/[pcre]/code/trunk/doc/html/pcreapi.html
ViewVC logotype

Contents of /code/trunk/doc/html/pcreapi.html

Parent Directory Parent Directory | Revision Log Revision Log


Revision 836 - (show annotations) (download) (as text)
Wed Dec 28 17:16:11 2011 UTC (2 years, 11 months ago) by ph10
File MIME type: text/html
File size: 116123 byte(s)
Merging all the changes from the pcre16 branch into the trunk.

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 BASIC FUNCTIONS</a>
17 <li><a name="TOC2" href="#SEC2">PCRE NATIVE API AUXILIARY FUNCTIONS</a>
18 <li><a name="TOC3" href="#SEC3">PCRE NATIVE API INDIRECTED FUNCTIONS</a>
19 <li><a name="TOC4" href="#SEC4">PCRE API OVERVIEW</a>
20 <li><a name="TOC5" href="#SEC5">NEWLINES</a>
21 <li><a name="TOC6" href="#SEC6">MULTITHREADING</a>
22 <li><a name="TOC7" href="#SEC7">SAVING PRECOMPILED PATTERNS FOR LATER USE</a>
23 <li><a name="TOC8" href="#SEC8">CHECKING BUILD-TIME OPTIONS</a>
24 <li><a name="TOC9" href="#SEC9">COMPILING A PATTERN</a>
25 <li><a name="TOC10" href="#SEC10">COMPILATION ERROR CODES</a>
26 <li><a name="TOC11" href="#SEC11">STUDYING A PATTERN</a>
27 <li><a name="TOC12" href="#SEC12">LOCALE SUPPORT</a>
28 <li><a name="TOC13" href="#SEC13">INFORMATION ABOUT A PATTERN</a>
29 <li><a name="TOC14" href="#SEC14">OBSOLETE INFO FUNCTION</a>
30 <li><a name="TOC15" href="#SEC15">REFERENCE COUNTS</a>
31 <li><a name="TOC16" href="#SEC16">MATCHING A PATTERN: THE TRADITIONAL FUNCTION</a>
32 <li><a name="TOC17" href="#SEC17">EXTRACTING CAPTURED SUBSTRINGS BY NUMBER</a>
33 <li><a name="TOC18" href="#SEC18">EXTRACTING CAPTURED SUBSTRINGS BY NAME</a>
34 <li><a name="TOC19" href="#SEC19">DUPLICATE SUBPATTERN NAMES</a>
35 <li><a name="TOC20" href="#SEC20">FINDING ALL POSSIBLE MATCHES</a>
36 <li><a name="TOC21" href="#SEC21">MATCHING A PATTERN: THE ALTERNATIVE FUNCTION</a>
37 <li><a name="TOC22" href="#SEC22">SEE ALSO</a>
38 <li><a name="TOC23" href="#SEC23">AUTHOR</a>
39 <li><a name="TOC24" href="#SEC24">REVISION</a>
40 </ul>
41 <br><a name="SEC1" href="#TOC1">PCRE NATIVE API BASIC FUNCTIONS</a><br>
42 <P>
43 <b>#include &#60;pcre.h&#62;</b>
44 </P>
45 <P>
46 <b>pcre *pcre_compile(const char *<i>pattern</i>, int <i>options</i>,</b>
47 <b>const char **<i>errptr</i>, int *<i>erroffset</i>,</b>
48 <b>const unsigned char *<i>tableptr</i>);</b>
49 </P>
50 <P>
51 <b>pcre *pcre_compile2(const char *<i>pattern</i>, int <i>options</i>,</b>
52 <b>int *<i>errorcodeptr</i>,</b>
53 <b>const char **<i>errptr</i>, int *<i>erroffset</i>,</b>
54 <b>const unsigned char *<i>tableptr</i>);</b>
55 </P>
56 <P>
57 <b>pcre_extra *pcre_study(const pcre *<i>code</i>, int <i>options</i>,</b>
58 <b>const char **<i>errptr</i>);</b>
59 </P>
60 <P>
61 <b>void pcre_free_study(pcre_extra *<i>extra</i>);</b>
62 </P>
63 <P>
64 <b>int pcre_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 </P>
68 <br><a name="SEC2" href="#TOC1">PCRE NATIVE API AUXILIARY FUNCTIONS</a><br>
69 <P>
70 <b>pcre_jit_stack *pcre_jit_stack_alloc(int <i>startsize</i>, int <i>maxsize</i>);</b>
71 </P>
72 <P>
73 <b>void pcre_jit_stack_free(pcre_jit_stack *<i>stack</i>);</b>
74 </P>
75 <P>
76 <b>void pcre_assign_jit_stack(pcre_extra *<i>extra</i>,</b>
77 <b>pcre_jit_callback <i>callback</i>, void *<i>data</i>);</b>
78 </P>
79 <P>
80 <b>int pcre_dfa_exec(const pcre *<i>code</i>, const pcre_extra *<i>extra</i>,</b>
81 <b>const char *<i>subject</i>, int <i>length</i>, int <i>startoffset</i>,</b>
82 <b>int <i>options</i>, int *<i>ovector</i>, int <i>ovecsize</i>,</b>
83 <b>int *<i>workspace</i>, int <i>wscount</i>);</b>
84 </P>
85 <P>
86 <b>int pcre_copy_named_substring(const pcre *<i>code</i>,</b>
87 <b>const char *<i>subject</i>, int *<i>ovector</i>,</b>
88 <b>int <i>stringcount</i>, const char *<i>stringname</i>,</b>
89 <b>char *<i>buffer</i>, int <i>buffersize</i>);</b>
90 </P>
91 <P>
92 <b>int pcre_copy_substring(const char *<i>subject</i>, int *<i>ovector</i>,</b>
93 <b>int <i>stringcount</i>, int <i>stringnumber</i>, char *<i>buffer</i>,</b>
94 <b>int <i>buffersize</i>);</b>
95 </P>
96 <P>
97 <b>int pcre_get_named_substring(const pcre *<i>code</i>,</b>
98 <b>const char *<i>subject</i>, int *<i>ovector</i>,</b>
99 <b>int <i>stringcount</i>, const char *<i>stringname</i>,</b>
100 <b>const char **<i>stringptr</i>);</b>
101 </P>
102 <P>
103 <b>int pcre_get_stringnumber(const pcre *<i>code</i>,</b>
104 <b>const char *<i>name</i>);</b>
105 </P>
106 <P>
107 <b>int pcre_get_stringtable_entries(const pcre *<i>code</i>,</b>
108 <b>const char *<i>name</i>, char **<i>first</i>, char **<i>last</i>);</b>
109 </P>
110 <P>
111 <b>int pcre_get_substring(const char *<i>subject</i>, int *<i>ovector</i>,</b>
112 <b>int <i>stringcount</i>, int <i>stringnumber</i>,</b>
113 <b>const char **<i>stringptr</i>);</b>
114 </P>
115 <P>
116 <b>int pcre_get_substring_list(const char *<i>subject</i>,</b>
117 <b>int *<i>ovector</i>, int <i>stringcount</i>, const char ***<i>listptr</i>);</b>
118 </P>
119 <P>
120 <b>void pcre_free_substring(const char *<i>stringptr</i>);</b>
121 </P>
122 <P>
123 <b>void pcre_free_substring_list(const char **<i>stringptr</i>);</b>
124 </P>
125 <P>
126 <b>const unsigned char *pcre_maketables(void);</b>
127 </P>
128 <P>
129 <b>int pcre_fullinfo(const pcre *<i>code</i>, const pcre_extra *<i>extra</i>,</b>
130 <b>int <i>what</i>, void *<i>where</i>);</b>
131 </P>
132 <P>
133 <b>int pcre_info(const pcre *<i>code</i>, int *<i>optptr</i>, int</b>
134 <b>*<i>firstcharptr</i>);</b>
135 </P>
136 <P>
137 <b>int pcre_refcount(pcre *<i>code</i>, int <i>adjust</i>);</b>
138 </P>
139 <P>
140 <b>int pcre_config(int <i>what</i>, void *<i>where</i>);</b>
141 </P>
142 <P>
143 <b>char *pcre_version(void);</b>
144 </P>
145 <br><a name="SEC3" href="#TOC1">PCRE NATIVE API INDIRECTED FUNCTIONS</a><br>
146 <P>
147 <b>void *(*pcre_malloc)(size_t);</b>
148 </P>
149 <P>
150 <b>void (*pcre_free)(void *);</b>
151 </P>
152 <P>
153 <b>void *(*pcre_stack_malloc)(size_t);</b>
154 </P>
155 <P>
156 <b>void (*pcre_stack_free)(void *);</b>
157 </P>
158 <P>
159 <b>int (*pcre_callout)(pcre_callout_block *);</b>
160 </P>
161 <br><a name="SEC4" href="#TOC1">PCRE API OVERVIEW</a><br>
162 <P>
163 PCRE has its own native API, which is described in this document. There are
164 also some wrapper functions that correspond to the POSIX regular expression
165 API, but they do not give access to all the functionality. They are described
166 in the
167 <a href="pcreposix.html"><b>pcreposix</b></a>
168 documentation. Both of these APIs define a set of C function calls. A C++
169 wrapper is also distributed with PCRE. It is documented in the
170 <a href="pcrecpp.html"><b>pcrecpp</b></a>
171 page.
172 </P>
173 <P>
174 The native API C function prototypes are defined in the header file
175 <b>pcre.h</b>, and on Unix systems the library itself is called <b>libpcre</b>.
176 It can normally be accessed by adding <b>-lpcre</b> to the command for linking
177 an application that uses PCRE. The header file defines the macros PCRE_MAJOR
178 and PCRE_MINOR to contain the major and minor release numbers for the library.
179 Applications can use these to include support for different releases of PCRE.
180 </P>
181 <P>
182 In a Windows environment, if you want to statically link an application program
183 against a non-dll <b>pcre.a</b> file, you must define PCRE_STATIC before
184 including <b>pcre.h</b> or <b>pcrecpp.h</b>, because otherwise the
185 <b>pcre_malloc()</b> and <b>pcre_free()</b> exported functions will be declared
186 <b>__declspec(dllimport)</b>, with unwanted results.
187 </P>
188 <P>
189 The functions <b>pcre_compile()</b>, <b>pcre_compile2()</b>, <b>pcre_study()</b>,
190 and <b>pcre_exec()</b> are used for compiling and matching regular expressions
191 in a Perl-compatible manner. A sample program that demonstrates the simplest
192 way of using them is provided in the file called <i>pcredemo.c</i> in the PCRE
193 source distribution. A listing of this program is given in the
194 <a href="pcredemo.html"><b>pcredemo</b></a>
195 documentation, and the
196 <a href="pcresample.html"><b>pcresample</b></a>
197 documentation describes how to compile and run it.
198 </P>
199 <P>
200 Just-in-time compiler support is an optional feature of PCRE that can be built
201 in appropriate hardware environments. It greatly speeds up the matching
202 performance of many patterns. Simple programs can easily request that it be
203 used if available, by setting an option that is ignored when it is not
204 relevant. More complicated programs might need to make use of the functions
205 <b>pcre_jit_stack_alloc()</b>, <b>pcre_jit_stack_free()</b>, and
206 <b>pcre_assign_jit_stack()</b> in order to control the JIT code's memory usage.
207 These functions are discussed in the
208 <a href="pcrejit.html"><b>pcrejit</b></a>
209 documentation.
210 </P>
211 <P>
212 A second matching function, <b>pcre_dfa_exec()</b>, which is not
213 Perl-compatible, is also provided. This uses a different algorithm for the
214 matching. The alternative algorithm finds all possible matches (at a given
215 point in the subject), and scans the subject just once (unless there are
216 lookbehind assertions). However, this algorithm does not return captured
217 substrings. A description of the two matching algorithms and their advantages
218 and disadvantages is given in the
219 <a href="pcrematching.html"><b>pcrematching</b></a>
220 documentation.
221 </P>
222 <P>
223 In addition to the main compiling and matching functions, there are convenience
224 functions for extracting captured substrings from a subject string that is
225 matched by <b>pcre_exec()</b>. They are:
226 <pre>
227 <b>pcre_copy_substring()</b>
228 <b>pcre_copy_named_substring()</b>
229 <b>pcre_get_substring()</b>
230 <b>pcre_get_named_substring()</b>
231 <b>pcre_get_substring_list()</b>
232 <b>pcre_get_stringnumber()</b>
233 <b>pcre_get_stringtable_entries()</b>
234 </pre>
235 <b>pcre_free_substring()</b> and <b>pcre_free_substring_list()</b> are also
236 provided, to free the memory used for extracted strings.
237 </P>
238 <P>
239 The function <b>pcre_maketables()</b> is used to build a set of character tables
240 in the current locale for passing to <b>pcre_compile()</b>, <b>pcre_exec()</b>,
241 or <b>pcre_dfa_exec()</b>. This is an optional facility that is provided for
242 specialist use. Most commonly, no special tables are passed, in which case
243 internal tables that are generated when PCRE is built are used.
244 </P>
245 <P>
246 The function <b>pcre_fullinfo()</b> is used to find out information about a
247 compiled pattern; <b>pcre_info()</b> is an obsolete version that returns only
248 some of the available information, but is retained for backwards compatibility.
249 The function <b>pcre_version()</b> returns a pointer to a string containing the
250 version of PCRE and its date of release.
251 </P>
252 <P>
253 The function <b>pcre_refcount()</b> maintains a reference count in a data block
254 containing a compiled pattern. This is provided for the benefit of
255 object-oriented applications.
256 </P>
257 <P>
258 The global variables <b>pcre_malloc</b> and <b>pcre_free</b> initially contain
259 the entry points of the standard <b>malloc()</b> and <b>free()</b> functions,
260 respectively. PCRE calls the memory management functions via these variables,
261 so a calling program can replace them if it wishes to intercept the calls. This
262 should be done before calling any PCRE functions.
263 </P>
264 <P>
265 The global variables <b>pcre_stack_malloc</b> and <b>pcre_stack_free</b> are also
266 indirections to memory management functions. These special functions are used
267 only when PCRE is compiled to use the heap for remembering data, instead of
268 recursive function calls, when running the <b>pcre_exec()</b> function. See the
269 <a href="pcrebuild.html"><b>pcrebuild</b></a>
270 documentation for details of how to do this. It is a non-standard way of
271 building PCRE, for use in environments that have limited stacks. Because of the
272 greater use of memory management, it runs more slowly. Separate functions are
273 provided so that special-purpose external code can be used for this case. When
274 used, these functions are always called in a stack-like manner (last obtained,
275 first freed), and always for memory blocks of the same size. There is a
276 discussion about PCRE's stack usage in the
277 <a href="pcrestack.html"><b>pcrestack</b></a>
278 documentation.
279 </P>
280 <P>
281 The global variable <b>pcre_callout</b> initially contains NULL. It can be set
282 by the caller to a "callout" function, which PCRE will then call at specified
283 points during a matching operation. Details are given in the
284 <a href="pcrecallout.html"><b>pcrecallout</b></a>
285 documentation.
286 <a name="newlines"></a></P>
287 <br><a name="SEC5" href="#TOC1">NEWLINES</a><br>
288 <P>
289 PCRE supports five different conventions for indicating line breaks in
290 strings: a single CR (carriage return) character, a single LF (linefeed)
291 character, the two-character sequence CRLF, any of the three preceding, or any
292 Unicode newline sequence. The Unicode newline sequences are the three just
293 mentioned, plus the single characters VT (vertical tab, U+000B), FF (formfeed,
294 U+000C), NEL (next line, U+0085), LS (line separator, U+2028), and PS
295 (paragraph separator, U+2029).
296 </P>
297 <P>
298 Each of the first three conventions is used by at least one operating system as
299 its standard newline sequence. When PCRE is built, a default can be specified.
300 The default default is LF, which is the Unix standard. When PCRE is run, the
301 default can be overridden, either when a pattern is compiled, or when it is
302 matched.
303 </P>
304 <P>
305 At compile time, the newline convention can be specified by the <i>options</i>
306 argument of <b>pcre_compile()</b>, or it can be specified by special text at the
307 start of the pattern itself; this overrides any other settings. See the
308 <a href="pcrepattern.html"><b>pcrepattern</b></a>
309 page for details of the special character sequences.
