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1 nigel 79 .TH PCREAPI 3
2 nigel 63 .SH NAME
3     PCRE - Perl-compatible regular expressions
4 ph10 856 .sp
5     .B #include <pcre.h>
6     .
7     .
8 ph10 678 .SH "PCRE NATIVE API BASIC FUNCTIONS"
9 nigel 63 .rs
10     .sp
11     .SM
12 nigel 75 .B pcre *pcre_compile(const char *\fIpattern\fP, int \fIoptions\fP,
13 nigel 63 .ti +5n
14 nigel 75 .B const char **\fIerrptr\fP, int *\fIerroffset\fP,
15 nigel 63 .ti +5n
16 nigel 75 .B const unsigned char *\fItableptr\fP);
17 nigel 63 .PP
18 nigel 77 .B pcre *pcre_compile2(const char *\fIpattern\fP, int \fIoptions\fP,
19     .ti +5n
20     .B int *\fIerrorcodeptr\fP,
21     .ti +5n
22     .B const char **\fIerrptr\fP, int *\fIerroffset\fP,
23     .ti +5n
24     .B const unsigned char *\fItableptr\fP);
25     .PP
26 nigel 75 .B pcre_extra *pcre_study(const pcre *\fIcode\fP, int \fIoptions\fP,
27 nigel 63 .ti +5n
28 nigel 75 .B const char **\fIerrptr\fP);
29 nigel 63 .PP
30 ph10 678 .B void pcre_free_study(pcre_extra *\fIextra\fP);
31     .PP
32 nigel 75 .B int pcre_exec(const pcre *\fIcode\fP, "const pcre_extra *\fIextra\fP,"
33 nigel 63 .ti +5n
34 nigel 75 .B "const char *\fIsubject\fP," int \fIlength\fP, int \fIstartoffset\fP,
35 nigel 63 .ti +5n
36 nigel 75 .B int \fIoptions\fP, int *\fIovector\fP, int \fIovecsize\fP);
37 nigel 63 .PP
38 nigel 77 .B int pcre_dfa_exec(const pcre *\fIcode\fP, "const pcre_extra *\fIextra\fP,"
39     .ti +5n
40     .B "const char *\fIsubject\fP," int \fIlength\fP, int \fIstartoffset\fP,
41     .ti +5n
42     .B int \fIoptions\fP, int *\fIovector\fP, int \fIovecsize\fP,
43     .ti +5n
44     .B int *\fIworkspace\fP, int \fIwscount\fP);
45 ph10 856 .
46     .
47     .SH "PCRE NATIVE API STRING EXTRACTION FUNCTIONS"
48     .rs
49     .sp
50 nigel 75 .B int pcre_copy_named_substring(const pcre *\fIcode\fP,
51 nigel 63 .ti +5n
52 nigel 75 .B const char *\fIsubject\fP, int *\fIovector\fP,
53 nigel 63 .ti +5n
54 nigel 75 .B int \fIstringcount\fP, const char *\fIstringname\fP,
55 nigel 63 .ti +5n
56 nigel 75 .B char *\fIbuffer\fP, int \fIbuffersize\fP);
57 nigel 63 .PP
58 nigel 75 .B int pcre_copy_substring(const char *\fIsubject\fP, int *\fIovector\fP,
59 nigel 63 .ti +5n
60 nigel 75 .B int \fIstringcount\fP, int \fIstringnumber\fP, char *\fIbuffer\fP,
61 nigel 63 .ti +5n
62 nigel 75 .B int \fIbuffersize\fP);
63 nigel 63 .PP
64 nigel 75 .B int pcre_get_named_substring(const pcre *\fIcode\fP,
65 nigel 63 .ti +5n
66 nigel 75 .B const char *\fIsubject\fP, int *\fIovector\fP,
67 nigel 63 .ti +5n
68 nigel 75 .B int \fIstringcount\fP, const char *\fIstringname\fP,
69 nigel 63 .ti +5n
70 nigel 75 .B const char **\fIstringptr\fP);
71 nigel 63 .PP
72 nigel 75 .B int pcre_get_stringnumber(const pcre *\fIcode\fP,
73 nigel 63 .ti +5n
74 nigel 75 .B const char *\fIname\fP);
75 nigel 63 .PP
76 nigel 91 .B int pcre_get_stringtable_entries(const pcre *\fIcode\fP,
77     .ti +5n
78     .B const char *\fIname\fP, char **\fIfirst\fP, char **\fIlast\fP);
79     .PP
80 nigel 75 .B int pcre_get_substring(const char *\fIsubject\fP, int *\fIovector\fP,
81 nigel 63 .ti +5n
82 nigel 75 .B int \fIstringcount\fP, int \fIstringnumber\fP,
83 nigel 63 .ti +5n
84 nigel 75 .B const char **\fIstringptr\fP);
85 nigel 63 .PP
86 nigel 75 .B int pcre_get_substring_list(const char *\fIsubject\fP,
87 nigel 63 .ti +5n
88 nigel 75 .B int *\fIovector\fP, int \fIstringcount\fP, "const char ***\fIlistptr\fP);"
89 nigel 63 .PP
90 nigel 75 .B void pcre_free_substring(const char *\fIstringptr\fP);
91 nigel 63 .PP
92 nigel 75 .B void pcre_free_substring_list(const char **\fIstringptr\fP);
93 ph10 856 .
94     .
95     .SH "PCRE NATIVE API AUXILIARY FUNCTIONS"
96     .rs
97     .sp
98     .B pcre_jit_stack *pcre_jit_stack_alloc(int \fIstartsize\fP, int \fImaxsize\fP);
99 nigel 63 .PP
100 ph10 856 .B void pcre_jit_stack_free(pcre_jit_stack *\fIstack\fP);
101     .PP
102     .B void pcre_assign_jit_stack(pcre_extra *\fIextra\fP,
103     .ti +5n
104     .B pcre_jit_callback \fIcallback\fP, void *\fIdata\fP);
105     .PP
106 nigel 63 .B const unsigned char *pcre_maketables(void);
107     .PP
108 nigel 75 .B int pcre_fullinfo(const pcre *\fIcode\fP, "const pcre_extra *\fIextra\fP,"
109 nigel 63 .ti +5n
110 nigel 75 .B int \fIwhat\fP, void *\fIwhere\fP);
111 nigel 63 .PP
112 nigel 77 .B int pcre_refcount(pcre *\fIcode\fP, int \fIadjust\fP);
113     .PP
114 nigel 75 .B int pcre_config(int \fIwhat\fP, void *\fIwhere\fP);
115 nigel 63 .PP
116 ph10 856 .B const char *pcre_version(void);
117     .PP
118     .B int pcre_pattern_to_host_byte_order(pcre *\fIcode\fP,
119     .ti +5n
120     .B pcre_extra *\fIextra\fP, const unsigned char *\fItables\fP);
121 ph10 686 .
122     .
123     .SH "PCRE NATIVE API INDIRECTED FUNCTIONS"
124     .rs
125     .sp
126 nigel 63 .B void *(*pcre_malloc)(size_t);
127     .PP
128     .B void (*pcre_free)(void *);
129     .PP
130 nigel 73 .B void *(*pcre_stack_malloc)(size_t);
131     .PP
132     .B void (*pcre_stack_free)(void *);
133     .PP
134 nigel 63 .B int (*pcre_callout)(pcre_callout_block *);
135 nigel 75 .
136     .
137 ph10 856 .SH "PCRE 8-BIT AND 16-BIT LIBRARIES"
138     .rs
139     .sp
140     From release 8.30, PCRE can be compiled as a library for handling 16-bit
141     character strings as well as, or instead of, the original library that handles
142     8-bit character strings. To avoid too much complication, this document
143     describes the 8-bit versions of the functions, with only occasional references
144     to the 16-bit library.
145     .P
146     The 16-bit functions operate in the same way as their 8-bit counterparts; they
147     just use different data types for their arguments and results, and their names
148     start with \fBpcre16_\fP instead of \fBpcre_\fP. For every option that has UTF8
149     in its name (for example, PCRE_UTF8), there is a corresponding 16-bit name with
150     UTF8 replaced by UTF16. This facility is in fact just cosmetic; the 16-bit
151 ph10 903 option names define the same bit values.
152 ph10 856 .P
153     References to bytes and UTF-8 in this document should be read as references to
154     16-bit data quantities and UTF-16 when using the 16-bit library, unless
155     specified otherwise. More details of the specific differences for the 16-bit
156     library are given in the
157     .\" HREF
158     \fBpcre16\fP
159     .\"
160 ph10 903 page.
161 ph10 856 .
162     .
163 nigel 75 .SH "PCRE API OVERVIEW"
164 nigel 63 .rs
165     .sp
166 nigel 93 PCRE has its own native API, which is described in this document. There are
167 ph10 856 also some wrapper functions (for the 8-bit library only) that correspond to the
168     POSIX regular expression API, but they do not give access to all the
169     functionality. They are described in the
170 nigel 75 .\" HREF
171     \fBpcreposix\fP
172     .\"
173 nigel 77 documentation. Both of these APIs define a set of C function calls. A C++
174 ph10 856 wrapper (again for the 8-bit library only) is also distributed with PCRE. It is
175     documented in the
176 nigel 77 .\" HREF
177     \fBpcrecpp\fP
178     .\"
179     page.
180 nigel 75 .P
181 nigel 77 The native API C function prototypes are defined in the header file
182 ph10 856 \fBpcre.h\fP, and on Unix-like systems the (8-bit) library itself is called
183     \fBlibpcre\fP. It can normally be accessed by adding \fB-lpcre\fP to the
184     command for linking an application that uses PCRE. The header file defines the
185     macros PCRE_MAJOR and PCRE_MINOR to contain the major and minor release numbers
186     for the library. Applications can use these to include support for different
187     releases of PCRE.
188 nigel 75 .P
189 ph10 525 In a Windows environment, if you want to statically link an application program
190     against a non-dll \fBpcre.a\fP file, you must define PCRE_STATIC before
191 ph10 526 including \fBpcre.h\fP or \fBpcrecpp.h\fP, because otherwise the
192     \fBpcre_malloc()\fP and \fBpcre_free()\fP exported functions will be declared
193 ph10 525 \fB__declspec(dllimport)\fP, with unwanted results.
194     .P
195 nigel 77 The functions \fBpcre_compile()\fP, \fBpcre_compile2()\fP, \fBpcre_study()\fP,
196     and \fBpcre_exec()\fP are used for compiling and matching regular expressions
197     in a Perl-compatible manner. A sample program that demonstrates the simplest
198 ph10 429 way of using them is provided in the file called \fIpcredemo.c\fP in the PCRE
199     source distribution. A listing of this program is given in the
200 nigel 75 .\" HREF
201 ph10 429 \fBpcredemo\fP
202     .\"
203     documentation, and the
204     .\" HREF
205 nigel 75 \fBpcresample\fP
206     .\"
207 ph10 312 documentation describes how to compile and run it.
208 nigel 75 .P
209 ph10 678 Just-in-time compiler support is an optional feature of PCRE that can be built
210 ph10 686 in appropriate hardware environments. It greatly speeds up the matching
211     performance of many patterns. Simple programs can easily request that it be
212     used if available, by setting an option that is ignored when it is not
213     relevant. More complicated programs might need to make use of the functions
214     \fBpcre_jit_stack_alloc()\fP, \fBpcre_jit_stack_free()\fP, and
215     \fBpcre_assign_jit_stack()\fP in order to control the JIT code's memory usage.
216 ph10 678 These functions are discussed in the
217     .\" HREF
218     \fBpcrejit\fP
219     .\"
220     documentation.
221     .P
222 nigel 77 A second matching function, \fBpcre_dfa_exec()\fP, which is not
223     Perl-compatible, is also provided. This uses a different algorithm for the
224 nigel 91 matching. The alternative algorithm finds all possible matches (at a given
225 ph10 435 point in the subject), and scans the subject just once (unless there are
226     lookbehind assertions). However, this algorithm does not return captured
227     substrings. A description of the two matching algorithms and their advantages
228     and disadvantages is given in the
229 nigel 77 .\" HREF
230     \fBpcrematching\fP
231     .\"
232     documentation.
233     .P
234 nigel 75 In addition to the main compiling and matching functions, there are convenience
235 nigel 77 functions for extracting captured substrings from a subject string that is
236     matched by \fBpcre_exec()\fP. They are:
237 nigel 75 .sp
238     \fBpcre_copy_substring()\fP
239     \fBpcre_copy_named_substring()\fP
240     \fBpcre_get_substring()\fP
241     \fBpcre_get_named_substring()\fP
242     \fBpcre_get_substring_list()\fP
243     \fBpcre_get_stringnumber()\fP
244 nigel 91 \fBpcre_get_stringtable_entries()\fP
245 nigel 75 .sp
246     \fBpcre_free_substring()\fP and \fBpcre_free_substring_list()\fP are also
247 nigel 63 provided, to free the memory used for extracted strings.
248 nigel 75 .P
249     The function \fBpcre_maketables()\fP is used to build a set of character tables
250 nigel 77 in the current locale for passing to \fBpcre_compile()\fP, \fBpcre_exec()\fP,
251     or \fBpcre_dfa_exec()\fP. This is an optional facility that is provided for
252     specialist use. Most commonly, no special tables are passed, in which case
253     internal tables that are generated when PCRE is built are used.
254 nigel 75 .P
255     The function \fBpcre_fullinfo()\fP is used to find out information about a
256 ph10 856 compiled pattern. The function \fBpcre_version()\fP returns a pointer to a
257     string containing the version of PCRE and its date of release.
258 nigel 75 .P
259 nigel 77 The function \fBpcre_refcount()\fP maintains a reference count in a data block
260     containing a compiled pattern. This is provided for the benefit of
261     object-oriented applications.
262     .P
263 nigel 75 The global variables \fBpcre_malloc\fP and \fBpcre_free\fP initially contain
264     the entry points of the standard \fBmalloc()\fP and \fBfree()\fP functions,
265 nigel 63 respectively. PCRE calls the memory management functions via these variables,
266     so a calling program can replace them if it wishes to intercept the calls. This
267     should be done before calling any PCRE functions.
268 nigel 75 .P
269     The global variables \fBpcre_stack_malloc\fP and \fBpcre_stack_free\fP are also
270 nigel 73 indirections to memory management functions. These special functions are used
271     only when PCRE is compiled to use the heap for remembering data, instead of
272 nigel 91 recursive function calls, when running the \fBpcre_exec()\fP function. See the
273     .\" HREF
274     \fBpcrebuild\fP
275     .\"
276     documentation for details of how to do this. It is a non-standard way of
277     building PCRE, for use in environments that have limited stacks. Because of the
278     greater use of memory management, it runs more slowly. Separate functions are
279     provided so that special-purpose external code can be used for this case. When
280     used, these functions are always called in a stack-like manner (last obtained,
281     first freed), and always for memory blocks of the same size. There is a
282     discussion about PCRE's stack usage in the
283     .\" HREF
284     \fBpcrestack\fP
285     .\"
286     documentation.
287 nigel 75 .P
288     The global variable \fBpcre_callout\fP initially contains NULL. It can be set
289 nigel 63 by the caller to a "callout" function, which PCRE will then call at specified
290 nigel 75 points during a matching operation. Details are given in the
291     .\" HREF
292     \fBpcrecallout\fP
293     .\"
294 nigel 63 documentation.
295 nigel 75 .
296     .
297 ph10 227 .\" HTML <a name="newlines"></a>
298 nigel 91 .SH NEWLINES
299 nigel 93 .rs
300 nigel 91 .sp
301 ph10 149 PCRE supports five different conventions for indicating line breaks in
302 nigel 93 strings: a single CR (carriage return) character, a single LF (linefeed)
303 ph10 149 character, the two-character sequence CRLF, any of the three preceding, or any
304     Unicode newline sequence. The Unicode newline sequences are the three just
305     mentioned, plus the single characters VT (vertical tab, U+000B), FF (formfeed,
306     U+000C), NEL (next line, U+0085), LS (line separator, U+2028), and PS
307     (paragraph separator, U+2029).
308 nigel 93 .P
309     Each of the first three conventions is used by at least one operating system as
310     its standard newline sequence. When PCRE is built, a default can be specified.
311     The default default is LF, which is the Unix standard. When PCRE is run, the
312     default can be overridden, either when a pattern is compiled, or when it is
313     matched.
314     .P
315 ph10 227 At compile time, the newline convention can be specified by the \fIoptions\fP
316     argument of \fBpcre_compile()\fP, or it can be specified by special text at the
317     start of the pattern itself; this overrides any other settings. See the
318     .\" HREF
319     \fBpcrepattern\fP
320     .\"
321     page for details of the special character sequences.
322     .P
323 nigel 91 In the PCRE documentation the word "newline" is used to mean "the character or
324 nigel 93 pair of characters that indicate a line break". The choice of newline
325     convention affects the handling of the dot, circumflex, and dollar
326     metacharacters, the handling of #-comments in /x mode, and, when CRLF is a
327     recognized line ending sequence, the match position advancement for a
328 ph10 226 non-anchored pattern. There is more detail about this in the
329     .\" HTML <a href="#execoptions">
330     .\" </a>
331     section on \fBpcre_exec()\fP options
332     .\"
333 ph10 231 below.
334     .P
335     The choice of newline convention does not affect the interpretation of
336     the \en or \er escape sequences, nor does it affect what \eR matches, which is
337     controlled in a similar way, but by separate options.
338 nigel 91 .
339     .
340 nigel 63 .SH MULTITHREADING
341     .rs
342     .sp
343     The PCRE functions can be used in multi-threading applications, with the
344 nigel 75 proviso that the memory management functions pointed to by \fBpcre_malloc\fP,
345     \fBpcre_free\fP, \fBpcre_stack_malloc\fP, and \fBpcre_stack_free\fP, and the
346     callout function pointed to by \fBpcre_callout\fP, are shared by all threads.
347     .P
348 nigel 63 The compiled form of a regular expression is not altered during matching, so
349     the same compiled pattern can safely be used by several threads at once.
