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Sun Nov 11 20:27:03 2012 UTC (8 years, 2 months ago) by ph10
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File tidies, preparing for 8.32-RC1.
1 .TH PCREAPI 3 "08 November 2012" "PCRE 8.32"
3 PCRE - Perl-compatible regular expressions
4 .sp
5 .B #include <pcre.h>
6 .
7 .
9 .rs
10 .sp
11 .SM
12 .B pcre *pcre_compile(const char *\fIpattern\fP, int \fIoptions\fP,
13 .ti +5n
14 .B const char **\fIerrptr\fP, int *\fIerroffset\fP,
15 .ti +5n
16 .B const unsigned char *\fItableptr\fP);
17 .PP
18 .B pcre *pcre_compile2(const char *\fIpattern\fP, int \fIoptions\fP,
19 .ti +5n
20 .B int *\fIerrorcodeptr\fP,
21 .ti +5n
22 .B const char **\fIerrptr\fP, int *\fIerroffset\fP,
23 .ti +5n
24 .B const unsigned char *\fItableptr\fP);
25 .PP
26 .B pcre_extra *pcre_study(const pcre *\fIcode\fP, int \fIoptions\fP,
27 .ti +5n
28 .B const char **\fIerrptr\fP);
29 .PP
30 .B void pcre_free_study(pcre_extra *\fIextra\fP);
31 .PP
32 .B int pcre_exec(const pcre *\fIcode\fP, "const pcre_extra *\fIextra\fP,"
33 .ti +5n
34 .B "const char *\fIsubject\fP," int \fIlength\fP, int \fIstartoffset\fP,
35 .ti +5n
36 .B int \fIoptions\fP, int *\fIovector\fP, int \fIovecsize\fP);
37 .PP
38 .B int pcre_dfa_exec(const pcre *\fIcode\fP, "const pcre_extra *\fIextra\fP,"
39 .ti +5n
40 .B "const char *\fIsubject\fP," int \fIlength\fP, int \fIstartoffset\fP,
41 .ti +5n
42 .B int \fIoptions\fP, int *\fIovector\fP, int \fIovecsize\fP,
43 .ti +5n
44 .B int *\fIworkspace\fP, int \fIwscount\fP);
45 .
46 .
48 .rs
49 .sp
50 .B int pcre_copy_named_substring(const pcre *\fIcode\fP,
51 .ti +5n
52 .B const char *\fIsubject\fP, int *\fIovector\fP,
53 .ti +5n
54 .B int \fIstringcount\fP, const char *\fIstringname\fP,
55 .ti +5n
56 .B char *\fIbuffer\fP, int \fIbuffersize\fP);
57 .PP
58 .B int pcre_copy_substring(const char *\fIsubject\fP, int *\fIovector\fP,
59 .ti +5n
60 .B int \fIstringcount\fP, int \fIstringnumber\fP, char *\fIbuffer\fP,
61 .ti +5n
62 .B int \fIbuffersize\fP);
63 .PP
64 .B int pcre_get_named_substring(const pcre *\fIcode\fP,
65 .ti +5n
66 .B const char *\fIsubject\fP, int *\fIovector\fP,
67 .ti +5n
68 .B int \fIstringcount\fP, const char *\fIstringname\fP,
69 .ti +5n
70 .B const char **\fIstringptr\fP);
71 .PP
72 .B int pcre_get_stringnumber(const pcre *\fIcode\fP,
73 .ti +5n
74 .B const char *\fIname\fP);
75 .PP
76 .B int pcre_get_stringtable_entries(const pcre *\fIcode\fP,
77 .ti +5n
78 .B const char *\fIname\fP, char **\fIfirst\fP, char **\fIlast\fP);
79 .PP
80 .B int pcre_get_substring(const char *\fIsubject\fP, int *\fIovector\fP,
81 .ti +5n
82 .B int \fIstringcount\fP, int \fIstringnumber\fP,
83 .ti +5n
84 .B const char **\fIstringptr\fP);
85 .PP
86 .B int pcre_get_substring_list(const char *\fIsubject\fP,
87 .ti +5n
88 .B int *\fIovector\fP, int \fIstringcount\fP, "const char ***\fIlistptr\fP);"
89 .PP
90 .B void pcre_free_substring(const char *\fIstringptr\fP);
91 .PP
92 .B void pcre_free_substring_list(const char **\fIstringptr\fP);
93 .
94 .
96 .rs
97 .sp
98 .B int pcre_jit_exec(const pcre *\fIcode\fP, "const pcre_extra *\fIextra\fP,"
99 .ti +5n
100 .B "const char *\fIsubject\fP," int \fIlength\fP, int \fIstartoffset\fP,
101 .ti +5n
102 .B int \fIoptions\fP, int *\fIovector\fP, int \fIovecsize\fP,
103 .ti +5n
104 .B pcre_jit_stack *\fIjstack\fP);
105 .PP
106 .B pcre_jit_stack *pcre_jit_stack_alloc(int \fIstartsize\fP, int \fImaxsize\fP);
107 .PP
108 .B void pcre_jit_stack_free(pcre_jit_stack *\fIstack\fP);
109 .PP
110 .B void pcre_assign_jit_stack(pcre_extra *\fIextra\fP,
111 .ti +5n
112 .B pcre_jit_callback \fIcallback\fP, void *\fIdata\fP);
113 .PP
114 .B const unsigned char *pcre_maketables(void);
115 .PP
116 .B int pcre_fullinfo(const pcre *\fIcode\fP, "const pcre_extra *\fIextra\fP,"
117 .ti +5n
118 .B int \fIwhat\fP, void *\fIwhere\fP);
119 .PP
120 .B int pcre_refcount(pcre *\fIcode\fP, int \fIadjust\fP);
121 .PP
122 .B int pcre_config(int \fIwhat\fP, void *\fIwhere\fP);
123 .PP
124 .B const char *pcre_version(void);
125 .PP
126 .B int pcre_pattern_to_host_byte_order(pcre *\fIcode\fP,
127 .ti +5n
128 .B pcre_extra *\fIextra\fP, const unsigned char *\fItables\fP);
129 .
130 .
132 .rs
133 .sp
134 .B void *(*pcre_malloc)(size_t);
135 .PP
136 .B void (*pcre_free)(void *);
137 .PP
138 .B void *(*pcre_stack_malloc)(size_t);
139 .PP
140 .B void (*pcre_stack_free)(void *);
141 .PP
142 .B int (*pcre_callout)(pcre_callout_block *);
143 .
144 .
146 .rs
147 .sp
148 As well as support for 8-bit character strings, PCRE also supports 16-bit
149 strings (from release 8.30) and 32-bit strings (from release 8.32), by means of
150 two additional libraries. They can be built as well as, or instead of, the
151 8-bit library. To avoid too much complication, this document describes the
152 8-bit versions of the functions, with only occasional references to the 16-bit
153 and 32-bit libraries.
154 .P
155 The 16-bit and 32-bit functions operate in the same way as their 8-bit
156 counterparts; they just use different data types for their arguments and
157 results, and their names start with \fBpcre16_\fP or \fBpcre32_\fP instead of
158 \fBpcre_\fP. For every option that has UTF8 in its name (for example,
159 PCRE_UTF8), there are corresponding 16-bit and 32-bit names with UTF8 replaced
160 by UTF16 or UTF32, respectively. This facility is in fact just cosmetic; the
161 16-bit and 32-bit option names define the same bit values.
162 .P
163 References to bytes and UTF-8 in this document should be read as references to
164 16-bit data quantities and UTF-16 when using the 16-bit library, or 32-bit data
165 quantities and UTF-32 when using the 32-bit library, unless specified
166 otherwise. More details of the specific differences for the 16-bit and 32-bit
167 libraries are given in the
168 .\" HREF
169 \fBpcre16\fP
170 .\"
171 and
172 .\" HREF
173 \fBpcre32\fP
174 .\"
175 pages.
176 .
177 .
179 .rs
180 .sp
181 PCRE has its own native API, which is described in this document. There are
182 also some wrapper functions (for the 8-bit library only) that correspond to the
183 POSIX regular expression API, but they do not give access to all the
184 functionality. They are described in the
185 .\" HREF
186 \fBpcreposix\fP
187 .\"
188 documentation. Both of these APIs define a set of C function calls. A C++
189 wrapper (again for the 8-bit library only) is also distributed with PCRE. It is
190 documented in the
191 .\" HREF
192 \fBpcrecpp\fP
193 .\"
194 page.
195 .P
196 The native API C function prototypes are defined in the header file
197 \fBpcre.h\fP, and on Unix-like systems the (8-bit) library itself is called
198 \fBlibpcre\fP. It can normally be accessed by adding \fB-lpcre\fP to the
199 command for linking an application that uses PCRE. The header file defines the
200 macros PCRE_MAJOR and PCRE_MINOR to contain the major and minor release numbers
201 for the library. Applications can use these to include support for different
202 releases of PCRE.
203 .P
204 In a Windows environment, if you want to statically link an application program
205 against a non-dll \fBpcre.a\fP file, you must define PCRE_STATIC before
206 including \fBpcre.h\fP or \fBpcrecpp.h\fP, because otherwise the
207 \fBpcre_malloc()\fP and \fBpcre_free()\fP exported functions will be declared
208 \fB__declspec(dllimport)\fP, with unwanted results.
209 .P
210 The functions \fBpcre_compile()\fP, \fBpcre_compile2()\fP, \fBpcre_study()\fP,
211 and \fBpcre_exec()\fP are used for compiling and matching regular expressions
212 in a Perl-compatible manner. A sample program that demonstrates the simplest
213 way of using them is provided in the file called \fIpcredemo.c\fP in the PCRE
214 source distribution. A listing of this program is given in the
215 .\" HREF
216 \fBpcredemo\fP
217 .\"
218 documentation, and the
219 .\" HREF
220 \fBpcresample\fP
221 .\"
222 documentation describes how to compile and run it.
223 .P
224 Just-in-time compiler support is an optional feature of PCRE that can be built
225 in appropriate hardware environments. It greatly speeds up the matching
226 performance of many patterns. Simple programs can easily request that it be
227 used if available, by setting an option that is ignored when it is not
228 relevant. More complicated programs might need to make use of the functions
229 \fBpcre_jit_stack_alloc()\fP, \fBpcre_jit_stack_free()\fP, and
230 \fBpcre_assign_jit_stack()\fP in order to control the JIT code's memory usage.
231 .P
232 From release 8.32 there is also a direct interface for JIT execution, which
233 gives improved performance. The JIT-specific functions are discussed in the
234 .\" HREF
235 \fBpcrejit\fP
236 .\"
237 documentation.
238 .P
239 A second matching function, \fBpcre_dfa_exec()\fP, which is not
240 Perl-compatible, is also provided. This uses a different algorithm for the
241 matching. The alternative algorithm finds all possible matches (at a given
242 point in the subject), and scans the subject just once (unless there are
243 lookbehind assertions). However, this algorithm does not return captured
244 substrings. A description of the two matching algorithms and their advantages
245 and disadvantages is given in the
246 .\" HREF
247 \fBpcrematching\fP
248 .\"
249 documentation.
250 .P
251 In addition to the main compiling and matching functions, there are convenience
252 functions for extracting captured substrings from a subject string that is
253 matched by \fBpcre_exec()\fP. They are:
254 .sp
255 \fBpcre_copy_substring()\fP
256 \fBpcre_copy_named_substring()\fP
257 \fBpcre_get_substring()\fP
258 \fBpcre_get_named_substring()\fP
259 \fBpcre_get_substring_list()\fP
260 \fBpcre_get_stringnumber()\fP
261 \fBpcre_get_stringtable_entries()\fP
262 .sp
263 \fBpcre_free_substring()\fP and \fBpcre_free_substring_list()\fP are also
264 provided, to free the memory used for extracted strings.
265 .P
266 The function \fBpcre_maketables()\fP is used to build a set of character tables
267 in the current locale for passing to \fBpcre_compile()\fP, \fBpcre_exec()\fP,
268 or \fBpcre_dfa_exec()\fP. This is an optional facility that is provided for
269 specialist use. Most commonly, no special tables are passed, in which case
270 internal tables that are generated when PCRE is built are used.
271 .P
272 The function \fBpcre_fullinfo()\fP is used to find out information about a
273 compiled pattern. The function \fBpcre_version()\fP returns a pointer to a
274 string containing the version of PCRE and its date of release.
275 .P
276 The function \fBpcre_refcount()\fP maintains a reference count in a data block
277 containing a compiled pattern. This is provided for the benefit of
278 object-oriented applications.
279 .P
280 The global variables \fBpcre_malloc\fP and \fBpcre_free\fP initially contain
281 the entry points of the standard \fBmalloc()\fP and \fBfree()\fP functions,
282 respectively. PCRE calls the memory management functions via these variables,
283 so a calling program can replace them if it wishes to intercept the calls. This
284 should be done before calling any PCRE functions.
285 .P
286 The global variables \fBpcre_stack_malloc\fP and \fBpcre_stack_free\fP are also
287 indirections to memory management functions. These special functions are used
288 only when PCRE is compiled to use the heap for remembering data, instead of
289 recursive function calls, when running the \fBpcre_exec()\fP function. See the
290 .\" HREF
291 \fBpcrebuild\fP
292 .\"
293 documentation for details of how to do this. It is a non-standard way of
294 building PCRE, for use in environments that have limited stacks. Because of the
295 greater use of memory management, it runs more slowly. Separate functions are
296 provided so that special-purpose external code can be used for this case. When
297 used, these functions are always called in a stack-like manner (last obtained,
298 first freed), and always for memory blocks of the same size. There is a
299 discussion about PCRE's stack usage in the
300 .\" HREF
301 \fBpcrestack\fP
302 .\"
303 documentation.
304 .P
305 The global variable \fBpcre_callout\fP initially contains NULL. It can be set
306 by the caller to a "callout" function, which PCRE will then call at specified
307 points during a matching operation. Details are given in the
308 .\" HREF
309 \fBpcrecallout\fP
310 .\"
311 documentation.
312 .
313 .
314 .\" HTML <a name="newlines"></a>
316 .rs
317 .sp
318 PCRE supports five different conventions for indicating line breaks in
319 strings: a single CR (carriage return) character, a single LF (linefeed)
320 character, the two-character sequence CRLF, any of the three preceding, or any
321 Unicode newline sequence. The Unicode newline sequences are the three just
322 mentioned, plus the single characters VT (vertical tab, U+000B), FF (form feed,
323 U+000C), NEL (next line, U+0085), LS (line separator, U+2028), and PS
324 (paragraph separator, U+2029).
325 .P
326 Each of the first three conventions is used by at least one operating system as
327 its standard newline sequence. When PCRE is built, a default can be specified.
328 The default default is LF, which is the Unix standard. When PCRE is run, the
329 default can be overridden, either when a pattern is compiled, or when it is
330 matched.
331 .P
332 At compile time, the newline convention can be specified by the \fIoptions\fP
333 argument of \fBpcre_compile()\fP, or it can be specified by special text at the
334 start of the pattern itself; this overrides any other settings. See the
335 .\" HREF
336 \fBpcrepattern\fP
337 .\"
338 page for details of the special character sequences.
339 .P
340 In the PCRE documentation the word "newline" is used to mean "the character or
341 pair of characters that indicate a line break". The choice of newline
342 convention affects the handling of the dot, circumflex, and dollar
343 metacharacters, the handling of #-comments in /x mode, and, when CRLF is a
344 recognized line ending sequence, the match position advancement for a
345 non-anchored pattern. There is more detail about this in the
346 .\" HTML <a href="#execoptions">
347 .\" </a>
348 section on \fBpcre_exec()\fP options
349 .\"
350 below.
351 .P
352 The choice of newline convention does not affect the interpretation of
353 the \en or \er escape sequences, nor does it affect what \eR matches, which is
354 controlled in a similar way, but by separate options.
355 .
356 .
