1PCRE2API(3) Library Functions Manual PCRE2API(3)
2
6 PCRE2 - Perl-compatible regular expressions (revised API)
7 #include <pcre2.h>
9 PCRE2 is a new API for PCRE, starting at release 10.0. This document
11 contains a description of all its native functions. See the pcre2 docu‐
12 ment for an overview of all the PCRE2 documentation.
13
15 pcre2_code *pcre2_compile(PCRE2_SPTR pattern, PCRE2_SIZE length,
17 uint32_t options, int *errorcode, PCRE2_SIZE *erroroffset,
18 pcre2_compile_context *ccontext);
19 void pcre2_code_free(pcre2_code *code);
21 pcre2_match_data *pcre2_match_data_create(uint32_t ovecsize,
23 pcre2_general_context *gcontext);
24 pcre2_match_data *pcre2_match_data_create_from_pattern(
26 const pcre2_code *code, pcre2_general_context *gcontext);
27 int pcre2_match(const pcre2_code *code, PCRE2_SPTR subject,
29 PCRE2_SIZE length, PCRE2_SIZE startoffset,
30 uint32_t options, pcre2_match_data *match_data,
31 pcre2_match_context *mcontext);
32 int pcre2_dfa_match(const pcre2_code *code, PCRE2_SPTR subject,
34 PCRE2_SIZE length, PCRE2_SIZE startoffset,
35 uint32_t options, pcre2_match_data *match_data,
36 pcre2_match_context *mcontext,
37 int *workspace, PCRE2_SIZE wscount);
38 void pcre2_match_data_free(pcre2_match_data *match_data);
40
42 PCRE2_SPTR pcre2_get_mark(pcre2_match_data *match_data);
44 uint32_t pcre2_get_ovector_count(pcre2_match_data *match_data);
46 PCRE2_SIZE *pcre2_get_ovector_pointer(pcre2_match_data *match_data);
48 PCRE2_SIZE pcre2_get_startchar(pcre2_match_data *match_data);
50
52 pcre2_general_context *pcre2_general_context_create(
54 void *(*private_malloc)(PCRE2_SIZE, void *),
55 void (*private_free)(void *, void *), void *memory_data);
56 pcre2_general_context *pcre2_general_context_copy(
58 pcre2_general_context *gcontext);
59 void pcre2_general_context_free(pcre2_general_context *gcontext);
61
63 pcre2_compile_context *pcre2_compile_context_create(
65 pcre2_general_context *gcontext);
66 pcre2_compile_context *pcre2_compile_context_copy(
68 pcre2_compile_context *ccontext);
69 void pcre2_compile_context_free(pcre2_compile_context *ccontext);
71 int pcre2_set_bsr(pcre2_compile_context *ccontext,
73 uint32_t value);
74 int pcre2_set_character_tables(pcre2_compile_context *ccontext,
76 const uint8_t *tables);
77 int pcre2_set_compile_extra_options(pcre2_compile_context *ccontext,
79 uint32_t extra_options);
80 int pcre2_set_max_pattern_length(pcre2_compile_context *ccontext,
82 PCRE2_SIZE value);
83 int pcre2_set_newline(pcre2_compile_context *ccontext,
85 uint32_t value);
86 int pcre2_set_parens_nest_limit(pcre2_compile_context *ccontext,
88 uint32_t value);
89 int pcre2_set_compile_recursion_guard(pcre2_compile_context *ccontext,
91 int (*guard_function)(uint32_t, void *), void *user_data);
92
94 pcre2_match_context *pcre2_match_context_create(
96 pcre2_general_context *gcontext);
97 pcre2_match_context *pcre2_match_context_copy(
99 pcre2_match_context *mcontext);
100 void pcre2_match_context_free(pcre2_match_context *mcontext);
102 int pcre2_set_callout(pcre2_match_context *mcontext,
104 int (*callout_function)(pcre2_callout_block *, void *),
105 void *callout_data);
106 int pcre2_set_substitute_callout(pcre2_match_context *mcontext,
108 int (*callout_function)(pcre2_substitute_callout_block *, void *),
109 void *callout_data);
110 int pcre2_set_offset_limit(pcre2_match_context *mcontext,
112 PCRE2_SIZE value);
113 int pcre2_set_heap_limit(pcre2_match_context *mcontext,
115 uint32_t value);
116 int pcre2_set_match_limit(pcre2_match_context *mcontext,
118 uint32_t value);
119 int pcre2_set_depth_limit(pcre2_match_context *mcontext,
121 uint32_t value);
122
124 int pcre2_substring_copy_byname(pcre2_match_data *match_data,
126 PCRE2_SPTR name, PCRE2_UCHAR *buffer, PCRE2_SIZE *bufflen);
127 int pcre2_substring_copy_bynumber(pcre2_match_data *match_data,
129 uint32_t number, PCRE2_UCHAR *buffer,
130 PCRE2_SIZE *bufflen);
131 void pcre2_substring_free(PCRE2_UCHAR *buffer);
133 int pcre2_substring_get_byname(pcre2_match_data *match_data,
135 PCRE2_SPTR name, PCRE2_UCHAR **bufferptr, PCRE2_SIZE *bufflen);
136 int pcre2_substring_get_bynumber(pcre2_match_data *match_data,
138 uint32_t number, PCRE2_UCHAR **bufferptr,
139 PCRE2_SIZE *bufflen);
140 int pcre2_substring_length_byname(pcre2_match_data *match_data,
142 PCRE2_SPTR name, PCRE2_SIZE *length);
143 int pcre2_substring_length_bynumber(pcre2_match_data *match_data,
145 uint32_t number, PCRE2_SIZE *length);
146 int pcre2_substring_nametable_scan(const pcre2_code *code,
148 PCRE2_SPTR name, PCRE2_SPTR *first, PCRE2_SPTR *last);
149 int pcre2_substring_number_from_name(const pcre2_code *code,
151 PCRE2_SPTR name);
152 void pcre2_substring_list_free(PCRE2_SPTR *list);
154 int pcre2_substring_list_get(pcre2_match_data *match_data,
156 PCRE2_UCHAR ***listptr, PCRE2_SIZE **lengthsptr);
157
159 int pcre2_substitute(const pcre2_code *code, PCRE2_SPTR subject,
161 PCRE2_SIZE length, PCRE2_SIZE startoffset,
162 uint32_t options, pcre2_match_data *match_data,
163 pcre2_match_context *mcontext, PCRE2_SPTR replacementz,
164 PCRE2_SIZE rlength, PCRE2_UCHAR *outputbuffer,
165 PCRE2_SIZE *outlengthptr);
166
168 int pcre2_jit_compile(pcre2_code *code, uint32_t options);
170 int pcre2_jit_match(const pcre2_code *code, PCRE2_SPTR subject,
172 PCRE2_SIZE length, PCRE2_SIZE startoffset,
173 uint32_t options, pcre2_match_data *match_data,
174 pcre2_match_context *mcontext);
175 void pcre2_jit_free_unused_memory(pcre2_general_context *gcontext);
177 pcre2_jit_stack *pcre2_jit_stack_create(PCRE2_SIZE startsize,
179 PCRE2_SIZE maxsize, pcre2_general_context *gcontext);
180 void pcre2_jit_stack_assign(pcre2_match_context *mcontext,
182 pcre2_jit_callback callback_function, void *callback_data);
183 void pcre2_jit_stack_free(pcre2_jit_stack *jit_stack);
185
187 int32_t pcre2_serialize_decode(pcre2_code **codes,
189 int32_t number_of_codes, const uint8_t *bytes,
190 pcre2_general_context *gcontext);
191 int32_t pcre2_serialize_encode(const pcre2_code **codes,
193 int32_t number_of_codes, uint8_t **serialized_bytes,
194 PCRE2_SIZE *serialized_size, pcre2_general_context *gcontext);
195 void pcre2_serialize_free(uint8_t *bytes);
197 int32_t pcre2_serialize_get_number_of_codes(const uint8_t *bytes);
199
201 pcre2_code *pcre2_code_copy(const pcre2_code *code);
203 pcre2_code *pcre2_code_copy_with_tables(const pcre2_code *code);
205 int pcre2_get_error_message(int errorcode, PCRE2_UCHAR *buffer,
207 PCRE2_SIZE bufflen);
208 const uint8_t *pcre2_maketables(pcre2_general_context *gcontext);
210 void pcre2_maketables_free(pcre2_general_context *gcontext,
212 const uint8_t *tables);
213 int pcre2_pattern_info(const pcre2_code *code, uint32_t what,
215 void *where);
216 int pcre2_callout_enumerate(const pcre2_code *code,
218 int (*callback)(pcre2_callout_enumerate_block *, void *),
219 void *user_data);
220 int pcre2_config(uint32_t what, void *where);
222
224 int pcre2_set_recursion_limit(pcre2_match_context *mcontext,
226 uint32_t value);
227 int pcre2_set_recursion_memory_management(
229 pcre2_match_context *mcontext,
230 void *(*private_malloc)(PCRE2_SIZE, void *),
231 void (*private_free)(void *, void *), void *memory_data);
232 These functions became obsolete at release 10.30 and are retained only
234 for backward compatibility. They should not be used in new code. The
235 first is replaced by pcre2_set_depth_limit(); the second is no longer
236 needed and has no effect (it always returns zero).
237
239 pcre2_convert_context *pcre2_convert_context_create(
241 pcre2_general_context *gcontext);
242 pcre2_convert_context *pcre2_convert_context_copy(
244 pcre2_convert_context *cvcontext);
245 void pcre2_convert_context_free(pcre2_convert_context *cvcontext);
247 int pcre2_set_glob_escape(pcre2_convert_context *cvcontext,
249 uint32_t escape_char);
250 int pcre2_set_glob_separator(pcre2_convert_context *cvcontext,
252 uint32_t separator_char);
253 int pcre2_pattern_convert(PCRE2_SPTR pattern, PCRE2_SIZE length,
255 uint32_t options, PCRE2_UCHAR **buffer,
256 PCRE2_SIZE *blength, pcre2_convert_context *cvcontext);
257 void pcre2_converted_pattern_free(PCRE2_UCHAR *converted_pattern);
259 These functions provide a way of converting non-PCRE2 patterns into
261 patterns that can be processed by pcre2_compile(). This facility is ex‐
262 perimental and may be changed in future releases. At present, "globs"
263 and POSIX basic and extended patterns can be converted. Details are
264 given in the pcre2convert documentation.
265
267 There are three PCRE2 libraries, supporting 8-bit, 16-bit, and 32-bit
269 code units, respectively. However, there is just one header file,
270 pcre2.h. This contains the function prototypes and other definitions
271 for all three libraries. One, two, or all three can be installed simul‐
272 taneously. On Unix-like systems the libraries are called libpcre2-8,
273 libpcre2-16, and libpcre2-32, and they can also co-exist with the orig‐
274 inal PCRE libraries.
275 Character strings are passed to and from a PCRE2 library as a sequence
277 of unsigned integers in code units of the appropriate width. Every
278 PCRE2 function comes in three different forms, one for each library,
279 for example:
280 pcre2_compile_8()
282 pcre2_compile_16()
283 pcre2_compile_32()
284 There are also three different sets of data types:
286 PCRE2_UCHAR8, PCRE2_UCHAR16, PCRE2_UCHAR32
288 PCRE2_SPTR8, PCRE2_SPTR16, PCRE2_SPTR32
289 The UCHAR types define unsigned code units of the appropriate widths.
291 For example, PCRE2_UCHAR16 is usually defined as `uint16_t'. The SPTR
292 types are constant pointers to the equivalent UCHAR types, that is,
293 they are pointers to vectors of unsigned code units.
294 Many applications use only one code unit width. For their convenience,
296 macros are defined whose names are the generic forms such as pcre2_com‐
297 pile() and PCRE2_SPTR. These macros use the value of the macro
298 PCRE2_CODE_UNIT_WIDTH to generate the appropriate width-specific func‐
299 tion and macro names. PCRE2_CODE_UNIT_WIDTH is not defined by default.
300 An application must define it to be 8, 16, or 32 before including
301 pcre2.h in order to make use of the generic names.
302 Applications that use more than one code unit width can be linked with
304 more than one PCRE2 library, but must define PCRE2_CODE_UNIT_WIDTH to
305 be 0 before including pcre2.h, and then use the real function names.
306 Any code that is to be included in an environment where the value of
307 PCRE2_CODE_UNIT_WIDTH is unknown should also use the real function
308 names. (Unfortunately, it is not possible in C code to save and restore
309 the value of a macro.)
310 If PCRE2_CODE_UNIT_WIDTH is not defined before including pcre2.h, a
312 compiler error occurs.
313 When using multiple libraries in an application, you must take care
315 when processing any particular pattern to use only functions from a
316 single library. For example, if you want to run a match using a pat‐
317 tern that was compiled with pcre2_compile_16(), you must do so with
318 pcre2_match_16(), not pcre2_match_8() or pcre2_match_32().
319 In the function summaries above, and in the rest of this document and
321 other PCRE2 documents, functions and data types are described using
322 their generic names, without the _8, _16, or _32 suffix.
323
325 PCRE2 has its own native API, which is described in this document.
327 There are also some wrapper functions for the 8-bit library that corre‐
328 spond to the POSIX regular expression API, but they do not give access
329 to all the functionality of PCRE2. They are described in the pcre2posix
330 documentation. Both these APIs define a set of C function calls.
331 The native API C data types, function prototypes, option values, and
333 error codes are defined in the header file pcre2.h, which also contains
334 definitions of PCRE2_MAJOR and PCRE2_MINOR, the major and minor release
335 numbers for the library. Applications can use these to include support
336 for different releases of PCRE2.
337 In a Windows environment, if you want to statically link an application
339 program against a non-dll PCRE2 library, you must define PCRE2_STATIC
340 before including pcre2.h.
341 The functions pcre2_compile() and pcre2_match() are used for compiling
343 and matching regular expressions in a Perl-compatible manner. A sample
344 program that demonstrates the simplest way of using them is provided in
345 the file called pcre2demo.c in the PCRE2 source distribution. A listing
346 of this program is given in the pcre2demo documentation, and the
347 pcre2sample documentation describes how to compile and run it.
348 The compiling and matching functions recognize various options that are
350 passed as bits in an options argument. There are also some more compli‐
351 cated parameters such as custom memory management functions and re‐
352 source limits that are passed in "contexts" (which are just memory
353 blocks, described below). Simple applications do not need to make use
354 of contexts.
355 Just-in-time (JIT) compiler support is an optional feature of PCRE2
357 that can be built in appropriate hardware environments. It greatly
358 speeds up the matching performance of many patterns. Programs can re‐
359 quest that it be used if available by calling pcre2_jit_compile() after
360 a pattern has been successfully compiled by pcre2_compile(). This does
361 nothing if JIT support is not available.
362 More complicated programs might need to make use of the specialist
364 functions pcre2_jit_stack_create(), pcre2_jit_stack_free(), and
365 pcre2_jit_stack_assign() in order to control the JIT code's memory us‐
366 age.
367 JIT matching is automatically used by pcre2_match() if it is available,
369 unless the PCRE2_NO_JIT option is set. There is also a direct interface
370 for JIT matching, which gives improved performance at the expense of
371 less sanity checking. The JIT-specific functions are discussed in the
372 pcre2jit documentation.
373 A second matching function, pcre2_dfa_match(), which is not Perl-com‐
375 patible, is also provided. This uses a different algorithm for the
376 matching. The alternative algorithm finds all possible matches (at a
377 given point in the subject), and scans the subject just once (unless
378 there are lookaround assertions). However, this algorithm does not re‐
379 turn captured substrings. A description of the two matching algorithms
380 and their advantages and disadvantages is given in the pcre2matching
381 documentation. There is no JIT support for pcre2_dfa_match().
382 In addition to the main compiling and matching functions, there are
384 convenience functions for extracting captured substrings from a subject
385 string that has been matched by pcre2_match(). They are:
386 pcre2_substring_copy_byname()
388 pcre2_substring_copy_bynumber()
389 pcre2_substring_get_byname()
390 pcre2_substring_get_bynumber()
391 pcre2_substring_list_get()
392 pcre2_substring_length_byname()
393 pcre2_substring_length_bynumber()
394 pcre2_substring_nametable_scan()
395 pcre2_substring_number_from_name()
396 pcre2_substring_free() and pcre2_substring_list_free() are also pro‐
398 vided, to free memory used for extracted strings. If either of these
399 functions is called with a NULL argument, the function returns immedi‐
400 ately without doing anything.
401 The function pcre2_substitute() can be called to match a pattern and
403 return a copy of the subject string with substitutions for parts that
404 were matched.
405 Functions whose names begin with pcre2_serialize_ are used for saving
407 compiled patterns on disc or elsewhere, and reloading them later.
408 Finally, there are functions for finding out information about a com‐
410 piled pattern (pcre2_pattern_info()) and about the configuration with
411 which PCRE2 was built (pcre2_config()).
412 Functions with names ending with _free() are used for freeing memory
414 blocks of various sorts. In all cases, if one of these functions is
415 called with a NULL argument, it does nothing.
416
418 The PCRE2 API uses string lengths and offsets into strings of code
420 units in several places. These values are always of type PCRE2_SIZE,
421 which is an unsigned integer type, currently always defined as size_t.
422 The largest value that can be stored in such a type (that is
423 ~(PCRE2_SIZE)0) is reserved as a special indicator for zero-terminated
424 strings and unset offsets. Therefore, the longest string that can be
425 handled is one less than this maximum.
426
428 PCRE2 supports five different conventions for indicating line breaks in
430 strings: a single CR (carriage return) character, a single LF (line‐
431 feed) character, the two-character sequence CRLF, any of the three pre‐
432 ceding, or any Unicode newline sequence. The Unicode newline sequences
433 are the three just mentioned, plus the single characters VT (vertical
434 tab, U+000B), FF (form feed, U+000C), NEL (next line, U+0085), LS (line
435 separator, U+2028), and PS (paragraph separator, U+2029).
436 Each of the first three conventions is used by at least one operating
438 system as its standard newline sequence. When PCRE2 is built, a default
439 can be specified. If it is not, the default is set to LF, which is the
440 Unix standard. However, the newline convention can be changed by an ap‐
441 plication when calling pcre2_compile(), or it can be specified by spe‐
442 cial text at the start of the pattern itself; this overrides any other
443 settings. See the pcre2pattern page for details of the special charac‐
444 ter sequences.
445 In the PCRE2 documentation the word "newline" is used to mean "the
447 character or pair of characters that indicate a line break". The choice
448 of newline convention affects the handling of the dot, circumflex, and
449 dollar metacharacters, the handling of #-comments in /x mode, and, when
450 CRLF is a recognized line ending sequence, the match position advance‐
451 ment for a non-anchored pattern. There is more detail about this in the
452 section on pcre2_match() options below.
453 The choice of newline convention does not affect the interpretation of
455 the \n or \r escape sequences, nor does it affect what \R matches; this
456 has its own separate convention.
457
459 In a multithreaded application it is important to keep thread-specific
461 data separate from data that can be shared between threads. The PCRE2
462 library code itself is thread-safe: it contains no static or global
463 variables. The API is designed to be fairly simple for non-threaded ap‐
464 plications while at the same time ensuring that multithreaded applica‐
465 tions can use it.
466 There are several different blocks of data that are used to pass infor‐
468 mation between the application and the PCRE2 libraries.
469 The compiled pattern
471 A pointer to the compiled form of a pattern is returned to the user
473 when pcre2_compile() is successful. The data in the compiled pattern is
474 fixed, and does not change when the pattern is matched. Therefore, it
475 is thread-safe, that is, the same compiled pattern can be used by more
476 than one thread simultaneously. For example, an application can compile
477 all its patterns at the start, before forking off multiple threads that
478 use them. However, if the just-in-time (JIT) optimization feature is
479 being used, it needs separate memory stack areas for each thread. See
480 the pcre2jit documentation for more details.
481 In a more complicated situation, where patterns are compiled only when
483 they are first needed, but are still shared between threads, pointers
484 to compiled patterns must be protected from simultaneous writing by
485 multiple threads. This is somewhat tricky to do correctly. If you know
486 that writing to a pointer is atomic in your environment, you can use
487 logic like this:
488 Get a read-only (shared) lock (mutex) for pointer
490 if (pointer == NULL)
491 {
492 Get a write (unique) lock for pointer
493 if (pointer == NULL) pointer = pcre2_compile(...
494 }
495 Release the lock
496 Use pointer in pcre2_match()
497 Of course, testing for compilation errors should also be included in
499 the code.
500 The reason for checking the pointer a second time is as follows: Sev‐
502 eral threads may have acquired the shared lock and tested the pointer
503 for being NULL, but only one of them will be given the write lock, with
504 the rest kept waiting. The winning thread will compile the pattern and
505 store the result. After this thread releases the write lock, another
506 thread will get it, and if it does not retest pointer for being NULL,
507 will recompile the pattern and overwrite the pointer, creating a memory
508 leak and possibly causing other issues.
