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


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