350 ph10 678 .P
351 ph10 691 If the just-in-time optimization feature is being used, it needs separate
352 ph10 678 memory stack areas for each thread. See the
353     .\" HREF
354     \fBpcrejit\fP
355     .\"
356     documentation for more details.
357 nigel 75 .
358     .
359     .SH "SAVING PRECOMPILED PATTERNS FOR LATER USE"
360 nigel 63 .rs
361     .sp
362 nigel 75 The compiled form of a regular expression can be saved and re-used at a later
363     time, possibly by a different program, and even on a host other than the one on
364     which it was compiled. Details are given in the
365     .\" HREF
366     \fBpcreprecompile\fP
367     .\"
368 ph10 856 documentation, which includes a description of the
369     \fBpcre_pattern_to_host_byte_order()\fP function. However, compiling a regular
370     expression with one version of PCRE for use with a different version is not
371     guaranteed to work and may cause crashes.
372 nigel 75 .
373     .
374     .SH "CHECKING BUILD-TIME OPTIONS"
375     .rs
376     .sp
377     .B int pcre_config(int \fIwhat\fP, void *\fIwhere\fP);
378 nigel 63 .PP
379 nigel 75 The function \fBpcre_config()\fP makes it possible for a PCRE client to
380 nigel 63 discover which optional features have been compiled into the PCRE library. The
381     .\" HREF
382 nigel 75 \fBpcrebuild\fP
383 nigel 63 .\"
384     documentation has more details about these optional features.
385 nigel 75 .P
386     The first argument for \fBpcre_config()\fP is an integer, specifying which
387 nigel 63 information is required; the second argument is a pointer to a variable into
388 ph10 856 which the information is placed. The returned value is zero on success, or the
389     negative error code PCRE_ERROR_BADOPTION if the value in the first argument is
390     not recognized. The following information is available:
391 nigel 75 .sp
392 nigel 63 PCRE_CONFIG_UTF8
393 nigel 75 .sp
394 nigel 63 The output is an integer that is set to one if UTF-8 support is available;
395 ph10 903 otherwise it is set to zero. If this option is given to the 16-bit version of
396 ph10 856 this function, \fBpcre16_config()\fP, the result is PCRE_ERROR_BADOPTION.
397 nigel 75 .sp
398 ph10 856 PCRE_CONFIG_UTF16
399     .sp
400     The output is an integer that is set to one if UTF-16 support is available;
401     otherwise it is set to zero. This value should normally be given to the 16-bit
402     version of this function, \fBpcre16_config()\fP. If it is given to the 8-bit
403     version of this function, the result is PCRE_ERROR_BADOPTION.
404     .sp
405 nigel 75 PCRE_CONFIG_UNICODE_PROPERTIES
406     .sp
407     The output is an integer that is set to one if support for Unicode character
408     properties is available; otherwise it is set to zero.
409     .sp
410 ph10 678 PCRE_CONFIG_JIT
411     .sp
412 ph10 691 The output is an integer that is set to one if support for just-in-time
413     compiling is available; otherwise it is set to zero.
414 ph10 678 .sp
415 ph10 887 PCRE_CONFIG_JITTARGET
416     .sp
417     The output is a pointer to a zero-terminated "const char *" string. If JIT
418 ph10 903 support is available, the string contains the name of the architecture for
419     which the JIT compiler is configured, for example "x86 32bit (little endian +
420 ph10 887 unaligned)". If JIT support is not available, the result is NULL.
421     .sp
422 nigel 63 PCRE_CONFIG_NEWLINE
423 nigel 75 .sp
424 nigel 91 The output is an integer whose value specifies the default character sequence
425 nigel 93 that is recognized as meaning "newline". The four values that are supported
426 ph10 392 are: 10 for LF, 13 for CR, 3338 for CRLF, -2 for ANYCRLF, and -1 for ANY.
427 ph10 391 Though they are derived from ASCII, the same values are returned in EBCDIC
428     environments. The default should normally correspond to the standard sequence
429     for your operating system.
430 nigel 75 .sp
431 ph10 231 PCRE_CONFIG_BSR
432     .sp
433     The output is an integer whose value indicates what character sequences the \eR
434     escape sequence matches by default. A value of 0 means that \eR matches any
435     Unicode line ending sequence; a value of 1 means that \eR matches only CR, LF,
436     or CRLF. The default can be overridden when a pattern is compiled or matched.
437     .sp
438 nigel 63 PCRE_CONFIG_LINK_SIZE
439 nigel 75 .sp
440 nigel 63 The output is an integer that contains the number of bytes used for internal
441 ph10 856 linkage in compiled regular expressions. For the 8-bit library, the value can
442     be 2, 3, or 4. For the 16-bit library, the value is either 2 or 4 and is still
443     a number of bytes. The default value of 2 is sufficient for all but the most
444     massive patterns, since it allows the compiled pattern to be up to 64K in size.
445     Larger values allow larger regular expressions to be compiled, at the expense
446     of slower matching.
447 nigel 75 .sp
448 nigel 63 PCRE_CONFIG_POSIX_MALLOC_THRESHOLD
449 nigel 75 .sp
450 nigel 63 The output is an integer that contains the threshold above which the POSIX
451 nigel 75 interface uses \fBmalloc()\fP for output vectors. Further details are given in
452     the
453     .\" HREF
454     \fBpcreposix\fP
455     .\"
456     documentation.
457     .sp
458 nigel 63 PCRE_CONFIG_MATCH_LIMIT
459 nigel 75 .sp
460 ph10 376 The output is a long integer that gives the default limit for the number of
461 nigel 75 internal matching function calls in a \fBpcre_exec()\fP execution. Further
462     details are given with \fBpcre_exec()\fP below.
463     .sp
464 nigel 87 PCRE_CONFIG_MATCH_LIMIT_RECURSION
465     .sp
466 ph10 376 The output is a long integer that gives the default limit for the depth of
467 nigel 87 recursion when calling the internal matching function in a \fBpcre_exec()\fP
468     execution. Further details are given with \fBpcre_exec()\fP below.
469     .sp
470 nigel 73 PCRE_CONFIG_STACKRECURSE
471 nigel 75 .sp
472 nigel 77 The output is an integer that is set to one if internal recursion when running
473     \fBpcre_exec()\fP is implemented by recursive function calls that use the stack
474     to remember their state. This is the usual way that PCRE is compiled. The
475     output is zero if PCRE was compiled to use blocks of data on the heap instead
476     of recursive function calls. In this case, \fBpcre_stack_malloc\fP and
477     \fBpcre_stack_free\fP are called to manage memory blocks on the heap, thus
478     avoiding the use of the stack.
479 nigel 75 .
480     .
481     .SH "COMPILING A PATTERN"
482 nigel 63 .rs
483     .sp
484 nigel 75 .B pcre *pcre_compile(const char *\fIpattern\fP, int \fIoptions\fP,
485 nigel 63 .ti +5n
486 nigel 75 .B const char **\fIerrptr\fP, int *\fIerroffset\fP,
487 nigel 63 .ti +5n
488 nigel 75 .B const unsigned char *\fItableptr\fP);
489 nigel 77 .sp
490     .B pcre *pcre_compile2(const char *\fIpattern\fP, int \fIoptions\fP,
491     .ti +5n
492     .B int *\fIerrorcodeptr\fP,
493     .ti +5n
494     .B const char **\fIerrptr\fP, int *\fIerroffset\fP,
495     .ti +5n
496     .B const unsigned char *\fItableptr\fP);
497 nigel 75 .P
498 nigel 77 Either of the functions \fBpcre_compile()\fP or \fBpcre_compile2()\fP can be
499     called to compile a pattern into an internal form. The only difference between
500     the two interfaces is that \fBpcre_compile2()\fP has an additional argument,
501 ph10 461 \fIerrorcodeptr\fP, via which a numerical error code can be returned. To avoid
502     too much repetition, we refer just to \fBpcre_compile()\fP below, but the
503 ph10 456 information applies equally to \fBpcre_compile2()\fP.
504 nigel 75 .P
505 nigel 77 The pattern is a C string terminated by a binary zero, and is passed in the
506     \fIpattern\fP argument. A pointer to a single block of memory that is obtained
507     via \fBpcre_malloc\fP is returned. This contains the compiled code and related
508     data. The \fBpcre\fP type is defined for the returned block; this is a typedef
509     for a structure whose contents are not externally defined. It is up to the
510 nigel 91 caller to free the memory (via \fBpcre_free\fP) when it is no longer required.
511 nigel 77 .P
512 nigel 63 Although the compiled code of a PCRE regex is relocatable, that is, it does not
513 nigel 75 depend on memory location, the complete \fBpcre\fP data block is not
514     fully relocatable, because it may contain a copy of the \fItableptr\fP
515     argument, which is an address (see below).
516     .P
517 nigel 93 The \fIoptions\fP argument contains various bit settings that affect the
518 nigel 75 compilation. It should be zero if no options are required. The available
519 ph10 412 options are described below. Some of them (in particular, those that are
520 ph10 456 compatible with Perl, but some others as well) can also be set and unset from
521 ph10 412 within the pattern (see the detailed description in the
522 nigel 75 .\" HREF
523     \fBpcrepattern\fP
524     .\"
525 ph10 412 documentation). For those options that can be different in different parts of
526 ph10 456 the pattern, the contents of the \fIoptions\fP argument specifies their
527 ph10 461 settings at the start of compilation and execution. The PCRE_ANCHORED,
528 ph10 576 PCRE_BSR_\fIxxx\fP, PCRE_NEWLINE_\fIxxx\fP, PCRE_NO_UTF8_CHECK, and
529 ph10 930 PCRE_NO_START_OPTIMIZE options can be set at the time of matching as well as at
530 ph10 576 compile time.
531 nigel 75 .P
532     If \fIerrptr\fP is NULL, \fBpcre_compile()\fP returns NULL immediately.
533     Otherwise, if compilation of a pattern fails, \fBpcre_compile()\fP returns
534     NULL, and sets the variable pointed to by \fIerrptr\fP to point to a textual
535 nigel 87 error message. This is a static string that is part of the library. You must
536 ph10 598 not try to free it. Normally, the offset from the start of the pattern to the
537     byte that was being processed when the error was discovered is placed in the
538     variable pointed to by \fIerroffset\fP, which must not be NULL (if it is, an
539     immediate error is given). However, for an invalid UTF-8 string, the offset is
540 ph10 856 that of the first byte of the failing character.
541 nigel 75 .P
542 ph10 856 Some errors are not detected until the whole pattern has been scanned; in these
543     cases, the offset passed back is the length of the pattern. Note that the
544     offset is in bytes, not characters, even in UTF-8 mode. It may sometimes point
545     into the middle of a UTF-8 character.
546 ph10 569 .P
547 nigel 77 If \fBpcre_compile2()\fP is used instead of \fBpcre_compile()\fP, and the
548     \fIerrorcodeptr\fP argument is not NULL, a non-zero error code number is
549     returned via this argument in the event of an error. This is in addition to the
550     textual error message. Error codes and messages are listed below.
551     .P
552 nigel 75 If the final argument, \fItableptr\fP, is NULL, PCRE uses a default set of
553     character tables that are built when PCRE is compiled, using the default C
554     locale. Otherwise, \fItableptr\fP must be an address that is the result of a
555     call to \fBpcre_maketables()\fP. This value is stored with the compiled
556     pattern, and used again by \fBpcre_exec()\fP, unless another table pointer is
557     passed to it. For more discussion, see the section on locale support below.
558     .P
559     This code fragment shows a typical straightforward call to \fBpcre_compile()\fP:
560     .sp
561 nigel 63 pcre *re;
562     const char *error;
563     int erroffset;
564     re = pcre_compile(
565     "^A.*Z", /* the pattern */
566     0, /* default options */
567     &error, /* for error message */
568     &erroffset, /* for error offset */
569     NULL); /* use default character tables */
570 nigel 75 .sp
571     The following names for option bits are defined in the \fBpcre.h\fP header
572     file:
573     .sp
574 nigel 63 PCRE_ANCHORED
575 nigel 75 .sp
576 nigel 63 If this bit is set, the pattern is forced to be "anchored", that is, it is
577 nigel 75 constrained to match only at the first matching point in the string that is
578 nigel 63 being searched (the "subject string"). This effect can also be achieved by
579     appropriate constructs in the pattern itself, which is the only way to do it in
580     Perl.
581 nigel 75 .sp
582     PCRE_AUTO_CALLOUT
583     .sp
584     If this bit is set, \fBpcre_compile()\fP automatically inserts callout items,
585     all with number 255, before each pattern item. For discussion of the callout
586     facility, see the
587     .\" HREF
588     \fBpcrecallout\fP
589     .\"
590     documentation.
591     .sp
592 ph10 231 PCRE_BSR_ANYCRLF
593     PCRE_BSR_UNICODE
594     .sp
595     These options (which are mutually exclusive) control what the \eR escape
596     sequence matches. The choice is either to match only CR, LF, or CRLF, or to
597     match any Unicode newline sequence. The default is specified when PCRE is
598     built. It can be overridden from within the pattern, or by setting an option
599     when a compiled pattern is matched.
600     .sp
601 nigel 63 PCRE_CASELESS
602 nigel 75 .sp
603 nigel 63 If this bit is set, letters in the pattern match both upper and lower case
604     letters. It is equivalent to Perl's /i option, and it can be changed within a
605 nigel 77 pattern by a (?i) option setting. In UTF-8 mode, PCRE always understands the
606     concept of case for characters whose values are less than 128, so caseless
607     matching is always possible. For characters with higher values, the concept of
608     case is supported if PCRE is compiled with Unicode property support, but not
609     otherwise. If you want to use caseless matching for characters 128 and above,
610     you must ensure that PCRE is compiled with Unicode property support as well as
611     with UTF-8 support.
612 nigel 75 .sp
613 nigel 63 PCRE_DOLLAR_ENDONLY
614 nigel 75 .sp
615 nigel 63 If this bit is set, a dollar metacharacter in the pattern matches only at the
616     end of the subject string. Without this option, a dollar also matches
617 nigel 91 immediately before a newline at the end of the string (but not before any other
618     newlines). The PCRE_DOLLAR_ENDONLY option is ignored if PCRE_MULTILINE is set.
619     There is no equivalent to this option in Perl, and no way to set it within a
620     pattern.
621 nigel 75 .sp
622 nigel 63 PCRE_DOTALL
623 nigel 75 .sp
624 ph10 572 If this bit is set, a dot metacharacter in the pattern matches a character of
625     any value, including one that indicates a newline. However, it only ever
626     matches one character, even if newlines are coded as CRLF. Without this option,
627     a dot does not match when the current position is at a newline. This option is
628     equivalent to Perl's /s option, and it can be changed within a pattern by a
629     (?s) option setting. A negative class such as [^a] always matches newline
630     characters, independent of the setting of this option.
631 nigel 75 .sp
632 nigel 91 PCRE_DUPNAMES
633     .sp
634     If this bit is set, names used to identify capturing subpatterns need not be
635     unique. This can be helpful for certain types of pattern when it is known that
636     only one instance of the named subpattern can ever be matched. There are more
637     details of named subpatterns below; see also the
638     .\" HREF
639     \fBpcrepattern\fP
640     .\"
641     documentation.
642     .sp
643 nigel 63 PCRE_EXTENDED
644 nigel 75 .sp
645 nigel 63 If this bit is set, whitespace data characters in the pattern are totally
646     ignored except when escaped or inside a character class. Whitespace does not
647     include the VT character (code 11). In addition, characters between an
648 nigel 91 unescaped # outside a character class and the next newline, inclusive, are also
649     ignored. This is equivalent to Perl's /x option, and it can be changed within a
650     pattern by a (?x) option setting.
651 nigel 75 .P
652 ph10 598 Which characters are interpreted as newlines is controlled by the options
653     passed to \fBpcre_compile()\fP or by a special sequence at the start of the
654     pattern, as described in the section entitled
655 ph10 572 .\" HTML <a href="pcrepattern.html#newlines">
656     .\" </a>
657     "Newline conventions"
658     .\"
659     in the \fBpcrepattern\fP documentation. Note that the end of this type of
660     comment is a literal newline sequence in the pattern; escape sequences that
661     happen to represent a newline do not count.
662     .P
663 nigel 63 This option makes it possible to include comments inside complicated patterns.
664     Note, however, that this applies only to data characters. Whitespace characters
665     may never appear within special character sequences in a pattern, for example
666 ph10 572 within the sequence (?( that introduces a conditional subpattern.
667 nigel 75 .sp
668 nigel 63 PCRE_EXTRA
669 nigel 75 .sp
670 nigel 63 This option was invented in order to turn on additional functionality of PCRE
671     that is incompatible with Perl, but it is currently of very little use. When
672     set, any backslash in a pattern that is followed by a letter that has no
673     special meaning causes an error, thus reserving these combinations for future
674     expansion. By default, as in Perl, a backslash followed by a letter with no
675 nigel 91 special meaning is treated as a literal. (Perl can, however, be persuaded to
676 ph10 513 give an error for this, by running it with the -w option.) There are at present
677     no other features controlled by this option. It can also be set by a (?X)
678     option setting within a pattern.
679 nigel 75 .sp
680 nigel 77 PCRE_FIRSTLINE
681     .sp
682     If this option is set, an unanchored pattern is required to match before or at
683 nigel 91 the first newline in the subject string, though the matched text may continue
684     over the newline.
685 nigel 77 .sp
686 ph10 336 PCRE_JAVASCRIPT_COMPAT
687     .sp
688 ph10 345 If this option is set, PCRE's behaviour is changed in some ways so that it is
689 ph10 336 compatible with JavaScript rather than Perl. The changes are as follows:
690     .P
691     (1) A lone closing square bracket in a pattern causes a compile-time error,
692     because this is illegal in JavaScript (by default it is treated as a data
693     character). Thus, the pattern AB]CD becomes illegal when this option is set.
694     .P
695     (2) At run time, a back reference to an unset subpattern group matches an empty
696 ph10 345 string (by default this causes the current matching alternative to fail). A
697     pattern such as (\e1)(a) succeeds when this option is set (assuming it can find
698     an "a" in the subject), whereas it fails by default, for Perl compatibility.