509 In an environment where writing to a pointer may not be atomic, the
511 above logic is not sufficient. The thread that is doing the compiling
512 may be descheduled after writing only part of the pointer, which could
513 cause other threads to use an invalid value. Instead of checking the
514 pointer itself, a separate "pointer is valid" flag (that can be updated
515 atomically) must be used:
516 Get a read-only (shared) lock (mutex) for pointer
518 if (!pointer_is_valid)
519 {
520 Get a write (unique) lock for pointer
521 if (!pointer_is_valid)
522 {
523 pointer = pcre2_compile(...
524 pointer_is_valid = TRUE
525 }
526 }
527 Release the lock
528 Use pointer in pcre2_match()
529 If JIT is being used, but the JIT compilation is not being done immedi‐
531 ately (perhaps waiting to see if the pattern is used often enough),
532 similar logic is required. JIT compilation updates a value within the
533 compiled code block, so a thread must gain unique write access to the
534 pointer before calling pcre2_jit_compile(). Alternatively,
535 pcre2_code_copy() or pcre2_code_copy_with_tables() can be used to ob‐
536 tain a private copy of the compiled code before calling the JIT com‐
537 piler.
538 Context blocks
540 The next main section below introduces the idea of "contexts" in which
542 PCRE2 functions are called. A context is nothing more than a collection
543 of parameters that control the way PCRE2 operates. Grouping a number of
544 parameters together in a context is a convenient way of passing them to
545 a PCRE2 function without using lots of arguments. The parameters that
546 are stored in contexts are in some sense "advanced features" of the
547 API. Many straightforward applications will not need to use contexts.
548 In a multithreaded application, if the parameters in a context are val‐
550 ues that are never changed, the same context can be used by all the
551 threads. However, if any thread needs to change any value in a context,
552 it must make its own thread-specific copy.
553 Match blocks
555 The matching functions need a block of memory for storing the results
557 of a match. This includes details of what was matched, as well as addi‐
558 tional information such as the name of a (*MARK) setting. Each thread
559 must provide its own copy of this memory.
560
562 Some PCRE2 functions have a lot of parameters, many of which are used
564 only by specialist applications, for example, those that use custom
565 memory management or non-standard character tables. To keep function
566 argument lists at a reasonable size, and at the same time to keep the
567 API extensible, "uncommon" parameters are passed to certain functions
568 in a context instead of directly. A context is just a block of memory
569 that holds the parameter values. Applications that do not need to ad‐
570 just any of the context parameters can pass NULL when a context pointer
571 is required.
572 There are three different types of context: a general context that is
574 relevant for several PCRE2 operations, a compile-time context, and a
575 match-time context.
576 The general context
578 At present, this context just contains pointers to (and data for) ex‐
580 ternal memory management functions that are called from several places
581 in the PCRE2 library. The context is named `general' rather than
582 specifically `memory' because in future other fields may be added. If
583 you do not want to supply your own custom memory management functions,
584 you do not need to bother with a general context. A general context is
585 created by:
586 pcre2_general_context *pcre2_general_context_create(
588 void *(*private_malloc)(PCRE2_SIZE, void *),
589 void (*private_free)(void *, void *), void *memory_data);
590 The two function pointers specify custom memory management functions,
592 whose prototypes are:
593 void *private_malloc(PCRE2_SIZE, void *);
595 void private_free(void *, void *);
596 Whenever code in PCRE2 calls these functions, the final argument is the
598 value of memory_data. Either of the first two arguments of the creation
599 function may be NULL, in which case the system memory management func‐
600 tions malloc() and free() are used. (This is not currently useful, as
601 there are no other fields in a general context, but in future there
602 might be.) The private_malloc() function is used (if supplied) to ob‐
603 tain memory for storing the context, and all three values are saved as
604 part of the context.
605 Whenever PCRE2 creates a data block of any kind, the block contains a
607 pointer to the free() function that matches the malloc() function that
608 was used. When the time comes to free the block, this function is
609 called.
610 A general context can be copied by calling:
612 pcre2_general_context *pcre2_general_context_copy(
614 pcre2_general_context *gcontext);
615 The memory used for a general context should be freed by calling:
617 void pcre2_general_context_free(pcre2_general_context *gcontext);
619 If this function is passed a NULL argument, it returns immediately
621 without doing anything.
622 The compile context
624 A compile context is required if you want to provide an external func‐
626 tion for stack checking during compilation or to change the default
627 values of any of the following compile-time parameters:
628 What \R matches (Unicode newlines or CR, LF, CRLF only)
630 PCRE2's character tables
631 The newline character sequence
632 The compile time nested parentheses limit
633 The maximum length of the pattern string
634 The extra options bits (none set by default)
635 A compile context is also required if you are using custom memory man‐
637 agement. If none of these apply, just pass NULL as the context argu‐
638 ment of pcre2_compile().
639 A compile context is created, copied, and freed by the following func‐
641 tions:
642 pcre2_compile_context *pcre2_compile_context_create(
644 pcre2_general_context *gcontext);
645 pcre2_compile_context *pcre2_compile_context_copy(
647 pcre2_compile_context *ccontext);
648 void pcre2_compile_context_free(pcre2_compile_context *ccontext);
650 A compile context is created with default values for its parameters.
652 These can be changed by calling the following functions, which return 0
653 on success, or PCRE2_ERROR_BADDATA if invalid data is detected.
654 int pcre2_set_bsr(pcre2_compile_context *ccontext,
656 uint32_t value);
657 The value must be PCRE2_BSR_ANYCRLF, to specify that \R matches only
659 CR, LF, or CRLF, or PCRE2_BSR_UNICODE, to specify that \R matches any
660 Unicode line ending sequence. The value is used by the JIT compiler and
661 by the two interpreted matching functions, pcre2_match() and
662 pcre2_dfa_match().
663 int pcre2_set_character_tables(pcre2_compile_context *ccontext,
665 const uint8_t *tables);
666 The value must be the result of a call to pcre2_maketables(), whose
668 only argument is a general context. This function builds a set of char‐
669 acter tables in the current locale.
670 int pcre2_set_compile_extra_options(pcre2_compile_context *ccontext,
672 uint32_t extra_options);
673 As PCRE2 has developed, almost all the 32 option bits that are avail‐
675 able in the options argument of pcre2_compile() have been used up. To
676 avoid running out, the compile context contains a set of extra option
677 bits which are used for some newer, assumed rarer, options. This func‐
678 tion sets those bits. It always sets all the bits (either on or off).
679 It does not modify any existing setting. The available options are de‐
680 fined in the section entitled "Extra compile options" below.
681 int pcre2_set_max_pattern_length(pcre2_compile_context *ccontext,
683 PCRE2_SIZE value);
684 This sets a maximum length, in code units, for any pattern string that
686 is compiled with this context. If the pattern is longer, an error is
687 generated. This facility is provided so that applications that accept
688 patterns from external sources can limit their size. The default is the
689 largest number that a PCRE2_SIZE variable can hold, which is effec‐
690 tively unlimited.
691 int pcre2_set_newline(pcre2_compile_context *ccontext,
693 uint32_t value);
694 This specifies which characters or character sequences are to be recog‐
696 nized as newlines. The value must be one of PCRE2_NEWLINE_CR (carriage
697 return only), PCRE2_NEWLINE_LF (linefeed only), PCRE2_NEWLINE_CRLF (the
698 two-character sequence CR followed by LF), PCRE2_NEWLINE_ANYCRLF (any
699 of the above), PCRE2_NEWLINE_ANY (any Unicode newline sequence), or
700 PCRE2_NEWLINE_NUL (the NUL character, that is a binary zero).
701 A pattern can override the value set in the compile context by starting
703 with a sequence such as (*CRLF). See the pcre2pattern page for details.
704 When a pattern is compiled with the PCRE2_EXTENDED or PCRE2_EX‐
706 TENDED_MORE option, the newline convention affects the recognition of
707 the end of internal comments starting with #. The value is saved with
708 the compiled pattern for subsequent use by the JIT compiler and by the
709 two interpreted matching functions, pcre2_match() and
710 pcre2_dfa_match().
711 int pcre2_set_parens_nest_limit(pcre2_compile_context *ccontext,
713 uint32_t value);
714 This parameter adjusts the limit, set when PCRE2 is built (default
716 250), on the depth of parenthesis nesting in a pattern. This limit
717 stops rogue patterns using up too much system stack when being com‐
718 piled. The limit applies to parentheses of all kinds, not just captur‐
719 ing parentheses.
720 int pcre2_set_compile_recursion_guard(pcre2_compile_context *ccontext,
722 int (*guard_function)(uint32_t, void *), void *user_data);
723 There is at least one application that runs PCRE2 in threads with very
725 limited system stack, where running out of stack is to be avoided at
726 all costs. The parenthesis limit above cannot take account of how much
727 stack is actually available during compilation. For a finer control,
728 you can supply a function that is called whenever pcre2_compile()
729 starts to compile a parenthesized part of a pattern. This function can
730 check the actual stack size (or anything else that it wants to, of
731 course).
732 The first argument to the callout function gives the current depth of
734 nesting, and the second is user data that is set up by the last argu‐
735 ment of pcre2_set_compile_recursion_guard(). The callout function
736 should return zero if all is well, or non-zero to force an error.
737 The match context
739 A match context is required if you want to:
741 Set up a callout function
743 Set an offset limit for matching an unanchored pattern
744 Change the limit on the amount of heap used when matching
745 Change the backtracking match limit
746 Change the backtracking depth limit
747 Set custom memory management specifically for the match
748 If none of these apply, just pass NULL as the context argument of
750 pcre2_match(), pcre2_dfa_match(), or pcre2_jit_match().
751 A match context is created, copied, and freed by the following func‐
753 tions:
754 pcre2_match_context *pcre2_match_context_create(
756 pcre2_general_context *gcontext);
757 pcre2_match_context *pcre2_match_context_copy(
759 pcre2_match_context *mcontext);
760 void pcre2_match_context_free(pcre2_match_context *mcontext);
762 A match context is created with default values for its parameters.
764 These can be changed by calling the following functions, which return 0
765 on success, or PCRE2_ERROR_BADDATA if invalid data is detected.
766 int pcre2_set_callout(pcre2_match_context *mcontext,
768 int (*callout_function)(pcre2_callout_block *, void *),
769 void *callout_data);
770 This sets up a callout function for PCRE2 to call at specified points
772 during a matching operation. Details are given in the pcre2callout doc‐
773 umentation.
774 int pcre2_set_substitute_callout(pcre2_match_context *mcontext,
776 int (*callout_function)(pcre2_substitute_callout_block *, void *),
777 void *callout_data);
778 This sets up a callout function for PCRE2 to call after each substitu‐
780 tion made by pcre2_substitute(). Details are given in the section enti‐
781 tled "Creating a new string with substitutions" below.
782 int pcre2_set_offset_limit(pcre2_match_context *mcontext,
784 PCRE2_SIZE value);
785 The offset_limit parameter limits how far an unanchored search can ad‐
787 vance in the subject string. The default value is PCRE2_UNSET. The
788 pcre2_match() and pcre2_dfa_match() functions return PCRE2_ERROR_NO‐
789 MATCH if a match with a starting point before or at the given offset is
790 not found. The pcre2_substitute() function makes no more substitutions.
791 For example, if the pattern /abc/ is matched against "123abc" with an
793 offset limit less than 3, the result is PCRE2_ERROR_NOMATCH. A match
794 can never be found if the startoffset argument of pcre2_match(),
795 pcre2_dfa_match(), or pcre2_substitute() is greater than the offset
796 limit set in the match context.
797 When using this facility, you must set the PCRE2_USE_OFFSET_LIMIT op‐
799 tion when calling pcre2_compile() so that when JIT is in use, different
800 code can be compiled. If a match is started with a non-default match
801 limit when PCRE2_USE_OFFSET_LIMIT is not set, an error is generated.
802 The offset limit facility can be used to track progress when searching
804 large subject strings or to limit the extent of global substitutions.
805 See also the PCRE2_FIRSTLINE option, which requires a match to start
806 before or at the first newline that follows the start of matching in
807 the subject. If this is set with an offset limit, a match must occur in
808 the first line and also within the offset limit. In other words, which‐
809 ever limit comes first is used.
810 int pcre2_set_heap_limit(pcre2_match_context *mcontext,
812 uint32_t value);
813 The heap_limit parameter specifies, in units of kibibytes (1024 bytes),
815 the maximum amount of heap memory that pcre2_match() may use to hold
816 backtracking information when running an interpretive match. This limit
817 also applies to pcre2_dfa_match(), which may use the heap when process‐
818 ing patterns with a lot of nested pattern recursion or lookarounds or
819 atomic groups. This limit does not apply to matching with the JIT opti‐
820 mization, which has its own memory control arrangements (see the
821 pcre2jit documentation for more details). If the limit is reached, the
822 negative error code PCRE2_ERROR_HEAPLIMIT is returned. The default
823 limit can be set when PCRE2 is built; if it is not, the default is set
824 very large and is essentially "unlimited".
825 A value for the heap limit may also be supplied by an item at the start
827 of a pattern of the form
828 (*LIMIT_HEAP=ddd)
830 where ddd is a decimal number. However, such a setting is ignored un‐
832 less ddd is less than the limit set by the caller of pcre2_match() or,
833 if no such limit is set, less than the default.
834 The pcre2_match() function starts out using a 20KiB vector on the sys‐
836 tem stack for recording backtracking points. The more nested backtrack‐
837 ing points there are (that is, the deeper the search tree), the more
838 memory is needed. Heap memory is used only if the initial vector is
839 too small. If the heap limit is set to a value less than 21 (in partic‐
840 ular, zero) no heap memory will be used. In this case, only patterns
841 that do not have a lot of nested backtracking can be successfully pro‐
842 cessed.
843 Similarly, for pcre2_dfa_match(), a vector on the system stack is used
845 when processing pattern recursions, lookarounds, or atomic groups, and
846 only if this is not big enough is heap memory used. In this case, too,
847 setting a value of zero disables the use of the heap.
848 int pcre2_set_match_limit(pcre2_match_context *mcontext,
850 uint32_t value);
851 The match_limit parameter provides a means of preventing PCRE2 from us‐
853 ing up too many computing resources when processing patterns that are
854 not going to match, but which have a very large number of possibilities
855 in their search trees. The classic example is a pattern that uses
856 nested unlimited repeats.
857 There is an internal counter in pcre2_match() that is incremented each
859 time round its main matching loop. If this value reaches the match
860 limit, pcre2_match() returns the negative value PCRE2_ERROR_MATCHLIMIT.
861 This has the effect of limiting the amount of backtracking that can
862 take place. For patterns that are not anchored, the count restarts from
863 zero for each position in the subject string. This limit also applies
864 to pcre2_dfa_match(), though the counting is done in a different way.
865 When pcre2_match() is called with a pattern that was successfully pro‐
867 cessed by pcre2_jit_compile(), the way in which matching is executed is
868 entirely different. However, there is still the possibility of runaway
869 matching that goes on for a very long time, and so the match_limit
870 value is also used in this case (but in a different way) to limit how
871 long the matching can continue.
872 The default value for the limit can be set when PCRE2 is built; the de‐
874 fault default is 10 million, which handles all but the most extreme
875 cases. A value for the match limit may also be supplied by an item at
876 the start of a pattern of the form
877 (*LIMIT_MATCH=ddd)
879 where ddd is a decimal number. However, such a setting is ignored un‐
881 less ddd is less than the limit set by the caller of pcre2_match() or
882 pcre2_dfa_match() or, if no such limit is set, less than the default.
883 int pcre2_set_depth_limit(pcre2_match_context *mcontext,
885 uint32_t value);
886 This parameter limits the depth of nested backtracking in
888 pcre2_match(). Each time a nested backtracking point is passed, a new
889 memory "frame" is used to remember the state of matching at that point.
890 Thus, this parameter indirectly limits the amount of memory that is
891 used in a match. However, because the size of each memory "frame" de‐
892 pends on the number of capturing parentheses, the actual memory limit
893 varies from pattern to pattern. This limit was more useful in versions
894 before 10.30, where function recursion was used for backtracking.
895 The depth limit is not relevant, and is ignored, when matching is done
897 using JIT compiled code. However, it is supported by pcre2_dfa_match(),
898 which uses it to limit the depth of nested internal recursive function
899 calls that implement atomic groups, lookaround assertions, and pattern
900 recursions. This limits, indirectly, the amount of system stack that is
901 used. It was more useful in versions before 10.32, when stack memory
902 was used for local workspace vectors for recursive function calls. From
903 version 10.32, only local variables are allocated on the stack and as
904 each call uses only a few hundred bytes, even a small stack can support
905 quite a lot of recursion.
906 If the depth of internal recursive function calls is great enough, lo‐
908 cal workspace vectors are allocated on the heap from version 10.32 on‐
909 wards, so the depth limit also indirectly limits the amount of heap
910 memory that is used. A recursive pattern such as /(.(?2))((?1)|)/, when
911 matched to a very long string using pcre2_dfa_match(), can use a great
912 deal of memory. However, it is probably better to limit heap usage di‐
913 rectly by calling pcre2_set_heap_limit().
914 The default value for the depth limit can be set when PCRE2 is built;
916 if it is not, the default is set to the same value as the default for
917 the match limit. If the limit is exceeded, pcre2_match() or
918 pcre2_dfa_match() returns PCRE2_ERROR_DEPTHLIMIT. A value for the depth
919 limit may also be supplied by an item at the start of a pattern of the
920 form
921 (*LIMIT_DEPTH=ddd)
923 where ddd is a decimal number. However, such a setting is ignored un‐
925 less ddd is less than the limit set by the caller of pcre2_match() or
926 pcre2_dfa_match() or, if no such limit is set, less than the default.
927
929 int pcre2_config(uint32_t what, void *where);
931 The function pcre2_config() makes it possible for a PCRE2 client to
933 find the value of certain configuration parameters and to discover
934 which optional features have been compiled into the PCRE2 library. The
935 pcre2build documentation has more details about these features.
936 The first argument for pcre2_config() specifies which information is
938 required. The second argument is a pointer to memory into which the in‐
939 formation is placed. If NULL is passed, the function returns the amount
940 of memory that is needed for the requested information. For calls that
941 return numerical values, the value is in bytes; when requesting these
942 values, where should point to appropriately aligned memory. For calls
943 that return strings, the required length is given in code units, not
944 counting the terminating zero.
945 When requesting information, the returned value from pcre2_config() is
947 non-negative on success, or the negative error code PCRE2_ERROR_BADOP‐
948 TION if the value in the first argument is not recognized. The follow‐
949 ing information is available:
950 PCRE2_CONFIG_BSR
952 The output is a uint32_t integer whose value indicates what character
954 sequences the \R escape sequence matches by default. A value of
955 PCRE2_BSR_UNICODE means that \R matches any Unicode line ending se‐
956 quence; a value of PCRE2_BSR_ANYCRLF means that \R matches only CR, LF,
957 or CRLF. The default can be overridden when a pattern is compiled.
958 PCRE2_CONFIG_COMPILED_WIDTHS
960 The output is a uint32_t integer whose lower bits indicate which code
962 unit widths were selected when PCRE2 was built. The 1-bit indicates
963 8-bit support, and the 2-bit and 4-bit indicate 16-bit and 32-bit sup‐
964 port, respectively.
965 PCRE2_CONFIG_DEPTHLIMIT
967 The output is a uint32_t integer that gives the default limit for the
969 depth of nested backtracking in pcre2_match() or the depth of nested
970 recursions, lookarounds, and atomic groups in pcre2_dfa_match(). Fur‐
971 ther details are given with pcre2_set_depth_limit() above.
972 PCRE2_CONFIG_HEAPLIMIT
974 The output is a uint32_t integer that gives, in kibibytes, the default
976 limit for the amount of heap memory used by pcre2_match() or
977 pcre2_dfa_match(). Further details are given with
978 pcre2_set_heap_limit() above.
979 PCRE2_CONFIG_JIT
981 The output is a uint32_t integer that is set to one if support for
983 just-in-time compiling is available; otherwise it is set to zero.
984 PCRE2_CONFIG_JITTARGET
986 The where argument should point to a buffer that is at least 48 code
988 units long. (The exact length required can be found by calling
989 pcre2_config() with where set to NULL.) The buffer is filled with a
990 string that contains the name of the architecture for which the JIT
991 compiler is configured, for example "x86 32bit (little endian + un‐
992 aligned)". If JIT support is not available, PCRE2_ERROR_BADOPTION is
993 returned, otherwise the number of code units used is returned. This is
994 the length of the string, plus one unit for the terminating zero.
995 PCRE2_CONFIG_LINKSIZE
997 The output is a uint32_t integer that contains the number of bytes used
999 for internal linkage in compiled regular expressions. When PCRE2 is
1000 configured, the value can be set to 2, 3, or 4, with the default being
1001 2. This is the value that is returned by pcre2_config(). However, when
1002 the 16-bit library is compiled, a value of 3 is rounded up to 4, and
1003 when the 32-bit library is compiled, internal linkages always use 4
1004 bytes, so the configured value is not relevant.