310 </P>
311 <P>
312 In the PCRE documentation the word "newline" is used to mean "the character or
313 pair of characters that indicate a line break". The choice of newline
314 convention affects the handling of the dot, circumflex, and dollar
315 metacharacters, the handling of #-comments in /x mode, and, when CRLF is a
316 recognized line ending sequence, the match position advancement for a
317 non-anchored pattern. There is more detail about this in the
318 <a href="#execoptions">section on <b>pcre_exec()</b> options</a>
319 below.
320 </P>
321 <P>
322 The choice of newline convention does not affect the interpretation of
323 the \n or \r escape sequences, nor does it affect what \R matches, which is
324 controlled in a similar way, but by separate options.
325 </P>
326 <br><a name="SEC6" href="#TOC1">MULTITHREADING</a><br>
327 <P>
328 The PCRE functions can be used in multi-threading applications, with the
329 proviso that the memory management functions pointed to by <b>pcre_malloc</b>,
330 <b>pcre_free</b>, <b>pcre_stack_malloc</b>, and <b>pcre_stack_free</b>, and the
331 callout function pointed to by <b>pcre_callout</b>, are shared by all threads.
332 </P>
333 <P>
334 The compiled form of a regular expression is not altered during matching, so
335 the same compiled pattern can safely be used by several threads at once.
336 </P>
337 <P>
338 If the just-in-time optimization feature is being used, it needs separate
339 memory stack areas for each thread. See the
340 <a href="pcrejit.html"><b>pcrejit</b></a>
341 documentation for more details.
342 </P>
343 <br><a name="SEC7" href="#TOC1">SAVING PRECOMPILED PATTERNS FOR LATER USE</a><br>
344 <P>
345 The compiled form of a regular expression can be saved and re-used at a later
346 time, possibly by a different program, and even on a host other than the one on
347 which it was compiled. Details are given in the
348 <a href="pcreprecompile.html"><b>pcreprecompile</b></a>
349 documentation. However, compiling a regular expression with one version of PCRE
350 for use with a different version is not guaranteed to work and may cause
351 crashes.
352 </P>
353 <br><a name="SEC8" href="#TOC1">CHECKING BUILD-TIME OPTIONS</a><br>
354 <P>
355 <b>int pcre_config(int <i>what</i>, void *<i>where</i>);</b>
356 </P>
357 <P>
358 The function <b>pcre_config()</b> makes it possible for a PCRE client to
359 discover which optional features have been compiled into the PCRE library. The
360 <a href="pcrebuild.html"><b>pcrebuild</b></a>
361 documentation has more details about these optional features.
362 </P>
363 <P>
364 The first argument for <b>pcre_config()</b> is an integer, specifying which
365 information is required; the second argument is a pointer to a variable into
366 which the information is placed. The following information is available:
367 <pre>
368 PCRE_CONFIG_UTF8
369 </pre>
370 The output is an integer that is set to one if UTF-8 support is available;
371 otherwise it is set to zero.
372 <pre>
373 PCRE_CONFIG_UNICODE_PROPERTIES
374 </pre>
375 The output is an integer that is set to one if support for Unicode character
376 properties is available; otherwise it is set to zero.
377 <pre>
378 PCRE_CONFIG_JIT
379 </pre>
380 The output is an integer that is set to one if support for just-in-time
381 compiling is available; otherwise it is set to zero.
382 <pre>
383 PCRE_CONFIG_NEWLINE
384 </pre>
385 The output is an integer whose value specifies the default character sequence
386 that is recognized as meaning "newline". The four values that are supported
387 are: 10 for LF, 13 for CR, 3338 for CRLF, -2 for ANYCRLF, and -1 for ANY.
388 Though they are derived from ASCII, the same values are returned in EBCDIC
389 environments. The default should normally correspond to the standard sequence
390 for your operating system.
391 <pre>
392 PCRE_CONFIG_BSR
393 </pre>
394 The output is an integer whose value indicates what character sequences the \R
395 escape sequence matches by default. A value of 0 means that \R matches any
396 Unicode line ending sequence; a value of 1 means that \R matches only CR, LF,
397 or CRLF. The default can be overridden when a pattern is compiled or matched.
398 <pre>
399 PCRE_CONFIG_LINK_SIZE
400 </pre>
401 The output is an integer that contains the number of bytes used for internal
402 linkage in compiled regular expressions. The value is 2, 3, or 4. Larger values
403 allow larger regular expressions to be compiled, at the expense of slower
404 matching. The default value of 2 is sufficient for all but the most massive
405 patterns, since it allows the compiled pattern to be up to 64K in size.
406 <pre>
407 PCRE_CONFIG_POSIX_MALLOC_THRESHOLD
408 </pre>
409 The output is an integer that contains the threshold above which the POSIX
410 interface uses <b>malloc()</b> for output vectors. Further details are given in
411 the
412 <a href="pcreposix.html"><b>pcreposix</b></a>
413 documentation.
414 <pre>
415 PCRE_CONFIG_MATCH_LIMIT
416 </pre>
417 The output is a long integer that gives the default limit for the number of
418 internal matching function calls in a <b>pcre_exec()</b> execution. Further
419 details are given with <b>pcre_exec()</b> below.
420 <pre>
421 PCRE_CONFIG_MATCH_LIMIT_RECURSION
422 </pre>
423 The output is a long integer that gives the default limit for the depth of
424 recursion when calling the internal matching function in a <b>pcre_exec()</b>
425 execution. Further details are given with <b>pcre_exec()</b> below.
426 <pre>
427 PCRE_CONFIG_STACKRECURSE
428 </pre>
429 The output is an integer that is set to one if internal recursion when running
430 <b>pcre_exec()</b> is implemented by recursive function calls that use the stack
431 to remember their state. This is the usual way that PCRE is compiled. The
432 output is zero if PCRE was compiled to use blocks of data on the heap instead
433 of recursive function calls. In this case, <b>pcre_stack_malloc</b> and
434 <b>pcre_stack_free</b> are called to manage memory blocks on the heap, thus
435 avoiding the use of the stack.
436 </P>
437 <br><a name="SEC9" href="#TOC1">COMPILING A PATTERN</a><br>
438 <P>
439 <b>pcre *pcre_compile(const char *<i>pattern</i>, int <i>options</i>,</b>
440 <b>const char **<i>errptr</i>, int *<i>erroffset</i>,</b>
441 <b>const unsigned char *<i>tableptr</i>);</b>
442 <b>pcre *pcre_compile2(const char *<i>pattern</i>, int <i>options</i>,</b>
443 <b>int *<i>errorcodeptr</i>,</b>
444 <b>const char **<i>errptr</i>, int *<i>erroffset</i>,</b>
445 <b>const unsigned char *<i>tableptr</i>);</b>
446 </P>
447 <P>
448 Either of the functions <b>pcre_compile()</b> or <b>pcre_compile2()</b> can be
449 called to compile a pattern into an internal form. The only difference between
450 the two interfaces is that <b>pcre_compile2()</b> has an additional argument,
451 <i>errorcodeptr</i>, via which a numerical error code can be returned. To avoid
452 too much repetition, we refer just to <b>pcre_compile()</b> below, but the
453 information applies equally to <b>pcre_compile2()</b>.
454 </P>
455 <P>
456 The pattern is a C string terminated by a binary zero, and is passed in the
457 <i>pattern</i> argument. A pointer to a single block of memory that is obtained
458 via <b>pcre_malloc</b> is returned. This contains the compiled code and related
459 data. The <b>pcre</b> type is defined for the returned block; this is a typedef
460 for a structure whose contents are not externally defined. It is up to the
461 caller to free the memory (via <b>pcre_free</b>) when it is no longer required.
462 </P>
463 <P>
464 Although the compiled code of a PCRE regex is relocatable, that is, it does not
465 depend on memory location, the complete <b>pcre</b> data block is not
466 fully relocatable, because it may contain a copy of the <i>tableptr</i>
467 argument, which is an address (see below).
468 </P>
469 <P>
470 The <i>options</i> argument contains various bit settings that affect the
471 compilation. It should be zero if no options are required. The available
472 options are described below. Some of them (in particular, those that are
473 compatible with Perl, but some others as well) can also be set and unset from
474 within the pattern (see the detailed description in the
475 <a href="pcrepattern.html"><b>pcrepattern</b></a>
476 documentation). For those options that can be different in different parts of
477 the pattern, the contents of the <i>options</i> argument specifies their
478 settings at the start of compilation and execution. The PCRE_ANCHORED,
479 PCRE_BSR_<i>xxx</i>, PCRE_NEWLINE_<i>xxx</i>, PCRE_NO_UTF8_CHECK, and
480 PCRE_NO_START_OPT options can be set at the time of matching as well as at
481 compile time.
482 </P>
483 <P>
484 If <i>errptr</i> is NULL, <b>pcre_compile()</b> returns NULL immediately.
485 Otherwise, if compilation of a pattern fails, <b>pcre_compile()</b> returns
486 NULL, and sets the variable pointed to by <i>errptr</i> to point to a textual
487 error message. This is a static string that is part of the library. You must
488 not try to free it. Normally, the offset from the start of the pattern to the
489 byte that was being processed when the error was discovered is placed in the
490 variable pointed to by <i>erroffset</i>, which must not be NULL (if it is, an
491 immediate error is given). However, for an invalid UTF-8 string, the offset is
492 that of the first byte of the failing character. Also, some errors are not
493 detected until checks are carried out when the whole pattern has been scanned;
494 in these cases the offset passed back is the length of the pattern.
495 </P>
496 <P>
497 Note that the offset is in bytes, not characters, even in UTF-8 mode. It may
498 sometimes point into the middle of a UTF-8 character.
499 </P>
500 <P>
501 If <b>pcre_compile2()</b> is used instead of <b>pcre_compile()</b>, and the
502 <i>errorcodeptr</i> argument is not NULL, a non-zero error code number is
503 returned via this argument in the event of an error. This is in addition to the
504 textual error message. Error codes and messages are listed below.
505 </P>
506 <P>
507 If the final argument, <i>tableptr</i>, is NULL, PCRE uses a default set of
508 character tables that are built when PCRE is compiled, using the default C
509 locale. Otherwise, <i>tableptr</i> must be an address that is the result of a
510 call to <b>pcre_maketables()</b>. This value is stored with the compiled
511 pattern, and used again by <b>pcre_exec()</b>, unless another table pointer is
512 passed to it. For more discussion, see the section on locale support below.
513 </P>
514 <P>
515 This code fragment shows a typical straightforward call to <b>pcre_compile()</b>:
516 <pre>
517 pcre *re;
518 const char *error;
519 int erroffset;
520 re = pcre_compile(
521 "^A.*Z", /* the pattern */
522 0, /* default options */
523 &error, /* for error message */
524 &erroffset, /* for error offset */
525 NULL); /* use default character tables */
526 </pre>
527 The following names for option bits are defined in the <b>pcre.h</b> header
528 file:
529 <pre>
530 PCRE_ANCHORED
531 </pre>
532 If this bit is set, the pattern is forced to be "anchored", that is, it is
533 constrained to match only at the first matching point in the string that is
534 being searched (the "subject string"). This effect can also be achieved by
535 appropriate constructs in the pattern itself, which is the only way to do it in
536 Perl.
537 <pre>
538 PCRE_AUTO_CALLOUT
539 </pre>
540 If this bit is set, <b>pcre_compile()</b> automatically inserts callout items,
541 all with number 255, before each pattern item. For discussion of the callout
542 facility, see the
543 <a href="pcrecallout.html"><b>pcrecallout</b></a>
544 documentation.
545 <pre>
546 PCRE_BSR_ANYCRLF
547 PCRE_BSR_UNICODE
548 </pre>
549 These options (which are mutually exclusive) control what the \R escape
550 sequence matches. The choice is either to match only CR, LF, or CRLF, or to
551 match any Unicode newline sequence. The default is specified when PCRE is
552 built. It can be overridden from within the pattern, or by setting an option
553 when a compiled pattern is matched.
554 <pre>
555 PCRE_CASELESS
556 </pre>
557 If this bit is set, letters in the pattern match both upper and lower case
558 letters. It is equivalent to Perl's /i option, and it can be changed within a
559 pattern by a (?i) option setting. In UTF-8 mode, PCRE always understands the
560 concept of case for characters whose values are less than 128, so caseless
561 matching is always possible. For characters with higher values, the concept of
562 case is supported if PCRE is compiled with Unicode property support, but not
563 otherwise. If you want to use caseless matching for characters 128 and above,
564 you must ensure that PCRE is compiled with Unicode property support as well as
565 with UTF-8 support.
566 <pre>
567 PCRE_DOLLAR_ENDONLY
568 </pre>
569 If this bit is set, a dollar metacharacter in the pattern matches only at the
570 end of the subject string. Without this option, a dollar also matches
571 immediately before a newline at the end of the string (but not before any other
572 newlines). The PCRE_DOLLAR_ENDONLY option is ignored if PCRE_MULTILINE is set.
573 There is no equivalent to this option in Perl, and no way to set it within a
574 pattern.
575 <pre>
576 PCRE_DOTALL
577 </pre>
578 If this bit is set, a dot metacharacter in the pattern matches a character of
579 any value, including one that indicates a newline. However, it only ever
580 matches one character, even if newlines are coded as CRLF. Without this option,
581 a dot does not match when the current position is at a newline. This option is
582 equivalent to Perl's /s option, and it can be changed within a pattern by a
583 (?s) option setting. A negative class such as [^a] always matches newline
584 characters, independent of the setting of this option.
585 <pre>
586 PCRE_DUPNAMES
587 </pre>
588 If this bit is set, names used to identify capturing subpatterns need not be
589 unique. This can be helpful for certain types of pattern when it is known that
590 only one instance of the named subpattern can ever be matched. There are more
591 details of named subpatterns below; see also the
592 <a href="pcrepattern.html"><b>pcrepattern</b></a>
593 documentation.
594 <pre>
595 PCRE_EXTENDED
596 </pre>
597 If this bit is set, whitespace data characters in the pattern are totally
598 ignored except when escaped or inside a character class. Whitespace does not
599 include the VT character (code 11). In addition, characters between an
600 unescaped # outside a character class and the next newline, inclusive, are also
601 ignored. This is equivalent to Perl's /x option, and it can be changed within a
602 pattern by a (?x) option setting.
603 </P>
604 <P>
605 Which characters are interpreted as newlines is controlled by the options
606 passed to <b>pcre_compile()</b> or by a special sequence at the start of the
607 pattern, as described in the section entitled
608 <a href="pcrepattern.html#newlines">"Newline conventions"</a>
609 in the <b>pcrepattern</b> documentation. Note that the end of this type of
610 comment is a literal newline sequence in the pattern; escape sequences that
611 happen to represent a newline do not count.
612 </P>
613 <P>
614 This option makes it possible to include comments inside complicated patterns.
615 Note, however, that this applies only to data characters. Whitespace characters
616 may never appear within special character sequences in a pattern, for example
617 within the sequence (?( that introduces a conditional subpattern.
618 <pre>
619 PCRE_EXTRA
620 </pre>
621 This option was invented in order to turn on additional functionality of PCRE
622 that is incompatible with Perl, but it is currently of very little use. When
623 set, any backslash in a pattern that is followed by a letter that has no
624 special meaning causes an error, thus reserving these combinations for future
625 expansion. By default, as in Perl, a backslash followed by a letter with no
626 special meaning is treated as a literal. (Perl can, however, be persuaded to
627 give an error for this, by running it with the -w option.) There are at present
628 no other features controlled by this option. It can also be set by a (?X)
629 option setting within a pattern.
630 <pre>
631 PCRE_FIRSTLINE
632 </pre>
633 If this option is set, an unanchored pattern is required to match before or at
634 the first newline in the subject string, though the matched text may continue
635 over the newline.
636 <pre>
637 PCRE_JAVASCRIPT_COMPAT
638 </pre>
639 If this option is set, PCRE's behaviour is changed in some ways so that it is
640 compatible with JavaScript rather than Perl. The changes are as follows:
641 </P>
642 <P>
643 (1) A lone closing square bracket in a pattern causes a compile-time error,
644 because this is illegal in JavaScript (by default it is treated as a data
645 character). Thus, the pattern AB]CD becomes illegal when this option is set.