358 .rs
359 .sp
360 The PCRE functions can be used in multi-threading applications, with the
361 proviso that the memory management functions pointed to by \fBpcre_malloc\fP,
362 \fBpcre_free\fP, \fBpcre_stack_malloc\fP, and \fBpcre_stack_free\fP, and the
363 callout function pointed to by \fBpcre_callout\fP, are shared by all threads.
364 .P
365 The compiled form of a regular expression is not altered during matching, so
366 the same compiled pattern can safely be used by several threads at once.
367 .P
368 If the just-in-time optimization feature is being used, it needs separate
369 memory stack areas for each thread. See the
370 .\" HREF
371 \fBpcrejit\fP
372 .\"
373 documentation for more details.
374 .
375 .
377 .rs
378 .sp
379 The compiled form of a regular expression can be saved and re-used at a later
380 time, possibly by a different program, and even on a host other than the one on
381 which it was compiled. Details are given in the
382 .\" HREF
383 \fBpcreprecompile\fP
384 .\"
385 documentation, which includes a description of the
386 \fBpcre_pattern_to_host_byte_order()\fP function. However, compiling a regular
387 expression with one version of PCRE for use with a different version is not
388 guaranteed to work and may cause crashes.
389 .
390 .
392 .rs
393 .sp
394 .B int pcre_config(int \fIwhat\fP, void *\fIwhere\fP);
395 .PP
396 The function \fBpcre_config()\fP makes it possible for a PCRE client to
397 discover which optional features have been compiled into the PCRE library. The
398 .\" HREF
399 \fBpcrebuild\fP
400 .\"
401 documentation has more details about these optional features.
402 .P
403 The first argument for \fBpcre_config()\fP is an integer, specifying which
404 information is required; the second argument is a pointer to a variable into
405 which the information is placed. The returned value is zero on success, or the
406 negative error code PCRE_ERROR_BADOPTION if the value in the first argument is
407 not recognized. The following information is available:
408 .sp
410 .sp
411 The output is an integer that is set to one if UTF-8 support is available;
412 otherwise it is set to zero. This value should normally be given to the 8-bit
413 version of this function, \fBpcre_config()\fP. If it is given to the 16-bit
414 or 32-bit version of this function, the result is PCRE_ERROR_BADOPTION.
415 .sp
417 .sp
418 The output is an integer that is set to one if UTF-16 support is available;
419 otherwise it is set to zero. This value should normally be given to the 16-bit
420 version of this function, \fBpcre16_config()\fP. If it is given to the 8-bit
421 or 32-bit version of this function, the result is PCRE_ERROR_BADOPTION.
422 .sp
424 .sp
425 The output is an integer that is set to one if UTF-32 support is available;
426 otherwise it is set to zero. This value should normally be given to the 32-bit
427 version of this function, \fBpcre32_config()\fP. If it is given to the 8-bit
428 or 16-bit version of this function, the result is PCRE_ERROR_BADOPTION.
429 .sp
431 .sp
432 The output is an integer that is set to one if support for Unicode character
433 properties is available; otherwise it is set to zero.
434 .sp
436 .sp
437 The output is an integer that is set to one if support for just-in-time
438 compiling is available; otherwise it is set to zero.
439 .sp
441 .sp
442 The output is a pointer to a zero-terminated "const char *" string. If JIT
443 support is available, the string contains the name of the architecture for
444 which the JIT compiler is configured, for example "x86 32bit (little endian +
445 unaligned)". If JIT support is not available, the result is NULL.
446 .sp
448 .sp
449 The output is an integer whose value specifies the default character sequence
450 that is recognized as meaning "newline". The values that are supported in
451 ASCII/Unicode environments are: 10 for LF, 13 for CR, 3338 for CRLF, -2 for
452 ANYCRLF, and -1 for ANY. In EBCDIC environments, CR, ANYCRLF, and ANY yield the
453 same values. However, the value for LF is normally 21, though some EBCDIC
454 environments use 37. The corresponding values for CRLF are 3349 and 3365. The
455 default should normally correspond to the standard sequence for your operating
456 system.
457 .sp
459 .sp
460 The output is an integer whose value indicates what character sequences the \eR
461 escape sequence matches by default. A value of 0 means that \eR matches any
462 Unicode line ending sequence; a value of 1 means that \eR matches only CR, LF,
463 or CRLF. The default can be overridden when a pattern is compiled or matched.
464 .sp
466 .sp
467 The output is an integer that contains the number of bytes used for internal
468 linkage in compiled regular expressions. For the 8-bit library, the value can
469 be 2, 3, or 4. For the 16-bit library, the value is either 2 or 4 and is still
470 a number of bytes. For the 32-bit library, the value is either 2 or 4 and is
471 still a number of bytes. The default value of 2 is sufficient for all but the
472 most massive patterns, since it allows the compiled pattern to be up to 64K in
473 size. Larger values allow larger regular expressions to be compiled, at the
474 expense of slower matching.
475 .sp
477 .sp
478 The output is an integer that contains the threshold above which the POSIX
479 interface uses \fBmalloc()\fP for output vectors. Further details are given in
480 the
481 .\" HREF
482 \fBpcreposix\fP
483 .\"
484 documentation.
485 .sp
487 .sp
488 The output is a long integer that gives the default limit for the number of
489 internal matching function calls in a \fBpcre_exec()\fP execution. Further
490 details are given with \fBpcre_exec()\fP below.
491 .sp
493 .sp
494 The output is a long integer that gives the default limit for the depth of
495 recursion when calling the internal matching function in a \fBpcre_exec()\fP
496 execution. Further details are given with \fBpcre_exec()\fP below.
497 .sp
499 .sp
500 The output is an integer that is set to one if internal recursion when running
501 \fBpcre_exec()\fP is implemented by recursive function calls that use the stack
502 to remember their state. This is the usual way that PCRE is compiled. The
503 output is zero if PCRE was compiled to use blocks of data on the heap instead
504 of recursive function calls. In this case, \fBpcre_stack_malloc\fP and
505 \fBpcre_stack_free\fP are called to manage memory blocks on the heap, thus
506 avoiding the use of the stack.
507 .
508 .
510 .rs
511 .sp
512 .B pcre *pcre_compile(const char *\fIpattern\fP, int \fIoptions\fP,
513 .ti +5n
514 .B const char **\fIerrptr\fP, int *\fIerroffset\fP,
515 .ti +5n
516 .B const unsigned char *\fItableptr\fP);
517 .sp
518 .B pcre *pcre_compile2(const char *\fIpattern\fP, int \fIoptions\fP,
519 .ti +5n
520 .B int *\fIerrorcodeptr\fP,
521 .ti +5n
522 .B const char **\fIerrptr\fP, int *\fIerroffset\fP,
523 .ti +5n
524 .B const unsigned char *\fItableptr\fP);
525 .P
526 Either of the functions \fBpcre_compile()\fP or \fBpcre_compile2()\fP can be
527 called to compile a pattern into an internal form. The only difference between
528 the two interfaces is that \fBpcre_compile2()\fP has an additional argument,
529 \fIerrorcodeptr\fP, via which a numerical error code can be returned. To avoid
530 too much repetition, we refer just to \fBpcre_compile()\fP below, but the
531 information applies equally to \fBpcre_compile2()\fP.
532 .P
533 The pattern is a C string terminated by a binary zero, and is passed in the
534 \fIpattern\fP argument. A pointer to a single block of memory that is obtained
535 via \fBpcre_malloc\fP is returned. This contains the compiled code and related
536 data. The \fBpcre\fP type is defined for the returned block; this is a typedef
537 for a structure whose contents are not externally defined. It is up to the
538 caller to free the memory (via \fBpcre_free\fP) when it is no longer required.
539 .P
540 Although the compiled code of a PCRE regex is relocatable, that is, it does not
541 depend on memory location, the complete \fBpcre\fP data block is not
542 fully relocatable, because it may contain a copy of the \fItableptr\fP
543 argument, which is an address (see below).
544 .P
545 The \fIoptions\fP argument contains various bit settings that affect the
546 compilation. It should be zero if no options are required. The available
547 options are described below. Some of them (in particular, those that are
548 compatible with Perl, but some others as well) can also be set and unset from
549 within the pattern (see the detailed description in the
550 .\" HREF
551 \fBpcrepattern\fP
552 .\"
553 documentation). For those options that can be different in different parts of
554 the pattern, the contents of the \fIoptions\fP argument specifies their
555 settings at the start of compilation and execution. The PCRE_ANCHORED,
557 PCRE_NO_START_OPTIMIZE options can be set at the time of matching as well as at
558 compile time.
559 .P
560 If \fIerrptr\fP is NULL, \fBpcre_compile()\fP returns NULL immediately.
561 Otherwise, if compilation of a pattern fails, \fBpcre_compile()\fP returns
562 NULL, and sets the variable pointed to by \fIerrptr\fP to point to a textual
563 error message. This is a static string that is part of the library. You must
564 not try to free it. Normally, the offset from the start of the pattern to the
565 byte that was being processed when the error was discovered is placed in the
566 variable pointed to by \fIerroffset\fP, which must not be NULL (if it is, an
567 immediate error is given). However, for an invalid UTF-8 string, the offset is
568 that of the first byte of the failing character.
569 .P
570 Some errors are not detected until the whole pattern has been scanned; in these
571 cases, the offset passed back is the length of the pattern. Note that the
572 offset is in bytes, not characters, even in UTF-8 mode. It may sometimes point
573 into the middle of a UTF-8 character.
574 .P
575 If \fBpcre_compile2()\fP is used instead of \fBpcre_compile()\fP, and the
576 \fIerrorcodeptr\fP argument is not NULL, a non-zero error code number is
577 returned via this argument in the event of an error. This is in addition to the
578 textual error message. Error codes and messages are listed below.
579 .P
580 If the final argument, \fItableptr\fP, is NULL, PCRE uses a default set of
581 character tables that are built when PCRE is compiled, using the default C
582 locale. Otherwise, \fItableptr\fP must be an address that is the result of a
583 call to \fBpcre_maketables()\fP. This value is stored with the compiled
584 pattern, and used again by \fBpcre_exec()\fP, unless another table pointer is
585 passed to it. For more discussion, see the section on locale support below.
586 .P
587 This code fragment shows a typical straightforward call to \fBpcre_compile()\fP:
588 .sp
589 pcre *re;
590 const char *error;
591 int erroffset;
592 re = pcre_compile(
593 "^A.*Z", /* the pattern */
594 0, /* default options */
595 &error, /* for error message */
596 &erroffset, /* for error offset */
597 NULL); /* use default character tables */
598 .sp
599 The following names for option bits are defined in the \fBpcre.h\fP header
600 file:
601 .sp
603 .sp
604 If this bit is set, the pattern is forced to be "anchored", that is, it is
605 constrained to match only at the first matching point in the string that is
606 being searched (the "subject string"). This effect can also be achieved by
607 appropriate constructs in the pattern itself, which is the only way to do it in
608 Perl.
609 .sp
611 .sp
612 If this bit is set, \fBpcre_compile()\fP automatically inserts callout items,
613 all with number 255, before each pattern item. For discussion of the callout
614 facility, see the
615 .\" HREF
616 \fBpcrecallout\fP
617 .\"
618 documentation.
619 .sp
622 .sp
623 These options (which are mutually exclusive) control what the \eR escape
624 sequence matches. The choice is either to match only CR, LF, or CRLF, or to
625 match any Unicode newline sequence. The default is specified when PCRE is
626 built. It can be overridden from within the pattern, or by setting an option
627 when a compiled pattern is matched.
628 .sp
630 .sp
631 If this bit is set, letters in the pattern match both upper and lower case
632 letters. It is equivalent to Perl's /i option, and it can be changed within a
633 pattern by a (?i) option setting. In UTF-8 mode, PCRE always understands the
634 concept of case for characters whose values are less than 128, so caseless
635 matching is always possible. For characters with higher values, the concept of
636 case is supported if PCRE is compiled with Unicode property support, but not
637 otherwise. If you want to use caseless matching for characters 128 and above,
638 you must ensure that PCRE is compiled with Unicode property support as well as
639 with UTF-8 support.
640 .sp
642 .sp
643 If this bit is set, a dollar metacharacter in the pattern matches only at the
644 end of the subject string. Without this option, a dollar also matches
645 immediately before a newline at the end of the string (but not before any other
646 newlines). The PCRE_DOLLAR_ENDONLY option is ignored if PCRE_MULTILINE is set.
647 There is no equivalent to this option in Perl, and no way to set it within a
648 pattern.
649 .sp
651 .sp
652 If this bit is set, a dot metacharacter in the pattern matches a character of
653 any value, including one that indicates a newline. However, it only ever
654 matches one character, even if newlines are coded as CRLF. Without this option,
655 a dot does not match when the current position is at a newline. This option is
656 equivalent to Perl's /s option, and it can be changed within a pattern by a
657 (?s) option setting. A negative class such as [^a] always matches newline
658 characters, independent of the setting of this option.
659 .sp
661 .sp
662 If this bit is set, names used to identify capturing subpatterns need not be
663 unique. This can be helpful for certain types of pattern when it is known that
664 only one instance of the named subpattern can ever be matched. There are more
665 details of named subpatterns below; see also the
666 .\" HREF
667 \fBpcrepattern\fP
668 .\"
669 documentation.
670 .sp
672 .sp
673 If this bit is set, white space data characters in the pattern are totally
674 ignored except when escaped or inside a character class. White space does not
675 include the VT character (code 11). In addition, characters between an
676 unescaped # outside a character class and the next newline, inclusive, are also
677 ignored. This is equivalent to Perl's /x option, and it can be changed within a
678 pattern by a (?x) option setting.
679 .P
680 Which characters are interpreted as newlines is controlled by the options
681 passed to \fBpcre_compile()\fP or by a special sequence at the start of the
682 pattern, as described in the section entitled
683 .\" HTML <a href="pcrepattern.html#newlines">
684 .\" </a>
685 "Newline conventions"
686 .\"
687 in the \fBpcrepattern\fP documentation. Note that the end of this type of
688 comment is a literal newline sequence in the pattern; escape sequences that
689 happen to represent a newline do not count.
690 .P
691 This option makes it possible to include comments inside complicated patterns.
692 Note, however, that this applies only to data characters. White space characters
693 may never appear within special character sequences in a pattern, for example
694 within the sequence (?( that introduces a conditional subpattern.
695 .sp
697 .sp
698 This option was invented in order to turn on additional functionality of PCRE
699 that is incompatible with Perl, but it is currently of very little use. When
700 set, any backslash in a pattern that is followed by a letter that has no
701 special meaning causes an error, thus reserving these combinations for future
702 expansion. By default, as in Perl, a backslash followed by a letter with no
703 special meaning is treated as a literal. (Perl can, however, be persuaded to
704 give an error for this, by running it with the -w option.) There are at present
705 no other features controlled by this option. It can also be set by a (?X)
706 option setting within a pattern.
707 .sp
709 .sp
710 If this option is set, an unanchored pattern is required to match before or at
711 the first newline in the subject string, though the matched text may continue
712 over the newline.
713 .sp
715 .sp
716 If this option is set, PCRE's behaviour is changed in some ways so that it is
717 compatible with JavaScript rather than Perl. The changes are as follows:
718 .P
719 (1) A lone closing square bracket in a pattern causes a compile-time error,
720 because this is illegal in JavaScript (by default it is treated as a data
721 character). Thus, the pattern AB]CD becomes illegal when this option is set.
722 .P
723 (2) At run time, a back reference to an unset subpattern group matches an empty
724 string (by default this causes the current matching alternative to fail). A
725 pattern such as (\e1)(a) succeeds when this option is set (assuming it can find
726 an "a" in the subject), whereas it fails by default, for Perl compatibility.
727 .P
728 (3) \eU matches an upper case "U" character; by default \eU causes a compile
729 time error (Perl uses \eU to upper case subsequent characters).
730 .P
731 (4) \eu matches a lower case "u" character unless it is followed by four
732 hexadecimal digits, in which case the hexadecimal number defines the code point
733 to match. By default, \eu causes a compile time error (Perl uses it to upper
734 case the following character).
