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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     way of using them is provided in the file called \fIpcredemo.c\fP in the source
139     distribution. The
140 nigel 75 .\" HREF
141     \fBpcresample\fP
142     .\"
143     documentation describes how to run it.
144     .P
145 nigel 77 A second matching function, \fBpcre_dfa_exec()\fP, which is not
146     Perl-compatible, is also provided. This uses a different algorithm for the
147 nigel 91 matching. The alternative algorithm finds all possible matches (at a given
148 nigel 93 point in the subject), and scans the subject just once. However, this algorithm
149     does not return captured substrings. A description of the two matching
150     algorithms and their advantages and disadvantages is given in the
151 nigel 77 .\" HREF
152     \fBpcrematching\fP
153     .\"
154     documentation.
155     .P
156 nigel 75 In addition to the main compiling and matching functions, there are convenience
157 nigel 77 functions for extracting captured substrings from a subject string that is
158     matched by \fBpcre_exec()\fP. They are:
159 nigel 75 .sp
160     \fBpcre_copy_substring()\fP
161     \fBpcre_copy_named_substring()\fP
162     \fBpcre_get_substring()\fP
163     \fBpcre_get_named_substring()\fP
164     \fBpcre_get_substring_list()\fP
165     \fBpcre_get_stringnumber()\fP
166 nigel 91 \fBpcre_get_stringtable_entries()\fP
167 nigel 75 .sp
168     \fBpcre_free_substring()\fP and \fBpcre_free_substring_list()\fP are also
169 nigel 63 provided, to free the memory used for extracted strings.
170 nigel 75 .P
171     The function \fBpcre_maketables()\fP is used to build a set of character tables
172 nigel 77 in the current locale for passing to \fBpcre_compile()\fP, \fBpcre_exec()\fP,
173     or \fBpcre_dfa_exec()\fP. This is an optional facility that is provided for
174     specialist use. Most commonly, no special tables are passed, in which case
175     internal tables that are generated when PCRE is built are used.
176 nigel 75 .P
177     The function \fBpcre_fullinfo()\fP is used to find out information about a
178     compiled pattern; \fBpcre_info()\fP is an obsolete version that returns only
179 nigel 63 some of the available information, but is retained for backwards compatibility.
180 nigel 75 The function \fBpcre_version()\fP returns a pointer to a string containing the
181 nigel 63 version of PCRE and its date of release.
182 nigel 75 .P
183 nigel 77 The function \fBpcre_refcount()\fP maintains a reference count in a data block
184     containing a compiled pattern. This is provided for the benefit of
185     object-oriented applications.
186     .P
187 nigel 75 The global variables \fBpcre_malloc\fP and \fBpcre_free\fP initially contain
188     the entry points of the standard \fBmalloc()\fP and \fBfree()\fP functions,
189 nigel 63 respectively. PCRE calls the memory management functions via these variables,
190     so a calling program can replace them if it wishes to intercept the calls. This
191     should be done before calling any PCRE functions.
192 nigel 75 .P
193     The global variables \fBpcre_stack_malloc\fP and \fBpcre_stack_free\fP are also
194 nigel 73 indirections to memory management functions. These special functions are used
195     only when PCRE is compiled to use the heap for remembering data, instead of
196 nigel 91 recursive function calls, when running the \fBpcre_exec()\fP function. See the
197     .\" HREF
198     \fBpcrebuild\fP
199     .\"
200     documentation for details of how to do this. It is a non-standard way of
201     building PCRE, for use in environments that have limited stacks. Because of the
202     greater use of memory management, it runs more slowly. Separate functions are
203     provided so that special-purpose external code can be used for this case. When
204     used, these functions are always called in a stack-like manner (last obtained,
205     first freed), and always for memory blocks of the same size. There is a
206     discussion about PCRE's stack usage in the
207     .\" HREF
208     \fBpcrestack\fP
209     .\"
210     documentation.
211 nigel 75 .P
212     The global variable \fBpcre_callout\fP initially contains NULL. It can be set
213 nigel 63 by the caller to a "callout" function, which PCRE will then call at specified
214 nigel 75 points during a matching operation. Details are given in the
215     .\" HREF
216     \fBpcrecallout\fP
217     .\"
218 nigel 63 documentation.