646 </P>
647 <P>
648 (2) At run time, a back reference to an unset subpattern group matches an empty
649 string (by default this causes the current matching alternative to fail). A
650 pattern such as (\1)(a) succeeds when this option is set (assuming it can find
651 an "a" in the subject), whereas it fails by default, for Perl compatibility.
652 </P>
653 <P>
654 (3) \U matches an upper case "U" character; by default \U causes a compile
655 time error (Perl uses \U to upper case subsequent characters).
656 </P>
657 <P>
658 (4) \u matches a lower case "u" character unless it is followed by four
659 hexadecimal digits, in which case the hexadecimal number defines the code point
660 to match. By default, \u causes a compile time error (Perl uses it to upper
661 case the following character).
662 </P>
663 <P>
664 (5) \x matches a lower case "x" character unless it is followed by two
665 hexadecimal digits, in which case the hexadecimal number defines the code point
666 to match. By default, as in Perl, a hexadecimal number is always expected after
667 \x, but it may have zero, one, or two digits (so, for example, \xz matches a
668 binary zero character followed by z).
669 <pre>
670 PCRE_MULTILINE
671 </pre>
672 By default, PCRE treats the subject string as consisting of a single line of
673 characters (even if it actually contains newlines). The "start of line"
674 metacharacter (^) matches only at the start of the string, while the "end of
675 line" metacharacter ($) matches only at the end of the string, or before a
676 terminating newline (unless PCRE_DOLLAR_ENDONLY is set). This is the same as
677 Perl.
678 </P>
679 <P>
680 When PCRE_MULTILINE it is set, the "start of line" and "end of line" constructs
681 match immediately following or immediately before internal newlines in the
682 subject string, respectively, as well as at the very start and end. This is
683 equivalent to Perl's /m option, and it can be changed within a pattern by a
684 (?m) option setting. If there are no newlines in a subject string, or no
685 occurrences of ^ or $ in a pattern, setting PCRE_MULTILINE has no effect.
686 <pre>
687 PCRE_NEWLINE_CR
688 PCRE_NEWLINE_LF
689 PCRE_NEWLINE_CRLF
690 PCRE_NEWLINE_ANYCRLF
691 PCRE_NEWLINE_ANY
692 </pre>
693 These options override the default newline definition that was chosen when PCRE
694 was built. Setting the first or the second specifies that a newline is
695 indicated by a single character (CR or LF, respectively). Setting
696 PCRE_NEWLINE_CRLF specifies that a newline is indicated by the two-character
697 CRLF sequence. Setting PCRE_NEWLINE_ANYCRLF specifies that any of the three
698 preceding sequences should be recognized. Setting PCRE_NEWLINE_ANY specifies
699 that any Unicode newline sequence should be recognized. The Unicode newline
700 sequences are the three just mentioned, plus the single characters VT (vertical
701 tab, U+000B), FF (formfeed, U+000C), NEL (next line, U+0085), LS (line
702 separator, U+2028), and PS (paragraph separator, U+2029). The last two are
703 recognized only in UTF-8 mode.
704 </P>
705 <P>
706 The newline setting in the options word uses three bits that are treated
707 as a number, giving eight possibilities. Currently only six are used (default
708 plus the five values above). This means that if you set more than one newline
709 option, the combination may or may not be sensible. For example,
710 PCRE_NEWLINE_CR with PCRE_NEWLINE_LF is equivalent to PCRE_NEWLINE_CRLF, but
711 other combinations may yield unused numbers and cause an error.
712 </P>
713 <P>
714 The only time that a line break in a pattern is specially recognized when
715 compiling is when PCRE_EXTENDED is set. CR and LF are whitespace characters,
716 and so are ignored in this mode. Also, an unescaped # outside a character class
717 indicates a comment that lasts until after the next line break sequence. In
718 other circumstances, line break sequences in patterns are treated as literal
719 data.
720 </P>
721 <P>
722 The newline option that is set at compile time becomes the default that is used
723 for <b>pcre_exec()</b> and <b>pcre_dfa_exec()</b>, but it can be overridden.
724 <pre>
725 PCRE_NO_AUTO_CAPTURE
726 </pre>
727 If this option is set, it disables the use of numbered capturing parentheses in
728 the pattern. Any opening parenthesis that is not followed by ? behaves as if it
729 were followed by ?: but named parentheses can still be used for capturing (and
730 they acquire numbers in the usual way). There is no equivalent of this option
731 in Perl.
732 <pre>
733 NO_START_OPTIMIZE
734 </pre>
735 This is an option that acts at matching time; that is, it is really an option
736 for <b>pcre_exec()</b> or <b>pcre_dfa_exec()</b>. If it is set at compile time,
737 it is remembered with the compiled pattern and assumed at matching time. For
738 details see the discussion of PCRE_NO_START_OPTIMIZE
739 <a href="#execoptions">below.</a>
740 <pre>
741 PCRE_UCP
742 </pre>
743 This option changes the way PCRE processes \B, \b, \D, \d, \S, \s, \W,
744 \w, and some of the POSIX character classes. By default, only ASCII characters
745 are recognized, but if PCRE_UCP is set, Unicode properties are used instead to
746 classify characters. More details are given in the section on
747 <a href="pcre.html#genericchartypes">generic character types</a>
748 in the
749 <a href="pcrepattern.html"><b>pcrepattern</b></a>
750 page. If you set PCRE_UCP, matching one of the items it affects takes much
751 longer. The option is available only if PCRE has been compiled with Unicode
752 property support.
753 <pre>
754 PCRE_UNGREEDY
755 </pre>
756 This option inverts the "greediness" of the quantifiers so that they are not
757 greedy by default, but become greedy if followed by "?". It is not compatible
758 with Perl. It can also be set by a (?U) option setting within the pattern.
759 <pre>
760 PCRE_UTF8
761 </pre>
762 This option causes PCRE to regard both the pattern and the subject as strings
763 of UTF-8 characters instead of single-byte character strings. However, it is
764 available only when PCRE is built to include UTF-8 support. If not, the use
765 of this option provokes an error. Details of how this option changes the
766 behaviour of PCRE are given in the
767 <a href="pcreunicode.html"><b>pcreunicode</b></a>
768 page.
769 <pre>
770 PCRE_NO_UTF8_CHECK
771 </pre>
772 When PCRE_UTF8 is set, the validity of the pattern as a UTF-8 string is
773 automatically checked. There is a discussion about the
774 <a href="pcre.html#utf8strings">validity of UTF-8 strings</a>
775 in the main
776 <a href="pcre.html"><b>pcre</b></a>
777 page. If an invalid UTF-8 sequence of bytes is found, <b>pcre_compile()</b>
778 returns an error. If you already know that your pattern is valid, and you want
779 to skip this check for performance reasons, you can set the PCRE_NO_UTF8_CHECK
780 option. When it is set, the effect of passing an invalid UTF-8 string as a
781 pattern is undefined. It may cause your program to crash. Note that this option
782 can also be passed to <b>pcre_exec()</b> and <b>pcre_dfa_exec()</b>, to suppress
783 the UTF-8 validity checking of subject strings.
784 </P>
785 <br><a name="SEC10" href="#TOC1">COMPILATION ERROR CODES</a><br>
786 <P>
787 The following table lists the error codes than may be returned by
788 <b>pcre_compile2()</b>, along with the error messages that may be returned by
789 both compiling functions. As PCRE has developed, some error codes have fallen
790 out of use. To avoid confusion, they have not been re-used.
791 <pre>
792 0 no error
793 1 \ at end of pattern
794 2 \c at end of pattern
795 3 unrecognized character follows \
796 4 numbers out of order in {} quantifier
797 5 number too big in {} quantifier
798 6 missing terminating ] for character class
799 7 invalid escape sequence in character class
800 8 range out of order in character class
801 9 nothing to repeat
802 10 [this code is not in use]
803 11 internal error: unexpected repeat
804 12 unrecognized character after (? or (?-
805 13 POSIX named classes are supported only within a class
806 14 missing )
807 15 reference to non-existent subpattern
808 16 erroffset passed as NULL
809 17 unknown option bit(s) set
810 18 missing ) after comment
811 19 [this code is not in use]
812 20 regular expression is too large
813 21 failed to get memory
814 22 unmatched parentheses
815 23 internal error: code overflow
816 24 unrecognized character after (?&#60;
817 25 lookbehind assertion is not fixed length
818 26 malformed number or name after (?(
819 27 conditional group contains more than two branches
820 28 assertion expected after (?(
821 29 (?R or (?[+-]digits must be followed by )
822 30 unknown POSIX class name
823 31 POSIX collating elements are not supported
824 32 this version of PCRE is not compiled with PCRE_UTF8 support
825 33 [this code is not in use]
826 34 character value in \x{...} sequence is too large
827 35 invalid condition (?(0)
828 36 \C not allowed in lookbehind assertion
829 37 PCRE does not support \L, \l, \N{name}, \U, or \u
830 38 number after (?C is &#62; 255
831 39 closing ) for (?C expected
832 40 recursive call could loop indefinitely
833 41 unrecognized character after (?P
834 42 syntax error in subpattern name (missing terminator)
835 43 two named subpatterns have the same name
836 44 invalid UTF-8 string
837 45 support for \P, \p, and \X has not been compiled
838 46 malformed \P or \p sequence
839 47 unknown property name after \P or \p
840 48 subpattern name is too long (maximum 32 characters)
841 49 too many named subpatterns (maximum 10000)
842 50 [this code is not in use]
843 51 octal value is greater than \377 (not in UTF-8 mode)
844 52 internal error: overran compiling workspace
845 53 internal error: previously-checked referenced subpattern
846 not found
847 54 DEFINE group contains more than one branch
848 55 repeating a DEFINE group is not allowed
849 56 inconsistent NEWLINE options
850 57 \g is not followed by a braced, angle-bracketed, or quoted
851 name/number or by a plain number
852 58 a numbered reference must not be zero
853 59 an argument is not allowed for (*ACCEPT), (*FAIL), or (*COMMIT)
854 60 (*VERB) not recognized
855 61 number is too big
856 62 subpattern name expected
857 63 digit expected after (?+
858 64 ] is an invalid data character in JavaScript compatibility mode
859 65 different names for subpatterns of the same number are
860 not allowed
861 66 (*MARK) must have an argument
862 67 this version of PCRE is not compiled with PCRE_UCP support
863 68 \c must be followed by an ASCII character
864 69 \k is not followed by a braced, angle-bracketed, or quoted name
865 </pre>
866 The numbers 32 and 10000 in errors 48 and 49 are defaults; different values may
867 be used if the limits were changed when PCRE was built.
868 <a name="studyingapattern"></a></P>
869 <br><a name="SEC11" href="#TOC1">STUDYING A PATTERN</a><br>
870 <P>
871 <b>pcre_extra *pcre_study(const pcre *<i>code</i>, int <i>options</i></b>
872 <b>const char **<i>errptr</i>);</b>
873 </P>
874 <P>
875 If a compiled pattern is going to be used several times, it is worth spending
876 more time analyzing it in order to speed up the time taken for matching. The
877 function <b>pcre_study()</b> takes a pointer to a compiled pattern as its first
878 argument. If studying the pattern produces additional information that will
879 help speed up matching, <b>pcre_study()</b> returns a pointer to a
880 <b>pcre_extra</b> block, in which the <i>study_data</i> field points to the
881 results of the study.
882 </P>
883 <P>
884 The returned value from <b>pcre_study()</b> can be passed directly to
885 <b>pcre_exec()</b> or <b>pcre_dfa_exec()</b>. However, a <b>pcre_extra</b> block
886 also contains other fields that can be set by the caller before the block is
887 passed; these are described
888 <a href="#extradata">below</a>
889 in the section on matching a pattern.
890 </P>
891 <P>
892 If studying the pattern does not produce any useful information,
893 <b>pcre_study()</b> returns NULL. In that circumstance, if the calling program
894 wants to pass any of the other fields to <b>pcre_exec()</b> or
895 <b>pcre_dfa_exec()</b>, it must set up its own <b>pcre_extra</b> block.
896 </P>
897 <P>
898 The second argument of <b>pcre_study()</b> contains option bits. There is only
899 one option: PCRE_STUDY_JIT_COMPILE. If this is set, and the just-in-time
900 compiler is available, the pattern is further compiled into machine code that
901 executes much faster than the <b>pcre_exec()</b> matching function. If
902 the just-in-time compiler is not available, this option is ignored. All other
903 bits in the <i>options</i> argument must be zero.
904 </P>
905 <P>
906 JIT compilation is a heavyweight optimization. It can take some time for
907 patterns to be analyzed, and for one-off matches and simple patterns the
908 benefit of faster execution might be offset by a much slower study time.
909 Not all patterns can be optimized by the JIT compiler. For those that cannot be
910 handled, matching automatically falls back to the <b>pcre_exec()</b>
911 interpreter. For more details, see the
912 <a href="pcrejit.html"><b>pcrejit</b></a>
913 documentation.
914 </P>
915 <P>
916 The third argument for <b>pcre_study()</b> is a pointer for an error message. If
917 studying succeeds (even if no data is returned), the variable it points to is
918 set to NULL. Otherwise it is set to point to a textual error message. This is a
919 static string that is part of the library. You must not try to free it. You
920 should test the error pointer for NULL after calling <b>pcre_study()</b>, to be
921 sure that it has run successfully.
922 </P>
923 <P>
924 When you are finished with a pattern, you can free the memory used for the
925 study data by calling <b>pcre_free_study()</b>. This function was added to the
926 API for release 8.20. For earlier versions, the memory could be freed with
927 <b>pcre_free()</b>, just like the pattern itself. This will still work in cases
928 where PCRE_STUDY_JIT_COMPILE is not used, but it is advisable to change to the
929 new function when convenient.
930 </P>
931 <P>
932 This is a typical way in which <b>pcre_study</b>() is used (except that in a
933 real application there should be tests for errors):
934 <pre>
935 int rc;
936 pcre *re;
937 pcre_extra *sd;
938 re = pcre_compile("pattern", 0, &error, &erroroffset, NULL);
939 sd = pcre_study(
940 re, /* result of pcre_compile() */
941 0, /* no options */
942 &error); /* set to NULL or points to a message */
943 rc = pcre_exec( /* see below for details of pcre_exec() options */
944 re, sd, "subject", 7, 0, 0, ovector, 30);
945 ...
946 pcre_free_study(sd);
947 pcre_free(re);
948 </pre>
949 Studying a pattern does two things: first, a lower bound for the length of
950 subject string that is needed to match the pattern is computed. This does not
951 mean that there are any strings of that length that match, but it does
952 guarantee that no shorter strings match. The value is used by
953 <b>pcre_exec()</b> and <b>pcre_dfa_exec()</b> to avoid wasting time by trying to
954 match strings that are shorter than the lower bound. You can find out the value
955 in a calling program via the <b>pcre_fullinfo()</b> function.
956 </P>
957 <P>
958 Studying a pattern is also useful for non-anchored patterns that do not have a
959 single fixed starting character. A bitmap of possible starting bytes is
960 created. This speeds up finding a position in the subject at which to start
961 matching.
962 </P>
963 <P>
964 These two optimizations apply to both <b>pcre_exec()</b> and
965 <b>pcre_dfa_exec()</b>. However, they are not used by <b>pcre_exec()</b> if
966 <b>pcre_study()</b> is called with the PCRE_STUDY_JIT_COMPILE option, and
967 just-in-time compiling is successful. The optimizations can be disabled by
968 setting the PCRE_NO_START_OPTIMIZE option when calling <b>pcre_exec()</b> or
969 <b>pcre_dfa_exec()</b>. You might want to do this if your pattern contains
970 callouts or (*MARK) (which cannot be handled by the JIT compiler), and you want
971 to make use of these facilities in cases where matching fails. See the
972 discussion of PCRE_NO_START_OPTIMIZE
973 <a href="#execoptions">below.</a>
974 <a name="localesupport"></a></P>
975 <br><a name="SEC12" href="#TOC1">LOCALE SUPPORT</a><br>
976 <P>
977 PCRE handles caseless matching, and determines whether characters are letters,
978 digits, or whatever, by reference to a set of tables, indexed by character
979 value. When running in UTF-8 mode, this applies only to characters with codes
980 less than 128. By default, higher-valued codes never match escapes such as \w
981 or \d, but they can be tested with \p if PCRE is built with Unicode character
982 property support. Alternatively, the PCRE_UCP option can be set at compile
983 time; this causes \w and friends to use Unicode property support instead of
984 built-in tables. The use of locales with Unicode is discouraged. If you are
985 handling characters with codes greater than 128, you should either use UTF-8
986 and Unicode, or use locales, but not try to mix the two.