735 .P
736 (5) \ex matches a lower case "x" character unless it is followed by two
737 hexadecimal digits, in which case the hexadecimal number defines the code point
738 to match. By default, as in Perl, a hexadecimal number is always expected after
739 \ex, but it may have zero, one, or two digits (so, for example, \exz matches a
740 binary zero character followed by z).
741 .sp
743 .sp
744 By default, PCRE treats the subject string as consisting of a single line of
745 characters (even if it actually contains newlines). The "start of line"
746 metacharacter (^) matches only at the start of the string, while the "end of
747 line" metacharacter ($) matches only at the end of the string, or before a
748 terminating newline (unless PCRE_DOLLAR_ENDONLY is set). This is the same as
749 Perl.
750 .P
751 When PCRE_MULTILINE it is set, the "start of line" and "end of line" constructs
752 match immediately following or immediately before internal newlines in the
753 subject string, respectively, as well as at the very start and end. This is
754 equivalent to Perl's /m option, and it can be changed within a pattern by a
755 (?m) option setting. If there are no newlines in a subject string, or no
756 occurrences of ^ or $ in a pattern, setting PCRE_MULTILINE has no effect.
757 .sp
763 .sp
764 These options override the default newline definition that was chosen when PCRE
765 was built. Setting the first or the second specifies that a newline is
766 indicated by a single character (CR or LF, respectively). Setting
767 PCRE_NEWLINE_CRLF specifies that a newline is indicated by the two-character
768 CRLF sequence. Setting PCRE_NEWLINE_ANYCRLF specifies that any of the three
769 preceding sequences should be recognized. Setting PCRE_NEWLINE_ANY specifies
770 that any Unicode newline sequence should be recognized.
771 .P
772 In an ASCII/Unicode environment, the Unicode newline sequences are the three
773 just mentioned, plus the single characters VT (vertical tab, U+000B), FF (form
774 feed, U+000C), NEL (next line, U+0085), LS (line separator, U+2028), and PS
775 (paragraph separator, U+2029). For the 8-bit library, the last two are
776 recognized only in UTF-8 mode.
777 .P
778 When PCRE is compiled to run in an EBCDIC (mainframe) environment, the code for
779 CR is 0x0d, the same as ASCII. However, the character code for LF is normally
780 0x15, though in some EBCDIC environments 0x25 is used. Whichever of these is
781 not LF is made to correspond to Unicode's NEL character. EBCDIC codes are all
782 less than 256. For more details, see the
783 .\" HREF
784 \fBpcrebuild\fP
785 .\"
786 documentation.
787 .P
788 The newline setting in the options word uses three bits that are treated
789 as a number, giving eight possibilities. Currently only six are used (default
790 plus the five values above). This means that if you set more than one newline
791 option, the combination may or may not be sensible. For example,
793 other combinations may yield unused numbers and cause an error.
794 .P
795 The only time that a line break in a pattern is specially recognized when
796 compiling is when PCRE_EXTENDED is set. CR and LF are white space characters,
797 and so are ignored in this mode. Also, an unescaped # outside a character class
798 indicates a comment that lasts until after the next line break sequence. In
799 other circumstances, line break sequences in patterns are treated as literal
800 data.
801 .P
802 The newline option that is set at compile time becomes the default that is used
803 for \fBpcre_exec()\fP and \fBpcre_dfa_exec()\fP, but it can be overridden.
804 .sp
806 .sp
807 If this option is set, it disables the use of numbered capturing parentheses in
808 the pattern. Any opening parenthesis that is not followed by ? behaves as if it
809 were followed by ?: but named parentheses can still be used for capturing (and
810 they acquire numbers in the usual way). There is no equivalent of this option
811 in Perl.
812 .sp
814 .sp
815 This is an option that acts at matching time; that is, it is really an option
816 for \fBpcre_exec()\fP or \fBpcre_dfa_exec()\fP. If it is set at compile time,
817 it is remembered with the compiled pattern and assumed at matching time. For
818 details see the discussion of PCRE_NO_START_OPTIMIZE
819 .\" HTML <a href="#execoptions">
820 .\" </a>
821 below.
822 .\"
823 .sp
825 .sp
826 This option changes the way PCRE processes \eB, \eb, \eD, \ed, \eS, \es, \eW,
827 \ew, and some of the POSIX character classes. By default, only ASCII characters
828 are recognized, but if PCRE_UCP is set, Unicode properties are used instead to
829 classify characters. More details are given in the section on
830 .\" HTML <a href="pcre.html#genericchartypes">
831 .\" </a>
832 generic character types
833 .\"
834 in the
835 .\" HREF
836 \fBpcrepattern\fP
837 .\"
838 page. If you set PCRE_UCP, matching one of the items it affects takes much
839 longer. The option is available only if PCRE has been compiled with Unicode
840 property support.
841 .sp
843 .sp
844 This option inverts the "greediness" of the quantifiers so that they are not
845 greedy by default, but become greedy if followed by "?". It is not compatible
846 with Perl. It can also be set by a (?U) option setting within the pattern.
847 .sp
849 .sp
850 This option causes PCRE to regard both the pattern and the subject as strings
851 of UTF-8 characters instead of single-byte strings. However, it is available
852 only when PCRE is built to include UTF support. If not, the use of this option
853 provokes an error. Details of how this option changes the behaviour of PCRE are
854 given in the
855 .\" HREF
856 \fBpcreunicode\fP
857 .\"
858 page.
859 .sp
861 .sp
862 When PCRE_UTF8 is set, the validity of the pattern as a UTF-8 string is
863 automatically checked. There is a discussion about the
864 .\" HTML <a href="pcreunicode.html#utf8strings">
865 .\" </a>
866 validity of UTF-8 strings
867 .\"
868 in the
869 .\" HREF
870 \fBpcreunicode\fP
871 .\"
872 page. If an invalid UTF-8 sequence is found, \fBpcre_compile()\fP returns an
873 error. If you already know that your pattern is valid, and you want to skip
874 this check for performance reasons, you can set the PCRE_NO_UTF8_CHECK option.
875 When it is set, the effect of passing an invalid UTF-8 string as a pattern is
876 undefined. It may cause your program to crash. Note that this option can also
877 be passed to \fBpcre_exec()\fP and \fBpcre_dfa_exec()\fP, to suppress the
878 validity checking of subject strings only. If the same string is being matched
879 many times, the option can be safely set for the second and subsequent
880 matchings to improve performance.
881 .
882 .
884 .rs
885 .sp
886 The following table lists the error codes than may be returned by
887 \fBpcre_compile2()\fP, along with the error messages that may be returned by
888 both compiling functions. Note that error messages are always 8-bit ASCII
889 strings, even in 16-bit or 32-bit mode. As PCRE has developed, some error codes
890 have fallen out of use. To avoid confusion, they have not been re-used.
891 .sp
892 0 no error
893 1 \e at end of pattern
894 2 \ec at end of pattern
895 3 unrecognized character follows \e
896 4 numbers out of order in {} quantifier
897 5 number too big in {} quantifier
898 6 missing terminating ] for character class
899 7 invalid escape sequence in character class
900 8 range out of order in character class
901 9 nothing to repeat
902 10 [this code is not in use]
903 11 internal error: unexpected repeat
904 12 unrecognized character after (? or (?-
905 13 POSIX named classes are supported only within a class
906 14 missing )
907 15 reference to non-existent subpattern
908 16 erroffset passed as NULL
909 17 unknown option bit(s) set
910 18 missing ) after comment
911 19 [this code is not in use]
912 20 regular expression is too large
913 21 failed to get memory
914 22 unmatched parentheses
915 23 internal error: code overflow
916 24 unrecognized character after (?<
917 25 lookbehind assertion is not fixed length
918 26 malformed number or name after (?(
919 27 conditional group contains more than two branches
920 28 assertion expected after (?(
921 29 (?R or (?[+-]digits must be followed by )
922 30 unknown POSIX class name
923 31 POSIX collating elements are not supported
924 32 this version of PCRE is compiled without UTF support
925 33 [this code is not in use]
926 34 character value in \ex{...} sequence is too large
927 35 invalid condition (?(0)
928 36 \eC not allowed in lookbehind assertion
929 37 PCRE does not support \eL, \el, \eN{name}, \eU, or \eu
930 38 number after (?C is > 255
931 39 closing ) for (?C expected
932 40 recursive call could loop indefinitely
933 41 unrecognized character after (?P
934 42 syntax error in subpattern name (missing terminator)
935 43 two named subpatterns have the same name
936 44 invalid UTF-8 string (specifically UTF-8)
937 45 support for \eP, \ep, and \eX has not been compiled
938 46 malformed \eP or \ep sequence
939 47 unknown property name after \eP or \ep
940 48 subpattern name is too long (maximum 32 characters)
941 49 too many named subpatterns (maximum 10000)
942 50 [this code is not in use]
943 51 octal value is greater than \e377 in 8-bit non-UTF-8 mode
944 52 internal error: overran compiling workspace
945 53 internal error: previously-checked referenced subpattern
946 not found
947 54 DEFINE group contains more than one branch
948 55 repeating a DEFINE group is not allowed
949 56 inconsistent NEWLINE options
950 57 \eg is not followed by a braced, angle-bracketed, or quoted
951 name/number or by a plain number
952 58 a numbered reference must not be zero
953 59 an argument is not allowed for (*ACCEPT), (*FAIL), or (*COMMIT)
954 60 (*VERB) not recognized
955 61 number is too big
956 62 subpattern name expected
957 63 digit expected after (?+
958 64 ] is an invalid data character in JavaScript compatibility mode
959 65 different names for subpatterns of the same number are
960 not allowed
961 66 (*MARK) must have an argument
962 67 this version of PCRE is not compiled with Unicode property
963 support
964 68 \ec must be followed by an ASCII character
965 69 \ek is not followed by a braced, angle-bracketed, or quoted name
966 70 internal error: unknown opcode in find_fixedlength()
967 71 \eN is not supported in a class
968 72 too many forward references
969 73 disallowed Unicode code point (>= 0xd800 && <= 0xdfff)
970 74 invalid UTF-16 string (specifically UTF-16)
971 75 name is too long in (*MARK), (*PRUNE), (*SKIP), or (*THEN)
972 76 character value in \eu.... sequence is too large
973 77 invalid UTF-32 string (specifically UTF-32)
974 .sp
975 The numbers 32 and 10000 in errors 48 and 49 are defaults; different values may
976 be used if the limits were changed when PCRE was built.
977 .
978 .
979 .\" HTML <a name="studyingapattern"></a>
981 .rs
982 .sp
983 .B pcre_extra *pcre_study(const pcre *\fIcode\fP, int \fIoptions\fP
984 .ti +5n
985 .B const char **\fIerrptr\fP);
986 .PP
987 If a compiled pattern is going to be used several times, it is worth spending
988 more time analyzing it in order to speed up the time taken for matching. The
989 function \fBpcre_study()\fP takes a pointer to a compiled pattern as its first
990 argument. If studying the pattern produces additional information that will
991 help speed up matching, \fBpcre_study()\fP returns a pointer to a
992 \fBpcre_extra\fP block, in which the \fIstudy_data\fP field points to the
993 results of the study.
994 .P
995 The returned value from \fBpcre_study()\fP can be passed directly to
996 \fBpcre_exec()\fP or \fBpcre_dfa_exec()\fP. However, a \fBpcre_extra\fP block
997 also contains other fields that can be set by the caller before the block is
998 passed; these are described
999 .\" HTML <a href="#extradata">
1000 .\" </a>
1001 below
1002 .\"
1003 in the section on matching a pattern.
1004 .P
1005 If studying the pattern does not produce any useful information,
1006 \fBpcre_study()\fP returns NULL by default. In that circumstance, if the
1007 calling program wants to pass any of the other fields to \fBpcre_exec()\fP or
1008 \fBpcre_dfa_exec()\fP, it must set up its own \fBpcre_extra\fP block. However,
1009 if \fBpcre_study()\fP is called with the PCRE_STUDY_EXTRA_NEEDED option, it
1010 returns a \fBpcre_extra\fP block even if studying did not find any additional
1011 information. It may still return NULL, however, if an error occurs in
1012 \fBpcre_study()\fP.
1013 .P
1014 The second argument of \fBpcre_study()\fP contains option bits. There are three
1015 further options in addition to PCRE_STUDY_EXTRA_NEEDED:
1016 .sp
1020 .sp
1021 If any of these are set, and the just-in-time compiler is available, the
1022 pattern is further compiled into machine code that executes much faster than
1023 the \fBpcre_exec()\fP interpretive matching function. If the just-in-time
1024 compiler is not available, these options are ignored. All undefined bits in the
1025 \fIoptions\fP argument must be zero.
1026 .P
1027 JIT compilation is a heavyweight optimization. It can take some time for
1028 patterns to be analyzed, and for one-off matches and simple patterns the
1029 benefit of faster execution might be offset by a much slower study time.
1030 Not all patterns can be optimized by the JIT compiler. For those that cannot be
1031 handled, matching automatically falls back to the \fBpcre_exec()\fP
1032 interpreter. For more details, see the
1033 .\" HREF
1034 \fBpcrejit\fP
1035 .\"
1036 documentation.
1037 .P
1038 The third argument for \fBpcre_study()\fP is a pointer for an error message. If
1039 studying succeeds (even if no data is returned), the variable it points to is
1040 set to NULL. Otherwise it is set to point to a textual error message. This is a
1041 static string that is part of the library. You must not try to free it. You
1042 should test the error pointer for NULL after calling \fBpcre_study()\fP, to be
1043 sure that it has run successfully.
1044 .P
1045 When you are finished with a pattern, you can free the memory used for the
1046 study data by calling \fBpcre_free_study()\fP. This function was added to the
1047 API for release 8.20. For earlier versions, the memory could be freed with
1048 \fBpcre_free()\fP, just like the pattern itself. This will still work in cases
1049 where JIT optimization is not used, but it is advisable to change to the new
1050 function when convenient.
1051 .P
1052 This is a typical way in which \fBpcre_study\fP() is used (except that in a
1053 real application there should be tests for errors):
1054 .sp
1055 int rc;
1056 pcre *re;
1057 pcre_extra *sd;
1058 re = pcre_compile("pattern", 0, &error, &erroroffset, NULL);
1059 sd = pcre_study(
1060 re, /* result of pcre_compile() */
1061 0, /* no options */
1062 &error); /* set to NULL or points to a message */
1063 rc = pcre_exec( /* see below for details of pcre_exec() options */
1064 re, sd, "subject", 7, 0, 0, ovector, 30);
1065 ...
1066 pcre_free_study(sd);
1067 pcre_free(re);
1068 .sp
1069 Studying a pattern does two things: first, a lower bound for the length of
1070 subject string that is needed to match the pattern is computed. This does not
1071 mean that there are any strings of that length that match, but it does
1072 guarantee that no shorter strings match. The value is used to avoid wasting
1073 time by trying to match strings that are shorter than the lower bound. You can
1074 find out the value in a calling program via the \fBpcre_fullinfo()\fP function.
1075 .P
1076 Studying a pattern is also useful for non-anchored patterns that do not have a
1077 single fixed starting character. A bitmap of possible starting bytes is
1078 created. This speeds up finding a position in the subject at which to start
1079 matching. (In 16-bit mode, the bitmap is used for 16-bit values less than 256.
1080 In 32-bit mode, the bitmap is used for 32-bit values less than 256.)
1081 .P
1082 These two optimizations apply to both \fBpcre_exec()\fP and
1083 \fBpcre_dfa_exec()\fP, and the information is also used by the JIT compiler.
1084 The optimizations can be disabled by setting the PCRE_NO_START_OPTIMIZE option
1085 when calling \fBpcre_exec()\fP or \fBpcre_dfa_exec()\fP, but if this is done,
1086 JIT execution is also disabled. You might want to do this if your pattern
1087 contains callouts or (*MARK) and you want to make use of these facilities in
1088 cases where matching fails. See the discussion of PCRE_NO_START_OPTIMIZE
1089 .\" HTML <a href="#execoptions">
1090 .\" </a>
1091 below.