219 nigel 75 .
220     .
221 nigel 91 .SH NEWLINES
222 nigel 93 .rs
223 nigel 91 .sp
224 nigel 93 PCRE supports four different conventions for indicating line breaks in
225     strings: a single CR (carriage return) character, a single LF (linefeed)
226     character, the two-character sequence CRLF, or any Unicode newline sequence.
227     The Unicode newline sequences are the three just mentioned, plus the single
228     characters VT (vertical tab, U+000B), FF (formfeed, U+000C), NEL (next line,
229     U+0085), LS (line separator, U+2028), and PS (paragraph separator, U+2029).
230     .P
231     Each of the first three conventions is used by at least one operating system as
232     its standard newline sequence. When PCRE is built, a default can be specified.
233     The default default is LF, which is the Unix standard. When PCRE is run, the
234     default can be overridden, either when a pattern is compiled, or when it is
235     matched.
236     .P
237 nigel 91 In the PCRE documentation the word "newline" is used to mean "the character or
238 nigel 93 pair of characters that indicate a line break". The choice of newline
239     convention affects the handling of the dot, circumflex, and dollar
240     metacharacters, the handling of #-comments in /x mode, and, when CRLF is a
241     recognized line ending sequence, the match position advancement for a
242     non-anchored pattern. The choice of newline convention does not affect the
243     interpretation of the \en or \er escape sequences.
244 nigel 91 .
245     .
247     .rs
248     .sp
249     The PCRE functions can be used in multi-threading applications, with the
250 nigel 75 proviso that the memory management functions pointed to by \fBpcre_malloc\fP,
251     \fBpcre_free\fP, \fBpcre_stack_malloc\fP, and \fBpcre_stack_free\fP, and the
252     callout function pointed to by \fBpcre_callout\fP, are shared by all threads.
253     .P
254 nigel 63 The compiled form of a regular expression is not altered during matching, so
255     the same compiled pattern can safely be used by several threads at once.
256 nigel 75 .
257     .
259 nigel 63 .rs
260     .sp
261 nigel 75 The compiled form of a regular expression can be saved and re-used at a later
262     time, possibly by a different program, and even on a host other than the one on
263     which it was compiled. Details are given in the
264     .\" HREF
265     \fBpcreprecompile\fP
266     .\"
267     documentation.
268     .
269     .
271     .rs
272     .sp
273     .B int pcre_config(int \fIwhat\fP, void *\fIwhere\fP);
274 nigel 63 .PP
275 nigel 75 The function \fBpcre_config()\fP makes it possible for a PCRE client to
276 nigel 63 discover which optional features have been compiled into the PCRE library. The
277     .\" HREF
278 nigel 75 \fBpcrebuild\fP
279 nigel 63 .\"
280     documentation has more details about these optional features.
281 nigel 75 .P
282     The first argument for \fBpcre_config()\fP is an integer, specifying which
283 nigel 63 information is required; the second argument is a pointer to a variable into
284     which the information is placed. The following information is available:
285 nigel 75 .sp
286 nigel 63 PCRE_CONFIG_UTF8
287 nigel 75 .sp
288 nigel 63 The output is an integer that is set to one if UTF-8 support is available;
289     otherwise it is set to zero.
290 nigel 75 .sp
292     .sp
293     The output is an integer that is set to one if support for Unicode character
294     properties is available; otherwise it is set to zero.
295     .sp
297 nigel 75 .sp
298 nigel 91 The output is an integer whose value specifies the default character sequence
299 nigel 93 that is recognized as meaning "newline". The four values that are supported
300     are: 10 for LF, 13 for CR, 3338 for CRLF, and -1 for ANY. The default should
301     normally be the standard sequence for your operating system.
302 nigel 75 .sp
304 nigel 75 .sp
305 nigel 63 The output is an integer that contains the number of bytes used for internal
306     linkage in compiled regular expressions. The value is 2, 3, or 4. Larger values
307     allow larger regular expressions to be compiled, at the expense of slower
308     matching. The default value of 2 is sufficient for all but the most massive
309     patterns, since it allows the compiled pattern to be up to 64K in size.
