, these optimizations can
1362 cause them to be skipped. This option disables the "start-up" optimizations,
1363 causing performance to suffer, but ensuring that the callouts do occur.
1364 <pre>
1366 </pre>
1367 When PCRE_UTF8 is set at compile time, the validity of the subject as a UTF-8
1368 string is automatically checked when <b>pcre_exec()</b> is subsequently called.
1369 The value of <i>startoffset</i> is also checked to ensure that it points to the
1370 start of a UTF-8 character. There is a discussion about the validity of UTF-8
1371 strings in the
1372 <a href="pcre.html#utf8strings">section on UTF-8 support</a>
1373 in the main
1374 <a href="pcre.html"><b>pcre</b></a>
1375 page. If an invalid UTF-8 sequence of bytes is found, <b>pcre_exec()</b> returns
1376 the error PCRE_ERROR_BADUTF8. If <i>startoffset</i> contains an invalid value,
1377 PCRE_ERROR_BADUTF8_OFFSET is returned.
1378 </P>
1379 <P>
1380 If you already know that your subject is valid, and you want to skip these
1381 checks for performance reasons, you can set the PCRE_NO_UTF8_CHECK option when
1382 calling <b>pcre_exec()</b>. You might want to do this for the second and
1383 subsequent calls to <b>pcre_exec()</b> if you are making repeated calls to find
1384 all the matches in a single subject string. However, you should be sure that
1385 the value of <i>startoffset</i> points to the start of a UTF-8 character. When
1386 PCRE_NO_UTF8_CHECK is set, the effect of passing an invalid UTF-8 string as a
1387 subject, or a value of <i>startoffset</i> that does not point to the start of a
1388 UTF-8 character, is undefined. Your program may crash.
1389 <pre>
1392 </pre>
1393 These options turn on the partial matching feature. For backwards
1394 compatibility, PCRE_PARTIAL is a synonym for PCRE_PARTIAL_SOFT. A partial match
1395 occurs if the end of the subject string is reached successfully, but there are
1396 not enough subject characters to complete the match. If this happens when
1397 PCRE_PARTIAL_HARD is set, <b>pcre_exec()</b> immediately returns
1398 PCRE_ERROR_PARTIAL. Otherwise, if PCRE_PARTIAL_SOFT is set, matching continues
1399 by testing any other alternatives. Only if they all fail is PCRE_ERROR_PARTIAL
1400 returned (instead of PCRE_ERROR_NOMATCH). The portion of the string that
1401 was inspected when the partial match was found is set as the first matching
1402 string. There is a more detailed discussion in the
1403 <a href="pcrepartial.html"><b>pcrepartial</b></a>
1404 documentation.
1405 </P>
1406 <br><b>
1407 The string to be matched by <b>pcre_exec()</b>
1408 </b><br>
1409 <P>
1410 The subject string is passed to <b>pcre_exec()</b> as a pointer in
1411 <i>subject</i>, a length (in bytes) in <i>length</i>, and a starting byte offset
1412 in <i>startoffset</i>. In UTF-8 mode, the byte offset must point to the start of
1413 a UTF-8 character. Unlike the pattern string, the subject may contain binary
1414 zero bytes. When the starting offset is zero, the search for a match starts at
1415 the beginning of the subject, and this is by far the most common case.
1416 </P>
1417 <P>
1418 A non-zero starting offset is useful when searching for another match in the
1419 same subject by calling <b>pcre_exec()</b> again after a previous success.
1420 Setting <i>startoffset</i> differs from just passing over a shortened string and
1421 setting PCRE_NOTBOL in the case of a pattern that begins with any kind of
1422 lookbehind. For example, consider the pattern
1423 <pre>
1424 \Biss\B
1425 </pre>
1426 which finds occurrences of "iss" in the middle of words. (\B matches only if
1427 the current position in the subject is not a word boundary.) When applied to
1428 the string "Mississipi" the first call to <b>pcre_exec()</b> finds the first
1429 occurrence. If <b>pcre_exec()</b> is called again with just the remainder of the
1430 subject, namely "issipi", it does not match, because \B is always false at the
1431 start of the subject, which is deemed to be a word boundary. However, if
1432 <b>pcre_exec()</b> is passed the entire string again, but with <i>startoffset</i>
1433 set to 4, it finds the second occurrence of "iss" because it is able to look
1434 behind the starting point to discover that it is preceded by a letter.