1092 .\"
1093 .
1094 .
1095 .\" HTML <a name="localesupport"></a>
1097 .rs
1098 .sp
1099 PCRE handles caseless matching, and determines whether characters are letters,
1100 digits, or whatever, by reference to a set of tables, indexed by character
1101 value. When running in UTF-8 mode, this applies only to characters
1102 with codes less than 128. By default, higher-valued codes never match escapes
1103 such as \ew or \ed, but they can be tested with \ep if PCRE is built with
1104 Unicode character property support. Alternatively, the PCRE_UCP option can be
1105 set at compile time; this causes \ew and friends to use Unicode property
1106 support instead of built-in tables. The use of locales with Unicode is
1107 discouraged. If you are handling characters with codes greater than 128, you
1108 should either use UTF-8 and Unicode, or use locales, but not try to mix the
1109 two.
1110 .P
1111 PCRE contains an internal set of tables that are used when the final argument
1112 of \fBpcre_compile()\fP is NULL. These are sufficient for many applications.
1113 Normally, the internal tables recognize only ASCII characters. However, when
1114 PCRE is built, it is possible to cause the internal tables to be rebuilt in the
1115 default "C" locale of the local system, which may cause them to be different.
1116 .P
1117 The internal tables can always be overridden by tables supplied by the
1118 application that calls PCRE. These may be created in a different locale from
1119 the default. As more and more applications change to using Unicode, the need
1120 for this locale support is expected to die away.
1121 .P
1122 External tables are built by calling the \fBpcre_maketables()\fP function,
1123 which has no arguments, in the relevant locale. The result can then be passed
1124 to \fBpcre_compile()\fP or \fBpcre_exec()\fP as often as necessary. For
1125 example, to build and use tables that are appropriate for the French locale
1126 (where accented characters with values greater than 128 are treated as letters),
1127 the following code could be used:
1128 .sp
1129 setlocale(LC_CTYPE, "fr_FR");
1130 tables = pcre_maketables();
1131 re = pcre_compile(..., tables);
1132 .sp
1133 The locale name "fr_FR" is used on Linux and other Unix-like systems; if you
1134 are using Windows, the name for the French locale is "french".
1135 .P
1136 When \fBpcre_maketables()\fP runs, the tables are built in memory that is
1137 obtained via \fBpcre_malloc\fP. It is the caller's responsibility to ensure
1138 that the memory containing the tables remains available for as long as it is
1139 needed.
1140 .P
1141 The pointer that is passed to \fBpcre_compile()\fP is saved with the compiled
1142 pattern, and the same tables are used via this pointer by \fBpcre_study()\fP
1143 and normally also by \fBpcre_exec()\fP. Thus, by default, for any single
1144 pattern, compilation, studying and matching all happen in the same locale, but
1145 different patterns can be compiled in different locales.
1146 .P
1147 It is possible to pass a table pointer or NULL (indicating the use of the
1148 internal tables) to \fBpcre_exec()\fP. Although not intended for this purpose,
1149 this facility could be used to match a pattern in a different locale from the
1150 one in which it was compiled. Passing table pointers at run time is discussed
1151 below in the section on matching a pattern.
1152 .
1153 .
1154 .\" HTML <a name="infoaboutpattern"></a>
1156 .rs
1157 .sp
1158 .B int pcre_fullinfo(const pcre *\fIcode\fP, "const pcre_extra *\fIextra\fP,"
1159 .ti +5n
1160 .B int \fIwhat\fP, void *\fIwhere\fP);
1161 .PP
1162 The \fBpcre_fullinfo()\fP function returns information about a compiled
1163 pattern. It replaces the \fBpcre_info()\fP function, which was removed from the
1164 library at version 8.30, after more than 10 years of obsolescence.
1165 .P
1166 The first argument for \fBpcre_fullinfo()\fP is a pointer to the compiled
1167 pattern. The second argument is the result of \fBpcre_study()\fP, or NULL if
1168 the pattern was not studied. The third argument specifies which piece of
1169 information is required, and the fourth argument is a pointer to a variable
1170 to receive the data. The yield of the function is zero for success, or one of
1171 the following negative numbers:
1172 .sp
1173 PCRE_ERROR_NULL the argument \fIcode\fP was NULL
1174 the argument \fIwhere\fP was NULL
1175 PCRE_ERROR_BADMAGIC the "magic number" was not found
1176 PCRE_ERROR_BADENDIANNESS the pattern was compiled with different
1177 endianness
1178 PCRE_ERROR_BADOPTION the value of \fIwhat\fP was invalid
1179 .sp
1180 The "magic number" is placed at the start of each compiled pattern as an simple
1181 check against passing an arbitrary memory pointer. The endianness error can
1182 occur if a compiled pattern is saved and reloaded on a different host. Here is
1183 a typical call of \fBpcre_fullinfo()\fP, to obtain the length of the compiled
1184 pattern:
1185 .sp
1186 int rc;
1187 size_t length;
1188 rc = pcre_fullinfo(
1189 re, /* result of pcre_compile() */
1190 sd, /* result of pcre_study(), or NULL */
1191 PCRE_INFO_SIZE, /* what is required */
1192 &length); /* where to put the data */
1193 .sp
1194 The possible values for the third argument are defined in \fBpcre.h\fP, and are
1195 as follows:
1196 .sp
1198 .sp
1199 Return the number of the highest back reference in the pattern. The fourth
1200 argument should point to an \fBint\fP variable. Zero is returned if there are
1201 no back references.
1202 .sp
1204 .sp
1205 Return the number of capturing subpatterns in the pattern. The fourth argument
1206 should point to an \fBint\fP variable.
1207 .sp
1209 .sp
1210 Return a pointer to the internal default character tables within PCRE. The
1211 fourth argument should point to an \fBunsigned char *\fP variable. This
1212 information call is provided for internal use by the \fBpcre_study()\fP
1213 function. External callers can cause PCRE to use its internal tables by passing
1214 a NULL table pointer.
1215 .sp
1217 .sp
1218 Return information about the first data unit of any matched string, for a
1219 non-anchored pattern. (The name of this option refers to the 8-bit library,
1220 where data units are bytes.) The fourth argument should point to an \fBint\fP
1221 variable.
1222 .P
1223 If there is a fixed first value, for example, the letter "c" from a pattern
1224 such as (cat|cow|coyote), its value is returned. In the 8-bit library, the
1225 value is always less than 256. In the 16-bit library the value can be up to
1226 0xffff. In the 32-bit library the value can be up to 0x10ffff.
1227 .P
1228 If there is no fixed first value, and if either
1229 .sp
1230 (a) the pattern was compiled with the PCRE_MULTILINE option, and every branch
1231 starts with "^", or
1232 .sp
1233 (b) every branch of the pattern starts with ".*" and PCRE_DOTALL is not set
1234 (if it were set, the pattern would be anchored),
1235 .sp
1236 -1 is returned, indicating that the pattern matches only at the start of a
1237 subject string or after any newline within the string. Otherwise -2 is
1238 returned. For anchored patterns, -2 is returned.
1239 .P
1240 Since for the 32-bit library using the non-UTF-32 mode, this function is unable
1241 to return the full 32-bit range of the character, this value is deprecated;
1243 should be used.
1244 .sp
1246 .sp
1247 If the pattern was studied, and this resulted in the construction of a 256-bit
1248 table indicating a fixed set of values for the first data unit in any matching
1249 string, a pointer to the table is returned. Otherwise NULL is returned. The
1250 fourth argument should point to an \fBunsigned char *\fP variable.
1251 .sp
1253 .sp
1254 Return 1 if the pattern contains any explicit matches for CR or LF characters,
1255 otherwise 0. The fourth argument should point to an \fBint\fP variable. An
1256 explicit match is either a literal CR or LF character, or \er or \en.
1257 .sp
1259 .sp
1260 Return 1 if the (?J) or (?-J) option setting is used in the pattern, otherwise
1261 0. The fourth argument should point to an \fBint\fP variable. (?J) and
1262 (?-J) set and unset the local PCRE_DUPNAMES option, respectively.
1263 .sp
1265 .sp
1266 Return 1 if the pattern was studied with one of the JIT options, and
1267 just-in-time compiling was successful. The fourth argument should point to an
1268 \fBint\fP variable. A return value of 0 means that JIT support is not available
1269 in this version of PCRE, or that the pattern was not studied with a JIT option,
1270 or that the JIT compiler could not handle this particular pattern. See the
1271 .\" HREF
1272 \fBpcrejit\fP
1273 .\"
1274 documentation for details of what can and cannot be handled.
1275 .sp
1277 .sp
1278 If the pattern was successfully studied with a JIT option, return the size of
1279 the JIT compiled code, otherwise return zero. The fourth argument should point
1280 to a \fBsize_t\fP variable.
1281 .sp
1283 .sp
1284 Return the value of the rightmost literal data unit that must exist in any
1285 matched string, other than at its start, if such a value has been recorded. The
1286 fourth argument should point to an \fBint\fP variable. If there is no such
1287 value, -1 is returned. For anchored patterns, a last literal value is recorded
1288 only if it follows something of variable length. For example, for the pattern
1289 /^a\ed+z\ed+/ the returned value is "z", but for /^a\edz\ed/ the returned value
1290 is -1.
1291 .P
1292 Since for the 32-bit library using the non-UTF-32 mode, this function is unable
1293 to return the full 32-bit range of the character, this value is deprecated;
1295 be used.
1296 .sp
1298 .sp
1299 Return the number of characters (NB not bytes) in the longest lookbehind
1300 assertion in the pattern. Note that the simple assertions \eb and \eB require a
1301 one-character lookbehind. This information is useful when doing multi-segment
1302 matching using the partial matching facilities.
1303 .sp
1305 .sp
1306 If the pattern was studied and a minimum length for matching subject strings
1307 was computed, its value is returned. Otherwise the returned value is -1. The
1308 value is a number of characters, which in UTF-8 mode may be different from the
1309 number of bytes. The fourth argument should point to an \fBint\fP variable. A
1310 non-negative value is a lower bound to the length of any matching string. There
1311 may not be any strings of that length that do actually match, but every string
1312 that does match is at least that long.
1313 .sp
1317 .sp
1318 PCRE supports the use of named as well as numbered capturing parentheses. The
1319 names are just an additional way of identifying the parentheses, which still
1320 acquire numbers. Several convenience functions such as
1321 \fBpcre_get_named_substring()\fP are provided for extracting captured
1322 substrings by name. It is also possible to extract the data directly, by first
1323 converting the name to a number in order to access the correct pointers in the
1324 output vector (described with \fBpcre_exec()\fP below). To do the conversion,
1325 you need to use the name-to-number map, which is described by these three
1326 values.
1327 .P
1328 The map consists of a number of fixed-size entries. PCRE_INFO_NAMECOUNT gives
1329 the number of entries, and PCRE_INFO_NAMEENTRYSIZE gives the size of each
1330 entry; both of these return an \fBint\fP value. The entry size depends on the
1331 length of the longest name. PCRE_INFO_NAMETABLE returns a pointer to the first
1332 entry of the table. This is a pointer to \fBchar\fP in the 8-bit library, where
1333 the first two bytes of each entry are the number of the capturing parenthesis,
1334 most significant byte first. In the 16-bit library, the pointer points to
1335 16-bit data units, the first of which contains the parenthesis number.
1336 In the 32-bit library, the pointer points to 32-bit data units, the first of
1337 which contains the parenthesis number. The rest
1338 of the entry is the corresponding name, zero terminated.
1339 .P
1340 The names are in alphabetical order. Duplicate names may appear if (?| is used
1341 to create multiple groups with the same number, as described in the
1342 .\" HTML <a href="pcrepattern.html#dupsubpatternnumber">
1343 .\" </a>
1344 section on duplicate subpattern numbers
1345 .\"
1346 in the
1347 .\" HREF
1348 \fBpcrepattern\fP
1349 .\"
1350 page. Duplicate names for subpatterns with different numbers are permitted only
1351 if PCRE_DUPNAMES is set. In all cases of duplicate names, they appear in the
1352 table in the order in which they were found in the pattern. In the absence of
1353 (?| this is the order of increasing number; when (?| is used this is not
1354 necessarily the case because later subpatterns may have lower numbers.
1355 .P
1356 As a simple example of the name/number table, consider the following pattern
1357 after compilation by the 8-bit library (assume PCRE_EXTENDED is set, so white
1358 space - including newlines - is ignored):
1359 .sp
1360 .\" JOIN
1361 (?<date> (?<year>(\ed\ed)?\ed\ed) -
1362 (?<month>\ed\ed) - (?<day>\ed\ed) )
1363 .sp
1364 There are four named subpatterns, so the table has four entries, and each entry
1365 in the table is eight bytes long. The table is as follows, with non-printing
1366 bytes shows in hexadecimal, and undefined bytes shown as ??:
1367 .sp
1368 00 01 d a t e 00 ??
1369 00 05 d a y 00 ?? ??
1370 00 04 m o n t h 00
1371 00 02 y e a r 00 ??
1372 .sp
1373 When writing code to extract data from named subpatterns using the
1374 name-to-number map, remember that the length of the entries is likely to be
1375 different for each compiled pattern.
1376 .sp
1378 .sp
1379 Return 1 if the pattern can be used for partial matching with
1380 \fBpcre_exec()\fP, otherwise 0. The fourth argument should point to an
1381 \fBint\fP variable. From release 8.00, this always returns 1, because the
1382 restrictions that previously applied to partial matching have been lifted. The
1383 .\" HREF
1384 \fBpcrepartial\fP
1385 .\"
1386 documentation gives details of partial matching.
1387 .sp
1389 .sp
1390 Return a copy of the options with which the pattern was compiled. The fourth
1391 argument should point to an \fBunsigned long int\fP variable. These option bits
1392 are those specified in the call to \fBpcre_compile()\fP, modified by any
1393 top-level option settings at the start of the pattern itself. In other words,
1394 they are the options that will be in force when matching starts. For example,
1395 if the pattern /(?im)abc(?-i)d/ is compiled with the PCRE_EXTENDED option, the
1397 .P
1398 A pattern is automatically anchored by PCRE if all of its top-level
1399 alternatives begin with one of the following:
1400 .sp
1401 ^ unless PCRE_MULTILINE is set
1402 \eA always
1403 \eG always
1404 .\" JOIN
1405 .* if PCRE_DOTALL is set and there are no back
1406 references to the subpattern in which .* appears
1407 .sp
1408 For such patterns, the PCRE_ANCHORED bit is set in the options returned by
1409 \fBpcre_fullinfo()\fP.
1410 .sp
1412 .sp
1413 Return the size of the compiled pattern in bytes (for both libraries). The
1414 fourth argument should point to a \fBsize_t\fP variable. This value does not
1415 include the size of the \fBpcre\fP structure that is returned by
1416 \fBpcre_compile()\fP. The value that is passed as the argument to
1417 \fBpcre_malloc()\fP when \fBpcre_compile()\fP is getting memory in which to
1418 place the compiled data is the value returned by this option plus the size of
1419 the \fBpcre\fP structure. Studying a compiled pattern, with or without JIT,
1420 does not alter the value returned by this option.
1421 .sp
1423 .sp
1424 Return the size in bytes of the data block pointed to by the \fIstudy_data\fP
1425 field in a \fBpcre_extra\fP block. If \fBpcre_extra\fP is NULL, or there is no
1426 study data, zero is returned. The fourth argument should point to a
1427 \fBsize_t\fP variable. The \fIstudy_data\fP field is set by \fBpcre_study()\fP
1428 to record information that will speed up matching (see the section entitled
1429 .\" HTML <a href="#studyingapattern">
1430 .\" </a>
1431 "Studying a pattern"
1432 .\"
1433 above). The format of the \fIstudy_data\fP block is private, but its length
1434 is made available via this option so that it can be saved and restored (see the
1435 .\" HREF
1436 \fBpcreprecompile\fP
1437 .\"
1438 documentation for details).