310 nigel 75 .sp
312 nigel 75 .sp
313 nigel 63 The output is an integer that contains the threshold above which the POSIX
314 nigel 75 interface uses \fBmalloc()\fP for output vectors. Further details are given in
315     the
316     .\" HREF
317     \fBpcreposix\fP
318     .\"
319     documentation.
320     .sp
322 nigel 75 .sp
323 nigel 63 The output is an integer that gives the default limit for the number of
324 nigel 75 internal matching function calls in a \fBpcre_exec()\fP execution. Further
325     details are given with \fBpcre_exec()\fP below.
326     .sp
328     .sp
329     The output is an integer that gives the default limit for the depth of
330     recursion when calling the internal matching function in a \fBpcre_exec()\fP
331     execution. Further details are given with \fBpcre_exec()\fP below.
332     .sp
334 nigel 75 .sp
335 nigel 77 The output is an integer that is set to one if internal recursion when running
336     \fBpcre_exec()\fP is implemented by recursive function calls that use the stack
337     to remember their state. This is the usual way that PCRE is compiled. The
338     output is zero if PCRE was compiled to use blocks of data on the heap instead
339     of recursive function calls. In this case, \fBpcre_stack_malloc\fP and
340     \fBpcre_stack_free\fP are called to manage memory blocks on the heap, thus
341     avoiding the use of the stack.
342 nigel 75 .
343     .
345 nigel 63 .rs
346     .sp
347 nigel 75 .B pcre *pcre_compile(const char *\fIpattern\fP, int \fIoptions\fP,
348 nigel 63 .ti +5n
349 nigel 75 .B const char **\fIerrptr\fP, int *\fIerroffset\fP,
350 nigel 63 .ti +5n
351 nigel 75 .B const unsigned char *\fItableptr\fP);
352 nigel 77 .sp
353     .B pcre *pcre_compile2(const char *\fIpattern\fP, int \fIoptions\fP,
354     .ti +5n
355     .B int *\fIerrorcodeptr\fP,
356     .ti +5n
357     .B const char **\fIerrptr\fP, int *\fIerroffset\fP,
358     .ti +5n
359     .B const unsigned char *\fItableptr\fP);
360 nigel 75 .P
361 nigel 77 Either of the functions \fBpcre_compile()\fP or \fBpcre_compile2()\fP can be
362     called to compile a pattern into an internal form. The only difference between
363     the two interfaces is that \fBpcre_compile2()\fP has an additional argument,
364     \fIerrorcodeptr\fP, via which a numerical error code can be returned.
365 nigel 75 .P
366 nigel 77 The pattern is a C string terminated by a binary zero, and is passed in the
367     \fIpattern\fP argument. A pointer to a single block of memory that is obtained
368     via \fBpcre_malloc\fP is returned. This contains the compiled code and related
369     data. The \fBpcre\fP type is defined for the returned block; this is a typedef
370     for a structure whose contents are not externally defined. It is up to the
371 nigel 91 caller to free the memory (via \fBpcre_free\fP) when it is no longer required.
372 nigel 77 .P
373 nigel 63 Although the compiled code of a PCRE regex is relocatable, that is, it does not
374 nigel 75 depend on memory location, the complete \fBpcre\fP data block is not
375     fully relocatable, because it may contain a copy of the \fItableptr\fP
376     argument, which is an address (see below).
377     .P
378 nigel 93 The \fIoptions\fP argument contains various bit settings that affect the
379 nigel 75 compilation. It should be zero if no options are required. The available
380     options are described below. Some of them, in particular, those that are
381     compatible with Perl, can also be set and unset from within the pattern (see
382     the detailed description in the
383     .\" HREF
384     \fBpcrepattern\fP
385     .\"
386     documentation). For these options, the contents of the \fIoptions\fP argument
387     specifies their initial settings at the start of compilation and execution. The
388 nigel 91 PCRE_ANCHORED and PCRE_NEWLINE_\fIxxx\fP options can be set at the time of
389     matching as well as at compile time.