1005 The default value of 2 for the 8-bit and 16-bit libraries is sufficient
1007 for all but the most massive patterns, since it allows the size of the
1008 compiled pattern to be up to 65535 code units. Larger values allow
1009 larger regular expressions to be compiled by those two libraries, but
1010 at the expense of slower matching.
1011 PCRE2_CONFIG_MATCHLIMIT
1013 The output is a uint32_t integer that gives the default match limit for
1015 pcre2_match(). Further details are given with pcre2_set_match_limit()
1016 above.
1017 PCRE2_CONFIG_NEWLINE
1019 The output is a uint32_t integer whose value specifies the default
1021 character sequence that is recognized as meaning "newline". The values
1022 are:
1023 PCRE2_NEWLINE_CR Carriage return (CR)
1025 PCRE2_NEWLINE_LF Linefeed (LF)
1026 PCRE2_NEWLINE_CRLF Carriage return, linefeed (CRLF)
1027 PCRE2_NEWLINE_ANY Any Unicode line ending
1028 PCRE2_NEWLINE_ANYCRLF Any of CR, LF, or CRLF
1029 PCRE2_NEWLINE_NUL The NUL character (binary zero)
1030 The default should normally correspond to the standard sequence for
1032 your operating system.
1033 PCRE2_CONFIG_NEVER_BACKSLASH_C
1035 The output is a uint32_t integer that is set to one if the use of \C
1037 was permanently disabled when PCRE2 was built; otherwise it is set to
1038 zero.
1039 PCRE2_CONFIG_PARENSLIMIT
1041 The output is a uint32_t integer that gives the maximum depth of nest‐
1043 ing of parentheses (of any kind) in a pattern. This limit is imposed to
1044 cap the amount of system stack used when a pattern is compiled. It is
1045 specified when PCRE2 is built; the default is 250. This limit does not
1046 take into account the stack that may already be used by the calling ap‐
1047 plication. For finer control over compilation stack usage, see
1048 pcre2_set_compile_recursion_guard().
1049 PCRE2_CONFIG_STACKRECURSE
1051 This parameter is obsolete and should not be used in new code. The out‐
1053 put is a uint32_t integer that is always set to zero.
1054 PCRE2_CONFIG_TABLES_LENGTH
1056 The output is a uint32_t integer that gives the length of PCRE2's char‐
1058 acter processing tables in bytes. For details of these tables see the
1059 section on locale support below.
1060 PCRE2_CONFIG_UNICODE_VERSION
1062 The where argument should point to a buffer that is at least 24 code
1064 units long. (The exact length required can be found by calling
1065 pcre2_config() with where set to NULL.) If PCRE2 has been compiled
1066 without Unicode support, the buffer is filled with the text "Unicode
1067 not supported". Otherwise, the Unicode version string (for example,
1068 "8.0.0") is inserted. The number of code units used is returned. This
1069 is the length of the string plus one unit for the terminating zero.
1070 PCRE2_CONFIG_UNICODE
1072 The output is a uint32_t integer that is set to one if Unicode support
1074 is available; otherwise it is set to zero. Unicode support implies UTF
1075 support.
1076 PCRE2_CONFIG_VERSION
1078 The where argument should point to a buffer that is at least 24 code
1080 units long. (The exact length required can be found by calling
1081 pcre2_config() with where set to NULL.) The buffer is filled with the
1082 PCRE2 version string, zero-terminated. The number of code units used is
1083 returned. This is the length of the string plus one unit for the termi‐
1084 nating zero.
1085
1087 pcre2_code *pcre2_compile(PCRE2_SPTR pattern, PCRE2_SIZE length,
1089 uint32_t options, int *errorcode, PCRE2_SIZE *erroroffset,
1090 pcre2_compile_context *ccontext);
1091 void pcre2_code_free(pcre2_code *code);
1093 pcre2_code *pcre2_code_copy(const pcre2_code *code);
1095 pcre2_code *pcre2_code_copy_with_tables(const pcre2_code *code);
1097 The pcre2_compile() function compiles a pattern into an internal form.
1099 The pattern is defined by a pointer to a string of code units and a
1100 length (in code units). If the pattern is zero-terminated, the length
1101 can be specified as PCRE2_ZERO_TERMINATED. The function returns a
1102 pointer to a block of memory that contains the compiled pattern and re‐
1103 lated data, or NULL if an error occurred.
1104 If the compile context argument ccontext is NULL, memory for the com‐
1106 piled pattern is obtained by calling malloc(). Otherwise, it is ob‐
1107 tained from the same memory function that was used for the compile con‐
1108 text. The caller must free the memory by calling pcre2_code_free() when
1109 it is no longer needed. If pcre2_code_free() is called with a NULL ar‐
1110 gument, it returns immediately, without doing anything.
1111 The function pcre2_code_copy() makes a copy of the compiled code in new
1113 memory, using the same memory allocator as was used for the original.
1114 However, if the code has been processed by the JIT compiler (see be‐
1115 low), the JIT information cannot be copied (because it is position-de‐
1116 pendent). The new copy can initially be used only for non-JIT match‐
1117 ing, though it can be passed to pcre2_jit_compile() if required. If
1118 pcre2_code_copy() is called with a NULL argument, it returns NULL.
1119 The pcre2_code_copy() function provides a way for individual threads in
1121 a multithreaded application to acquire a private copy of shared com‐
1122 piled code. However, it does not make a copy of the character tables
1123 used by the compiled pattern; the new pattern code points to the same
1124 tables as the original code. (See "Locale Support" below for details
1125 of these character tables.) In many applications the same tables are
1126 used throughout, so this behaviour is appropriate. Nevertheless, there
1127 are occasions when a copy of a compiled pattern and the relevant tables
1128 are needed. The pcre2_code_copy_with_tables() provides this facility.
1129 Copies of both the code and the tables are made, with the new code
1130 pointing to the new tables. The memory for the new tables is automati‐
1131 cally freed when pcre2_code_free() is called for the new copy of the
1132 compiled code. If pcre2_code_copy_with_tables() is called with a NULL
1133 argument, it returns NULL.
1134 NOTE: When one of the matching functions is called, pointers to the
1136 compiled pattern and the subject string are set in the match data block
1137 so that they can be referenced by the substring extraction functions
1138 after a successful match. After running a match, you must not free a
1139 compiled pattern or a subject string until after all operations on the
1140 match data block have taken place, unless, in the case of the subject
1141 string, you have used the PCRE2_COPY_MATCHED_SUBJECT option, which is
1142 described in the section entitled "Option bits for pcre2_match()" be‐
1143 low.
1144 The options argument for pcre2_compile() contains various bit settings
1146 that affect the compilation. It should be zero if none of them are re‐
1147 quired. The available options are described below. Some of them (in
1148 particular, those that are compatible with Perl, but some others as
1149 well) can also be set and unset from within the pattern (see the de‐
1150 tailed description in the pcre2pattern documentation).
1151 For those options that can be different in different parts of the pat‐
1153 tern, the contents of the options argument specifies their settings at
1154 the start of compilation. The PCRE2_ANCHORED, PCRE2_ENDANCHORED, and
1155 PCRE2_NO_UTF_CHECK options can be set at the time of matching as well
1156 as at compile time.
1157 Some additional options and less frequently required compile-time pa‐
1159 rameters (for example, the newline setting) can be provided in a com‐
1160 pile context (as described above).
1161 If errorcode or erroroffset is NULL, pcre2_compile() returns NULL imme‐
1163 diately. Otherwise, the variables to which these point are set to an
1164 error code and an offset (number of code units) within the pattern, re‐
1165 spectively, when pcre2_compile() returns NULL because a compilation er‐
1166 ror has occurred. The values are not defined when compilation is suc‐
1167 cessful and pcre2_compile() returns a non-NULL value.
1168 There are nearly 100 positive error codes that pcre2_compile() may re‐
1170 turn if it finds an error in the pattern. There are also some negative
1171 error codes that are used for invalid UTF strings when validity check‐
1172 ing is in force. These are the same as given by pcre2_match() and
1173 pcre2_dfa_match(), and are described in the pcre2unicode documentation.
1174 There is no separate documentation for the positive error codes, be‐
1175 cause the textual error messages that are obtained by calling the
1176 pcre2_get_error_message() function (see "Obtaining a textual error mes‐
1177 sage" below) should be self-explanatory. Macro names starting with
1178 PCRE2_ERROR_ are defined for both positive and negative error codes in
1179 pcre2.h.
1180 The value returned in erroroffset is an indication of where in the pat‐
1182 tern the error occurred. It is not necessarily the furthest point in
1183 the pattern that was read. For example, after the error "lookbehind as‐
1184 sertion is not fixed length", the error offset points to the start of
1185 the failing assertion. For an invalid UTF-8 or UTF-16 string, the off‐
1186 set is that of the first code unit of the failing character.
1187 Some errors are not detected until the whole pattern has been scanned;
1189 in these cases, the offset passed back is the length of the pattern.
1190 Note that the offset is in code units, not characters, even in a UTF
1191 mode. It may sometimes point into the middle of a UTF-8 or UTF-16 char‐
1192 acter.
1193 This code fragment shows a typical straightforward call to pcre2_com‐
1195 pile():
1196 pcre2_code *re;
1198 PCRE2_SIZE erroffset;
1199 int errorcode;
1200 re = pcre2_compile(
1201 "^A.*Z", /* the pattern */
1202 PCRE2_ZERO_TERMINATED, /* the pattern is zero-terminated */
1203 0, /* default options */
1204 &errorcode, /* for error code */
1205 &erroffset, /* for error offset */
1206 NULL); /* no compile context */
1207 Main compile options
1210 The following names for option bits are defined in the pcre2.h header
1212 file:
1213 PCRE2_ANCHORED
1215 If this bit is set, the pattern is forced to be "anchored", that is, it
1217 is constrained to match only at the first matching point in the string
1218 that is being searched (the "subject string"). This effect can also be
1219 achieved by appropriate constructs in the pattern itself, which is the
1220 only way to do it in Perl.
1221 PCRE2_ALLOW_EMPTY_CLASS
1223 By default, for compatibility with Perl, a closing square bracket that
1225 immediately follows an opening one is treated as a data character for
1226 the class. When PCRE2_ALLOW_EMPTY_CLASS is set, it terminates the
1227 class, which therefore contains no characters and so can never match.
1228 PCRE2_ALT_BSUX
1230 This option request alternative handling of three escape sequences,
1232 which makes PCRE2's behaviour more like ECMAscript (aka JavaScript).
1233 When it is set:
1234 (1) \U matches an upper case "U" character; by default \U causes a com‐
1236 pile time error (Perl uses \U to upper case subsequent characters).
1237 (2) \u matches a lower case "u" character unless it is followed by four
1239 hexadecimal digits, in which case the hexadecimal number defines the
1240 code point to match. By default, \u causes a compile time error (Perl
1241 uses it to upper case the following character).
1242 (3) \x matches a lower case "x" character unless it is followed by two
1244 hexadecimal digits, in which case the hexadecimal number defines the
1245 code point to match. By default, as in Perl, a hexadecimal number is
1246 always expected after \x, but it may have zero, one, or two digits (so,
1247 for example, \xz matches a binary zero character followed by z).
1248 ECMAscript 6 added additional functionality to \u. This can be accessed
1250 using the PCRE2_EXTRA_ALT_BSUX extra option (see "Extra compile op‐
1251 tions" below). Note that this alternative escape handling applies only
1252 to patterns. Neither of these options affects the processing of re‐
1253 placement strings passed to pcre2_substitute().
1254 PCRE2_ALT_CIRCUMFLEX
1256 In multiline mode (when PCRE2_MULTILINE is set), the circumflex
1258 metacharacter matches at the start of the subject (unless PCRE2_NOTBOL
1259 is set), and also after any internal newline. However, it does not
1260 match after a newline at the end of the subject, for compatibility with
1261 Perl. If you want a multiline circumflex also to match after a termi‐
1262 nating newline, you must set PCRE2_ALT_CIRCUMFLEX.
1263 PCRE2_ALT_VERBNAMES
1265 By default, for compatibility with Perl, the name in any verb sequence
1267 such as (*MARK:NAME) is any sequence of characters that does not in‐
1268 clude a closing parenthesis. The name is not processed in any way, and
1269 it is not possible to include a closing parenthesis in the name. How‐
1270 ever, if the PCRE2_ALT_VERBNAMES option is set, normal backslash pro‐
1271 cessing is applied to verb names and only an unescaped closing paren‐
1272 thesis terminates the name. A closing parenthesis can be included in a
1273 name either as \) or between \Q and \E. If the PCRE2_EXTENDED or
1274 PCRE2_EXTENDED_MORE option is set with PCRE2_ALT_VERBNAMES, unescaped
1275 whitespace in verb names is skipped and #-comments are recognized, ex‐
1276 actly as in the rest of the pattern.
1277 PCRE2_AUTO_CALLOUT
1279 If this bit is set, pcre2_compile() automatically inserts callout
1281 items, all with number 255, before each pattern item, except immedi‐
1282 ately before or after an explicit callout in the pattern. For discus‐
1283 sion of the callout facility, see the pcre2callout documentation.
1284 PCRE2_CASELESS
1286 If this bit is set, letters in the pattern match both upper and lower
1288 case letters in the subject. It is equivalent to Perl's /i option, and
1289 it can be changed within a pattern by a (?i) option setting. If either
1290 PCRE2_UTF or PCRE2_UCP is set, Unicode properties are used for all
1291 characters with more than one other case, and for all characters whose
1292 code points are greater than U+007F. Note that there are two ASCII
1293 characters, K and S, that, in addition to their lower case ASCII equiv‐
1294 alents, are case-equivalent with U+212A (Kelvin sign) and U+017F (long
1295 S) respectively. For lower valued characters with only one other case,
1296 a lookup table is used for speed. When neither PCRE2_UTF nor PCRE2_UCP
1297 is set, a lookup table is used for all code points less than 256, and
1298 higher code points (available only in 16-bit or 32-bit mode) are
1299 treated as not having another case.
1300 PCRE2_DOLLAR_ENDONLY
1302 If this bit is set, a dollar metacharacter in the pattern matches only
1304 at the end of the subject string. Without this option, a dollar also
1305 matches immediately before a newline at the end of the string (but not
1306 before any other newlines). The PCRE2_DOLLAR_ENDONLY option is ignored
1307 if PCRE2_MULTILINE is set. There is no equivalent to this option in
1308 Perl, and no way to set it within a pattern.
1309 PCRE2_DOTALL
1311 If this bit is set, a dot metacharacter in the pattern matches any
1313 character, including one that indicates a newline. However, it only
1314 ever matches one character, even if newlines are coded as CRLF. Without
1315 this option, a dot does not match when the current position in the sub‐
1316 ject is at a newline. This option is equivalent to Perl's /s option,
1317 and it can be changed within a pattern by a (?s) option setting. A neg‐
1318 ative class such as [^a] always matches newline characters, and the \N
1319 escape sequence always matches a non-newline character, independent of
1320 the setting of PCRE2_DOTALL.
1321 PCRE2_DUPNAMES
1323 If this bit is set, names used to identify capture groups need not be
1325 unique. This can be helpful for certain types of pattern when it is
1326 known that only one instance of the named group can ever be matched.
1327 There are more details of named capture groups below; see also the
1328 pcre2pattern documentation.
1329 PCRE2_ENDANCHORED
1331 If this bit is set, the end of any pattern match must be right at the
1333 end of the string being searched (the "subject string"). If the pattern
1334 match succeeds by reaching (*ACCEPT), but does not reach the end of the
1335 subject, the match fails at the current starting point. For unanchored
1336 patterns, a new match is then tried at the next starting point. How‐
1337 ever, if the match succeeds by reaching the end of the pattern, but not
1338 the end of the subject, backtracking occurs and an alternative match
1339 may be found. Consider these two patterns:
1340 .(*ACCEPT)|..
1342 .|..
1343 If matched against "abc" with PCRE2_ENDANCHORED set, the first matches
1345 "c" whereas the second matches "bc". The effect of PCRE2_ENDANCHORED
1346 can also be achieved by appropriate constructs in the pattern itself,
1347 which is the only way to do it in Perl.
1348 For DFA matching with pcre2_dfa_match(), PCRE2_ENDANCHORED applies only
1350 to the first (that is, the longest) matched string. Other parallel
1351 matches, which are necessarily substrings of the first one, must obvi‐
1352 ously end before the end of the subject.
1353 PCRE2_EXTENDED
1355 If this bit is set, most white space characters in the pattern are to‐
1357 tally ignored except when escaped or inside a character class. However,
1358 white space is not allowed within sequences such as (?> that introduce
1359 various parenthesized groups, nor within numerical quantifiers such as
1360 {1,3}. Ignorable white space is permitted between an item and a follow‐
1361 ing quantifier and between a quantifier and a following + that indi‐
1362 cates possessiveness. PCRE2_EXTENDED is equivalent to Perl's /x option,
1363 and it can be changed within a pattern by a (?x) option setting.
1364 When PCRE2 is compiled without Unicode support, PCRE2_EXTENDED recog‐
1366 nizes as white space only those characters with code points less than
1367 256 that are flagged as white space in its low-character table. The ta‐
1368 ble is normally created by pcre2_maketables(), which uses the isspace()
1369 function to identify space characters. In most ASCII environments, the
1370 relevant characters are those with code points 0x0009 (tab), 0x000A
1371 (linefeed), 0x000B (vertical tab), 0x000C (formfeed), 0x000D (carriage
1372 return), and 0x0020 (space).
1373 When PCRE2 is compiled with Unicode support, in addition to these char‐
1375 acters, five more Unicode "Pattern White Space" characters are recog‐
1376 nized by PCRE2_EXTENDED. These are U+0085 (next line), U+200E (left-to-
1377 right mark), U+200F (right-to-left mark), U+2028 (line separator), and
1378 U+2029 (paragraph separator). This set of characters is the same as
1379 recognized by Perl's /x option. Note that the horizontal and vertical
1380 space characters that are matched by the \h and \v escapes in patterns
1381 are a much bigger set.
1382 As well as ignoring most white space, PCRE2_EXTENDED also causes char‐
1384 acters between an unescaped # outside a character class and the next
1385 newline, inclusive, to be ignored, which makes it possible to include
1386 comments inside complicated patterns. Note that the end of this type of
1387 comment is a literal newline sequence in the pattern; escape sequences
1388 that happen to represent a newline do not count.
1389 Which characters are interpreted as newlines can be specified by a set‐
1391 ting in the compile context that is passed to pcre2_compile() or by a
1392 special sequence at the start of the pattern, as described in the sec‐
1393 tion entitled "Newline conventions" in the pcre2pattern documentation.
1394 A default is defined when PCRE2 is built.
1395 PCRE2_EXTENDED_MORE
1397 This option has the effect of PCRE2_EXTENDED, but, in addition, un‐
1399 escaped space and horizontal tab characters are ignored inside a char‐
1400 acter class. Note: only these two characters are ignored, not the full
1401 set of pattern white space characters that are ignored outside a char‐
1402 acter class. PCRE2_EXTENDED_MORE is equivalent to Perl's /xx option,
1403 and it can be changed within a pattern by a (?xx) option setting.
1404 PCRE2_FIRSTLINE
1406 If this option is set, the start of an unanchored pattern match must be
1408 before or at the first newline in the subject string following the
1409 start of matching, though the matched text may continue over the new‐
1410 line. If startoffset is non-zero, the limiting newline is not necessar‐
1411 ily the first newline in the subject. For example, if the subject
1412 string is "abc\nxyz" (where \n represents a single-character newline) a
1413 pattern match for "yz" succeeds with PCRE2_FIRSTLINE if startoffset is
1414 greater than 3. See also PCRE2_USE_OFFSET_LIMIT, which provides a more
1415 general limiting facility. If PCRE2_FIRSTLINE is set with an offset
1416 limit, a match must occur in the first line and also within the offset
1417 limit. In other words, whichever limit comes first is used.
1418 PCRE2_LITERAL
1420 If this option is set, all meta-characters in the pattern are disabled,
1422 and it is treated as a literal string. Matching literal strings with a
1423 regular expression engine is not the most efficient way of doing it. If
1424 you are doing a lot of literal matching and are worried about effi‐
1425 ciency, you should consider using other approaches. The only other main
1426 options that are allowed with PCRE2_LITERAL are: PCRE2_ANCHORED,
1427 PCRE2_ENDANCHORED, PCRE2_AUTO_CALLOUT, PCRE2_CASELESS, PCRE2_FIRSTLINE,
1428 PCRE2_MATCH_INVALID_UTF, PCRE2_NO_START_OPTIMIZE, PCRE2_NO_UTF_CHECK,
1429 PCRE2_UTF, and PCRE2_USE_OFFSET_LIMIT. The extra options PCRE2_EX‐
1430 TRA_MATCH_LINE and PCRE2_EXTRA_MATCH_WORD are also supported. Any other
1431 options cause an error.