699 ph10 745 .P
700 ph10 836 (3) \eU matches an upper case "U" character; by default \eU causes a compile
701 ph10 745 time error (Perl uses \eU to upper case subsequent characters).
702     .P
703 ph10 836 (4) \eu matches a lower case "u" character unless it is followed by four
704     hexadecimal digits, in which case the hexadecimal number defines the code point
705     to match. By default, \eu causes a compile time error (Perl uses it to upper
706 ph10 745 case the following character).
707     .P
708 ph10 836 (5) \ex matches a lower case "x" character unless it is followed by two
709     hexadecimal digits, in which case the hexadecimal number defines the code point
710     to match. By default, as in Perl, a hexadecimal number is always expected after
711     \ex, but it may have zero, one, or two digits (so, for example, \exz matches a
712 ph10 745 binary zero character followed by z).
713 ph10 336 .sp
714 nigel 63 PCRE_MULTILINE
715 nigel 75 .sp
716     By default, PCRE treats the subject string as consisting of a single line of
717     characters (even if it actually contains newlines). The "start of line"
718 nigel 63 metacharacter (^) matches only at the start of the string, while the "end of
719     line" metacharacter ($) matches only at the end of the string, or before a
720     terminating newline (unless PCRE_DOLLAR_ENDONLY is set). This is the same as
721     Perl.
722 nigel 75 .P
723 nigel 63 When PCRE_MULTILINE it is set, the "start of line" and "end of line" constructs
724 nigel 91 match immediately following or immediately before internal newlines in the
725     subject string, respectively, as well as at the very start and end. This is
726     equivalent to Perl's /m option, and it can be changed within a pattern by a
727     (?m) option setting. If there are no newlines in a subject string, or no
728 nigel 63 occurrences of ^ or $ in a pattern, setting PCRE_MULTILINE has no effect.
729 nigel 75 .sp
730 nigel 91 PCRE_NEWLINE_CR
731     PCRE_NEWLINE_LF
732     PCRE_NEWLINE_CRLF
733 ph10 150 PCRE_NEWLINE_ANYCRLF
734 nigel 93 PCRE_NEWLINE_ANY
735 nigel 91 .sp
736     These options override the default newline definition that was chosen when PCRE
737     was built. Setting the first or the second specifies that a newline is
738 nigel 93 indicated by a single character (CR or LF, respectively). Setting
739     PCRE_NEWLINE_CRLF specifies that a newline is indicated by the two-character
740 ph10 149 CRLF sequence. Setting PCRE_NEWLINE_ANYCRLF specifies that any of the three
741     preceding sequences should be recognized. Setting PCRE_NEWLINE_ANY specifies
742     that any Unicode newline sequence should be recognized. The Unicode newline
743     sequences are the three just mentioned, plus the single characters VT (vertical
744     tab, U+000B), FF (formfeed, U+000C), NEL (next line, U+0085), LS (line
745 ph10 903 separator, U+2028), and PS (paragraph separator, U+2029). For the 8-bit
746 ph10 856 library, the last two are recognized only in UTF-8 mode.
747 nigel 91 .P
748 nigel 93 The newline setting in the options word uses three bits that are treated
749 ph10 149 as a number, giving eight possibilities. Currently only six are used (default
750     plus the five values above). This means that if you set more than one newline
751 nigel 93 option, the combination may or may not be sensible. For example,
752     PCRE_NEWLINE_CR with PCRE_NEWLINE_LF is equivalent to PCRE_NEWLINE_CRLF, but
753 ph10 149 other combinations may yield unused numbers and cause an error.
754 nigel 93 .P
755 ph10 572 The only time that a line break in a pattern is specially recognized when
756     compiling is when PCRE_EXTENDED is set. CR and LF are whitespace characters,
757     and so are ignored in this mode. Also, an unescaped # outside a character class
758     indicates a comment that lasts until after the next line break sequence. In
759     other circumstances, line break sequences in patterns are treated as literal
760     data.
761 nigel 93 .P
762     The newline option that is set at compile time becomes the default that is used
763     for \fBpcre_exec()\fP and \fBpcre_dfa_exec()\fP, but it can be overridden.
764 nigel 91 .sp
765 nigel 63 PCRE_NO_AUTO_CAPTURE
766 nigel 75 .sp
767 nigel 63 If this option is set, it disables the use of numbered capturing parentheses in
768     the pattern. Any opening parenthesis that is not followed by ? behaves as if it
769     were followed by ?: but named parentheses can still be used for capturing (and
770     they acquire numbers in the usual way). There is no equivalent of this option
771     in Perl.
772 nigel 75 .sp
773 ph10 576 NO_START_OPTIMIZE
774     .sp
775     This is an option that acts at matching time; that is, it is really an option
776     for \fBpcre_exec()\fP or \fBpcre_dfa_exec()\fP. If it is set at compile time,
777     it is remembered with the compiled pattern and assumed at matching time. For
778     details see the discussion of PCRE_NO_START_OPTIMIZE
779     .\" HTML <a href="#execoptions">
780     .\" </a>
781     below.
782     .\"
783     .sp
784 ph10 518 PCRE_UCP
785     .sp
786 ph10 572 This option changes the way PCRE processes \eB, \eb, \eD, \ed, \eS, \es, \eW,
787     \ew, and some of the POSIX character classes. By default, only ASCII characters
788     are recognized, but if PCRE_UCP is set, Unicode properties are used instead to
789     classify characters. More details are given in the section on
790 ph10 518 .\" HTML <a href="pcre.html#genericchartypes">
791     .\" </a>
792     generic character types
793     .\"
794     in the
795     .\" HREF
796     \fBpcrepattern\fP
797     .\"
798     page. If you set PCRE_UCP, matching one of the items it affects takes much
799     longer. The option is available only if PCRE has been compiled with Unicode
800     property support.
801     .sp
802 nigel 63 PCRE_UNGREEDY
803 nigel 75 .sp
804 nigel 63 This option inverts the "greediness" of the quantifiers so that they are not
805     greedy by default, but become greedy if followed by "?". It is not compatible
806     with Perl. It can also be set by a (?U) option setting within the pattern.
807 nigel 75 .sp
808 nigel 63 PCRE_UTF8
809 nigel 75 .sp
810 nigel 63 This option causes PCRE to regard both the pattern and the subject as strings
811 ph10 856 of UTF-8 characters instead of single-byte strings. However, it is available
812     only when PCRE is built to include UTF support. If not, the use of this option
813     provokes an error. Details of how this option changes the behaviour of PCRE are
814     given in the
815 nigel 63 .\" HREF
816 ph10 678 \fBpcreunicode\fP
817 nigel 63 .\"
818     page.
819 nigel 75 .sp
820 nigel 71 PCRE_NO_UTF8_CHECK
821 nigel 75 .sp
822 ph10 903 When PCRE_UTF8 is set, the validity of the pattern as a UTF-8
823 ph10 856 string is automatically checked. There is a discussion about the
824     .\" HTML <a href="pcreunicode.html#utf8strings">
825 ph10 211 .\" </a>
826 ph10 903 validity of UTF-8 strings
827 ph10 211 .\"
828 ph10 856 in the
829 ph10 211 .\" HREF
830 ph10 856 \fBpcreunicode\fP
831 ph10 211 .\"
832 ph10 856 page. If an invalid UTF-8 sequence is found, \fBpcre_compile()\fP returns an
833     error. If you already know that your pattern is valid, and you want to skip
834     this check for performance reasons, you can set the PCRE_NO_UTF8_CHECK option.
835     When it is set, the effect of passing an invalid UTF-8 string as a pattern is
836     undefined. It may cause your program to crash. Note that this option can also
837     be passed to \fBpcre_exec()\fP and \fBpcre_dfa_exec()\fP, to suppress the
838     validity checking of subject strings.
839 nigel 75 .
840     .
841 nigel 77 .SH "COMPILATION ERROR CODES"
842     .rs
843     .sp
844     The following table lists the error codes than may be returned by
845     \fBpcre_compile2()\fP, along with the error messages that may be returned by
846 ph10 903 both compiling functions. Note that error messages are always 8-bit ASCII
847 ph10 856 strings, even in 16-bit mode. As PCRE has developed, some error codes have
848     fallen out of use. To avoid confusion, they have not been re-used.
849 nigel 77 .sp
850     0 no error
851     1 \e at end of pattern
852     2 \ec at end of pattern
853     3 unrecognized character follows \e
854     4 numbers out of order in {} quantifier
855     5 number too big in {} quantifier
856     6 missing terminating ] for character class
857     7 invalid escape sequence in character class
858     8 range out of order in character class
859     9 nothing to repeat
860 nigel 93 10 [this code is not in use]
861 nigel 77 11 internal error: unexpected repeat
862 ph10 290 12 unrecognized character after (? or (?-
863 nigel 77 13 POSIX named classes are supported only within a class
864     14 missing )
865     15 reference to non-existent subpattern
866     16 erroffset passed as NULL
867     17 unknown option bit(s) set
868     18 missing ) after comment
869 nigel 93 19 [this code is not in use]
870 ph10 290 20 regular expression is too large
871 nigel 77 21 failed to get memory
872     22 unmatched parentheses
873     23 internal error: code overflow
874     24 unrecognized character after (?<
875     25 lookbehind assertion is not fixed length
876 nigel 91 26 malformed number or name after (?(
877 nigel 77 27 conditional group contains more than two branches
878     28 assertion expected after (?(
879 ph10 181 29 (?R or (?[+-]digits must be followed by )
880 nigel 77 30 unknown POSIX class name
881     31 POSIX collating elements are not supported
882 ph10 856 32 this version of PCRE is compiled without UTF support
883 nigel 93 33 [this code is not in use]
884 nigel 77 34 character value in \ex{...} sequence is too large
885     35 invalid condition (?(0)
886     36 \eC not allowed in lookbehind assertion
887 ph10 656 37 PCRE does not support \eL, \el, \eN{name}, \eU, or \eu
888 nigel 77 38 number after (?C is > 255
889     39 closing ) for (?C expected
890     40 recursive call could loop indefinitely
891     41 unrecognized character after (?P
892 nigel 93 42 syntax error in subpattern name (missing terminator)
893 nigel 91 43 two named subpatterns have the same name
894 ph10 856 44 invalid UTF-8 string (specifically UTF-8)
895 nigel 77 45 support for \eP, \ep, and \eX has not been compiled
896     46 malformed \eP or \ep sequence
897     47 unknown property name after \eP or \ep
898 nigel 91 48 subpattern name is too long (maximum 32 characters)
899 ph10 290 49 too many named subpatterns (maximum 10000)
900 ph10 202 50 [this code is not in use]
901 ph10 856 51 octal value is greater than \e377 in 8-bit non-UTF-8 mode
902 nigel 93 52 internal error: overran compiling workspace
903 ph10 548 53 internal error: previously-checked referenced subpattern
904 ph10 546 not found
905 nigel 93 54 DEFINE group contains more than one branch
906     55 repeating a DEFINE group is not allowed
907 ph10 231 56 inconsistent NEWLINE options
908 ph10 345 57 \eg is not followed by a braced, angle-bracketed, or quoted
909     name/number or by a plain number
910 ph10 336 58 a numbered reference must not be zero
911 ph10 510 59 an argument is not allowed for (*ACCEPT), (*FAIL), or (*COMMIT)
912 ph10 290 60 (*VERB) not recognized
913     61 number is too big
914     62 subpattern name expected
915 ph10 292 63 digit expected after (?+
916 ph10 336 64 ] is an invalid data character in JavaScript compatibility mode
917 ph10 548 65 different names for subpatterns of the same number are
918 ph10 546 not allowed
919 ph10 510 66 (*MARK) must have an argument
920 ph10 903 67 this version of PCRE is not compiled with Unicode property
921 ph10 856 support
922 ph10 656 68 \ec must be followed by an ASCII character
923 ph10 659 69 \ek is not followed by a braced, angle-bracketed, or quoted name
924 ph10 856 70 internal error: unknown opcode in find_fixedlength()
925     71 \eN is not supported in a class
926     72 too many forward references
927 ph10 903 73 disallowed Unicode code point (>= 0xd800 && <= 0xdfff)
928 ph10 856 74 invalid UTF-16 string (specifically UTF-16)
929 ph10 290 .sp
930 ph10 292 The numbers 32 and 10000 in errors 48 and 49 are defaults; different values may
931 ph10 290 be used if the limits were changed when PCRE was built.
932 nigel 77 .
933     .
934 ph10 656 .\" HTML <a name="studyingapattern"></a>
935 nigel 75 .SH "STUDYING A PATTERN"
936 nigel 63 .rs
937     .sp
938 nigel 77 .B pcre_extra *pcre_study(const pcre *\fIcode\fP, int \fIoptions\fP
939 nigel 63 .ti +5n
940 nigel 75 .B const char **\fIerrptr\fP);
941 nigel 63 .PP
942 nigel 75 If a compiled pattern is going to be used several times, it is worth spending
943     more time analyzing it in order to speed up the time taken for matching. The
944     function \fBpcre_study()\fP takes a pointer to a compiled pattern as its first
945     argument. If studying the pattern produces additional information that will
946     help speed up matching, \fBpcre_study()\fP returns a pointer to a
947     \fBpcre_extra\fP block, in which the \fIstudy_data\fP field points to the
948     results of the study.
949     .P
950     The returned value from \fBpcre_study()\fP can be passed directly to
951 ph10 455 \fBpcre_exec()\fP or \fBpcre_dfa_exec()\fP. However, a \fBpcre_extra\fP block
952     also contains other fields that can be set by the caller before the block is
953     passed; these are described
954 nigel 75 .\" HTML <a href="#extradata">
955     .\" </a>
956     below
957     .\"
958     in the section on matching a pattern.
959     .P
960 ph10 455 If studying the pattern does not produce any useful information,
961 nigel 75 \fBpcre_study()\fP returns NULL. In that circumstance, if the calling program
962 ph10 461 wants to pass any of the other fields to \fBpcre_exec()\fP or
963 ph10 455 \fBpcre_dfa_exec()\fP, it must set up its own \fBpcre_extra\fP block.
964 nigel 75 .P
965 ph10 921 The second argument of \fBpcre_study()\fP contains option bits. There are three
966     options:
967     .sp
968     PCRE_STUDY_JIT_COMPILE
969     PCRE_STUDY_JIT_PARTIAL_HARD_COMPILE
970     PCRE_STUDY_JIT_PARTIAL_SOFT_COMPILE
971     .sp
972     If any of these are set, and the just-in-time compiler is available, the
973     pattern is further compiled into machine code that executes much faster than
974     the \fBpcre_exec()\fP interpretive matching function. If the just-in-time
975     compiler is not available, these options are ignored. All other bits in the
976     \fIoptions\fP argument must be zero.
977 nigel 75 .P
978 ph10 691 JIT compilation is a heavyweight optimization. It can take some time for
979 ph10 678 patterns to be analyzed, and for one-off matches and simple patterns the
980     benefit of faster execution might be offset by a much slower study time.
981 ph10 691 Not all patterns can be optimized by the JIT compiler. For those that cannot be
982 ph10 678 handled, matching automatically falls back to the \fBpcre_exec()\fP
983     interpreter. For more details, see the
984     .\" HREF
985     \fBpcrejit\fP
986     .\"
987     documentation.
988     .P
989 nigel 75 The third argument for \fBpcre_study()\fP is a pointer for an error message. If
990 nigel 63 studying succeeds (even if no data is returned), the variable it points to is
991 nigel 87 set to NULL. Otherwise it is set to point to a textual error message. This is a
992     static string that is part of the library. You must not try to free it. You
993     should test the error pointer for NULL after calling \fBpcre_study()\fP, to be
994     sure that it has run successfully.
995 nigel 75 .P
996 ph10 678 When you are finished with a pattern, you can free the memory used for the
997     study data by calling \fBpcre_free_study()\fP. This function was added to the
998     API for release 8.20. For earlier versions, the memory could be freed with
999     \fBpcre_free()\fP, just like the pattern itself. This will still work in cases
1000 ph10 921 where JIT optimization is not used, but it is advisable to change to the new
1001     function when convenient.
1002 ph10 678 .P
1003 ph10 691 This is a typical way in which \fBpcre_study\fP() is used (except that in a
1004 ph10 678 real application there should be tests for errors):
1005 nigel 75 .sp
1006 ph10 678 int rc;
1007     pcre *re;
1008     pcre_extra *sd;
1009     re = pcre_compile("pattern", 0, &error, &erroroffset, NULL);
1010     sd = pcre_study(
1011 nigel 63 re, /* result of pcre_compile() */
1012 ph10 678 0, /* no options */
1013 nigel 63 &error); /* set to NULL or points to a message */
1014 ph10 678 rc = pcre_exec( /* see below for details of pcre_exec() options */
1015 ph10 691 re, sd, "subject", 7, 0, 0, ovector, 30);
1016 ph10 678 ...
1017     pcre_free_study(sd);
1018 ph10 691 pcre_free(re);
1019 nigel 75 .sp
1020 ph10 455 Studying a pattern does two things: first, a lower bound for the length of
1021 ph10 461 subject string that is needed to match the pattern is computed. This does not
1022     mean that there are any strings of that length that match, but it does
1023     guarantee that no shorter strings match. The value is used by
1024     \fBpcre_exec()\fP and \fBpcre_dfa_exec()\fP to avoid wasting time by trying to
1025     match strings that are shorter than the lower bound. You can find out the value
1026 ph10 455 in a calling program via the \fBpcre_fullinfo()\fP function.
1027     .P
1028     Studying a pattern is also useful for non-anchored patterns that do not have a
1029     single fixed starting character. A bitmap of possible starting bytes is
1030 ph10 461 created. This speeds up finding a position in the subject at which to start
1031 ph10 856 matching. (In 16-bit mode, the bitmap is used for 16-bit values less than 256.)
1032 ph10 547 .P
1033 ph10 691 These two optimizations apply to both \fBpcre_exec()\fP and
1034 ph10 921 \fBpcre_dfa_exec()\fP, and the information is also used by the JIT compiler.