390 nigel 75 .P
391     If \fIerrptr\fP is NULL, \fBpcre_compile()\fP returns NULL immediately.
392     Otherwise, if compilation of a pattern fails, \fBpcre_compile()\fP returns
393     NULL, and sets the variable pointed to by \fIerrptr\fP to point to a textual
394 nigel 87 error message. This is a static string that is part of the library. You must
395     not try to free it. The offset from the start of the pattern to the character
396     where the error was discovered is placed in the variable pointed to by
397 nigel 75 \fIerroffset\fP, which must not be NULL. If it is, an immediate error is given.
398     .P
399 nigel 77 If \fBpcre_compile2()\fP is used instead of \fBpcre_compile()\fP, and the
400     \fIerrorcodeptr\fP argument is not NULL, a non-zero error code number is
401     returned via this argument in the event of an error. This is in addition to the
402     textual error message. Error codes and messages are listed below.
403     .P
404 nigel 75 If the final argument, \fItableptr\fP, is NULL, PCRE uses a default set of
405     character tables that are built when PCRE is compiled, using the default C
406     locale. Otherwise, \fItableptr\fP must be an address that is the result of a
407     call to \fBpcre_maketables()\fP. This value is stored with the compiled
408     pattern, and used again by \fBpcre_exec()\fP, unless another table pointer is
409     passed to it. For more discussion, see the section on locale support below.
410     .P
411     This code fragment shows a typical straightforward call to \fBpcre_compile()\fP:
412     .sp
413 nigel 63 pcre *re;
414     const char *error;
415     int erroffset;
416     re = pcre_compile(
417     "^A.*Z", /* the pattern */
418     0, /* default options */
419     &error, /* for error message */
420     &erroffset, /* for error offset */
421     NULL); /* use default character tables */
422 nigel 75 .sp
423     The following names for option bits are defined in the \fBpcre.h\fP header
424     file:
425     .sp
426 nigel 63 PCRE_ANCHORED
427 nigel 75 .sp
428 nigel 63 If this bit is set, the pattern is forced to be "anchored", that is, it is
429 nigel 75 constrained to match only at the first matching point in the string that is
430 nigel 63 being searched (the "subject string"). This effect can also be achieved by
431     appropriate constructs in the pattern itself, which is the only way to do it in
432     Perl.
433 nigel 75 .sp
435     .sp
436     If this bit is set, \fBpcre_compile()\fP automatically inserts callout items,
437     all with number 255, before each pattern item. For discussion of the callout
438     facility, see the
439     .\" HREF
440     \fBpcrecallout\fP
441     .\"
442     documentation.
443     .sp
444 nigel 63 PCRE_CASELESS
445 nigel 75 .sp
446 nigel 63 If this bit is set, letters in the pattern match both upper and lower case
447     letters. It is equivalent to Perl's /i option, and it can be changed within a
448 nigel 77 pattern by a (?i) option setting. In UTF-8 mode, PCRE always understands the
449     concept of case for characters whose values are less than 128, so caseless
450     matching is always possible. For characters with higher values, the concept of
451     case is supported if PCRE is compiled with Unicode property support, but not
452     otherwise. If you want to use caseless matching for characters 128 and above,
453     you must ensure that PCRE is compiled with Unicode property support as well as
454     with UTF-8 support.
455 nigel 75 .sp
457 nigel 75 .sp
458 nigel 63 If this bit is set, a dollar metacharacter in the pattern matches only at the
459     end of the subject string. Without this option, a dollar also matches
460 nigel 91 immediately before a newline at the end of the string (but not before any other
461     newlines). The PCRE_DOLLAR_ENDONLY option is ignored if PCRE_MULTILINE is set.
462     There is no equivalent to this option in Perl, and no way to set it within a
463     pattern.
464 nigel 75 .sp
465 nigel 63 PCRE_DOTALL
466 nigel 75 .sp
467 nigel 63 If this bit is set, a dot metacharater in the pattern matches all characters,
468 nigel 91 including those that indicate newline. Without it, a dot does not match when
469     the current position is at a newline. This option is equivalent to Perl's /s
470     option, and it can be changed within a pattern by a (?s) option setting. A
471 nigel 93 negative class such as [^a] always matches newline characters, independent of
472     the setting of this option.