1432 PCRE2_MATCH_INVALID_UTF
1434 This option forces PCRE2_UTF (see below) and also enables support for
1436 matching by pcre2_match() in subject strings that contain invalid UTF
1437 sequences. This facility is not supported for DFA matching. For de‐
1438 tails, see the pcre2unicode documentation.
1439 PCRE2_MATCH_UNSET_BACKREF
1441 If this option is set, a backreference to an unset capture group
1443 matches an empty string (by default this causes the current matching
1444 alternative to fail). A pattern such as (\1)(a) succeeds when this op‐
1445 tion is set (assuming it can find an "a" in the subject), whereas it
1446 fails by default, for Perl compatibility. Setting this option makes
1447 PCRE2 behave more like ECMAscript (aka JavaScript).
1448 PCRE2_MULTILINE
1450 By default, for the purposes of matching "start of line" and "end of
1452 line", PCRE2 treats the subject string as consisting of a single line
1453 of characters, even if it actually contains newlines. The "start of
1454 line" metacharacter (^) matches only at the start of the string, and
1455 the "end of line" metacharacter ($) matches only at the end of the
1456 string, or before a terminating newline (except when PCRE2_DOLLAR_EN‐
1457 DONLY is set). Note, however, that unless PCRE2_DOTALL is set, the "any
1458 character" metacharacter (.) does not match at a newline. This behav‐
1459 iour (for ^, $, and dot) is the same as Perl.
1460 When PCRE2_MULTILINE it is set, the "start of line" and "end of line"
1462 constructs match immediately following or immediately before internal
1463 newlines in the subject string, respectively, as well as at the very
1464 start and end. This is equivalent to Perl's /m option, and it can be
1465 changed within a pattern by a (?m) option setting. Note that the "start
1466 of line" metacharacter does not match after a newline at the end of the
1467 subject, for compatibility with Perl. However, you can change this by
1468 setting the PCRE2_ALT_CIRCUMFLEX option. If there are no newlines in a
1469 subject string, or no occurrences of ^ or $ in a pattern, setting
1470 PCRE2_MULTILINE has no effect.
1471 PCRE2_NEVER_BACKSLASH_C
1473 This option locks out the use of \C in the pattern that is being com‐
1475 piled. This escape can cause unpredictable behaviour in UTF-8 or
1476 UTF-16 modes, because it may leave the current matching point in the
1477 middle of a multi-code-unit character. This option may be useful in ap‐
1478 plications that process patterns from external sources. Note that there
1479 is also a build-time option that permanently locks out the use of \C.
1480 PCRE2_NEVER_UCP
1482 This option locks out the use of Unicode properties for handling \B,
1484 \b, \D, \d, \S, \s, \W, \w, and some of the POSIX character classes, as
1485 described for the PCRE2_UCP option below. In particular, it prevents
1486 the creator of the pattern from enabling this facility by starting the
1487 pattern with (*UCP). This option may be useful in applications that
1488 process patterns from external sources. The option combination PCRE_UCP
1489 and PCRE_NEVER_UCP causes an error.
1490 PCRE2_NEVER_UTF
1492 This option locks out interpretation of the pattern as UTF-8, UTF-16,
1494 or UTF-32, depending on which library is in use. In particular, it pre‐
1495 vents the creator of the pattern from switching to UTF interpretation
1496 by starting the pattern with (*UTF). This option may be useful in ap‐
1497 plications that process patterns from external sources. The combination
1498 of PCRE2_UTF and PCRE2_NEVER_UTF causes an error.
1499 PCRE2_NO_AUTO_CAPTURE
1501 If this option is set, it disables the use of numbered capturing paren‐
1503 theses in the pattern. Any opening parenthesis that is not followed by
1504 ? behaves as if it were followed by ?: but named parentheses can still
1505 be used for capturing (and they acquire numbers in the usual way). This
1506 is the same as Perl's /n option. Note that, when this option is set,
1507 references to capture groups (backreferences or recursion/subroutine
1508 calls) may only refer to named groups, though the reference can be by
1509 name or by number.
1510 PCRE2_NO_AUTO_POSSESS
1512 If this option is set, it disables "auto-possessification", which is an
1514 optimization that, for example, turns a+b into a++b in order to avoid
1515 backtracks into a+ that can never be successful. However, if callouts
1516 are in use, auto-possessification means that some callouts are never
1517 taken. You can set this option if you want the matching functions to do
1518 a full unoptimized search and run all the callouts, but it is mainly
1519 provided for testing purposes.
1520 PCRE2_NO_DOTSTAR_ANCHOR
1522 If this option is set, it disables an optimization that is applied when
1524 .* is the first significant item in a top-level branch of a pattern,
1525 and all the other branches also start with .* or with \A or \G or ^.
1526 The optimization is automatically disabled for .* if it is inside an
1527 atomic group or a capture group that is the subject of a backreference,
1528 or if the pattern contains (*PRUNE) or (*SKIP). When the optimization
1529 is not disabled, such a pattern is automatically anchored if
1530 PCRE2_DOTALL is set for all the .* items and PCRE2_MULTILINE is not set
1531 for any ^ items. Otherwise, the fact that any match must start either
1532 at the start of the subject or following a newline is remembered. Like
1533 other optimizations, this can cause callouts to be skipped.
1534 PCRE2_NO_START_OPTIMIZE
1536 This is an option whose main effect is at matching time. It does not
1538 change what pcre2_compile() generates, but it does affect the output of
1539 the JIT compiler.
1540 There are a number of optimizations that may occur at the start of a
1542 match, in order to speed up the process. For example, if it is known
1543 that an unanchored match must start with a specific code unit value,
1544 the matching code searches the subject for that value, and fails imme‐
1545 diately if it cannot find it, without actually running the main match‐
1546 ing function. This means that a special item such as (*COMMIT) at the
1547 start of a pattern is not considered until after a suitable starting
1548 point for the match has been found. Also, when callouts or (*MARK)
1549 items are in use, these "start-up" optimizations can cause them to be
1550 skipped if the pattern is never actually used. The start-up optimiza‐
1551 tions are in effect a pre-scan of the subject that takes place before
1552 the pattern is run.
1553 The PCRE2_NO_START_OPTIMIZE option disables the start-up optimizations,
1555 possibly causing performance to suffer, but ensuring that in cases
1556 where the result is "no match", the callouts do occur, and that items
1557 such as (*COMMIT) and (*MARK) are considered at every possible starting
1558 position in the subject string.
1559 Setting PCRE2_NO_START_OPTIMIZE may change the outcome of a matching
1561 operation. Consider the pattern
1562 (*COMMIT)ABC
1564 When this is compiled, PCRE2 records the fact that a match must start
1566 with the character "A". Suppose the subject string is "DEFABC". The
1567 start-up optimization scans along the subject, finds "A" and runs the
1568 first match attempt from there. The (*COMMIT) item means that the pat‐
1569 tern must match the current starting position, which in this case, it
1570 does. However, if the same match is run with PCRE2_NO_START_OPTIMIZE
1571 set, the initial scan along the subject string does not happen. The
1572 first match attempt is run starting from "D" and when this fails,
1573 (*COMMIT) prevents any further matches being tried, so the overall re‐
1574 sult is "no match".
1575 As another start-up optimization makes use of a minimum length for a
1577 matching subject, which is recorded when possible. Consider the pattern
1578 (*MARK:1)B(*MARK:2)(X|Y)
1580 The minimum length for a match is two characters. If the subject is
1582 "XXBB", the "starting character" optimization skips "XX", then tries to
1583 match "BB", which is long enough. In the process, (*MARK:2) is encoun‐
1584 tered and remembered. When the match attempt fails, the next "B" is
1585 found, but there is only one character left, so there are no more at‐
1586 tempts, and "no match" is returned with the "last mark seen" set to
1587 "2". If NO_START_OPTIMIZE is set, however, matches are tried at every
1588 possible starting position, including at the end of the subject, where
1589 (*MARK:1) is encountered, but there is no "B", so the "last mark seen"
1590 that is returned is "1". In this case, the optimizations do not affect
1591 the overall match result, which is still "no match", but they do affect
1592 the auxiliary information that is returned.
1593 PCRE2_NO_UTF_CHECK
1595 When PCRE2_UTF is set, the validity of the pattern as a UTF string is
1597 automatically checked. There are discussions about the validity of
1598 UTF-8 strings, UTF-16 strings, and UTF-32 strings in the pcre2unicode
1599 document. If an invalid UTF sequence is found, pcre2_compile() returns
1600 a negative error code.
1601 If you know that your pattern is a valid UTF string, and you want to
1603 skip this check for performance reasons, you can set the
1604 PCRE2_NO_UTF_CHECK option. When it is set, the effect of passing an in‐
1605 valid UTF string as a pattern is undefined. It may cause your program
1606 to crash or loop.
1607 Note that this option can also be passed to pcre2_match() and
1609 pcre2_dfa_match(), to suppress UTF validity checking of the subject
1610 string.
1611 Note also that setting PCRE2_NO_UTF_CHECK at compile time does not dis‐
1613 able the error that is given if an escape sequence for an invalid Uni‐
1614 code code point is encountered in the pattern. In particular, the so-
1615 called "surrogate" code points (0xd800 to 0xdfff) are invalid. If you
1616 want to allow escape sequences such as \x{d800} you can set the
1617 PCRE2_EXTRA_ALLOW_SURROGATE_ESCAPES extra option, as described in the
1618 section entitled "Extra compile options" below. However, this is pos‐
1619 sible only in UTF-8 and UTF-32 modes, because these values are not rep‐
1620 resentable in UTF-16.
1621 PCRE2_UCP
1623 This option has two effects. Firstly, it change the way PCRE2 processes
1625 \B, \b, \D, \d, \S, \s, \W, \w, and some of the POSIX character
1626 classes. By default, only ASCII characters are recognized, but if
1627 PCRE2_UCP is set, Unicode properties are used instead to classify char‐
1628 acters. More details are given in the section on generic character
1629 types in the pcre2pattern page. If you set PCRE2_UCP, matching one of
1630 the items it affects takes much longer.
1631 The second effect of PCRE2_UCP is to force the use of Unicode proper‐
1633 ties for upper/lower casing operations on characters with code points
1634 greater than 127, even when PCRE2_UTF is not set. This makes it possi‐
1635 ble, for example, to process strings in the 16-bit UCS-2 code. This op‐
1636 tion is available only if PCRE2 has been compiled with Unicode support
1637 (which is the default).
1638 PCRE2_UNGREEDY
1640 This option inverts the "greediness" of the quantifiers so that they
1642 are not greedy by default, but become greedy if followed by "?". It is
1643 not compatible with Perl. It can also be set by a (?U) option setting
1644 within the pattern.
1645 PCRE2_USE_OFFSET_LIMIT
1647 This option must be set for pcre2_compile() if pcre2_set_offset_limit()
1649 is going to be used to set a non-default offset limit in a match con‐
1650 text for matches that use this pattern. An error is generated if an
1651 offset limit is set without this option. For more details, see the de‐
1652 scription of pcre2_set_offset_limit() in the section that describes
1653 match contexts. See also the PCRE2_FIRSTLINE option above.
1654 PCRE2_UTF
1656 This option causes PCRE2 to regard both the pattern and the subject
1658 strings that are subsequently processed as strings of UTF characters
1659 instead of single-code-unit strings. It is available when PCRE2 is
1660 built to include Unicode support (which is the default). If Unicode
1661 support is not available, the use of this option provokes an error. De‐
1662 tails of how PCRE2_UTF changes the behaviour of PCRE2 are given in the
1663 pcre2unicode page. In particular, note that it changes the way
1664 PCRE2_CASELESS handles characters with code points greater than 127.
1665 Extra compile options
1667 The option bits that can be set in a compile context by calling the
1669 pcre2_set_compile_extra_options() function are as follows:
1670 PCRE2_EXTRA_ALLOW_LOOKAROUND_BSK
1672 Since release 10.38 PCRE2 has forbidden the use of \K within lookaround
1674 assertions, following Perl's lead. This option is provided to re-enable
1675 the previous behaviour (act in positive lookarounds, ignore in negative
1676 ones) in case anybody is relying on it.
1677 PCRE2_EXTRA_ALLOW_SURROGATE_ESCAPES
1679 This option applies when compiling a pattern in UTF-8 or UTF-32 mode.
1681 It is forbidden in UTF-16 mode, and ignored in non-UTF modes. Unicode
1682 "surrogate" code points in the range 0xd800 to 0xdfff are used in pairs
1683 in UTF-16 to encode code points with values in the range 0x10000 to
1684 0x10ffff. The surrogates cannot therefore be represented in UTF-16.
1685 They can be represented in UTF-8 and UTF-32, but are defined as invalid
1686 code points, and cause errors if encountered in a UTF-8 or UTF-32
1687 string that is being checked for validity by PCRE2.
1688 These values also cause errors if encountered in escape sequences such
1690 as \x{d912} within a pattern. However, it seems that some applications,
1691 when using PCRE2 to check for unwanted characters in UTF-8 strings, ex‐
1692 plicitly test for the surrogates using escape sequences. The
1693 PCRE2_NO_UTF_CHECK option does not disable the error that occurs, be‐
1694 cause it applies only to the testing of input strings for UTF validity.
1695 If the extra option PCRE2_EXTRA_ALLOW_SURROGATE_ESCAPES is set, surro‐
1697 gate code point values in UTF-8 and UTF-32 patterns no longer provoke
1698 errors and are incorporated in the compiled pattern. However, they can
1699 only match subject characters if the matching function is called with
1700 PCRE2_NO_UTF_CHECK set.
1701 PCRE2_EXTRA_ALT_BSUX
1703 The original option PCRE2_ALT_BSUX causes PCRE2 to process \U, \u, and
1705 \x in the way that ECMAscript (aka JavaScript) does. Additional func‐
1706 tionality was defined by ECMAscript 6; setting PCRE2_EXTRA_ALT_BSUX has
1707 the effect of PCRE2_ALT_BSUX, but in addition it recognizes \u{hhh..}
1708 as a hexadecimal character code, where hhh.. is any number of hexadeci‐
1709 mal digits.
1710 PCRE2_EXTRA_BAD_ESCAPE_IS_LITERAL
1712 This is a dangerous option. Use with care. By default, an unrecognized
1714 escape such as \j or a malformed one such as \x{2z} causes a compile-
1715 time error when detected by pcre2_compile(). Perl is somewhat inconsis‐
1716 tent in handling such items: for example, \j is treated as a literal
1717 "j", and non-hexadecimal digits in \x{} are just ignored, though warn‐
1718 ings are given in both cases if Perl's warning switch is enabled. How‐
1719 ever, a malformed octal number after \o{ always causes an error in
1720 Perl.
1721 If the PCRE2_EXTRA_BAD_ESCAPE_IS_LITERAL extra option is passed to
1723 pcre2_compile(), all unrecognized or malformed escape sequences are
1724 treated as single-character escapes. For example, \j is a literal "j"
1725 and \x{2z} is treated as the literal string "x{2z}". Setting this op‐
1726 tion means that typos in patterns may go undetected and have unexpected
1727 results. Also note that a sequence such as [\N{] is interpreted as a
1728 malformed attempt at [\N{...}] and so is treated as [N{] whereas [\N]
1729 gives an error because an unqualified \N is a valid escape sequence but
1730 is not supported in a character class. To reiterate: this is a danger‐
1731 ous option. Use with great care.
1732 PCRE2_EXTRA_ESCAPED_CR_IS_LF
1734 There are some legacy applications where the escape sequence \r in a
1736 pattern is expected to match a newline. If this option is set, \r in a
1737 pattern is converted to \n so that it matches a LF (linefeed) instead
1738 of a CR (carriage return) character. The option does not affect a lit‐
1739 eral CR in the pattern, nor does it affect CR specified as an explicit
1740 code point such as \x{0D}.
1741 PCRE2_EXTRA_MATCH_LINE
1743 This option is provided for use by the -x option of pcre2grep. It
1745 causes the pattern only to match complete lines. This is achieved by
1746 automatically inserting the code for "^(?:" at the start of the com‐
1747 piled pattern and ")$" at the end. Thus, when PCRE2_MULTILINE is set,
1748 the matched line may be in the middle of the subject string. This op‐
1749 tion can be used with PCRE2_LITERAL.
1750 PCRE2_EXTRA_MATCH_WORD
1752 This option is provided for use by the -w option of pcre2grep. It
1754 causes the pattern only to match strings that have a word boundary at
1755 the start and the end. This is achieved by automatically inserting the
1756 code for "\b(?:" at the start of the compiled pattern and ")\b" at the
1757 end. The option may be used with PCRE2_LITERAL. However, it is ignored
1758 if PCRE2_EXTRA_MATCH_LINE is also set.
1759
1761 int pcre2_jit_compile(pcre2_code *code, uint32_t options);
1763 int pcre2_jit_match(const pcre2_code *code, PCRE2_SPTR subject,
1765 PCRE2_SIZE length, PCRE2_SIZE startoffset,
1766 uint32_t options, pcre2_match_data *match_data,
1767 pcre2_match_context *mcontext);
1768 void pcre2_jit_free_unused_memory(pcre2_general_context *gcontext);
1770 pcre2_jit_stack *pcre2_jit_stack_create(PCRE2_SIZE startsize,
1772 PCRE2_SIZE maxsize, pcre2_general_context *gcontext);
1773 void pcre2_jit_stack_assign(pcre2_match_context *mcontext,
1775 pcre2_jit_callback callback_function, void *callback_data);
1776 void pcre2_jit_stack_free(pcre2_jit_stack *jit_stack);
1778 These functions provide support for JIT compilation, which, if the
1780 just-in-time compiler is available, further processes a compiled pat‐
1781 tern into machine code that executes much faster than the pcre2_match()
1782 interpretive matching function. Full details are given in the pcre2jit
1783 documentation.
1784 JIT compilation is a heavyweight optimization. It can take some time
1786 for patterns to be analyzed, and for one-off matches and simple pat‐
1787 terns the benefit of faster execution might be offset by a much slower
1788 compilation time. Most (but not all) patterns can be optimized by the
1789 JIT compiler.
1790
1792 const uint8_t *pcre2_maketables(pcre2_general_context *gcontext);
1794 void pcre2_maketables_free(pcre2_general_context *gcontext,
1796 const uint8_t *tables);
1797 PCRE2 handles caseless matching, and determines whether characters are
1799 letters, digits, or whatever, by reference to a set of tables, indexed
1800 by character code point. However, this applies only to characters whose
1801 code points are less than 256. By default, higher-valued code points
1802 never match escapes such as \w or \d.
1803 When PCRE2 is built with Unicode support (the default), certain Unicode
1805 character properties can be tested with \p and \P, or, alternatively,
1806 the PCRE2_UCP option can be set when a pattern is compiled; this causes
1807 \w and friends to use Unicode property support instead of the built-in
1808 tables. PCRE2_UCP also causes upper/lower casing operations on charac‐
1809 ters with code points greater than 127 to use Unicode properties. These
1810 effects apply even when PCRE2_UTF is not set.
1811 The use of locales with Unicode is discouraged. If you are handling
1813 characters with code points greater than 127, you should either use
1814 Unicode support, or use locales, but not try to mix the two.
1815 PCRE2 contains a built-in set of character tables that are used by de‐
1817 fault. These are sufficient for many applications. Normally, the in‐
1818 ternal tables recognize only ASCII characters. However, when PCRE2 is
1819 built, it is possible to cause the internal tables to be rebuilt in the
1820 default "C" locale of the local system, which may cause them to be dif‐
1821 ferent.
1822 The built-in tables can be overridden by tables supplied by the appli‐
1824 cation that calls PCRE2. These may be created in a different locale
1825 from the default. As more and more applications change to using Uni‐
1826 code, the need for this locale support is expected to die away.
1827 External tables are built by calling the pcre2_maketables() function,
1829 in the relevant locale. The only argument to this function is a general
1830 context, which can be used to pass a custom memory allocator. If the
1831 argument is NULL, the system malloc() is used. The result can be passed
1832 to pcre2_compile() as often as necessary, by creating a compile context
1833 and calling pcre2_set_character_tables() to set the tables pointer
1834 therein.
1835 For example, to build and use tables that are appropriate for the
1837 French locale (where accented characters with values greater than 127
1838 are treated as letters), the following code could be used:
1839 setlocale(LC_CTYPE, "fr_FR");
1841 tables = pcre2_maketables(NULL);
1842 ccontext = pcre2_compile_context_create(NULL);
1843 pcre2_set_character_tables(ccontext, tables);
1844 re = pcre2_compile(..., ccontext);
1845 The locale name "fr_FR" is used on Linux and other Unix-like systems;
1847 if you are using Windows, the name for the French locale is "french".
1848 The pointer that is passed (via the compile context) to pcre2_compile()
1850 is saved with the compiled pattern, and the same tables are used by the
1851 matching functions. Thus, for any single pattern, compilation and
1852 matching both happen in the same locale, but different patterns can be
1853 processed in different locales.