1035     The optimizations can be disabled by setting the PCRE_NO_START_OPTIMIZE option
1036     when calling \fBpcre_exec()\fP or \fBpcre_dfa_exec()\fP, but if this is done,
1037     JIT execution is also disabled. You might want to do this if your pattern
1038     contains callouts or (*MARK) and you want to make use of these facilities in
1039     cases where matching fails. See the discussion of PCRE_NO_START_OPTIMIZE
1040 ph10 547 .\" HTML <a href="#execoptions">
1041     .\" </a>
1042     below.
1043     .\"
1044 nigel 75 .
1045     .
1046 nigel 63 .\" HTML <a name="localesupport"></a>
1047 nigel 75 .SH "LOCALE SUPPORT"
1048 nigel 63 .rs
1049     .sp
1050 ph10 139 PCRE handles caseless matching, and determines whether characters are letters,
1051 nigel 75 digits, or whatever, by reference to a set of tables, indexed by character
1052 ph10 856 value. When running in UTF-8 mode, this applies only to characters
1053     with codes less than 128. By default, higher-valued codes never match escapes
1054     such as \ew or \ed, but they can be tested with \ep if PCRE is built with
1055     Unicode character property support. Alternatively, the PCRE_UCP option can be
1056     set at compile time; this causes \ew and friends to use Unicode property
1057     support instead of built-in tables. The use of locales with Unicode is
1058     discouraged. If you are handling characters with codes greater than 128, you
1059     should either use UTF-8 and Unicode, or use locales, but not try to mix the
1060     two.
1061 nigel 75 .P
1062 ph10 139 PCRE contains an internal set of tables that are used when the final argument
1063     of \fBpcre_compile()\fP is NULL. These are sufficient for many applications.
1064 ph10 142 Normally, the internal tables recognize only ASCII characters. However, when
1065 ph10 139 PCRE is built, it is possible to cause the internal tables to be rebuilt in the
1066     default "C" locale of the local system, which may cause them to be different.
1067 nigel 75 .P
1068 ph10 139 The internal tables can always be overridden by tables supplied by the
1069     application that calls PCRE. These may be created in a different locale from
1070     the default. As more and more applications change to using Unicode, the need
1071     for this locale support is expected to die away.
1072     .P
1073 nigel 75 External tables are built by calling the \fBpcre_maketables()\fP function,
1074     which has no arguments, in the relevant locale. The result can then be passed
1075     to \fBpcre_compile()\fP or \fBpcre_exec()\fP as often as necessary. For
1076     example, to build and use tables that are appropriate for the French locale
1077     (where accented characters with values greater than 128 are treated as letters),
1078     the following code could be used:
1079     .sp
1080     setlocale(LC_CTYPE, "fr_FR");
1081 nigel 63 tables = pcre_maketables();
1082     re = pcre_compile(..., tables);
1083 nigel 75 .sp
1084 ph10 142 The locale name "fr_FR" is used on Linux and other Unix-like systems; if you
1085 ph10 139 are using Windows, the name for the French locale is "french".
1086     .P
1087 nigel 75 When \fBpcre_maketables()\fP runs, the tables are built in memory that is
1088     obtained via \fBpcre_malloc\fP. It is the caller's responsibility to ensure
1089     that the memory containing the tables remains available for as long as it is
1090     needed.
1091     .P
1092     The pointer that is passed to \fBpcre_compile()\fP is saved with the compiled
1093     pattern, and the same tables are used via this pointer by \fBpcre_study()\fP
1094     and normally also by \fBpcre_exec()\fP. Thus, by default, for any single
1095     pattern, compilation, studying and matching all happen in the same locale, but
1096     different patterns can be compiled in different locales.
1097     .P
1098     It is possible to pass a table pointer or NULL (indicating the use of the
1099     internal tables) to \fBpcre_exec()\fP. Although not intended for this purpose,
1100     this facility could be used to match a pattern in a different locale from the
1101     one in which it was compiled. Passing table pointers at run time is discussed
1102     below in the section on matching a pattern.
1103     .
1104     .
1105 ph10 598 .\" HTML <a name="infoaboutpattern"></a>
1106 nigel 75 .SH "INFORMATION ABOUT A PATTERN"
1107 nigel 63 .rs
1108     .sp
1109 nigel 75 .B int pcre_fullinfo(const pcre *\fIcode\fP, "const pcre_extra *\fIextra\fP,"
1110 nigel 63 .ti +5n
1111 nigel 75 .B int \fIwhat\fP, void *\fIwhere\fP);
1112 nigel 63 .PP
1113 nigel 75 The \fBpcre_fullinfo()\fP function returns information about a compiled
1114 ph10 856 pattern. It replaces the \fBpcre_info()\fP function, which was removed from the
1115     library at version 8.30, after more than 10 years of obsolescence.
1116 nigel 75 .P
1117     The first argument for \fBpcre_fullinfo()\fP is a pointer to the compiled
1118     pattern. The second argument is the result of \fBpcre_study()\fP, or NULL if
1119 nigel 63 the pattern was not studied. The third argument specifies which piece of
1120     information is required, and the fourth argument is a pointer to a variable
1121     to receive the data. The yield of the function is zero for success, or one of
1122     the following negative numbers:
1123 nigel 75 .sp
1124 ph10 856 PCRE_ERROR_NULL the argument \fIcode\fP was NULL
1125     the argument \fIwhere\fP was NULL
1126     PCRE_ERROR_BADMAGIC the "magic number" was not found
1127 ph10 903 PCRE_ERROR_BADENDIANNESS the pattern was compiled with different
1128 ph10 856 endianness
1129     PCRE_ERROR_BADOPTION the value of \fIwhat\fP was invalid
1130 nigel 75 .sp
1131     The "magic number" is placed at the start of each compiled pattern as an simple
1132 ph10 903 check against passing an arbitrary memory pointer. The endianness error can
1133 ph10 856 occur if a compiled pattern is saved and reloaded on a different host. Here is
1134     a typical call of \fBpcre_fullinfo()\fP, to obtain the length of the compiled
1135     pattern:
1136 nigel 75 .sp
1137 nigel 63 int rc;
1138 nigel 91 size_t length;
1139 nigel 63 rc = pcre_fullinfo(
1140     re, /* result of pcre_compile() */
1141 ph10 678 sd, /* result of pcre_study(), or NULL */
1142 nigel 63 PCRE_INFO_SIZE, /* what is required */
1143     &length); /* where to put the data */
1144 nigel 75 .sp
1145     The possible values for the third argument are defined in \fBpcre.h\fP, and are
1146 nigel 63 as follows:
1147 nigel 75 .sp
1148 nigel 63 PCRE_INFO_BACKREFMAX
1149 nigel 75 .sp
1150 nigel 63 Return the number of the highest back reference in the pattern. The fourth
1151 nigel 75 argument should point to an \fBint\fP variable. Zero is returned if there are
1152 nigel 63 no back references.
1153 nigel 75 .sp
1154 nigel 63 PCRE_INFO_CAPTURECOUNT
1155 nigel 75 .sp
1156 nigel 63 Return the number of capturing subpatterns in the pattern. The fourth argument
1157 nigel 75 should point to an \fBint\fP variable.
1158     .sp
1159 nigel 77 PCRE_INFO_DEFAULT_TABLES
1160 nigel 75 .sp
1161     Return a pointer to the internal default character tables within PCRE. The
1162     fourth argument should point to an \fBunsigned char *\fP variable. This
1163     information call is provided for internal use by the \fBpcre_study()\fP
1164     function. External callers can cause PCRE to use its internal tables by passing
1165     a NULL table pointer.
1166     .sp
1167 nigel 63 PCRE_INFO_FIRSTBYTE
1168 nigel 75 .sp
1169 ph10 856 Return information about the first data unit of any matched string, for a
1170     non-anchored pattern. (The name of this option refers to the 8-bit library,
1171     where data units are bytes.) The fourth argument should point to an \fBint\fP
1172     variable.
1173 nigel 75 .P
1174 ph10 856 If there is a fixed first value, for example, the letter "c" from a pattern
1175 ph10 903 such as (cat|cow|coyote), its value is returned. In the 8-bit library, the
1176     value is always less than 256; in the 16-bit library the value can be up to
1177 ph10 856 0xffff.
1178     .P
1179     If there is no fixed first value, and if either
1180 nigel 75 .sp
1181 nigel 63 (a) the pattern was compiled with the PCRE_MULTILINE option, and every branch
1182     starts with "^", or
1183 nigel 75 .sp
1184 nigel 63 (b) every branch of the pattern starts with ".*" and PCRE_DOTALL is not set
1185     (if it were set, the pattern would be anchored),
1186 nigel 75 .sp
1187 nigel 63 -1 is returned, indicating that the pattern matches only at the start of a
1188     subject string or after any newline within the string. Otherwise -2 is
1189     returned. For anchored patterns, -2 is returned.
1190 nigel 75 .sp
1191 nigel 63 PCRE_INFO_FIRSTTABLE
1192 nigel 75 .sp
1193 nigel 63 If the pattern was studied, and this resulted in the construction of a 256-bit
1194 ph10 856 table indicating a fixed set of values for the first data unit in any matching
1195 nigel 63 string, a pointer to the table is returned. Otherwise NULL is returned. The
1196 nigel 75 fourth argument should point to an \fBunsigned char *\fP variable.
1197     .sp
1198 ph10 226 PCRE_INFO_HASCRORLF
1199     .sp
1200 ph10 227 Return 1 if the pattern contains any explicit matches for CR or LF characters,
1201 ph10 243 otherwise 0. The fourth argument should point to an \fBint\fP variable. An
1202 ph10 231 explicit match is either a literal CR or LF character, or \er or \en.
1203 ph10 226 .sp
1204 ph10 169 PCRE_INFO_JCHANGED
1205     .sp
1206 ph10 278 Return 1 if the (?J) or (?-J) option setting is used in the pattern, otherwise
1207     0. The fourth argument should point to an \fBint\fP variable. (?J) and
1208     (?-J) set and unset the local PCRE_DUPNAMES option, respectively.
1209 ph10 169 .sp
1210 ph10 678 PCRE_INFO_JIT
1211     .sp
1212 ph10 921 Return 1 if the pattern was studied with one of the JIT options, and
1213 ph10 678 just-in-time compiling was successful. The fourth argument should point to an
1214     \fBint\fP variable. A return value of 0 means that JIT support is not available
1215 ph10 921 in this version of PCRE, or that the pattern was not studied with a JIT option,
1216     or that the JIT compiler could not handle this particular pattern. See the
1217 ph10 678 .\" HREF
1218     \fBpcrejit\fP
1219     .\"
1220     documentation for details of what can and cannot be handled.
1221     .sp
1222 ph10 836 PCRE_INFO_JITSIZE
1223     .sp
1224 ph10 921 If the pattern was successfully studied with a JIT option, return the size of
1225     the JIT compiled code, otherwise return zero. The fourth argument should point
1226     to a \fBsize_t\fP variable.
1227 ph10 836 .sp
1228 nigel 63 PCRE_INFO_LASTLITERAL
1229 nigel 75 .sp
1230 ph10 856 Return the value of the rightmost literal data unit that must exist in any
1231     matched string, other than at its start, if such a value has been recorded. The
1232     fourth argument should point to an \fBint\fP variable. If there is no such
1233     value, -1 is returned. For anchored patterns, a last literal value is recorded
1234     only if it follows something of variable length. For example, for the pattern
1235 nigel 75 /^a\ed+z\ed+/ the returned value is "z", but for /^a\edz\ed/ the returned value
1236 nigel 65 is -1.
1237 nigel 75 .sp
1238 ph10 932 PCRE_INFO_MAXLOOKBEHIND
1239     .sp
1240     Return the number of characters (NB not bytes) in the longest lookbehind
1241     assertion in the pattern. Note that the simple assertions \eb and \eB require a
1242     one-character lookbehind. This information is useful when doing multi-segment
1243     matching using the partial matching facilities.
1244     .sp
1245 ph10 455 PCRE_INFO_MINLENGTH
1246     .sp
1247     If the pattern was studied and a minimum length for matching subject strings
1248     was computed, its value is returned. Otherwise the returned value is -1. The
1249 ph10 856 value is a number of characters, which in UTF-8 mode may be different from the
1250     number of bytes. The fourth argument should point to an \fBint\fP variable. A
1251 ph10 455 non-negative value is a lower bound to the length of any matching string. There
1252     may not be any strings of that length that do actually match, but every string
1253     that does match is at least that long.
1254     .sp
1255 nigel 63 PCRE_INFO_NAMECOUNT
1256     PCRE_INFO_NAMEENTRYSIZE
1257     PCRE_INFO_NAMETABLE
1258 nigel 75 .sp
1259 nigel 63 PCRE supports the use of named as well as numbered capturing parentheses. The
1260     names are just an additional way of identifying the parentheses, which still
1261 nigel 91 acquire numbers. Several convenience functions such as
1262     \fBpcre_get_named_substring()\fP are provided for extracting captured
1263     substrings by name. It is also possible to extract the data directly, by first
1264     converting the name to a number in order to access the correct pointers in the
1265     output vector (described with \fBpcre_exec()\fP below). To do the conversion,
1266     you need to use the name-to-number map, which is described by these three
1267     values.
1268 nigel 75 .P
1269 nigel 63 The map consists of a number of fixed-size entries. PCRE_INFO_NAMECOUNT gives
1270     the number of entries, and PCRE_INFO_NAMEENTRYSIZE gives the size of each
1271 nigel 75 entry; both of these return an \fBint\fP value. The entry size depends on the
1272 nigel 63 length of the longest name. PCRE_INFO_NAMETABLE returns a pointer to the first
1273 ph10 856 entry of the table. This is a pointer to \fBchar\fP in the 8-bit library, where
1274     the first two bytes of each entry are the number of the capturing parenthesis,
1275     most significant byte first. In the 16-bit library, the pointer points to
1276     16-bit data units, the first of which contains the parenthesis number. The rest
1277     of the entry is the corresponding name, zero terminated.
1278 ph10 457 .P
1279     The names are in alphabetical order. Duplicate names may appear if (?| is used
1280     to create multiple groups with the same number, as described in the
1281     .\" HTML <a href="pcrepattern.html#dupsubpatternnumber">
1282     .\" </a>
1283     section on duplicate subpattern numbers
1284     .\"
1285     in the
1286     .\" HREF
1287     \fBpcrepattern\fP
1288     .\"
1289 ph10 461 page. Duplicate names for subpatterns with different numbers are permitted only
1290     if PCRE_DUPNAMES is set. In all cases of duplicate names, they appear in the
1291     table in the order in which they were found in the pattern. In the absence of
1292     (?| this is the order of increasing number; when (?| is used this is not
1293 ph10 457 necessarily the case because later subpatterns may have lower numbers.
1294     .P
1295     As a simple example of the name/number table, consider the following pattern
1296 ph10 856 after compilation by the 8-bit library (assume PCRE_EXTENDED is set, so white
1297     space - including newlines - is ignored):
1298 nigel 75 .sp
1299     .\" JOIN
1300 nigel 93 (?<date> (?<year>(\ed\ed)?\ed\ed) -
1301     (?<month>\ed\ed) - (?<day>\ed\ed) )
1302 nigel 75 .sp
1303 nigel 63 There are four named subpatterns, so the table has four entries, and each entry
1304     in the table is eight bytes long. The table is as follows, with non-printing
1305 nigel 75 bytes shows in hexadecimal, and undefined bytes shown as ??:
1306     .sp
1307 nigel 63 00 01 d a t e 00 ??
1308     00 05 d a y 00 ?? ??
1309     00 04 m o n t h 00
1310     00 02 y e a r 00 ??
1311 nigel 75 .sp
1312     When writing code to extract data from named subpatterns using the
1313 nigel 91 name-to-number map, remember that the length of the entries is likely to be
1314 nigel 75 different for each compiled pattern.
1315     .sp
1316 ph10 169 PCRE_INFO_OKPARTIAL
1317     .sp
1318 ph10 435 Return 1 if the pattern can be used for partial matching with
1319     \fBpcre_exec()\fP, otherwise 0. The fourth argument should point to an
1320     \fBint\fP variable. From release 8.00, this always returns 1, because the
1321     restrictions that previously applied to partial matching have been lifted. The
1322 ph10 169 .\" HREF
1323     \fBpcrepartial\fP
1324     .\"
1325 ph10 426 documentation gives details of partial matching.
1326 ph10 169 .sp
1327 nigel 63 PCRE_INFO_OPTIONS
1328 nigel 75 .sp
1329 nigel 63 Return a copy of the options with which the pattern was compiled. The fourth
1330 nigel 75 argument should point to an \fBunsigned long int\fP variable. These option bits
1331     are those specified in the call to \fBpcre_compile()\fP, modified by any
1332 ph10 196 top-level option settings at the start of the pattern itself. In other words,
1333     they are the options that will be in force when matching starts. For example,
1334     if the pattern /(?im)abc(?-i)d/ is compiled with the PCRE_EXTENDED option, the
1335     result is PCRE_CASELESS, PCRE_MULTILINE, and PCRE_EXTENDED.
1336 nigel 75 .P
1337 nigel 63 A pattern is automatically anchored by PCRE if all of its top-level
1338     alternatives begin with one of the following:
1339 nigel 75 .sp
1340 nigel 63 ^ unless PCRE_MULTILINE is set
1341 nigel 75 \eA always
1342     \eG always
1343     .\" JOIN
1344 nigel 63 .* if PCRE_DOTALL is set and there are no back
1345     references to the subpattern in which .* appears
1346 nigel 75 .sp
1347 nigel 63 For such patterns, the PCRE_ANCHORED bit is set in the options returned by
1348 nigel 75 \fBpcre_fullinfo()\fP.
1349     .sp
1350 nigel 63 PCRE_INFO_SIZE
1351 nigel 75 .sp
1352 ph10 856 Return the size of the compiled pattern in bytes (for both libraries). The
1353     fourth argument should point to a \fBsize_t\fP variable. This value does not
1354     include the size of the \fBpcre\fP structure that is returned by
1355     \fBpcre_compile()\fP. The value that is passed as the argument to
1356     \fBpcre_malloc()\fP when \fBpcre_compile()\fP is getting memory in which to
1357     place the compiled data is the value returned by this option plus the size of
1358     the \fBpcre\fP structure. Studying a compiled pattern, with or without JIT,
1359     does not alter the value returned by this option.