473 nigel 75 .sp
474 nigel 91 PCRE_DUPNAMES
475     .sp
476     If this bit is set, names used to identify capturing subpatterns need not be
477     unique. This can be helpful for certain types of pattern when it is known that
478     only one instance of the named subpattern can ever be matched. There are more
479     details of named subpatterns below; see also the
480     .\" HREF
481     \fBpcrepattern\fP
482     .\"
483     documentation.
484     .sp
485 nigel 63 PCRE_EXTENDED
486 nigel 75 .sp
487 nigel 63 If this bit is set, whitespace data characters in the pattern are totally
488     ignored except when escaped or inside a character class. Whitespace does not
489     include the VT character (code 11). In addition, characters between an
490 nigel 91 unescaped # outside a character class and the next newline, inclusive, are also
491     ignored. This is equivalent to Perl's /x option, and it can be changed within a
492     pattern by a (?x) option setting.
493 nigel 75 .P
494 nigel 63 This option makes it possible to include comments inside complicated patterns.
495     Note, however, that this applies only to data characters. Whitespace characters
496     may never appear within special character sequences in a pattern, for example
497     within the sequence (?( which introduces a conditional subpattern.
498 nigel 75 .sp
499 nigel 63 PCRE_EXTRA
500 nigel 75 .sp
501 nigel 63 This option was invented in order to turn on additional functionality of PCRE
502     that is incompatible with Perl, but it is currently of very little use. When
503     set, any backslash in a pattern that is followed by a letter that has no
504     special meaning causes an error, thus reserving these combinations for future
505     expansion. By default, as in Perl, a backslash followed by a letter with no
506 nigel 91 special meaning is treated as a literal. (Perl can, however, be persuaded to
507     give a warning for this.) There are at present no other features controlled by
508     this option. It can also be set by a (?X) option setting within a pattern.
509 nigel 75 .sp
510 nigel 77 PCRE_FIRSTLINE
511     .sp
512     If this option is set, an unanchored pattern is required to match before or at
513 nigel 91 the first newline in the subject string, though the matched text may continue
514     over the newline.
515 nigel 77 .sp
516 nigel 63 PCRE_MULTILINE
517 nigel 75 .sp
518     By default, PCRE treats the subject string as consisting of a single line of
519     characters (even if it actually contains newlines). The "start of line"
520 nigel 63 metacharacter (^) matches only at the start of the string, while the "end of
521     line" metacharacter ($) matches only at the end of the string, or before a
522     terminating newline (unless PCRE_DOLLAR_ENDONLY is set). This is the same as
523     Perl.
524 nigel 75 .P
525 nigel 63 When PCRE_MULTILINE it is set, the "start of line" and "end of line" constructs
526 nigel 91 match immediately following or immediately before internal newlines in the
527     subject string, respectively, as well as at the very start and end. This is
528     equivalent to Perl's /m option, and it can be changed within a pattern by a
529     (?m) option setting. If there are no newlines in a subject string, or no
530 nigel 63 occurrences of ^ or $ in a pattern, setting PCRE_MULTILINE has no effect.
531 nigel 75 .sp
532 nigel 91 PCRE_NEWLINE_CR
535 nigel 93 PCRE_NEWLINE_ANY
536 nigel 91 .sp
537     These options override the default newline definition that was chosen when PCRE
538     was built. Setting the first or the second specifies that a newline is
539 nigel 93 indicated by a single character (CR or LF, respectively). Setting
540     PCRE_NEWLINE_CRLF specifies that a newline is indicated by the two-character
541     CRLF sequence. Setting PCRE_NEWLINE_ANY specifies that any Unicode newline
542     sequence should be recognized. The Unicode newline sequences are the three just
543     mentioned, plus the single characters VT (vertical tab, U+000B), FF (formfeed,
544     U+000C), NEL (next line, U+0085), LS (line separator, U+2028), and PS
545     (paragraph separator, U+2029). The last two are recognized only in UTF-8 mode.
