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1 nigel 79 .TH PCREAPI 3
2 nigel 63 .SH NAME
3     PCRE - Perl-compatible regular expressions
4 nigel 75 .SH "PCRE NATIVE API"
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 nigel 75 .B int pcre_exec(const pcre *\fIcode\fP, "const pcre_extra *\fIextra\fP,"
29 nigel 63 .ti +5n
30 nigel 75 .B "const char *\fIsubject\fP," int \fIlength\fP, int \fIstartoffset\fP,
31 nigel 63 .ti +5n
32 nigel 75 .B int \fIoptions\fP, int *\fIovector\fP, int \fIovecsize\fP);
33 nigel 63 .PP
34 nigel 77 .B int pcre_dfa_exec(const pcre *\fIcode\fP, "const pcre_extra *\fIextra\fP,"
35     .ti +5n
36     .B "const char *\fIsubject\fP," int \fIlength\fP, int \fIstartoffset\fP,
37     .ti +5n
38     .B int \fIoptions\fP, int *\fIovector\fP, int \fIovecsize\fP,
39     .ti +5n
40     .B int *\fIworkspace\fP, int \fIwscount\fP);
41     .PP
42 nigel 75 .B int pcre_copy_named_substring(const pcre *\fIcode\fP,
43 nigel 63 .ti +5n
44 nigel 75 .B const char *\fIsubject\fP, int *\fIovector\fP,
45 nigel 63 .ti +5n
46 nigel 75 .B int \fIstringcount\fP, const char *\fIstringname\fP,
47 nigel 63 .ti +5n
48 nigel 75 .B char *\fIbuffer\fP, int \fIbuffersize\fP);
49 nigel 63 .PP
50 nigel 75 .B int pcre_copy_substring(const char *\fIsubject\fP, int *\fIovector\fP,
51 nigel 63 .ti +5n
52 nigel 75 .B int \fIstringcount\fP, int \fIstringnumber\fP, char *\fIbuffer\fP,
53 nigel 63 .ti +5n
54 nigel 75 .B int \fIbuffersize\fP);
55 nigel 63 .PP
56 nigel 75 .B int pcre_get_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 const char **\fIstringptr\fP);
63 nigel 63 .PP
64 nigel 75 .B int pcre_get_stringnumber(const pcre *\fIcode\fP,
65 nigel 63 .ti +5n
66 nigel 75 .B const char *\fIname\fP);
67 nigel 63 .PP
68 nigel 91 .B int pcre_get_stringtable_entries(const pcre *\fIcode\fP,
69     .ti +5n
70     .B const char *\fIname\fP, char **\fIfirst\fP, char **\fIlast\fP);
71     .PP
72 nigel 75 .B int pcre_get_substring(const char *\fIsubject\fP, int *\fIovector\fP,
73 nigel 63 .ti +5n
74 nigel 75 .B int \fIstringcount\fP, int \fIstringnumber\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_substring_list(const char *\fIsubject\fP,
79 nigel 63 .ti +5n
80 nigel 75 .B int *\fIovector\fP, int \fIstringcount\fP, "const char ***\fIlistptr\fP);"
81 nigel 63 .PP
82 nigel 75 .B void pcre_free_substring(const char *\fIstringptr\fP);
83 nigel 63 .PP
84 nigel 75 .B void pcre_free_substring_list(const char **\fIstringptr\fP);
85 nigel 63 .PP
86     .B const unsigned char *pcre_maketables(void);
87     .PP
88 nigel 75 .B int pcre_fullinfo(const pcre *\fIcode\fP, "const pcre_extra *\fIextra\fP,"
89 nigel 63 .ti +5n
90 nigel 75 .B int \fIwhat\fP, void *\fIwhere\fP);
91 nigel 63 .PP
92 nigel 75 .B int pcre_info(const pcre *\fIcode\fP, int *\fIoptptr\fP, int
93     .B *\fIfirstcharptr\fP);
94 nigel 63 .PP
95 nigel 77 .B int pcre_refcount(pcre *\fIcode\fP, int \fIadjust\fP);
96     .PP
97 nigel 75 .B int pcre_config(int \fIwhat\fP, void *\fIwhere\fP);
98 nigel 63 .PP
99     .B char *pcre_version(void);
100     .PP
101     .B void *(*pcre_malloc)(size_t);
102     .PP
103     .B void (*pcre_free)(void *);
104     .PP
105 nigel 73 .B void *(*pcre_stack_malloc)(size_t);
106     .PP
107     .B void (*pcre_stack_free)(void *);
108     .PP
109 nigel 63 .B int (*pcre_callout)(pcre_callout_block *);
110 nigel 75 .
111     .
112     .SH "PCRE API OVERVIEW"
113 nigel 63 .rs
114     .sp
115 nigel 93 PCRE has its own native API, which is described in this document. There are
116     also some wrapper functions that correspond to the POSIX regular expression
117 nigel 77 API. These are described in the
118 nigel 75 .\" HREF
119     \fBpcreposix\fP
120     .\"
121 nigel 77 documentation. Both of these APIs define a set of C function calls. A C++
122     wrapper is distributed with PCRE. It is documented in the
123     .\" HREF
124     \fBpcrecpp\fP
125     .\"
126     page.
127 nigel 75 .P
128 nigel 77 The native API C function prototypes are defined in the header file
129     \fBpcre.h\fP, and on Unix systems the library itself is called \fBlibpcre\fP.
130     It can normally be accessed by adding \fB-lpcre\fP to the command for linking
131     an application that uses PCRE. The header file defines the macros PCRE_MAJOR
132     and PCRE_MINOR to contain the major and minor release numbers for the library.
133 nigel 75 Applications can use these to include support for different releases of PCRE.
134     .P
135 ph10 525 In a Windows environment, if you want to statically link an application program
136     against a non-dll \fBpcre.a\fP file, you must define PCRE_STATIC before
137 ph10 526 including \fBpcre.h\fP or \fBpcrecpp.h\fP, because otherwise the
138     \fBpcre_malloc()\fP and \fBpcre_free()\fP exported functions will be declared
139 ph10 525 \fB__declspec(dllimport)\fP, with unwanted results.
140     .P
141 nigel 77 The functions \fBpcre_compile()\fP, \fBpcre_compile2()\fP, \fBpcre_study()\fP,
142     and \fBpcre_exec()\fP are used for compiling and matching regular expressions
143     in a Perl-compatible manner. A sample program that demonstrates the simplest
144 ph10 429 way of using them is provided in the file called \fIpcredemo.c\fP in the PCRE
145     source distribution. A listing of this program is given in the
146 nigel 75 .\" HREF
147 ph10 429 \fBpcredemo\fP
148     .\"
149     documentation, and the
150     .\" HREF
151 nigel 75 \fBpcresample\fP
152     .\"
153 ph10 312 documentation describes how to compile and run it.
154 nigel 75 .P
155 nigel 77 A second matching function, \fBpcre_dfa_exec()\fP, which is not
156     Perl-compatible, is also provided. This uses a different algorithm for the
157 nigel 91 matching. The alternative algorithm finds all possible matches (at a given
158 ph10 435 point in the subject), and scans the subject just once (unless there are
159     lookbehind assertions). However, this algorithm does not return captured
160     substrings. A description of the two matching algorithms and their advantages
161     and disadvantages is given in the
162 nigel 77 .\" HREF
163     \fBpcrematching\fP
164     .\"
165     documentation.
166     .P
167 nigel 75 In addition to the main compiling and matching functions, there are convenience
168 nigel 77 functions for extracting captured substrings from a subject string that is
169     matched by \fBpcre_exec()\fP. They are:
170 nigel 75 .sp
171     \fBpcre_copy_substring()\fP
172     \fBpcre_copy_named_substring()\fP
173     \fBpcre_get_substring()\fP
174     \fBpcre_get_named_substring()\fP
175     \fBpcre_get_substring_list()\fP
176     \fBpcre_get_stringnumber()\fP
177 nigel 91 \fBpcre_get_stringtable_entries()\fP
178 nigel 75 .sp
179     \fBpcre_free_substring()\fP and \fBpcre_free_substring_list()\fP are also
180 nigel 63 provided, to free the memory used for extracted strings.
181 nigel 75 .P
182     The function \fBpcre_maketables()\fP is used to build a set of character tables
183 nigel 77 in the current locale for passing to \fBpcre_compile()\fP, \fBpcre_exec()\fP,
184     or \fBpcre_dfa_exec()\fP. This is an optional facility that is provided for
185     specialist use. Most commonly, no special tables are passed, in which case
186     internal tables that are generated when PCRE is built are used.
187 nigel 75 .P
188     The function \fBpcre_fullinfo()\fP is used to find out information about a
189     compiled pattern; \fBpcre_info()\fP is an obsolete version that returns only
190 nigel 63 some of the available information, but is retained for backwards compatibility.
191 nigel 75 The function \fBpcre_version()\fP returns a pointer to a string containing the
192 nigel 63 version of PCRE and its date of release.
193 nigel 75 .P
194 nigel 77 The function \fBpcre_refcount()\fP maintains a reference count in a data block
195     containing a compiled pattern. This is provided for the benefit of
196     object-oriented applications.
197     .P
198 nigel 75 The global variables \fBpcre_malloc\fP and \fBpcre_free\fP initially contain
199     the entry points of the standard \fBmalloc()\fP and \fBfree()\fP functions,
200 nigel 63 respectively. PCRE calls the memory management functions via these variables,
201     so a calling program can replace them if it wishes to intercept the calls. This
202     should be done before calling any PCRE functions.
203 nigel 75 .P
204     The global variables \fBpcre_stack_malloc\fP and \fBpcre_stack_free\fP are also
205 nigel 73 indirections to memory management functions. These special functions are used
206     only when PCRE is compiled to use the heap for remembering data, instead of
207 nigel 91 recursive function calls, when running the \fBpcre_exec()\fP function. See the
208     .\" HREF
209     \fBpcrebuild\fP
210     .\"
211     documentation for details of how to do this. It is a non-standard way of
212     building PCRE, for use in environments that have limited stacks. Because of the
213     greater use of memory management, it runs more slowly. Separate functions are
214     provided so that special-purpose external code can be used for this case. When
215     used, these functions are always called in a stack-like manner (last obtained,
216     first freed), and always for memory blocks of the same size. There is a
217     discussion about PCRE's stack usage in the
218     .\" HREF
219     \fBpcrestack\fP
220     .\"
221     documentation.
222 nigel 75 .P
223     The global variable \fBpcre_callout\fP initially contains NULL. It can be set
224 nigel 63 by the caller to a "callout" function, which PCRE will then call at specified
225 nigel 75 points during a matching operation. Details are given in the
226     .\" HREF
227     \fBpcrecallout\fP
228     .\"
229 nigel 63 documentation.
230 nigel 75 .
231     .
232 ph10 227 .\" HTML <a name="newlines"></a>
233 nigel 91 .SH NEWLINES
234 nigel 93 .rs
235 nigel 91 .sp
236 ph10 149 PCRE supports five different conventions for indicating line breaks in
237 nigel 93 strings: a single CR (carriage return) character, a single LF (linefeed)
238 ph10 149 character, the two-character sequence CRLF, any of the three preceding, or any
239     Unicode newline sequence. The Unicode newline sequences are the three just
240     mentioned, plus the single characters VT (vertical tab, U+000B), FF (formfeed,
241     U+000C), NEL (next line, U+0085), LS (line separator, U+2028), and PS
242     (paragraph separator, U+2029).
243 nigel 93 .P
244     Each of the first three conventions is used by at least one operating system as
245     its standard newline sequence. When PCRE is built, a default can be specified.
246     The default default is LF, which is the Unix standard. When PCRE is run, the
247     default can be overridden, either when a pattern is compiled, or when it is
248     matched.
249     .P
250 ph10 227 At compile time, the newline convention can be specified by the \fIoptions\fP
251     argument of \fBpcre_compile()\fP, or it can be specified by special text at the
252     start of the pattern itself; this overrides any other settings. See the
253     .\" HREF
254     \fBpcrepattern\fP
255     .\"
256     page for details of the special character sequences.
257     .P
258 nigel 91 In the PCRE documentation the word "newline" is used to mean "the character or
259 nigel 93 pair of characters that indicate a line break". The choice of newline
260     convention affects the handling of the dot, circumflex, and dollar
261     metacharacters, the handling of #-comments in /x mode, and, when CRLF is a
262     recognized line ending sequence, the match position advancement for a
263 ph10 226 non-anchored pattern. There is more detail about this in the
264     .\" HTML <a href="#execoptions">
265     .\" </a>
266     section on \fBpcre_exec()\fP options
267     .\"
268 ph10 231 below.
269     .P
270     The choice of newline convention does not affect the interpretation of
271     the \en or \er escape sequences, nor does it affect what \eR matches, which is
272     controlled in a similar way, but by separate options.
273 nigel 91 .
274     .
275 nigel 63 .SH MULTITHREADING
276     .rs
277     .sp
278     The PCRE functions can be used in multi-threading applications, with the
279 nigel 75 proviso that the memory management functions pointed to by \fBpcre_malloc\fP,
280     \fBpcre_free\fP, \fBpcre_stack_malloc\fP, and \fBpcre_stack_free\fP, and the
281     callout function pointed to by \fBpcre_callout\fP, are shared by all threads.
282     .P
283 nigel 63 The compiled form of a regular expression is not altered during matching, so
284     the same compiled pattern can safely be used by several threads at once.
285 nigel 75 .
286     .
287     .SH "SAVING PRECOMPILED PATTERNS FOR LATER USE"
288 nigel 63 .rs
289     .sp
290 nigel 75 The compiled form of a regular expression can be saved and re-used at a later
291     time, possibly by a different program, and even on a host other than the one on
292     which it was compiled. Details are given in the
293     .\" HREF
294     \fBpcreprecompile\fP
295     .\"
296 ph10 155 documentation. However, compiling a regular expression with one version of PCRE
297     for use with a different version is not guaranteed to work and may cause
298     crashes.
299 nigel 75 .
300     .
301     .SH "CHECKING BUILD-TIME OPTIONS"
302     .rs
303     .sp
304     .B int pcre_config(int \fIwhat\fP, void *\fIwhere\fP);
305 nigel 63 .PP
306 nigel 75 The function \fBpcre_config()\fP makes it possible for a PCRE client to
307 nigel 63 discover which optional features have been compiled into the PCRE library. The
308     .\" HREF
309 nigel 75 \fBpcrebuild\fP
310 nigel 63 .\"
311     documentation has more details about these optional features.