1854 It is the caller's responsibility to ensure that the memory containing
1856 the tables remains available while they are still in use. When they are
1857 no longer needed, you can discard them using pcre2_maketables_free(),
1858 which should pass as its first parameter the same global context that
1859 was used to create the tables.
1860 Saving locale tables
1862 The tables described above are just a sequence of binary bytes, which
1864 makes them independent of hardware characteristics such as endianness
1865 or whether the processor is 32-bit or 64-bit. A copy of the result of
1866 pcre2_maketables() can therefore be saved in a file or elsewhere and
1867 re-used later, even in a different program or on another computer. The
1868 size of the tables (number of bytes) must be obtained by calling
1869 pcre2_config() with the PCRE2_CONFIG_TABLES_LENGTH option because
1870 pcre2_maketables() does not return this value. Note that the
1871 pcre2_dftables program, which is part of the PCRE2 build system, can be
1872 used stand-alone to create a file that contains a set of binary tables.
1873 See the pcre2build documentation for details.
1874
1876 int pcre2_pattern_info(const pcre2 *code, uint32_t what, void *where);
1878 The pcre2_pattern_info() function returns general information about a
1880 compiled pattern. For information about callouts, see the next section.
1881 The first argument for pcre2_pattern_info() is a pointer to the com‐
1882 piled pattern. The second argument specifies which piece of information
1883 is required, and the third argument is a pointer to a variable to re‐
1884 ceive the data. If the third argument is NULL, the first argument is
1885 ignored, and the function returns the size in bytes of the variable
1886 that is required for the information requested. Otherwise, the yield of
1887 the function is zero for success, or one of the following negative num‐
1888 bers:
1889 PCRE2_ERROR_NULL the argument code was NULL
1891 PCRE2_ERROR_BADMAGIC the "magic number" was not found
1892 PCRE2_ERROR_BADOPTION the value of what was invalid
1893 PCRE2_ERROR_UNSET the requested field is not set
1894 The "magic number" is placed at the start of each compiled pattern as a
1896 simple check against passing an arbitrary memory pointer. Here is a
1897 typical call of pcre2_pattern_info(), to obtain the length of the com‐
1898 piled pattern:
1899 int rc;
1901 size_t length;
1902 rc = pcre2_pattern_info(
1903 re, /* result of pcre2_compile() */
1904 PCRE2_INFO_SIZE, /* what is required */
1905 &length); /* where to put the data */
1906 The possible values for the second argument are defined in pcre2.h, and
1908 are as follows:
1909 PCRE2_INFO_ALLOPTIONS
1911 PCRE2_INFO_ARGOPTIONS
1912 PCRE2_INFO_EXTRAOPTIONS
1913 Return copies of the pattern's options. The third argument should point
1915 to a uint32_t variable. PCRE2_INFO_ARGOPTIONS returns exactly the op‐
1916 tions that were passed to pcre2_compile(), whereas PCRE2_INFO_ALLOP‐
1917 TIONS returns the compile options as modified by any top-level (*XXX)
1918 option settings such as (*UTF) at the start of the pattern itself.
1919 PCRE2_INFO_EXTRAOPTIONS returns the extra options that were set in the
1920 compile context by calling the pcre2_set_compile_extra_options() func‐
1921 tion.
1922 For example, if the pattern /(*UTF)abc/ is compiled with the PCRE2_EX‐
1924 TENDED option, the result for PCRE2_INFO_ALLOPTIONS is PCRE2_EXTENDED
1925 and PCRE2_UTF. Option settings such as (?i) that can change within a
1926 pattern do not affect the result of PCRE2_INFO_ALLOPTIONS, even if they
1927 appear right at the start of the pattern. (This was different in some
1928 earlier releases.)
1929 A pattern compiled without PCRE2_ANCHORED is automatically anchored by
1931 PCRE2 if the first significant item in every top-level branch is one of
1932 the following:
1933 ^ unless PCRE2_MULTILINE is set
1935 \A always
1936 \G always
1937 .* sometimes - see below
1938 When .* is the first significant item, anchoring is possible only when
1940 all the following are true:
1941 .* is not in an atomic group
1943 .* is not in a capture group that is the subject
1944 of a backreference
1945 PCRE2_DOTALL is in force for .*
1946 Neither (*PRUNE) nor (*SKIP) appears in the pattern
1947 PCRE2_NO_DOTSTAR_ANCHOR is not set
1948 For patterns that are auto-anchored, the PCRE2_ANCHORED bit is set in
1950 the options returned for PCRE2_INFO_ALLOPTIONS.
1951 PCRE2_INFO_BACKREFMAX
1953 Return the number of the highest backreference in the pattern. The
1955 third argument should point to a uint32_t variable. Named capture
1956 groups acquire numbers as well as names, and these count towards the
1957 highest backreference. Backreferences such as \4 or \g{12} match the
1958 captured characters of the given group, but in addition, the check that
1959 a capture group is set in a conditional group such as (?(3)a|b) is also
1960 a backreference. Zero is returned if there are no backreferences.
1961 PCRE2_INFO_BSR
1963 The output is a uint32_t integer whose value indicates what character
1965 sequences the \R escape sequence matches. A value of PCRE2_BSR_UNICODE
1966 means that \R matches any Unicode line ending sequence; a value of
1967 PCRE2_BSR_ANYCRLF means that \R matches only CR, LF, or CRLF.
1968 PCRE2_INFO_CAPTURECOUNT
1970 Return the highest capture group number in the pattern. In patterns
1972 where (?| is not used, this is also the total number of capture groups.
1973 The third argument should point to a uint32_t variable.
1974 PCRE2_INFO_DEPTHLIMIT
1976 If the pattern set a backtracking depth limit by including an item of
1978 the form (*LIMIT_DEPTH=nnnn) at the start, the value is returned. The
1979 third argument should point to a uint32_t integer. If no such value has
1980 been set, the call to pcre2_pattern_info() returns the error PCRE2_ER‐
1981 ROR_UNSET. Note that this limit will only be used during matching if it
1982 is less than the limit set or defaulted by the caller of the match
1983 function.
1984 PCRE2_INFO_FIRSTBITMAP
1986 In the absence of a single first code unit for a non-anchored pattern,
1988 pcre2_compile() may construct a 256-bit table that defines a fixed set
1989 of values for the first code unit in any match. For example, a pattern
1990 that starts with [abc] results in a table with three bits set. When
1991 code unit values greater than 255 are supported, the flag bit for 255
1992 means "any code unit of value 255 or above". If such a table was con‐
1993 structed, a pointer to it is returned. Otherwise NULL is returned. The
1994 third argument should point to a const uint8_t * variable.
1995 PCRE2_INFO_FIRSTCODETYPE
1997 Return information about the first code unit of any matched string, for
1999 a non-anchored pattern. The third argument should point to a uint32_t
2000 variable. If there is a fixed first value, for example, the letter "c"
2001 from a pattern such as (cat|cow|coyote), 1 is returned, and the value
2002 can be retrieved using PCRE2_INFO_FIRSTCODEUNIT. If there is no fixed
2003 first value, but it is known that a match can occur only at the start
2004 of the subject or following a newline in the subject, 2 is returned.
2005 Otherwise, and for anchored patterns, 0 is returned.
2006 PCRE2_INFO_FIRSTCODEUNIT
2008 Return the value of the first code unit of any matched string for a
2010 pattern where PCRE2_INFO_FIRSTCODETYPE returns 1; otherwise return 0.
2011 The third argument should point to a uint32_t variable. In the 8-bit
2012 library, the value is always less than 256. In the 16-bit library the
2013 value can be up to 0xffff. In the 32-bit library in UTF-32 mode the
2014 value can be up to 0x10ffff, and up to 0xffffffff when not using UTF-32
2015 mode.
2016 PCRE2_INFO_FRAMESIZE
2018 Return the size (in bytes) of the data frames that are used to remember
2020 backtracking positions when the pattern is processed by pcre2_match()
2021 without the use of JIT. The third argument should point to a size_t
2022 variable. The frame size depends on the number of capturing parentheses
2023 in the pattern. Each additional capture group adds two PCRE2_SIZE vari‐
2024 ables.
2025 PCRE2_INFO_HASBACKSLASHC
2027 Return 1 if the pattern contains any instances of \C, otherwise 0. The
2029 third argument should point to a uint32_t variable.
2030 PCRE2_INFO_HASCRORLF
2032 Return 1 if the pattern contains any explicit matches for CR or LF
2034 characters, otherwise 0. The third argument should point to a uint32_t
2035 variable. An explicit match is either a literal CR or LF character, or
2036 \r or \n or one of the equivalent hexadecimal or octal escape se‐
2037 quences.
2038 PCRE2_INFO_HEAPLIMIT
2040 If the pattern set a heap memory limit by including an item of the form
2042 (*LIMIT_HEAP=nnnn) at the start, the value is returned. The third argu‐
2043 ment should point to a uint32_t integer. If no such value has been set,
2044 the call to pcre2_pattern_info() returns the error PCRE2_ERROR_UNSET.
2045 Note that this limit will only be used during matching if it is less
2046 than the limit set or defaulted by the caller of the match function.
2047 PCRE2_INFO_JCHANGED
2049 Return 1 if the (?J) or (?-J) option setting is used in the pattern,
2051 otherwise 0. The third argument should point to a uint32_t variable.
2052 (?J) and (?-J) set and unset the local PCRE2_DUPNAMES option, respec‐
2053 tively.
2054 PCRE2_INFO_JITSIZE
2056 If the compiled pattern was successfully processed by pcre2_jit_com‐
2058 pile(), return the size of the JIT compiled code, otherwise return
2059 zero. The third argument should point to a size_t variable.
2060 PCRE2_INFO_LASTCODETYPE
2062 Returns 1 if there is a rightmost literal code unit that must exist in
2064 any matched string, other than at its start. The third argument should
2065 point to a uint32_t variable. If there is no such value, 0 is returned.
2066 When 1 is returned, the code unit value itself can be retrieved using
2067 PCRE2_INFO_LASTCODEUNIT. For anchored patterns, a last literal value is
2068 recorded only if it follows something of variable length. For example,
2069 for the pattern /^a\d+z\d+/ the returned value is 1 (with "z" returned
2070 from PCRE2_INFO_LASTCODEUNIT), but for /^a\dz\d/ the returned value is
2071 0.
2072 PCRE2_INFO_LASTCODEUNIT
2074 Return the value of the rightmost literal code unit that must exist in
2076 any matched string, other than at its start, for a pattern where
2077 PCRE2_INFO_LASTCODETYPE returns 1. Otherwise, return 0. The third argu‐
2078 ment should point to a uint32_t variable.
2079 PCRE2_INFO_MATCHEMPTY
2081 Return 1 if the pattern might match an empty string, otherwise 0. The
2083 third argument should point to a uint32_t variable. When a pattern con‐
2084 tains recursive subroutine calls it is not always possible to determine
2085 whether or not it can match an empty string. PCRE2 takes a cautious ap‐
2086 proach and returns 1 in such cases.
2087 PCRE2_INFO_MATCHLIMIT
2089 If the pattern set a match limit by including an item of the form
2091 (*LIMIT_MATCH=nnnn) at the start, the value is returned. The third ar‐
2092 gument should point to a uint32_t integer. If no such value has been
2093 set, the call to pcre2_pattern_info() returns the error PCRE2_ERROR_UN‐
2094 SET. Note that this limit will only be used during matching if it is
2095 less than the limit set or defaulted by the caller of the match func‐
2096 tion.
2097 PCRE2_INFO_MAXLOOKBEHIND
2099 A lookbehind assertion moves back a certain number of characters (not
2101 code units) when it starts to process each of its branches. This re‐
2102 quest returns the largest of these backward moves. The third argument
2103 should point to a uint32_t integer. The simple assertions \b and \B re‐
2104 quire a one-character lookbehind and cause PCRE2_INFO_MAXLOOKBEHIND to
2105 return 1 in the absence of anything longer. \A also registers a one-
2106 character lookbehind, though it does not actually inspect the previous
2107 character.
2108 Note that this information is useful for multi-segment matching only if
2110 the pattern contains no nested lookbehinds. For example, the pattern
2111 (?<=a(?<=ba)c) returns a maximum lookbehind of 2, but when it is pro‐
2112 cessed, the first lookbehind moves back by two characters, matches one
2113 character, then the nested lookbehind also moves back by two charac‐
2114 ters. This puts the matching point three characters earlier than it was
2115 at the start. PCRE2_INFO_MAXLOOKBEHIND is really only useful as a de‐
2116 bugging tool. See the pcre2partial documentation for a discussion of
2117 multi-segment matching.
2118 PCRE2_INFO_MINLENGTH
2120 If a minimum length for matching subject strings was computed, its
2122 value is returned. Otherwise the returned value is 0. This value is not
2123 computed when PCRE2_NO_START_OPTIMIZE is set. The value is a number of
2124 characters, which in UTF mode may be different from the number of code
2125 units. The third argument should point to a uint32_t variable. The
2126 value is a lower bound to the length of any matching string. There may
2127 not be any strings of that length that do actually match, but every
2128 string that does match is at least that long.
2129 PCRE2_INFO_NAMECOUNT
2131 PCRE2_INFO_NAMEENTRYSIZE
2132 PCRE2_INFO_NAMETABLE
2133 PCRE2 supports the use of named as well as numbered capturing parenthe‐
2135 ses. The names are just an additional way of identifying the parenthe‐
2136 ses, which still acquire numbers. Several convenience functions such as
2137 pcre2_substring_get_byname() are provided for extracting captured sub‐
2138 strings by name. It is also possible to extract the data directly, by
2139 first converting the name to a number in order to access the correct
2140 pointers in the output vector (described with pcre2_match() below). To
2141 do the conversion, you need to use the name-to-number map, which is de‐
2142 scribed by these three values.
2143 The map consists of a number of fixed-size entries. PCRE2_INFO_NAME‐
2145 COUNT gives the number of entries, and PCRE2_INFO_NAMEENTRYSIZE gives
2146 the size of each entry in code units; both of these return a uint32_t
2147 value. The entry size depends on the length of the longest name.
2148 PCRE2_INFO_NAMETABLE returns a pointer to the first entry of the table.
2150 This is a PCRE2_SPTR pointer to a block of code units. In the 8-bit li‐
2151 brary, the first two bytes of each entry are the number of the captur‐
2152 ing parenthesis, most significant byte first. In the 16-bit library,
2153 the pointer points to 16-bit code units, the first of which contains
2154 the parenthesis number. In the 32-bit library, the pointer points to
2155 32-bit code units, the first of which contains the parenthesis number.
2156 The rest of the entry is the corresponding name, zero terminated.
2157 The names are in alphabetical order. If (?| is used to create multiple
2159 capture groups with the same number, as described in the section on du‐
2160 plicate group numbers in the pcre2pattern page, the groups may be given
2161 the same name, but there is only one entry in the table. Different
2162 names for groups of the same number are not permitted.
2163 Duplicate names for capture groups with different numbers are permit‐
2165 ted, but only if PCRE2_DUPNAMES is set. They appear in the table in the
2166 order in which they were found in the pattern. In the absence of (?|
2167 this is the order of increasing number; when (?| is used this is not
2168 necessarily the case because later capture groups may have lower num‐
2169 bers.
2170 As a simple example of the name/number table, consider the following
2172 pattern after compilation by the 8-bit library (assume PCRE2_EXTENDED
2173 is set, so white space - including newlines - is ignored):
2174 (?<date> (?<year>(\d\d)?\d\d) -
2176 (?<month>\d\d) - (?<day>\d\d) )
2177 There are four named capture groups, so the table has four entries, and
2179 each entry in the table is eight bytes long. The table is as follows,
2180 with non-printing bytes shows in hexadecimal, and undefined bytes shown
2181 as ??:
2182 00 01 d a t e 00 ??
2184 00 05 d a y 00 ?? ??
2185 00 04 m o n t h 00
2186 00 02 y e a r 00 ??
2187 When writing code to extract data from named capture groups using the
2189 name-to-number map, remember that the length of the entries is likely
2190 to be different for each compiled pattern.
2191 PCRE2_INFO_NEWLINE
2193 The output is one of the following uint32_t values:
2195 PCRE2_NEWLINE_CR Carriage return (CR)
2197 PCRE2_NEWLINE_LF Linefeed (LF)
2198 PCRE2_NEWLINE_CRLF Carriage return, linefeed (CRLF)
2199 PCRE2_NEWLINE_ANY Any Unicode line ending
2200 PCRE2_NEWLINE_ANYCRLF Any of CR, LF, or CRLF
2201 PCRE2_NEWLINE_NUL The NUL character (binary zero)
2202 This identifies the character sequence that will be recognized as mean‐
2204 ing "newline" while matching.
2205 PCRE2_INFO_SIZE
2207 Return the size of the compiled pattern in bytes (for all three li‐
2209 braries). The third argument should point to a size_t variable. This
2210 value includes the size of the general data block that precedes the
2211 code units of the compiled pattern itself. The value that is used when
2212 pcre2_compile() is getting memory in which to place the compiled pat‐
2213 tern may be slightly larger than the value returned by this option, be‐
2214 cause there are cases where the code that calculates the size has to
2215 over-estimate. Processing a pattern with the JIT compiler does not al‐
2216 ter the value returned by this option.
2217
2219 int pcre2_callout_enumerate(const pcre2_code *code,
2221 int (*callback)(pcre2_callout_enumerate_block *, void *),
2222 void *user_data);
2223 A script language that supports the use of string arguments in callouts
2225 might like to scan all the callouts in a pattern before running the
2226 match. This can be done by calling pcre2_callout_enumerate(). The first
2227 argument is a pointer to a compiled pattern, the second points to a
2228 callback function, and the third is arbitrary user data. The callback
2229 function is called for every callout in the pattern in the order in
2230 which they appear. Its first argument is a pointer to a callout enumer‐
2231 ation block, and its second argument is the user_data value that was
2232 passed to pcre2_callout_enumerate(). The contents of the callout enu‐
2233 meration block are described in the pcre2callout documentation, which
2234 also gives further details about callouts.
2235
2237 It is possible to save compiled patterns on disc or elsewhere, and
2239 reload them later, subject to a number of restrictions. The host on
2240 which the patterns are reloaded must be running the same version of
2241 PCRE2, with the same code unit width, and must also have the same endi‐
2242 anness, pointer width, and PCRE2_SIZE type. Before compiled patterns
2243 can be saved, they must be converted to a "serialized" form, which in
2244 the case of PCRE2 is really just a bytecode dump. The functions whose
2245 names begin with pcre2_serialize_ are used for converting to and from
2246 the serialized form. They are described in the pcre2serialize documen‐
2247 tation. Note that PCRE2 serialization does not convert compiled pat‐
2248 terns to an abstract format like Java or .NET serialization.
2249
2251 pcre2_match_data *pcre2_match_data_create(uint32_t ovecsize,
2253 pcre2_general_context *gcontext);
2254 pcre2_match_data *pcre2_match_data_create_from_pattern(
2256 const pcre2_code *code, pcre2_general_context *gcontext);
2257 void pcre2_match_data_free(pcre2_match_data *match_data);
2259 Information about a successful or unsuccessful match is placed in a
2261 match data block, which is an opaque structure that is accessed by
2262 function calls. In particular, the match data block contains a vector
2263 of offsets into the subject string that define the matched parts of the
2264 subject. This is known as the ovector.
2265 Before calling pcre2_match(), pcre2_dfa_match(), or pcre2_jit_match()
2267 you must create a match data block by calling one of the creation func‐
2268 tions above. For pcre2_match_data_create(), the first argument is the
2269 number of pairs of offsets in the ovector.
2270 When using pcre2_match(), one pair of offsets is required to identify
2272 the string that matched the whole pattern, with an additional pair for
2273 each captured substring. For example, a value of 4 creates enough space
2274 to record the matched portion of the subject plus three captured sub‐
2275 strings.
2276 When using pcre2_dfa_match() there may be multiple matched substrings
2278 of different lengths at the same point in the subject. The ovector
2279 should be made large enough to hold as many as are expected.
2280 A minimum of at least 1 pair is imposed by pcre2_match_data_create(),
2282 so it is always possible to return the overall matched string in the
2283 case of pcre2_match() or the longest match in the case of
2284 pcre2_dfa_match().
2285 The second argument of pcre2_match_data_create() is a pointer to a gen‐
2287 eral context, which can specify custom memory management for obtaining
2288 the memory for the match data block. If you are not using custom memory
2289 management, pass NULL, which causes malloc() to be used.
2290 For pcre2_match_data_create_from_pattern(), the first argument is a
2292 pointer to a compiled pattern. The ovector is created to be exactly the
2293 right size to hold all the substrings a pattern might capture when
2294 matched using pcre2_match(). You should not use this call when matching
2295 with pcre2_dfa_match(). The second argument is again a pointer to a
2296 general context, but in this case if NULL is passed, the memory is ob‐
2297 tained using the same allocator that was used for the compiled pattern
2298 (custom or default).