1439 .sp
1441 .sp
1442 Return information about the first data unit of any matched string, for a
1443 non-anchored pattern. The fourth argument should point to an \fBint\fP
1444 variable.
1445 .P
1446 If there is a fixed first value, for example, the letter "c" from a pattern
1447 such as (cat|cow|coyote), 1 is returned, and the character value can be
1448 retrieved using PCRE_INFO_FIRSTCHARACTER.
1449 .P
1450 If there is no fixed first value, and if either
1451 .sp
1452 (a) the pattern was compiled with the PCRE_MULTILINE option, and every branch
1453 starts with "^", or
1454 .sp
1455 (b) every branch of the pattern starts with ".*" and PCRE_DOTALL is not set
1456 (if it were set, the pattern would be anchored),
1457 .sp
1458 2 is returned, indicating that the pattern matches only at the start of a
1459 subject string or after any newline within the string. Otherwise 0 is
1460 returned. For anchored patterns, 0 is returned.
1461 .sp
1463 .sp
1464 Return the fixed first character value, if PCRE_INFO_FIRSTCHARACTERFLAGS
1465 returned 1; otherwise returns 0. The fourth argument should point to an
1466 \fBuint_t\fP variable.
1467 .P
1468 In the 8-bit library, the value is always less than 256. In the 16-bit library
1469 the value can be up to 0xffff. In the 32-bit library in UTF-32 mode the value
1470 can be up to 0x10ffff, and up to 0xffffffff when not using UTF-32 mode.
1471 .P
1472 If there is no fixed first value, and if either
1473 .sp
1474 (a) the pattern was compiled with the PCRE_MULTILINE option, and every branch
1475 starts with "^", or
1476 .sp
1477 (b) every branch of the pattern starts with ".*" and PCRE_DOTALL is not set
1478 (if it were set, the pattern would be anchored),
1479 .sp
1480 -1 is returned, indicating that the pattern matches only at the start of a
1481 subject string or after any newline within the string. Otherwise -2 is
1482 returned. For anchored patterns, -2 is returned.
1483 .sp
1485 .sp
1486 Returns 1 if there is a rightmost literal data unit that must exist in any
1487 matched string, other than at its start. The fourth argument should point to
1488 an \fBint\fP variable. If there is no such value, 0 is returned. If returning
1489 1, the character value itself can be retrieved using PCRE_INFO_REQUIREDCHAR.
1490 .P
1491 For anchored patterns, a last literal value is recorded only if it follows
1492 something of variable length. For example, for the pattern /^a\ed+z\ed+/ the
1493 returned value 1 (with "z" returned from PCRE_INFO_REQUIREDCHAR), but for
1494 /^a\edz\ed/ the returned value is 0.
1495 .sp
1497 .sp
1498 Return the value of the rightmost literal data unit that must exist in any
1499 matched string, other than at its start, if such a value has been recorded. The
1500 fourth argument should point to an \fBuint32_t\fP variable. If there is no such
1501 value, 0 is returned.
1502 .
1503 .
1505 .rs
1506 .sp
1507 .B int pcre_refcount(pcre *\fIcode\fP, int \fIadjust\fP);
1508 .PP
1509 The \fBpcre_refcount()\fP function is used to maintain a reference count in the
1510 data block that contains a compiled pattern. It is provided for the benefit of
1511 applications that operate in an object-oriented manner, where different parts
1512 of the application may be using the same compiled pattern, but you want to free
1513 the block when they are all done.
1514 .P
1515 When a pattern is compiled, the reference count field is initialized to zero.
1516 It is changed only by calling this function, whose action is to add the
1517 \fIadjust\fP value (which may be positive or negative) to it. The yield of the
1518 function is the new value. However, the value of the count is constrained to
1519 lie between 0 and 65535, inclusive. If the new value is outside these limits,
1520 it is forced to the appropriate limit value.
1521 .P
1522 Except when it is zero, the reference count is not correctly preserved if a
1523 pattern is compiled on one host and then transferred to a host whose byte-order
1524 is different. (This seems a highly unlikely scenario.)
1525 .
1526 .
1528 .rs
1529 .sp
1530 .B int pcre_exec(const pcre *\fIcode\fP, "const pcre_extra *\fIextra\fP,"
1531 .ti +5n
1532 .B "const char *\fIsubject\fP," int \fIlength\fP, int \fIstartoffset\fP,
1533 .ti +5n
1534 .B int \fIoptions\fP, int *\fIovector\fP, int \fIovecsize\fP);
1535 .P
1536 The function \fBpcre_exec()\fP is called to match a subject string against a
1537 compiled pattern, which is passed in the \fIcode\fP argument. If the
1538 pattern was studied, the result of the study should be passed in the
1539 \fIextra\fP argument. You can call \fBpcre_exec()\fP with the same \fIcode\fP
1540 and \fIextra\fP arguments as many times as you like, in order to match
1541 different subject strings with the same pattern.
1542 .P
1543 This function is the main matching facility of the library, and it operates in
1544 a Perl-like manner. For specialist use there is also an alternative matching
1545 function, which is described
1546 .\" HTML <a href="#dfamatch">
1547 .\" </a>
1548 below
1549 .\"
1550 in the section about the \fBpcre_dfa_exec()\fP function.
1551 .P
1552 In most applications, the pattern will have been compiled (and optionally
1553 studied) in the same process that calls \fBpcre_exec()\fP. However, it is
1554 possible to save compiled patterns and study data, and then use them later
1555 in different processes, possibly even on different hosts. For a discussion
1556 about this, see the
1557 .\" HREF
1558 \fBpcreprecompile\fP
1559 .\"
1560 documentation.
1561 .P
1562 Here is an example of a simple call to \fBpcre_exec()\fP:
1563 .sp
1564 int rc;
1565 int ovector[30];
1566 rc = pcre_exec(
1567 re, /* result of pcre_compile() */
1568 NULL, /* we didn't study the pattern */
1569 "some string", /* the subject string */
1570 11, /* the length of the subject string */
1571 0, /* start at offset 0 in the subject */
1572 0, /* default options */
1573 ovector, /* vector of integers for substring information */
1574 30); /* number of elements (NOT size in bytes) */
1575 .
1576 .
1577 .\" HTML <a name="extradata"></a>
1578 .SS "Extra data for \fBpcre_exec()\fR"
1579 .rs
1580 .sp
1581 If the \fIextra\fP argument is not NULL, it must point to a \fBpcre_extra\fP
1582 data block. The \fBpcre_study()\fP function returns such a block (when it
1583 doesn't return NULL), but you can also create one for yourself, and pass
1584 additional information in it. The \fBpcre_extra\fP block contains the following
1585 fields (not necessarily in this order):
1586 .sp
1587 unsigned long int \fIflags\fP;
1588 void *\fIstudy_data\fP;
1589 void *\fIexecutable_jit\fP;
1590 unsigned long int \fImatch_limit\fP;
1591 unsigned long int \fImatch_limit_recursion\fP;
1592 void *\fIcallout_data\fP;
1593 const unsigned char *\fItables\fP;
1594 unsigned char **\fImark\fP;
1595 .sp
1596 In the 16-bit version of this structure, the \fImark\fP field has type
1597 "PCRE_UCHAR16 **".
1598 .sp
1599 In the 32-bit version of this structure, the \fImark\fP field has type
1600 "PCRE_UCHAR32 **".
1601 .P
1602 The \fIflags\fP field is used to specify which of the other fields are set. The
1603 flag bits are:
1604 .sp
1612 .sp
1613 Other flag bits should be set to zero. The \fIstudy_data\fP field and sometimes
1614 the \fIexecutable_jit\fP field are set in the \fBpcre_extra\fP block that is
1615 returned by \fBpcre_study()\fP, together with the appropriate flag bits. You
1616 should not set these yourself, but you may add to the block by setting other
1617 fields and their corresponding flag bits.
1618 .P
1619 The \fImatch_limit\fP field provides a means of preventing PCRE from using up a
1620 vast amount of resources when running patterns that are not going to match,
1621 but which have a very large number of possibilities in their search trees. The
1622 classic example is a pattern that uses nested unlimited repeats.
1623 .P
1624 Internally, \fBpcre_exec()\fP uses a function called \fBmatch()\fP, which it
1625 calls repeatedly (sometimes recursively). The limit set by \fImatch_limit\fP is
1626 imposed on the number of times this function is called during a match, which
1627 has the effect of limiting the amount of backtracking that can take place. For
1628 patterns that are not anchored, the count restarts from zero for each position
1629 in the subject string.
1630 .P
1631 When \fBpcre_exec()\fP is called with a pattern that was successfully studied
1632 with a JIT option, the way that the matching is executed is entirely different.
1633 However, there is still the possibility of runaway matching that goes on for a
1634 very long time, and so the \fImatch_limit\fP value is also used in this case
1635 (but in a different way) to limit how long the matching can continue.
1636 .P
1637 The default value for the limit can be set when PCRE is built; the default
1638 default is 10 million, which handles all but the most extreme cases. You can
1639 override the default by suppling \fBpcre_exec()\fP with a \fBpcre_extra\fP
1640 block in which \fImatch_limit\fP is set, and PCRE_EXTRA_MATCH_LIMIT is set in
1641 the \fIflags\fP field. If the limit is exceeded, \fBpcre_exec()\fP returns
1643 .P
1644 The \fImatch_limit_recursion\fP field is similar to \fImatch_limit\fP, but
1645 instead of limiting the total number of times that \fBmatch()\fP is called, it
1646 limits the depth of recursion. The recursion depth is a smaller number than the
1647 total number of calls, because not all calls to \fBmatch()\fP are recursive.
1648 This limit is of use only if it is set smaller than \fImatch_limit\fP.
1649 .P
1650 Limiting the recursion depth limits the amount of machine stack that can be
1651 used, or, when PCRE has been compiled to use memory on the heap instead of the
1652 stack, the amount of heap memory that can be used. This limit is not relevant,
1653 and is ignored, when matching is done using JIT compiled code.
1654 .P
1655 The default value for \fImatch_limit_recursion\fP can be set when PCRE is
1656 built; the default default is the same value as the default for
1657 \fImatch_limit\fP. You can override the default by suppling \fBpcre_exec()\fP
1658 with a \fBpcre_extra\fP block in which \fImatch_limit_recursion\fP is set, and
1659 PCRE_EXTRA_MATCH_LIMIT_RECURSION is set in the \fIflags\fP field. If the limit
1660 is exceeded, \fBpcre_exec()\fP returns PCRE_ERROR_RECURSIONLIMIT.
1661 .P
1662 The \fIcallout_data\fP field is used in conjunction with the "callout" feature,
1663 and is described in the
1664 .\" HREF
1665 \fBpcrecallout\fP
1666 .\"
1667 documentation.
1668 .P
1669 The \fItables\fP field is used to pass a character tables pointer to
1670 \fBpcre_exec()\fP; this overrides the value that is stored with the compiled
1671 pattern. A non-NULL value is stored with the compiled pattern only if custom
1672 tables were supplied to \fBpcre_compile()\fP via its \fItableptr\fP argument.
1673 If NULL is passed to \fBpcre_exec()\fP using this mechanism, it forces PCRE's
1674 internal tables to be used. This facility is helpful when re-using patterns
1675 that have been saved after compiling with an external set of tables, because
1676 the external tables might be at a different address when \fBpcre_exec()\fP is
1677 called. See the
1678 .\" HREF
1679 \fBpcreprecompile\fP
1680 .\"
1681 documentation for a discussion of saving compiled patterns for later use.
1682 .P
1683 If PCRE_EXTRA_MARK is set in the \fIflags\fP field, the \fImark\fP field must
1684 be set to point to a suitable variable. If the pattern contains any
1685 backtracking control verbs such as (*MARK:NAME), and the execution ends up with
1686 a name to pass back, a pointer to the name string (zero terminated) is placed
1687 in the variable pointed to by the \fImark\fP field. The names are within the
1688 compiled pattern; if you wish to retain such a name you must copy it before
1689 freeing the memory of a compiled pattern. If there is no name to pass back, the
1690 variable pointed to by the \fImark\fP field is set to NULL. For details of the
1691 backtracking control verbs, see the section entitled
1692 .\" HTML <a href="pcrepattern#backtrackcontrol">
1693 .\" </a>
1694 "Backtracking control"
1695 .\"
1696 in the
1697 .\" HREF
1698 \fBpcrepattern\fP
1699 .\"
1700 documentation.
1701 .
1702 .
1703 .\" HTML <a name="execoptions"></a>
1704 .SS "Option bits for \fBpcre_exec()\fP"
1705 .rs
1706 .sp
1707 The unused bits of the \fIoptions\fP argument for \fBpcre_exec()\fP must be
1708 zero. The only bits that may be set are PCRE_ANCHORED, PCRE_NEWLINE_\fIxxx\fP,
1712 .P
1713 If the pattern was successfully studied with one of the just-in-time (JIT)
1714 compile options, the only supported options for JIT execution are
1717 unsupported option is used, JIT execution is disabled and the normal
1718 interpretive code in \fBpcre_exec()\fP is run.
1719 .sp
1721 .sp
1722 The PCRE_ANCHORED option limits \fBpcre_exec()\fP to matching at the first
1723 matching position. If a pattern was compiled with PCRE_ANCHORED, or turned out
1724 to be anchored by virtue of its contents, it cannot be made unachored at
1725 matching time.
1726 .sp
1729 .sp
1730 These options (which are mutually exclusive) control what the \eR escape
1731 sequence matches. The choice is either to match only CR, LF, or CRLF, or to
1732 match any Unicode newline sequence. These options override the choice that was
1733 made or defaulted when the pattern was compiled.
1734 .sp
1740 .sp
1741 These options override the newline definition that was chosen or defaulted when
1742 the pattern was compiled. For details, see the description of
1743 \fBpcre_compile()\fP above. During matching, the newline choice affects the
1744 behaviour of the dot, circumflex, and dollar metacharacters. It may also alter
1745 the way the match position is advanced after a match failure for an unanchored
1746 pattern.
1747 .P
1749 match attempt for an unanchored pattern fails when the current position is at a
1750 CRLF sequence, and the pattern contains no explicit matches for CR or LF
1751 characters, the match position is advanced by two characters instead of one, in
1752 other words, to after the CRLF.
1753 .P
1754 The above rule is a compromise that makes the most common cases work as
1755 expected. For example, if the pattern is .+A (and the PCRE_DOTALL option is not
1756 set), it does not match the string "\er\enA" because, after failing at the
1757 start, it skips both the CR and the LF before retrying. However, the pattern
1758 [\er\en]A does match that string, because it contains an explicit CR or LF
1759 reference, and so advances only by one character after the first failure.
1760 .P
1761 An explicit match for CR of LF is either a literal appearance of one of those
1762 characters, or one of the \er or \en escape sequences. Implicit matches such as
1763 [^X] do not count, nor does \es (which includes CR and LF in the characters
1764 that it matches).
1765 .P
1766 Notwithstanding the above, anomalous effects may still occur when CRLF is a
1767 valid newline sequence and explicit \er or \en escapes appear in the pattern.
1768 .sp
1770 .sp
1771 This option specifies that first character of the subject string is not the
1772 beginning of a line, so the circumflex metacharacter should not match before
1773 it. Setting this without PCRE_MULTILINE (at compile time) causes circumflex
1774 never to match. This option affects only the behaviour of the circumflex
1775 metacharacter. It does not affect \eA.
1776 .sp
1778 .sp
1779 This option specifies that the end of the subject string is not the end of a
1780 line, so the dollar metacharacter should not match it nor (except in multiline
1781 mode) a newline immediately before it. Setting this without PCRE_MULTILINE (at
1782 compile time) causes dollar never to match. This option affects only the
1783 behaviour of the dollar metacharacter. It does not affect \eZ or \ez.