312 nigel 75 .P
313     The first argument for \fBpcre_config()\fP is an integer, specifying which
314 nigel 63 information is required; the second argument is a pointer to a variable into
315     which the information is placed. The following information is available:
316 nigel 75 .sp
317 nigel 63 PCRE_CONFIG_UTF8
318 nigel 75 .sp
319 nigel 63 The output is an integer that is set to one if UTF-8 support is available;
320     otherwise it is set to zero.
321 nigel 75 .sp
322     PCRE_CONFIG_UNICODE_PROPERTIES
323     .sp
324     The output is an integer that is set to one if support for Unicode character
325     properties is available; otherwise it is set to zero.
326     .sp
327 nigel 63 PCRE_CONFIG_NEWLINE
328 nigel 75 .sp
329 nigel 91 The output is an integer whose value specifies the default character sequence
330 nigel 93 that is recognized as meaning "newline". The four values that are supported
331 ph10 392 are: 10 for LF, 13 for CR, 3338 for CRLF, -2 for ANYCRLF, and -1 for ANY.
332 ph10 391 Though they are derived from ASCII, the same values are returned in EBCDIC
333     environments. The default should normally correspond to the standard sequence
334     for your operating system.
335 nigel 75 .sp
336 ph10 231 PCRE_CONFIG_BSR
337     .sp
338     The output is an integer whose value indicates what character sequences the \eR
339     escape sequence matches by default. A value of 0 means that \eR matches any
340     Unicode line ending sequence; a value of 1 means that \eR matches only CR, LF,
341     or CRLF. The default can be overridden when a pattern is compiled or matched.
342     .sp
343 nigel 63 PCRE_CONFIG_LINK_SIZE
344 nigel 75 .sp
345 nigel 63 The output is an integer that contains the number of bytes used for internal
346     linkage in compiled regular expressions. The value is 2, 3, or 4. Larger values
347     allow larger regular expressions to be compiled, at the expense of slower
348     matching. The default value of 2 is sufficient for all but the most massive
349     patterns, since it allows the compiled pattern to be up to 64K in size.
350 nigel 75 .sp
351 nigel 63 PCRE_CONFIG_POSIX_MALLOC_THRESHOLD
352 nigel 75 .sp
353 nigel 63 The output is an integer that contains the threshold above which the POSIX
354 nigel 75 interface uses \fBmalloc()\fP for output vectors. Further details are given in
355     the
356     .\" HREF
357     \fBpcreposix\fP
358     .\"
359     documentation.
360     .sp
361 nigel 63 PCRE_CONFIG_MATCH_LIMIT
362 nigel 75 .sp
363 ph10 376 The output is a long integer that gives the default limit for the number of
364 nigel 75 internal matching function calls in a \fBpcre_exec()\fP execution. Further
365     details are given with \fBpcre_exec()\fP below.
366     .sp
367 nigel 87 PCRE_CONFIG_MATCH_LIMIT_RECURSION
368     .sp
369 ph10 376 The output is a long integer that gives the default limit for the depth of
370 nigel 87 recursion when calling the internal matching function in a \fBpcre_exec()\fP
371     execution. Further details are given with \fBpcre_exec()\fP below.
372     .sp
373 nigel 73 PCRE_CONFIG_STACKRECURSE
374 nigel 75 .sp
375 nigel 77 The output is an integer that is set to one if internal recursion when running
376     \fBpcre_exec()\fP is implemented by recursive function calls that use the stack
377     to remember their state. This is the usual way that PCRE is compiled. The
378     output is zero if PCRE was compiled to use blocks of data on the heap instead
379     of recursive function calls. In this case, \fBpcre_stack_malloc\fP and
380     \fBpcre_stack_free\fP are called to manage memory blocks on the heap, thus
381     avoiding the use of the stack.
382 nigel 75 .
383     .
384     .SH "COMPILING A PATTERN"
385 nigel 63 .rs
386     .sp
387 nigel 75 .B pcre *pcre_compile(const char *\fIpattern\fP, int \fIoptions\fP,
388 nigel 63 .ti +5n
389 nigel 75 .B const char **\fIerrptr\fP, int *\fIerroffset\fP,
390 nigel 63 .ti +5n
391 nigel 75 .B const unsigned char *\fItableptr\fP);
392 nigel 77 .sp
393     .B pcre *pcre_compile2(const char *\fIpattern\fP, int \fIoptions\fP,
394     .ti +5n
395     .B int *\fIerrorcodeptr\fP,
396     .ti +5n
397     .B const char **\fIerrptr\fP, int *\fIerroffset\fP,
398     .ti +5n
399     .B const unsigned char *\fItableptr\fP);
400 nigel 75 .P
401 nigel 77 Either of the functions \fBpcre_compile()\fP or \fBpcre_compile2()\fP can be
402     called to compile a pattern into an internal form. The only difference between
403     the two interfaces is that \fBpcre_compile2()\fP has an additional argument,
404 ph10 461 \fIerrorcodeptr\fP, via which a numerical error code can be returned. To avoid
405     too much repetition, we refer just to \fBpcre_compile()\fP below, but the
406 ph10 456 information applies equally to \fBpcre_compile2()\fP.
407 nigel 75 .P
408 nigel 77 The pattern is a C string terminated by a binary zero, and is passed in the
409     \fIpattern\fP argument. A pointer to a single block of memory that is obtained
410     via \fBpcre_malloc\fP is returned. This contains the compiled code and related
411     data. The \fBpcre\fP type is defined for the returned block; this is a typedef
412     for a structure whose contents are not externally defined. It is up to the
413 nigel 91 caller to free the memory (via \fBpcre_free\fP) when it is no longer required.
414 nigel 77 .P
415 nigel 63 Although the compiled code of a PCRE regex is relocatable, that is, it does not
416 nigel 75 depend on memory location, the complete \fBpcre\fP data block is not
417     fully relocatable, because it may contain a copy of the \fItableptr\fP
418     argument, which is an address (see below).
419     .P
420 nigel 93 The \fIoptions\fP argument contains various bit settings that affect the
421 nigel 75 compilation. It should be zero if no options are required. The available
422 ph10 412 options are described below. Some of them (in particular, those that are
423 ph10 456 compatible with Perl, but some others as well) can also be set and unset from
424 ph10 412 within the pattern (see the detailed description in the
425 nigel 75 .\" HREF
426     \fBpcrepattern\fP
427     .\"
428 ph10 412 documentation). For those options that can be different in different parts of
429 ph10 456 the pattern, the contents of the \fIoptions\fP argument specifies their
430 ph10 461 settings at the start of compilation and execution. The PCRE_ANCHORED,
431 ph10 456 PCRE_BSR_\fIxxx\fP, and PCRE_NEWLINE_\fIxxx\fP options can be set at the time
432     of matching as well as at compile time.
433 nigel 75 .P
434     If \fIerrptr\fP is NULL, \fBpcre_compile()\fP returns NULL immediately.
435     Otherwise, if compilation of a pattern fails, \fBpcre_compile()\fP returns
436     NULL, and sets the variable pointed to by \fIerrptr\fP to point to a textual
437 nigel 87 error message. This is a static string that is part of the library. You must
438 ph10 454 not try to free it. The byte offset from the start of the pattern to the
439 ph10 456 character that was being processed when the error was discovered is placed in
440 ph10 454 the variable pointed to by \fIerroffset\fP, which must not be NULL. If it is,
441     an immediate error is given. Some errors are not detected until checks are
442     carried out when the whole pattern has been scanned; in this case the offset is
443     set to the end of the pattern.
444 nigel 75 .P
445 nigel 77 If \fBpcre_compile2()\fP is used instead of \fBpcre_compile()\fP, and the
446     \fIerrorcodeptr\fP argument is not NULL, a non-zero error code number is
447     returned via this argument in the event of an error. This is in addition to the
448     textual error message. Error codes and messages are listed below.
449     .P
450 nigel 75 If the final argument, \fItableptr\fP, is NULL, PCRE uses a default set of
451     character tables that are built when PCRE is compiled, using the default C
452     locale. Otherwise, \fItableptr\fP must be an address that is the result of a
453     call to \fBpcre_maketables()\fP. This value is stored with the compiled
454     pattern, and used again by \fBpcre_exec()\fP, unless another table pointer is
455     passed to it. For more discussion, see the section on locale support below.
456     .P
457     This code fragment shows a typical straightforward call to \fBpcre_compile()\fP:
458     .sp
459 nigel 63 pcre *re;
460     const char *error;
461     int erroffset;
462     re = pcre_compile(
463     "^A.*Z", /* the pattern */
464     0, /* default options */
465     &error, /* for error message */
466     &erroffset, /* for error offset */
467     NULL); /* use default character tables */
468 nigel 75 .sp
469     The following names for option bits are defined in the \fBpcre.h\fP header
470     file:
471     .sp
472 nigel 63 PCRE_ANCHORED
473 nigel 75 .sp
474 nigel 63 If this bit is set, the pattern is forced to be "anchored", that is, it is
475 nigel 75 constrained to match only at the first matching point in the string that is
476 nigel 63 being searched (the "subject string"). This effect can also be achieved by
477     appropriate constructs in the pattern itself, which is the only way to do it in
478     Perl.
479 nigel 75 .sp
480     PCRE_AUTO_CALLOUT
481     .sp
482     If this bit is set, \fBpcre_compile()\fP automatically inserts callout items,
483     all with number 255, before each pattern item. For discussion of the callout
484     facility, see the
485     .\" HREF
486     \fBpcrecallout\fP
487     .\"
488     documentation.
489     .sp
490 ph10 231 PCRE_BSR_ANYCRLF
491     PCRE_BSR_UNICODE
492     .sp
493     These options (which are mutually exclusive) control what the \eR escape
494     sequence matches. The choice is either to match only CR, LF, or CRLF, or to
495     match any Unicode newline sequence. The default is specified when PCRE is
496     built. It can be overridden from within the pattern, or by setting an option
497     when a compiled pattern is matched.
498     .sp
499 nigel 63 PCRE_CASELESS
500 nigel 75 .sp
501 nigel 63 If this bit is set, letters in the pattern match both upper and lower case
502     letters. It is equivalent to Perl's /i option, and it can be changed within a
503 nigel 77 pattern by a (?i) option setting. In UTF-8 mode, PCRE always understands the
504     concept of case for characters whose values are less than 128, so caseless
505     matching is always possible. For characters with higher values, the concept of
506     case is supported if PCRE is compiled with Unicode property support, but not
507     otherwise. If you want to use caseless matching for characters 128 and above,
508     you must ensure that PCRE is compiled with Unicode property support as well as
509     with UTF-8 support.
510 nigel 75 .sp
511 nigel 63 PCRE_DOLLAR_ENDONLY
512 nigel 75 .sp
513 nigel 63 If this bit is set, a dollar metacharacter in the pattern matches only at the
514     end of the subject string. Without this option, a dollar also matches
515 nigel 91 immediately before a newline at the end of the string (but not before any other
516     newlines). The PCRE_DOLLAR_ENDONLY option is ignored if PCRE_MULTILINE is set.
517     There is no equivalent to this option in Perl, and no way to set it within a
518     pattern.
519 nigel 75 .sp
520 nigel 63 PCRE_DOTALL
521 nigel 75 .sp
522 nigel 63 If this bit is set, a dot metacharater in the pattern matches all characters,
523 nigel 91 including those that indicate newline. Without it, a dot does not match when
524     the current position is at a newline. This option is equivalent to Perl's /s
525     option, and it can be changed within a pattern by a (?s) option setting. A
526 nigel 93 negative class such as [^a] always matches newline characters, independent of
527     the setting of this option.
528 nigel 75 .sp
529 nigel 91 PCRE_DUPNAMES
530     .sp
531     If this bit is set, names used to identify capturing subpatterns need not be
532     unique. This can be helpful for certain types of pattern when it is known that
533     only one instance of the named subpattern can ever be matched. There are more
534     details of named subpatterns below; see also the
535     .\" HREF
536     \fBpcrepattern\fP
537     .\"
538     documentation.
539     .sp
540 nigel 63 PCRE_EXTENDED
541 nigel 75 .sp
542 nigel 63 If this bit is set, whitespace data characters in the pattern are totally
543     ignored except when escaped or inside a character class. Whitespace does not
544     include the VT character (code 11). In addition, characters between an
545 nigel 91 unescaped # outside a character class and the next newline, inclusive, are also
546     ignored. This is equivalent to Perl's /x option, and it can be changed within a
547     pattern by a (?x) option setting.
548 nigel 75 .P
549 nigel 63 This option makes it possible to include comments inside complicated patterns.
550     Note, however, that this applies only to data characters. Whitespace characters
551     may never appear within special character sequences in a pattern, for example
552     within the sequence (?( which introduces a conditional subpattern.
553 nigel 75 .sp
554 nigel 63 PCRE_EXTRA
555 nigel 75 .sp
556 nigel 63 This option was invented in order to turn on additional functionality of PCRE
557     that is incompatible with Perl, but it is currently of very little use. When
558     set, any backslash in a pattern that is followed by a letter that has no
559     special meaning causes an error, thus reserving these combinations for future
560     expansion. By default, as in Perl, a backslash followed by a letter with no
561 nigel 91 special meaning is treated as a literal. (Perl can, however, be persuaded to
562 ph10 513 give an error for this, by running it with the -w option.) There are at present
563     no other features controlled by this option. It can also be set by a (?X)
564     option setting within a pattern.
565 nigel 75 .sp
566 nigel 77 PCRE_FIRSTLINE
567     .sp
568     If this option is set, an unanchored pattern is required to match before or at
569 nigel 91 the first newline in the subject string, though the matched text may continue
570     over the newline.
571 nigel 77 .sp
572 ph10 336 PCRE_JAVASCRIPT_COMPAT
573     .sp
574 ph10 345 If this option is set, PCRE's behaviour is changed in some ways so that it is
575 ph10 336 compatible with JavaScript rather than Perl. The changes are as follows:
576     .P
577     (1) A lone closing square bracket in a pattern causes a compile-time error,
578     because this is illegal in JavaScript (by default it is treated as a data
579     character). Thus, the pattern AB]CD becomes illegal when this option is set.
580     .P
581     (2) At run time, a back reference to an unset subpattern group matches an empty
582 ph10 345 string (by default this causes the current matching alternative to fail). A
583     pattern such as (\e1)(a) succeeds when this option is set (assuming it can find
584     an "a" in the subject), whereas it fails by default, for Perl compatibility.