1435 </P>
1436 <P>
1437 If a non-zero starting offset is passed when the pattern is anchored, one
1438 attempt to match at the given offset is made. This can only succeed if the
1439 pattern does not require the match to be at the start of the subject.
1440 </P>
1441 <br><b>
1442 How <b>pcre_exec()</b> returns captured substrings
1443 </b><br>
1444 <P>
1445 In general, a pattern matches a certain portion of the subject, and in
1446 addition, further substrings from the subject may be picked out by parts of the
1447 pattern. Following the usage in Jeffrey Friedl's book, this is called
1448 "capturing" in what follows, and the phrase "capturing subpattern" is used for
1449 a fragment of a pattern that picks out a substring. PCRE supports several other
1450 kinds of parenthesized subpattern that do not cause substrings to be captured.
1451 </P>
1452 <P>
1453 Captured substrings are returned to the caller via a vector of integers whose
1454 address is passed in <i>ovector</i>. The number of elements in the vector is
1455 passed in <i>ovecsize</i>, which must be a non-negative number. <b>Note</b>: this
1456 argument is NOT the size of <i>ovector</i> in bytes.
1457 </P>
1458 <P>
1459 The first two-thirds of the vector is used to pass back captured substrings,
1460 each substring using a pair of integers. The remaining third of the vector is
1461 used as workspace by <b>pcre_exec()</b> while matching capturing subpatterns,
1462 and is not available for passing back information. The number passed in
1463 <i>ovecsize</i> should always be a multiple of three. If it is not, it is
1464 rounded down.
1465 </P>
1466 <P>
1467 When a match is successful, information about captured substrings is returned
1468 in pairs of integers, starting at the beginning of <i>ovector</i>, and
1469 continuing up to two-thirds of its length at the most. The first element of
1470 each pair is set to the byte offset of the first character in a substring, and
1471 the second is set to the byte offset of the first character after the end of a
1472 substring. <b>Note</b>: these values are always byte offsets, even in UTF-8
1473 mode. They are not character counts.
1474 </P>
1475 <P>
1476 The first pair of integers, <i>ovector[0]</i> and <i>ovector[1]</i>, identify the
1477 portion of the subject string matched by the entire pattern. The next pair is
1478 used for the first capturing subpattern, and so on. The value returned by
1479 <b>pcre_exec()</b> is one more than the highest numbered pair that has been set.
1480 For example, if two substrings have been captured, the returned value is 3. If
1481 there are no capturing subpatterns, the return value from a successful match is
1482 1, indicating that just the first pair of offsets has been set.
1483 </P>
1484 <P>
1485 If a capturing subpattern is matched repeatedly, it is the last portion of the
1486 string that it matched that is returned.
1487 </P>
1488 <P>
1489 If the vector is too small to hold all the captured substring offsets, it is
1490 used as far as possible (up to two-thirds of its length), and the function
1491 returns a value of zero. If the substring offsets are not of interest,
1492 <b>pcre_exec()</b> may be called with <i>ovector</i> passed as NULL and
1493 <i>ovecsize</i> as zero. However, if the pattern contains back references and
1494 the <i>ovector</i> is not big enough to remember the related substrings, PCRE
1495 has to get additional memory for use during matching. Thus it is usually
1496 advisable to supply an <i>ovector</i>.
1497 </P>
1498 <P>
1499 The <b>pcre_info()</b> function can be used to find out how many capturing
1500 subpatterns there are in a compiled pattern. The smallest size for
1501 <i>ovector</i> that will allow for <i>n</i> captured substrings, in addition to
1502 the offsets of the substring matched by the whole pattern, is (<i>n</i>+1)*3.
1503 </P>
1504 <P>
1505 It is possible for capturing subpattern number <i>n+1</i> to match some part of
1506 the subject when subpattern <i>n</i> has not been used at all. For example, if
1507 the string "abc" is matched against the pattern (a|(z))(bc) the return from the
1508 function is 4, and subpatterns 1 and 3 are matched, but 2 is not. When this
1509 happens, both values in the offset pairs corresponding to unused subpatterns
1510 are set to -1.