1360 nigel 75 .sp
1361 nigel 63 PCRE_INFO_STUDYSIZE
1362 nigel 75 .sp
1363 ph10 856 Return the size in bytes of the data block pointed to by the \fIstudy_data\fP
1364     field in a \fBpcre_extra\fP block. If \fBpcre_extra\fP is NULL, or there is no
1365     study data, zero is returned. The fourth argument should point to a
1366     \fBsize_t\fP variable. The \fIstudy_data\fP field is set by \fBpcre_study()\fP
1367     to record information that will speed up matching (see the section entitled
1368 ph10 656 .\" HTML <a href="#studyingapattern">
1369     .\" </a>
1370 ph10 659 "Studying a pattern"
1371 ph10 656 .\"
1372     above). The format of the \fIstudy_data\fP block is private, but its length
1373     is made available via this option so that it can be saved and restored (see the
1374     .\" HREF
1375     \fBpcreprecompile\fP
1376     .\"
1377     documentation for details).
1378 nigel 75 .
1379     .
1380 nigel 77 .SH "REFERENCE COUNTS"
1381 nigel 63 .rs
1382     .sp
1383 nigel 77 .B int pcre_refcount(pcre *\fIcode\fP, int \fIadjust\fP);
1384     .PP
1385     The \fBpcre_refcount()\fP function is used to maintain a reference count in the
1386     data block that contains a compiled pattern. It is provided for the benefit of
1387     applications that operate in an object-oriented manner, where different parts
1388     of the application may be using the same compiled pattern, but you want to free
1389     the block when they are all done.
1390     .P
1391     When a pattern is compiled, the reference count field is initialized to zero.
1392     It is changed only by calling this function, whose action is to add the
1393     \fIadjust\fP value (which may be positive or negative) to it. The yield of the
1394     function is the new value. However, the value of the count is constrained to
1395     lie between 0 and 65535, inclusive. If the new value is outside these limits,
1396     it is forced to the appropriate limit value.
1397     .P
1398     Except when it is zero, the reference count is not correctly preserved if a
1399     pattern is compiled on one host and then transferred to a host whose byte-order
1400     is different. (This seems a highly unlikely scenario.)
1401     .
1402     .
1403     .SH "MATCHING A PATTERN: THE TRADITIONAL FUNCTION"
1404     .rs
1405     .sp
1406 nigel 75 .B int pcre_exec(const pcre *\fIcode\fP, "const pcre_extra *\fIextra\fP,"
1407 nigel 63 .ti +5n
1408 nigel 75 .B "const char *\fIsubject\fP," int \fIlength\fP, int \fIstartoffset\fP,
1409 nigel 63 .ti +5n
1410 nigel 75 .B int \fIoptions\fP, int *\fIovector\fP, int \fIovecsize\fP);
1411     .P
1412     The function \fBpcre_exec()\fP is called to match a subject string against a
1413     compiled pattern, which is passed in the \fIcode\fP argument. If the
1414 ph10 455 pattern was studied, the result of the study should be passed in the
1415 ph10 707 \fIextra\fP argument. You can call \fBpcre_exec()\fP with the same \fIcode\fP
1416     and \fIextra\fP arguments as many times as you like, in order to match
1417     different subject strings with the same pattern.
1418     .P
1419     This function is the main matching facility of the library, and it operates in
1420     a Perl-like manner. For specialist use there is also an alternative matching
1421     function, which is described
1422 nigel 77 .\" HTML <a href="#dfamatch">
1423     .\" </a>
1424     below
1425     .\"
1426     in the section about the \fBpcre_dfa_exec()\fP function.
1427 nigel 75 .P
1428     In most applications, the pattern will have been compiled (and optionally
1429     studied) in the same process that calls \fBpcre_exec()\fP. However, it is
1430     possible to save compiled patterns and study data, and then use them later
1431     in different processes, possibly even on different hosts. For a discussion
1432     about this, see the
1433     .\" HREF
1434     \fBpcreprecompile\fP
1435     .\"
1436     documentation.
1437     .P
1438     Here is an example of a simple call to \fBpcre_exec()\fP:
1439     .sp
1440 nigel 63 int rc;
1441     int ovector[30];
1442     rc = pcre_exec(
1443     re, /* result of pcre_compile() */
1444     NULL, /* we didn't study the pattern */
1445     "some string", /* the subject string */
1446     11, /* the length of the subject string */
1447     0, /* start at offset 0 in the subject */
1448     0, /* default options */
1449 nigel 75 ovector, /* vector of integers for substring information */
1450 nigel 77 30); /* number of elements (NOT size in bytes) */
1451 nigel 75 .
1452 ph10 656 .
1453 nigel 75 .\" HTML <a name="extradata"></a>
1454     .SS "Extra data for \fBpcre_exec()\fR"
1455     .rs
1456     .sp
1457     If the \fIextra\fP argument is not NULL, it must point to a \fBpcre_extra\fP
1458     data block. The \fBpcre_study()\fP function returns such a block (when it
1459 nigel 63 doesn't return NULL), but you can also create one for yourself, and pass
1460 nigel 87 additional information in it. The \fBpcre_extra\fP block contains the following
1461     fields (not necessarily in this order):
1462 nigel 75 .sp
1463     unsigned long int \fIflags\fP;
1464     void *\fIstudy_data\fP;
1465 ph10 691 void *\fIexecutable_jit\fP;
1466 nigel 75 unsigned long int \fImatch_limit\fP;
1467 nigel 87 unsigned long int \fImatch_limit_recursion\fP;
1468 nigel 75 void *\fIcallout_data\fP;
1469     const unsigned char *\fItables\fP;
1470 ph10 512 unsigned char **\fImark\fP;
1471 nigel 75 .sp
1472 ph10 903 In the 16-bit version of this structure, the \fImark\fP field has type
1473 ph10 859 "PCRE_UCHAR16 **".
1474 ph10 856 .P
1475 ph10 926 The \fIflags\fP field is used to specify which of the other fields are set. The
1476     flag bits are:
1477 nigel 75 .sp
1478 ph10 922 PCRE_EXTRA_CALLOUT_DATA
1479 ph10 691 PCRE_EXTRA_EXECUTABLE_JIT
1480 ph10 922 PCRE_EXTRA_MARK
1481 nigel 63 PCRE_EXTRA_MATCH_LIMIT
1482 nigel 87 PCRE_EXTRA_MATCH_LIMIT_RECURSION
1483 ph10 922 PCRE_EXTRA_STUDY_DATA
1484 nigel 75 PCRE_EXTRA_TABLES
1485     .sp
1486 ph10 678 Other flag bits should be set to zero. The \fIstudy_data\fP field and sometimes
1487     the \fIexecutable_jit\fP field are set in the \fBpcre_extra\fP block that is
1488     returned by \fBpcre_study()\fP, together with the appropriate flag bits. You
1489 ph10 922 should not set these yourself, but you may add to the block by setting other
1490     fields and their corresponding flag bits.
1491 nigel 75 .P
1492     The \fImatch_limit\fP field provides a means of preventing PCRE from using up a
1493 nigel 63 vast amount of resources when running patterns that are not going to match,
1494     but which have a very large number of possibilities in their search trees. The
1495 ph10 456 classic example is a pattern that uses nested unlimited repeats.
1496 nigel 75 .P
1497 ph10 678 Internally, \fBpcre_exec()\fP uses a function called \fBmatch()\fP, which it
1498     calls repeatedly (sometimes recursively). The limit set by \fImatch_limit\fP is
1499     imposed on the number of times this function is called during a match, which
1500     has the effect of limiting the amount of backtracking that can take place. For
1501     patterns that are not anchored, the count restarts from zero for each position
1502 ph10 691 in the subject string.
1503 nigel 75 .P
1504 ph10 691 When \fBpcre_exec()\fP is called with a pattern that was successfully studied
1505 ph10 921 with a JIT option, the way that the matching is executed is entirely different.
1506     However, there is still the possibility of runaway matching that goes on for a
1507     very long time, and so the \fImatch_limit\fP value is also used in this case
1508     (but in a different way) to limit how long the matching can continue.
1509 ph10 678 .P
1510 nigel 87 The default value for the limit can be set when PCRE is built; the default
1511 nigel 63 default is 10 million, which handles all but the most extreme cases. You can
1512 nigel 87 override the default by suppling \fBpcre_exec()\fP with a \fBpcre_extra\fP
1513     block in which \fImatch_limit\fP is set, and PCRE_EXTRA_MATCH_LIMIT is set in
1514     the \fIflags\fP field. If the limit is exceeded, \fBpcre_exec()\fP returns
1515     PCRE_ERROR_MATCHLIMIT.
1516 nigel 75 .P
1517 nigel 87 The \fImatch_limit_recursion\fP field is similar to \fImatch_limit\fP, but
1518     instead of limiting the total number of times that \fBmatch()\fP is called, it
1519     limits the depth of recursion. The recursion depth is a smaller number than the
1520     total number of calls, because not all calls to \fBmatch()\fP are recursive.
1521 ph10 691 This limit is of use only if it is set smaller than \fImatch_limit\fP.
1522 nigel 87 .P
1523 ph10 678 Limiting the recursion depth limits the amount of machine stack that can be
1524     used, or, when PCRE has been compiled to use memory on the heap instead of the
1525 ph10 686 stack, the amount of heap memory that can be used. This limit is not relevant,
1526 ph10 921 and is ignored, when matching is done using JIT compiled code.
1527 nigel 87 .P
1528     The default value for \fImatch_limit_recursion\fP can be set when PCRE is
1529     built; the default default is the same value as the default for
1530     \fImatch_limit\fP. You can override the default by suppling \fBpcre_exec()\fP
1531     with a \fBpcre_extra\fP block in which \fImatch_limit_recursion\fP is set, and
1532     PCRE_EXTRA_MATCH_LIMIT_RECURSION is set in the \fIflags\fP field. If the limit
1533     is exceeded, \fBpcre_exec()\fP returns PCRE_ERROR_RECURSIONLIMIT.
1534     .P
1535 ph10 440 The \fIcallout_data\fP field is used in conjunction with the "callout" feature,
1536     and is described in the
1537 nigel 75 .\" HREF
1538     \fBpcrecallout\fP
1539     .\"
1540     documentation.
1541     .P
1542     The \fItables\fP field is used to pass a character tables pointer to
1543     \fBpcre_exec()\fP; this overrides the value that is stored with the compiled
1544     pattern. A non-NULL value is stored with the compiled pattern only if custom
1545     tables were supplied to \fBpcre_compile()\fP via its \fItableptr\fP argument.
1546     If NULL is passed to \fBpcre_exec()\fP using this mechanism, it forces PCRE's
1547     internal tables to be used. This facility is helpful when re-using patterns
1548     that have been saved after compiling with an external set of tables, because
1549     the external tables might be at a different address when \fBpcre_exec()\fP is
1550     called. See the
1551     .\" HREF
1552     \fBpcreprecompile\fP
1553     .\"
1554     documentation for a discussion of saving compiled patterns for later use.
1555 ph10 510 .P
1556     If PCRE_EXTRA_MARK is set in the \fIflags\fP field, the \fImark\fP field must
1557 ph10 856 be set to point to a suitable variable. If the pattern contains any
1558 ph10 510 backtracking control verbs such as (*MARK:NAME), and the execution ends up with
1559     a name to pass back, a pointer to the name string (zero terminated) is placed
1560     in the variable pointed to by the \fImark\fP field. The names are within the
1561     compiled pattern; if you wish to retain such a name you must copy it before
1562     freeing the memory of a compiled pattern. If there is no name to pass back, the
1563 ph10 856 variable pointed to by the \fImark\fP field is set to NULL. For details of the
1564 ph10 510 backtracking control verbs, see the section entitled
1565     .\" HTML <a href="pcrepattern#backtrackcontrol">
1566     .\" </a>
1567     "Backtracking control"
1568     .\"
1569     in the
1570     .\" HREF
1571     \fBpcrepattern\fP
1572     .\"
1573     documentation.
1574 nigel 75 .
1575 ph10 510 .
1576 ph10 226 .\" HTML <a name="execoptions"></a>
1577 nigel 75 .SS "Option bits for \fBpcre_exec()\fP"
1578     .rs
1579     .sp
1580     The unused bits of the \fIoptions\fP argument for \fBpcre_exec()\fP must be
1581 nigel 91 zero. The only bits that may be set are PCRE_ANCHORED, PCRE_NEWLINE_\fIxxx\fP,
1582 ph10 442 PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY, PCRE_NOTEMPTY_ATSTART,
1583 ph10 921 PCRE_NO_START_OPTIMIZE, PCRE_NO_UTF8_CHECK, PCRE_PARTIAL_HARD, and
1584     PCRE_PARTIAL_SOFT.
1585 ph10 686 .P
1586 ph10 921 If the pattern was successfully studied with one of the just-in-time (JIT)
1587     compile options, the only supported options for JIT execution are
1588     PCRE_NO_UTF8_CHECK, PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY,
1589     PCRE_NOTEMPTY_ATSTART, PCRE_PARTIAL_HARD, and PCRE_PARTIAL_SOFT. If an
1590     unsupported option is used, JIT execution is disabled and the normal
1591     interpretive code in \fBpcre_exec()\fP is run.
1592 nigel 75 .sp
1593     PCRE_ANCHORED
1594     .sp
1595     The PCRE_ANCHORED option limits \fBpcre_exec()\fP to matching at the first
1596     matching position. If a pattern was compiled with PCRE_ANCHORED, or turned out
1597     to be anchored by virtue of its contents, it cannot be made unachored at
1598     matching time.
1599     .sp
1600 ph10 231 PCRE_BSR_ANYCRLF
1601     PCRE_BSR_UNICODE
1602     .sp
1603     These options (which are mutually exclusive) control what the \eR escape
1604     sequence matches. The choice is either to match only CR, LF, or CRLF, or to
1605     match any Unicode newline sequence. These options override the choice that was
1606     made or defaulted when the pattern was compiled.
1607     .sp
1608 nigel 91 PCRE_NEWLINE_CR
1609     PCRE_NEWLINE_LF
1610     PCRE_NEWLINE_CRLF
1611 ph10 150 PCRE_NEWLINE_ANYCRLF
1612 nigel 93 PCRE_NEWLINE_ANY
1613 nigel 91 .sp
1614     These options override the newline definition that was chosen or defaulted when
1615 nigel 93 the pattern was compiled. For details, see the description of
1616     \fBpcre_compile()\fP above. During matching, the newline choice affects the
1617     behaviour of the dot, circumflex, and dollar metacharacters. It may also alter
1618     the way the match position is advanced after a match failure for an unanchored
1619 ph10 227 pattern.
1620 ph10 225 .P
1621 ph10 226 When PCRE_NEWLINE_CRLF, PCRE_NEWLINE_ANYCRLF, or PCRE_NEWLINE_ANY is set, and a
1622     match attempt for an unanchored pattern fails when the current position is at a
1623 ph10 230 CRLF sequence, and the pattern contains no explicit matches for CR or LF
1624 ph10 226 characters, the match position is advanced by two characters instead of one, in
1625     other words, to after the CRLF.
1626     .P
1627 ph10 227 The above rule is a compromise that makes the most common cases work as
1628     expected. For example, if the pattern is .+A (and the PCRE_DOTALL option is not
1629     set), it does not match the string "\er\enA" because, after failing at the
1630     start, it skips both the CR and the LF before retrying. However, the pattern
1631     [\er\en]A does match that string, because it contains an explicit CR or LF
1632 ph10 226 reference, and so advances only by one character after the first failure.
1633     .P
1634 ph10 231 An explicit match for CR of LF is either a literal appearance of one of those
1635     characters, or one of the \er or \en escape sequences. Implicit matches such as
1636 ph10 230 [^X] do not count, nor does \es (which includes CR and LF in the characters
1637     that it matches).
1638     .P
1639 ph10 226 Notwithstanding the above, anomalous effects may still occur when CRLF is a
1640     valid newline sequence and explicit \er or \en escapes appear in the pattern.
1641 nigel 91 .sp
1642 nigel 63 PCRE_NOTBOL
1643 nigel 75 .sp
1644     This option specifies that first character of the subject string is not the
1645     beginning of a line, so the circumflex metacharacter should not match before
1646     it. Setting this without PCRE_MULTILINE (at compile time) causes circumflex
1647     never to match. This option affects only the behaviour of the circumflex
1648     metacharacter. It does not affect \eA.
1649     .sp
1650 nigel 63 PCRE_NOTEOL
1651 nigel 75 .sp
1652     This option specifies that the end of the subject string is not the end of a
1653     line, so the dollar metacharacter should not match it nor (except in multiline
1654     mode) a newline immediately before it. Setting this without PCRE_MULTILINE (at
1655     compile time) causes dollar never to match. This option affects only the
1656     behaviour of the dollar metacharacter. It does not affect \eZ or \ez.
1657     .sp
1658 nigel 63 PCRE_NOTEMPTY
1659 nigel 75 .sp
1660 nigel 63 An empty string is not considered to be a valid match if this option is set. If
1661     there are alternatives in the pattern, they are tried. If all the alternatives
1662     match the empty string, the entire match fails. For example, if the pattern
1663 nigel 75 .sp
1664 nigel 63 a?b?
1665 nigel 75 .sp
1666 ph10 442 is applied to a string not beginning with "a" or "b", it matches an empty
1667 nigel 63 string at the start of the subject. With PCRE_NOTEMPTY set, this match is not
1668     valid, so PCRE searches further into the string for occurrences of "a" or "b".
1669 ph10 442 .sp
1670     PCRE_NOTEMPTY_ATSTART
1671     .sp
1672 ph10 461 This is like PCRE_NOTEMPTY, except that an empty string match that is not at
1673 ph10 442 the start of the subject is permitted. If the pattern is anchored, such a match
1674     can occur only if the pattern contains \eK.