1784 .sp
1786 .sp
1787 An empty string is not considered to be a valid match if this option is set. If
1788 there are alternatives in the pattern, they are tried. If all the alternatives
1789 match the empty string, the entire match fails. For example, if the pattern
1790 .sp
1791 a?b?
1792 .sp
1793 is applied to a string not beginning with "a" or "b", it matches an empty
1794 string at the start of the subject. With PCRE_NOTEMPTY set, this match is not
1795 valid, so PCRE searches further into the string for occurrences of "a" or "b".
1796 .sp
1798 .sp
1799 This is like PCRE_NOTEMPTY, except that an empty string match that is not at
1800 the start of the subject is permitted. If the pattern is anchored, such a match
1801 can occur only if the pattern contains \eK.
1802 .P
1803 Perl has no direct equivalent of PCRE_NOTEMPTY or PCRE_NOTEMPTY_ATSTART, but it
1804 does make a special case of a pattern match of the empty string within its
1805 \fBsplit()\fP function, and when using the /g modifier. It is possible to
1806 emulate Perl's behaviour after matching a null string by first trying the match
1807 again at the same offset with PCRE_NOTEMPTY_ATSTART and PCRE_ANCHORED, and then
1808 if that fails, by advancing the starting offset (see below) and trying an
1809 ordinary match again. There is some code that demonstrates how to do this in
1810 the
1811 .\" HREF
1812 \fBpcredemo\fP
1813 .\"
1814 sample program. In the most general case, you have to check to see if the
1815 newline convention recognizes CRLF as a newline, and if so, and the current
1816 character is CR followed by LF, advance the starting offset by two characters
1817 instead of one.
1818 .sp
1820 .sp
1821 There are a number of optimizations that \fBpcre_exec()\fP uses at the start of
1822 a match, in order to speed up the process. For example, if it is known that an
1823 unanchored match must start with a specific character, it searches the subject
1824 for that character, and fails immediately if it cannot find it, without
1825 actually running the main matching function. This means that a special item
1826 such as (*COMMIT) at the start of a pattern is not considered until after a
1827 suitable starting point for the match has been found. When callouts or (*MARK)
1828 items are in use, these "start-up" optimizations can cause them to be skipped
1829 if the pattern is never actually used. The start-up optimizations are in effect
1830 a pre-scan of the subject that takes place before the pattern is run.
1831 .P
1832 The PCRE_NO_START_OPTIMIZE option disables the start-up optimizations, possibly
1833 causing performance to suffer, but ensuring that in cases where the result is
1834 "no match", the callouts do occur, and that items such as (*COMMIT) and (*MARK)
1835 are considered at every possible starting position in the subject string. If
1836 PCRE_NO_START_OPTIMIZE is set at compile time, it cannot be unset at matching
1837 time. The use of PCRE_NO_START_OPTIMIZE disables JIT execution; when it is set,
1838 matching is always done using interpretively.
1839 .P
1840 Setting PCRE_NO_START_OPTIMIZE can change the outcome of a matching operation.
1841 Consider the pattern
1842 .sp
1844 .sp
1845 When this is compiled, PCRE records the fact that a match must start with the
1846 character "A". Suppose the subject string is "DEFABC". The start-up
1847 optimization scans along the subject, finds "A" and runs the first match
1848 attempt from there. The (*COMMIT) item means that the pattern must match the
1849 current starting position, which in this case, it does. However, if the same
1850 match is run with PCRE_NO_START_OPTIMIZE set, the initial scan along the
1851 subject string does not happen. The first match attempt is run starting from
1852 "D" and when this fails, (*COMMIT) prevents any further matches being tried, so
1853 the overall result is "no match". If the pattern is studied, more start-up
1854 optimizations may be used. For example, a minimum length for the subject may be
1855 recorded. Consider the pattern
1856 .sp
1857 (*MARK:A)(X|Y)
1858 .sp
1859 The minimum length for a match is one character. If the subject is "ABC", there
1860 will be attempts to match "ABC", "BC", "C", and then finally an empty string.
1861 If the pattern is studied, the final attempt does not take place, because PCRE
1862 knows that the subject is too short, and so the (*MARK) is never encountered.
1863 In this case, studying the pattern does not affect the overall match result,
1864 which is still "no match", but it does affect the auxiliary information that is
1865 returned.
1866 .sp
1868 .sp
1869 When PCRE_UTF8 is set at compile time, the validity of the subject as a UTF-8
1870 string is automatically checked when \fBpcre_exec()\fP is subsequently called.
1871 The entire string is checked before any other processing takes place. The value
1872 of \fIstartoffset\fP is also checked to ensure that it points to the start of a
1873 UTF-8 character. There is a discussion about the
1874 .\" HTML <a href="pcreunicode.html#utf8strings">
1875 .\" </a>
1876 validity of UTF-8 strings
1877 .\"
1878 in the
1879 .\" HREF
1880 \fBpcreunicode\fP
1881 .\"
1882 page. If an invalid sequence of bytes is found, \fBpcre_exec()\fP returns the
1883 error PCRE_ERROR_BADUTF8 or, if PCRE_PARTIAL_HARD is set and the problem is a
1884 truncated character at the end of the subject, PCRE_ERROR_SHORTUTF8. In both
1885 cases, information about the precise nature of the error may also be returned
1886 (see the descriptions of these errors in the section entitled \fIError return
1887 values from\fP \fBpcre_exec()\fP
1888 .\" HTML <a href="#errorlist">
1889 .\" </a>
1890 below).
1891 .\"
1892 If \fIstartoffset\fP contains a value that does not point to the start of a
1893 UTF-8 character (or to the end of the subject), PCRE_ERROR_BADUTF8_OFFSET is
1894 returned.
1895 .P
1896 If you already know that your subject is valid, and you want to skip these
1897 checks for performance reasons, you can set the PCRE_NO_UTF8_CHECK option when
1898 calling \fBpcre_exec()\fP. You might want to do this for the second and
1899 subsequent calls to \fBpcre_exec()\fP if you are making repeated calls to find
1900 all the matches in a single subject string. However, you should be sure that
1901 the value of \fIstartoffset\fP points to the start of a character (or the end
1902 of the subject). When PCRE_NO_UTF8_CHECK is set, the effect of passing an
1903 invalid string as a subject or an invalid value of \fIstartoffset\fP is
1904 undefined. Your program may crash.
1905 .sp
1908 .sp
1909 These options turn on the partial matching feature. For backwards
1910 compatibility, PCRE_PARTIAL is a synonym for PCRE_PARTIAL_SOFT. A partial match
1911 occurs if the end of the subject string is reached successfully, but there are
1912 not enough subject characters to complete the match. If this happens when
1913 PCRE_PARTIAL_SOFT (but not PCRE_PARTIAL_HARD) is set, matching continues by
1914 testing any remaining alternatives. Only if no complete match can be found is
1915 PCRE_ERROR_PARTIAL returned instead of PCRE_ERROR_NOMATCH. In other words,
1916 PCRE_PARTIAL_SOFT says that the caller is prepared to handle a partial match,
1917 but only if no complete match can be found.
1918 .P
1919 If PCRE_PARTIAL_HARD is set, it overrides PCRE_PARTIAL_SOFT. In this case, if a
1920 partial match is found, \fBpcre_exec()\fP immediately returns
1921 PCRE_ERROR_PARTIAL, without considering any other alternatives. In other words,
1922 when PCRE_PARTIAL_HARD is set, a partial match is considered to be more
1923 important that an alternative complete match.
1924 .P
1925 In both cases, the portion of the string that was inspected when the partial
1926 match was found is set as the first matching string. There is a more detailed
1927 discussion of partial and multi-segment matching, with examples, in the
1928 .\" HREF
1929 \fBpcrepartial\fP
1930 .\"
1931 documentation.
1932 .
1933 .
1934 .SS "The string to be matched by \fBpcre_exec()\fP"
1935 .rs
1936 .sp
1937 The subject string is passed to \fBpcre_exec()\fP as a pointer in
1938 \fIsubject\fP, a length in bytes in \fIlength\fP, and a starting byte offset
1939 in \fIstartoffset\fP. If this is negative or greater than the length of the
1940 subject, \fBpcre_exec()\fP returns PCRE_ERROR_BADOFFSET. When the starting
1941 offset is zero, the search for a match starts at the beginning of the subject,
1942 and this is by far the most common case. In UTF-8 mode, the byte offset must
1943 point to the start of a UTF-8 character (or the end of the subject). Unlike the
1944 pattern string, the subject may contain binary zero bytes.
1945 .P
1946 A non-zero starting offset is useful when searching for another match in the
1947 same subject by calling \fBpcre_exec()\fP again after a previous success.
1948 Setting \fIstartoffset\fP differs from just passing over a shortened string and
1949 setting PCRE_NOTBOL in the case of a pattern that begins with any kind of
1950 lookbehind. For example, consider the pattern
1951 .sp
1952 \eBiss\eB
1953 .sp
1954 which finds occurrences of "iss" in the middle of words. (\eB matches only if
1955 the current position in the subject is not a word boundary.) When applied to
1956 the string "Mississipi" the first call to \fBpcre_exec()\fP finds the first
1957 occurrence. If \fBpcre_exec()\fP is called again with just the remainder of the
1958 subject, namely "issipi", it does not match, because \eB is always false at the
1959 start of the subject, which is deemed to be a word boundary. However, if
1960 \fBpcre_exec()\fP is passed the entire string again, but with \fIstartoffset\fP
1961 set to 4, it finds the second occurrence of "iss" because it is able to look
1962 behind the starting point to discover that it is preceded by a letter.
1963 .P
1964 Finding all the matches in a subject is tricky when the pattern can match an
1965 empty string. It is possible to emulate Perl's /g behaviour by first trying the
1966 match again at the same offset, with the PCRE_NOTEMPTY_ATSTART and
1967 PCRE_ANCHORED options, and then if that fails, advancing the starting offset
1968 and trying an ordinary match again. There is some code that demonstrates how to
1969 do this in the
1970 .\" HREF
1971 \fBpcredemo\fP
1972 .\"
1973 sample program. In the most general case, you have to check to see if the
1974 newline convention recognizes CRLF as a newline, and if so, and the current
1975 character is CR followed by LF, advance the starting offset by two characters
1976 instead of one.
1977 .P
1978 If a non-zero starting offset is passed when the pattern is anchored, one
1979 attempt to match at the given offset is made. This can only succeed if the
1980 pattern does not require the match to be at the start of the subject.
1981 .
1982 .
1983 .SS "How \fBpcre_exec()\fP returns captured substrings"
1984 .rs
1985 .sp
1986 In general, a pattern matches a certain portion of the subject, and in
1987 addition, further substrings from the subject may be picked out by parts of the
1988 pattern. Following the usage in Jeffrey Friedl's book, this is called
1989 "capturing" in what follows, and the phrase "capturing subpattern" is used for
1990 a fragment of a pattern that picks out a substring. PCRE supports several other
1991 kinds of parenthesized subpattern that do not cause substrings to be captured.
1992 .P
1993 Captured substrings are returned to the caller via a vector of integers whose
1994 address is passed in \fIovector\fP. The number of elements in the vector is
1995 passed in \fIovecsize\fP, which must be a non-negative number. \fBNote\fP: this
1996 argument is NOT the size of \fIovector\fP in bytes.
1997 .P
1998 The first two-thirds of the vector is used to pass back captured substrings,
1999 each substring using a pair of integers. The remaining third of the vector is
2000 used as workspace by \fBpcre_exec()\fP while matching capturing subpatterns,
2001 and is not available for passing back information. The number passed in
2002 \fIovecsize\fP should always be a multiple of three. If it is not, it is
2003 rounded down.
2004 .P
2005 When a match is successful, information about captured substrings is returned
2006 in pairs of integers, starting at the beginning of \fIovector\fP, and
2007 continuing up to two-thirds of its length at the most. The first element of
2008 each pair is set to the byte offset of the first character in a substring, and
2009 the second is set to the byte offset of the first character after the end of a
2010 substring. \fBNote\fP: these values are always byte offsets, even in UTF-8
2011 mode. They are not character counts.
2012 .P
2013 The first pair of integers, \fIovector[0]\fP and \fIovector[1]\fP, identify the
2014 portion of the subject string matched by the entire pattern. The next pair is
2015 used for the first capturing subpattern, and so on. The value returned by
2016 \fBpcre_exec()\fP is one more than the highest numbered pair that has been set.
2017 For example, if two substrings have been captured, the returned value is 3. If
2018 there are no capturing subpatterns, the return value from a successful match is
2019 1, indicating that just the first pair of offsets has been set.
2020 .P
2021 If a capturing subpattern is matched repeatedly, it is the last portion of the
2022 string that it matched that is returned.
2023 .P
2024 If the vector is too small to hold all the captured substring offsets, it is
2025 used as far as possible (up to two-thirds of its length), and the function
2026 returns a value of zero. If neither the actual string matched nor any captured
2027 substrings are of interest, \fBpcre_exec()\fP may be called with \fIovector\fP
2028 passed as NULL and \fIovecsize\fP as zero. However, if the pattern contains
2029 back references and the \fIovector\fP is not big enough to remember the related
2030 substrings, PCRE has to get additional memory for use during matching. Thus it
2031 is usually advisable to supply an \fIovector\fP of reasonable size.
2032 .P
2033 There are some cases where zero is returned (indicating vector overflow) when
2034 in fact the vector is exactly the right size for the final match. For example,
2035 consider the pattern
2036 .sp
2037 (a)(?:(b)c|bd)
2038 .sp
2039 If a vector of 6 elements (allowing for only 1 captured substring) is given
2040 with subject string "abd", \fBpcre_exec()\fP will try to set the second
2041 captured string, thereby recording a vector overflow, before failing to match
2042 "c" and backing up to try the second alternative. The zero return, however,
2043 does correctly indicate that the maximum number of slots (namely 2) have been
2044 filled. In similar cases where there is temporary overflow, but the final
2045 number of used slots is actually less than the maximum, a non-zero value is
2046 returned.
2047 .P
2048 The \fBpcre_fullinfo()\fP function can be used to find out how many capturing
2049 subpatterns there are in a compiled pattern. The smallest size for
2050 \fIovector\fP that will allow for \fIn\fP captured substrings, in addition to
2051 the offsets of the substring matched by the whole pattern, is (\fIn\fP+1)*3.
2052 .P
2053 It is possible for capturing subpattern number \fIn+1\fP to match some part of
2054 the subject when subpattern \fIn\fP has not been used at all. For example, if
2055 the string "abc" is matched against the pattern (a|(z))(bc) the return from the
2056 function is 4, and subpatterns 1 and 3 are matched, but 2 is not. When this
2057 happens, both values in the offset pairs corresponding to unused subpatterns
2058 are set to -1.
2059 .P
2060 Offset values that correspond to unused subpatterns at the end of the
2061 expression are also set to -1. For example, if the string "abc" is matched
2062 against the pattern (abc)(x(yz)?)? subpatterns 2 and 3 are not matched. The
2063 return from the function is 2, because the highest used capturing subpattern
2064 number is 1, and the offsets for for the second and third capturing subpatterns
2065 (assuming the vector is large enough, of course) are set to -1.
2066 .P
2067 \fBNote\fP: Elements in the first two-thirds of \fIovector\fP that do not
2068 correspond to capturing parentheses in the pattern are never changed. That is,
2069 if a pattern contains \fIn\fP capturing parentheses, no more than
2070 \fIovector[0]\fP to \fIovector[2n+1]\fP are set by \fBpcre_exec()\fP. The other
2071 elements (in the first two-thirds) retain whatever values they previously had.
2072 .P
2073 Some convenience functions are provided for extracting the captured substrings
2074 as separate strings. These are described below.
2075 .
2076 .