1511 </P>
1512 <P>
1513 Offset values that correspond to unused subpatterns at the end of the
1514 expression are also set to -1. For example, if the string "abc" is matched
1515 against the pattern (abc)(x(yz)?)? subpatterns 2 and 3 are not matched. The
1516 return from the function is 2, because the highest used capturing subpattern
1517 number is 1. However, you can refer to the offsets for the second and third
1518 capturing subpatterns if you wish (assuming the vector is large enough, of
1519 course).
1520 </P>
1521 <P>
1522 Some convenience functions are provided for extracting the captured substrings
1523 as separate strings. These are described below.
1524 <a name="errorlist"></a></P>
1525 <br><b>
1526 Error return values from <b>pcre_exec()</b>
1527 </b><br>
1528 <P>
1529 If <b>pcre_exec()</b> fails, it returns a negative number. The following are
1530 defined in the header file:
1531 <pre>
1533 </pre>
1534 The subject string did not match the pattern.
1535 <pre>
1537 </pre>
1538 Either <i>code</i> or <i>subject</i> was passed as NULL, or <i>ovector</i> was
1539 NULL and <i>ovecsize</i> was not zero.
1540 <pre>
1542 </pre>
1543 An unrecognized bit was set in the <i>options</i> argument.
1544 <pre>
1546 </pre>
1547 PCRE stores a 4-byte "magic number" at the start of the compiled code, to catch
1548 the case when it is passed a junk pointer and to detect when a pattern that was
1549 compiled in an environment of one endianness is run in an environment with the
1550 other endianness. This is the error that PCRE gives when the magic number is
1551 not present.
1552 <pre>
1554 </pre>
1555 While running the pattern match, an unknown item was encountered in the
1556 compiled pattern. This error could be caused by a bug in PCRE or by overwriting
1557 of the compiled pattern.
1558 <pre>
1560 </pre>
1561 If a pattern contains back references, but the <i>ovector</i> that is passed to
1562 <b>pcre_exec()</b> is not big enough to remember the referenced substrings, PCRE
1563 gets a block of memory at the start of matching to use for this purpose. If the
1564 call via <b>pcre_malloc()</b> fails, this error is given. The memory is
1565 automatically freed at the end of matching.
1566 <pre>
1568 </pre>
1569 This error is used by the <b>pcre_copy_substring()</b>,
1570 <b>pcre_get_substring()</b>, and <b>pcre_get_substring_list()</b> functions (see
1571 below). It is never returned by <b>pcre_exec()</b>.
1572 <pre>
1574 </pre>
1575 The backtracking limit, as specified by the <i>match_limit</i> field in a
1576 <b>pcre_extra</b> structure (or defaulted) was reached. See the description
1577 above.
1578 <pre>
1580 </pre>
1581 This error is never generated by <b>pcre_exec()</b> itself. It is provided for
1582 use by callout functions that want to yield a distinctive error code. See the
1583 <a href="pcrecallout.html"><b>pcrecallout</b></a>
1584 documentation for details.
1585 <pre>
1587 </pre>
1588 A string that contains an invalid UTF-8 byte sequence was passed as a subject.
1589 <pre>
1591 </pre>
1592 The UTF-8 byte sequence that was passed as a subject was valid, but the value
1593 of <i>startoffset</i> did not point to the beginning of a UTF-8 character.
1594 <pre>
1596 </pre>
1597 The subject string did not match, but it did match partially. See the
1598 <a href="pcrepartial.html"><b>pcrepartial</b></a>
1599 documentation for details of partial matching.
1600 <pre>
1602 </pre>
1603 This code is no longer in use. It was formerly returned when the PCRE_PARTIAL
1604 option was used with a compiled pattern containing items that were not
1605 supported for partial matching. From release 8.00 onwards, there are no
1606 restrictions on partial matching.
1607 <pre>
1609 </pre>
1610 An unexpected internal error has occurred. This error could be caused by a bug
1611 in PCRE or by overwriting of the compiled pattern.
