/[pcre]/code/trunk/doc/pcreapi.3
ViewVC logotype

Contents of /code/trunk/doc/pcreapi.3

Parent Directory Parent Directory | Revision Log Revision Log


Revision 745 - (hide annotations) (download)
Mon Nov 14 11:41:03 2011 UTC (2 years, 10 months ago) by ph10
File size: 110283 byte(s)
Small tidies, and documentation update for JavaScript \x, \u, \U support.

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

Properties

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

webmaster@exim.org
ViewVC Help
Powered by ViewVC 1.1.12