585 ph10 336 .sp
586 nigel 63 PCRE_MULTILINE
587 nigel 75 .sp
588     By default, PCRE treats the subject string as consisting of a single line of
589     characters (even if it actually contains newlines). The "start of line"
590 nigel 63 metacharacter (^) matches only at the start of the string, while the "end of
591     line" metacharacter ($) matches only at the end of the string, or before a
592     terminating newline (unless PCRE_DOLLAR_ENDONLY is set). This is the same as
593     Perl.
594 nigel 75 .P
595 nigel 63 When PCRE_MULTILINE it is set, the "start of line" and "end of line" constructs
596 nigel 91 match immediately following or immediately before internal newlines in the
597     subject string, respectively, as well as at the very start and end. This is
598     equivalent to Perl's /m option, and it can be changed within a pattern by a
599     (?m) option setting. If there are no newlines in a subject string, or no
600 nigel 63 occurrences of ^ or $ in a pattern, setting PCRE_MULTILINE has no effect.
601 nigel 75 .sp
602 nigel 91 PCRE_NEWLINE_CR
603     PCRE_NEWLINE_LF
604     PCRE_NEWLINE_CRLF
605 ph10 150 PCRE_NEWLINE_ANYCRLF
606 nigel 93 PCRE_NEWLINE_ANY
607 nigel 91 .sp
608     These options override the default newline definition that was chosen when PCRE
609     was built. Setting the first or the second specifies that a newline is
610 nigel 93 indicated by a single character (CR or LF, respectively). Setting
611     PCRE_NEWLINE_CRLF specifies that a newline is indicated by the two-character
612 ph10 149 CRLF sequence. Setting PCRE_NEWLINE_ANYCRLF specifies that any of the three
613     preceding sequences should be recognized. Setting PCRE_NEWLINE_ANY specifies
614     that any Unicode newline sequence should be recognized. The Unicode newline
615     sequences are the three just mentioned, plus the single characters VT (vertical
616     tab, U+000B), FF (formfeed, U+000C), NEL (next line, U+0085), LS (line
617     separator, U+2028), and PS (paragraph separator, U+2029). The last two are
618     recognized only in UTF-8 mode.
619 nigel 91 .P
620 nigel 93 The newline setting in the options word uses three bits that are treated
621 ph10 149 as a number, giving eight possibilities. Currently only six are used (default
622     plus the five values above). This means that if you set more than one newline
623 nigel 93 option, the combination may or may not be sensible. For example,
624     PCRE_NEWLINE_CR with PCRE_NEWLINE_LF is equivalent to PCRE_NEWLINE_CRLF, but
625 ph10 149 other combinations may yield unused numbers and cause an error.
626 nigel 93 .P
627     The only time that a line break is specially recognized when compiling a
628     pattern is if PCRE_EXTENDED is set, and an unescaped # outside a character
629     class is encountered. This indicates a comment that lasts until after the next
630     line break sequence. In other circumstances, line break sequences are treated
631     as literal data, except that in PCRE_EXTENDED mode, both CR and LF are treated
632     as whitespace characters and are therefore ignored.
633     .P
634     The newline option that is set at compile time becomes the default that is used
635     for \fBpcre_exec()\fP and \fBpcre_dfa_exec()\fP, but it can be overridden.
636 nigel 91 .sp
637 nigel 63 PCRE_NO_AUTO_CAPTURE
638 nigel 75 .sp
639 nigel 63 If this option is set, it disables the use of numbered capturing parentheses in
640     the pattern. Any opening parenthesis that is not followed by ? behaves as if it
641     were followed by ?: but named parentheses can still be used for capturing (and
642     they acquire numbers in the usual way). There is no equivalent of this option
643     in Perl.
644 nigel 75 .sp
645 ph10 518 PCRE_UCP
646     .sp
647     This option changes the way PCRE processes \eb, \ed, \es, \ew, and some of the
648     POSIX character classes. By default, only ASCII characters are recognized, but
649     if PCRE_UCP is set, Unicode properties are used instead to classify characters.
650     More details are given in the section on
651     .\" HTML <a href="pcre.html#genericchartypes">
652     .\" </a>
653     generic character types
654     .\"
655     in the
656     .\" HREF
657     \fBpcrepattern\fP
658     .\"
659     page. If you set PCRE_UCP, matching one of the items it affects takes much
660     longer. The option is available only if PCRE has been compiled with Unicode
661     property support.
662     .sp
663 nigel 63 PCRE_UNGREEDY
664 nigel 75 .sp
665 nigel 63 This option inverts the "greediness" of the quantifiers so that they are not
666     greedy by default, but become greedy if followed by "?". It is not compatible
667     with Perl. It can also be set by a (?U) option setting within the pattern.
668 nigel 75 .sp
669 nigel 63 PCRE_UTF8
670 nigel 75 .sp
671 nigel 63 This option causes PCRE to regard both the pattern and the subject as strings
672     of UTF-8 characters instead of single-byte character strings. However, it is
673 nigel 75 available only when PCRE is built to include UTF-8 support. If not, the use
674 nigel 63 of this option provokes an error. Details of how this option changes the
675     behaviour of PCRE are given in the
676     .\" HTML <a href="pcre.html#utf8support">
677     .\" </a>
678     section on UTF-8 support
679     .\"
680     in the main
681     .\" HREF
682 nigel 75 \fBpcre\fP
683 nigel 63 .\"
684     page.
685 nigel 75 .sp
686 nigel 71 PCRE_NO_UTF8_CHECK
687 nigel 75 .sp
688 nigel 71 When PCRE_UTF8 is set, the validity of the pattern as a UTF-8 string is
689 ph10 211 automatically checked. There is a discussion about the
690     .\" HTML <a href="pcre.html#utf8strings">
691     .\" </a>
692     validity of UTF-8 strings
693     .\"
694     in the main
695     .\" HREF
696     \fBpcre\fP
697     .\"
698     page. If an invalid UTF-8 sequence of bytes is found, \fBpcre_compile()\fP
699     returns an error. If you already know that your pattern is valid, and you want
700     to skip this check for performance reasons, you can set the PCRE_NO_UTF8_CHECK
701     option. When it is set, the effect of passing an invalid UTF-8 string as a
702     pattern is undefined. It may cause your program to crash. Note that this option
703     can also be passed to \fBpcre_exec()\fP and \fBpcre_dfa_exec()\fP, to suppress
704     the UTF-8 validity checking of subject strings.
705 nigel 75 .
706     .
707 nigel 77 .SH "COMPILATION ERROR CODES"
708     .rs
709     .sp
710     The following table lists the error codes than may be returned by
711     \fBpcre_compile2()\fP, along with the error messages that may be returned by
712 nigel 93 both compiling functions. As PCRE has developed, some error codes have fallen
713     out of use. To avoid confusion, they have not been re-used.
714 nigel 77 .sp
715     0 no error
716     1 \e at end of pattern
717     2 \ec at end of pattern
718     3 unrecognized character follows \e
719     4 numbers out of order in {} quantifier
720     5 number too big in {} quantifier
721     6 missing terminating ] for character class
722     7 invalid escape sequence in character class
723     8 range out of order in character class
724     9 nothing to repeat
725 nigel 93 10 [this code is not in use]
726 nigel 77 11 internal error: unexpected repeat
727 ph10 290 12 unrecognized character after (? or (?-
728 nigel 77 13 POSIX named classes are supported only within a class
729     14 missing )
730     15 reference to non-existent subpattern
731     16 erroffset passed as NULL
732     17 unknown option bit(s) set
733     18 missing ) after comment
734 nigel 93 19 [this code is not in use]
735 ph10 290 20 regular expression is too large
736 nigel 77 21 failed to get memory
737     22 unmatched parentheses
738     23 internal error: code overflow
739     24 unrecognized character after (?<
740     25 lookbehind assertion is not fixed length
741 nigel 91 26 malformed number or name after (?(
742 nigel 77 27 conditional group contains more than two branches
743     28 assertion expected after (?(
744 ph10 181 29 (?R or (?[+-]digits must be followed by )
745 nigel 77 30 unknown POSIX class name
746     31 POSIX collating elements are not supported
747     32 this version of PCRE is not compiled with PCRE_UTF8 support
748 nigel 93 33 [this code is not in use]
749 nigel 77 34 character value in \ex{...} sequence is too large
750     35 invalid condition (?(0)
751     36 \eC not allowed in lookbehind assertion
752     37 PCRE does not support \eL, \el, \eN, \eU, or \eu
753     38 number after (?C is > 255
754     39 closing ) for (?C expected
755     40 recursive call could loop indefinitely
756     41 unrecognized character after (?P
757 nigel 93 42 syntax error in subpattern name (missing terminator)
758 nigel 91 43 two named subpatterns have the same name
759 nigel 77 44 invalid UTF-8 string
760     45 support for \eP, \ep, and \eX has not been compiled
761     46 malformed \eP or \ep sequence
762     47 unknown property name after \eP or \ep
763 nigel 91 48 subpattern name is too long (maximum 32 characters)
764 ph10 290 49 too many named subpatterns (maximum 10000)
765 ph10 202 50 [this code is not in use]
766 nigel 91 51 octal value is greater than \e377 (not in UTF-8 mode)
767 nigel 93 52 internal error: overran compiling workspace
768 ph10 546 53 internal error: previously-checked referenced subpattern
769     not found
770 nigel 93 54 DEFINE group contains more than one branch
771     55 repeating a DEFINE group is not allowed
772 ph10 231 56 inconsistent NEWLINE options
773 ph10 345 57 \eg is not followed by a braced, angle-bracketed, or quoted
774     name/number or by a plain number
775 ph10 336 58 a numbered reference must not be zero
776 ph10 510 59 an argument is not allowed for (*ACCEPT), (*FAIL), or (*COMMIT)
777 ph10 290 60 (*VERB) not recognized
778     61 number is too big
779     62 subpattern name expected
780 ph10 292 63 digit expected after (?+
781 ph10 336 64 ] is an invalid data character in JavaScript compatibility mode
782 ph10 546 65 different names for subpatterns of the same number are
783     not allowed
784 ph10 510 66 (*MARK) must have an argument
785 ph10 518 67 this version of PCRE is not compiled with PCRE_UCP support
786 ph10 290 .sp
787 ph10 292 The numbers 32 and 10000 in errors 48 and 49 are defaults; different values may
788 ph10 290 be used if the limits were changed when PCRE was built.
789 nigel 77 .
790     .
791 nigel 75 .SH "STUDYING A PATTERN"
792 nigel 63 .rs
793     .sp
794 nigel 77 .B pcre_extra *pcre_study(const pcre *\fIcode\fP, int \fIoptions\fP
795 nigel 63 .ti +5n
796 nigel 75 .B const char **\fIerrptr\fP);
797 nigel 63 .PP
798 nigel 75 If a compiled pattern is going to be used several times, it is worth spending
799     more time analyzing it in order to speed up the time taken for matching. The
800     function \fBpcre_study()\fP takes a pointer to a compiled pattern as its first
801     argument. If studying the pattern produces additional information that will
802     help speed up matching, \fBpcre_study()\fP returns a pointer to a
803     \fBpcre_extra\fP block, in which the \fIstudy_data\fP field points to the
804     results of the study.
805     .P
806     The returned value from \fBpcre_study()\fP can be passed directly to
807 ph10 455 \fBpcre_exec()\fP or \fBpcre_dfa_exec()\fP. However, a \fBpcre_extra\fP block
808     also contains other fields that can be set by the caller before the block is
809     passed; these are described
810 nigel 75 .\" HTML <a href="#extradata">
811     .\" </a>
812     below
813     .\"
814     in the section on matching a pattern.
815     .P
816 ph10 455 If studying the pattern does not produce any useful information,
817 nigel 75 \fBpcre_study()\fP returns NULL. In that circumstance, if the calling program
818 ph10 461 wants to pass any of the other fields to \fBpcre_exec()\fP or
819 ph10 455 \fBpcre_dfa_exec()\fP, it must set up its own \fBpcre_extra\fP block.
820 nigel 75 .P
821     The second argument of \fBpcre_study()\fP contains option bits. At present, no
822     options are defined, and this argument should always be zero.
823     .P
824     The third argument for \fBpcre_study()\fP is a pointer for an error message. If
825 nigel 63 studying succeeds (even if no data is returned), the variable it points to is
826 nigel 87 set to NULL. Otherwise it is set to point to a textual error message. This is a
827     static string that is part of the library. You must not try to free it. You
828     should test the error pointer for NULL after calling \fBpcre_study()\fP, to be
829     sure that it has run successfully.
830 nigel 75 .P
831     This is a typical call to \fBpcre_study\fP():
832     .sp
833 nigel 63 pcre_extra *pe;
834     pe = pcre_study(
835     re, /* result of pcre_compile() */
836     0, /* no options exist */
837     &error); /* set to NULL or points to a message */
838 nigel 75 .sp
839 ph10 455 Studying a pattern does two things: first, a lower bound for the length of
840 ph10 461 subject string that is needed to match the pattern is computed. This does not
841     mean that there are any strings of that length that match, but it does
842     guarantee that no shorter strings match. The value is used by
843     \fBpcre_exec()\fP and \fBpcre_dfa_exec()\fP to avoid wasting time by trying to
844     match strings that are shorter than the lower bound. You can find out the value
845 ph10 455 in a calling program via the \fBpcre_fullinfo()\fP function.
846     .P
847     Studying a pattern is also useful for non-anchored patterns that do not have a
848     single fixed starting character. A bitmap of possible starting bytes is
849 ph10 461 created. This speeds up finding a position in the subject at which to start
850 ph10 455 matching.
851 ph10 547 .P
852     The two optimizations just described can be disabled by setting the
853     PCRE_NO_START_OPTIMIZE option when calling \fBpcre_exec()\fP or
854     \fBpcre_dfa_exec()\fP. You might want to do this if your pattern contains
855     callouts, or make use of (*MARK), and you make use of these in cases where
856     matching fails. See the discussion of PCRE_NO_START_OPTIMIZE
857     .\" HTML <a href="#execoptions">
858     .\" </a>
859     below.
860     .\"
861 nigel 75 .
862     .
863 nigel 63 .\" HTML <a name="localesupport"></a>
864 nigel 75 .SH "LOCALE SUPPORT"
865 nigel 63 .rs
866     .sp
867 ph10 139 PCRE handles caseless matching, and determines whether characters are letters,
868 nigel 75 digits, or whatever, by reference to a set of tables, indexed by character
869 nigel 77 value. When running in UTF-8 mode, this applies only to characters with codes
870 ph10 518 less than 128. By default, higher-valued codes never match escapes such as \ew
871     or \ed, but they can be tested with \ep if PCRE is built with Unicode character
872     property support. Alternatively, the PCRE_UCP option can be set at compile
873     time; this causes \ew and friends to use Unicode property support instead of
874     built-in tables. The use of locales with Unicode is discouraged. If you are
875     handling characters with codes greater than 128, you should either use UTF-8
876     and Unicode, or use locales, but not try to mix the two.