1612 <pre>
1614 </pre>
1615 This error is given if the value of the <i>ovecsize</i> argument is negative.
1616 <pre>
1618 </pre>
1619 The internal recursion limit, as specified by the <i>match_limit_recursion</i>
1620 field in a <b>pcre_extra</b> structure (or defaulted) was reached. See the
1621 description above.
1622 <pre>
1624 </pre>
1625 An invalid combination of PCRE_NEWLINE_<i>xxx</i> options was given.
1626 </P>
1627 <P>
1628 Error numbers -16 to -20 and -22 are not used by <b>pcre_exec()</b>.
1629 </P>
1630 <br><a name="SEC15" href="#TOC1">EXTRACTING CAPTURED SUBSTRINGS BY NUMBER</a><br>
1631 <P>
1632 <b>int pcre_copy_substring(const char *<i>subject</i>, int *<i>ovector</i>,</b>
1633 <b>int <i>stringcount</i>, int <i>stringnumber</i>, char *<i>buffer</i>,</b>
1634 <b>int <i>buffersize</i>);</b>
1635 </P>
1636 <P>
1637 <b>int pcre_get_substring(const char *<i>subject</i>, int *<i>ovector</i>,</b>
1638 <b>int <i>stringcount</i>, int <i>stringnumber</i>,</b>
1639 <b>const char **<i>stringptr</i>);</b>
1640 </P>
1641 <P>
1642 <b>int pcre_get_substring_list(const char *<i>subject</i>,</b>
1643 <b>int *<i>ovector</i>, int <i>stringcount</i>, const char ***<i>listptr</i>);</b>
1644 </P>
1645 <P>
1646 Captured substrings can be accessed directly by using the offsets returned by
1647 <b>pcre_exec()</b> in <i>ovector</i>. For convenience, the functions
1648 <b>pcre_copy_substring()</b>, <b>pcre_get_substring()</b>, and
1649 <b>pcre_get_substring_list()</b> are provided for extracting captured substrings
1650 as new, separate, zero-terminated strings. These functions identify substrings
1651 by number. The next section describes functions for extracting named
1652 substrings.
1653 </P>
1654 <P>
1655 A substring that contains a binary zero is correctly extracted and has a
1656 further zero added on the end, but the result is not, of course, a C string.
1657 However, you can process such a string by referring to the length that is
1658 returned by <b>pcre_copy_substring()</b> and <b>pcre_get_substring()</b>.
1659 Unfortunately, the interface to <b>pcre_get_substring_list()</b> is not adequate
1660 for handling strings containing binary zeros, because the end of the final
1661 string is not independently indicated.
1662 </P>
1663 <P>
1664 The first three arguments are the same for all three of these functions:
1665 <i>subject</i> is the subject string that has just been successfully matched,
1666 <i>ovector</i> is a pointer to the vector of integer offsets that was passed to
1667 <b>pcre_exec()</b>, and <i>stringcount</i> is the number of substrings that were
1668 captured by the match, including the substring that matched the entire regular
1669 expression. This is the value returned by <b>pcre_exec()</b> if it is greater
1670 than zero. If <b>pcre_exec()</b> returned zero, indicating that it ran out of
1671 space in <i>ovector</i>, the value passed as <i>stringcount</i> should be the
1672 number of elements in the vector divided by three.
1673 </P>
1674 <P>
1675 The functions <b>pcre_copy_substring()</b> and <b>pcre_get_substring()</b>
1676 extract a single substring, whose number is given as <i>stringnumber</i>. A
1677 value of zero extracts the substring that matched the entire pattern, whereas
1678 higher values extract the captured substrings. For <b>pcre_copy_substring()</b>,
1679 the string is placed in <i>buffer</i>, whose length is given by
1680 <i>buffersize</i>, while for <b>pcre_get_substring()</b> a new block of memory is
1681 obtained via <b>pcre_malloc</b>, and its address is returned via
1682 <i>stringptr</i>. The yield of the function is the length of the string, not
1683 including the terminating zero, or one of these error codes:
1684 <pre>
1686 </pre>
1687 The buffer was too small for <b>pcre_copy_substring()</b>, or the attempt to get
1688 memory failed for <b>pcre_get_substring()</b>.