1675 nigel 75 .P
1676 ph10 442 Perl has no direct equivalent of PCRE_NOTEMPTY or PCRE_NOTEMPTY_ATSTART, but it
1677     does make a special case of a pattern match of the empty string within its
1678     \fBsplit()\fP function, and when using the /g modifier. It is possible to
1679     emulate Perl's behaviour after matching a null string by first trying the match
1680     again at the same offset with PCRE_NOTEMPTY_ATSTART and PCRE_ANCHORED, and then
1681     if that fails, by advancing the starting offset (see below) and trying an
1682     ordinary match again. There is some code that demonstrates how to do this in
1683     the
1684 ph10 429 .\" HREF
1685     \fBpcredemo\fP
1686     .\"
1687 ph10 572 sample program. In the most general case, you have to check to see if the
1688     newline convention recognizes CRLF as a newline, and if so, and the current
1689 ph10 566 character is CR followed by LF, advance the starting offset by two characters
1690     instead of one.
1691 nigel 75 .sp
1692 ph10 389 PCRE_NO_START_OPTIMIZE
1693     .sp
1694 ph10 392 There are a number of optimizations that \fBpcre_exec()\fP uses at the start of
1695 ph10 542 a match, in order to speed up the process. For example, if it is known that an
1696     unanchored match must start with a specific character, it searches the subject
1697     for that character, and fails immediately if it cannot find it, without
1698 ph10 545 actually running the main matching function. This means that a special item
1699 ph10 542 such as (*COMMIT) at the start of a pattern is not considered until after a
1700 ph10 548 suitable starting point for the match has been found. When callouts or (*MARK)
1701 ph10 546 items are in use, these "start-up" optimizations can cause them to be skipped
1702     if the pattern is never actually used. The start-up optimizations are in effect
1703     a pre-scan of the subject that takes place before the pattern is run.
1704     .P
1705     The PCRE_NO_START_OPTIMIZE option disables the start-up optimizations, possibly
1706     causing performance to suffer, but ensuring that in cases where the result is
1707     "no match", the callouts do occur, and that items such as (*COMMIT) and (*MARK)
1708 ph10 579 are considered at every possible starting position in the subject string. If
1709     PCRE_NO_START_OPTIMIZE is set at compile time, it cannot be unset at matching
1710 ph10 921 time. The use of PCRE_NO_START_OPTIMIZE disables JIT execution; when it is set,
1711     matching is always done using interpretively.
1712 ph10 576 .P
1713 ph10 546 Setting PCRE_NO_START_OPTIMIZE can change the outcome of a matching operation.
1714     Consider the pattern
1715 ph10 389 .sp
1716 ph10 546 (*COMMIT)ABC
1717     .sp
1718     When this is compiled, PCRE records the fact that a match must start with the
1719 ph10 548 character "A". Suppose the subject string is "DEFABC". The start-up
1720     optimization scans along the subject, finds "A" and runs the first match
1721 ph10 546 attempt from there. The (*COMMIT) item means that the pattern must match the
1722 ph10 548 current starting position, which in this case, it does. However, if the same
1723     match is run with PCRE_NO_START_OPTIMIZE set, the initial scan along the
1724     subject string does not happen. The first match attempt is run starting from
1725 ph10 546 "D" and when this fails, (*COMMIT) prevents any further matches being tried, so
1726     the overall result is "no match". If the pattern is studied, more start-up
1727     optimizations may be used. For example, a minimum length for the subject may be
1728     recorded. Consider the pattern
1729     .sp
1730     (*MARK:A)(X|Y)
1731     .sp
1732 ph10 548 The minimum length for a match is one character. If the subject is "ABC", there
1733     will be attempts to match "ABC", "BC", "C", and then finally an empty string.
1734     If the pattern is studied, the final attempt does not take place, because PCRE
1735     knows that the subject is too short, and so the (*MARK) is never encountered.
1736     In this case, studying the pattern does not affect the overall match result,
1737     which is still "no match", but it does affect the auxiliary information that is
1738 ph10 546 returned.
1739     .sp
1740 nigel 75 PCRE_NO_UTF8_CHECK
1741     .sp
1742     When PCRE_UTF8 is set at compile time, the validity of the subject as a UTF-8
1743     string is automatically checked when \fBpcre_exec()\fP is subsequently called.
1744 ph10 211 The value of \fIstartoffset\fP is also checked to ensure that it points to the
1745     start of a UTF-8 character. There is a discussion about the validity of UTF-8
1746     strings in the
1747     .\" HREF
1748 ph10 856 \fBpcreunicode\fP
1749 ph10 211 .\"
1750 ph10 856 page. If an invalid sequence of bytes is found, \fBpcre_exec()\fP returns the
1751     error PCRE_ERROR_BADUTF8 or, if PCRE_PARTIAL_HARD is set and the problem is a
1752     truncated character at the end of the subject, PCRE_ERROR_SHORTUTF8. In both
1753     cases, information about the precise nature of the error may also be returned
1754     (see the descriptions of these errors in the section entitled \fIError return
1755     values from\fP \fBpcre_exec()\fP
1756 ph10 598 .\" HTML <a href="#errorlist">
1757     .\" </a>
1758     below).
1759     .\"
1760     If \fIstartoffset\fP contains a value that does not point to the start of a
1761     UTF-8 character (or to the end of the subject), PCRE_ERROR_BADUTF8_OFFSET is
1762 ph10 569 returned.
1763 nigel 75 .P
1764     If you already know that your subject is valid, and you want to skip these
1765     checks for performance reasons, you can set the PCRE_NO_UTF8_CHECK option when
1766     calling \fBpcre_exec()\fP. You might want to do this for the second and
1767     subsequent calls to \fBpcre_exec()\fP if you are making repeated calls to find
1768     all the matches in a single subject string. However, you should be sure that
1769 ph10 856 the value of \fIstartoffset\fP points to the start of a character (or the end
1770     of the subject). When PCRE_NO_UTF8_CHECK is set, the effect of passing an
1771     invalid string as a subject or an invalid value of \fIstartoffset\fP is
1772 ph10 567 undefined. Your program may crash.
1773 nigel 75 .sp
1774 ph10 461 PCRE_PARTIAL_HARD
1775 ph10 428 PCRE_PARTIAL_SOFT
1776 nigel 75 .sp
1777 ph10 428 These options turn on the partial matching feature. For backwards
1778     compatibility, PCRE_PARTIAL is a synonym for PCRE_PARTIAL_SOFT. A partial match
1779     occurs if the end of the subject string is reached successfully, but there are
1780     not enough subject characters to complete the match. If this happens when
1781 ph10 553 PCRE_PARTIAL_SOFT (but not PCRE_PARTIAL_HARD) is set, matching continues by
1782     testing any remaining alternatives. Only if no complete match can be found is
1783     PCRE_ERROR_PARTIAL returned instead of PCRE_ERROR_NOMATCH. In other words,
1784     PCRE_PARTIAL_SOFT says that the caller is prepared to handle a partial match,
1785     but only if no complete match can be found.
1786     .P
1787     If PCRE_PARTIAL_HARD is set, it overrides PCRE_PARTIAL_SOFT. In this case, if a
1788     partial match is found, \fBpcre_exec()\fP immediately returns
1789     PCRE_ERROR_PARTIAL, without considering any other alternatives. In other words,
1790 ph10 572 when PCRE_PARTIAL_HARD is set, a partial match is considered to be more
1791 ph10 553 important that an alternative complete match.
1792     .P
1793     In both cases, the portion of the string that was inspected when the partial
1794     match was found is set as the first matching string. There is a more detailed
1795     discussion of partial and multi-segment matching, with examples, in the
1796 nigel 75 .\" HREF
1797     \fBpcrepartial\fP
1798     .\"
1799     documentation.
1800     .
1801 ph10 567 .
1802 nigel 75 .SS "The string to be matched by \fBpcre_exec()\fP"
1803     .rs
1804     .sp
1805     The subject string is passed to \fBpcre_exec()\fP as a pointer in
1806 ph10 856 \fIsubject\fP, a length in bytes in \fIlength\fP, and a starting byte offset
1807 ph10 572 in \fIstartoffset\fP. If this is negative or greater than the length of the
1808     subject, \fBpcre_exec()\fP returns PCRE_ERROR_BADOFFSET. When the starting
1809     offset is zero, the search for a match starts at the beginning of the subject,
1810     and this is by far the most common case. In UTF-8 mode, the byte offset must
1811     point to the start of a UTF-8 character (or the end of the subject). Unlike the
1812     pattern string, the subject may contain binary zero bytes.
1813 nigel 75 .P
1814 nigel 63 A non-zero starting offset is useful when searching for another match in the
1815 nigel 75 same subject by calling \fBpcre_exec()\fP again after a previous success.
1816     Setting \fIstartoffset\fP differs from just passing over a shortened string and
1817 nigel 63 setting PCRE_NOTBOL in the case of a pattern that begins with any kind of
1818     lookbehind. For example, consider the pattern
1819 nigel 75 .sp
1820     \eBiss\eB
1821     .sp
1822     which finds occurrences of "iss" in the middle of words. (\eB matches only if
1823 nigel 63 the current position in the subject is not a word boundary.) When applied to
1824 nigel 75 the string "Mississipi" the first call to \fBpcre_exec()\fP finds the first
1825     occurrence. If \fBpcre_exec()\fP is called again with just the remainder of the
1826     subject, namely "issipi", it does not match, because \eB is always false at the
1827 nigel 63 start of the subject, which is deemed to be a word boundary. However, if
1828 nigel 75 \fBpcre_exec()\fP is passed the entire string again, but with \fIstartoffset\fP
1829 nigel 63 set to 4, it finds the second occurrence of "iss" because it is able to look
1830     behind the starting point to discover that it is preceded by a letter.
1831 nigel 75 .P
1832 ph10 567 Finding all the matches in a subject is tricky when the pattern can match an
1833     empty string. It is possible to emulate Perl's /g behaviour by first trying the
1834     match again at the same offset, with the PCRE_NOTEMPTY_ATSTART and
1835     PCRE_ANCHORED options, and then if that fails, advancing the starting offset
1836     and trying an ordinary match again. There is some code that demonstrates how to
1837     do this in the
1838     .\" HREF
1839     \fBpcredemo\fP
1840     .\"
1841 ph10 572 sample program. In the most general case, you have to check to see if the
1842     newline convention recognizes CRLF as a newline, and if so, and the current
1843 ph10 567 character is CR followed by LF, advance the starting offset by two characters
1844     instead of one.
1845     .P
1846 nigel 63 If a non-zero starting offset is passed when the pattern is anchored, one
1847 nigel 75 attempt to match at the given offset is made. This can only succeed if the
1848 nigel 63 pattern does not require the match to be at the start of the subject.
1849 nigel 75 .
1850 ph10 567 .
1851 nigel 75 .SS "How \fBpcre_exec()\fP returns captured substrings"
1852     .rs
1853     .sp
1854 nigel 63 In general, a pattern matches a certain portion of the subject, and in
1855     addition, further substrings from the subject may be picked out by parts of the
1856     pattern. Following the usage in Jeffrey Friedl's book, this is called
1857     "capturing" in what follows, and the phrase "capturing subpattern" is used for
1858     a fragment of a pattern that picks out a substring. PCRE supports several other
1859     kinds of parenthesized subpattern that do not cause substrings to be captured.
1860 nigel 75 .P
1861 ph10 368 Captured substrings are returned to the caller via a vector of integers whose
1862     address is passed in \fIovector\fP. The number of elements in the vector is
1863     passed in \fIovecsize\fP, which must be a non-negative number. \fBNote\fP: this
1864     argument is NOT the size of \fIovector\fP in bytes.
1865 nigel 75 .P
1866     The first two-thirds of the vector is used to pass back captured substrings,
1867     each substring using a pair of integers. The remaining third of the vector is
1868     used as workspace by \fBpcre_exec()\fP while matching capturing subpatterns,
1869 ph10 368 and is not available for passing back information. The number passed in
1870 nigel 75 \fIovecsize\fP should always be a multiple of three. If it is not, it is
1871     rounded down.
1872     .P
1873     When a match is successful, information about captured substrings is returned
1874     in pairs of integers, starting at the beginning of \fIovector\fP, and
1875 ph10 371 continuing up to two-thirds of its length at the most. The first element of
1876 ph10 368 each pair is set to the byte offset of the first character in a substring, and
1877     the second is set to the byte offset of the first character after the end of a
1878     substring. \fBNote\fP: these values are always byte offsets, even in UTF-8
1879     mode. They are not character counts.
1880 nigel 75 .P
1881 ph10 368 The first pair of integers, \fIovector[0]\fP and \fIovector[1]\fP, identify the
1882     portion of the subject string matched by the entire pattern. The next pair is
1883     used for the first capturing subpattern, and so on. The value returned by
1884     \fBpcre_exec()\fP is one more than the highest numbered pair that has been set.
1885     For example, if two substrings have been captured, the returned value is 3. If
1886     there are no capturing subpatterns, the return value from a successful match is
1887     1, indicating that just the first pair of offsets has been set.
1888     .P
1889 nigel 63 If a capturing subpattern is matched repeatedly, it is the last portion of the
1890 nigel 75 string that it matched that is returned.
1891     .P
1892     If the vector is too small to hold all the captured substring offsets, it is
1893     used as far as possible (up to two-thirds of its length), and the function
1894 ph10 950 returns a value of zero. If neither the actual string matched nor any captured
1895 ph10 686 substrings are of interest, \fBpcre_exec()\fP may be called with \fIovector\fP
1896     passed as NULL and \fIovecsize\fP as zero. However, if the pattern contains
1897     back references and the \fIovector\fP is not big enough to remember the related
1898     substrings, PCRE has to get additional memory for use during matching. Thus it
1899     is usually advisable to supply an \fIovector\fP of reasonable size.
1900 nigel 75 .P
1901 ph10 686 There are some cases where zero is returned (indicating vector overflow) when
1902     in fact the vector is exactly the right size for the final match. For example,
1903     consider the pattern
1904     .sp
1905     (a)(?:(b)c|bd)
1906     .sp
1907     If a vector of 6 elements (allowing for only 1 captured substring) is given
1908     with subject string "abd", \fBpcre_exec()\fP will try to set the second
1909     captured string, thereby recording a vector overflow, before failing to match
1910 ph10 691 "c" and backing up to try the second alternative. The zero return, however,
1911 ph10 686 does correctly indicate that the maximum number of slots (namely 2) have been
1912     filled. In similar cases where there is temporary overflow, but the final
1913     number of used slots is actually less than the maximum, a non-zero value is
1914     returned.
1915     .P
1916 ph10 456 The \fBpcre_fullinfo()\fP function can be used to find out how many capturing
1917 nigel 63 subpatterns there are in a compiled pattern. The smallest size for
1918 nigel 75 \fIovector\fP that will allow for \fIn\fP captured substrings, in addition to
1919     the offsets of the substring matched by the whole pattern, is (\fIn\fP+1)*3.
1920 nigel 91 .P
1921     It is possible for capturing subpattern number \fIn+1\fP to match some part of
1922     the subject when subpattern \fIn\fP has not been used at all. For example, if
1923     the string "abc" is matched against the pattern (a|(z))(bc) the return from the
1924     function is 4, and subpatterns 1 and 3 are matched, but 2 is not. When this
1925     happens, both values in the offset pairs corresponding to unused subpatterns
1926     are set to -1.
1927     .P
1928     Offset values that correspond to unused subpatterns at the end of the
1929     expression are also set to -1. For example, if the string "abc" is matched
1930     against the pattern (abc)(x(yz)?)? subpatterns 2 and 3 are not matched. The
1931     return from the function is 2, because the highest used capturing subpattern
1932 ph10 568 number is 1, and the offsets for for the second and third capturing subpatterns
1933     (assuming the vector is large enough, of course) are set to -1.
1934 nigel 91 .P
1935 ph10 686 \fBNote\fP: Elements in the first two-thirds of \fIovector\fP that do not
1936 ph10 683 correspond to capturing parentheses in the pattern are never changed. That is,
1937     if a pattern contains \fIn\fP capturing parentheses, no more than
1938     \fIovector[0]\fP to \fIovector[2n+1]\fP are set by \fBpcre_exec()\fP. The other
1939     elements (in the first two-thirds) retain whatever values they previously had.
1940 ph10 568 .P
1941 nigel 91 Some convenience functions are provided for extracting the captured substrings
1942     as separate strings. These are described below.
1943 nigel 75 .
1944 ph10 598 .
1945 nigel 77 .\" HTML <a name="errorlist"></a>
1946 nigel 91 .SS "Error return values from \fBpcre_exec()\fP"
1947 nigel 75 .rs
1948     .sp
1949     If \fBpcre_exec()\fP fails, it returns a negative number. The following are
1950 nigel 63 defined in the header file:
1951 nigel 75 .sp
1952 nigel 63 PCRE_ERROR_NOMATCH (-1)
1953 nigel 75 .sp
1954 nigel 63 The subject string did not match the pattern.
1955 nigel 75 .sp
1956 nigel 63 PCRE_ERROR_NULL (-2)
1957 nigel 75 .sp
1958     Either \fIcode\fP or \fIsubject\fP was passed as NULL, or \fIovector\fP was
1959     NULL and \fIovecsize\fP was not zero.
1960     .sp
1961 nigel 63 PCRE_ERROR_BADOPTION (-3)
1962 nigel 75 .sp
1963     An unrecognized bit was set in the \fIoptions\fP argument.
1964     .sp
1965 nigel 63 PCRE_ERROR_BADMAGIC (-4)
1966 nigel 75 .sp
1967 nigel 63 PCRE stores a 4-byte "magic number" at the start of the compiled code, to catch
1968 nigel 75 the case when it is passed a junk pointer and to detect when a pattern that was
1969     compiled in an environment of one endianness is run in an environment with the
1970     other endianness. This is the error that PCRE gives when the magic number is
1971     not present.
1972     .sp
1973 nigel 93 PCRE_ERROR_UNKNOWN_OPCODE (-5)
1974 nigel 75 .sp
1975 nigel 63 While running the pattern match, an unknown item was encountered in the
1976     compiled pattern. This error could be caused by a bug in PCRE or by overwriting
1977     of the compiled pattern.