877 nigel 75 .P
878 ph10 139 PCRE contains an internal set of tables that are used when the final argument
879     of \fBpcre_compile()\fP is NULL. These are sufficient for many applications.
880 ph10 142 Normally, the internal tables recognize only ASCII characters. However, when
881 ph10 139 PCRE is built, it is possible to cause the internal tables to be rebuilt in the
882     default "C" locale of the local system, which may cause them to be different.
883 nigel 75 .P
884 ph10 139 The internal tables can always be overridden by tables supplied by the
885     application that calls PCRE. These may be created in a different locale from
886     the default. As more and more applications change to using Unicode, the need
887     for this locale support is expected to die away.
888     .P
889 nigel 75 External tables are built by calling the \fBpcre_maketables()\fP function,
890     which has no arguments, in the relevant locale. The result can then be passed
891     to \fBpcre_compile()\fP or \fBpcre_exec()\fP as often as necessary. For
892     example, to build and use tables that are appropriate for the French locale
893     (where accented characters with values greater than 128 are treated as letters),
894     the following code could be used:
895     .sp
896     setlocale(LC_CTYPE, "fr_FR");
897 nigel 63 tables = pcre_maketables();
898     re = pcre_compile(..., tables);
899 nigel 75 .sp
900 ph10 142 The locale name "fr_FR" is used on Linux and other Unix-like systems; if you
901 ph10 139 are using Windows, the name for the French locale is "french".
902     .P
903 nigel 75 When \fBpcre_maketables()\fP runs, the tables are built in memory that is
904     obtained via \fBpcre_malloc\fP. It is the caller's responsibility to ensure
905     that the memory containing the tables remains available for as long as it is
906     needed.
907     .P
908     The pointer that is passed to \fBpcre_compile()\fP is saved with the compiled
909     pattern, and the same tables are used via this pointer by \fBpcre_study()\fP
910     and normally also by \fBpcre_exec()\fP. Thus, by default, for any single
911     pattern, compilation, studying and matching all happen in the same locale, but
912     different patterns can be compiled in different locales.
913     .P
914     It is possible to pass a table pointer or NULL (indicating the use of the
915     internal tables) to \fBpcre_exec()\fP. Although not intended for this purpose,
916     this facility could be used to match a pattern in a different locale from the
917     one in which it was compiled. Passing table pointers at run time is discussed
918     below in the section on matching a pattern.
919     .
920     .
921     .SH "INFORMATION ABOUT A PATTERN"
922 nigel 63 .rs
923     .sp
924 nigel 75 .B int pcre_fullinfo(const pcre *\fIcode\fP, "const pcre_extra *\fIextra\fP,"
925 nigel 63 .ti +5n
926 nigel 75 .B int \fIwhat\fP, void *\fIwhere\fP);
927 nigel 63 .PP
928 nigel 75 The \fBpcre_fullinfo()\fP function returns information about a compiled
929     pattern. It replaces the obsolete \fBpcre_info()\fP function, which is
930 nigel 63 nevertheless retained for backwards compability (and is documented below).
931 nigel 75 .P
932     The first argument for \fBpcre_fullinfo()\fP is a pointer to the compiled
933     pattern. The second argument is the result of \fBpcre_study()\fP, or NULL if
934 nigel 63 the pattern was not studied. The third argument specifies which piece of
935     information is required, and the fourth argument is a pointer to a variable
936     to receive the data. The yield of the function is zero for success, or one of
937     the following negative numbers:
938 nigel 75 .sp
939     PCRE_ERROR_NULL the argument \fIcode\fP was NULL
940     the argument \fIwhere\fP was NULL
941 nigel 63 PCRE_ERROR_BADMAGIC the "magic number" was not found
942 nigel 75 PCRE_ERROR_BADOPTION the value of \fIwhat\fP was invalid
943     .sp
944     The "magic number" is placed at the start of each compiled pattern as an simple
945     check against passing an arbitrary memory pointer. Here is a typical call of
946     \fBpcre_fullinfo()\fP, to obtain the length of the compiled pattern:
947     .sp
948 nigel 63 int rc;
949 nigel 91 size_t length;
950 nigel 63 rc = pcre_fullinfo(
951     re, /* result of pcre_compile() */
952     pe, /* result of pcre_study(), or NULL */
953     PCRE_INFO_SIZE, /* what is required */
954     &length); /* where to put the data */
955 nigel 75 .sp
956     The possible values for the third argument are defined in \fBpcre.h\fP, and are
957 nigel 63 as follows:
958 nigel 75 .sp
959 nigel 63 PCRE_INFO_BACKREFMAX
960 nigel 75 .sp
961 nigel 63 Return the number of the highest back reference in the pattern. The fourth
962 nigel 75 argument should point to an \fBint\fP variable. Zero is returned if there are
963 nigel 63 no back references.
964 nigel 75 .sp
965 nigel 63 PCRE_INFO_CAPTURECOUNT
966 nigel 75 .sp
967 nigel 63 Return the number of capturing subpatterns in the pattern. The fourth argument
968 nigel 75 should point to an \fBint\fP variable.
969     .sp
970 nigel 77 PCRE_INFO_DEFAULT_TABLES
971 nigel 75 .sp
972     Return a pointer to the internal default character tables within PCRE. The
973     fourth argument should point to an \fBunsigned char *\fP variable. This
974     information call is provided for internal use by the \fBpcre_study()\fP
975     function. External callers can cause PCRE to use its internal tables by passing
976     a NULL table pointer.
977     .sp
978 nigel 63 PCRE_INFO_FIRSTBYTE
979 nigel 75 .sp
980 nigel 63 Return information about the first byte of any matched string, for a
981 nigel 91 non-anchored pattern. The fourth argument should point to an \fBint\fP
982     variable. (This option used to be called PCRE_INFO_FIRSTCHAR; the old name is
983     still recognized for backwards compatibility.)
984 nigel 75 .P
985     If there is a fixed first byte, for example, from a pattern such as
986 nigel 93 (cat|cow|coyote), its value is returned. Otherwise, if either
987 nigel 75 .sp
988 nigel 63 (a) the pattern was compiled with the PCRE_MULTILINE option, and every branch
989     starts with "^", or
990 nigel 75 .sp
991 nigel 63 (b) every branch of the pattern starts with ".*" and PCRE_DOTALL is not set
992     (if it were set, the pattern would be anchored),
993 nigel 75 .sp
994 nigel 63 -1 is returned, indicating that the pattern matches only at the start of a
995     subject string or after any newline within the string. Otherwise -2 is
996     returned. For anchored patterns, -2 is returned.
997 nigel 75 .sp
998 nigel 63 PCRE_INFO_FIRSTTABLE
999 nigel 75 .sp
1000 nigel 63 If the pattern was studied, and this resulted in the construction of a 256-bit
1001     table indicating a fixed set of bytes for the first byte in any matching
1002     string, a pointer to the table is returned. Otherwise NULL is returned. The
1003 nigel 75 fourth argument should point to an \fBunsigned char *\fP variable.
1004     .sp
1005 ph10 226 PCRE_INFO_HASCRORLF
1006     .sp
1007 ph10 227 Return 1 if the pattern contains any explicit matches for CR or LF characters,
1008 ph10 243 otherwise 0. The fourth argument should point to an \fBint\fP variable. An
1009 ph10 231 explicit match is either a literal CR or LF character, or \er or \en.
1010 ph10 226 .sp
1011 ph10 169 PCRE_INFO_JCHANGED
1012     .sp
1013 ph10 278 Return 1 if the (?J) or (?-J) option setting is used in the pattern, otherwise
1014     0. The fourth argument should point to an \fBint\fP variable. (?J) and
1015     (?-J) set and unset the local PCRE_DUPNAMES option, respectively.
1016 ph10 169 .sp
1017 nigel 63 PCRE_INFO_LASTLITERAL
1018 nigel 75 .sp
1019 nigel 65 Return the value of the rightmost literal byte that must exist in any matched
1020     string, other than at its start, if such a byte has been recorded. The fourth
1021 nigel 75 argument should point to an \fBint\fP variable. If there is no such byte, -1 is
1022 nigel 65 returned. For anchored patterns, a last literal byte is recorded only if it
1023     follows something of variable length. For example, for the pattern
1024 nigel 75 /^a\ed+z\ed+/ the returned value is "z", but for /^a\edz\ed/ the returned value
1025 nigel 65 is -1.
1026 nigel 75 .sp
1027 ph10 455 PCRE_INFO_MINLENGTH
1028     .sp
1029     If the pattern was studied and a minimum length for matching subject strings
1030     was computed, its value is returned. Otherwise the returned value is -1. The
1031 ph10 456 value is a number of characters, not bytes (this may be relevant in UTF-8
1032 ph10 455 mode). The fourth argument should point to an \fBint\fP variable. A
1033     non-negative value is a lower bound to the length of any matching string. There
1034     may not be any strings of that length that do actually match, but every string
1035     that does match is at least that long.
1036     .sp
1037 nigel 63 PCRE_INFO_NAMECOUNT
1038     PCRE_INFO_NAMEENTRYSIZE
1039     PCRE_INFO_NAMETABLE
1040 nigel 75 .sp
1041 nigel 63 PCRE supports the use of named as well as numbered capturing parentheses. The
1042     names are just an additional way of identifying the parentheses, which still
1043 nigel 91 acquire numbers. Several convenience functions such as
1044     \fBpcre_get_named_substring()\fP are provided for extracting captured
1045     substrings by name. It is also possible to extract the data directly, by first
1046     converting the name to a number in order to access the correct pointers in the
1047     output vector (described with \fBpcre_exec()\fP below). To do the conversion,
1048     you need to use the name-to-number map, which is described by these three
1049     values.
1050 nigel 75 .P
1051 nigel 63 The map consists of a number of fixed-size entries. PCRE_INFO_NAMECOUNT gives
1052     the number of entries, and PCRE_INFO_NAMEENTRYSIZE gives the size of each
1053 nigel 75 entry; both of these return an \fBint\fP value. The entry size depends on the
1054 nigel 63 length of the longest name. PCRE_INFO_NAMETABLE returns a pointer to the first
1055 nigel 75 entry of the table (a pointer to \fBchar\fP). The first two bytes of each entry
1056 nigel 63 are the number of the capturing parenthesis, most significant byte first. The
1057 ph10 461 rest of the entry is the corresponding name, zero terminated.
1058 ph10 457 .P
1059     The names are in alphabetical order. Duplicate names may appear if (?| is used
1060     to create multiple groups with the same number, as described in the
1061     .\" HTML <a href="pcrepattern.html#dupsubpatternnumber">
1062     .\" </a>
1063     section on duplicate subpattern numbers
1064     .\"
1065     in the
1066     .\" HREF
1067     \fBpcrepattern\fP
1068     .\"
1069 ph10 461 page. Duplicate names for subpatterns with different numbers are permitted only
1070     if PCRE_DUPNAMES is set. In all cases of duplicate names, they appear in the
1071     table in the order in which they were found in the pattern. In the absence of
1072     (?| this is the order of increasing number; when (?| is used this is not
1073 ph10 457 necessarily the case because later subpatterns may have lower numbers.
1074     .P
1075     As a simple example of the name/number table, consider the following pattern
1076     (assume PCRE_EXTENDED is set, so white space - including newlines - is
1077     ignored):
1078 nigel 75 .sp
1079     .\" JOIN
1080 nigel 93 (?<date> (?<year>(\ed\ed)?\ed\ed) -
1081     (?<month>\ed\ed) - (?<day>\ed\ed) )
1082 nigel 75 .sp
1083 nigel 63 There are four named subpatterns, so the table has four entries, and each entry
1084     in the table is eight bytes long. The table is as follows, with non-printing
1085 nigel 75 bytes shows in hexadecimal, and undefined bytes shown as ??:
1086     .sp
1087 nigel 63 00 01 d a t e 00 ??
1088     00 05 d a y 00 ?? ??
1089     00 04 m o n t h 00
1090     00 02 y e a r 00 ??
1091 nigel 75 .sp
1092     When writing code to extract data from named subpatterns using the
1093 nigel 91 name-to-number map, remember that the length of the entries is likely to be
1094 nigel 75 different for each compiled pattern.
1095     .sp
1096 ph10 169 PCRE_INFO_OKPARTIAL
1097     .sp
1098 ph10 435 Return 1 if the pattern can be used for partial matching with
1099     \fBpcre_exec()\fP, otherwise 0. The fourth argument should point to an
1100     \fBint\fP variable. From release 8.00, this always returns 1, because the
1101     restrictions that previously applied to partial matching have been lifted. The
1102 ph10 169 .\" HREF
1103     \fBpcrepartial\fP
1104     .\"
1105 ph10 426 documentation gives details of partial matching.
1106 ph10 169 .sp
1107 nigel 63 PCRE_INFO_OPTIONS
1108 nigel 75 .sp
1109 nigel 63 Return a copy of the options with which the pattern was compiled. The fourth
1110 nigel 75 argument should point to an \fBunsigned long int\fP variable. These option bits
1111     are those specified in the call to \fBpcre_compile()\fP, modified by any
1112 ph10 196 top-level option settings at the start of the pattern itself. In other words,
1113     they are the options that will be in force when matching starts. For example,
1114     if the pattern /(?im)abc(?-i)d/ is compiled with the PCRE_EXTENDED option, the
1115     result is PCRE_CASELESS, PCRE_MULTILINE, and PCRE_EXTENDED.
1116 nigel 75 .P
1117 nigel 63 A pattern is automatically anchored by PCRE if all of its top-level
1118     alternatives begin with one of the following:
1119 nigel 75 .sp
1120 nigel 63 ^ unless PCRE_MULTILINE is set
1121 nigel 75 \eA always
1122     \eG always
1123     .\" JOIN
1124 nigel 63 .* if PCRE_DOTALL is set and there are no back
1125     references to the subpattern in which .* appears
1126 nigel 75 .sp
1127 nigel 63 For such patterns, the PCRE_ANCHORED bit is set in the options returned by
1128 nigel 75 \fBpcre_fullinfo()\fP.
1129     .sp
1130 nigel 63 PCRE_INFO_SIZE
1131 nigel 75 .sp
1132 nigel 63 Return the size of the compiled pattern, that is, the value that was passed as
1133 nigel 75 the argument to \fBpcre_malloc()\fP when PCRE was getting memory in which to
1134     place the compiled data. The fourth argument should point to a \fBsize_t\fP
1135 nigel 63 variable.