987 </P>
988 <P>
989 PCRE contains an internal set of tables that are used when the final argument
990 of <b>pcre_compile()</b> is NULL. These are sufficient for many applications.
991 Normally, the internal tables recognize only ASCII characters. However, when
992 PCRE is built, it is possible to cause the internal tables to be rebuilt in the
993 default "C" locale of the local system, which may cause them to be different.
994 </P>
995 <P>
996 The internal tables can always be overridden by tables supplied by the
997 application that calls PCRE. These may be created in a different locale from
998 the default. As more and more applications change to using Unicode, the need
999 for this locale support is expected to die away.
1000 </P>
1001 <P>
1002 External tables are built by calling the <b>pcre_maketables()</b> function,
1003 which has no arguments, in the relevant locale. The result can then be passed
1004 to <b>pcre_compile()</b> or <b>pcre_exec()</b> as often as necessary. For
1005 example, to build and use tables that are appropriate for the French locale
1006 (where accented characters with values greater than 128 are treated as letters),
1007 the following code could be used:
1008 <pre>
1009 setlocale(LC_CTYPE, "fr_FR");
1010 tables = pcre_maketables();
1011 re = pcre_compile(..., tables);
1012 </pre>
1013 The locale name "fr_FR" is used on Linux and other Unix-like systems; if you
1014 are using Windows, the name for the French locale is "french".
1015 </P>
1016 <P>
1017 When <b>pcre_maketables()</b> runs, the tables are built in memory that is
1018 obtained via <b>pcre_malloc</b>. It is the caller's responsibility to ensure
1019 that the memory containing the tables remains available for as long as it is
1020 needed.
1021 </P>
1022 <P>
1023 The pointer that is passed to <b>pcre_compile()</b> is saved with the compiled
1024 pattern, and the same tables are used via this pointer by <b>pcre_study()</b>
1025 and normally also by <b>pcre_exec()</b>. Thus, by default, for any single
1026 pattern, compilation, studying and matching all happen in the same locale, but
1027 different patterns can be compiled in different locales.
1028 </P>
1029 <P>
1030 It is possible to pass a table pointer or NULL (indicating the use of the
1031 internal tables) to <b>pcre_exec()</b>. Although not intended for this purpose,
1032 this facility could be used to match a pattern in a different locale from the
1033 one in which it was compiled. Passing table pointers at run time is discussed
1034 below in the section on matching a pattern.
1035 <a name="infoaboutpattern"></a></P>
1036 <br><a name="SEC13" href="#TOC1">INFORMATION ABOUT A PATTERN</a><br>
1037 <P>
1038 <b>int pcre_fullinfo(const pcre *<i>code</i>, const pcre_extra *<i>extra</i>,</b>
1039 <b>int <i>what</i>, void *<i>where</i>);</b>
1040 </P>
1041 <P>
1042 The <b>pcre_fullinfo()</b> function returns information about a compiled
1043 pattern. It replaces the obsolete <b>pcre_info()</b> function, which is
1044 nevertheless retained for backwards compability (and is documented below).
1045 </P>
1046 <P>
1047 The first argument for <b>pcre_fullinfo()</b> is a pointer to the compiled
1048 pattern. The second argument is the result of <b>pcre_study()</b>, or NULL if
1049 the pattern was not studied. The third argument specifies which piece of
1050 information is required, and the fourth argument is a pointer to a variable
1051 to receive the data. The yield of the function is zero for success, or one of
1052 the following negative numbers:
1053 <pre>
1054 PCRE_ERROR_NULL the argument <i>code</i> was NULL
1055 the argument <i>where</i> was NULL
1056 PCRE_ERROR_BADMAGIC the "magic number" was not found
1057 PCRE_ERROR_BADOPTION the value of <i>what</i> was invalid
1058 </pre>
1059 The "magic number" is placed at the start of each compiled pattern as an simple
1060 check against passing an arbitrary memory pointer. Here is a typical call of
1061 <b>pcre_fullinfo()</b>, to obtain the length of the compiled pattern:
1062 <pre>
1063 int rc;
1064 size_t length;
1065 rc = pcre_fullinfo(
1066 re, /* result of pcre_compile() */
1067 sd, /* result of pcre_study(), or NULL */
1068 PCRE_INFO_SIZE, /* what is required */
1069 &length); /* where to put the data */
1070 </pre>
1071 The possible values for the third argument are defined in <b>pcre.h</b>, and are
1072 as follows:
1073 <pre>
1074 PCRE_INFO_BACKREFMAX
1075 </pre>
1076 Return the number of the highest back reference in the pattern. The fourth
1077 argument should point to an <b>int</b> variable. Zero is returned if there are
1078 no back references.
1079 <pre>
1080 PCRE_INFO_CAPTURECOUNT
1081 </pre>
1082 Return the number of capturing subpatterns in the pattern. The fourth argument
1083 should point to an <b>int</b> variable.
1084 <pre>
1085 PCRE_INFO_DEFAULT_TABLES
1086 </pre>
1087 Return a pointer to the internal default character tables within PCRE. The
1088 fourth argument should point to an <b>unsigned char *</b> variable. This
1089 information call is provided for internal use by the <b>pcre_study()</b>
1090 function. External callers can cause PCRE to use its internal tables by passing
1091 a NULL table pointer.
1092 <pre>
1093 PCRE_INFO_FIRSTBYTE
1094 </pre>
1095 Return information about the first byte of any matched string, for a
1096 non-anchored pattern. The fourth argument should point to an <b>int</b>
1097 variable. (This option used to be called PCRE_INFO_FIRSTCHAR; the old name is
1098 still recognized for backwards compatibility.)
1099 </P>
1100 <P>
1101 If there is a fixed first byte, for example, from a pattern such as
1102 (cat|cow|coyote), its value is returned. Otherwise, if either
1103 <br>
1104 <br>
1105 (a) the pattern was compiled with the PCRE_MULTILINE option, and every branch
1106 starts with "^", or
1107 <br>
1108 <br>
1109 (b) every branch of the pattern starts with ".*" and PCRE_DOTALL is not set
1110 (if it were set, the pattern would be anchored),
1111 <br>
1112 <br>
1113 -1 is returned, indicating that the pattern matches only at the start of a
1114 subject string or after any newline within the string. Otherwise -2 is
1115 returned. For anchored patterns, -2 is returned.
1116 <pre>
1117 PCRE_INFO_FIRSTTABLE
1118 </pre>
1119 If the pattern was studied, and this resulted in the construction of a 256-bit
1120 table indicating a fixed set of bytes for the first byte in any matching
1121 string, a pointer to the table is returned. Otherwise NULL is returned. The
1122 fourth argument should point to an <b>unsigned char *</b> variable.
1123 <pre>
1124 PCRE_INFO_HASCRORLF
1125 </pre>
1126 Return 1 if the pattern contains any explicit matches for CR or LF characters,
1127 otherwise 0. The fourth argument should point to an <b>int</b> variable. An
1128 explicit match is either a literal CR or LF character, or \r or \n.
1129 <pre>
1130 PCRE_INFO_JCHANGED
1131 </pre>
1132 Return 1 if the (?J) or (?-J) option setting is used in the pattern, otherwise
1133 0. The fourth argument should point to an <b>int</b> variable. (?J) and
1134 (?-J) set and unset the local PCRE_DUPNAMES option, respectively.
1135 <pre>
1136 PCRE_INFO_JIT
1137 </pre>
1138 Return 1 if the pattern was studied with the PCRE_STUDY_JIT_COMPILE option, and
1139 just-in-time compiling was successful. The fourth argument should point to an
1140 <b>int</b> variable. A return value of 0 means that JIT support is not available
1141 in this version of PCRE, or that the pattern was not studied with the
1142 PCRE_STUDY_JIT_COMPILE option, or that the JIT compiler could not handle this
1143 particular pattern. See the
1144 <a href="pcrejit.html"><b>pcrejit</b></a>
1145 documentation for details of what can and cannot be handled.
1146 <pre>
1147 PCRE_INFO_JITSIZE
1148 </pre>
1149 If the pattern was successfully studied with the PCRE_STUDY_JIT_COMPILE option,
1150 return the size of the JIT compiled code, otherwise return zero. The fourth
1151 argument should point to a <b>size_t</b> variable.
1152 <pre>
1153 PCRE_INFO_LASTLITERAL
1154 </pre>
1155 Return the value of the rightmost literal byte that must exist in any matched
1156 string, other than at its start, if such a byte has been recorded. The fourth
1157 argument should point to an <b>int</b> variable. If there is no such byte, -1 is
1158 returned. For anchored patterns, a last literal byte is recorded only if it
1159 follows something of variable length. For example, for the pattern
1160 /^a\d+z\d+/ the returned value is "z", but for /^a\dz\d/ the returned value
1161 is -1.
1162 <pre>
1163 PCRE_INFO_MINLENGTH
1164 </pre>
1165 If the pattern was studied and a minimum length for matching subject strings
1166 was computed, its value is returned. Otherwise the returned value is -1. The
1167 value is a number of characters, not bytes (this may be relevant in UTF-8
1168 mode). The fourth argument should point to an <b>int</b> variable. A
1169 non-negative value is a lower bound to the length of any matching string. There
1170 may not be any strings of that length that do actually match, but every string
1171 that does match is at least that long.
1172 <pre>
1173 PCRE_INFO_NAMECOUNT
1174 PCRE_INFO_NAMEENTRYSIZE
1175 PCRE_INFO_NAMETABLE
1176 </pre>
1177 PCRE supports the use of named as well as numbered capturing parentheses. The
1178 names are just an additional way of identifying the parentheses, which still
1179 acquire numbers. Several convenience functions such as
1180 <b>pcre_get_named_substring()</b> are provided for extracting captured
1181 substrings by name. It is also possible to extract the data directly, by first
1182 converting the name to a number in order to access the correct pointers in the
1183 output vector (described with <b>pcre_exec()</b> below). To do the conversion,
1184 you need to use the name-to-number map, which is described by these three
1185 values.
1186 </P>
1187 <P>
1188 The map consists of a number of fixed-size entries. PCRE_INFO_NAMECOUNT gives
1189 the number of entries, and PCRE_INFO_NAMEENTRYSIZE gives the size of each
1190 entry; both of these return an <b>int</b> value. The entry size depends on the
1191 length of the longest name. PCRE_INFO_NAMETABLE returns a pointer to the first
1192 entry of the table (a pointer to <b>char</b>). The first two bytes of each entry
1193 are the number of the capturing parenthesis, most significant byte first. The
1194 rest of the entry is the corresponding name, zero terminated.
1195 </P>
1196 <P>
1197 The names are in alphabetical order. Duplicate names may appear if (?| is used
1198 to create multiple groups with the same number, as described in the
1199 <a href="pcrepattern.html#dupsubpatternnumber">section on duplicate subpattern numbers</a>
1200 in the
1201 <a href="pcrepattern.html"><b>pcrepattern</b></a>
1202 page. Duplicate names for subpatterns with different numbers are permitted only
1203 if PCRE_DUPNAMES is set. In all cases of duplicate names, they appear in the
1204 table in the order in which they were found in the pattern. In the absence of
1205 (?| this is the order of increasing number; when (?| is used this is not
1206 necessarily the case because later subpatterns may have lower numbers.
1207 </P>
1208 <P>
1209 As a simple example of the name/number table, consider the following pattern
1210 (assume PCRE_EXTENDED is set, so white space - including newlines - is
1211 ignored):
1212 <pre>
1213 (?&#60;date&#62; (?&#60;year&#62;(\d\d)?\d\d) - (?&#60;month&#62;\d\d) - (?&#60;day&#62;\d\d) )
1214 </pre>
1215 There are four named subpatterns, so the table has four entries, and each entry
1216 in the table is eight bytes long. The table is as follows, with non-printing
1217 bytes shows in hexadecimal, and undefined bytes shown as ??:
1218 <pre>
1219 00 01 d a t e 00 ??
1220 00 05 d a y 00 ?? ??
1221 00 04 m o n t h 00
1222 00 02 y e a r 00 ??
1223 </pre>
1224 When writing code to extract data from named subpatterns using the
1225 name-to-number map, remember that the length of the entries is likely to be
1226 different for each compiled pattern.
1227 <pre>
1228 PCRE_INFO_OKPARTIAL
1229 </pre>
1230 Return 1 if the pattern can be used for partial matching with
1231 <b>pcre_exec()</b>, otherwise 0. The fourth argument should point to an
1232 <b>int</b> variable. From release 8.00, this always returns 1, because the
1233 restrictions that previously applied to partial matching have been lifted. The
1234 <a href="pcrepartial.html"><b>pcrepartial</b></a>
1235 documentation gives details of partial matching.
1236 <pre>
1237 PCRE_INFO_OPTIONS
1238 </pre>
1239 Return a copy of the options with which the pattern was compiled. The fourth
1240 argument should point to an <b>unsigned long int</b> variable. These option bits
1241 are those specified in the call to <b>pcre_compile()</b>, modified by any
1242 top-level option settings at the start of the pattern itself. In other words,
1243 they are the options that will be in force when matching starts. For example,
1244 if the pattern /(?im)abc(?-i)d/ is compiled with the PCRE_EXTENDED option, the
1245 result is PCRE_CASELESS, PCRE_MULTILINE, and PCRE_EXTENDED.
1246 </P>
1247 <P>
1248 A pattern is automatically anchored by PCRE if all of its top-level
1249 alternatives begin with one of the following:
1250 <pre>
1251 ^ unless PCRE_MULTILINE is set
1252 \A always
1253 \G always
1254 .* if PCRE_DOTALL is set and there are no back references to the subpattern in which .* appears
1255 </pre>
1256 For such patterns, the PCRE_ANCHORED bit is set in the options returned by
1257 <b>pcre_fullinfo()</b>.
1258 <pre>
1259 PCRE_INFO_SIZE
1260 </pre>
1261 Return the size of the compiled pattern. The fourth argument should point to a
1262 <b>size_t</b> variable. This value does not include the size of the <b>pcre</b>
1263 structure that is returned by <b>pcre_compile()</b>. The value that is passed as
1264 the argument to <b>pcre_malloc()</b> when <b>pcre_compile()</b> is getting memory
1265 in which to place the compiled data is the value returned by this option plus
1266 the size of the <b>pcre</b> structure. Studying a compiled pattern, with or
1267 without JIT, does not alter the value returned by this option.
1268 <pre>
1269 PCRE_INFO_STUDYSIZE
1270 </pre>
1271 Return the size of the data block pointed to by the <i>study_data</i> field in a
1272 <b>pcre_extra</b> block. If <b>pcre_extra</b> is NULL, or there is no study data,
1273 zero is returned. The fourth argument should point to a <b>size_t</b> variable.
1274 The <i>study_data</i> field is set by <b>pcre_study()</b> to record information
1275 that will speed up matching (see the section entitled
1276 <a href="#studyingapattern">"Studying a pattern"</a>
1277 above). The format of the <i>study_data</i> block is private, but its length
1278 is made available via this option so that it can be saved and restored (see the
1279 <a href="pcreprecompile.html"><b>pcreprecompile</b></a>
1280 documentation for details).
