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

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