546 nigel 91 .P
547 nigel 93 The newline setting in the options word uses three bits that are treated
548     as a number, giving eight possibilities. Currently only five are used (default
549     plus the four values above). This means that if you set more than one newline
550     option, the combination may or may not be sensible. For example,
551     PCRE_NEWLINE_CR with PCRE_NEWLINE_LF is equivalent to PCRE_NEWLINE_CRLF, but
552     other combinations yield unused numbers and cause an error.
553     .P
554     The only time that a line break is specially recognized when compiling a
555     pattern is if PCRE_EXTENDED is set, and an unescaped # outside a character
556     class is encountered. This indicates a comment that lasts until after the next
557     line break sequence. In other circumstances, line break sequences are treated
558     as literal data, except that in PCRE_EXTENDED mode, both CR and LF are treated
559     as whitespace characters and are therefore ignored.
560     .P
561     The newline option that is set at compile time becomes the default that is used
562     for \fBpcre_exec()\fP and \fBpcre_dfa_exec()\fP, but it can be overridden.
563 nigel 91 .sp
565 nigel 75 .sp
566 nigel 63 If this option is set, it disables the use of numbered capturing parentheses in
567     the pattern. Any opening parenthesis that is not followed by ? behaves as if it
568     were followed by ?: but named parentheses can still be used for capturing (and
569     they acquire numbers in the usual way). There is no equivalent of this option
570     in Perl.
571 nigel 75 .sp
572 nigel 63 PCRE_UNGREEDY
573 nigel 75 .sp
574 nigel 63 This option inverts the "greediness" of the quantifiers so that they are not
575     greedy by default, but become greedy if followed by "?". It is not compatible
576     with Perl. It can also be set by a (?U) option setting within the pattern.
577 nigel 75 .sp
578 nigel 63 PCRE_UTF8
579 nigel 75 .sp
580 nigel 63 This option causes PCRE to regard both the pattern and the subject as strings
581     of UTF-8 characters instead of single-byte character strings. However, it is
582 nigel 75 available only when PCRE is built to include UTF-8 support. If not, the use
583 nigel 63 of this option provokes an error. Details of how this option changes the
584     behaviour of PCRE are given in the
585     .\" HTML <a href="pcre.html#utf8support">
586     .\" </a>
587     section on UTF-8 support
588     .\"
589     in the main
590     .\" HREF
591 nigel 75 \fBpcre\fP
592 nigel 63 .\"
593     page.
594 nigel 75 .sp
595 nigel 71 PCRE_NO_UTF8_CHECK
596 nigel 75 .sp
597 nigel 71 When PCRE_UTF8 is set, the validity of the pattern as a UTF-8 string is
598     automatically checked. If an invalid UTF-8 sequence of bytes is found,
599 nigel 75 \fBpcre_compile()\fP returns an error. If you already know that your pattern is
600 nigel 71 valid, and you want to skip this check for performance reasons, you can set the
601     PCRE_NO_UTF8_CHECK option. When it is set, the effect of passing an invalid
602     UTF-8 string as a pattern is undefined. It may cause your program to crash.
603 nigel 77 Note that this option can also be passed to \fBpcre_exec()\fP and
604     \fBpcre_dfa_exec()\fP, to suppress the UTF-8 validity checking of subject
605     strings.
606 nigel 75 .
607     .
609     .rs
610     .sp
611     The following table lists the error codes than may be returned by
612     \fBpcre_compile2()\fP, along with the error messages that may be returned by
613 nigel 93 both compiling functions. As PCRE has developed, some error codes have fallen
614     out of use. To avoid confusion, they have not been re-used.
615 nigel 77 .sp
616     0 no error
617     1 \e at end of pattern
618     2 \ec at end of pattern
619     3 unrecognized character follows \e
620     4 numbers out of order in {} quantifier
621     5 number too big in {} quantifier
622     6 missing terminating ] for character class
623     7 invalid escape sequence in character class
624     8 range out of order in character class
625     9 nothing to repeat
626 nigel 93 10 [this code is not in use]
627 nigel 77 11 internal error: unexpected repeat
628     12 unrecognized character after (?