2077 .\" HTML <a name="errorlist"></a>
2078 .SS "Error return values from \fBpcre_exec()\fP"
2079 .rs
2080 .sp
2081 If \fBpcre_exec()\fP fails, it returns a negative number. The following are
2082 defined in the header file:
2083 .sp
2085 .sp
2086 The subject string did not match the pattern.
2087 .sp
2089 .sp
2090 Either \fIcode\fP or \fIsubject\fP was passed as NULL, or \fIovector\fP was
2091 NULL and \fIovecsize\fP was not zero.
2092 .sp
2094 .sp
2095 An unrecognized bit was set in the \fIoptions\fP argument.
2096 .sp
2098 .sp
2099 PCRE stores a 4-byte "magic number" at the start of the compiled code, to catch
2100 the case when it is passed a junk pointer and to detect when a pattern that was
2101 compiled in an environment of one endianness is run in an environment with the
2102 other endianness. This is the error that PCRE gives when the magic number is
2103 not present.
2104 .sp
2106 .sp
2107 While running the pattern match, an unknown item was encountered in the
2108 compiled pattern. This error could be caused by a bug in PCRE or by overwriting
2109 of the compiled pattern.
2110 .sp
2112 .sp
2113 If a pattern contains back references, but the \fIovector\fP that is passed to
2114 \fBpcre_exec()\fP is not big enough to remember the referenced substrings, PCRE
2115 gets a block of memory at the start of matching to use for this purpose. If the
2116 call via \fBpcre_malloc()\fP fails, this error is given. The memory is
2117 automatically freed at the end of matching.
2118 .P
2119 This error is also given if \fBpcre_stack_malloc()\fP fails in
2120 \fBpcre_exec()\fP. This can happen only when PCRE has been compiled with
2121 \fB--disable-stack-for-recursion\fP.
2122 .sp
2124 .sp
2125 This error is used by the \fBpcre_copy_substring()\fP,
2126 \fBpcre_get_substring()\fP, and \fBpcre_get_substring_list()\fP functions (see
2127 below). It is never returned by \fBpcre_exec()\fP.
2128 .sp
2130 .sp
2131 The backtracking limit, as specified by the \fImatch_limit\fP field in a
2132 \fBpcre_extra\fP structure (or defaulted) was reached. See the description
2133 above.
2134 .sp
2136 .sp
2137 This error is never generated by \fBpcre_exec()\fP itself. It is provided for
2138 use by callout functions that want to yield a distinctive error code. See the
2139 .\" HREF
2140 \fBpcrecallout\fP
2141 .\"
2142 documentation for details.
2143 .sp
2145 .sp
2146 A string that contains an invalid UTF-8 byte sequence was passed as a subject,
2147 and the PCRE_NO_UTF8_CHECK option was not set. If the size of the output vector
2148 (\fIovecsize\fP) is at least 2, the byte offset to the start of the the invalid
2149 UTF-8 character is placed in the first element, and a reason code is placed in
2150 the second element. The reason codes are listed in the
2151 .\" HTML <a href="#badutf8reasons">
2152 .\" </a>
2153 following section.
2154 .\"
2155 For backward compatibility, if PCRE_PARTIAL_HARD is set and the problem is a
2156 truncated UTF-8 character at the end of the subject (reason codes 1 to 5),
2157 PCRE_ERROR_SHORTUTF8 is returned instead of PCRE_ERROR_BADUTF8.
2158 .sp
2160 .sp
2161 The UTF-8 byte sequence that was passed as a subject was checked and found to
2162 be valid (the PCRE_NO_UTF8_CHECK option was not set), but the value of
2163 \fIstartoffset\fP did not point to the beginning of a UTF-8 character or the
2164 end of the subject.
2165 .sp
2167 .sp
2168 The subject string did not match, but it did match partially. See the
2169 .\" HREF
2170 \fBpcrepartial\fP
2171 .\"
2172 documentation for details of partial matching.
2173 .sp
2175 .sp
2176 This code is no longer in use. It was formerly returned when the PCRE_PARTIAL
2177 option was used with a compiled pattern containing items that were not
2178 supported for partial matching. From release 8.00 onwards, there are no
2179 restrictions on partial matching.
2180 .sp
2182 .sp
2183 An unexpected internal error has occurred. This error could be caused by a bug
2184 in PCRE or by overwriting of the compiled pattern.
2185 .sp
2187 .sp
2188 This error is given if the value of the \fIovecsize\fP argument is negative.
2189 .sp
2191 .sp
2192 The internal recursion limit, as specified by the \fImatch_limit_recursion\fP
2193 field in a \fBpcre_extra\fP structure (or defaulted) was reached. See the
2194 description above.
2195 .sp
2197 .sp
2198 An invalid combination of PCRE_NEWLINE_\fIxxx\fP options was given.
2199 .sp
2201 .sp
2202 The value of \fIstartoffset\fP was negative or greater than the length of the
2203 subject, that is, the value in \fIlength\fP.
2204 .sp
2206 .sp
2207 This error is returned instead of PCRE_ERROR_BADUTF8 when the subject string
2208 ends with a truncated UTF-8 character and the PCRE_PARTIAL_HARD option is set.
2209 Information about the failure is returned as for PCRE_ERROR_BADUTF8. It is in
2210 fact sufficient to detect this case, but this special error code for
2211 PCRE_PARTIAL_HARD precedes the implementation of returned information; it is
2212 retained for backwards compatibility.
2213 .sp
2215 .sp
2216 This error is returned when \fBpcre_exec()\fP detects a recursion loop within
2217 the pattern. Specifically, it means that either the whole pattern or a
2218 subpattern has been called recursively for the second time at the same position
2219 in the subject string. Some simple patterns that might do this are detected and
2220 faulted at compile time, but more complicated cases, in particular mutual
2221 recursions between two different subpatterns, cannot be detected until run
2222 time.
2223 .sp
2225 .sp
2226 This error is returned when a pattern that was successfully studied using a
2227 JIT compile option is being matched, but the memory available for the
2228 just-in-time processing stack is not large enough. See the
2229 .\" HREF
2230 \fBpcrejit\fP
2231 .\"
2232 documentation for more details.
2233 .sp
2235 .sp
2236 This error is given if a pattern that was compiled by the 8-bit library is
2237 passed to a 16-bit or 32-bit library function, or vice versa.
2238 .sp
2240 .sp
2241 This error is given if a pattern that was compiled and saved is reloaded on a
2242 host with different endianness. The utility function
2243 \fBpcre_pattern_to_host_byte_order()\fP can be used to convert such a pattern
2244 so that it runs on the new host.
2245 .sp
2247 .sp
2248 This error is returned when a pattern that was successfully studied using a JIT
2249 compile option is being matched, but the matching mode (partial or complete
2250 match) does not correspond to any JIT compilation mode. When the JIT fast path
2251 function is used, this error may be also given for invalid options. See the
2252 .\" HREF
2253 \fBpcrejit\fP
2254 .\"
2255 documentation for more details.
2256 .sp
2258 .sp
2259 This error is given if \fBpcre_exec()\fP is called with a negative value for
2260 the \fIlength\fP argument.
2261 .P
2262 Error numbers -16 to -20, -22, and 30 are not used by \fBpcre_exec()\fP.
2263 .
2264 .
2265 .\" HTML <a name="badutf8reasons"></a>
2266 .SS "Reason codes for invalid UTF-8 strings"
2267 .rs
2268 .sp
2269 This section applies only to the 8-bit library. The corresponding information
2270 for the 16-bit and 32-bit libraries is given in the
2271 .\" HREF
2272 \fBpcre16\fP
2273 .\"
2274 and
2275 .\" HREF
2276 \fBpcre32\fP
2277 .\"
2278 pages.
2279 .P
2280 When \fBpcre_exec()\fP returns either PCRE_ERROR_BADUTF8 or
2281 PCRE_ERROR_SHORTUTF8, and the size of the output vector (\fIovecsize\fP) is at
2282 least 2, the offset of the start of the invalid UTF-8 character is placed in
2283 the first output vector element (\fIovector[0]\fP) and a reason code is placed
2284 in the second element (\fIovector[1]\fP). The reason codes are given names in
2285 the \fBpcre.h\fP header file:
2286 .sp
2292 .sp
2293 The string ends with a truncated UTF-8 character; the code specifies how many
2294 bytes are missing (1 to 5). Although RFC 3629 restricts UTF-8 characters to be
2295 no longer than 4 bytes, the encoding scheme (originally defined by RFC 2279)
2296 allows for up to 6 bytes, and this is checked first; hence the possibility of
2297 4 or 5 missing bytes.
2298 .sp
2303 PCRE_UTF8_ERR10
2304 .sp
2305 The two most significant bits of the 2nd, 3rd, 4th, 5th, or 6th byte of the
2306 character do not have the binary value 0b10 (that is, either the most
2307 significant bit is 0, or the next bit is 1).
2308 .sp
2309 PCRE_UTF8_ERR11
2310 PCRE_UTF8_ERR12
2311 .sp
2312 A character that is valid by the RFC 2279 rules is either 5 or 6 bytes long;
2313 these code points are excluded by RFC 3629.
2314 .sp
2315 PCRE_UTF8_ERR13
2316 .sp
2317 A 4-byte character has a value greater than 0x10fff; these code points are
2318 excluded by RFC 3629.
2319 .sp
2320 PCRE_UTF8_ERR14
2321 .sp
2322 A 3-byte character has a value in the range 0xd800 to 0xdfff; this range of
2323 code points are reserved by RFC 3629 for use with UTF-16, and so are excluded
2324 from UTF-8.
2325 .sp
2326 PCRE_UTF8_ERR15
2327 PCRE_UTF8_ERR16
2328 PCRE_UTF8_ERR17
2329 PCRE_UTF8_ERR18
2330 PCRE_UTF8_ERR19
2331 .sp
2332 A 2-, 3-, 4-, 5-, or 6-byte character is "overlong", that is, it codes for a
2333 value that can be represented by fewer bytes, which is invalid. For example,
2334 the two bytes 0xc0, 0xae give the value 0x2e, whose correct coding uses just
2335 one byte.
2336 .sp
2337 PCRE_UTF8_ERR20
2338 .sp
2339 The two most significant bits of the first byte of a character have the binary
2340 value 0b10 (that is, the most significant bit is 1 and the second is 0). Such a
2341 byte can only validly occur as the second or subsequent byte of a multi-byte
2342 character.
2343 .sp
2344 PCRE_UTF8_ERR21
2345 .sp
2346 The first byte of a character has the value 0xfe or 0xff. These values can
2347 never occur in a valid UTF-8 string.
2348 .sp
2350 .sp
2351 Non-character. These are the last two characters in each plane (0xfffe, 0xffff,
2352 0x1fffe, 0x1ffff .. 0x10fffe, 0x10ffff), and the characters 0xfdd0..0xfdef.
2353 .
2354 .
2356 .rs
2357 .sp
2358 .B int pcre_copy_substring(const char *\fIsubject\fP, int *\fIovector\fP,
2359 .ti +5n
2360 .B int \fIstringcount\fP, int \fIstringnumber\fP, char *\fIbuffer\fP,
2361 .ti +5n
2362 .B int \fIbuffersize\fP);
2363 .PP
2364 .B int pcre_get_substring(const char *\fIsubject\fP, int *\fIovector\fP,
2365 .ti +5n
2366 .B int \fIstringcount\fP, int \fIstringnumber\fP,
2367 .ti +5n
2368 .B const char **\fIstringptr\fP);
2369 .PP
2370 .B int pcre_get_substring_list(const char *\fIsubject\fP,
2371 .ti +5n
2372 .B int *\fIovector\fP, int \fIstringcount\fP, "const char ***\fIlistptr\fP);"
2373 .PP
2374 Captured substrings can be accessed directly by using the offsets returned by
2375 \fBpcre_exec()\fP in \fIovector\fP. For convenience, the functions
2376 \fBpcre_copy_substring()\fP, \fBpcre_get_substring()\fP, and
2377 \fBpcre_get_substring_list()\fP are provided for extracting captured substrings
2378 as new, separate, zero-terminated strings. These functions identify substrings
2379 by number. The next section describes functions for extracting named
2380 substrings.
2381 .P
2382 A substring that contains a binary zero is correctly extracted and has a
2383 further zero added on the end, but the result is not, of course, a C string.
2384 However, you can process such a string by referring to the length that is
2385 returned by \fBpcre_copy_substring()\fP and \fBpcre_get_substring()\fP.
2386 Unfortunately, the interface to \fBpcre_get_substring_list()\fP is not adequate
2387 for handling strings containing binary zeros, because the end of the final
2388 string is not independently indicated.
2389 .P
2390 The first three arguments are the same for all three of these functions:
2391 \fIsubject\fP is the subject string that has just been successfully matched,
2392 \fIovector\fP is a pointer to the vector of integer offsets that was passed to
2393 \fBpcre_exec()\fP, and \fIstringcount\fP is the number of substrings that were
2394 captured by the match, including the substring that matched the entire regular
2395 expression. This is the value returned by \fBpcre_exec()\fP if it is greater
2396 than zero. If \fBpcre_exec()\fP returned zero, indicating that it ran out of
2397 space in \fIovector\fP, the value passed as \fIstringcount\fP should be the
2398 number of elements in the vector divided by three.
2399 .P
2400 The functions \fBpcre_copy_substring()\fP and \fBpcre_get_substring()\fP
2401 extract a single substring, whose number is given as \fIstringnumber\fP. A
2402 value of zero extracts the substring that matched the entire pattern, whereas
2403 higher values extract the captured substrings. For \fBpcre_copy_substring()\fP,
2404 the string is placed in \fIbuffer\fP, whose length is given by
2405 \fIbuffersize\fP, while for \fBpcre_get_substring()\fP a new block of memory is
2406 obtained via \fBpcre_malloc\fP, and its address is returned via
2407 \fIstringptr\fP. The yield of the function is the length of the string, not
2408 including the terminating zero, or one of these error codes:
2409 .sp
2411 .sp
2412 The buffer was too small for \fBpcre_copy_substring()\fP, or the attempt to get
2413 memory failed for \fBpcre_get_substring()\fP.
2414 .sp
2416 .sp
2417 There is no substring whose number is \fIstringnumber\fP.
2418 .P
2419 The \fBpcre_get_substring_list()\fP function extracts all available substrings
2420 and builds a list of pointers to them. All this is done in a single block of
2421 memory that is obtained via \fBpcre_malloc\fP. The address of the memory block
2422 is returned via \fIlistptr\fP, which is also the start of the list of string
2423 pointers. The end of the list is marked by a NULL pointer. The yield of the
2424 function is zero if all went well, or the error code
2425 .sp
2427 .sp
2428 if the attempt to get the memory block failed.
2429 .P
2430 When any of these functions encounter a substring that is unset, which can
2431 happen when capturing subpattern number \fIn+1\fP matches some part of the
2432 subject, but subpattern \fIn\fP has not been used at all, they return an empty
2433 string. This can be distinguished from a genuine zero-length substring by
2434 inspecting the appropriate offset in \fIovector\fP, which is negative for unset
2435 substrings.
2436 .P
2437 The two convenience functions \fBpcre_free_substring()\fP and
2438 \fBpcre_free_substring_list()\fP can be used to free the memory returned by
2439 a previous call of \fBpcre_get_substring()\fP or
2440 \fBpcre_get_substring_list()\fP, respectively. They do nothing more than call
2441 the function pointed to by \fBpcre_free\fP, which of course could be called
2442 directly from a C program. However, PCRE is used in some situations where it is
2443 linked via a special interface to another programming language that cannot use
2444 \fBpcre_free\fP directly; it is for these cases that the functions are
2445 provided.
2446 .
2447 .