1689 <pre>
1691 </pre>
1692 There is no substring whose number is <i>stringnumber</i>.
1693 </P>
1694 <P>
1695 The <b>pcre_get_substring_list()</b> function extracts all available substrings
1696 and builds a list of pointers to them. All this is done in a single block of
1697 memory that is obtained via <b>pcre_malloc</b>. The address of the memory block
1698 is returned via <i>listptr</i>, which is also the start of the list of string
1699 pointers. The end of the list is marked by a NULL pointer. The yield of the
1700 function is zero if all went well, or the error code
1701 <pre>
1703 </pre>
1704 if the attempt to get the memory block failed.
1705 </P>
1706 <P>
1707 When any of these functions encounter a substring that is unset, which can
1708 happen when capturing subpattern number <i>n+1</i> matches some part of the
1709 subject, but subpattern <i>n</i> has not been used at all, they return an empty
1710 string. This can be distinguished from a genuine zero-length substring by
1711 inspecting the appropriate offset in <i>ovector</i>, which is negative for unset
1712 substrings.
1713 </P>
1714 <P>
1715 The two convenience functions <b>pcre_free_substring()</b> and
1716 <b>pcre_free_substring_list()</b> can be used to free the memory returned by
1717 a previous call of <b>pcre_get_substring()</b> or
1718 <b>pcre_get_substring_list()</b>, respectively. They do nothing more than call
1719 the function pointed to by <b>pcre_free</b>, which of course could be called
1720 directly from a C program. However, PCRE is used in some situations where it is
1721 linked via a special interface to another programming language that cannot use
1722 <b>pcre_free</b> directly; it is for these cases that the functions are
1723 provided.
1724 </P>
1725 <br><a name="SEC16" href="#TOC1">EXTRACTING CAPTURED SUBSTRINGS BY NAME</a><br>
1726 <P>
1727 <b>int pcre_get_stringnumber(const pcre *<i>code</i>,</b>
1728 <b>const char *<i>name</i>);</b>
1729 </P>
1730 <P>
1731 <b>int pcre_copy_named_substring(const pcre *<i>code</i>,</b>
1732 <b>const char *<i>subject</i>, int *<i>ovector</i>,</b>
1733 <b>int <i>stringcount</i>, const char *<i>stringname</i>,</b>
1734 <b>char *<i>buffer</i>, int <i>buffersize</i>);</b>
1735 </P>
1736 <P>
1737 <b>int pcre_get_named_substring(const pcre *<i>code</i>,</b>
1738 <b>const char *<i>subject</i>, int *<i>ovector</i>,</b>
1739 <b>int <i>stringcount</i>, const char *<i>stringname</i>,</b>
1740 <b>const char **<i>stringptr</i>);</b>
1741 </P>
1742 <P>
1743 To extract a substring by name, you first have to find associated number.
1744 For example, for this pattern
1745 <pre>
1746 (a+)b(?&#60;xxx&#62;\d+)...
1747 </pre>
1748 the number of the subpattern called "xxx" is 2. If the name is known to be
1749 unique (PCRE_DUPNAMES was not set), you can find the number from the name by
1750 calling <b>pcre_get_stringnumber()</b>. The first argument is the compiled
1751 pattern, and the second is the name. The yield of the function is the
1752 subpattern number, or PCRE_ERROR_NOSUBSTRING (-7) if there is no subpattern of
1753 that name.
1754 </P>
1755 <P>
1756 Given the number, you can extract the substring directly, or use one of the
1757 functions described in the previous section. For convenience, there are also
1758 two functions that do the whole job.
1759 </P>
1760 <P>
1761 Most of the arguments of <b>pcre_copy_named_substring()</b> and
1762 <b>pcre_get_named_substring()</b> are the same as those for the similarly named
1763 functions that extract by number. As these are described in the previous
1764 section, they are not re-described here. There are just two differences:
1765 </P>
1766 <P>
1767 First, instead of a substring number, a substring name is given. Second, there
1768 is an extra argument, given at the start, which is a pointer to the compiled
1769 pattern. This is needed in order to gain access to the name-to-number
1770 translation table.