1281 </P>
1282 <br><a name="SEC14" href="#TOC1">OBSOLETE INFO FUNCTION</a><br>
1283 <P>
1284 <b>int pcre_info(const pcre *<i>code</i>, int *<i>optptr</i>, int</b>
1285 <b>*<i>firstcharptr</i>);</b>
1286 </P>
1287 <P>
1288 The <b>pcre_info()</b> function is now obsolete because its interface is too
1289 restrictive to return all the available data about a compiled pattern. New
1290 programs should use <b>pcre_fullinfo()</b> instead. The yield of
1291 <b>pcre_info()</b> is the number of capturing subpatterns, or one of the
1292 following negative numbers:
1293 <pre>
1294 PCRE_ERROR_NULL the argument <i>code</i> was NULL
1295 PCRE_ERROR_BADMAGIC the "magic number" was not found
1296 </pre>
1297 If the <i>optptr</i> argument is not NULL, a copy of the options with which the
1298 pattern was compiled is placed in the integer it points to (see
1299 PCRE_INFO_OPTIONS above).
1300 </P>
1301 <P>
1302 If the pattern is not anchored and the <i>firstcharptr</i> argument is not NULL,
1303 it is used to pass back information about the first character of any matched
1304 string (see PCRE_INFO_FIRSTBYTE above).
1305 </P>
1306 <br><a name="SEC15" href="#TOC1">REFERENCE COUNTS</a><br>
1307 <P>
1308 <b>int pcre_refcount(pcre *<i>code</i>, int <i>adjust</i>);</b>
1309 </P>
1310 <P>
1311 The <b>pcre_refcount()</b> function is used to maintain a reference count in the
1312 data block that contains a compiled pattern. It is provided for the benefit of
1313 applications that operate in an object-oriented manner, where different parts
1314 of the application may be using the same compiled pattern, but you want to free
1315 the block when they are all done.
1316 </P>
1317 <P>
1318 When a pattern is compiled, the reference count field is initialized to zero.
1319 It is changed only by calling this function, whose action is to add the
1320 <i>adjust</i> value (which may be positive or negative) to it. The yield of the
1321 function is the new value. However, the value of the count is constrained to
1322 lie between 0 and 65535, inclusive. If the new value is outside these limits,
1323 it is forced to the appropriate limit value.
1324 </P>
1325 <P>
1326 Except when it is zero, the reference count is not correctly preserved if a
1327 pattern is compiled on one host and then transferred to a host whose byte-order
1328 is different. (This seems a highly unlikely scenario.)
1329 </P>
1330 <br><a name="SEC16" href="#TOC1">MATCHING A PATTERN: THE TRADITIONAL FUNCTION</a><br>
1331 <P>
1332 <b>int pcre_exec(const pcre *<i>code</i>, const pcre_extra *<i>extra</i>,</b>
1333 <b>const char *<i>subject</i>, int <i>length</i>, int <i>startoffset</i>,</b>
1334 <b>int <i>options</i>, int *<i>ovector</i>, int <i>ovecsize</i>);</b>
1335 </P>
1336 <P>
1337 The function <b>pcre_exec()</b> is called to match a subject string against a
1338 compiled pattern, which is passed in the <i>code</i> argument. If the
1339 pattern was studied, the result of the study should be passed in the
1340 <i>extra</i> argument. You can call <b>pcre_exec()</b> with the same <i>code</i>
1341 and <i>extra</i> arguments as many times as you like, in order to match
1342 different subject strings with the same pattern.
1343 </P>
1344 <P>
1345 This function is the main matching facility of the library, and it operates in
1346 a Perl-like manner. For specialist use there is also an alternative matching
1347 function, which is described
1348 <a href="#dfamatch">below</a>
1349 in the section about the <b>pcre_dfa_exec()</b> function.
1350 </P>
1351 <P>
1352 In most applications, the pattern will have been compiled (and optionally
1353 studied) in the same process that calls <b>pcre_exec()</b>. However, it is
1354 possible to save compiled patterns and study data, and then use them later
1355 in different processes, possibly even on different hosts. For a discussion
1356 about this, see the
1357 <a href="pcreprecompile.html"><b>pcreprecompile</b></a>
1358 documentation.
1359 </P>
1360 <P>
1361 Here is an example of a simple call to <b>pcre_exec()</b>:
1362 <pre>
1363 int rc;
1364 int ovector[30];
1365 rc = pcre_exec(
1366 re, /* result of pcre_compile() */
1367 NULL, /* we didn't study the pattern */
1368 "some string", /* the subject string */
1369 11, /* the length of the subject string */
1370 0, /* start at offset 0 in the subject */
1371 0, /* default options */
1372 ovector, /* vector of integers for substring information */
1373 30); /* number of elements (NOT size in bytes) */
1374 <a name="extradata"></a></PRE>
1375 </P>
1376 <br><b>
1377 Extra data for <b>pcre_exec()</b>
1378 </b><br>
1379 <P>
1380 If the <i>extra</i> argument is not NULL, it must point to a <b>pcre_extra</b>
1381 data block. The <b>pcre_study()</b> function returns such a block (when it
1382 doesn't return NULL), but you can also create one for yourself, and pass
1383 additional information in it. The <b>pcre_extra</b> block contains the following
1384 fields (not necessarily in this order):
1385 <pre>
1386 unsigned long int <i>flags</i>;
1387 void *<i>study_data</i>;
1388 void *<i>executable_jit</i>;
1389 unsigned long int <i>match_limit</i>;
1390 unsigned long int <i>match_limit_recursion</i>;
1391 void *<i>callout_data</i>;
1392 const unsigned char *<i>tables</i>;
1393 unsigned char **<i>mark</i>;
1394 </pre>
1395 The <i>flags</i> field is a bitmap that specifies which of the other fields
1396 are set. The flag bits are:
1397 <pre>
1398 PCRE_EXTRA_STUDY_DATA
1399 PCRE_EXTRA_EXECUTABLE_JIT
1400 PCRE_EXTRA_MATCH_LIMIT
1401 PCRE_EXTRA_MATCH_LIMIT_RECURSION
1402 PCRE_EXTRA_CALLOUT_DATA
1403 PCRE_EXTRA_TABLES
1404 PCRE_EXTRA_MARK
1405 </pre>
1406 Other flag bits should be set to zero. The <i>study_data</i> field and sometimes
1407 the <i>executable_jit</i> field are set in the <b>pcre_extra</b> block that is
1408 returned by <b>pcre_study()</b>, together with the appropriate flag bits. You
1409 should not set these yourself, but you may add to the block by setting the
1410 other fields and their corresponding flag bits.
1411 </P>
1412 <P>
1413 The <i>match_limit</i> field provides a means of preventing PCRE from using up a
1414 vast amount of resources when running patterns that are not going to match,
1415 but which have a very large number of possibilities in their search trees. The
1416 classic example is a pattern that uses nested unlimited repeats.
1417 </P>
1418 <P>
1419 Internally, <b>pcre_exec()</b> uses a function called <b>match()</b>, which it
1420 calls repeatedly (sometimes recursively). The limit set by <i>match_limit</i> is
1421 imposed on the number of times this function is called during a match, which
1422 has the effect of limiting the amount of backtracking that can take place. For
1423 patterns that are not anchored, the count restarts from zero for each position
1424 in the subject string.
1425 </P>
1426 <P>
1427 When <b>pcre_exec()</b> is called with a pattern that was successfully studied
1428 with the PCRE_STUDY_JIT_COMPILE option, the way that the matching is executed
1429 is entirely different. However, there is still the possibility of runaway
1430 matching that goes on for a very long time, and so the <i>match_limit</i> value
1431 is also used in this case (but in a different way) to limit how long the
1432 matching can continue.
1433 </P>
1434 <P>
1435 The default value for the limit can be set when PCRE is built; the default
1436 default is 10 million, which handles all but the most extreme cases. You can
1437 override the default by suppling <b>pcre_exec()</b> with a <b>pcre_extra</b>
1438 block in which <i>match_limit</i> is set, and PCRE_EXTRA_MATCH_LIMIT is set in
1439 the <i>flags</i> field. If the limit is exceeded, <b>pcre_exec()</b> returns
1440 PCRE_ERROR_MATCHLIMIT.
1441 </P>
1442 <P>
1443 The <i>match_limit_recursion</i> field is similar to <i>match_limit</i>, but
1444 instead of limiting the total number of times that <b>match()</b> is called, it
1445 limits the depth of recursion. The recursion depth is a smaller number than the
1446 total number of calls, because not all calls to <b>match()</b> are recursive.
1447 This limit is of use only if it is set smaller than <i>match_limit</i>.
1448 </P>
1449 <P>
1450 Limiting the recursion depth limits the amount of machine stack that can be
1451 used, or, when PCRE has been compiled to use memory on the heap instead of the
1452 stack, the amount of heap memory that can be used. This limit is not relevant,
1453 and is ignored, if the pattern was successfully studied with
1454 PCRE_STUDY_JIT_COMPILE.
1455 </P>
1456 <P>
1457 The default value for <i>match_limit_recursion</i> can be set when PCRE is
1458 built; the default default is the same value as the default for
1459 <i>match_limit</i>. You can override the default by suppling <b>pcre_exec()</b>
1460 with a <b>pcre_extra</b> block in which <i>match_limit_recursion</i> is set, and
1461 PCRE_EXTRA_MATCH_LIMIT_RECURSION is set in the <i>flags</i> field. If the limit
1462 is exceeded, <b>pcre_exec()</b> returns PCRE_ERROR_RECURSIONLIMIT.
1463 </P>
1464 <P>
1465 The <i>callout_data</i> field is used in conjunction with the "callout" feature,
1466 and is described in the
1467 <a href="pcrecallout.html"><b>pcrecallout</b></a>
1468 documentation.
1469 </P>
1470 <P>
1471 The <i>tables</i> field is used to pass a character tables pointer to
1472 <b>pcre_exec()</b>; this overrides the value that is stored with the compiled
1473 pattern. A non-NULL value is stored with the compiled pattern only if custom
1474 tables were supplied to <b>pcre_compile()</b> via its <i>tableptr</i> argument.
1475 If NULL is passed to <b>pcre_exec()</b> using this mechanism, it forces PCRE's
1476 internal tables to be used. This facility is helpful when re-using patterns
1477 that have been saved after compiling with an external set of tables, because
1478 the external tables might be at a different address when <b>pcre_exec()</b> is
1479 called. See the
1480 <a href="pcreprecompile.html"><b>pcreprecompile</b></a>
1481 documentation for a discussion of saving compiled patterns for later use.
1482 </P>
1483 <P>
1484 If PCRE_EXTRA_MARK is set in the <i>flags</i> field, the <i>mark</i> field must
1485 be set to point to a <b>char *</b> variable. If the pattern contains any
1486 backtracking control verbs such as (*MARK:NAME), and the execution ends up with
1487 a name to pass back, a pointer to the name string (zero terminated) is placed
1488 in the variable pointed to by the <i>mark</i> field. The names are within the
1489 compiled pattern; if you wish to retain such a name you must copy it before
1490 freeing the memory of a compiled pattern. If there is no name to pass back, the
1491 variable pointed to by the <i>mark</i> field set to NULL. For details of the
1492 backtracking control verbs, see the section entitled
1493 <a href="pcrepattern#backtrackcontrol">"Backtracking control"</a>
1494 in the
1495 <a href="pcrepattern.html"><b>pcrepattern</b></a>
1496 documentation.
1497 <a name="execoptions"></a></P>
1498 <br><b>
1499 Option bits for <b>pcre_exec()</b>
1500 </b><br>
1501 <P>
1502 The unused bits of the <i>options</i> argument for <b>pcre_exec()</b> must be
1503 zero. The only bits that may be set are PCRE_ANCHORED, PCRE_NEWLINE_<i>xxx</i>,
1504 PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY, PCRE_NOTEMPTY_ATSTART,
1505 PCRE_NO_START_OPTIMIZE, PCRE_NO_UTF8_CHECK, PCRE_PARTIAL_SOFT, and
1506 PCRE_PARTIAL_HARD.
1507 </P>
1508 <P>
1509 If the pattern was successfully studied with the PCRE_STUDY_JIT_COMPILE option,
1510 the only supported options for JIT execution are PCRE_NO_UTF8_CHECK,
1511 PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY, and PCRE_NOTEMPTY_ATSTART. Note in
1512 particular that partial matching is not supported. If an unsupported option is
1513 used, JIT execution is disabled and the normal interpretive code in
1514 <b>pcre_exec()</b> is run.
1515 <pre>
1516 PCRE_ANCHORED
1517 </pre>
1518 The PCRE_ANCHORED option limits <b>pcre_exec()</b> to matching at the first
1519 matching position. If a pattern was compiled with PCRE_ANCHORED, or turned out
1520 to be anchored by virtue of its contents, it cannot be made unachored at
1521 matching time.
1522 <pre>
1523 PCRE_BSR_ANYCRLF
1524 PCRE_BSR_UNICODE
1525 </pre>
1526 These options (which are mutually exclusive) control what the \R escape
1527 sequence matches. The choice is either to match only CR, LF, or CRLF, or to
1528 match any Unicode newline sequence. These options override the choice that was
1529 made or defaulted when the pattern was compiled.
1530 <pre>
1531 PCRE_NEWLINE_CR
1532 PCRE_NEWLINE_LF
1533 PCRE_NEWLINE_CRLF
1534 PCRE_NEWLINE_ANYCRLF
1535 PCRE_NEWLINE_ANY
1536 </pre>
1537 These options override the newline definition that was chosen or defaulted when
1538 the pattern was compiled. For details, see the description of
1539 <b>pcre_compile()</b> above. During matching, the newline choice affects the
1540 behaviour of the dot, circumflex, and dollar metacharacters. It may also alter
1541 the way the match position is advanced after a match failure for an unanchored
1542 pattern.
1543 </P>
1544 <P>
1545 When PCRE_NEWLINE_CRLF, PCRE_NEWLINE_ANYCRLF, or PCRE_NEWLINE_ANY is set, and a
1546 match attempt for an unanchored pattern fails when the current position is at a
1547 CRLF sequence, and the pattern contains no explicit matches for CR or LF
1548 characters, the match position is advanced by two characters instead of one, in
1549 other words, to after the CRLF.
1550 </P>
1551 <P>
1552 The above rule is a compromise that makes the most common cases work as
1553 expected. For example, if the pattern is .+A (and the PCRE_DOTALL option is not
1554 set), it does not match the string "\r\nA" because, after failing at the
1555 start, it skips both the CR and the LF before retrying. However, the pattern
1556 [\r\n]A does match that string, because it contains an explicit CR or LF
1557 reference, and so advances only by one character after the first failure.
1558 </P>
1559 <P>
1560 An explicit match for CR of LF is either a literal appearance of one of those
1561 characters, or one of the \r or \n escape sequences. Implicit matches such as
1562 [^X] do not count, nor does \s (which includes CR and LF in the characters
1563 that it matches).
1564 </P>
1565 <P>
1566 Notwithstanding the above, anomalous effects may still occur when CRLF is a
1567 valid newline sequence and explicit \r or \n escapes appear in the pattern.
1568 <pre>
1569 PCRE_NOTBOL
1570 </pre>
1571 This option specifies that first character of the subject string is not the
1572 beginning of a line, so the circumflex metacharacter should not match before
1573 it. Setting this without PCRE_MULTILINE (at compile time) causes circumflex
1574 never to match. This option affects only the behaviour of the circumflex
1575 metacharacter. It does not affect \A.
1576 <pre>
1577 PCRE_NOTEOL
1578 </pre>
1579 This option specifies that the end of the subject string is not the end of a
1580 line, so the dollar metacharacter should not match it nor (except in multiline
1581 mode) a newline immediately before it. Setting this without PCRE_MULTILINE (at
1582 compile time) causes dollar never to match. This option affects only the
1583 behaviour of the dollar metacharacter. It does not affect \Z or \z.
1584 <pre>
1585 PCRE_NOTEMPTY
1586 </pre>
1587 An empty string is not considered to be a valid match if this option is set. If
1588 there are alternatives in the pattern, they are tried. If all the alternatives
1589 match the empty string, the entire match fails. For example, if the pattern
1590 <pre>
1591 a?b?
1592 </pre>
1593 is applied to a string not beginning with "a" or "b", it matches an empty
1594 string at the start of the subject. With PCRE_NOTEMPTY set, this match is not
1595 valid, so PCRE searches further into the string for occurrences of "a" or "b".
1596 <pre>
1597 PCRE_NOTEMPTY_ATSTART
1598 </pre>
1599 This is like PCRE_NOTEMPTY, except that an empty string match that is not at
1600 the start of the subject is permitted. If the pattern is anchored, such a match
1601 can occur only if the pattern contains \K.