1136 nigel 75 .sp
1137 nigel 63 PCRE_INFO_STUDYSIZE
1138 nigel 75 .sp
1139     Return the size of the data block pointed to by the \fIstudy_data\fP field in
1140     a \fBpcre_extra\fP block. That is, it is the value that was passed to
1141     \fBpcre_malloc()\fP when PCRE was getting memory into which to place the data
1142 ph10 455 created by \fBpcre_study()\fP. If \fBpcre_extra\fP is NULL, or there is no
1143     study data, zero is returned. The fourth argument should point to a
1144 nigel 75 \fBsize_t\fP variable.
1145     .
1146     .
1147     .SH "OBSOLETE INFO FUNCTION"
1148 nigel 63 .rs
1149     .sp
1150 nigel 75 .B int pcre_info(const pcre *\fIcode\fP, int *\fIoptptr\fP, int
1151     .B *\fIfirstcharptr\fP);
1152 nigel 63 .PP
1153 nigel 75 The \fBpcre_info()\fP function is now obsolete because its interface is too
1154 nigel 63 restrictive to return all the available data about a compiled pattern. New
1155 nigel 75 programs should use \fBpcre_fullinfo()\fP instead. The yield of
1156     \fBpcre_info()\fP is the number of capturing subpatterns, or one of the
1157 nigel 63 following negative numbers:
1158 nigel 75 .sp
1159     PCRE_ERROR_NULL the argument \fIcode\fP was NULL
1160 nigel 63 PCRE_ERROR_BADMAGIC the "magic number" was not found
1161 nigel 75 .sp
1162     If the \fIoptptr\fP argument is not NULL, a copy of the options with which the
1163 nigel 63 pattern was compiled is placed in the integer it points to (see
1164     PCRE_INFO_OPTIONS above).
1165 nigel 75 .P
1166     If the pattern is not anchored and the \fIfirstcharptr\fP argument is not NULL,
1167 nigel 63 it is used to pass back information about the first character of any matched
1168     string (see PCRE_INFO_FIRSTBYTE above).
1169 nigel 75 .
1170     .
1171 nigel 77 .SH "REFERENCE COUNTS"
1172 nigel 63 .rs
1173     .sp
1174 nigel 77 .B int pcre_refcount(pcre *\fIcode\fP, int \fIadjust\fP);
1175     .PP
1176     The \fBpcre_refcount()\fP function is used to maintain a reference count in the
1177     data block that contains a compiled pattern. It is provided for the benefit of
1178     applications that operate in an object-oriented manner, where different parts
1179     of the application may be using the same compiled pattern, but you want to free
1180     the block when they are all done.
1181     .P
1182     When a pattern is compiled, the reference count field is initialized to zero.
1183     It is changed only by calling this function, whose action is to add the
1184     \fIadjust\fP value (which may be positive or negative) to it. The yield of the
1185     function is the new value. However, the value of the count is constrained to
1186     lie between 0 and 65535, inclusive. If the new value is outside these limits,
1187     it is forced to the appropriate limit value.
1188     .P
1189     Except when it is zero, the reference count is not correctly preserved if a
1190     pattern is compiled on one host and then transferred to a host whose byte-order
1191     is different. (This seems a highly unlikely scenario.)
1192     .
1193     .
1194     .SH "MATCHING A PATTERN: THE TRADITIONAL FUNCTION"
1195     .rs
1196     .sp
1197 nigel 75 .B int pcre_exec(const pcre *\fIcode\fP, "const pcre_extra *\fIextra\fP,"
1198 nigel 63 .ti +5n
1199 nigel 75 .B "const char *\fIsubject\fP," int \fIlength\fP, int \fIstartoffset\fP,
1200 nigel 63 .ti +5n
1201 nigel 75 .B int \fIoptions\fP, int *\fIovector\fP, int \fIovecsize\fP);
1202     .P
1203     The function \fBpcre_exec()\fP is called to match a subject string against a
1204     compiled pattern, which is passed in the \fIcode\fP argument. If the
1205 ph10 455 pattern was studied, the result of the study should be passed in the
1206 nigel 77 \fIextra\fP argument. This function is the main matching facility of the
1207     library, and it operates in a Perl-like manner. For specialist use there is
1208     also an alternative matching function, which is described
1209     .\" HTML <a href="#dfamatch">
1210     .\" </a>
1211     below
1212     .\"
1213     in the section about the \fBpcre_dfa_exec()\fP function.
1214 nigel 75 .P
1215     In most applications, the pattern will have been compiled (and optionally
1216     studied) in the same process that calls \fBpcre_exec()\fP. However, it is
1217     possible to save compiled patterns and study data, and then use them later
1218     in different processes, possibly even on different hosts. For a discussion
1219     about this, see the
1220     .\" HREF
1221     \fBpcreprecompile\fP
1222     .\"
1223     documentation.
1224     .P
1225     Here is an example of a simple call to \fBpcre_exec()\fP:
1226     .sp
1227 nigel 63 int rc;
1228     int ovector[30];
1229     rc = pcre_exec(
1230     re, /* result of pcre_compile() */
1231     NULL, /* we didn't study the pattern */
1232     "some string", /* the subject string */
1233     11, /* the length of the subject string */
1234     0, /* start at offset 0 in the subject */
1235     0, /* default options */
1236 nigel 75 ovector, /* vector of integers for substring information */
1237 nigel 77 30); /* number of elements (NOT size in bytes) */
1238 nigel 75 .
1239     .\" HTML <a name="extradata"></a>
1240     .SS "Extra data for \fBpcre_exec()\fR"
1241     .rs
1242     .sp
1243     If the \fIextra\fP argument is not NULL, it must point to a \fBpcre_extra\fP
1244     data block. The \fBpcre_study()\fP function returns such a block (when it
1245 nigel 63 doesn't return NULL), but you can also create one for yourself, and pass
1246 nigel 87 additional information in it. The \fBpcre_extra\fP block contains the following
1247     fields (not necessarily in this order):
1248 nigel 75 .sp
1249     unsigned long int \fIflags\fP;
1250     void *\fIstudy_data\fP;
1251     unsigned long int \fImatch_limit\fP;
1252 nigel 87 unsigned long int \fImatch_limit_recursion\fP;
1253 nigel 75 void *\fIcallout_data\fP;
1254     const unsigned char *\fItables\fP;
1255 ph10 512 unsigned char **\fImark\fP;
1256 nigel 75 .sp
1257     The \fIflags\fP field is a bitmap that specifies which of the other fields
1258 nigel 63 are set. The flag bits are:
1259 nigel 75 .sp
1260 nigel 63 PCRE_EXTRA_STUDY_DATA
1261     PCRE_EXTRA_MATCH_LIMIT
1262 nigel 87 PCRE_EXTRA_MATCH_LIMIT_RECURSION
1263 nigel 63 PCRE_EXTRA_CALLOUT_DATA
1264 nigel 75 PCRE_EXTRA_TABLES
1265 ph10 512 PCRE_EXTRA_MARK
1266 nigel 75 .sp
1267     Other flag bits should be set to zero. The \fIstudy_data\fP field is set in the
1268     \fBpcre_extra\fP block that is returned by \fBpcre_study()\fP, together with
1269     the appropriate flag bit. You should not set this yourself, but you may add to
1270     the block by setting the other fields and their corresponding flag bits.
1271     .P
1272     The \fImatch_limit\fP field provides a means of preventing PCRE from using up a
1273 nigel 63 vast amount of resources when running patterns that are not going to match,
1274     but which have a very large number of possibilities in their search trees. The
1275 ph10 456 classic example is a pattern that uses nested unlimited repeats.
1276 nigel 75 .P
1277     Internally, PCRE uses a function called \fBmatch()\fP which it calls repeatedly
1278 nigel 87 (sometimes recursively). The limit set by \fImatch_limit\fP is imposed on the
1279     number of times this function is called during a match, which has the effect of
1280     limiting the amount of backtracking that can take place. For patterns that are
1281     not anchored, the count restarts from zero for each position in the subject
1282     string.
1283 nigel 75 .P
1284 nigel 87 The default value for the limit can be set when PCRE is built; the default
1285 nigel 63 default is 10 million, which handles all but the most extreme cases. You can
1286 nigel 87 override the default by suppling \fBpcre_exec()\fP with a \fBpcre_extra\fP
1287     block in which \fImatch_limit\fP is set, and PCRE_EXTRA_MATCH_LIMIT is set in
1288     the \fIflags\fP field. If the limit is exceeded, \fBpcre_exec()\fP returns
1289     PCRE_ERROR_MATCHLIMIT.
1290 nigel 75 .P
1291 nigel 87 The \fImatch_limit_recursion\fP field is similar to \fImatch_limit\fP, but
1292     instead of limiting the total number of times that \fBmatch()\fP is called, it
1293     limits the depth of recursion. The recursion depth is a smaller number than the
1294     total number of calls, because not all calls to \fBmatch()\fP are recursive.
1295     This limit is of use only if it is set smaller than \fImatch_limit\fP.
1296     .P
1297     Limiting the recursion depth limits the amount of stack that can be used, or,
1298     when PCRE has been compiled to use memory on the heap instead of the stack, the
1299     amount of heap memory that can be used.
1300     .P
1301     The default value for \fImatch_limit_recursion\fP can be set when PCRE is
1302     built; the default default is the same value as the default for
1303     \fImatch_limit\fP. You can override the default by suppling \fBpcre_exec()\fP
1304     with a \fBpcre_extra\fP block in which \fImatch_limit_recursion\fP is set, and
1305     PCRE_EXTRA_MATCH_LIMIT_RECURSION is set in the \fIflags\fP field. If the limit
1306     is exceeded, \fBpcre_exec()\fP returns PCRE_ERROR_RECURSIONLIMIT.
1307     .P
1308 ph10 440 The \fIcallout_data\fP field is used in conjunction with the "callout" feature,
1309     and is described in the
1310 nigel 75 .\" HREF
1311     \fBpcrecallout\fP
1312     .\"
1313     documentation.
1314     .P
1315     The \fItables\fP field is used to pass a character tables pointer to
1316     \fBpcre_exec()\fP; this overrides the value that is stored with the compiled
1317     pattern. A non-NULL value is stored with the compiled pattern only if custom
1318     tables were supplied to \fBpcre_compile()\fP via its \fItableptr\fP argument.
1319     If NULL is passed to \fBpcre_exec()\fP using this mechanism, it forces PCRE's
1320     internal tables to be used. This facility is helpful when re-using patterns
1321     that have been saved after compiling with an external set of tables, because
1322     the external tables might be at a different address when \fBpcre_exec()\fP is
1323     called. See the
1324     .\" HREF
1325     \fBpcreprecompile\fP
1326     .\"
1327     documentation for a discussion of saving compiled patterns for later use.
1328 ph10 510 .P
1329     If PCRE_EXTRA_MARK is set in the \fIflags\fP field, the \fImark\fP field must
1330 ph10 512 be set to point to a \fBchar *\fP variable. If the pattern contains any
1331 ph10 510 backtracking control verbs such as (*MARK:NAME), and the execution ends up with
1332     a name to pass back, a pointer to the name string (zero terminated) is placed
1333     in the variable pointed to by the \fImark\fP field. The names are within the
1334     compiled pattern; if you wish to retain such a name you must copy it before
1335     freeing the memory of a compiled pattern. If there is no name to pass back, the
1336     variable pointed to by the \fImark\fP field set to NULL. For details of the
1337     backtracking control verbs, see the section entitled
1338     .\" HTML <a href="pcrepattern#backtrackcontrol">
1339     .\" </a>
1340     "Backtracking control"
1341     .\"
1342     in the
1343     .\" HREF
1344     \fBpcrepattern\fP
1345     .\"
1346     documentation.
1347 nigel 75 .
1348 ph10 510 .
1349 ph10 226 .\" HTML <a name="execoptions"></a>
1350 nigel 75 .SS "Option bits for \fBpcre_exec()\fP"
1351     .rs
1352     .sp
1353     The unused bits of the \fIoptions\fP argument for \fBpcre_exec()\fP must be
1354 nigel 91 zero. The only bits that may be set are PCRE_ANCHORED, PCRE_NEWLINE_\fIxxx\fP,
1355 ph10 442 PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY, PCRE_NOTEMPTY_ATSTART,
1356     PCRE_NO_START_OPTIMIZE, PCRE_NO_UTF8_CHECK, PCRE_PARTIAL_SOFT, and
1357     PCRE_PARTIAL_HARD.
1358 nigel 75 .sp
1359     PCRE_ANCHORED
1360     .sp
1361     The PCRE_ANCHORED option limits \fBpcre_exec()\fP to matching at the first
1362     matching position. If a pattern was compiled with PCRE_ANCHORED, or turned out
1363     to be anchored by virtue of its contents, it cannot be made unachored at
1364     matching time.
1365     .sp
1366 ph10 231 PCRE_BSR_ANYCRLF
1367     PCRE_BSR_UNICODE
1368     .sp
1369     These options (which are mutually exclusive) control what the \eR escape
1370     sequence matches. The choice is either to match only CR, LF, or CRLF, or to
1371     match any Unicode newline sequence. These options override the choice that was
1372     made or defaulted when the pattern was compiled.
1373     .sp
1374 nigel 91 PCRE_NEWLINE_CR
1375     PCRE_NEWLINE_LF
1376     PCRE_NEWLINE_CRLF
1377 ph10 150 PCRE_NEWLINE_ANYCRLF
1378 nigel 93 PCRE_NEWLINE_ANY
1379 nigel 91 .sp
1380     These options override the newline definition that was chosen or defaulted when
1381 nigel 93 the pattern was compiled. For details, see the description of
1382     \fBpcre_compile()\fP above. During matching, the newline choice affects the
1383     behaviour of the dot, circumflex, and dollar metacharacters. It may also alter
1384     the way the match position is advanced after a match failure for an unanchored
1385 ph10 227 pattern.
1386 ph10 225 .P
1387 ph10 226 When PCRE_NEWLINE_CRLF, PCRE_NEWLINE_ANYCRLF, or PCRE_NEWLINE_ANY is set, and a
1388     match attempt for an unanchored pattern fails when the current position is at a
1389 ph10 230 CRLF sequence, and the pattern contains no explicit matches for CR or LF
1390 ph10 226 characters, the match position is advanced by two characters instead of one, in
1391     other words, to after the CRLF.