1978 nigel 75 .sp
1979 nigel 63 PCRE_ERROR_NOMEMORY (-6)
1980 nigel 75 .sp
1981     If a pattern contains back references, but the \fIovector\fP that is passed to
1982     \fBpcre_exec()\fP is not big enough to remember the referenced substrings, PCRE
1983 nigel 63 gets a block of memory at the start of matching to use for this purpose. If the
1984 nigel 75 call via \fBpcre_malloc()\fP fails, this error is given. The memory is
1985     automatically freed at the end of matching.
1986 ph10 531 .P
1987 ph10 535 This error is also given if \fBpcre_stack_malloc()\fP fails in
1988 ph10 531 \fBpcre_exec()\fP. This can happen only when PCRE has been compiled with
1989     \fB--disable-stack-for-recursion\fP.
1990 nigel 75 .sp
1991 nigel 63 PCRE_ERROR_NOSUBSTRING (-7)
1992 nigel 75 .sp
1993     This error is used by the \fBpcre_copy_substring()\fP,
1994     \fBpcre_get_substring()\fP, and \fBpcre_get_substring_list()\fP functions (see
1995     below). It is never returned by \fBpcre_exec()\fP.
1996     .sp
1997 nigel 63 PCRE_ERROR_MATCHLIMIT (-8)
1998 nigel 75 .sp
1999 nigel 87 The backtracking limit, as specified by the \fImatch_limit\fP field in a
2000     \fBpcre_extra\fP structure (or defaulted) was reached. See the description
2001     above.
2002     .sp
2003 nigel 63 PCRE_ERROR_CALLOUT (-9)
2004 nigel 75 .sp
2005     This error is never generated by \fBpcre_exec()\fP itself. It is provided for
2006 nigel 63 use by callout functions that want to yield a distinctive error code. See the
2007 nigel 75 .\" HREF
2008     \fBpcrecallout\fP
2009     .\"
2010     documentation for details.
2011     .sp
2012 nigel 73 PCRE_ERROR_BADUTF8 (-10)
2013 nigel 75 .sp
2014 ph10 598 A string that contains an invalid UTF-8 byte sequence was passed as a subject,
2015     and the PCRE_NO_UTF8_CHECK option was not set. If the size of the output vector
2016     (\fIovecsize\fP) is at least 2, the byte offset to the start of the the invalid
2017     UTF-8 character is placed in the first element, and a reason code is placed in
2018     the second element. The reason codes are listed in the
2019     .\" HTML <a href="#badutf8reasons">
2020     .\" </a>
2021     following section.
2022     .\"
2023     For backward compatibility, if PCRE_PARTIAL_HARD is set and the problem is a
2024     truncated UTF-8 character at the end of the subject (reason codes 1 to 5),
2025     PCRE_ERROR_SHORTUTF8 is returned instead of PCRE_ERROR_BADUTF8.
2026 nigel 75 .sp
2027 nigel 73 PCRE_ERROR_BADUTF8_OFFSET (-11)
2028 nigel 75 .sp
2029 ph10 654 The UTF-8 byte sequence that was passed as a subject was checked and found to
2030 ph10 598 be valid (the PCRE_NO_UTF8_CHECK option was not set), but the value of
2031     \fIstartoffset\fP did not point to the beginning of a UTF-8 character or the
2032 ph10 569 end of the subject.
2033 nigel 75 .sp
2034 nigel 77 PCRE_ERROR_PARTIAL (-12)
2035 nigel 75 .sp
2036     The subject string did not match, but it did match partially. See the
2037     .\" HREF
2038     \fBpcrepartial\fP
2039     .\"
2040     documentation for details of partial matching.
2041     .sp
2042 nigel 77 PCRE_ERROR_BADPARTIAL (-13)
2043 nigel 75 .sp
2044 ph10 426 This code is no longer in use. It was formerly returned when the PCRE_PARTIAL
2045     option was used with a compiled pattern containing items that were not
2046 ph10 461 supported for partial matching. From release 8.00 onwards, there are no
2047 ph10 426 restrictions on partial matching.
2048 nigel 75 .sp
2049 nigel 77 PCRE_ERROR_INTERNAL (-14)
2050 nigel 75 .sp
2051     An unexpected internal error has occurred. This error could be caused by a bug
2052     in PCRE or by overwriting of the compiled pattern.
2053     .sp
2054 nigel 77 PCRE_ERROR_BADCOUNT (-15)
2055 nigel 75 .sp
2056     This error is given if the value of the \fIovecsize\fP argument is negative.
2057 nigel 93 .sp
2058     PCRE_ERROR_RECURSIONLIMIT (-21)
2059     .sp
2060     The internal recursion limit, as specified by the \fImatch_limit_recursion\fP
2061     field in a \fBpcre_extra\fP structure (or defaulted) was reached. See the
2062     description above.
2063     .sp
2064     PCRE_ERROR_BADNEWLINE (-23)
2065     .sp
2066     An invalid combination of PCRE_NEWLINE_\fIxxx\fP options was given.
2067 ph10 567 .sp
2068     PCRE_ERROR_BADOFFSET (-24)
2069     .sp
2070 ph10 572 The value of \fIstartoffset\fP was negative or greater than the length of the
2071 ph10 567 subject, that is, the value in \fIlength\fP.
2072 ph10 569 .sp
2073     PCRE_ERROR_SHORTUTF8 (-25)
2074     .sp
2075 ph10 598 This error is returned instead of PCRE_ERROR_BADUTF8 when the subject string
2076     ends with a truncated UTF-8 character and the PCRE_PARTIAL_HARD option is set.
2077     Information about the failure is returned as for PCRE_ERROR_BADUTF8. It is in
2078     fact sufficient to detect this case, but this special error code for
2079     PCRE_PARTIAL_HARD precedes the implementation of returned information; it is
2080     retained for backwards compatibility.
2081 ph10 642 .sp
2082     PCRE_ERROR_RECURSELOOP (-26)
2083     .sp
2084 ph10 654 This error is returned when \fBpcre_exec()\fP detects a recursion loop within
2085     the pattern. Specifically, it means that either the whole pattern or a
2086     subpattern has been called recursively for the second time at the same position
2087 ph10 642 in the subject string. Some simple patterns that might do this are detected and
2088     faulted at compile time, but more complicated cases, in particular mutual
2089     recursions between two different subpatterns, cannot be detected until run
2090     time.
2091 ph10 678 .sp
2092     PCRE_ERROR_JIT_STACKLIMIT (-27)
2093     .sp
2094 ph10 922 This error is returned when a pattern that was successfully studied using a
2095     JIT compile option is being matched, but the memory available for the
2096     just-in-time processing stack is not large enough. See the
2097 ph10 678 .\" HREF
2098     \fBpcrejit\fP
2099     .\"
2100 ph10 691 documentation for more details.
2101 ph10 856 .sp
2102     PCRE_ERROR_BADMODE (-28)
2103     .sp
2104 ph10 903 This error is given if a pattern that was compiled by the 8-bit library is
2105 ph10 856 passed to a 16-bit library function, or vice versa.
2106     .sp
2107     PCRE_ERROR_BADENDIANNESS (-29)
2108 ph10 903 .sp
2109     This error is given if a pattern that was compiled and saved is reloaded on a
2110     host with different endianness. The utility function
2111     \fBpcre_pattern_to_host_byte_order()\fP can be used to convert such a pattern
2112 ph10 856 so that it runs on the new host.
2113 nigel 93 .P
2114 ph10 197 Error numbers -16 to -20 and -22 are not used by \fBpcre_exec()\fP.
2115 nigel 75 .
2116     .
2117 ph10 598 .\" HTML <a name="badutf8reasons"></a>
2118     .SS "Reason codes for invalid UTF-8 strings"
2119     .rs
2120     .sp
2121 ph10 903 This section applies only to the 8-bit library. The corresponding information
2122 ph10 856 for the 16-bit library is given in the
2123     .\" HREF
2124     \fBpcre16\fP
2125     .\"
2126     page.
2127     .P
2128 ph10 654 When \fBpcre_exec()\fP returns either PCRE_ERROR_BADUTF8 or
2129     PCRE_ERROR_SHORTUTF8, and the size of the output vector (\fIovecsize\fP) is at
2130     least 2, the offset of the start of the invalid UTF-8 character is placed in
2131     the first output vector element (\fIovector[0]\fP) and a reason code is placed
2132 ph10 598 in the second element (\fIovector[1]\fP). The reason codes are given names in
2133     the \fBpcre.h\fP header file:
2134     .sp
2135     PCRE_UTF8_ERR1
2136     PCRE_UTF8_ERR2
2137     PCRE_UTF8_ERR3
2138     PCRE_UTF8_ERR4
2139     PCRE_UTF8_ERR5
2140     .sp
2141 ph10 654 The string ends with a truncated UTF-8 character; the code specifies how many
2142 ph10 598 bytes are missing (1 to 5). Although RFC 3629 restricts UTF-8 characters to be
2143     no longer than 4 bytes, the encoding scheme (originally defined by RFC 2279)
2144 ph10 654 allows for up to 6 bytes, and this is checked first; hence the possibility of
2145 ph10 598 4 or 5 missing bytes.
2146     .sp
2147     PCRE_UTF8_ERR6
2148     PCRE_UTF8_ERR7
2149     PCRE_UTF8_ERR8
2150     PCRE_UTF8_ERR9
2151     PCRE_UTF8_ERR10
2152     .sp
2153 ph10 654 The two most significant bits of the 2nd, 3rd, 4th, 5th, or 6th byte of the
2154 ph10 598 character do not have the binary value 0b10 (that is, either the most
2155     significant bit is 0, or the next bit is 1).
2156 ph10 654 .sp
2157 ph10 598 PCRE_UTF8_ERR11
2158     PCRE_UTF8_ERR12
2159     .sp
2160 ph10 654 A character that is valid by the RFC 2279 rules is either 5 or 6 bytes long;
2161     these code points are excluded by RFC 3629.
2162     .sp
2163 ph10 598 PCRE_UTF8_ERR13
2164     .sp
2165 ph10 654 A 4-byte character has a value greater than 0x10fff; these code points are
2166 ph10 598 excluded by RFC 3629.
2167 ph10 654 .sp
2168 ph10 598 PCRE_UTF8_ERR14
2169     .sp
2170     A 3-byte character has a value in the range 0xd800 to 0xdfff; this range of
2171 ph10 654 code points are reserved by RFC 3629 for use with UTF-16, and so are excluded
2172 ph10 598 from UTF-8.
2173 ph10 654 .sp
2174 ph10 598 PCRE_UTF8_ERR15
2175     PCRE_UTF8_ERR16
2176     PCRE_UTF8_ERR17
2177     PCRE_UTF8_ERR18
2178     PCRE_UTF8_ERR19
2179     .sp
2180 ph10 654 A 2-, 3-, 4-, 5-, or 6-byte character is "overlong", that is, it codes for a
2181     value that can be represented by fewer bytes, which is invalid. For example,
2182 ph10 598 the two bytes 0xc0, 0xae give the value 0x2e, whose correct coding uses just
2183     one byte.
2184     .sp
2185     PCRE_UTF8_ERR20
2186     .sp
2187 ph10 654 The two most significant bits of the first byte of a character have the binary
2188     value 0b10 (that is, the most significant bit is 1 and the second is 0). Such a
2189 ph10 598 byte can only validly occur as the second or subsequent byte of a multi-byte
2190     character.
2191     .sp
2192     PCRE_UTF8_ERR21
2193     .sp
2194     The first byte of a character has the value 0xfe or 0xff. These values can
2195     never occur in a valid UTF-8 string.
2196     .
2197     .
2198 nigel 75 .SH "EXTRACTING CAPTURED SUBSTRINGS BY NUMBER"
2199 nigel 63 .rs
2200     .sp
2201 nigel 75 .B int pcre_copy_substring(const char *\fIsubject\fP, int *\fIovector\fP,
2202 nigel 63 .ti +5n
2203 nigel 75 .B int \fIstringcount\fP, int \fIstringnumber\fP, char *\fIbuffer\fP,
2204 nigel 63 .ti +5n
2205 nigel 75 .B int \fIbuffersize\fP);
2206 nigel 63 .PP
2207 nigel 75 .B int pcre_get_substring(const char *\fIsubject\fP, int *\fIovector\fP,
2208 nigel 63 .ti +5n
2209 nigel 75 .B int \fIstringcount\fP, int \fIstringnumber\fP,
2210 nigel 63 .ti +5n
2211 nigel 75 .B const char **\fIstringptr\fP);
2212 nigel 63 .PP
2213 nigel 75 .B int pcre_get_substring_list(const char *\fIsubject\fP,
2214 nigel 63 .ti +5n
2215 nigel 75 .B int *\fIovector\fP, int \fIstringcount\fP, "const char ***\fIlistptr\fP);"
2216 nigel 63 .PP
2217     Captured substrings can be accessed directly by using the offsets returned by
2218 nigel 75 \fBpcre_exec()\fP in \fIovector\fP. For convenience, the functions
2219     \fBpcre_copy_substring()\fP, \fBpcre_get_substring()\fP, and
2220     \fBpcre_get_substring_list()\fP are provided for extracting captured substrings
2221 nigel 63 as new, separate, zero-terminated strings. These functions identify substrings
2222     by number. The next section describes functions for extracting named
2223 nigel 91 substrings.
2224 nigel 75 .P
2225 nigel 91 A substring that contains a binary zero is correctly extracted and has a
2226     further zero added on the end, but the result is not, of course, a C string.
2227     However, you can process such a string by referring to the length that is
2228     returned by \fBpcre_copy_substring()\fP and \fBpcre_get_substring()\fP.
2229     Unfortunately, the interface to \fBpcre_get_substring_list()\fP is not adequate
2230     for handling strings containing binary zeros, because the end of the final
2231     string is not independently indicated.
2232     .P
2233 nigel 63 The first three arguments are the same for all three of these functions:
2234 nigel 75 \fIsubject\fP is the subject string that has just been successfully matched,
2235     \fIovector\fP is a pointer to the vector of integer offsets that was passed to
2236     \fBpcre_exec()\fP, and \fIstringcount\fP is the number of substrings that were
2237 nigel 63 captured by the match, including the substring that matched the entire regular
2238 nigel 75 expression. This is the value returned by \fBpcre_exec()\fP if it is greater
2239     than zero. If \fBpcre_exec()\fP returned zero, indicating that it ran out of
2240     space in \fIovector\fP, the value passed as \fIstringcount\fP should be the
2241     number of elements in the vector divided by three.
2242     .P
2243     The functions \fBpcre_copy_substring()\fP and \fBpcre_get_substring()\fP
2244     extract a single substring, whose number is given as \fIstringnumber\fP. A
2245     value of zero extracts the substring that matched the entire pattern, whereas
2246     higher values extract the captured substrings. For \fBpcre_copy_substring()\fP,
2247     the string is placed in \fIbuffer\fP, whose length is given by
2248     \fIbuffersize\fP, while for \fBpcre_get_substring()\fP a new block of memory is
2249     obtained via \fBpcre_malloc\fP, and its address is returned via
2250     \fIstringptr\fP. The yield of the function is the length of the string, not
2251 nigel 93 including the terminating zero, or one of these error codes:
2252 nigel 75 .sp
2253 nigel 63 PCRE_ERROR_NOMEMORY (-6)
2254 nigel 75 .sp
2255     The buffer was too small for \fBpcre_copy_substring()\fP, or the attempt to get
2256     memory failed for \fBpcre_get_substring()\fP.
2257     .sp
2258 nigel 63 PCRE_ERROR_NOSUBSTRING (-7)
2259 nigel 75 .sp
2260     There is no substring whose number is \fIstringnumber\fP.
2261     .P
2262     The \fBpcre_get_substring_list()\fP function extracts all available substrings
2263 nigel 63 and builds a list of pointers to them. All this is done in a single block of
2264 nigel 75 memory that is obtained via \fBpcre_malloc\fP. The address of the memory block
2265     is returned via \fIlistptr\fP, which is also the start of the list of string
2266 nigel 63 pointers. The end of the list is marked by a NULL pointer. The yield of the
2267 nigel 93 function is zero if all went well, or the error code
2268 nigel 75 .sp
2269 nigel 63 PCRE_ERROR_NOMEMORY (-6)
2270 nigel 75 .sp
2271 nigel 63 if the attempt to get the memory block failed.
2272 nigel 75 .P
2273 nigel 63 When any of these functions encounter a substring that is unset, which can
2274 nigel 75 happen when capturing subpattern number \fIn+1\fP matches some part of the
2275     subject, but subpattern \fIn\fP has not been used at all, they return an empty
2276 nigel 63 string. This can be distinguished from a genuine zero-length substring by
2277 nigel 75 inspecting the appropriate offset in \fIovector\fP, which is negative for unset
2278 nigel 63 substrings.
2279 nigel 75 .P
2280     The two convenience functions \fBpcre_free_substring()\fP and
2281     \fBpcre_free_substring_list()\fP can be used to free the memory returned by
2282     a previous call of \fBpcre_get_substring()\fP or
2283     \fBpcre_get_substring_list()\fP, respectively. They do nothing more than call
2284     the function pointed to by \fBpcre_free\fP, which of course could be called
2285 nigel 63 directly from a C program. However, PCRE is used in some situations where it is
2286 nigel 91 linked via a special interface to another programming language that cannot use
2287 nigel 75 \fBpcre_free\fP directly; it is for these cases that the functions are
2288 nigel 63 provided.
2289 nigel 75 .
2290     .
2291     .SH "EXTRACTING CAPTURED SUBSTRINGS BY NAME"
2292 nigel 63 .rs
2293     .sp
2294 nigel 75 .B int pcre_get_stringnumber(const pcre *\fIcode\fP,
2295 nigel 63 .ti +5n
2296 nigel 75 .B const char *\fIname\fP);
2297 nigel 63 .PP
2298 nigel 75 .B int pcre_copy_named_substring(const pcre *\fIcode\fP,
2299 nigel 63 .ti +5n
2300 nigel 75 .B const char *\fIsubject\fP, int *\fIovector\fP,
2301     .ti +5n
2302     .B int \fIstringcount\fP, const char *\fIstringname\fP,
2303     .ti +5n
2304     .B char *\fIbuffer\fP, int \fIbuffersize\fP);
2305 nigel 63 .PP
2306 nigel 75 .B int pcre_get_named_substring(const pcre *\fIcode\fP,
2307 nigel 63 .ti +5n
2308 nigel 75 .B const char *\fIsubject\fP, int *\fIovector\fP,
2309 nigel 63 .ti +5n
2310 nigel 75 .B int \fIstringcount\fP, const char *\fIstringname\fP,
2311 nigel 63 .ti +5n
2312 nigel 75 .B const char **\fIstringptr\fP);
2313 nigel 63 .PP
2314 nigel 75 To extract a substring by name, you first have to find associated number.