1602 </P>
1603 <P>
1604 Perl has no direct equivalent of PCRE_NOTEMPTY or PCRE_NOTEMPTY_ATSTART, but it
1605 does make a special case of a pattern match of the empty string within its
1606 <b>split()</b> function, and when using the /g modifier. It is possible to
1607 emulate Perl's behaviour after matching a null string by first trying the match
1608 again at the same offset with PCRE_NOTEMPTY_ATSTART and PCRE_ANCHORED, and then
1609 if that fails, by advancing the starting offset (see below) and trying an
1610 ordinary match again. There is some code that demonstrates how to do this in
1611 the
1612 <a href="pcredemo.html"><b>pcredemo</b></a>
1613 sample program. In the most general case, you have to check to see if the
1614 newline convention recognizes CRLF as a newline, and if so, and the current
1615 character is CR followed by LF, advance the starting offset by two characters
1616 instead of one.
1617 <pre>
1618 PCRE_NO_START_OPTIMIZE
1619 </pre>
1620 There are a number of optimizations that <b>pcre_exec()</b> uses at the start of
1621 a match, in order to speed up the process. For example, if it is known that an
1622 unanchored match must start with a specific character, it searches the subject
1623 for that character, and fails immediately if it cannot find it, without
1624 actually running the main matching function. This means that a special item
1625 such as (*COMMIT) at the start of a pattern is not considered until after a
1626 suitable starting point for the match has been found. When callouts or (*MARK)
1627 items are in use, these "start-up" optimizations can cause them to be skipped
1628 if the pattern is never actually used. The start-up optimizations are in effect
1629 a pre-scan of the subject that takes place before the pattern is run.
1630 </P>
1631 <P>
1632 The PCRE_NO_START_OPTIMIZE option disables the start-up optimizations, possibly
1633 causing performance to suffer, but ensuring that in cases where the result is
1634 "no match", the callouts do occur, and that items such as (*COMMIT) and (*MARK)
1635 are considered at every possible starting position in the subject string. If
1636 PCRE_NO_START_OPTIMIZE is set at compile time, it cannot be unset at matching
1637 time.
1638 </P>
1639 <P>
1640 Setting PCRE_NO_START_OPTIMIZE can change the outcome of a matching operation.
1641 Consider the pattern
1642 <pre>
1643 (*COMMIT)ABC
1644 </pre>
1645 When this is compiled, PCRE records the fact that a match must start with the
1646 character "A". Suppose the subject string is "DEFABC". The start-up
1647 optimization scans along the subject, finds "A" and runs the first match
1648 attempt from there. The (*COMMIT) item means that the pattern must match the
1649 current starting position, which in this case, it does. However, if the same
1650 match is run with PCRE_NO_START_OPTIMIZE set, the initial scan along the
1651 subject string does not happen. The first match attempt is run starting from
1652 "D" and when this fails, (*COMMIT) prevents any further matches being tried, so
1653 the overall result is "no match". If the pattern is studied, more start-up
1654 optimizations may be used. For example, a minimum length for the subject may be
1655 recorded. Consider the pattern
1656 <pre>
1657 (*MARK:A)(X|Y)
1658 </pre>
1659 The minimum length for a match is one character. If the subject is "ABC", there
1660 will be attempts to match "ABC", "BC", "C", and then finally an empty string.
1661 If the pattern is studied, the final attempt does not take place, because PCRE
1662 knows that the subject is too short, and so the (*MARK) is never encountered.
1663 In this case, studying the pattern does not affect the overall match result,
1664 which is still "no match", but it does affect the auxiliary information that is
1665 returned.
1666 <pre>
1667 PCRE_NO_UTF8_CHECK
1668 </pre>
1669 When PCRE_UTF8 is set at compile time, the validity of the subject as a UTF-8
1670 string is automatically checked when <b>pcre_exec()</b> is subsequently called.
1671 The value of <i>startoffset</i> is also checked to ensure that it points to the
1672 start of a UTF-8 character. There is a discussion about the validity of UTF-8
1673 strings in the
1674 <a href="pcre.html#utf8strings">section on UTF-8 support</a>
1675 in the main
1676 <a href="pcre.html"><b>pcre</b></a>
1677 page. If an invalid UTF-8 sequence of bytes is found, <b>pcre_exec()</b> returns
1678 the error PCRE_ERROR_BADUTF8 or, if PCRE_PARTIAL_HARD is set and the problem is
1679 a truncated UTF-8 character at the end of the subject, PCRE_ERROR_SHORTUTF8. In
1680 both cases, information about the precise nature of the error may also be
1681 returned (see the descriptions of these errors in the section entitled \fIError
1682 return values from\fP <b>pcre_exec()</b>
1683 <a href="#errorlist">below).</a>
1684 If <i>startoffset</i> contains a value that does not point to the start of a
1685 UTF-8 character (or to the end of the subject), PCRE_ERROR_BADUTF8_OFFSET is
1686 returned.
1687 </P>
1688 <P>
1689 If you already know that your subject is valid, and you want to skip these
1690 checks for performance reasons, you can set the PCRE_NO_UTF8_CHECK option when
1691 calling <b>pcre_exec()</b>. You might want to do this for the second and
1692 subsequent calls to <b>pcre_exec()</b> if you are making repeated calls to find
1693 all the matches in a single subject string. However, you should be sure that
1694 the value of <i>startoffset</i> points to the start of a UTF-8 character (or the
1695 end of the subject). When PCRE_NO_UTF8_CHECK is set, the effect of passing an
1696 invalid UTF-8 string as a subject or an invalid value of <i>startoffset</i> is
1697 undefined. Your program may crash.
1698 <pre>
1699 PCRE_PARTIAL_HARD
1700 PCRE_PARTIAL_SOFT
1701 </pre>
1702 These options turn on the partial matching feature. For backwards
1703 compatibility, PCRE_PARTIAL is a synonym for PCRE_PARTIAL_SOFT. A partial match
1704 occurs if the end of the subject string is reached successfully, but there are
1705 not enough subject characters to complete the match. If this happens when
1706 PCRE_PARTIAL_SOFT (but not PCRE_PARTIAL_HARD) is set, matching continues by
1707 testing any remaining alternatives. Only if no complete match can be found is
1708 PCRE_ERROR_PARTIAL returned instead of PCRE_ERROR_NOMATCH. In other words,
1709 PCRE_PARTIAL_SOFT says that the caller is prepared to handle a partial match,
1710 but only if no complete match can be found.
1711 </P>
1712 <P>
1713 If PCRE_PARTIAL_HARD is set, it overrides PCRE_PARTIAL_SOFT. In this case, if a
1714 partial match is found, <b>pcre_exec()</b> immediately returns
1715 PCRE_ERROR_PARTIAL, without considering any other alternatives. In other words,
1716 when PCRE_PARTIAL_HARD is set, a partial match is considered to be more
1717 important that an alternative complete match.
1718 </P>
1719 <P>
1720 In both cases, the portion of the string that was inspected when the partial
1721 match was found is set as the first matching string. There is a more detailed
1722 discussion of partial and multi-segment matching, with examples, in the
1723 <a href="pcrepartial.html"><b>pcrepartial</b></a>
1724 documentation.
1725 </P>
1726 <br><b>
1727 The string to be matched by <b>pcre_exec()</b>
1728 </b><br>
1729 <P>
1730 The subject string is passed to <b>pcre_exec()</b> as a pointer in
1731 <i>subject</i>, a length (in bytes) in <i>length</i>, and a starting byte offset
1732 in <i>startoffset</i>. If this is negative or greater than the length of the
1733 subject, <b>pcre_exec()</b> returns PCRE_ERROR_BADOFFSET. When the starting
1734 offset is zero, the search for a match starts at the beginning of the subject,
1735 and this is by far the most common case. In UTF-8 mode, the byte offset must
1736 point to the start of a UTF-8 character (or the end of the subject). Unlike the
1737 pattern string, the subject may contain binary zero bytes.
1738 </P>
1739 <P>
1740 A non-zero starting offset is useful when searching for another match in the
1741 same subject by calling <b>pcre_exec()</b> again after a previous success.
1742 Setting <i>startoffset</i> differs from just passing over a shortened string and
1743 setting PCRE_NOTBOL in the case of a pattern that begins with any kind of
1744 lookbehind. For example, consider the pattern
1745 <pre>
1746 \Biss\B
1747 </pre>
1748 which finds occurrences of "iss" in the middle of words. (\B matches only if
1749 the current position in the subject is not a word boundary.) When applied to
1750 the string "Mississipi" the first call to <b>pcre_exec()</b> finds the first
1751 occurrence. If <b>pcre_exec()</b> is called again with just the remainder of the
1752 subject, namely "issipi", it does not match, because \B is always false at the
1753 start of the subject, which is deemed to be a word boundary. However, if
1754 <b>pcre_exec()</b> is passed the entire string again, but with <i>startoffset</i>
1755 set to 4, it finds the second occurrence of "iss" because it is able to look
1756 behind the starting point to discover that it is preceded by a letter.
1757 </P>
1758 <P>
1759 Finding all the matches in a subject is tricky when the pattern can match an
1760 empty string. It is possible to emulate Perl's /g behaviour by first trying the
1761 match again at the same offset, with the PCRE_NOTEMPTY_ATSTART and
1762 PCRE_ANCHORED options, and then if that fails, advancing the starting offset
1763 and trying an ordinary match again. There is some code that demonstrates how to
1764 do this in the
1765 <a href="pcredemo.html"><b>pcredemo</b></a>
1766 sample program. In the most general case, you have to check to see if the
1767 newline convention recognizes CRLF as a newline, and if so, and the current
1768 character is CR followed by LF, advance the starting offset by two characters
1769 instead of one.
1770 </P>
1771 <P>
1772 If a non-zero starting offset is passed when the pattern is anchored, one
1773 attempt to match at the given offset is made. This can only succeed if the
1774 pattern does not require the match to be at the start of the subject.
1775 </P>
1776 <br><b>
1777 How <b>pcre_exec()</b> returns captured substrings
1778 </b><br>
1779 <P>
1780 In general, a pattern matches a certain portion of the subject, and in
1781 addition, further substrings from the subject may be picked out by parts of the
1782 pattern. Following the usage in Jeffrey Friedl's book, this is called
1783 "capturing" in what follows, and the phrase "capturing subpattern" is used for
1784 a fragment of a pattern that picks out a substring. PCRE supports several other
1785 kinds of parenthesized subpattern that do not cause substrings to be captured.
1786 </P>
1787 <P>
1788 Captured substrings are returned to the caller via a vector of integers whose
1789 address is passed in <i>ovector</i>. The number of elements in the vector is
1790 passed in <i>ovecsize</i>, which must be a non-negative number. <b>Note</b>: this
1791 argument is NOT the size of <i>ovector</i> in bytes.
1792 </P>
1793 <P>
1794 The first two-thirds of the vector is used to pass back captured substrings,
1795 each substring using a pair of integers. The remaining third of the vector is
1796 used as workspace by <b>pcre_exec()</b> while matching capturing subpatterns,
1797 and is not available for passing back information. The number passed in
1798 <i>ovecsize</i> should always be a multiple of three. If it is not, it is
1799 rounded down.
1800 </P>
1801 <P>
1802 When a match is successful, information about captured substrings is returned
1803 in pairs of integers, starting at the beginning of <i>ovector</i>, and
1804 continuing up to two-thirds of its length at the most. The first element of
1805 each pair is set to the byte offset of the first character in a substring, and
1806 the second is set to the byte offset of the first character after the end of a
1807 substring. <b>Note</b>: these values are always byte offsets, even in UTF-8
1808 mode. They are not character counts.
1809 </P>
1810 <P>
1811 The first pair of integers, <i>ovector[0]</i> and <i>ovector[1]</i>, identify the
1812 portion of the subject string matched by the entire pattern. The next pair is
1813 used for the first capturing subpattern, and so on. The value returned by
1814 <b>pcre_exec()</b> is one more than the highest numbered pair that has been set.
1815 For example, if two substrings have been captured, the returned value is 3. If
1816 there are no capturing subpatterns, the return value from a successful match is
1817 1, indicating that just the first pair of offsets has been set.
1818 </P>
1819 <P>
1820 If a capturing subpattern is matched repeatedly, it is the last portion of the
1821 string that it matched that is returned.
1822 </P>
1823 <P>
1824 If the vector is too small to hold all the captured substring offsets, it is
1825 used as far as possible (up to two-thirds of its length), and the function
1826 returns a value of zero. If neither the actual string matched not any captured
1827 substrings are of interest, <b>pcre_exec()</b> may be called with <i>ovector</i>
1828 passed as NULL and <i>ovecsize</i> as zero. However, if the pattern contains
1829 back references and the <i>ovector</i> is not big enough to remember the related
1830 substrings, PCRE has to get additional memory for use during matching. Thus it
1831 is usually advisable to supply an <i>ovector</i> of reasonable size.
1832 </P>
1833 <P>
1834 There are some cases where zero is returned (indicating vector overflow) when
1835 in fact the vector is exactly the right size for the final match. For example,
1836 consider the pattern
1837 <pre>
1838 (a)(?:(b)c|bd)
1839 </pre>
1840 If a vector of 6 elements (allowing for only 1 captured substring) is given
1841 with subject string "abd", <b>pcre_exec()</b> will try to set the second
1842 captured string, thereby recording a vector overflow, before failing to match
1843 "c" and backing up to try the second alternative. The zero return, however,
1844 does correctly indicate that the maximum number of slots (namely 2) have been
1845 filled. In similar cases where there is temporary overflow, but the final
1846 number of used slots is actually less than the maximum, a non-zero value is
1847 returned.
1848 </P>
1849 <P>
1850 The <b>pcre_fullinfo()</b> function can be used to find out how many capturing
1851 subpatterns there are in a compiled pattern. The smallest size for
1852 <i>ovector</i> that will allow for <i>n</i> captured substrings, in addition to
1853 the offsets of the substring matched by the whole pattern, is (<i>n</i>+1)*3.
1854 </P>
1855 <P>
1856 It is possible for capturing subpattern number <i>n+1</i> to match some part of
1857 the subject when subpattern <i>n</i> has not been used at all. For example, if
1858 the string "abc" is matched against the pattern (a|(z))(bc) the return from the
1859 function is 4, and subpatterns 1 and 3 are matched, but 2 is not. When this
1860 happens, both values in the offset pairs corresponding to unused subpatterns
1861 are set to -1.
1862 </P>
1863 <P>
1864 Offset values that correspond to unused subpatterns at the end of the
1865 expression are also set to -1. For example, if the string "abc" is matched
1866 against the pattern (abc)(x(yz)?)? subpatterns 2 and 3 are not matched. The
1867 return from the function is 2, because the highest used capturing subpattern
1868 number is 1, and the offsets for for the second and third capturing subpatterns
1869 (assuming the vector is large enough, of course) are set to -1.
1870 </P>
1871 <P>
1872 <b>Note</b>: Elements in the first two-thirds of <i>ovector</i> that do not
1873 correspond to capturing parentheses in the pattern are never changed. That is,
1874 if a pattern contains <i>n</i> capturing parentheses, no more than
1875 <i>ovector[0]</i> to <i>ovector[2n+1]</i> are set by <b>pcre_exec()</b>. The other
1876 elements (in the first two-thirds) retain whatever values they previously had.
1877 </P>
1878 <P>
1879 Some convenience functions are provided for extracting the captured substrings
1880 as separate strings. These are described below.
1881 <a name="errorlist"></a></P>
1882 <br><b>
1883 Error return values from <b>pcre_exec()</b>
1884 </b><br>
1885 <P>
1886 If <b>pcre_exec()</b> fails, it returns a negative number. The following are
1887 defined in the header file:
1888 <pre>
1889 PCRE_ERROR_NOMATCH (-1)
1890 </pre>
1891 The subject string did not match the pattern.
1892 <pre>
1893 PCRE_ERROR_NULL (-2)
1894 </pre>
1895 Either <i>code</i> or <i>subject</i> was passed as NULL, or <i>ovector</i> was
1896 NULL and <i>ovecsize</i> was not zero.
1897 <pre>
1898 PCRE_ERROR_BADOPTION (-3)
1899 </pre>
1900 An unrecognized bit was set in the <i>options</i> argument.
1901 <pre>
1902 PCRE_ERROR_BADMAGIC (-4)
1903 </pre>
1904 PCRE stores a 4-byte "magic number" at the start of the compiled code, to catch
1905 the case when it is passed a junk pointer and to detect when a pattern that was
1906 compiled in an environment of one endianness is run in an environment with the
1907 other endianness. This is the error that PCRE gives when the magic number is
1908 not present.