2299 A match data block can be used many times, with the same or different
2301 compiled patterns. You can extract information from a match data block
2302 after a match operation has finished, using functions that are de‐
2303 scribed in the sections on matched strings and other match data below.
2304 When a call of pcre2_match() fails, valid data is available in the
2306 match block only when the error is PCRE2_ERROR_NOMATCH, PCRE2_ER‐
2307 ROR_PARTIAL, or one of the error codes for an invalid UTF string. Ex‐
2308 actly what is available depends on the error, and is detailed below.
2309 When one of the matching functions is called, pointers to the compiled
2311 pattern and the subject string are set in the match data block so that
2312 they can be referenced by the extraction functions after a successful
2313 match. After running a match, you must not free a compiled pattern or a
2314 subject string until after all operations on the match data block (for
2315 that match) have taken place, unless, in the case of the subject
2316 string, you have used the PCRE2_COPY_MATCHED_SUBJECT option, which is
2317 described in the section entitled "Option bits for pcre2_match()" be‐
2318 low.
2319 When a match data block itself is no longer needed, it should be freed
2321 by calling pcre2_match_data_free(). If this function is called with a
2322 NULL argument, it returns immediately, without doing anything.
2323
2325 int pcre2_match(const pcre2_code *code, PCRE2_SPTR subject,
2327 PCRE2_SIZE length, PCRE2_SIZE startoffset,
2328 uint32_t options, pcre2_match_data *match_data,
2329 pcre2_match_context *mcontext);
2330 The function pcre2_match() is called to match a subject string against
2332 a compiled pattern, which is passed in the code argument. You can call
2333 pcre2_match() with the same code argument as many times as you like, in
2334 order to find multiple matches in the subject string or to match dif‐
2335 ferent subject strings with the same pattern.
2336 This function is the main matching facility of the library, and it op‐
2338 erates in a Perl-like manner. For specialist use there is also an al‐
2339 ternative matching function, which is described below in the section
2340 about the pcre2_dfa_match() function.
2341 Here is an example of a simple call to pcre2_match():
2343 pcre2_match_data *md = pcre2_match_data_create(4, NULL);
2345 int rc = pcre2_match(
2346 re, /* result of pcre2_compile() */
2347 "some string", /* the subject string */
2348 11, /* the length of the subject string */
2349 0, /* start at offset 0 in the subject */
2350 0, /* default options */
2351 md, /* the match data block */
2352 NULL); /* a match context; NULL means use defaults */
2353 If the subject string is zero-terminated, the length can be given as
2355 PCRE2_ZERO_TERMINATED. A match context must be provided if certain less
2356 common matching parameters are to be changed. For details, see the sec‐
2357 tion on the match context above.
2358 The string to be matched by pcre2_match()
2360 The subject string is passed to pcre2_match() as a pointer in subject,
2362 a length in length, and a starting offset in startoffset. The length
2363 and offset are in code units, not characters. That is, they are in
2364 bytes for the 8-bit library, 16-bit code units for the 16-bit library,
2365 and 32-bit code units for the 32-bit library, whether or not UTF pro‐
2366 cessing is enabled. As a special case, if subject is NULL and length is
2367 zero, the subject is assumed to be an empty string. If length is non-
2368 zero, an error occurs if subject is NULL.
2369 If startoffset is greater than the length of the subject, pcre2_match()
2371 returns PCRE2_ERROR_BADOFFSET. When the starting offset is zero, the
2372 search for a match starts at the beginning of the subject, and this is
2373 by far the most common case. In UTF-8 or UTF-16 mode, the starting off‐
2374 set must point to the start of a character, or to the end of the sub‐
2375 ject (in UTF-32 mode, one code unit equals one character, so all off‐
2376 sets are valid). Like the pattern string, the subject may contain bi‐
2377 nary zeros.
2378 A non-zero starting offset is useful when searching for another match
2380 in the same subject by calling pcre2_match() again after a previous
2381 success. Setting startoffset differs from passing over a shortened
2382 string and setting PCRE2_NOTBOL in the case of a pattern that begins
2383 with any kind of lookbehind. For example, consider the pattern
2384 \Biss\B
2386 which finds occurrences of "iss" in the middle of words. (\B matches
2388 only if the current position in the subject is not a word boundary.)
2389 When applied to the string "Mississippi" the first call to
2390 pcre2_match() finds the first occurrence. If pcre2_match() is called
2391 again with just the remainder of the subject, namely "issippi", it does
2392 not match, because \B is always false at the start of the subject,
2393 which is deemed to be a word boundary. However, if pcre2_match() is
2394 passed the entire string again, but with startoffset set to 4, it finds
2395 the second occurrence of "iss" because it is able to look behind the
2396 starting point to discover that it is preceded by a letter.
2397 Finding all the matches in a subject is tricky when the pattern can
2399 match an empty string. It is possible to emulate Perl's /g behaviour by
2400 first trying the match again at the same offset, with the
2401 PCRE2_NOTEMPTY_ATSTART and PCRE2_ANCHORED options, and then if that
2402 fails, advancing the starting offset and trying an ordinary match
2403 again. There is some code that demonstrates how to do this in the
2404 pcre2demo sample program. In the most general case, you have to check
2405 to see if the newline convention recognizes CRLF as a newline, and if
2406 so, and the current character is CR followed by LF, advance the start‐
2407 ing offset by two characters instead of one.
2408 If a non-zero starting offset is passed when the pattern is anchored, a
2410 single attempt to match at the given offset is made. This can only suc‐
2411 ceed if the pattern does not require the match to be at the start of
2412 the subject. In other words, the anchoring must be the result of set‐
2413 ting the PCRE2_ANCHORED option or the use of .* with PCRE2_DOTALL, not
2414 by starting the pattern with ^ or \A.
2415 Option bits for pcre2_match()
2417 The unused bits of the options argument for pcre2_match() must be zero.
2419 The only bits that may be set are PCRE2_ANCHORED,
2420 PCRE2_COPY_MATCHED_SUBJECT, PCRE2_ENDANCHORED, PCRE2_NOTBOL, PCRE2_NO‐
2421 TEOL, PCRE2_NOTEMPTY, PCRE2_NOTEMPTY_ATSTART, PCRE2_NO_JIT,
2422 PCRE2_NO_UTF_CHECK, PCRE2_PARTIAL_HARD, and PCRE2_PARTIAL_SOFT. Their
2423 action is described below.
2424 Setting PCRE2_ANCHORED or PCRE2_ENDANCHORED at match time is not sup‐
2426 ported by the just-in-time (JIT) compiler. If it is set, JIT matching
2427 is disabled and the interpretive code in pcre2_match() is run. Apart
2428 from PCRE2_NO_JIT (obviously), the remaining options are supported for
2429 JIT matching.
2430 PCRE2_ANCHORED
2432 The PCRE2_ANCHORED option limits pcre2_match() to matching at the first
2434 matching position. If a pattern was compiled with PCRE2_ANCHORED, or
2435 turned out to be anchored by virtue of its contents, it cannot be made
2436 unachored at matching time. Note that setting the option at match time
2437 disables JIT matching.
2438 PCRE2_COPY_MATCHED_SUBJECT
2440 By default, a pointer to the subject is remembered in the match data
2442 block so that, after a successful match, it can be referenced by the
2443 substring extraction functions. This means that the subject's memory
2444 must not be freed until all such operations are complete. For some ap‐
2445 plications where the lifetime of the subject string is not guaranteed,
2446 it may be necessary to make a copy of the subject string, but it is
2447 wasteful to do this unless the match is successful. After a successful
2448 match, if PCRE2_COPY_MATCHED_SUBJECT is set, the subject is copied and
2449 the new pointer is remembered in the match data block instead of the
2450 original subject pointer. The memory allocator that was used for the
2451 match block itself is used. The copy is automatically freed when
2452 pcre2_match_data_free() is called to free the match data block. It is
2453 also automatically freed if the match data block is re-used for another
2454 match operation.
2455 PCRE2_ENDANCHORED
2457 If the PCRE2_ENDANCHORED option is set, any string that pcre2_match()
2459 matches must be right at the end of the subject string. Note that set‐
2460 ting the option at match time disables JIT matching.
2461 PCRE2_NOTBOL
2463 This option specifies that first character of the subject string is not
2465 the beginning of a line, so the circumflex metacharacter should not
2466 match before it. Setting this without having set PCRE2_MULTILINE at
2467 compile time causes circumflex never to match. This option affects only
2468 the behaviour of the circumflex metacharacter. It does not affect \A.
2469 PCRE2_NOTEOL
2471 This option specifies that the end of the subject string is not the end
2473 of a line, so the dollar metacharacter should not match it nor (except
2474 in multiline mode) a newline immediately before it. Setting this with‐
2475 out having set PCRE2_MULTILINE at compile time causes dollar never to
2476 match. This option affects only the behaviour of the dollar metacharac‐
2477 ter. It does not affect \Z or \z.
2478 PCRE2_NOTEMPTY
2480 An empty string is not considered to be a valid match if this option is
2482 set. If there are alternatives in the pattern, they are tried. If all
2483 the alternatives match the empty string, the entire match fails. For
2484 example, if the pattern
2485 a?b?
2487 is applied to a string not beginning with "a" or "b", it matches an
2489 empty string at the start of the subject. With PCRE2_NOTEMPTY set, this
2490 match is not valid, so pcre2_match() searches further into the string
2491 for occurrences of "a" or "b".
2492 PCRE2_NOTEMPTY_ATSTART
2494 This is like PCRE2_NOTEMPTY, except that it locks out an empty string
2496 match only at the first matching position, that is, at the start of the
2497 subject plus the starting offset. An empty string match later in the
2498 subject is permitted. If the pattern is anchored, such a match can oc‐
2499 cur only if the pattern contains \K.
2500 PCRE2_NO_JIT
2502 By default, if a pattern has been successfully processed by
2504 pcre2_jit_compile(), JIT is automatically used when pcre2_match() is
2505 called with options that JIT supports. Setting PCRE2_NO_JIT disables
2506 the use of JIT; it forces matching to be done by the interpreter.
2507 PCRE2_NO_UTF_CHECK
2509 When PCRE2_UTF is set at compile time, the validity of the subject as a
2511 UTF string is checked unless PCRE2_NO_UTF_CHECK is passed to
2512 pcre2_match() or PCRE2_MATCH_INVALID_UTF was passed to pcre2_compile().
2513 The latter special case is discussed in detail in the pcre2unicode doc‐
2514 umentation.
2515 In the default case, if a non-zero starting offset is given, the check
2517 is applied only to that part of the subject that could be inspected
2518 during matching, and there is a check that the starting offset points
2519 to the first code unit of a character or to the end of the subject. If
2520 there are no lookbehind assertions in the pattern, the check starts at
2521 the starting offset. Otherwise, it starts at the length of the longest
2522 lookbehind before the starting offset, or at the start of the subject
2523 if there are not that many characters before the starting offset. Note
2524 that the sequences \b and \B are one-character lookbehinds.
2525 The check is carried out before any other processing takes place, and a
2527 negative error code is returned if the check fails. There are several
2528 UTF error codes for each code unit width, corresponding to different
2529 problems with the code unit sequence. There are discussions about the
2530 validity of UTF-8 strings, UTF-16 strings, and UTF-32 strings in the
2531 pcre2unicode documentation.
2532 If you know that your subject is valid, and you want to skip this check
2534 for performance reasons, you can set the PCRE2_NO_UTF_CHECK option when
2535 calling pcre2_match(). You might want to do this for the second and
2536 subsequent calls to pcre2_match() if you are making repeated calls to
2537 find multiple matches in the same subject string.
2538 Warning: Unless PCRE2_MATCH_INVALID_UTF was set at compile time, when
2540 PCRE2_NO_UTF_CHECK is set at match time the effect of passing an in‐
2541 valid string as a subject, or an invalid value of startoffset, is unde‐
2542 fined. Your program may crash or loop indefinitely or give wrong re‐
2543 sults.
2544 PCRE2_PARTIAL_HARD
2546 PCRE2_PARTIAL_SOFT
2547 These options turn on the partial matching feature. A partial match oc‐
2549 curs if the end of the subject string is reached successfully, but
2550 there are not enough subject characters to complete the match. In addi‐
2551 tion, either at least one character must have been inspected or the
2552 pattern must contain a lookbehind, or the pattern must be one that
2553 could match an empty string.
2554 If this situation arises when PCRE2_PARTIAL_SOFT (but not PCRE2_PAR‐
2556 TIAL_HARD) is set, matching continues by testing any remaining alterna‐
2557 tives. Only if no complete match can be found is PCRE2_ERROR_PARTIAL
2558 returned instead of PCRE2_ERROR_NOMATCH. In other words, PCRE2_PAR‐
2559 TIAL_SOFT specifies that the caller is prepared to handle a partial
2560 match, but only if no complete match can be found.
2561 If PCRE2_PARTIAL_HARD is set, it overrides PCRE2_PARTIAL_SOFT. In this
2563 case, if a partial match is found, pcre2_match() immediately returns
2564 PCRE2_ERROR_PARTIAL, without considering any other alternatives. In
2565 other words, when PCRE2_PARTIAL_HARD is set, a partial match is consid‐
2566 ered to be more important that an alternative complete match.
2567 There is a more detailed discussion of partial and multi-segment match‐
2569 ing, with examples, in the pcre2partial documentation.
2570
2572 When PCRE2 is built, a default newline convention is set; this is usu‐
2574 ally the standard convention for the operating system. The default can
2575 be overridden in a compile context by calling pcre2_set_newline(). It
2576 can also be overridden by starting a pattern string with, for example,
2577 (*CRLF), as described in the section on newline conventions in the
2578 pcre2pattern page. During matching, the newline choice affects the be‐
2579 haviour of the dot, circumflex, and dollar metacharacters. It may also
2580 alter the way the match starting position is advanced after a match
2581 failure for an unanchored pattern.
2582 When PCRE2_NEWLINE_CRLF, PCRE2_NEWLINE_ANYCRLF, or PCRE2_NEWLINE_ANY is
2584 set as the newline convention, and a match attempt for an unanchored
2585 pattern fails when the current starting position is at a CRLF sequence,
2586 and the pattern contains no explicit matches for CR or LF characters,
2587 the match position is advanced by two characters instead of one, in
2588 other words, to after the CRLF.
2589 The above rule is a compromise that makes the most common cases work as
2591 expected. For example, if the pattern is .+A (and the PCRE2_DOTALL op‐
2592 tion is not set), it does not match the string "\r\nA" because, after
2593 failing at the start, it skips both the CR and the LF before retrying.
2594 However, the pattern [\r\n]A does match that string, because it con‐
2595 tains an explicit CR or LF reference, and so advances only by one char‐
2596 acter after the first failure.
2597 An explicit match for CR of LF is either a literal appearance of one of
2599 those characters in the pattern, or one of the \r or \n or equivalent
2600 octal or hexadecimal escape sequences. Implicit matches such as [^X] do
2601 not count, nor does \s, even though it includes CR and LF in the char‐
2602 acters that it matches.
2603 Notwithstanding the above, anomalous effects may still occur when CRLF
2605 is a valid newline sequence and explicit \r or \n escapes appear in the
2606 pattern.
2607
2609 uint32_t pcre2_get_ovector_count(pcre2_match_data *match_data);
2611 PCRE2_SIZE *pcre2_get_ovector_pointer(pcre2_match_data *match_data);
2613 In general, a pattern matches a certain portion of the subject, and in
2615 addition, further substrings from the subject may be picked out by
2616 parenthesized parts of the pattern. Following the usage in Jeffrey
2617 Friedl's book, this is called "capturing" in what follows, and the
2618 phrase "capture group" (Perl terminology) is used for a fragment of a
2619 pattern that picks out a substring. PCRE2 supports several other kinds
2620 of parenthesized group that do not cause substrings to be captured. The
2621 pcre2_pattern_info() function can be used to find out how many capture
2622 groups there are in a compiled pattern.
2623 You can use auxiliary functions for accessing captured substrings by
2625 number or by name, as described in sections below.
2626 Alternatively, you can make direct use of the vector of PCRE2_SIZE val‐
2628 ues, called the ovector, which contains the offsets of captured
2629 strings. It is part of the match data block. The function
2630 pcre2_get_ovector_pointer() returns the address of the ovector, and
2631 pcre2_get_ovector_count() returns the number of pairs of values it con‐
2632 tains.
2633 Within the ovector, the first in each pair of values is set to the off‐
2635 set of the first code unit of a substring, and the second is set to the
2636 offset of the first code unit after the end of a substring. These val‐
2637 ues are always code unit offsets, not character offsets. That is, they
2638 are byte offsets in the 8-bit library, 16-bit offsets in the 16-bit li‐
2639 brary, and 32-bit offsets in the 32-bit library.
2640 After a partial match (error return PCRE2_ERROR_PARTIAL), only the
2642 first pair of offsets (that is, ovector[0] and ovector[1]) are set.
2643 They identify the part of the subject that was partially matched. See
2644 the pcre2partial documentation for details of partial matching.
2645 After a fully successful match, the first pair of offsets identifies
2647 the portion of the subject string that was matched by the entire pat‐
2648 tern. The next pair is used for the first captured substring, and so
2649 on. The value returned by pcre2_match() is one more than the highest
2650 numbered pair that has been set. For example, if two substrings have
2651 been captured, the returned value is 3. If there are no captured sub‐
2652 strings, the return value from a successful match is 1, indicating that
2653 just the first pair of offsets has been set.
2654 If a pattern uses the \K escape sequence within a positive assertion,
2656 the reported start of a successful match can be greater than the end of
2657 the match. For example, if the pattern (?=ab\K) is matched against
2658 "ab", the start and end offset values for the match are 2 and 0.
2659 If a capture group is matched repeatedly within a single match opera‐
2661 tion, it is the last portion of the subject that it matched that is re‐
2662 turned.
2663 If the ovector is too small to hold all the captured substring offsets,
2665 as much as possible is filled in, and the function returns a value of
2666 zero. If captured substrings are not of interest, pcre2_match() may be
2667 called with a match data block whose ovector is of minimum length (that
2668 is, one pair).
2669 It is possible for capture group number n+1 to match some part of the
2671 subject when group n has not been used at all. For example, if the
2672 string "abc" is matched against the pattern (a|(z))(bc) the return from
2673 the function is 4, and groups 1 and 3 are matched, but 2 is not. When
2674 this happens, both values in the offset pairs corresponding to unused
2675 groups are set to PCRE2_UNSET.
2676 Offset values that correspond to unused groups at the end of the ex‐
2678 pression are also set to PCRE2_UNSET. For example, if the string "abc"
2679 is matched against the pattern (abc)(x(yz)?)? groups 2 and 3 are not
2680 matched. The return from the function is 2, because the highest used
2681 capture group number is 1. The offsets for for the second and third
2682 capture groupss (assuming the vector is large enough, of course) are
2683 set to PCRE2_UNSET.
2684 Elements in the ovector that do not correspond to capturing parentheses
2686 in the pattern are never changed. That is, if a pattern contains n cap‐
2687 turing parentheses, no more than ovector[0] to ovector[2n+1] are set by
2688 pcre2_match(). The other elements retain whatever values they previ‐
2689 ously had. After a failed match attempt, the contents of the ovector
2690 are unchanged.
2691
2693 PCRE2_SPTR pcre2_get_mark(pcre2_match_data *match_data);
2695 PCRE2_SIZE pcre2_get_startchar(pcre2_match_data *match_data);
2697 As well as the offsets in the ovector, other information about a match
2699 is retained in the match data block and can be retrieved by the above
2700 functions in appropriate circumstances. If they are called at other
2701 times, the result is undefined.
2702 After a successful match, a partial match (PCRE2_ERROR_PARTIAL), or a
2704 failure to match (PCRE2_ERROR_NOMATCH), a mark name may be available.
2705 The function pcre2_get_mark() can be called to access this name, which
2706 can be specified in the pattern by any of the backtracking control
2707 verbs, not just (*MARK). The same function applies to all the verbs. It
2708 returns a pointer to the zero-terminated name, which is within the com‐
2709 piled pattern. If no name is available, NULL is returned. The length of
2710 the name (excluding the terminating zero) is stored in the code unit
2711 that precedes the name. You should use this length instead of relying
2712 on the terminating zero if the name might contain a binary zero.
2713 After a successful match, the name that is returned is the last mark
2715 name encountered on the matching path through the pattern. Instances of
2716 backtracking verbs without names do not count. Thus, for example, if
2717 the matching path contains (*MARK:A)(*PRUNE), the name "A" is returned.
2718 After a "no match" or a partial match, the last encountered name is re‐
2719 turned. For example, consider this pattern:
2720 ^(*MARK:A)((*MARK:B)a|b)c
2722 When it matches "bc", the returned name is A. The B mark is "seen" in
2724 the first branch of the group, but it is not on the matching path. On
2725 the other hand, when this pattern fails to match "bx", the returned
2726 name is B.