1771 </P>
1772 <P>
1773 These functions call <b>pcre_get_stringnumber()</b>, and if it succeeds, they
1774 then call <b>pcre_copy_substring()</b> or <b>pcre_get_substring()</b>, as
1775 appropriate. <b>NOTE:</b> If PCRE_DUPNAMES is set and there are duplicate names,
1776 the behaviour may not be what you want (see the next section).
1777 </P>
1778 <P>
1779 <b>Warning:</b> If the pattern uses the "(?|" feature to set up multiple
1780 subpatterns with the same number, you cannot use names to distinguish them,
1781 because names are not included in the compiled code. The matching process uses
1782 only numbers.
1783 </P>
1784 <br><a name="SEC17" href="#TOC1">DUPLICATE SUBPATTERN NAMES</a><br>
1785 <P>
1786 <b>int pcre_get_stringtable_entries(const pcre *<i>code</i>,</b>
1787 <b>const char *<i>name</i>, char **<i>first</i>, char **<i>last</i>);</b>
1788 </P>
1789 <P>
1790 When a pattern is compiled with the PCRE_DUPNAMES option, names for subpatterns
1791 are not required to be unique. Normally, patterns with duplicate names are such
1792 that in any one match, only one of the named subpatterns participates. An
1793 example is shown in the
1794 <a href="pcrepattern.html"><b>pcrepattern</b></a>
1795 documentation.
1796 </P>
1797 <P>
1798 When duplicates are present, <b>pcre_copy_named_substring()</b> and
1799 <b>pcre_get_named_substring()</b> return the first substring corresponding to
1800 the given name that is set. If none are set, PCRE_ERROR_NOSUBSTRING (-7) is
1801 returned; no data is returned. The <b>pcre_get_stringnumber()</b> function
1802 returns one of the numbers that are associated with the name, but it is not
1803 defined which it is.
1804 </P>
1805 <P>
1806 If you want to get full details of all captured substrings for a given name,
1807 you must use the <b>pcre_get_stringtable_entries()</b> function. The first
1808 argument is the compiled pattern, and the second is the name. The third and
1809 fourth are pointers to variables which are updated by the function. After it
1810 has run, they point to the first and last entries in the name-to-number table
1811 for the given name. The function itself returns the length of each entry, or
1812 PCRE_ERROR_NOSUBSTRING (-7) if there are none. The format of the table is
1813 described above in the section entitled <i>Information about a pattern</i>.
1814 Given all the relevant entries for the name, you can extract each of their
1815 numbers, and hence the captured data, if any.
1816 </P>
1817 <br><a name="SEC18" href="#TOC1">FINDING ALL POSSIBLE MATCHES</a><br>
1818 <P>
1819 The traditional matching function uses a similar algorithm to Perl, which stops
1820 when it finds the first match, starting at a given point in the subject. If you
1821 want to find all possible matches, or the longest possible match, consider
1822 using the alternative matching function (see below) instead. If you cannot use
1823 the alternative function, but still need to find all possible matches, you
1824 can kludge it up by making use of the callout facility, which is described in
1825 the
1826 <a href="pcrecallout.html"><b>pcrecallout</b></a>
1827 documentation.
1828 </P>
1829 <P>
1830 What you have to do is to insert a callout right at the end of the pattern.
1831 When your callout function is called, extract and save the current matched
1832 substring. Then return 1, which forces <b>pcre_exec()</b> to backtrack and try
1833 other alternatives. Ultimately, when it runs out of matches, <b>pcre_exec()</b>
1834 will yield PCRE_ERROR_NOMATCH.
1835 <a name="dfamatch"></a></P>
1836 <br><a name="SEC19" href="#TOC1">MATCHING A PATTERN: THE ALTERNATIVE FUNCTION</a><br>
1837 <P>
1838 <b>int pcre_dfa_exec(const pcre *<i>code</i>, const pcre_extra *<i>extra</i>,</b>
1839 <b>const char *<i>subject</i>, int <i>length</i>, int <i>startoffset</i>,</b>
1840 <b>int <i>options</i>, int *<i>ovector</i>, int <i>ovecsize</i>,</b>
1841 <b>int *<i>workspace</i>, int <i>wscount</i>);</b>
1842 </P>
1843 <P>
1844 The function <b>pcre_dfa_exec()</b> is called to match a subject string against
1845 a compiled pattern, using a matching algorithm that scans the subject string
1846 just once, and does not backtrack. This has different characteristics to the
1847 normal algorithm, and is not compatible with Perl. Some of the features of PCRE
1848 patterns are not supported. Nevertheless, there are times when this kind of
1849 matching can be useful. For a discussion of the two matching algorithms, and a
1850 list of features that <b>pcre_dfa_exec()</b> does not support, see the
1851 <a href="pcrematching.html"><b>pcrematching</b></a>
1852 documentation.