1909 <pre>
1910 PCRE_ERROR_UNKNOWN_OPCODE (-5)
1911 </pre>
1912 While running the pattern match, an unknown item was encountered in the
1913 compiled pattern. This error could be caused by a bug in PCRE or by overwriting
1914 of the compiled pattern.
1915 <pre>
1916 PCRE_ERROR_NOMEMORY (-6)
1917 </pre>
1918 If a pattern contains back references, but the <i>ovector</i> that is passed to
1919 <b>pcre_exec()</b> is not big enough to remember the referenced substrings, PCRE
1920 gets a block of memory at the start of matching to use for this purpose. If the
1921 call via <b>pcre_malloc()</b> fails, this error is given. The memory is
1922 automatically freed at the end of matching.
1923 </P>
1924 <P>
1925 This error is also given if <b>pcre_stack_malloc()</b> fails in
1926 <b>pcre_exec()</b>. This can happen only when PCRE has been compiled with
1927 <b>--disable-stack-for-recursion</b>.
1928 <pre>
1929 PCRE_ERROR_NOSUBSTRING (-7)
1930 </pre>
1931 This error is used by the <b>pcre_copy_substring()</b>,
1932 <b>pcre_get_substring()</b>, and <b>pcre_get_substring_list()</b> functions (see
1933 below). It is never returned by <b>pcre_exec()</b>.
1934 <pre>
1935 PCRE_ERROR_MATCHLIMIT (-8)
1936 </pre>
1937 The backtracking limit, as specified by the <i>match_limit</i> field in a
1938 <b>pcre_extra</b> structure (or defaulted) was reached. See the description
1939 above.
1940 <pre>
1941 PCRE_ERROR_CALLOUT (-9)
1942 </pre>
1943 This error is never generated by <b>pcre_exec()</b> itself. It is provided for
1944 use by callout functions that want to yield a distinctive error code. See the
1945 <a href="pcrecallout.html"><b>pcrecallout</b></a>
1946 documentation for details.
1947 <pre>
1948 PCRE_ERROR_BADUTF8 (-10)
1949 </pre>
1950 A string that contains an invalid UTF-8 byte sequence was passed as a subject,
1951 and the PCRE_NO_UTF8_CHECK option was not set. If the size of the output vector
1952 (<i>ovecsize</i>) is at least 2, the byte offset to the start of the the invalid
1953 UTF-8 character is placed in the first element, and a reason code is placed in
1954 the second element. The reason codes are listed in the
1955 <a href="#badutf8reasons">following section.</a>
1956 For backward compatibility, if PCRE_PARTIAL_HARD is set and the problem is a
1957 truncated UTF-8 character at the end of the subject (reason codes 1 to 5),
1958 PCRE_ERROR_SHORTUTF8 is returned instead of PCRE_ERROR_BADUTF8.
1959 <pre>
1960 PCRE_ERROR_BADUTF8_OFFSET (-11)
1961 </pre>
1962 The UTF-8 byte sequence that was passed as a subject was checked and found to
1963 be valid (the PCRE_NO_UTF8_CHECK option was not set), but the value of
1964 <i>startoffset</i> did not point to the beginning of a UTF-8 character or the
1965 end of the subject.
1966 <pre>
1967 PCRE_ERROR_PARTIAL (-12)
1968 </pre>
1969 The subject string did not match, but it did match partially. See the
1970 <a href="pcrepartial.html"><b>pcrepartial</b></a>
1971 documentation for details of partial matching.
1972 <pre>
1973 PCRE_ERROR_BADPARTIAL (-13)
1974 </pre>
1975 This code is no longer in use. It was formerly returned when the PCRE_PARTIAL
1976 option was used with a compiled pattern containing items that were not
1977 supported for partial matching. From release 8.00 onwards, there are no
1978 restrictions on partial matching.
1979 <pre>
1980 PCRE_ERROR_INTERNAL (-14)
1981 </pre>
1982 An unexpected internal error has occurred. This error could be caused by a bug
1983 in PCRE or by overwriting of the compiled pattern.
1984 <pre>
1985 PCRE_ERROR_BADCOUNT (-15)
1986 </pre>
1987 This error is given if the value of the <i>ovecsize</i> argument is negative.
1988 <pre>
1989 PCRE_ERROR_RECURSIONLIMIT (-21)
1990 </pre>
1991 The internal recursion limit, as specified by the <i>match_limit_recursion</i>
1992 field in a <b>pcre_extra</b> structure (or defaulted) was reached. See the
1993 description above.
1994 <pre>
1995 PCRE_ERROR_BADNEWLINE (-23)
1996 </pre>
1997 An invalid combination of PCRE_NEWLINE_<i>xxx</i> options was given.
1998 <pre>
1999 PCRE_ERROR_BADOFFSET (-24)
2000 </pre>
2001 The value of <i>startoffset</i> was negative or greater than the length of the
2002 subject, that is, the value in <i>length</i>.
2003 <pre>
2004 PCRE_ERROR_SHORTUTF8 (-25)
2005 </pre>
2006 This error is returned instead of PCRE_ERROR_BADUTF8 when the subject string
2007 ends with a truncated UTF-8 character and the PCRE_PARTIAL_HARD option is set.
2008 Information about the failure is returned as for PCRE_ERROR_BADUTF8. It is in
2009 fact sufficient to detect this case, but this special error code for
2010 PCRE_PARTIAL_HARD precedes the implementation of returned information; it is
2011 retained for backwards compatibility.
2012 <pre>
2013 PCRE_ERROR_RECURSELOOP (-26)
2014 </pre>
2015 This error is returned when <b>pcre_exec()</b> detects a recursion loop within
2016 the pattern. Specifically, it means that either the whole pattern or a
2017 subpattern has been called recursively for the second time at the same position
2018 in the subject string. Some simple patterns that might do this are detected and
2019 faulted at compile time, but more complicated cases, in particular mutual
2020 recursions between two different subpatterns, cannot be detected until run
2021 time.
2022 <pre>
2023 PCRE_ERROR_JIT_STACKLIMIT (-27)
2024 </pre>
2025 This error is returned when a pattern that was successfully studied using the
2026 PCRE_STUDY_JIT_COMPILE option is being matched, but the memory available for
2027 the just-in-time processing stack is not large enough. See the
2028 <a href="pcrejit.html"><b>pcrejit</b></a>
2029 documentation for more details.
2030 </P>
2031 <P>
2032 Error numbers -16 to -20 and -22 are not used by <b>pcre_exec()</b>.
2033 <a name="badutf8reasons"></a></P>
2034 <br><b>
2035 Reason codes for invalid UTF-8 strings
2036 </b><br>
2037 <P>
2038 When <b>pcre_exec()</b> returns either PCRE_ERROR_BADUTF8 or
2039 PCRE_ERROR_SHORTUTF8, and the size of the output vector (<i>ovecsize</i>) is at
2040 least 2, the offset of the start of the invalid UTF-8 character is placed in
2041 the first output vector element (<i>ovector[0]</i>) and a reason code is placed
2042 in the second element (<i>ovector[1]</i>). The reason codes are given names in
2043 the <b>pcre.h</b> header file:
2044 <pre>
2045 PCRE_UTF8_ERR1
2046 PCRE_UTF8_ERR2
2047 PCRE_UTF8_ERR3
2048 PCRE_UTF8_ERR4
2049 PCRE_UTF8_ERR5
2050 </pre>
2051 The string ends with a truncated UTF-8 character; the code specifies how many
2052 bytes are missing (1 to 5). Although RFC 3629 restricts UTF-8 characters to be
2053 no longer than 4 bytes, the encoding scheme (originally defined by RFC 2279)
2054 allows for up to 6 bytes, and this is checked first; hence the possibility of
2055 4 or 5 missing bytes.
2056 <pre>
2057 PCRE_UTF8_ERR6
2058 PCRE_UTF8_ERR7
2059 PCRE_UTF8_ERR8
2060 PCRE_UTF8_ERR9
2061 PCRE_UTF8_ERR10
2062 </pre>
2063 The two most significant bits of the 2nd, 3rd, 4th, 5th, or 6th byte of the
2064 character do not have the binary value 0b10 (that is, either the most
2065 significant bit is 0, or the next bit is 1).
2066 <pre>
2067 PCRE_UTF8_ERR11
2068 PCRE_UTF8_ERR12
2069 </pre>
2070 A character that is valid by the RFC 2279 rules is either 5 or 6 bytes long;
2071 these code points are excluded by RFC 3629.
2072 <pre>
2073 PCRE_UTF8_ERR13
2074 </pre>
2075 A 4-byte character has a value greater than 0x10fff; these code points are
2076 excluded by RFC 3629.
2077 <pre>
2078 PCRE_UTF8_ERR14
2079 </pre>
2080 A 3-byte character has a value in the range 0xd800 to 0xdfff; this range of
2081 code points are reserved by RFC 3629 for use with UTF-16, and so are excluded
2082 from UTF-8.
2083 <pre>
2084 PCRE_UTF8_ERR15
2085 PCRE_UTF8_ERR16
2086 PCRE_UTF8_ERR17
2087 PCRE_UTF8_ERR18
2088 PCRE_UTF8_ERR19
2089 </pre>
2090 A 2-, 3-, 4-, 5-, or 6-byte character is "overlong", that is, it codes for a
2091 value that can be represented by fewer bytes, which is invalid. For example,
2092 the two bytes 0xc0, 0xae give the value 0x2e, whose correct coding uses just
2093 one byte.
2094 <pre>
2095 PCRE_UTF8_ERR20
2096 </pre>
2097 The two most significant bits of the first byte of a character have the binary
2098 value 0b10 (that is, the most significant bit is 1 and the second is 0). Such a
2099 byte can only validly occur as the second or subsequent byte of a multi-byte
2100 character.
2101 <pre>
2102 PCRE_UTF8_ERR21
2103 </pre>
2104 The first byte of a character has the value 0xfe or 0xff. These values can
2105 never occur in a valid UTF-8 string.
2106 </P>
2107 <br><a name="SEC17" href="#TOC1">EXTRACTING CAPTURED SUBSTRINGS BY NUMBER</a><br>
2108 <P>
2109 <b>int pcre_copy_substring(const char *<i>subject</i>, int *<i>ovector</i>,</b>
2110 <b>int <i>stringcount</i>, int <i>stringnumber</i>, char *<i>buffer</i>,</b>
2111 <b>int <i>buffersize</i>);</b>
2112 </P>
2113 <P>
2114 <b>int pcre_get_substring(const char *<i>subject</i>, int *<i>ovector</i>,</b>
2115 <b>int <i>stringcount</i>, int <i>stringnumber</i>,</b>
2116 <b>const char **<i>stringptr</i>);</b>
2117 </P>
2118 <P>
2119 <b>int pcre_get_substring_list(const char *<i>subject</i>,</b>
2120 <b>int *<i>ovector</i>, int <i>stringcount</i>, const char ***<i>listptr</i>);</b>
2121 </P>
2122 <P>
2123 Captured substrings can be accessed directly by using the offsets returned by
2124 <b>pcre_exec()</b> in <i>ovector</i>. For convenience, the functions
2125 <b>pcre_copy_substring()</b>, <b>pcre_get_substring()</b>, and
2126 <b>pcre_get_substring_list()</b> are provided for extracting captured substrings
2127 as new, separate, zero-terminated strings. These functions identify substrings
2128 by number. The next section describes functions for extracting named
2129 substrings.
2130 </P>
2131 <P>
2132 A substring that contains a binary zero is correctly extracted and has a
2133 further zero added on the end, but the result is not, of course, a C string.
2134 However, you can process such a string by referring to the length that is
2135 returned by <b>pcre_copy_substring()</b> and <b>pcre_get_substring()</b>.
2136 Unfortunately, the interface to <b>pcre_get_substring_list()</b> is not adequate
2137 for handling strings containing binary zeros, because the end of the final
2138 string is not independently indicated.
2139 </P>
2140 <P>
2141 The first three arguments are the same for all three of these functions:
2142 <i>subject</i> is the subject string that has just been successfully matched,
2143 <i>ovector</i> is a pointer to the vector of integer offsets that was passed to
2144 <b>pcre_exec()</b>, and <i>stringcount</i> is the number of substrings that were
2145 captured by the match, including the substring that matched the entire regular
2146 expression. This is the value returned by <b>pcre_exec()</b> if it is greater
2147 than zero. If <b>pcre_exec()</b> returned zero, indicating that it ran out of
2148 space in <i>ovector</i>, the value passed as <i>stringcount</i> should be the
2149 number of elements in the vector divided by three.
2150 </P>
2151 <P>
2152 The functions <b>pcre_copy_substring()</b> and <b>pcre_get_substring()</b>
2153 extract a single substring, whose number is given as <i>stringnumber</i>. A
2154 value of zero extracts the substring that matched the entire pattern, whereas
2155 higher values extract the captured substrings. For <b>pcre_copy_substring()</b>,
2156 the string is placed in <i>buffer</i>, whose length is given by
2157 <i>buffersize</i>, while for <b>pcre_get_substring()</b> a new block of memory is
2158 obtained via <b>pcre_malloc</b>, and its address is returned via
2159 <i>stringptr</i>. The yield of the function is the length of the string, not
2160 including the terminating zero, or one of these error codes:
2161 <pre>
2162 PCRE_ERROR_NOMEMORY (-6)
2163 </pre>
2164 The buffer was too small for <b>pcre_copy_substring()</b>, or the attempt to get
2165 memory failed for <b>pcre_get_substring()</b>.
2166 <pre>
2167 PCRE_ERROR_NOSUBSTRING (-7)
2168 </pre>
2169 There is no substring whose number is <i>stringnumber</i>.
2170 </P>
2171 <P>
2172 The <b>pcre_get_substring_list()</b> function extracts all available substrings
2173 and builds a list of pointers to them. All this is done in a single block of
2174 memory that is obtained via <b>pcre_malloc</b>. The address of the memory block
2175 is returned via <i>listptr</i>, which is also the start of the list of string
2176 pointers. The end of the list is marked by a NULL pointer. The yield of the
2177 function is zero if all went well, or the error code
2178 <pre>
2179 PCRE_ERROR_NOMEMORY (-6)
2180 </pre>
2181 if the attempt to get the memory block failed.
2182 </P>
2183 <P>
2184 When any of these functions encounter a substring that is unset, which can
2185 happen when capturing subpattern number <i>n+1</i> matches some part of the
2186 subject, but subpattern <i>n</i> has not been used at all, they return an empty
2187 string. This can be distinguished from a genuine zero-length substring by
2188 inspecting the appropriate offset in <i>ovector</i>, which is negative for unset
2189 substrings.
2190 </P>
2191 <P>
2192 The two convenience functions <b>pcre_free_substring()</b> and
2193 <b>pcre_free_substring_list()</b> can be used to free the memory returned by
2194 a previous call of <b>pcre_get_substring()</b> or
2195 <b>pcre_get_substring_list()</b>, respectively. They do nothing more than call
2196 the function pointed to by <b>pcre_free</b>, which of course could be called
2197 directly from a C program. However, PCRE is used in some situations where it is
2198 linked via a special interface to another programming language that cannot use
2199 <b>pcre_free</b> directly; it is for these cases that the functions are
2200 provided.