1392     .P
1393 ph10 227 The above rule is a compromise that makes the most common cases work as
1394     expected. For example, if the pattern is .+A (and the PCRE_DOTALL option is not
1395     set), it does not match the string "\er\enA" because, after failing at the
1396     start, it skips both the CR and the LF before retrying. However, the pattern
1397     [\er\en]A does match that string, because it contains an explicit CR or LF
1398 ph10 226 reference, and so advances only by one character after the first failure.
1399     .P
1400 ph10 231 An explicit match for CR of LF is either a literal appearance of one of those
1401     characters, or one of the \er or \en escape sequences. Implicit matches such as
1402 ph10 230 [^X] do not count, nor does \es (which includes CR and LF in the characters
1403     that it matches).
1404     .P
1405 ph10 226 Notwithstanding the above, anomalous effects may still occur when CRLF is a
1406     valid newline sequence and explicit \er or \en escapes appear in the pattern.
1407 nigel 91 .sp
1408 nigel 63 PCRE_NOTBOL
1409 nigel 75 .sp
1410     This option specifies that first character of the subject string is not the
1411     beginning of a line, so the circumflex metacharacter should not match before
1412     it. Setting this without PCRE_MULTILINE (at compile time) causes circumflex
1413     never to match. This option affects only the behaviour of the circumflex
1414     metacharacter. It does not affect \eA.
1415     .sp
1416 nigel 63 PCRE_NOTEOL
1417 nigel 75 .sp
1418     This option specifies that the end of the subject string is not the end of a
1419     line, so the dollar metacharacter should not match it nor (except in multiline
1420     mode) a newline immediately before it. Setting this without PCRE_MULTILINE (at
1421     compile time) causes dollar never to match. This option affects only the
1422     behaviour of the dollar metacharacter. It does not affect \eZ or \ez.
1423     .sp
1424 nigel 63 PCRE_NOTEMPTY
1425 nigel 75 .sp
1426 nigel 63 An empty string is not considered to be a valid match if this option is set. If
1427     there are alternatives in the pattern, they are tried. If all the alternatives
1428     match the empty string, the entire match fails. For example, if the pattern
1429 nigel 75 .sp
1430 nigel 63 a?b?
1431 nigel 75 .sp
1432 ph10 442 is applied to a string not beginning with "a" or "b", it matches an empty
1433 nigel 63 string at the start of the subject. With PCRE_NOTEMPTY set, this match is not
1434     valid, so PCRE searches further into the string for occurrences of "a" or "b".
1435 ph10 442 .sp
1436     PCRE_NOTEMPTY_ATSTART
1437     .sp
1438 ph10 461 This is like PCRE_NOTEMPTY, except that an empty string match that is not at
1439 ph10 442 the start of the subject is permitted. If the pattern is anchored, such a match
1440     can occur only if the pattern contains \eK.
1441 nigel 75 .P
1442 ph10 442 Perl has no direct equivalent of PCRE_NOTEMPTY or PCRE_NOTEMPTY_ATSTART, but it
1443     does make a special case of a pattern match of the empty string within its
1444     \fBsplit()\fP function, and when using the /g modifier. It is possible to
1445     emulate Perl's behaviour after matching a null string by first trying the match
1446     again at the same offset with PCRE_NOTEMPTY_ATSTART and PCRE_ANCHORED, and then
1447     if that fails, by advancing the starting offset (see below) and trying an
1448     ordinary match again. There is some code that demonstrates how to do this in
1449     the
1450 ph10 429 .\" HREF
1451     \fBpcredemo\fP
1452     .\"
1453     sample program.
1454 nigel 75 .sp
1455 ph10 389 PCRE_NO_START_OPTIMIZE
1456     .sp
1457 ph10 392 There are a number of optimizations that \fBpcre_exec()\fP uses at the start of
1458 ph10 542 a match, in order to speed up the process. For example, if it is known that an
1459     unanchored match must start with a specific character, it searches the subject
1460     for that character, and fails immediately if it cannot find it, without
1461 ph10 545 actually running the main matching function. This means that a special item
1462 ph10 542 such as (*COMMIT) at the start of a pattern is not considered until after a
1463 ph10 546 suitable starting point for the match has been found. When callouts or (*MARK)
1464     items are in use, these "start-up" optimizations can cause them to be skipped
1465     if the pattern is never actually used. The start-up optimizations are in effect
1466     a pre-scan of the subject that takes place before the pattern is run.
1467     .P
1468     The PCRE_NO_START_OPTIMIZE option disables the start-up optimizations, possibly
1469     causing performance to suffer, but ensuring that in cases where the result is
1470     "no match", the callouts do occur, and that items such as (*COMMIT) and (*MARK)
1471     are considered at every possible starting position in the subject string.
1472     Setting PCRE_NO_START_OPTIMIZE can change the outcome of a matching operation.
1473     Consider the pattern
1474 ph10 389 .sp
1475 ph10 546 (*COMMIT)ABC
1476     .sp
1477     When this is compiled, PCRE records the fact that a match must start with the
1478     character "A". Suppose the subject string is "DEFABC". The start-up
1479     optimization scans along the subject, finds "A" and runs the first match
1480     attempt from there. The (*COMMIT) item means that the pattern must match the
1481     current starting position, which in this case, it does. However, if the same
1482     match is run with PCRE_NO_START_OPTIMIZE set, the initial scan along the
1483     subject string does not happen. The first match attempt is run starting from
1484     "D" and when this fails, (*COMMIT) prevents any further matches being tried, so
1485     the overall result is "no match". If the pattern is studied, more start-up
1486     optimizations may be used. For example, a minimum length for the subject may be
1487     recorded. Consider the pattern
1488     .sp
1489     (*MARK:A)(X|Y)
1490     .sp
1491     The minimum length for a match is one character. If the subject is "ABC", there
1492     will be attempts to match "ABC", "BC", "C", and then finally an empty string.
1493     If the pattern is studied, the final attempt does not take place, because PCRE
1494     knows that the subject is too short, and so the (*MARK) is never encountered.
1495     In this case, studying the pattern does not affect the overall match result,
1496     which is still "no match", but it does affect the auxiliary information that is
1497     returned.
1498     .sp
1499 nigel 75 PCRE_NO_UTF8_CHECK
1500     .sp
1501     When PCRE_UTF8 is set at compile time, the validity of the subject as a UTF-8
1502     string is automatically checked when \fBpcre_exec()\fP is subsequently called.
1503 ph10 211 The value of \fIstartoffset\fP is also checked to ensure that it points to the
1504     start of a UTF-8 character. There is a discussion about the validity of UTF-8
1505     strings in the
1506     .\" HTML <a href="pcre.html#utf8strings">
1507     .\" </a>
1508     section on UTF-8 support
1509     .\"
1510     in the main
1511     .\" HREF
1512     \fBpcre\fP
1513     .\"
1514     page. If an invalid UTF-8 sequence of bytes is found, \fBpcre_exec()\fP returns
1515     the error PCRE_ERROR_BADUTF8. If \fIstartoffset\fP contains an invalid value,
1516 ph10 209 PCRE_ERROR_BADUTF8_OFFSET is returned.
1517 nigel 75 .P
1518     If you already know that your subject is valid, and you want to skip these
1519     checks for performance reasons, you can set the PCRE_NO_UTF8_CHECK option when
1520     calling \fBpcre_exec()\fP. You might want to do this for the second and
1521     subsequent calls to \fBpcre_exec()\fP if you are making repeated calls to find
1522     all the matches in a single subject string. However, you should be sure that
1523     the value of \fIstartoffset\fP points to the start of a UTF-8 character. When
1524     PCRE_NO_UTF8_CHECK is set, the effect of passing an invalid UTF-8 string as a
1525     subject, or a value of \fIstartoffset\fP that does not point to the start of a
1526     UTF-8 character, is undefined. Your program may crash.
1527     .sp
1528 ph10 461 PCRE_PARTIAL_HARD
1529 ph10 428 PCRE_PARTIAL_SOFT
1530 nigel 75 .sp
1531 ph10 428 These options turn on the partial matching feature. For backwards
1532     compatibility, PCRE_PARTIAL is a synonym for PCRE_PARTIAL_SOFT. A partial match
1533     occurs if the end of the subject string is reached successfully, but there are
1534     not enough subject characters to complete the match. If this happens when
1535     PCRE_PARTIAL_HARD is set, \fBpcre_exec()\fP immediately returns
1536     PCRE_ERROR_PARTIAL. Otherwise, if PCRE_PARTIAL_SOFT is set, matching continues
1537     by testing any other alternatives. Only if they all fail is PCRE_ERROR_PARTIAL
1538     returned (instead of PCRE_ERROR_NOMATCH). The portion of the string that
1539 ph10 435 was inspected when the partial match was found is set as the first matching
1540     string. There is a more detailed discussion in the
1541 nigel 75 .\" HREF
1542     \fBpcrepartial\fP
1543     .\"
1544     documentation.
1545     .
1546     .SS "The string to be matched by \fBpcre_exec()\fP"
1547     .rs
1548     .sp
1549     The subject string is passed to \fBpcre_exec()\fP as a pointer in
1550 ph10 368 \fIsubject\fP, a length (in bytes) in \fIlength\fP, and a starting byte offset
1551     in \fIstartoffset\fP. In UTF-8 mode, the byte offset must point to the start of
1552     a UTF-8 character. Unlike the pattern string, the subject may contain binary
1553     zero bytes. When the starting offset is zero, the search for a match starts at
1554     the beginning of the subject, and this is by far the most common case.
1555 nigel 75 .P
1556 nigel 63 A non-zero starting offset is useful when searching for another match in the
1557 nigel 75 same subject by calling \fBpcre_exec()\fP again after a previous success.
1558     Setting \fIstartoffset\fP differs from just passing over a shortened string and
1559 nigel 63 setting PCRE_NOTBOL in the case of a pattern that begins with any kind of
1560     lookbehind. For example, consider the pattern
1561 nigel 75 .sp
1562     \eBiss\eB
1563     .sp
1564     which finds occurrences of "iss" in the middle of words. (\eB matches only if
1565 nigel 63 the current position in the subject is not a word boundary.) When applied to
1566 nigel 75 the string "Mississipi" the first call to \fBpcre_exec()\fP finds the first
1567     occurrence. If \fBpcre_exec()\fP is called again with just the remainder of the
1568     subject, namely "issipi", it does not match, because \eB is always false at the
1569 nigel 63 start of the subject, which is deemed to be a word boundary. However, if
1570 nigel 75 \fBpcre_exec()\fP is passed the entire string again, but with \fIstartoffset\fP
1571 nigel 63 set to 4, it finds the second occurrence of "iss" because it is able to look
1572     behind the starting point to discover that it is preceded by a letter.
1573 nigel 75 .P
1574 nigel 63 If a non-zero starting offset is passed when the pattern is anchored, one
1575 nigel 75 attempt to match at the given offset is made. This can only succeed if the
1576 nigel 63 pattern does not require the match to be at the start of the subject.
1577 nigel 75 .
1578     .SS "How \fBpcre_exec()\fP returns captured substrings"
1579     .rs
1580     .sp
1581 nigel 63 In general, a pattern matches a certain portion of the subject, and in
1582     addition, further substrings from the subject may be picked out by parts of the
1583     pattern. Following the usage in Jeffrey Friedl's book, this is called
1584     "capturing" in what follows, and the phrase "capturing subpattern" is used for
1585     a fragment of a pattern that picks out a substring. PCRE supports several other
1586     kinds of parenthesized subpattern that do not cause substrings to be captured.
1587 nigel 75 .P
1588 ph10 368 Captured substrings are returned to the caller via a vector of integers whose
1589     address is passed in \fIovector\fP. The number of elements in the vector is
1590     passed in \fIovecsize\fP, which must be a non-negative number. \fBNote\fP: this
1591     argument is NOT the size of \fIovector\fP in bytes.
1592 nigel 75 .P
1593     The first two-thirds of the vector is used to pass back captured substrings,
1594     each substring using a pair of integers. The remaining third of the vector is
1595     used as workspace by \fBpcre_exec()\fP while matching capturing subpatterns,
1596 ph10 368 and is not available for passing back information. The number passed in
1597 nigel 75 \fIovecsize\fP should always be a multiple of three. If it is not, it is
1598     rounded down.
1599     .P
1600     When a match is successful, information about captured substrings is returned
1601     in pairs of integers, starting at the beginning of \fIovector\fP, and
1602 ph10 371 continuing up to two-thirds of its length at the most. The first element of
1603 ph10 368 each pair is set to the byte offset of the first character in a substring, and
1604     the second is set to the byte offset of the first character after the end of a
1605     substring. \fBNote\fP: these values are always byte offsets, even in UTF-8
1606     mode. They are not character counts.
1607 nigel 75 .P
1608 ph10 368 The first pair of integers, \fIovector[0]\fP and \fIovector[1]\fP, identify the
1609     portion of the subject string matched by the entire pattern. The next pair is
1610     used for the first capturing subpattern, and so on. The value returned by
1611     \fBpcre_exec()\fP is one more than the highest numbered pair that has been set.
1612     For example, if two substrings have been captured, the returned value is 3. If
1613     there are no capturing subpatterns, the return value from a successful match is
1614     1, indicating that just the first pair of offsets has been set.
1615     .P
1616 nigel 63 If a capturing subpattern is matched repeatedly, it is the last portion of the
1617 nigel 75 string that it matched that is returned.
1618     .P
1619     If the vector is too small to hold all the captured substring offsets, it is
1620     used as far as possible (up to two-thirds of its length), and the function
1621 ph10 368 returns a value of zero. If the substring offsets are not of interest,
1622     \fBpcre_exec()\fP may be called with \fIovector\fP passed as NULL and
1623 nigel 75 \fIovecsize\fP as zero. However, if the pattern contains back references and
1624     the \fIovector\fP is not big enough to remember the related substrings, PCRE
1625     has to get additional memory for use during matching. Thus it is usually
1626     advisable to supply an \fIovector\fP.
1627     .P
1628 ph10 456 The \fBpcre_fullinfo()\fP function can be used to find out how many capturing
1629 nigel 63 subpatterns there are in a compiled pattern. The smallest size for
1630 nigel 75 \fIovector\fP that will allow for \fIn\fP captured substrings, in addition to
1631     the offsets of the substring matched by the whole pattern, is (\fIn\fP+1)*3.
1632 nigel 91 .P
1633     It is possible for capturing subpattern number \fIn+1\fP to match some part of
1634     the subject when subpattern \fIn\fP has not been used at all. For example, if
1635     the string "abc" is matched against the pattern (a|(z))(bc) the return from the
1636     function is 4, and subpatterns 1 and 3 are matched, but 2 is not. When this
1637     happens, both values in the offset pairs corresponding to unused subpatterns
1638     are set to -1.