2727 Warning: By default, certain start-of-match optimizations are used to
2729 give a fast "no match" result in some situations. For example, if the
2730 anchoring is removed from the pattern above, there is an initial check
2731 for the presence of "c" in the subject before running the matching en‐
2732 gine. This check fails for "bx", causing a match failure without seeing
2733 any marks. You can disable the start-of-match optimizations by setting
2734 the PCRE2_NO_START_OPTIMIZE option for pcre2_compile() or by starting
2735 the pattern with (*NO_START_OPT).
2736 After a successful match, a partial match, or one of the invalid UTF
2738 errors (for example, PCRE2_ERROR_UTF8_ERR5), pcre2_get_startchar() can
2739 be called. After a successful or partial match it returns the code unit
2740 offset of the character at which the match started. For a non-partial
2741 match, this can be different to the value of ovector[0] if the pattern
2742 contains the \K escape sequence. After a partial match, however, this
2743 value is always the same as ovector[0] because \K does not affect the
2744 result of a partial match.
2745 After a UTF check failure, pcre2_get_startchar() can be used to obtain
2747 the code unit offset of the invalid UTF character. Details are given in
2748 the pcre2unicode page.
2749
2751 If pcre2_match() fails, it returns a negative number. This can be con‐
2753 verted to a text string by calling the pcre2_get_error_message() func‐
2754 tion (see "Obtaining a textual error message" below). Negative error
2755 codes are also returned by other functions, and are documented with
2756 them. The codes are given names in the header file. If UTF checking is
2757 in force and an invalid UTF subject string is detected, one of a number
2758 of UTF-specific negative error codes is returned. Details are given in
2759 the pcre2unicode page. The following are the other errors that may be
2760 returned by pcre2_match():
2761 PCRE2_ERROR_NOMATCH
2763 The subject string did not match the pattern.
2765 PCRE2_ERROR_PARTIAL
2767 The subject string did not match, but it did match partially. See the
2769 pcre2partial documentation for details of partial matching.
2770 PCRE2_ERROR_BADMAGIC
2772 PCRE2 stores a 4-byte "magic number" at the start of the compiled code,
2774 to catch the case when it is passed a junk pointer. This is the error
2775 that is returned when the magic number is not present.
2776 PCRE2_ERROR_BADMODE
2778 This error is given when a compiled pattern is passed to a function in
2780 a library of a different code unit width, for example, a pattern com‐
2781 piled by the 8-bit library is passed to a 16-bit or 32-bit library
2782 function.
2783 PCRE2_ERROR_BADOFFSET
2785 The value of startoffset was greater than the length of the subject.
2787 PCRE2_ERROR_BADOPTION
2789 An unrecognized bit was set in the options argument.
2791 PCRE2_ERROR_BADUTFOFFSET
2793 The UTF code unit sequence that was passed as a subject was checked and
2795 found to be valid (the PCRE2_NO_UTF_CHECK option was not set), but the
2796 value of startoffset did not point to the beginning of a UTF character
2797 or the end of the subject.
2798 PCRE2_ERROR_CALLOUT
2800 This error is never generated by pcre2_match() itself. It is provided
2802 for use by callout functions that want to cause pcre2_match() or
2803 pcre2_callout_enumerate() to return a distinctive error code. See the
2804 pcre2callout documentation for details.
2805 PCRE2_ERROR_DEPTHLIMIT
2807 The nested backtracking depth limit was reached.
2809 PCRE2_ERROR_HEAPLIMIT
2811 The heap limit was reached.
2813 PCRE2_ERROR_INTERNAL
2815 An unexpected internal error has occurred. This error could be caused
2817 by a bug in PCRE2 or by overwriting of the compiled pattern.
2818 PCRE2_ERROR_JIT_STACKLIMIT
2820 This error is returned when a pattern that was successfully studied us‐
2822 ing JIT is being matched, but the memory available for the just-in-time
2823 processing stack is not large enough. See the pcre2jit documentation
2824 for more details.
2825 PCRE2_ERROR_MATCHLIMIT
2827 The backtracking match limit was reached.
2829 PCRE2_ERROR_NOMEMORY
2831 If a pattern contains many nested backtracking points, heap memory is
2833 used to remember them. This error is given when the memory allocation
2834 function (default or custom) fails. Note that a different error,
2835 PCRE2_ERROR_HEAPLIMIT, is given if the amount of memory needed exceeds
2836 the heap limit. PCRE2_ERROR_NOMEMORY is also returned if
2837 PCRE2_COPY_MATCHED_SUBJECT is set and memory allocation fails.
2838 PCRE2_ERROR_NULL
2840 Either the code, subject, or match_data argument was passed as NULL.
2842 PCRE2_ERROR_RECURSELOOP
2844 This error is returned when pcre2_match() detects a recursion loop
2846 within the pattern. Specifically, it means that either the whole pat‐
2847 tern or a capture group has been called recursively for the second time
2848 at the same position in the subject string. Some simple patterns that
2849 might do this are detected and faulted at compile time, but more com‐
2850 plicated cases, in particular mutual recursions between two different
2851 groups, cannot be detected until matching is attempted.
2852
2854 int pcre2_get_error_message(int errorcode, PCRE2_UCHAR *buffer,
2856 PCRE2_SIZE bufflen);
2857 A text message for an error code from any PCRE2 function (compile,
2859 match, or auxiliary) can be obtained by calling pcre2_get_error_mes‐
2860 sage(). The code is passed as the first argument, with the remaining
2861 two arguments specifying a code unit buffer and its length in code
2862 units, into which the text message is placed. The message is returned
2863 in code units of the appropriate width for the library that is being
2864 used.
2865 The returned message is terminated with a trailing zero, and the func‐
2867 tion returns the number of code units used, excluding the trailing
2868 zero. If the error number is unknown, the negative error code PCRE2_ER‐
2869 ROR_BADDATA is returned. If the buffer is too small, the message is
2870 truncated (but still with a trailing zero), and the negative error code
2871 PCRE2_ERROR_NOMEMORY is returned. None of the messages are very long;
2872 a buffer size of 120 code units is ample.
2873
2875 int pcre2_substring_length_bynumber(pcre2_match_data *match_data,
2877 uint32_t number, PCRE2_SIZE *length);
2878 int pcre2_substring_copy_bynumber(pcre2_match_data *match_data,
2880 uint32_t number, PCRE2_UCHAR *buffer,
2881 PCRE2_SIZE *bufflen);
2882 int pcre2_substring_get_bynumber(pcre2_match_data *match_data,
2884 uint32_t number, PCRE2_UCHAR **bufferptr,
2885 PCRE2_SIZE *bufflen);
2886 void pcre2_substring_free(PCRE2_UCHAR *buffer);
2888 Captured substrings can be accessed directly by using the ovector as
2890 described above. For convenience, auxiliary functions are provided for
2891 extracting captured substrings as new, separate, zero-terminated
2892 strings. A substring that contains a binary zero is correctly extracted
2893 and has a further zero added on the end, but the result is not, of
2894 course, a C string.
2895 The functions in this section identify substrings by number. The number
2897 zero refers to the entire matched substring, with higher numbers refer‐
2898 ring to substrings captured by parenthesized groups. After a partial
2899 match, only substring zero is available. An attempt to extract any
2900 other substring gives the error PCRE2_ERROR_PARTIAL. The next section
2901 describes similar functions for extracting captured substrings by name.
2902 If a pattern uses the \K escape sequence within a positive assertion,
2904 the reported start of a successful match can be greater than the end of
2905 the match. For example, if the pattern (?=ab\K) is matched against
2906 "ab", the start and end offset values for the match are 2 and 0. In
2907 this situation, calling these functions with a zero substring number
2908 extracts a zero-length empty string.
2909 You can find the length in code units of a captured substring without
2911 extracting it by calling pcre2_substring_length_bynumber(). The first
2912 argument is a pointer to the match data block, the second is the group
2913 number, and the third is a pointer to a variable into which the length
2914 is placed. If you just want to know whether or not the substring has
2915 been captured, you can pass the third argument as NULL.
2916 The pcre2_substring_copy_bynumber() function copies a captured sub‐
2918 string into a supplied buffer, whereas pcre2_substring_get_bynumber()
2919 copies it into new memory, obtained using the same memory allocation
2920 function that was used for the match data block. The first two argu‐
2921 ments of these functions are a pointer to the match data block and a
2922 capture group number.
2923 The final arguments of pcre2_substring_copy_bynumber() are a pointer to
2925 the buffer and a pointer to a variable that contains its length in code
2926 units. This is updated to contain the actual number of code units used
2927 for the extracted substring, excluding the terminating zero.
2928 For pcre2_substring_get_bynumber() the third and fourth arguments point
2930 to variables that are updated with a pointer to the new memory and the
2931 number of code units that comprise the substring, again excluding the
2932 terminating zero. When the substring is no longer needed, the memory
2933 should be freed by calling pcre2_substring_free().
2934 The return value from all these functions is zero for success, or a
2936 negative error code. If the pattern match failed, the match failure
2937 code is returned. If a substring number greater than zero is used af‐
2938 ter a partial match, PCRE2_ERROR_PARTIAL is returned. Other possible
2939 error codes are:
2940 PCRE2_ERROR_NOMEMORY
2942 The buffer was too small for pcre2_substring_copy_bynumber(), or the
2944 attempt to get memory failed for pcre2_substring_get_bynumber().
2945 PCRE2_ERROR_NOSUBSTRING
2947 There is no substring with that number in the pattern, that is, the
2949 number is greater than the number of capturing parentheses.
2950 PCRE2_ERROR_UNAVAILABLE
2952 The substring number, though not greater than the number of captures in
2954 the pattern, is greater than the number of slots in the ovector, so the
2955 substring could not be captured.
2956 PCRE2_ERROR_UNSET
2958 The substring did not participate in the match. For example, if the
2960 pattern is (abc)|(def) and the subject is "def", and the ovector con‐
2961 tains at least two capturing slots, substring number 1 is unset.
2962
2964 int pcre2_substring_list_get(pcre2_match_data *match_data,
2966 PCRE2_UCHAR ***listptr, PCRE2_SIZE **lengthsptr);
2967 void pcre2_substring_list_free(PCRE2_SPTR *list);
2969 The pcre2_substring_list_get() function extracts all available sub‐
2971 strings and builds a list of pointers to them. It also (optionally)
2972 builds a second list that contains their lengths (in code units), ex‐
2973 cluding a terminating zero that is added to each of them. All this is
2974 done in a single block of memory that is obtained using the same memory
2975 allocation function that was used to get the match data block.
2976 This function must be called only after a successful match. If called
2978 after a partial match, the error code PCRE2_ERROR_PARTIAL is returned.
2979 The address of the memory block is returned via listptr, which is also
2981 the start of the list of string pointers. The end of the list is marked
2982 by a NULL pointer. The address of the list of lengths is returned via
2983 lengthsptr. If your strings do not contain binary zeros and you do not
2984 therefore need the lengths, you may supply NULL as the lengthsptr argu‐
2985 ment to disable the creation of a list of lengths. The yield of the
2986 function is zero if all went well, or PCRE2_ERROR_NOMEMORY if the mem‐
2987 ory block could not be obtained. When the list is no longer needed, it
2988 should be freed by calling pcre2_substring_list_free().
2989 If this function encounters a substring that is unset, which can happen
2991 when capture group number n+1 matches some part of the subject, but
2992 group n has not been used at all, it returns an empty string. This can
2993 be distinguished from a genuine zero-length substring by inspecting the
2994 appropriate offset in the ovector, which contain PCRE2_UNSET for unset
2995 substrings, or by calling pcre2_substring_length_bynumber().
2996
2998 int pcre2_substring_number_from_name(const pcre2_code *code,
3000 PCRE2_SPTR name);
3001 int pcre2_substring_length_byname(pcre2_match_data *match_data,
3003 PCRE2_SPTR name, PCRE2_SIZE *length);
3004 int pcre2_substring_copy_byname(pcre2_match_data *match_data,
3006 PCRE2_SPTR name, PCRE2_UCHAR *buffer, PCRE2_SIZE *bufflen);
3007 int pcre2_substring_get_byname(pcre2_match_data *match_data,
3009 PCRE2_SPTR name, PCRE2_UCHAR **bufferptr, PCRE2_SIZE *bufflen);
3010 void pcre2_substring_free(PCRE2_UCHAR *buffer);
3012 To extract a substring by name, you first have to find associated num‐
3014 ber. For example, for this pattern:
3015 (a+)b(?<xxx>\d+)...
3017 the number of the capture group called "xxx" is 2. If the name is known
3019 to be unique (PCRE2_DUPNAMES was not set), you can find the number from
3020 the name by calling pcre2_substring_number_from_name(). The first argu‐
3021 ment is the compiled pattern, and the second is the name. The yield of
3022 the function is the group number, PCRE2_ERROR_NOSUBSTRING if there is
3023 no group with that name, or PCRE2_ERROR_NOUNIQUESUBSTRING if there is
3024 more than one group with that name. Given the number, you can extract
3025 the substring directly from the ovector, or use one of the "bynumber"
3026 functions described above.
3027 For convenience, there are also "byname" functions that correspond to
3029 the "bynumber" functions, the only difference being that the second ar‐
3030 gument is a name instead of a number. If PCRE2_DUPNAMES is set and
3031 there are duplicate names, these functions scan all the groups with the
3032 given name, and return the captured substring from the first named
3033 group that is set.
3034 If there are no groups with the given name, PCRE2_ERROR_NOSUBSTRING is
3036 returned. If all groups with the name have numbers that are greater
3037 than the number of slots in the ovector, PCRE2_ERROR_UNAVAILABLE is re‐
3038 turned. If there is at least one group with a slot in the ovector, but
3039 no group is found to be set, PCRE2_ERROR_UNSET is returned.
3040 Warning: If the pattern uses the (?| feature to set up multiple capture
3042 groups with the same number, as described in the section on duplicate
3043 group numbers in the pcre2pattern page, you cannot use names to distin‐
3044 guish the different capture groups, because names are not included in
3045 the compiled code. The matching process uses only numbers. For this
3046 reason, the use of different names for groups with the same number
3047 causes an error at compile time.
3048
3050 int pcre2_substitute(const pcre2_code *code, PCRE2_SPTR subject,
3052 PCRE2_SIZE length, PCRE2_SIZE startoffset,
3053 uint32_t options, pcre2_match_data *match_data,
3054 pcre2_match_context *mcontext, PCRE2_SPTR replacement,
3055 PCRE2_SIZE rlength, PCRE2_UCHAR *outputbuffer,
3056 PCRE2_SIZE *outlengthptr);
3057 This function optionally calls pcre2_match() and then makes a copy of
3059 the subject string in outputbuffer, replacing parts that were matched
3060 with the replacement string, whose length is supplied in rlength, which
3061 can be given as PCRE2_ZERO_TERMINATED for a zero-terminated string. As
3062 a special case, if replacement is NULL and rlength is zero, the re‐
3063 placement is assumed to be an empty string. If rlength is non-zero, an
3064 error occurs if replacement is NULL.
3065 There is an option (see PCRE2_SUBSTITUTE_REPLACEMENT_ONLY below) to re‐
3067 turn just the replacement string(s). The default action is to perform
3068 just one replacement if the pattern matches, but there is an option
3069 that requests multiple replacements (see PCRE2_SUBSTITUTE_GLOBAL be‐
3070 low).
3071 If successful, pcre2_substitute() returns the number of substitutions
3073 that were carried out. This may be zero if no match was found, and is
3074 never greater than one unless PCRE2_SUBSTITUTE_GLOBAL is set. A nega‐
3075 tive value is returned if an error is detected.
3076 Matches in which a \K item in a lookahead in the pattern causes the
3078 match to end before it starts are not supported, and give rise to an
3079 error return. For global replacements, matches in which \K in a lookbe‐
3080 hind causes the match to start earlier than the point that was reached
3081 in the previous iteration are also not supported.
3082 The first seven arguments of pcre2_substitute() are the same as for
3084 pcre2_match(), except that the partial matching options are not permit‐
3085 ted, and match_data may be passed as NULL, in which case a match data
3086 block is obtained and freed within this function, using memory manage‐
3087 ment functions from the match context, if provided, or else those that
3088 were used to allocate memory for the compiled code.
3089 If match_data is not NULL and PCRE2_SUBSTITUTE_MATCHED is not set, the
3091 provided block is used for all calls to pcre2_match(), and its contents
3092 afterwards are the result of the final call. For global changes, this
3093 will always be a no-match error. The contents of the ovector within the
3094 match data block may or may not have been changed.
3095 As well as the usual options for pcre2_match(), a number of additional
3097 options can be set in the options argument of pcre2_substitute(). One
3098 such option is PCRE2_SUBSTITUTE_MATCHED. When this is set, an external
3099 match_data block must be provided, and it must have already been used
3100 for an external call to pcre2_match() with the same pattern and subject
3101 arguments. The data in the match_data block (return code, offset vec‐
3102 tor) is then used for the first substitution instead of calling
3103 pcre2_match() from within pcre2_substitute(). This allows an applica‐
3104 tion to check for a match before choosing to substitute, without having
3105 to repeat the match.
3106 The contents of the externally supplied match data block are not
3108 changed when PCRE2_SUBSTITUTE_MATCHED is set. If PCRE2_SUBSTI‐
3109 TUTE_GLOBAL is also set, pcre2_match() is called after the first sub‐
3110 stitution to check for further matches, but this is done using an in‐
3111 ternally obtained match data block, thus always leaving the external
3112 block unchanged.
3113 The code argument is not used for matching before the first substitu‐
3115 tion when PCRE2_SUBSTITUTE_MATCHED is set, but it must be provided,
3116 even when PCRE2_SUBSTITUTE_GLOBAL is not set, because it contains in‐
3117 formation such as the UTF setting and the number of capturing parenthe‐
3118 ses in the pattern.
3119 The default action of pcre2_substitute() is to return a copy of the
3121 subject string with matched substrings replaced. However, if PCRE2_SUB‐
3122 STITUTE_REPLACEMENT_ONLY is set, only the replacement substrings are
3123 returned. In the global case, multiple replacements are concatenated in
3124 the output buffer. Substitution callouts (see below) can be used to
3125 separate them if necessary.
3126 The outlengthptr argument of pcre2_substitute() must point to a vari‐
3128 able that contains the length, in code units, of the output buffer. If
3129 the function is successful, the value is updated to contain the length
3130 in code units of the new string, excluding the trailing zero that is
3131 automatically added.
3132 If the function is not successful, the value set via outlengthptr de‐
3134 pends on the type of error. For syntax errors in the replacement
3135 string, the value is the offset in the replacement string where the er‐
3136 ror was detected. For other errors, the value is PCRE2_UNSET by de‐
3137 fault. This includes the case of the output buffer being too small, un‐
3138 less PCRE2_SUBSTITUTE_OVERFLOW_LENGTH is set.
3139 PCRE2_SUBSTITUTE_OVERFLOW_LENGTH changes what happens when the output
3141 buffer is too small. The default action is to return PCRE2_ERROR_NOMEM‐
3142 ORY immediately. If this option is set, however, pcre2_substitute()
3143 continues to go through the motions of matching and substituting (with‐
3144 out, of course, writing anything) in order to compute the size of buf‐
3145 fer that is needed. This value is passed back via the outlengthptr
3146 variable, with the result of the function still being PCRE2_ER‐
3147 ROR_NOMEMORY.
3148 Passing a buffer size of zero is a permitted way of finding out how
3150 much memory is needed for given substitution. However, this does mean
3151 that the entire operation is carried out twice. Depending on the appli‐
3152 cation, it may be more efficient to allocate a large buffer and free
3153 the excess afterwards, instead of using PCRE2_SUBSTITUTE_OVER‐
3154 FLOW_LENGTH.
3155 The replacement string, which is interpreted as a UTF string in UTF
3157 mode, is checked for UTF validity unless PCRE2_NO_UTF_CHECK is set. An
3158 invalid UTF replacement string causes an immediate return with the rel‐
3159 evant UTF error code.
3160 If PCRE2_SUBSTITUTE_LITERAL is set, the replacement string is not in‐
3162 terpreted in any way. By default, however, a dollar character is an es‐
3163 cape character that can specify the insertion of characters from cap‐
3164 ture groups and names from (*MARK) or other control verbs in the pat‐
3165 tern. The following forms are always recognized:
3166 $$ insert a dollar character
3168 $<n> or ${<n>} insert the contents of group <n>
3169 $*MARK or ${*MARK} insert a control verb name
3170 Either a group number or a group name can be given for <n>. Curly
3172 brackets are required only if the following character would be inter‐
3173 preted as part of the number or name. The number may be zero to include
3174 the entire matched string. For example, if the pattern a(b)c is
3175 matched with "=abc=" and the replacement string "+$1$0$1+", the result
3176 is "=+babcb+=".