2201 </P>
2202 <br><a name="SEC18" href="#TOC1">EXTRACTING CAPTURED SUBSTRINGS BY NAME</a><br>
2203 <P>
2204 <b>int pcre_get_stringnumber(const pcre *<i>code</i>,</b>
2205 <b>const char *<i>name</i>);</b>
2206 </P>
2207 <P>
2208 <b>int pcre_copy_named_substring(const pcre *<i>code</i>,</b>
2209 <b>const char *<i>subject</i>, int *<i>ovector</i>,</b>
2210 <b>int <i>stringcount</i>, const char *<i>stringname</i>,</b>
2211 <b>char *<i>buffer</i>, int <i>buffersize</i>);</b>
2212 </P>
2213 <P>
2214 <b>int pcre_get_named_substring(const pcre *<i>code</i>,</b>
2215 <b>const char *<i>subject</i>, int *<i>ovector</i>,</b>
2216 <b>int <i>stringcount</i>, const char *<i>stringname</i>,</b>
2217 <b>const char **<i>stringptr</i>);</b>
2218 </P>
2219 <P>
2220 To extract a substring by name, you first have to find associated number.
2221 For example, for this pattern
2222 <pre>
2223 (a+)b(?&#60;xxx&#62;\d+)...
2224 </pre>
2225 the number of the subpattern called "xxx" is 2. If the name is known to be
2226 unique (PCRE_DUPNAMES was not set), you can find the number from the name by
2227 calling <b>pcre_get_stringnumber()</b>. The first argument is the compiled
2228 pattern, and the second is the name. The yield of the function is the
2229 subpattern number, or PCRE_ERROR_NOSUBSTRING (-7) if there is no subpattern of
2230 that name.
2231 </P>
2232 <P>
2233 Given the number, you can extract the substring directly, or use one of the
2234 functions described in the previous section. For convenience, there are also
2235 two functions that do the whole job.
2236 </P>
2237 <P>
2238 Most of the arguments of <b>pcre_copy_named_substring()</b> and
2239 <b>pcre_get_named_substring()</b> are the same as those for the similarly named
2240 functions that extract by number. As these are described in the previous
2241 section, they are not re-described here. There are just two differences:
2242 </P>
2243 <P>
2244 First, instead of a substring number, a substring name is given. Second, there
2245 is an extra argument, given at the start, which is a pointer to the compiled
2246 pattern. This is needed in order to gain access to the name-to-number
2247 translation table.
2248 </P>
2249 <P>
2250 These functions call <b>pcre_get_stringnumber()</b>, and if it succeeds, they
2251 then call <b>pcre_copy_substring()</b> or <b>pcre_get_substring()</b>, as
2252 appropriate. <b>NOTE:</b> If PCRE_DUPNAMES is set and there are duplicate names,
2253 the behaviour may not be what you want (see the next section).
2254 </P>
2255 <P>
2256 <b>Warning:</b> If the pattern uses the (?| feature to set up multiple
2257 subpatterns with the same number, as described in the
2258 <a href="pcrepattern.html#dupsubpatternnumber">section on duplicate subpattern numbers</a>
2259 in the
2260 <a href="pcrepattern.html"><b>pcrepattern</b></a>
2261 page, you cannot use names to distinguish the different subpatterns, because
2262 names are not included in the compiled code. The matching process uses only
2263 numbers. For this reason, the use of different names for subpatterns of the
2264 same number causes an error at compile time.
2265 </P>
2266 <br><a name="SEC19" href="#TOC1">DUPLICATE SUBPATTERN NAMES</a><br>
2267 <P>
2268 <b>int pcre_get_stringtable_entries(const pcre *<i>code</i>,</b>
2269 <b>const char *<i>name</i>, char **<i>first</i>, char **<i>last</i>);</b>
2270 </P>
2271 <P>
2272 When a pattern is compiled with the PCRE_DUPNAMES option, names for subpatterns
2273 are not required to be unique. (Duplicate names are always allowed for
2274 subpatterns with the same number, created by using the (?| feature. Indeed, if
2275 such subpatterns are named, they are required to use the same names.)
2276 </P>
2277 <P>
2278 Normally, patterns with duplicate names are such that in any one match, only
2279 one of the named subpatterns participates. An example is shown in the
2280 <a href="pcrepattern.html"><b>pcrepattern</b></a>
2281 documentation.
2282 </P>
2283 <P>
2284 When duplicates are present, <b>pcre_copy_named_substring()</b> and
2285 <b>pcre_get_named_substring()</b> return the first substring corresponding to
2286 the given name that is set. If none are set, PCRE_ERROR_NOSUBSTRING (-7) is
2287 returned; no data is returned. The <b>pcre_get_stringnumber()</b> function
2288 returns one of the numbers that are associated with the name, but it is not
2289 defined which it is.
2290 </P>
2291 <P>
2292 If you want to get full details of all captured substrings for a given name,
2293 you must use the <b>pcre_get_stringtable_entries()</b> function. The first
2294 argument is the compiled pattern, and the second is the name. The third and
2295 fourth are pointers to variables which are updated by the function. After it
2296 has run, they point to the first and last entries in the name-to-number table
2297 for the given name. The function itself returns the length of each entry, or
2298 PCRE_ERROR_NOSUBSTRING (-7) if there are none. The format of the table is
2299 described above in the section entitled <i>Information about a pattern</i>
2300 <a href="#infoaboutpattern">above.</a>
2301 Given all the relevant entries for the name, you can extract each of their
2302 numbers, and hence the captured data, if any.
2303 </P>
2304 <br><a name="SEC20" href="#TOC1">FINDING ALL POSSIBLE MATCHES</a><br>
2305 <P>
2306 The traditional matching function uses a similar algorithm to Perl, which stops
2307 when it finds the first match, starting at a given point in the subject. If you
2308 want to find all possible matches, or the longest possible match, consider
2309 using the alternative matching function (see below) instead. If you cannot use
2310 the alternative function, but still need to find all possible matches, you
2311 can kludge it up by making use of the callout facility, which is described in
2312 the
2313 <a href="pcrecallout.html"><b>pcrecallout</b></a>
2314 documentation.
2315 </P>
2316 <P>
2317 What you have to do is to insert a callout right at the end of the pattern.
2318 When your callout function is called, extract and save the current matched
2319 substring. Then return 1, which forces <b>pcre_exec()</b> to backtrack and try
2320 other alternatives. Ultimately, when it runs out of matches, <b>pcre_exec()</b>
2321 will yield PCRE_ERROR_NOMATCH.
2322 <a name="dfamatch"></a></P>
2323 <br><a name="SEC21" href="#TOC1">MATCHING A PATTERN: THE ALTERNATIVE FUNCTION</a><br>
2324 <P>
2325 <b>int pcre_dfa_exec(const pcre *<i>code</i>, const pcre_extra *<i>extra</i>,</b>
2326 <b>const char *<i>subject</i>, int <i>length</i>, int <i>startoffset</i>,</b>
2327 <b>int <i>options</i>, int *<i>ovector</i>, int <i>ovecsize</i>,</b>
2328 <b>int *<i>workspace</i>, int <i>wscount</i>);</b>
2329 </P>
2330 <P>
2331 The function <b>pcre_dfa_exec()</b> is called to match a subject string against
2332 a compiled pattern, using a matching algorithm that scans the subject string
2333 just once, and does not backtrack. This has different characteristics to the
2334 normal algorithm, and is not compatible with Perl. Some of the features of PCRE
2335 patterns are not supported. Nevertheless, there are times when this kind of
2336 matching can be useful. For a discussion of the two matching algorithms, and a
2337 list of features that <b>pcre_dfa_exec()</b> does not support, see the
2338 <a href="pcrematching.html"><b>pcrematching</b></a>
2339 documentation.
2340 </P>
2341 <P>
2342 The arguments for the <b>pcre_dfa_exec()</b> function are the same as for
2343 <b>pcre_exec()</b>, plus two extras. The <i>ovector</i> argument is used in a
2344 different way, and this is described below. The other common arguments are used
2345 in the same way as for <b>pcre_exec()</b>, so their description is not repeated
2346 here.
2347 </P>
2348 <P>
2349 The two additional arguments provide workspace for the function. The workspace
2350 vector should contain at least 20 elements. It is used for keeping track of
2351 multiple paths through the pattern tree. More workspace will be needed for
2352 patterns and subjects where there are a lot of potential matches.
2353 </P>
2354 <P>
2355 Here is an example of a simple call to <b>pcre_dfa_exec()</b>:
2356 <pre>
2357 int rc;
2358 int ovector[10];
2359 int wspace[20];
2360 rc = pcre_dfa_exec(
2361 re, /* result of pcre_compile() */
2362 NULL, /* we didn't study the pattern */
2363 "some string", /* the subject string */
2364 11, /* the length of the subject string */
2365 0, /* start at offset 0 in the subject */
2366 0, /* default options */
2367 ovector, /* vector of integers for substring information */
2368 10, /* number of elements (NOT size in bytes) */
2369 wspace, /* working space vector */
2370 20); /* number of elements (NOT size in bytes) */
2371 </PRE>
2372 </P>
2373 <br><b>
2374 Option bits for <b>pcre_dfa_exec()</b>
2375 </b><br>
2376 <P>
2377 The unused bits of the <i>options</i> argument for <b>pcre_dfa_exec()</b> must be
2378 zero. The only bits that may be set are PCRE_ANCHORED, PCRE_NEWLINE_<i>xxx</i>,
2379 PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY, PCRE_NOTEMPTY_ATSTART,
2380 PCRE_NO_UTF8_CHECK, PCRE_BSR_ANYCRLF, PCRE_BSR_UNICODE, PCRE_NO_START_OPTIMIZE,
2381 PCRE_PARTIAL_HARD, PCRE_PARTIAL_SOFT, PCRE_DFA_SHORTEST, and PCRE_DFA_RESTART.
2382 All but the last four of these are exactly the same as for <b>pcre_exec()</b>,
2383 so their description is not repeated here.
2384 <pre>
2385 PCRE_PARTIAL_HARD
2386 PCRE_PARTIAL_SOFT
2387 </pre>
2388 These have the same general effect as they do for <b>pcre_exec()</b>, but the
2389 details are slightly different. When PCRE_PARTIAL_HARD is set for
2390 <b>pcre_dfa_exec()</b>, it returns PCRE_ERROR_PARTIAL if the end of the subject
2391 is reached and there is still at least one matching possibility that requires
2392 additional characters. This happens even if some complete matches have also
2393 been found. When PCRE_PARTIAL_SOFT is set, the return code PCRE_ERROR_NOMATCH
2394 is converted into PCRE_ERROR_PARTIAL if the end of the subject is reached,
2395 there have been no complete matches, but there is still at least one matching
2396 possibility. The portion of the string that was inspected when the longest
2397 partial match was found is set as the first matching string in both cases.
2398 There is a more detailed discussion of partial and multi-segment matching, with
2399 examples, in the
2400 <a href="pcrepartial.html"><b>pcrepartial</b></a>
2401 documentation.
2402 <pre>
2403 PCRE_DFA_SHORTEST
2404 </pre>
2405 Setting the PCRE_DFA_SHORTEST option causes the matching algorithm to stop as
2406 soon as it has found one match. Because of the way the alternative algorithm
2407 works, this is necessarily the shortest possible match at the first possible
2408 matching point in the subject string.
2409 <pre>
2410 PCRE_DFA_RESTART
2411 </pre>
2412 When <b>pcre_dfa_exec()</b> returns a partial match, it is possible to call it
2413 again, with additional subject characters, and have it continue with the same
2414 match. The PCRE_DFA_RESTART option requests this action; when it is set, the
2415 <i>workspace</i> and <i>wscount</i> options must reference the same vector as
2416 before because data about the match so far is left in them after a partial
2417 match. There is more discussion of this facility in the
2418 <a href="pcrepartial.html"><b>pcrepartial</b></a>
2419 documentation.
2420 </P>
2421 <br><b>
2422 Successful returns from <b>pcre_dfa_exec()</b>
2423 </b><br>
2424 <P>
2425 When <b>pcre_dfa_exec()</b> succeeds, it may have matched more than one
2426 substring in the subject. Note, however, that all the matches from one run of
2427 the function start at the same point in the subject. The shorter matches are
2428 all initial substrings of the longer matches. For example, if the pattern
2429 <pre>
2430 &#60;.*&#62;
2431 </pre>
2432 is matched against the string
2433 <pre>
2434 This is &#60;something&#62; &#60;something else&#62; &#60;something further&#62; no more
2435 </pre>
2436 the three matched strings are
2437 <pre>
2438 &#60;something&#62;
2439 &#60;something&#62; &#60;something else&#62;
2440 &#60;something&#62; &#60;something else&#62; &#60;something further&#62;
2441 </pre>
2442 On success, the yield of the function is a number greater than zero, which is
2443 the number of matched substrings. The substrings themselves are returned in
2444 <i>ovector</i>. Each string uses two elements; the first is the offset to the
2445 start, and the second is the offset to the end. In fact, all the strings have
2446 the same start offset. (Space could have been saved by giving this only once,
2447 but it was decided to retain some compatibility with the way <b>pcre_exec()</b>
2448 returns data, even though the meaning of the strings is different.)
2449 </P>
2450 <P>
2451 The strings are returned in reverse order of length; that is, the longest
2452 matching string is given first. If there were too many matches to fit into
2453 <i>ovector</i>, the yield of the function is zero, and the vector is filled with
2454 the longest matches. Unlike <b>pcre_exec()</b>, <b>pcre_dfa_exec()</b> can use
2455 the entire <i>ovector</i> for returning matched strings.
2456 </P>
2457 <br><b>
2458 Error returns from <b>pcre_dfa_exec()</b>
2459 </b><br>
2460 <P>
2461 The <b>pcre_dfa_exec()</b> function returns a negative number when it fails.
2462 Many of the errors are the same as for <b>pcre_exec()</b>, and these are
2463 described
2464 <a href="#errorlist">above.</a>
2465 There are in addition the following errors that are specific to
2466 <b>pcre_dfa_exec()</b>:
2467 <pre>
2468 PCRE_ERROR_DFA_UITEM (-16)
2469 </pre>
2470 This return is given if <b>pcre_dfa_exec()</b> encounters an item in the pattern
2471 that it does not support, for instance, the use of \C or a back reference.
2472 <pre>
2473 PCRE_ERROR_DFA_UCOND (-17)
2474 </pre>
2475 This return is given if <b>pcre_dfa_exec()</b> encounters a condition item that
2476 uses a back reference for the condition, or a test for recursion in a specific
2477 group. These are not supported.
2478 <pre>
2479 PCRE_ERROR_DFA_UMLIMIT (-18)
2480 </pre>
2481 This return is given if <b>pcre_dfa_exec()</b> is called with an <i>extra</i>
2482 block that contains a setting of the <i>match_limit</i> or
2483 <i>match_limit_recursion</i> fields. This is not supported (these fields are
2484 meaningless for DFA matching).
2485 <pre>
2486 PCRE_ERROR_DFA_WSSIZE (-19)
2487 </pre>
2488 This return is given if <b>pcre_dfa_exec()</b> runs out of space in the
2489 <i>workspace</i> vector.
2490 <pre>
2491 PCRE_ERROR_DFA_RECURSE (-20)
2492 </pre>
2493 When a recursive subpattern is processed, the matching function calls itself
2494 recursively, using private vectors for <i>ovector</i> and <i>workspace</i>. This
2495 error is given if the output vector is not large enough. This should be
2496 extremely rare, as a vector of size 1000 is used.
2497 </P>
2498 <br><a name="SEC22" href="#TOC1">SEE ALSO</a><br>
2499 <P>
2500 <b>pcrebuild</b>(3), <b>pcrecallout</b>(3), <b>pcrecpp(3)</b>(3),
2501 <b>pcrematching</b>(3), <b>pcrepartial</b>(3), <b>pcreposix</b>(3),
2502 <b>pcreprecompile</b>(3), <b>pcresample</b>(3), <b>pcrestack</b>(3).
2503 </P>
2504 <br><a name="SEC23" href="#TOC1">AUTHOR</a><br>
2505 <P>
2506 Philip Hazel
2507 <br>
2508 University Computing Service
2509 <br>
2510 Cambridge CB2 3QH, England.
2511 <br>
2512 </P>
2513 <br><a name="SEC24" href="#TOC1">REVISION</a><br>
2514 <P>
2515 Last updated: 02 December 2011
2516 <br>
2517 Copyright &copy; 1997-2011 University of Cambridge.
2518 <br>
2519 <p>
2520 Return to the <a href="index.html">PCRE index page</a>.
2521 </p>

Properties

Name Value
svn:eol-style native
svn:keywords "Author Date Id Revision Url"

webmaster@exim.org
ViewVC Help
Powered by ViewVC 1.1.12