1639     .P
1640     Offset values that correspond to unused subpatterns at the end of the
1641     expression are also set to -1. For example, if the string "abc" is matched
1642     against the pattern (abc)(x(yz)?)? subpatterns 2 and 3 are not matched. The
1643     return from the function is 2, because the highest used capturing subpattern
1644     number is 1. However, you can refer to the offsets for the second and third
1645     capturing subpatterns if you wish (assuming the vector is large enough, of
1646     course).
1647     .P
1648     Some convenience functions are provided for extracting the captured substrings
1649     as separate strings. These are described below.
1650 nigel 75 .
1651 nigel 77 .\" HTML <a name="errorlist"></a>
1652 nigel 91 .SS "Error return values from \fBpcre_exec()\fP"
1653 nigel 75 .rs
1654     .sp
1655     If \fBpcre_exec()\fP fails, it returns a negative number. The following are
1656 nigel 63 defined in the header file:
1657 nigel 75 .sp
1658 nigel 63 PCRE_ERROR_NOMATCH (-1)
1659 nigel 75 .sp
1660 nigel 63 The subject string did not match the pattern.
1661 nigel 75 .sp
1662 nigel 63 PCRE_ERROR_NULL (-2)
1663 nigel 75 .sp
1664     Either \fIcode\fP or \fIsubject\fP was passed as NULL, or \fIovector\fP was
1665     NULL and \fIovecsize\fP was not zero.
1666     .sp
1667 nigel 63 PCRE_ERROR_BADOPTION (-3)
1668 nigel 75 .sp
1669     An unrecognized bit was set in the \fIoptions\fP argument.
1670     .sp
1671 nigel 63 PCRE_ERROR_BADMAGIC (-4)
1672 nigel 75 .sp
1673 nigel 63 PCRE stores a 4-byte "magic number" at the start of the compiled code, to catch
1674 nigel 75 the case when it is passed a junk pointer and to detect when a pattern that was
1675     compiled in an environment of one endianness is run in an environment with the
1676     other endianness. This is the error that PCRE gives when the magic number is
1677     not present.
1678     .sp
1679 nigel 93 PCRE_ERROR_UNKNOWN_OPCODE (-5)
1680 nigel 75 .sp
1681 nigel 63 While running the pattern match, an unknown item was encountered in the
1682     compiled pattern. This error could be caused by a bug in PCRE or by overwriting
1683     of the compiled pattern.
1684 nigel 75 .sp
1685 nigel 63 PCRE_ERROR_NOMEMORY (-6)
1686 nigel 75 .sp
1687     If a pattern contains back references, but the \fIovector\fP that is passed to
1688     \fBpcre_exec()\fP is not big enough to remember the referenced substrings, PCRE
1689 nigel 63 gets a block of memory at the start of matching to use for this purpose. If the
1690 nigel 75 call via \fBpcre_malloc()\fP fails, this error is given. The memory is
1691     automatically freed at the end of matching.
1692 ph10 531 .P
1693 ph10 535 This error is also given if \fBpcre_stack_malloc()\fP fails in
1694 ph10 531 \fBpcre_exec()\fP. This can happen only when PCRE has been compiled with
1695     \fB--disable-stack-for-recursion\fP.
1696 nigel 75 .sp
1697 nigel 63 PCRE_ERROR_NOSUBSTRING (-7)
1698 nigel 75 .sp
1699     This error is used by the \fBpcre_copy_substring()\fP,
1700     \fBpcre_get_substring()\fP, and \fBpcre_get_substring_list()\fP functions (see
1701     below). It is never returned by \fBpcre_exec()\fP.
1702     .sp
1703 nigel 63 PCRE_ERROR_MATCHLIMIT (-8)
1704 nigel 75 .sp
1705 nigel 87 The backtracking limit, as specified by the \fImatch_limit\fP field in a
1706     \fBpcre_extra\fP structure (or defaulted) was reached. See the description
1707     above.
1708     .sp
1709 nigel 63 PCRE_ERROR_CALLOUT (-9)
1710 nigel 75 .sp
1711     This error is never generated by \fBpcre_exec()\fP itself. It is provided for
1712 nigel 63 use by callout functions that want to yield a distinctive error code. See the
1713 nigel 75 .\" HREF
1714     \fBpcrecallout\fP
1715     .\"
1716     documentation for details.
1717     .sp
1718 nigel 73 PCRE_ERROR_BADUTF8 (-10)
1719 nigel 75 .sp
1720 nigel 71 A string that contains an invalid UTF-8 byte sequence was passed as a subject.
1721 nigel 75 .sp
1722 nigel 73 PCRE_ERROR_BADUTF8_OFFSET (-11)
1723 nigel 75 .sp
1724 nigel 73 The UTF-8 byte sequence that was passed as a subject was valid, but the value
1725 nigel 75 of \fIstartoffset\fP did not point to the beginning of a UTF-8 character.
1726     .sp
1727 nigel 77 PCRE_ERROR_PARTIAL (-12)
1728 nigel 75 .sp
1729     The subject string did not match, but it did match partially. See the
1730     .\" HREF
1731     \fBpcrepartial\fP
1732     .\"
1733     documentation for details of partial matching.
1734     .sp
1735 nigel 77 PCRE_ERROR_BADPARTIAL (-13)
1736 nigel 75 .sp
1737 ph10 426 This code is no longer in use. It was formerly returned when the PCRE_PARTIAL
1738     option was used with a compiled pattern containing items that were not
1739 ph10 461 supported for partial matching. From release 8.00 onwards, there are no
1740 ph10 426 restrictions on partial matching.
1741 nigel 75 .sp
1742 nigel 77 PCRE_ERROR_INTERNAL (-14)
1743 nigel 75 .sp
1744     An unexpected internal error has occurred. This error could be caused by a bug
1745     in PCRE or by overwriting of the compiled pattern.
1746     .sp
1747 nigel 77 PCRE_ERROR_BADCOUNT (-15)
1748 nigel 75 .sp
1749     This error is given if the value of the \fIovecsize\fP argument is negative.
1750 nigel 93 .sp
1751     PCRE_ERROR_RECURSIONLIMIT (-21)
1752     .sp
1753     The internal recursion limit, as specified by the \fImatch_limit_recursion\fP
1754     field in a \fBpcre_extra\fP structure (or defaulted) was reached. See the
1755     description above.
1756     .sp
1757     PCRE_ERROR_BADNEWLINE (-23)
1758     .sp
1759     An invalid combination of PCRE_NEWLINE_\fIxxx\fP options was given.
1760     .P
1761 ph10 197 Error numbers -16 to -20 and -22 are not used by \fBpcre_exec()\fP.
1762 nigel 75 .
1763     .
1764     .SH "EXTRACTING CAPTURED SUBSTRINGS BY NUMBER"
1765 nigel 63 .rs
1766     .sp
1767 nigel 75 .B int pcre_copy_substring(const char *\fIsubject\fP, int *\fIovector\fP,
1768 nigel 63 .ti +5n
1769 nigel 75 .B int \fIstringcount\fP, int \fIstringnumber\fP, char *\fIbuffer\fP,
1770 nigel 63 .ti +5n
1771 nigel 75 .B int \fIbuffersize\fP);
1772 nigel 63 .PP
1773 nigel 75 .B int pcre_get_substring(const char *\fIsubject\fP, int *\fIovector\fP,
1774 nigel 63 .ti +5n
1775 nigel 75 .B int \fIstringcount\fP, int \fIstringnumber\fP,
1776 nigel 63 .ti +5n
1777 nigel 75 .B const char **\fIstringptr\fP);
1778 nigel 63 .PP
1779 nigel 75 .B int pcre_get_substring_list(const char *\fIsubject\fP,
1780 nigel 63 .ti +5n
1781 nigel 75 .B int *\fIovector\fP, int \fIstringcount\fP, "const char ***\fIlistptr\fP);"
1782 nigel 63 .PP
1783     Captured substrings can be accessed directly by using the offsets returned by
1784 nigel 75 \fBpcre_exec()\fP in \fIovector\fP. For convenience, the functions
1785     \fBpcre_copy_substring()\fP, \fBpcre_get_substring()\fP, and
1786     \fBpcre_get_substring_list()\fP are provided for extracting captured substrings
1787 nigel 63 as new, separate, zero-terminated strings. These functions identify substrings
1788     by number. The next section describes functions for extracting named
1789 nigel 91 substrings.
1790 nigel 75 .P
1791 nigel 91 A substring that contains a binary zero is correctly extracted and has a
1792     further zero added on the end, but the result is not, of course, a C string.
1793     However, you can process such a string by referring to the length that is
1794     returned by \fBpcre_copy_substring()\fP and \fBpcre_get_substring()\fP.
1795     Unfortunately, the interface to \fBpcre_get_substring_list()\fP is not adequate
1796     for handling strings containing binary zeros, because the end of the final
1797     string is not independently indicated.
1798     .P
1799 nigel 63 The first three arguments are the same for all three of these functions:
1800 nigel 75 \fIsubject\fP is the subject string that has just been successfully matched,
1801     \fIovector\fP is a pointer to the vector of integer offsets that was passed to
1802     \fBpcre_exec()\fP, and \fIstringcount\fP is the number of substrings that were
1803 nigel 63 captured by the match, including the substring that matched the entire regular
1804 nigel 75 expression. This is the value returned by \fBpcre_exec()\fP if it is greater
1805     than zero. If \fBpcre_exec()\fP returned zero, indicating that it ran out of
1806     space in \fIovector\fP, the value passed as \fIstringcount\fP should be the
1807     number of elements in the vector divided by three.
1808     .P
1809     The functions \fBpcre_copy_substring()\fP and \fBpcre_get_substring()\fP
1810     extract a single substring, whose number is given as \fIstringnumber\fP. A
1811     value of zero extracts the substring that matched the entire pattern, whereas
1812     higher values extract the captured substrings. For \fBpcre_copy_substring()\fP,
1813     the string is placed in \fIbuffer\fP, whose length is given by
1814     \fIbuffersize\fP, while for \fBpcre_get_substring()\fP a new block of memory is
1815     obtained via \fBpcre_malloc\fP, and its address is returned via
1816     \fIstringptr\fP. The yield of the function is the length of the string, not
1817 nigel 93 including the terminating zero, or one of these error codes:
1818 nigel 75 .sp
1819 nigel 63 PCRE_ERROR_NOMEMORY (-6)
1820 nigel 75 .sp
1821     The buffer was too small for \fBpcre_copy_substring()\fP, or the attempt to get
1822     memory failed for \fBpcre_get_substring()\fP.
1823     .sp
1824 nigel 63 PCRE_ERROR_NOSUBSTRING (-7)
1825 nigel 75 .sp
1826     There is no substring whose number is \fIstringnumber\fP.
1827     .P
1828     The \fBpcre_get_substring_list()\fP function extracts all available substrings
1829 nigel 63 and builds a list of pointers to them. All this is done in a single block of
1830 nigel 75 memory that is obtained via \fBpcre_malloc\fP. The address of the memory block
1831     is returned via \fIlistptr\fP, which is also the start of the list of string
1832 nigel 63 pointers. The end of the list is marked by a NULL pointer. The yield of the
1833 nigel 93 function is zero if all went well, or the error code
1834 nigel 75 .sp
1835 nigel 63 PCRE_ERROR_NOMEMORY (-6)
1836 nigel 75 .sp
1837 nigel 63 if the attempt to get the memory block failed.
1838 nigel 75 .P
1839 nigel 63 When any of these functions encounter a substring that is unset, which can
1840 nigel 75 happen when capturing subpattern number \fIn+1\fP matches some part of the
1841     subject, but subpattern \fIn\fP has not been used at all, they return an empty
1842 nigel 63 string. This can be distinguished from a genuine zero-length substring by
1843 nigel 75 inspecting the appropriate offset in \fIovector\fP, which is negative for unset
1844 nigel 63 substrings.
1845 nigel 75 .P
1846     The two convenience functions \fBpcre_free_substring()\fP and
1847     \fBpcre_free_substring_list()\fP can be used to free the memory returned by
1848     a previous call of \fBpcre_get_substring()\fP or
1849     \fBpcre_get_substring_list()\fP, respectively. They do nothing more than call
1850     the function pointed to by \fBpcre_free\fP, which of course could be called
1851 nigel 63 directly from a C program. However, PCRE is used in some situations where it is
1852 nigel 91 linked via a special interface to another programming language that cannot use
1853 nigel 75 \fBpcre_free\fP directly; it is for these cases that the functions are
1854 nigel 63 provided.
1855 nigel 75 .
1856     .
1857     .SH "EXTRACTING CAPTURED SUBSTRINGS BY NAME"
1858 nigel 63 .rs
1859     .sp
1860 nigel 75 .B int pcre_get_stringnumber(const pcre *\fIcode\fP,
1861 nigel 63 .ti +5n
1862 nigel 75 .B const char *\fIname\fP);
1863 nigel 63 .PP
1864 nigel 75 .B int pcre_copy_named_substring(const pcre *\fIcode\fP,
1865 nigel 63 .ti +5n
1866 nigel 75 .B const char *\fIsubject\fP, int *\fIovector\fP,
1867     .ti +5n
1868     .B int \fIstringcount\fP, const char *\fIstringname\fP,
1869     .ti +5n
1870     .B char *\fIbuffer\fP, int \fIbuffersize\fP);
1871 nigel 63 .PP
1872 nigel 75 .B int pcre_get_named_substring(const pcre *\fIcode\fP,
1873 nigel 63 .ti +5n
1874 nigel 75 .B const char *\fIsubject\fP, int *\fIovector\fP,
1875 nigel 63 .ti +5n
1876 nigel 75 .B int \fIstringcount\fP, const char *\fIstringname\fP,
1877 nigel 63 .ti +5n
1878 nigel 75 .B const char **\fIstringptr\fP);
1879 nigel 63 .PP
1880 nigel 75 To extract a substring by name, you first have to find associated number.
1881     For example, for this pattern
1882     .sp
1883 nigel 93 (a+)b(?<xxx>\ed+)...
1884 nigel 75 .sp
1885 nigel 91 the number of the subpattern called "xxx" is 2. If the name is known to be
1886     unique (PCRE_DUPNAMES was not set), you can find the number from the name by
1887     calling \fBpcre_get_stringnumber()\fP. The first argument is the compiled
1888     pattern, and the second is the name. The yield of the function is the
1889 nigel 75 subpattern number, or PCRE_ERROR_NOSUBSTRING (-7) if there is no subpattern of
1890     that name.
1891     .P
1892     Given the number, you can extract the substring directly, or use one of the
1893     functions described in the previous section. For convenience, there are also
1894     two functions that do the whole job.