1853 </P>
1854 <P>
1855 The arguments for the <b>pcre_dfa_exec()</b> function are the same as for
1856 <b>pcre_exec()</b>, plus two extras. The <i>ovector</i> argument is used in a
1857 different way, and this is described below. The other common arguments are used
1858 in the same way as for <b>pcre_exec()</b>, so their description is not repeated
1859 here.
1860 </P>
1861 <P>
1862 The two additional arguments provide workspace for the function. The workspace
1863 vector should contain at least 20 elements. It is used for keeping track of
1864 multiple paths through the pattern tree. More workspace will be needed for
1865 patterns and subjects where there are a lot of potential matches.
1866 </P>
1867 <P>
1868 Here is an example of a simple call to <b>pcre_dfa_exec()</b>:
1869 <pre>
1870 int rc;
1871 int ovector[10];
1872 int wspace[20];
1873 rc = pcre_dfa_exec(
1874 re, /* result of pcre_compile() */
1875 NULL, /* we didn't study the pattern */
1876 "some string", /* the subject string */
1877 11, /* the length of the subject string */
1878 0, /* start at offset 0 in the subject */
1879 0, /* default options */
1880 ovector, /* vector of integers for substring information */
1881 10, /* number of elements (NOT size in bytes) */
1882 wspace, /* working space vector */
1883 20); /* number of elements (NOT size in bytes) */
1884 </PRE>
1885 </P>
1886 <br><b>
1887 Option bits for <b>pcre_dfa_exec()</b>
1888 </b><br>
1889 <P>
1890 The unused bits of the <i>options</i> argument for <b>pcre_dfa_exec()</b> must be
1891 zero. The only bits that may be set are PCRE_ANCHORED, PCRE_NEWLINE_<i>xxx</i>,
1894 and PCRE_DFA_RESTART. All but the last four of these are exactly the same as
1895 for <b>pcre_exec()</b>, so their description is not repeated here.
1896 <pre>
1899 </pre>
1900 These have the same general effect as they do for <b>pcre_exec()</b>, but the
1901 details are slightly different. When PCRE_PARTIAL_HARD is set for
1902 <b>pcre_dfa_exec()</b>, it returns PCRE_ERROR_PARTIAL if the end of the subject
1903 is reached and there is still at least one matching possibility that requires
1904 additional characters. This happens even if some complete matches have also
1905 been found. When PCRE_PARTIAL_SOFT is set, the return code PCRE_ERROR_NOMATCH
1906 is converted into PCRE_ERROR_PARTIAL if the end of the subject is reached,
1907 there have been no complete matches, but there is still at least one matching
1908 possibility. The portion of the string that was inspected when the longest
1909 partial match was found is set as the first matching string in both cases.
1910 <pre>
1912 </pre>
1913 Setting the PCRE_DFA_SHORTEST option causes the matching algorithm to stop as
1914 soon as it has found one match. Because of the way the alternative algorithm
1915 works, this is necessarily the shortest possible match at the first possible
1916 matching point in the subject string.
1917 <pre>
1919 </pre>
1920 When <b>pcre_dfa_exec()</b> returns a partial match, it is possible to call it
1921 again, with additional subject characters, and have it continue with the same
1922 match. The PCRE_DFA_RESTART option requests this action; when it is set, the
1923 <i>workspace</i> and <i>wscount</i> options must reference the same vector as
1924 before because data about the match so far is left in them after a partial
1925 match. There is more discussion of this facility in the
1926 <a href="pcrepartial.html"><b>pcrepartial</b></a>
1927 documentation.