2315     For example, for this pattern
2316     .sp
2317 nigel 93 (a+)b(?<xxx>\ed+)...
2318 nigel 75 .sp
2319 nigel 91 the number of the subpattern called "xxx" is 2. If the name is known to be
2320     unique (PCRE_DUPNAMES was not set), you can find the number from the name by
2321     calling \fBpcre_get_stringnumber()\fP. The first argument is the compiled
2322     pattern, and the second is the name. The yield of the function is the
2323 nigel 75 subpattern number, or PCRE_ERROR_NOSUBSTRING (-7) if there is no subpattern of
2324     that name.
2325     .P
2326     Given the number, you can extract the substring directly, or use one of the
2327     functions described in the previous section. For convenience, there are also
2328     two functions that do the whole job.
2329     .P
2330 nigel 91 Most of the arguments of \fBpcre_copy_named_substring()\fP and
2331     \fBpcre_get_named_substring()\fP are the same as those for the similarly named
2332 nigel 75 functions that extract by number. As these are described in the previous
2333     section, they are not re-described here. There are just two differences:
2334     .P
2335 nigel 63 First, instead of a substring number, a substring name is given. Second, there
2336     is an extra argument, given at the start, which is a pointer to the compiled
2337     pattern. This is needed in order to gain access to the name-to-number
2338     translation table.
2339 nigel 75 .P
2340     These functions call \fBpcre_get_stringnumber()\fP, and if it succeeds, they
2341 ph10 127 then call \fBpcre_copy_substring()\fP or \fBpcre_get_substring()\fP, as
2342     appropriate. \fBNOTE:\fP If PCRE_DUPNAMES is set and there are duplicate names,
2343 ph10 128 the behaviour may not be what you want (see the next section).
2344 ph10 385 .P
2345 ph10 457 \fBWarning:\fP If the pattern uses the (?| feature to set up multiple
2346     subpatterns with the same number, as described in the
2347     .\" HTML <a href="pcrepattern.html#dupsubpatternnumber">
2348     .\" </a>
2349     section on duplicate subpattern numbers
2350     .\"
2351     in the
2352     .\" HREF
2353     \fBpcrepattern\fP
2354     .\"
2355     page, you cannot use names to distinguish the different subpatterns, because
2356     names are not included in the compiled code. The matching process uses only
2357     numbers. For this reason, the use of different names for subpatterns of the
2358     same number causes an error at compile time.
2359 nigel 77 .
2360 ph10 686 .
2361 nigel 91 .SH "DUPLICATE SUBPATTERN NAMES"
2362     .rs
2363     .sp
2364     .B int pcre_get_stringtable_entries(const pcre *\fIcode\fP,
2365     .ti +5n
2366     .B const char *\fIname\fP, char **\fIfirst\fP, char **\fIlast\fP);
2367     .PP
2368     When a pattern is compiled with the PCRE_DUPNAMES option, names for subpatterns
2369 ph10 457 are not required to be unique. (Duplicate names are always allowed for
2370     subpatterns with the same number, created by using the (?| feature. Indeed, if
2371     such subpatterns are named, they are required to use the same names.)
2372     .P
2373     Normally, patterns with duplicate names are such that in any one match, only
2374     one of the named subpatterns participates. An example is shown in the
2375 nigel 91 .\" HREF
2376     \fBpcrepattern\fP
2377     .\"
2378 ph10 208 documentation.
2379 ph10 203 .P
2380     When duplicates are present, \fBpcre_copy_named_substring()\fP and
2381     \fBpcre_get_named_substring()\fP return the first substring corresponding to
2382     the given name that is set. If none are set, PCRE_ERROR_NOSUBSTRING (-7) is
2383     returned; no data is returned. The \fBpcre_get_stringnumber()\fP function
2384     returns one of the numbers that are associated with the name, but it is not
2385     defined which it is.
2386     .P
2387 nigel 91 If you want to get full details of all captured substrings for a given name,
2388     you must use the \fBpcre_get_stringtable_entries()\fP function. The first
2389     argument is the compiled pattern, and the second is the name. The third and
2390     fourth are pointers to variables which are updated by the function. After it
2391     has run, they point to the first and last entries in the name-to-number table
2392     for the given name. The function itself returns the length of each entry, or
2393 nigel 93 PCRE_ERROR_NOSUBSTRING (-7) if there are none. The format of the table is
2394 ph10 598 described above in the section entitled \fIInformation about a pattern\fP
2395     .\" HTML <a href="#infoaboutpattern">
2396     .\" </a>
2397     above.
2398     .\"
2399 nigel 93 Given all the relevant entries for the name, you can extract each of their
2400     numbers, and hence the captured data, if any.
2401 nigel 91 .
2402     .
2403 nigel 77 .SH "FINDING ALL POSSIBLE MATCHES"
2404     .rs
2405     .sp
2406     The traditional matching function uses a similar algorithm to Perl, which stops
2407     when it finds the first match, starting at a given point in the subject. If you
2408     want to find all possible matches, or the longest possible match, consider
2409     using the alternative matching function (see below) instead. If you cannot use
2410     the alternative function, but still need to find all possible matches, you
2411     can kludge it up by making use of the callout facility, which is described in
2412     the
2413     .\" HREF
2414     \fBpcrecallout\fP
2415     .\"
2416     documentation.
2417 nigel 75 .P
2418 nigel 77 What you have to do is to insert a callout right at the end of the pattern.
2419     When your callout function is called, extract and save the current matched
2420     substring. Then return 1, which forces \fBpcre_exec()\fP to backtrack and try
2421     other alternatives. Ultimately, when it runs out of matches, \fBpcre_exec()\fP
2422     will yield PCRE_ERROR_NOMATCH.
2423     .
2424     .
2425 ph10 901 .SH "OBTAINING AN ESTIMATE OF STACK USAGE"
2426     .rs
2427     .sp
2428     Matching certain patterns using \fBpcre_exec()\fP can use a lot of process
2429 ph10 903 stack, which in certain environments can be rather limited in size. Some users
2430     find it helpful to have an estimate of the amount of stack that is used by
2431 ph10 901 \fBpcre_exec()\fP, to help them set recursion limits, as described in the
2432     .\" HREF
2433     \fBpcrestack\fP
2434     .\"
2435 ph10 903 documentation. The estimate that is output by \fBpcretest\fP when called with
2436     the \fB-m\fP and \fB-C\fP options is obtained by calling \fBpcre_exec\fP with
2437 ph10 901 the values NULL, NULL, NULL, -999, and -999 for its first five arguments.
2438     .P
2439     Normally, if its first argument is NULL, \fBpcre_exec()\fP immediately returns
2440     the negative error code PCRE_ERROR_NULL, but with this special combination of
2441     arguments, it returns instead a negative number whose absolute value is the
2442     approximate stack frame size in bytes. (A negative number is used so that it is
2443     clear that no match has happened.) The value is approximate because in some
2444 ph10 903 cases, recursive calls to \fBpcre_exec()\fP occur when there are one or two
2445 ph10 901 additional variables on the stack.
2446     .P
2447 ph10 903 If PCRE has been compiled to use the heap instead of the stack for recursion,
2448 ph10 901 the value returned is the size of each block that is obtained from the heap.
2449     .
2450     .
2451 nigel 77 .\" HTML <a name="dfamatch"></a>
2452     .SH "MATCHING A PATTERN: THE ALTERNATIVE FUNCTION"
2453     .rs
2454     .sp
2455     .B int pcre_dfa_exec(const pcre *\fIcode\fP, "const pcre_extra *\fIextra\fP,"
2456     .ti +5n
2457     .B "const char *\fIsubject\fP," int \fIlength\fP, int \fIstartoffset\fP,
2458     .ti +5n
2459     .B int \fIoptions\fP, int *\fIovector\fP, int \fIovecsize\fP,
2460     .ti +5n
2461     .B int *\fIworkspace\fP, int \fIwscount\fP);
2462     .P
2463     The function \fBpcre_dfa_exec()\fP is called to match a subject string against
2464 nigel 93 a compiled pattern, using a matching algorithm that scans the subject string
2465     just once, and does not backtrack. This has different characteristics to the
2466     normal algorithm, and is not compatible with Perl. Some of the features of PCRE
2467     patterns are not supported. Nevertheless, there are times when this kind of
2468 ph10 461 matching can be useful. For a discussion of the two matching algorithms, and a
2469 ph10 435 list of features that \fBpcre_dfa_exec()\fP does not support, see the
2470 nigel 77 .\" HREF
2471     \fBpcrematching\fP
2472     .\"
2473     documentation.
2474     .P
2475     The arguments for the \fBpcre_dfa_exec()\fP function are the same as for
2476     \fBpcre_exec()\fP, plus two extras. The \fIovector\fP argument is used in a
2477     different way, and this is described below. The other common arguments are used
2478     in the same way as for \fBpcre_exec()\fP, so their description is not repeated
2479     here.
2480     .P
2481     The two additional arguments provide workspace for the function. The workspace
2482     vector should contain at least 20 elements. It is used for keeping track of
2483     multiple paths through the pattern tree. More workspace will be needed for
2484 nigel 91 patterns and subjects where there are a lot of potential matches.
2485 nigel 77 .P
2486 nigel 87 Here is an example of a simple call to \fBpcre_dfa_exec()\fP:
2487 nigel 77 .sp
2488     int rc;
2489     int ovector[10];
2490     int wspace[20];
2491 nigel 87 rc = pcre_dfa_exec(
2492 nigel 77 re, /* result of pcre_compile() */
2493     NULL, /* we didn't study the pattern */
2494     "some string", /* the subject string */
2495     11, /* the length of the subject string */
2496     0, /* start at offset 0 in the subject */
2497     0, /* default options */
2498     ovector, /* vector of integers for substring information */
2499     10, /* number of elements (NOT size in bytes) */
2500     wspace, /* working space vector */
2501     20); /* number of elements (NOT size in bytes) */
2502     .
2503     .SS "Option bits for \fBpcre_dfa_exec()\fP"
2504     .rs
2505     .sp
2506     The unused bits of the \fIoptions\fP argument for \fBpcre_dfa_exec()\fP must be
2507 nigel 91 zero. The only bits that may be set are PCRE_ANCHORED, PCRE_NEWLINE_\fIxxx\fP,
2508 ph10 442 PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY, PCRE_NOTEMPTY_ATSTART,
2509 ph10 542 PCRE_NO_UTF8_CHECK, PCRE_BSR_ANYCRLF, PCRE_BSR_UNICODE, PCRE_NO_START_OPTIMIZE,
2510     PCRE_PARTIAL_HARD, PCRE_PARTIAL_SOFT, PCRE_DFA_SHORTEST, and PCRE_DFA_RESTART.
2511     All but the last four of these are exactly the same as for \fBpcre_exec()\fP,
2512     so their description is not repeated here.
2513 nigel 77 .sp
2514 ph10 428 PCRE_PARTIAL_HARD
2515 ph10 461 PCRE_PARTIAL_SOFT
2516 nigel 77 .sp
2517 ph10 428 These have the same general effect as they do for \fBpcre_exec()\fP, but the
2518     details are slightly different. When PCRE_PARTIAL_HARD is set for
2519     \fBpcre_dfa_exec()\fP, it returns PCRE_ERROR_PARTIAL if the end of the subject
2520     is reached and there is still at least one matching possibility that requires
2521     additional characters. This happens even if some complete matches have also
2522     been found. When PCRE_PARTIAL_SOFT is set, the return code PCRE_ERROR_NOMATCH
2523     is converted into PCRE_ERROR_PARTIAL if the end of the subject is reached,
2524     there have been no complete matches, but there is still at least one matching
2525 ph10 435 possibility. The portion of the string that was inspected when the longest
2526     partial match was found is set as the first matching string in both cases.
2527 ph10 553 There is a more detailed discussion of partial and multi-segment matching, with
2528     examples, in the
2529     .\" HREF
2530     \fBpcrepartial\fP
2531     .\"
2532     documentation.
2533 nigel 77 .sp
2534     PCRE_DFA_SHORTEST
2535     .sp
2536     Setting the PCRE_DFA_SHORTEST option causes the matching algorithm to stop as
2537 nigel 93 soon as it has found one match. Because of the way the alternative algorithm
2538     works, this is necessarily the shortest possible match at the first possible
2539     matching point in the subject string.
2540 nigel 77 .sp
2541     PCRE_DFA_RESTART
2542     .sp
2543 ph10 428 When \fBpcre_dfa_exec()\fP returns a partial match, it is possible to call it
2544     again, with additional subject characters, and have it continue with the same
2545     match. The PCRE_DFA_RESTART option requests this action; when it is set, the
2546     \fIworkspace\fP and \fIwscount\fP options must reference the same vector as
2547     before because data about the match so far is left in them after a partial
2548     match. There is more discussion of this facility in the
2549 nigel 77 .\" HREF
2550     \fBpcrepartial\fP
2551     .\"
2552     documentation.
2553     .
2554 ph10 598 .
2555 nigel 77 .SS "Successful returns from \fBpcre_dfa_exec()\fP"
2556     .rs
2557     .sp
2558     When \fBpcre_dfa_exec()\fP succeeds, it may have matched more than one
2559     substring in the subject. Note, however, that all the matches from one run of
2560     the function start at the same point in the subject. The shorter matches are
2561     all initial substrings of the longer matches. For example, if the pattern
2562     .sp
2563     <.*>
2564     .sp
2565     is matched against the string
2566     .sp
2567     This is <something> <something else> <something further> no more
2568     .sp
2569     the three matched strings are
2570     .sp
2571     <something>
2572     <something> <something else>
2573     <something> <something else> <something further>
2574     .sp
2575     On success, the yield of the function is a number greater than zero, which is
2576     the number of matched substrings. The substrings themselves are returned in
2577     \fIovector\fP. Each string uses two elements; the first is the offset to the
2578 nigel 93 start, and the second is the offset to the end. In fact, all the strings have
2579     the same start offset. (Space could have been saved by giving this only once,
2580     but it was decided to retain some compatibility with the way \fBpcre_exec()\fP
2581     returns data, even though the meaning of the strings is different.)
2582 nigel 77 .P
2583     The strings are returned in reverse order of length; that is, the longest
2584     matching string is given first. If there were too many matches to fit into
2585     \fIovector\fP, the yield of the function is zero, and the vector is filled with
2586 ph10 691 the longest matches. Unlike \fBpcre_exec()\fP, \fBpcre_dfa_exec()\fP can use
2587 ph10 683 the entire \fIovector\fP for returning matched strings.
2588 nigel 77 .
2589 ph10 598 .
2590 nigel 77 .SS "Error returns from \fBpcre_dfa_exec()\fP"
2591     .rs
2592     .sp
2593     The \fBpcre_dfa_exec()\fP function returns a negative number when it fails.
2594     Many of the errors are the same as for \fBpcre_exec()\fP, and these are
2595     described
2596     .\" HTML <a href="#errorlist">
2597     .\" </a>
2598     above.
2599     .\"
2600     There are in addition the following errors that are specific to
2601     \fBpcre_dfa_exec()\fP:
2602     .sp
2603     PCRE_ERROR_DFA_UITEM (-16)
2604     .sp
2605     This return is given if \fBpcre_dfa_exec()\fP encounters an item in the pattern
2606     that it does not support, for instance, the use of \eC or a back reference.
2607     .sp
2608     PCRE_ERROR_DFA_UCOND (-17)
2609     .sp
2610 nigel 93 This return is given if \fBpcre_dfa_exec()\fP encounters a condition item that
2611     uses a back reference for the condition, or a test for recursion in a specific
2612     group. These are not supported.
2613 nigel 77 .sp
2614     PCRE_ERROR_DFA_UMLIMIT (-18)
2615     .sp
2616     This return is given if \fBpcre_dfa_exec()\fP is called with an \fIextra\fP
2617 ph10 678 block that contains a setting of the \fImatch_limit\fP or
2618     \fImatch_limit_recursion\fP fields. This is not supported (these fields are
2619     meaningless for DFA matching).
2620 nigel 77 .sp
2621     PCRE_ERROR_DFA_WSSIZE (-19)
2622     .sp
2623     This return is given if \fBpcre_dfa_exec()\fP runs out of space in the
2624     \fIworkspace\fP vector.
2625     .sp
2626     PCRE_ERROR_DFA_RECURSE (-20)
2627     .sp
2628     When a recursive subpattern is processed, the matching function calls itself
2629     recursively, using private vectors for \fIovector\fP and \fIworkspace\fP. This
2630     error is given if the output vector is not large enough. This should be
2631     extremely rare, as a vector of size 1000 is used.
2632 nigel 93 .
2633     .
2634     .SH "SEE ALSO"
2635     .rs
2636     .sp
2637 ph10 856 \fBpcre16\fP(3), \fBpcrebuild\fP(3), \fBpcrecallout\fP(3), \fBpcrecpp(3)\fP(3),
2638 nigel 93 \fBpcrematching\fP(3), \fBpcrepartial\fP(3), \fBpcreposix\fP(3),
2639     \fBpcreprecompile\fP(3), \fBpcresample\fP(3), \fBpcrestack\fP(3).
2640 ph10 99 .
2641     .
2642     .SH AUTHOR
2643     .rs
2644     .sp
2645     .nf
2646     Philip Hazel
2647     University Computing Service
2648     Cambridge CB2 3QH, England.
2649     .fi
2650     .
2651     .
2652     .SH REVISION
2653     .rs
2654     .sp
2655     .nf
2656 ph10 932 Last updated: 24 February 2012
2657 ph10 856 Copyright (c) 1997-2012 University of Cambridge.
2658 ph10 99 .fi

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