2449 .rs
2450 .sp
2451 .B int pcre_get_stringnumber(const pcre *\fIcode\fP,
2452 .ti +5n
2453 .B const char *\fIname\fP);
2454 .PP
2455 .B int pcre_copy_named_substring(const pcre *\fIcode\fP,
2456 .ti +5n
2457 .B const char *\fIsubject\fP, int *\fIovector\fP,
2458 .ti +5n
2459 .B int \fIstringcount\fP, const char *\fIstringname\fP,
2460 .ti +5n
2461 .B char *\fIbuffer\fP, int \fIbuffersize\fP);
2462 .PP
2463 .B int pcre_get_named_substring(const pcre *\fIcode\fP,
2464 .ti +5n
2465 .B const char *\fIsubject\fP, int *\fIovector\fP,
2466 .ti +5n
2467 .B int \fIstringcount\fP, const char *\fIstringname\fP,
2468 .ti +5n
2469 .B const char **\fIstringptr\fP);
2470 .PP
2471 To extract a substring by name, you first have to find associated number.
2472 For example, for this pattern
2473 .sp
2474 (a+)b(?<xxx>\ed+)...
2475 .sp
2476 the number of the subpattern called "xxx" is 2. If the name is known to be
2477 unique (PCRE_DUPNAMES was not set), you can find the number from the name by
2478 calling \fBpcre_get_stringnumber()\fP. The first argument is the compiled
2479 pattern, and the second is the name. The yield of the function is the
2480 subpattern number, or PCRE_ERROR_NOSUBSTRING (-7) if there is no subpattern of
2481 that name.
2482 .P
2483 Given the number, you can extract the substring directly, or use one of the
2484 functions described in the previous section. For convenience, there are also
2485 two functions that do the whole job.
2486 .P
2487 Most of the arguments of \fBpcre_copy_named_substring()\fP and
2488 \fBpcre_get_named_substring()\fP are the same as those for the similarly named
2489 functions that extract by number. As these are described in the previous
2490 section, they are not re-described here. There are just two differences:
2491 .P
2492 First, instead of a substring number, a substring name is given. Second, there
2493 is an extra argument, given at the start, which is a pointer to the compiled
2494 pattern. This is needed in order to gain access to the name-to-number
2495 translation table.
2496 .P
2497 These functions call \fBpcre_get_stringnumber()\fP, and if it succeeds, they
2498 then call \fBpcre_copy_substring()\fP or \fBpcre_get_substring()\fP, as
2499 appropriate. \fBNOTE:\fP If PCRE_DUPNAMES is set and there are duplicate names,
2500 the behaviour may not be what you want (see the next section).
2501 .P
2502 \fBWarning:\fP If the pattern uses the (?| feature to set up multiple
2503 subpatterns with the same number, as described in the
2504 .\" HTML <a href="pcrepattern.html#dupsubpatternnumber">
2505 .\" </a>
2506 section on duplicate subpattern numbers
2507 .\"
2508 in the
2509 .\" HREF
2510 \fBpcrepattern\fP
2511 .\"
2512 page, you cannot use names to distinguish the different subpatterns, because
2513 names are not included in the compiled code. The matching process uses only
2514 numbers. For this reason, the use of different names for subpatterns of the
2515 same number causes an error at compile time.
2516 .
2517 .
2519 .rs
2520 .sp
2521 .B int pcre_get_stringtable_entries(const pcre *\fIcode\fP,
2522 .ti +5n
2523 .B const char *\fIname\fP, char **\fIfirst\fP, char **\fIlast\fP);
2524 .PP
2525 When a pattern is compiled with the PCRE_DUPNAMES option, names for subpatterns
2526 are not required to be unique. (Duplicate names are always allowed for
2527 subpatterns with the same number, created by using the (?| feature. Indeed, if
2528 such subpatterns are named, they are required to use the same names.)
2529 .P
2530 Normally, patterns with duplicate names are such that in any one match, only
2531 one of the named subpatterns participates. An example is shown in the
2532 .\" HREF
2533 \fBpcrepattern\fP
2534 .\"
2535 documentation.
2536 .P
2537 When duplicates are present, \fBpcre_copy_named_substring()\fP and
2538 \fBpcre_get_named_substring()\fP return the first substring corresponding to
2539 the given name that is set. If none are set, PCRE_ERROR_NOSUBSTRING (-7) is
2540 returned; no data is returned. The \fBpcre_get_stringnumber()\fP function
2541 returns one of the numbers that are associated with the name, but it is not
2542 defined which it is.
2543 .P
2544 If you want to get full details of all captured substrings for a given name,
2545 you must use the \fBpcre_get_stringtable_entries()\fP function. The first
2546 argument is the compiled pattern, and the second is the name. The third and
2547 fourth are pointers to variables which are updated by the function. After it
2548 has run, they point to the first and last entries in the name-to-number table
2549 for the given name. The function itself returns the length of each entry, or
2550 PCRE_ERROR_NOSUBSTRING (-7) if there are none. The format of the table is
2551 described above in the section entitled \fIInformation about a pattern\fP
2552 .\" HTML <a href="#infoaboutpattern">
2553 .\" </a>
2554 above.
2555 .\"
2556 Given all the relevant entries for the name, you can extract each of their
2557 numbers, and hence the captured data, if any.
2558 .
2559 .
2561 .rs
2562 .sp
2563 The traditional matching function uses a similar algorithm to Perl, which stops
2564 when it finds the first match, starting at a given point in the subject. If you
2565 want to find all possible matches, or the longest possible match, consider
2566 using the alternative matching function (see below) instead. If you cannot use
2567 the alternative function, but still need to find all possible matches, you
2568 can kludge it up by making use of the callout facility, which is described in
2569 the
2570 .\" HREF
2571 \fBpcrecallout\fP
2572 .\"
2573 documentation.
2574 .P
2575 What you have to do is to insert a callout right at the end of the pattern.
2576 When your callout function is called, extract and save the current matched
2577 substring. Then return 1, which forces \fBpcre_exec()\fP to backtrack and try
2578 other alternatives. Ultimately, when it runs out of matches, \fBpcre_exec()\fP
2579 will yield PCRE_ERROR_NOMATCH.
2580 .
2581 .
2583 .rs
2584 .sp
2585 Matching certain patterns using \fBpcre_exec()\fP can use a lot of process
2586 stack, which in certain environments can be rather limited in size. Some users
2587 find it helpful to have an estimate of the amount of stack that is used by
2588 \fBpcre_exec()\fP, to help them set recursion limits, as described in the
2589 .\" HREF
2590 \fBpcrestack\fP
2591 .\"
2592 documentation. The estimate that is output by \fBpcretest\fP when called with
2593 the \fB-m\fP and \fB-C\fP options is obtained by calling \fBpcre_exec\fP with
2594 the values NULL, NULL, NULL, -999, and -999 for its first five arguments.
2595 .P
2596 Normally, if its first argument is NULL, \fBpcre_exec()\fP immediately returns
2597 the negative error code PCRE_ERROR_NULL, but with this special combination of
2598 arguments, it returns instead a negative number whose absolute value is the
2599 approximate stack frame size in bytes. (A negative number is used so that it is
2600 clear that no match has happened.) The value is approximate because in some
2601 cases, recursive calls to \fBpcre_exec()\fP occur when there are one or two
2602 additional variables on the stack.
2603 .P
2604 If PCRE has been compiled to use the heap instead of the stack for recursion,
2605 the value returned is the size of each block that is obtained from the heap.
2606 .
2607 .
2608 .\" HTML <a name="dfamatch"></a>
2610 .rs
2611 .sp
2612 .B int pcre_dfa_exec(const pcre *\fIcode\fP, "const pcre_extra *\fIextra\fP,"
2613 .ti +5n
2614 .B "const char *\fIsubject\fP," int \fIlength\fP, int \fIstartoffset\fP,
2615 .ti +5n
2616 .B int \fIoptions\fP, int *\fIovector\fP, int \fIovecsize\fP,
2617 .ti +5n
2618 .B int *\fIworkspace\fP, int \fIwscount\fP);
2619 .P
2620 The function \fBpcre_dfa_exec()\fP is called to match a subject string against
2621 a compiled pattern, using a matching algorithm that scans the subject string
2622 just once, and does not backtrack. This has different characteristics to the
2623 normal algorithm, and is not compatible with Perl. Some of the features of PCRE
2624 patterns are not supported. Nevertheless, there are times when this kind of
2625 matching can be useful. For a discussion of the two matching algorithms, and a
2626 list of features that \fBpcre_dfa_exec()\fP does not support, see the
2627 .\" HREF
2628 \fBpcrematching\fP
2629 .\"
2630 documentation.
2631 .P
2632 The arguments for the \fBpcre_dfa_exec()\fP function are the same as for
2633 \fBpcre_exec()\fP, plus two extras. The \fIovector\fP argument is used in a
2634 different way, and this is described below. The other common arguments are used
2635 in the same way as for \fBpcre_exec()\fP, so their description is not repeated
2636 here.
2637 .P
2638 The two additional arguments provide workspace for the function. The workspace
2639 vector should contain at least 20 elements. It is used for keeping track of
2640 multiple paths through the pattern tree. More workspace will be needed for
2641 patterns and subjects where there are a lot of potential matches.
2642 .P
2643 Here is an example of a simple call to \fBpcre_dfa_exec()\fP:
2644 .sp
2645 int rc;
2646 int ovector[10];
2647 int wspace[20];
2648 rc = pcre_dfa_exec(
2649 re, /* result of pcre_compile() */
2650 NULL, /* we didn't study the pattern */
2651 "some string", /* the subject string */
2652 11, /* the length of the subject string */
2653 0, /* start at offset 0 in the subject */
2654 0, /* default options */
2655 ovector, /* vector of integers for substring information */
2656 10, /* number of elements (NOT size in bytes) */
2657 wspace, /* working space vector */
2658 20); /* number of elements (NOT size in bytes) */
2659 .
2660 .SS "Option bits for \fBpcre_dfa_exec()\fP"
2661 .rs
2662 .sp
2663 The unused bits of the \fIoptions\fP argument for \fBpcre_dfa_exec()\fP must be
2664 zero. The only bits that may be set are PCRE_ANCHORED, PCRE_NEWLINE_\fIxxx\fP,
2668 All but the last four of these are exactly the same as for \fBpcre_exec()\fP,
2669 so their description is not repeated here.
2670 .sp
2673 .sp
2674 These have the same general effect as they do for \fBpcre_exec()\fP, but the
2675 details are slightly different. When PCRE_PARTIAL_HARD is set for
2676 \fBpcre_dfa_exec()\fP, it returns PCRE_ERROR_PARTIAL if the end of the subject
2677 is reached and there is still at least one matching possibility that requires
2678 additional characters. This happens even if some complete matches have also
2679 been found. When PCRE_PARTIAL_SOFT is set, the return code PCRE_ERROR_NOMATCH
2680 is converted into PCRE_ERROR_PARTIAL if the end of the subject is reached,
2681 there have been no complete matches, but there is still at least one matching
2682 possibility. The portion of the string that was inspected when the longest
2683 partial match was found is set as the first matching string in both cases.
2684 There is a more detailed discussion of partial and multi-segment matching, with
2685 examples, in the
2686 .\" HREF
2687 \fBpcrepartial\fP
2688 .\"
2689 documentation.
2690 .sp
2692 .sp
2693 Setting the PCRE_DFA_SHORTEST option causes the matching algorithm to stop as
2694 soon as it has found one match. Because of the way the alternative algorithm
2695 works, this is necessarily the shortest possible match at the first possible
2696 matching point in the subject string.
2697 .sp
2699 .sp
2700 When \fBpcre_dfa_exec()\fP returns a partial match, it is possible to call it
2701 again, with additional subject characters, and have it continue with the same
2702 match. The PCRE_DFA_RESTART option requests this action; when it is set, the
2703 \fIworkspace\fP and \fIwscount\fP options must reference the same vector as
2704 before because data about the match so far is left in them after a partial
2705 match. There is more discussion of this facility in the
2706 .\" HREF
2707 \fBpcrepartial\fP
2708 .\"
2709 documentation.
2710 .
2711 .
2712 .SS "Successful returns from \fBpcre_dfa_exec()\fP"
2713 .rs
2714 .sp
2715 When \fBpcre_dfa_exec()\fP succeeds, it may have matched more than one
2716 substring in the subject. Note, however, that all the matches from one run of
2717 the function start at the same point in the subject. The shorter matches are
2718 all initial substrings of the longer matches. For example, if the pattern
2719 .sp
2720 <.*>
2721 .sp
2722 is matched against the string
2723 .sp
2724 This is <something> <something else> <something further> no more
2725 .sp
2726 the three matched strings are
2727 .sp
2728 <something>
2729 <something> <something else>
2730 <something> <something else> <something further>
2731 .sp
2732 On success, the yield of the function is a number greater than zero, which is
2733 the number of matched substrings. The substrings themselves are returned in
2734 \fIovector\fP. Each string uses two elements; the first is the offset to the
2735 start, and the second is the offset to the end. In fact, all the strings have
2736 the same start offset. (Space could have been saved by giving this only once,
2737 but it was decided to retain some compatibility with the way \fBpcre_exec()\fP
2738 returns data, even though the meaning of the strings is different.)
2739 .P
2740 The strings are returned in reverse order of length; that is, the longest
2741 matching string is given first. If there were too many matches to fit into
2742 \fIovector\fP, the yield of the function is zero, and the vector is filled with
2743 the longest matches. Unlike \fBpcre_exec()\fP, \fBpcre_dfa_exec()\fP can use
2744 the entire \fIovector\fP for returning matched strings.
2745 .
2746 .
2747 .SS "Error returns from \fBpcre_dfa_exec()\fP"
2748 .rs
2749 .sp
2750 The \fBpcre_dfa_exec()\fP function returns a negative number when it fails.
2751 Many of the errors are the same as for \fBpcre_exec()\fP, and these are
2752 described
2753 .\" HTML <a href="#errorlist">
2754 .\" </a>
2755 above.
2756 .\"
2757 There are in addition the following errors that are specific to
2758 \fBpcre_dfa_exec()\fP:
2759 .sp
2761 .sp
2762 This return is given if \fBpcre_dfa_exec()\fP encounters an item in the pattern
2763 that it does not support, for instance, the use of \eC or a back reference.
2764 .sp
2766 .sp
2767 This return is given if \fBpcre_dfa_exec()\fP encounters a condition item that
2768 uses a back reference for the condition, or a test for recursion in a specific
2769 group. These are not supported.
2770 .sp
2772 .sp
2773 This return is given if \fBpcre_dfa_exec()\fP is called with an \fIextra\fP
2774 block that contains a setting of the \fImatch_limit\fP or
2775 \fImatch_limit_recursion\fP fields. This is not supported (these fields are
2776 meaningless for DFA matching).
2777 .sp
2779 .sp
2780 This return is given if \fBpcre_dfa_exec()\fP runs out of space in the
2781 \fIworkspace\fP vector.
2782 .sp
2784 .sp
2785 When a recursive subpattern is processed, the matching function calls itself
2786 recursively, using private vectors for \fIovector\fP and \fIworkspace\fP. This
2787 error is given if the output vector is not large enough. This should be
2788 extremely rare, as a vector of size 1000 is used.
2789 .sp
2791 .sp
2792 When \fBpcre_dfa_exec()\fP is called with the \fBPCRE_DFA_RESTART\fP option,
2793 some plausibility checks are made on the contents of the workspace, which
2794 should contain data about the previous partial match. If any of these checks
2795 fail, this error is given.
2796 .
2797 .
2798 .SH "SEE ALSO"
2799 .rs
2800 .sp
2801 \fBpcre16\fP(3), \fBpcre32\fP(3), \fBpcrebuild\fP(3), \fBpcrecallout\fP(3),
2802 \fBpcrecpp(3)\fP(3), \fBpcrematching\fP(3), \fBpcrepartial\fP(3),
2803 \fBpcreposix\fP(3), \fBpcreprecompile\fP(3), \fBpcresample\fP(3),
2804 \fBpcrestack\fP(3).
2805 .
2806 .
2808 .rs
2809 .sp
2810 .nf
2811 Philip Hazel
2812 University Computing Service
2813 Cambridge CB2 3QH, England.
2814 .fi
2815 .
2816 .
2818 .rs
2819 .sp
2820 .nf
2821 Last updated: 08 November 2012
2822 Copyright (c) 1997-2012 University of Cambridge.
2823 .fi


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