1895     .P
1896 nigel 91 Most of the arguments of \fBpcre_copy_named_substring()\fP and
1897     \fBpcre_get_named_substring()\fP are the same as those for the similarly named
1898 nigel 75 functions that extract by number. As these are described in the previous
1899     section, they are not re-described here. There are just two differences:
1900     .P
1901 nigel 63 First, instead of a substring number, a substring name is given. Second, there
1902     is an extra argument, given at the start, which is a pointer to the compiled
1903     pattern. This is needed in order to gain access to the name-to-number
1904     translation table.
1905 nigel 75 .P
1906     These functions call \fBpcre_get_stringnumber()\fP, and if it succeeds, they
1907 ph10 127 then call \fBpcre_copy_substring()\fP or \fBpcre_get_substring()\fP, as
1908     appropriate. \fBNOTE:\fP If PCRE_DUPNAMES is set and there are duplicate names,
1909 ph10 128 the behaviour may not be what you want (see the next section).
1910 ph10 385 .P
1911 ph10 457 \fBWarning:\fP If the pattern uses the (?| feature to set up multiple
1912     subpatterns with the same number, as described in the
1913     .\" HTML <a href="pcrepattern.html#dupsubpatternnumber">
1914     .\" </a>
1915     section on duplicate subpattern numbers
1916     .\"
1917     in the
1918     .\" HREF
1919     \fBpcrepattern\fP
1920     .\"
1921     page, you cannot use names to distinguish the different subpatterns, because
1922     names are not included in the compiled code. The matching process uses only
1923     numbers. For this reason, the use of different names for subpatterns of the
1924     same number causes an error at compile time.
1925 nigel 77 .
1926 nigel 91 .SH "DUPLICATE SUBPATTERN NAMES"
1927     .rs
1928     .sp
1929     .B int pcre_get_stringtable_entries(const pcre *\fIcode\fP,
1930     .ti +5n
1931     .B const char *\fIname\fP, char **\fIfirst\fP, char **\fIlast\fP);
1932     .PP
1933     When a pattern is compiled with the PCRE_DUPNAMES option, names for subpatterns
1934 ph10 457 are not required to be unique. (Duplicate names are always allowed for
1935     subpatterns with the same number, created by using the (?| feature. Indeed, if
1936     such subpatterns are named, they are required to use the same names.)
1937     .P
1938     Normally, patterns with duplicate names are such that in any one match, only
1939     one of the named subpatterns participates. An example is shown in the
1940 nigel 91 .\" HREF
1941     \fBpcrepattern\fP
1942     .\"
1943 ph10 208 documentation.
1944 ph10 203 .P
1945     When duplicates are present, \fBpcre_copy_named_substring()\fP and
1946     \fBpcre_get_named_substring()\fP return the first substring corresponding to
1947     the given name that is set. If none are set, PCRE_ERROR_NOSUBSTRING (-7) is
1948     returned; no data is returned. The \fBpcre_get_stringnumber()\fP function
1949     returns one of the numbers that are associated with the name, but it is not
1950     defined which it is.
1951     .P
1952 nigel 91 If you want to get full details of all captured substrings for a given name,
1953     you must use the \fBpcre_get_stringtable_entries()\fP function. The first
1954     argument is the compiled pattern, and the second is the name. The third and
1955     fourth are pointers to variables which are updated by the function. After it
1956     has run, they point to the first and last entries in the name-to-number table
1957     for the given name. The function itself returns the length of each entry, or
1958 nigel 93 PCRE_ERROR_NOSUBSTRING (-7) if there are none. The format of the table is
1959     described above in the section entitled \fIInformation about a pattern\fP.
1960     Given all the relevant entries for the name, you can extract each of their
1961     numbers, and hence the captured data, if any.
1962 nigel 91 .
1963     .
1964 nigel 77 .SH "FINDING ALL POSSIBLE MATCHES"
1965     .rs
1966     .sp
1967     The traditional matching function uses a similar algorithm to Perl, which stops
1968     when it finds the first match, starting at a given point in the subject. If you
1969     want to find all possible matches, or the longest possible match, consider
1970     using the alternative matching function (see below) instead. If you cannot use
1971     the alternative function, but still need to find all possible matches, you
1972     can kludge it up by making use of the callout facility, which is described in
1973     the
1974     .\" HREF
1975     \fBpcrecallout\fP
1976     .\"
1977     documentation.
1978 nigel 75 .P
1979 nigel 77 What you have to do is to insert a callout right at the end of the pattern.
1980     When your callout function is called, extract and save the current matched
1981     substring. Then return 1, which forces \fBpcre_exec()\fP to backtrack and try
1982     other alternatives. Ultimately, when it runs out of matches, \fBpcre_exec()\fP
1983     will yield PCRE_ERROR_NOMATCH.
1984     .
1985     .
1986     .\" HTML <a name="dfamatch"></a>
1987     .SH "MATCHING A PATTERN: THE ALTERNATIVE FUNCTION"
1988     .rs
1989     .sp
1990     .B int pcre_dfa_exec(const pcre *\fIcode\fP, "const pcre_extra *\fIextra\fP,"
1991     .ti +5n
1992     .B "const char *\fIsubject\fP," int \fIlength\fP, int \fIstartoffset\fP,
1993     .ti +5n
1994     .B int \fIoptions\fP, int *\fIovector\fP, int \fIovecsize\fP,
1995     .ti +5n
1996     .B int *\fIworkspace\fP, int \fIwscount\fP);
1997     .P
1998     The function \fBpcre_dfa_exec()\fP is called to match a subject string against
1999 nigel 93 a compiled pattern, using a matching algorithm that scans the subject string
2000     just once, and does not backtrack. This has different characteristics to the
2001     normal algorithm, and is not compatible with Perl. Some of the features of PCRE
2002     patterns are not supported. Nevertheless, there are times when this kind of
2003 ph10 461 matching can be useful. For a discussion of the two matching algorithms, and a
2004 ph10 435 list of features that \fBpcre_dfa_exec()\fP does not support, see the
2005 nigel 77 .\" HREF
2006     \fBpcrematching\fP
2007     .\"
2008     documentation.
2009     .P
2010     The arguments for the \fBpcre_dfa_exec()\fP function are the same as for
2011     \fBpcre_exec()\fP, plus two extras. The \fIovector\fP argument is used in a
2012     different way, and this is described below. The other common arguments are used
2013     in the same way as for \fBpcre_exec()\fP, so their description is not repeated
2014     here.
2015     .P
2016     The two additional arguments provide workspace for the function. The workspace
2017     vector should contain at least 20 elements. It is used for keeping track of
2018     multiple paths through the pattern tree. More workspace will be needed for
2019 nigel 91 patterns and subjects where there are a lot of potential matches.
2020 nigel 77 .P
2021 nigel 87 Here is an example of a simple call to \fBpcre_dfa_exec()\fP:
2022 nigel 77 .sp
2023     int rc;
2024     int ovector[10];
2025     int wspace[20];
2026 nigel 87 rc = pcre_dfa_exec(
2027 nigel 77 re, /* result of pcre_compile() */
2028     NULL, /* we didn't study the pattern */
2029     "some string", /* the subject string */
2030     11, /* the length of the subject string */
2031     0, /* start at offset 0 in the subject */
2032     0, /* default options */
2033     ovector, /* vector of integers for substring information */
2034     10, /* number of elements (NOT size in bytes) */
2035     wspace, /* working space vector */
2036     20); /* number of elements (NOT size in bytes) */
2037     .
2038     .SS "Option bits for \fBpcre_dfa_exec()\fP"
2039     .rs
2040     .sp
2041     The unused bits of the \fIoptions\fP argument for \fBpcre_dfa_exec()\fP must be
2042 nigel 91 zero. The only bits that may be set are PCRE_ANCHORED, PCRE_NEWLINE_\fIxxx\fP,
2043 ph10 442 PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY, PCRE_NOTEMPTY_ATSTART,
2044 ph10 542 PCRE_NO_UTF8_CHECK, PCRE_BSR_ANYCRLF, PCRE_BSR_UNICODE, PCRE_NO_START_OPTIMIZE,
2045     PCRE_PARTIAL_HARD, PCRE_PARTIAL_SOFT, PCRE_DFA_SHORTEST, and PCRE_DFA_RESTART.
2046     All but the last four of these are exactly the same as for \fBpcre_exec()\fP,
2047     so their description is not repeated here.
2048 nigel 77 .sp
2049 ph10 428 PCRE_PARTIAL_HARD
2050 ph10 461 PCRE_PARTIAL_SOFT
2051 nigel 77 .sp
2052 ph10 428 These have the same general effect as they do for \fBpcre_exec()\fP, but the
2053     details are slightly different. When PCRE_PARTIAL_HARD is set for
2054     \fBpcre_dfa_exec()\fP, it returns PCRE_ERROR_PARTIAL if the end of the subject
2055     is reached and there is still at least one matching possibility that requires
2056     additional characters. This happens even if some complete matches have also
2057     been found. When PCRE_PARTIAL_SOFT is set, the return code PCRE_ERROR_NOMATCH
2058     is converted into PCRE_ERROR_PARTIAL if the end of the subject is reached,
2059     there have been no complete matches, but there is still at least one matching
2060 ph10 435 possibility. The portion of the string that was inspected when the longest
2061     partial match was found is set as the first matching string in both cases.
2062 nigel 77 .sp
2063     PCRE_DFA_SHORTEST
2064     .sp
2065     Setting the PCRE_DFA_SHORTEST option causes the matching algorithm to stop as
2066 nigel 93 soon as it has found one match. Because of the way the alternative algorithm
2067     works, this is necessarily the shortest possible match at the first possible
2068     matching point in the subject string.
2069 nigel 77 .sp
2070     PCRE_DFA_RESTART
2071     .sp
2072 ph10 428 When \fBpcre_dfa_exec()\fP returns a partial match, it is possible to call it
2073     again, with additional subject characters, and have it continue with the same
2074     match. The PCRE_DFA_RESTART option requests this action; when it is set, the
2075     \fIworkspace\fP and \fIwscount\fP options must reference the same vector as
2076     before because data about the match so far is left in them after a partial
2077     match. There is more discussion of this facility in the
2078 nigel 77 .\" HREF
2079     \fBpcrepartial\fP
2080     .\"
2081     documentation.
2082     .
2083     .SS "Successful returns from \fBpcre_dfa_exec()\fP"
2084     .rs
2085     .sp
2086     When \fBpcre_dfa_exec()\fP succeeds, it may have matched more than one
2087     substring in the subject. Note, however, that all the matches from one run of
2088     the function start at the same point in the subject. The shorter matches are
2089     all initial substrings of the longer matches. For example, if the pattern
2090     .sp
2091     <.*>
2092     .sp
2093     is matched against the string
2094     .sp
2095     This is <something> <something else> <something further> no more
2096     .sp
2097     the three matched strings are
2098     .sp
2099     <something>
2100     <something> <something else>
2101     <something> <something else> <something further>
2102     .sp
2103     On success, the yield of the function is a number greater than zero, which is
2104     the number of matched substrings. The substrings themselves are returned in
2105     \fIovector\fP. Each string uses two elements; the first is the offset to the
2106 nigel 93 start, and the second is the offset to the end. In fact, all the strings have
2107     the same start offset. (Space could have been saved by giving this only once,
2108     but it was decided to retain some compatibility with the way \fBpcre_exec()\fP
2109     returns data, even though the meaning of the strings is different.)
2110 nigel 77 .P
2111     The strings are returned in reverse order of length; that is, the longest
2112     matching string is given first. If there were too many matches to fit into
2113     \fIovector\fP, the yield of the function is zero, and the vector is filled with
2114     the longest matches.
2115     .
2116     .SS "Error returns from \fBpcre_dfa_exec()\fP"
2117     .rs
2118     .sp
2119     The \fBpcre_dfa_exec()\fP function returns a negative number when it fails.
2120     Many of the errors are the same as for \fBpcre_exec()\fP, and these are
2121     described
2122     .\" HTML <a href="#errorlist">
2123     .\" </a>
2124     above.
2125     .\"
2126     There are in addition the following errors that are specific to
2127     \fBpcre_dfa_exec()\fP:
2128     .sp
2129     PCRE_ERROR_DFA_UITEM (-16)
2130     .sp
2131     This return is given if \fBpcre_dfa_exec()\fP encounters an item in the pattern
2132     that it does not support, for instance, the use of \eC or a back reference.
2133     .sp
2134     PCRE_ERROR_DFA_UCOND (-17)
2135     .sp
2136 nigel 93 This return is given if \fBpcre_dfa_exec()\fP encounters a condition item that
2137     uses a back reference for the condition, or a test for recursion in a specific
2138     group. These are not supported.
2139 nigel 77 .sp
2140     PCRE_ERROR_DFA_UMLIMIT (-18)
2141     .sp
2142     This return is given if \fBpcre_dfa_exec()\fP is called with an \fIextra\fP
2143     block that contains a setting of the \fImatch_limit\fP field. This is not
2144     supported (it is meaningless).
2145     .sp
2146     PCRE_ERROR_DFA_WSSIZE (-19)
2147     .sp
2148     This return is given if \fBpcre_dfa_exec()\fP runs out of space in the
2149     \fIworkspace\fP vector.
2150     .sp
2151     PCRE_ERROR_DFA_RECURSE (-20)
2152     .sp
2153     When a recursive subpattern is processed, the matching function calls itself
2154     recursively, using private vectors for \fIovector\fP and \fIworkspace\fP. This
2155     error is given if the output vector is not large enough. This should be
2156     extremely rare, as a vector of size 1000 is used.
2157 nigel 93 .
2158     .
2159     .SH "SEE ALSO"
2160     .rs
2161     .sp
2162     \fBpcrebuild\fP(3), \fBpcrecallout\fP(3), \fBpcrecpp(3)\fP(3),
2163     \fBpcrematching\fP(3), \fBpcrepartial\fP(3), \fBpcreposix\fP(3),
2164     \fBpcreprecompile\fP(3), \fBpcresample\fP(3), \fBpcrestack\fP(3).
2165 ph10 99 .
2166     .
2167     .SH AUTHOR
2168     .rs
2169     .sp
2170     .nf
2171     Philip Hazel
2172     University Computing Service
2173     Cambridge CB2 3QH, England.
2174     .fi
2175     .
2176     .
2177     .SH REVISION
2178     .rs
2179     .sp
2180     .nf
2181 ph10 547 Last updated: 21 June 2010
2182 ph10 510 Copyright (c) 1997-2010 University of Cambridge.
2183 ph10 99 .fi

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