3177 $*MARK inserts the name from the last encountered backtracking control
3179 verb on the matching path that has a name. (*MARK) must always include
3180 a name, but the other verbs need not. For example, in the case of
3181 (*MARK:A)(*PRUNE) the name inserted is "A", but for (*MARK:A)(*PRUNE:B)
3182 the relevant name is "B". This facility can be used to perform simple
3183 simultaneous substitutions, as this pcre2test example shows:
3184 /(*MARK:pear)apple|(*MARK:orange)lemon/g,replace=${*MARK}
3186 apple lemon
3187 2: pear orange
3188 PCRE2_SUBSTITUTE_GLOBAL causes the function to iterate over the subject
3190 string, replacing every matching substring. If this option is not set,
3191 only the first matching substring is replaced. The search for matches
3192 takes place in the original subject string (that is, previous replace‐
3193 ments do not affect it). Iteration is implemented by advancing the
3194 startoffset value for each search, which is always passed the entire
3195 subject string. If an offset limit is set in the match context, search‐
3196 ing stops when that limit is reached.
3197 You can restrict the effect of a global substitution to a portion of
3199 the subject string by setting either or both of startoffset and an off‐
3200 set limit. Here is a pcre2test example:
3201 /B/g,replace=!,use_offset_limit
3203 ABC ABC ABC ABC\=offset=3,offset_limit=12
3204 2: ABC A!C A!C ABC
3205 When continuing with global substitutions after matching a substring
3207 with zero length, an attempt to find a non-empty match at the same off‐
3208 set is performed. If this is not successful, the offset is advanced by
3209 one character except when CRLF is a valid newline sequence and the next
3210 two characters are CR, LF. In this case, the offset is advanced by two
3211 characters.
3212 PCRE2_SUBSTITUTE_UNKNOWN_UNSET causes references to capture groups that
3214 do not appear in the pattern to be treated as unset groups. This option
3215 should be used with care, because it means that a typo in a group name
3216 or number no longer causes the PCRE2_ERROR_NOSUBSTRING error.
3217 PCRE2_SUBSTITUTE_UNSET_EMPTY causes unset capture groups (including un‐
3219 known groups when PCRE2_SUBSTITUTE_UNKNOWN_UNSET is set) to be treated
3220 as empty strings when inserted as described above. If this option is
3221 not set, an attempt to insert an unset group causes the PCRE2_ERROR_UN‐
3222 SET error. This option does not influence the extended substitution
3223 syntax described below.
3224 PCRE2_SUBSTITUTE_EXTENDED causes extra processing to be applied to the
3226 replacement string. Without this option, only the dollar character is
3227 special, and only the group insertion forms listed above are valid.
3228 When PCRE2_SUBSTITUTE_EXTENDED is set, two things change:
3229 Firstly, backslash in a replacement string is interpreted as an escape
3231 character. The usual forms such as \n or \x{ddd} can be used to specify
3232 particular character codes, and backslash followed by any non-alphanu‐
3233 meric character quotes that character. Extended quoting can be coded
3234 using \Q...\E, exactly as in pattern strings.
3235 There are also four escape sequences for forcing the case of inserted
3237 letters. The insertion mechanism has three states: no case forcing,
3238 force upper case, and force lower case. The escape sequences change the
3239 current state: \U and \L change to upper or lower case forcing, respec‐
3240 tively, and \E (when not terminating a \Q quoted sequence) reverts to
3241 no case forcing. The sequences \u and \l force the next character (if
3242 it is a letter) to upper or lower case, respectively, and then the
3243 state automatically reverts to no case forcing. Case forcing applies to
3244 all inserted characters, including those from capture groups and let‐
3245 ters within \Q...\E quoted sequences. If either PCRE2_UTF or PCRE2_UCP
3246 was set when the pattern was compiled, Unicode properties are used for
3247 case forcing characters whose code points are greater than 127.
3248 Note that case forcing sequences such as \U...\E do not nest. For exam‐
3250 ple, the result of processing "\Uaa\LBB\Ecc\E" is "AAbbcc"; the final
3251 \E has no effect. Note also that the PCRE2_ALT_BSUX and PCRE2_EX‐
3252 TRA_ALT_BSUX options do not apply to replacement strings.
3253 The second effect of setting PCRE2_SUBSTITUTE_EXTENDED is to add more
3255 flexibility to capture group substitution. The syntax is similar to
3256 that used by Bash:
3257 ${<n>:-<string>}
3259 ${<n>:+<string1>:<string2>}
3260 As before, <n> may be a group number or a name. The first form speci‐
3262 fies a default value. If group <n> is set, its value is inserted; if
3263 not, <string> is expanded and the result inserted. The second form
3264 specifies strings that are expanded and inserted when group <n> is set
3265 or unset, respectively. The first form is just a convenient shorthand
3266 for
3267 ${<n>:+${<n>}:<string>}
3269 Backslash can be used to escape colons and closing curly brackets in
3271 the replacement strings. A change of the case forcing state within a
3272 replacement string remains in force afterwards, as shown in this
3273 pcre2test example:
3274 /(some)?(body)/substitute_extended,replace=${1:+\U:\L}HeLLo
3276 body
3277 1: hello
3278 somebody
3279 1: HELLO
3280 The PCRE2_SUBSTITUTE_UNSET_EMPTY option does not affect these extended
3282 substitutions. However, PCRE2_SUBSTITUTE_UNKNOWN_UNSET does cause un‐
3283 known groups in the extended syntax forms to be treated as unset.
3284 If PCRE2_SUBSTITUTE_LITERAL is set, PCRE2_SUBSTITUTE_UNKNOWN_UNSET,
3286 PCRE2_SUBSTITUTE_UNSET_EMPTY, and PCRE2_SUBSTITUTE_EXTENDED are irrele‐
3287 vant and are ignored.
3288 Substitution errors
3290 In the event of an error, pcre2_substitute() returns a negative error
3292 code. Except for PCRE2_ERROR_NOMATCH (which is never returned), errors
3293 from pcre2_match() are passed straight back.
3294 PCRE2_ERROR_NOSUBSTRING is returned for a non-existent substring inser‐
3296 tion, unless PCRE2_SUBSTITUTE_UNKNOWN_UNSET is set.
3297 PCRE2_ERROR_UNSET is returned for an unset substring insertion (includ‐
3299 ing an unknown substring when PCRE2_SUBSTITUTE_UNKNOWN_UNSET is set)
3300 when the simple (non-extended) syntax is used and PCRE2_SUBSTITUTE_UN‐
3301 SET_EMPTY is not set.
3302 PCRE2_ERROR_NOMEMORY is returned if the output buffer is not big
3304 enough. If the PCRE2_SUBSTITUTE_OVERFLOW_LENGTH option is set, the size
3305 of buffer that is needed is returned via outlengthptr. Note that this
3306 does not happen by default.
3307 PCRE2_ERROR_NULL is returned if PCRE2_SUBSTITUTE_MATCHED is set but the
3309 match_data argument is NULL or if the subject or replacement arguments
3310 are NULL. For backward compatibility reasons an exception is made for
3311 the replacement argument if the rlength argument is also 0.
3312 PCRE2_ERROR_BADREPLACEMENT is used for miscellaneous syntax errors in
3314 the replacement string, with more particular errors being PCRE2_ER‐
3315 ROR_BADREPESCAPE (invalid escape sequence), PCRE2_ERROR_REPMISSINGBRACE
3316 (closing curly bracket not found), PCRE2_ERROR_BADSUBSTITUTION (syntax
3317 error in extended group substitution), and PCRE2_ERROR_BADSUBSPATTERN
3318 (the pattern match ended before it started or the match started earlier
3319 than the current position in the subject, which can happen if \K is
3320 used in an assertion).
3321 As for all PCRE2 errors, a text message that describes the error can be
3323 obtained by calling the pcre2_get_error_message() function (see "Ob‐
3324 taining a textual error message" above).
3325 Substitution callouts
3327 int pcre2_set_substitute_callout(pcre2_match_context *mcontext,
3329 int (*callout_function)(pcre2_substitute_callout_block *, void *),
3330 void *callout_data);
3331 The pcre2_set_substitution_callout() function can be used to specify a
3333 callout function for pcre2_substitute(). This information is passed in
3334 a match context. The callout function is called after each substitution
3335 has been processed, but it can cause the replacement not to happen. The
3336 callout function is not called for simulated substitutions that happen
3337 as a result of the PCRE2_SUBSTITUTE_OVERFLOW_LENGTH option.
3338 The first argument of the callout function is a pointer to a substitute
3340 callout block structure, which contains the following fields, not nec‐
3341 essarily in this order:
3342 uint32_t version;
3344 uint32_t subscount;
3345 PCRE2_SPTR input;
3346 PCRE2_SPTR output;
3347 PCRE2_SIZE *ovector;
3348 uint32_t oveccount;
3349 PCRE2_SIZE output_offsets[2];
3350 The version field contains the version number of the block format. The
3352 current version is 0. The version number will increase in future if
3353 more fields are added, but the intention is never to remove any of the
3354 existing fields.
3355 The subscount field is the number of the current match. It is 1 for the
3357 first callout, 2 for the second, and so on. The input and output point‐
3358 ers are copies of the values passed to pcre2_substitute().
3359 The ovector field points to the ovector, which contains the result of
3361 the most recent match. The oveccount field contains the number of pairs
3362 that are set in the ovector, and is always greater than zero.
3363 The output_offsets vector contains the offsets of the replacement in
3365 the output string. This has already been processed for dollar and (if
3366 requested) backslash substitutions as described above.
3367 The second argument of the callout function is the value passed as
3369 callout_data when the function was registered. The value returned by
3370 the callout function is interpreted as follows:
3371 If the value is zero, the replacement is accepted, and, if PCRE2_SUB‐
3373 STITUTE_GLOBAL is set, processing continues with a search for the next
3374 match. If the value is not zero, the current replacement is not ac‐
3375 cepted. If the value is greater than zero, processing continues when
3376 PCRE2_SUBSTITUTE_GLOBAL is set. Otherwise (the value is less than zero
3377 or PCRE2_SUBSTITUTE_GLOBAL is not set), the the rest of the input is
3378 copied to the output and the call to pcre2_substitute() exits, return‐
3379 ing the number of matches so far.
3380
3382 int pcre2_substring_nametable_scan(const pcre2_code *code,
3384 PCRE2_SPTR name, PCRE2_SPTR *first, PCRE2_SPTR *last);
3385 When a pattern is compiled with the PCRE2_DUPNAMES option, names for
3387 capture groups are not required to be unique. Duplicate names are al‐
3388 ways allowed for groups with the same number, created by using the (?|
3389 feature. Indeed, if such groups are named, they are required to use the
3390 same names.
3391 Normally, patterns that use duplicate names are such that in any one
3393 match, only one of each set of identically-named groups participates.
3394 An example is shown in the pcre2pattern documentation.
3395 When duplicates are present, pcre2_substring_copy_byname() and
3397 pcre2_substring_get_byname() return the first substring corresponding
3398 to the given name that is set. Only if none are set is PCRE2_ERROR_UN‐
3399 SET is returned. The pcre2_substring_number_from_name() function re‐
3400 turns the error PCRE2_ERROR_NOUNIQUESUBSTRING when there are duplicate
3401 names.
3402 If you want to get full details of all captured substrings for a given
3404 name, you must use the pcre2_substring_nametable_scan() function. The
3405 first argument is the compiled pattern, and the second is the name. If
3406 the third and fourth arguments are NULL, the function returns a group
3407 number for a unique name, or PCRE2_ERROR_NOUNIQUESUBSTRING otherwise.
3408 When the third and fourth arguments are not NULL, they must be pointers
3410 to variables that are updated by the function. After it has run, they
3411 point to the first and last entries in the name-to-number table for the
3412 given name, and the function returns the length of each entry in code
3413 units. In both cases, PCRE2_ERROR_NOSUBSTRING is returned if there are
3414 no entries for the given name.
3415 The format of the name table is described above in the section entitled
3417 Information about a pattern. Given all the relevant entries for the
3418 name, you can extract each of their numbers, and hence the captured
3419 data.
3420
3422 The traditional matching function uses a similar algorithm to Perl,
3424 which stops when it finds the first match at a given point in the sub‐
3425 ject. If you want to find all possible matches, or the longest possible
3426 match at a given position, consider using the alternative matching
3427 function (see below) instead. If you cannot use the alternative func‐
3428 tion, you can kludge it up by making use of the callout facility, which
3429 is described in the pcre2callout documentation.
3430 What you have to do is to insert a callout right at the end of the pat‐
3432 tern. When your callout function is called, extract and save the cur‐
3433 rent matched substring. Then return 1, which forces pcre2_match() to
3434 backtrack and try other alternatives. Ultimately, when it runs out of
3435 matches, pcre2_match() will yield PCRE2_ERROR_NOMATCH.
3436
3438 int pcre2_dfa_match(const pcre2_code *code, PCRE2_SPTR subject,
3440 PCRE2_SIZE length, PCRE2_SIZE startoffset,
3441 uint32_t options, pcre2_match_data *match_data,
3442 pcre2_match_context *mcontext,
3443 int *workspace, PCRE2_SIZE wscount);
3444 The function pcre2_dfa_match() is called to match a subject string
3446 against a compiled pattern, using a matching algorithm that scans the
3447 subject string just once (not counting lookaround assertions), and does
3448 not backtrack (except when processing lookaround assertions). This has
3449 different characteristics to the normal algorithm, and is not compati‐
3450 ble with Perl. Some of the features of PCRE2 patterns are not sup‐
3451 ported. Nevertheless, there are times when this kind of matching can be
3452 useful. For a discussion of the two matching algorithms, and a list of
3453 features that pcre2_dfa_match() does not support, see the pcre2matching
3454 documentation.
3455 The arguments for the pcre2_dfa_match() function are the same as for
3457 pcre2_match(), plus two extras. The ovector within the match data block
3458 is used in a different way, and this is described below. The other com‐
3459 mon arguments are used in the same way as for pcre2_match(), so their
3460 description is not repeated here.
3461 The two additional arguments provide workspace for the function. The
3463 workspace vector should contain at least 20 elements. It is used for
3464 keeping track of multiple paths through the pattern tree. More
3465 workspace is needed for patterns and subjects where there are a lot of
3466 potential matches.
3467 Here is an example of a simple call to pcre2_dfa_match():
3469 int wspace[20];
3471 pcre2_match_data *md = pcre2_match_data_create(4, NULL);
3472 int rc = pcre2_dfa_match(
3473 re, /* result of pcre2_compile() */
3474 "some string", /* the subject string */
3475 11, /* the length of the subject string */
3476 0, /* start at offset 0 in the subject */
3477 0, /* default options */
3478 md, /* the match data block */
3479 NULL, /* a match context; NULL means use defaults */
3480 wspace, /* working space vector */
3481 20); /* number of elements (NOT size in bytes) */
3482 Option bits for pcre2_dfa_match()
3484 The unused bits of the options argument for pcre2_dfa_match() must be
3486 zero. The only bits that may be set are PCRE2_ANCHORED,
3487 PCRE2_COPY_MATCHED_SUBJECT, PCRE2_ENDANCHORED, PCRE2_NOTBOL, PCRE2_NO‐
3488 TEOL, PCRE2_NOTEMPTY, PCRE2_NOTEMPTY_ATSTART, PCRE2_NO_UTF_CHECK,
3489 PCRE2_PARTIAL_HARD, PCRE2_PARTIAL_SOFT, PCRE2_DFA_SHORTEST, and
3490 PCRE2_DFA_RESTART. All but the last four of these are exactly the same
3491 as for pcre2_match(), so their description is not repeated here.
3492 PCRE2_PARTIAL_HARD
3494 PCRE2_PARTIAL_SOFT
3495 These have the same general effect as they do for pcre2_match(), but
3497 the details are slightly different. When PCRE2_PARTIAL_HARD is set for
3498 pcre2_dfa_match(), it returns PCRE2_ERROR_PARTIAL if the end of the
3499 subject is reached and there is still at least one matching possibility
3500 that requires additional characters. This happens even if some complete
3501 matches have already been found. When PCRE2_PARTIAL_SOFT is set, the
3502 return code PCRE2_ERROR_NOMATCH is converted into PCRE2_ERROR_PARTIAL
3503 if the end of the subject is reached, there have been no complete
3504 matches, but there is still at least one matching possibility. The por‐
3505 tion of the string that was inspected when the longest partial match
3506 was found is set as the first matching string in both cases. There is a
3507 more detailed discussion of partial and multi-segment matching, with
3508 examples, in the pcre2partial documentation.
3509 PCRE2_DFA_SHORTEST
3511 Setting the PCRE2_DFA_SHORTEST option causes the matching algorithm to
3513 stop as soon as it has found one match. Because of the way the alterna‐
3514 tive algorithm works, this is necessarily the shortest possible match
3515 at the first possible matching point in the subject string.
3516 PCRE2_DFA_RESTART
3518 When pcre2_dfa_match() returns a partial match, it is possible to call
3520 it again, with additional subject characters, and have it continue with
3521 the same match. The PCRE2_DFA_RESTART option requests this action; when
3522 it is set, the workspace and wscount options must reference the same
3523 vector as before because data about the match so far is left in them
3524 after a partial match. There is more discussion of this facility in the
3525 pcre2partial documentation.
3526 Successful returns from pcre2_dfa_match()
3528 When pcre2_dfa_match() succeeds, it may have matched more than one sub‐
3530 string in the subject. Note, however, that all the matches from one run
3531 of the function start at the same point in the subject. The shorter
3532 matches are all initial substrings of the longer matches. For example,
3533 if the pattern
3534 <.*>
3536 is matched against the string
3538 This is <something> <something else> <something further> no more
3540 the three matched strings are
3542 <something> <something else> <something further>
3544 <something> <something else>
3545 <something>
3546 On success, the yield of the function is a number greater than zero,
3548 which is the number of matched substrings. The offsets of the sub‐
3549 strings are returned in the ovector, and can be extracted by number in
3550 the same way as for pcre2_match(), but the numbers bear no relation to
3551 any capture groups that may exist in the pattern, because DFA matching
3552 does not support capturing.
3553 Calls to the convenience functions that extract substrings by name re‐
3555 turn the error PCRE2_ERROR_DFA_UFUNC (unsupported function) if used af‐
3556 ter a DFA match. The convenience functions that extract substrings by
3557 number never return PCRE2_ERROR_NOSUBSTRING.
3558 The matched strings are stored in the ovector in reverse order of
3560 length; that is, the longest matching string is first. If there were
3561 too many matches to fit into the ovector, the yield of the function is
3562 zero, and the vector is filled with the longest matches.
3563 NOTE: PCRE2's "auto-possessification" optimization usually applies to
3565 character repeats at the end of a pattern (as well as internally). For
3566 example, the pattern "a\d+" is compiled as if it were "a\d++". For DFA
3567 matching, this means that only one possible match is found. If you re‐
3568 ally do want multiple matches in such cases, either use an ungreedy re‐
3569 peat such as "a\d+?" or set the PCRE2_NO_AUTO_POSSESS option when com‐
3570 piling.
3571 Error returns from pcre2_dfa_match()
3573 The pcre2_dfa_match() function returns a negative number when it fails.
3575 Many of the errors are the same as for pcre2_match(), as described
3576 above. There are in addition the following errors that are specific to
3577 pcre2_dfa_match():
3578 PCRE2_ERROR_DFA_UITEM
3580 This return is given if pcre2_dfa_match() encounters an item in the
3582 pattern that it does not support, for instance, the use of \C in a UTF
3583 mode or a backreference.
3584 PCRE2_ERROR_DFA_UCOND
3586 This return is given if pcre2_dfa_match() encounters a condition item
3588 that uses a backreference for the condition, or a test for recursion in
3589 a specific capture group. These are not supported.
3590 PCRE2_ERROR_DFA_UINVALID_UTF
3592 This return is given if pcre2_dfa_match() is called for a pattern that
3594 was compiled with PCRE2_MATCH_INVALID_UTF. This is not supported for
3595 DFA matching.
3596 PCRE2_ERROR_DFA_WSSIZE
3598 This return is given if pcre2_dfa_match() runs out of space in the
3600 workspace vector.
3601 PCRE2_ERROR_DFA_RECURSE
3603 When a recursion or subroutine call is processed, the matching function
3605 calls itself recursively, using private memory for the ovector and
3606 workspace. This error is given if the internal ovector is not large
3607 enough. This should be extremely rare, as a vector of size 1000 is
3608 used.
3609 PCRE2_ERROR_DFA_BADRESTART
3611 When pcre2_dfa_match() is called with the PCRE2_DFA_RESTART option,
3613 some plausibility checks are made on the contents of the workspace,
3614 which should contain data about the previous partial match. If any of
3615 these checks fail, this error is given.
3616
3618 pcre2build(3), pcre2callout(3), pcre2demo(3), pcre2matching(3),
3620 pcre2partial(3), pcre2posix(3), pcre2sample(3), pcre2unicode(3).
3621
3623 Philip Hazel
3625 Retired from University Computing Service
3626 Cambridge, England.
3627
3629 Last updated: 14 December 2021
3631 Copyright (c) 1997-2021 University of Cambridge.
3632PCRE2 10.40 14 December 2021 PCRE2API(3)