1928 </P>
1929 <br><b>
1930 Successful returns from <b>pcre_dfa_exec()</b>
1931 </b><br>
1932 <P>
1933 When <b>pcre_dfa_exec()</b> succeeds, it may have matched more than one
1934 substring in the subject. Note, however, that all the matches from one run of
1935 the function start at the same point in the subject. The shorter matches are
1936 all initial substrings of the longer matches. For example, if the pattern
1937 <pre>
1938 &#60;.*&#62;
1939 </pre>
1940 is matched against the string
1941 <pre>
1942 This is &#60;something&#62; &#60;something else&#62; &#60;something further&#62; no more
1943 </pre>
1944 the three matched strings are
1945 <pre>
1946 &#60;something&#62;
1947 &#60;something&#62; &#60;something else&#62;
1948 &#60;something&#62; &#60;something else&#62; &#60;something further&#62;
1949 </pre>
1950 On success, the yield of the function is a number greater than zero, which is
1951 the number of matched substrings. The substrings themselves are returned in
1952 <i>ovector</i>. Each string uses two elements; the first is the offset to the
1953 start, and the second is the offset to the end. In fact, all the strings have
1954 the same start offset. (Space could have been saved by giving this only once,
1955 but it was decided to retain some compatibility with the way <b>pcre_exec()</b>
1956 returns data, even though the meaning of the strings is different.)
1957 </P>
1958 <P>
1959 The strings are returned in reverse order of length; that is, the longest
1960 matching string is given first. If there were too many matches to fit into
1961 <i>ovector</i>, the yield of the function is zero, and the vector is filled with
1962 the longest matches.
1963 </P>
1964 <br><b>
1965 Error returns from <b>pcre_dfa_exec()</b>
1966 </b><br>
1967 <P>
1968 The <b>pcre_dfa_exec()</b> function returns a negative number when it fails.
1969 Many of the errors are the same as for <b>pcre_exec()</b>, and these are
1970 described
1971 <a href="#errorlist">above.</a>
1972 There are in addition the following errors that are specific to
1973 <b>pcre_dfa_exec()</b>:
1974 <pre>
1976 </pre>
1977 This return is given if <b>pcre_dfa_exec()</b> encounters an item in the pattern
1978 that it does not support, for instance, the use of \C or a back reference.
1979 <pre>
1981 </pre>
1982 This return is given if <b>pcre_dfa_exec()</b> encounters a condition item that
1983 uses a back reference for the condition, or a test for recursion in a specific
1984 group. These are not supported.
1985 <pre>
1987 </pre>
1988 This return is given if <b>pcre_dfa_exec()</b> is called with an <i>extra</i>
1989 block that contains a setting of the <i>match_limit</i> field. This is not
1990 supported (it is meaningless).
1991 <pre>
1993 </pre>
1994 This return is given if <b>pcre_dfa_exec()</b> runs out of space in the
1995 <i>workspace</i> vector.
1996 <pre>
1998 </pre>
1999 When a recursive subpattern is processed, the matching function calls itself
2000 recursively, using private vectors for <i>ovector</i> and <i>workspace</i>. This
2001 error is given if the output vector is not large enough. This should be
2002 extremely rare, as a vector of size 1000 is used.
2003 </P>
2004 <br><a name="SEC20" href="#TOC1">SEE ALSO</a><br>
2005 <P>
2006 <b>pcrebuild</b>(3), <b>pcrecallout</b>(3), <b>pcrecpp(3)</b>(3),
2007 <b>pcrematching</b>(3), <b>pcrepartial</b>(3), <b>pcreposix</b>(3),
2008 <b>pcreprecompile</b>(3), <b>pcresample</b>(3), <b>pcrestack</b>(3).
2009 </P>
2010 <br><a name="SEC21" href="#TOC1">AUTHOR</a><br>
2011 <P>
2012 Philip Hazel
2013 <br>
2014 University Computing Service
2015 <br>
2016 Cambridge CB2 3QH, England.
2017 <br>
2018 </P>
2019 <br><a name="SEC22" href="#TOC1">REVISION</a><br>
2020 <P>
2021 Last updated: 11 September 2009
2022 <br>
2023 Copyright &copy; 1997-2009 University of Cambridge.
2024 <br>
2025 <p>
2026 Return to the <a href="index.html">PCRE index page</a>.
2027 </p>


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