629     13 POSIX named classes are supported only within a class
630     14 missing )
631     15 reference to non-existent subpattern
632     16 erroffset passed as NULL
633     17 unknown option bit(s) set
634     18 missing ) after comment
635 nigel 93 19 [this code is not in use]
636 nigel 77 20 regular expression too large
637     21 failed to get memory
638     22 unmatched parentheses
639     23 internal error: code overflow
640     24 unrecognized character after (?<
641     25 lookbehind assertion is not fixed length
642 nigel 91 26 malformed number or name after (?(
643 nigel 77 27 conditional group contains more than two branches
644     28 assertion expected after (?(
645     29 (?R or (?digits must be followed by )
646     30 unknown POSIX class name
647     31 POSIX collating elements are not supported
648     32 this version of PCRE is not compiled with PCRE_UTF8 support
649 nigel 93 33 [this code is not in use]
650 nigel 77 34 character value in \ex{...} sequence is too large
651     35 invalid condition (?(0)
652     36 \eC not allowed in lookbehind assertion
653     37 PCRE does not support \eL, \el, \eN, \eU, or \eu
654     38 number after (?C is > 255
655     39 closing ) for (?C expected
656     40 recursive call could loop indefinitely
657     41 unrecognized character after (?P
658 nigel 93 42 syntax error in subpattern name (missing terminator)
659 nigel 91 43 two named subpatterns have the same name
660 nigel 77 44 invalid UTF-8 string
661     45 support for \eP, \ep, and \eX has not been compiled
662     46 malformed \eP or \ep sequence
663     47 unknown property name after \eP or \ep
664 nigel 91 48 subpattern name is too long (maximum 32 characters)
665     49 too many named subpatterns (maximum 10,000)
666     50 repeated subpattern is too long
667     51 octal value is greater than \e377 (not in UTF-8 mode)
668 nigel 93 52 internal error: overran compiling workspace
669     53 internal error: previously-checked referenced subpattern not found
670     54 DEFINE group contains more than one branch
671     55 repeating a DEFINE group is not allowed
672     56 inconsistent NEWLINE options"
673 nigel 77 .
674     .
675 nigel 75 .SH "STUDYING A PATTERN"
676 nigel 63 .rs
677     .sp
678 nigel 77 .B pcre_extra *pcre_study(const pcre *\fIcode\fP, int \fIoptions\fP
679 nigel 63 .ti +5n
680 nigel 75 .B const char **\fIerrptr\fP);
681 nigel 63 .PP
682 nigel 75 If a compiled pattern is going to be used several times, it is worth spending
683     more time analyzing it in order to speed up the time taken for matching. The
684     function \fBpcre_study()\fP takes a pointer to a compiled pattern as its first
685     argument. If studying the pattern produces additional information that will
686     help speed up matching, \fBpcre_study()\fP returns a pointer to a
687     \fBpcre_extra\fP block, in which the \fIstudy_data\fP field points to the
688     results of the study.
689     .P
690     The returned value from \fBpcre_study()\fP can be passed directly to
691     \fBpcre_exec()\fP. However, a \fBpcre_extra\fP block also contains other
692 nigel 63 fields that can be set by the caller before the block is passed; these are
693 nigel 75 described
694     .\" HTML <a href="#extradata">
695     .\" </a>
696     below
697     .\"
698     in the section on matching a pattern.
699     .P
700 nigel 77 If studying the pattern does not produce any additional information
701 nigel 75 \fBpcre_study()\fP returns NULL. In that circumstance, if the calling program
702     wants to pass any of the other fields to \fBpcre_exec()\fP, it must set up its
703     own \fBpcre_extra\fP block.
704     .P
705     The second argument of \fBpcre_study()\fP contains option bits. At present, no
706     options are defined, and this argument should always be zero.
707     .P
708     The third argument for \fBpcre_study()\fP is a pointer for an error message. If
709 nigel 63 studying succeeds (even if no data is returned), the variable it points to is
710 nigel 87 set to NULL. Otherwise it is set to point to a textual error message. This is a
711     static string that is part of the library. You must not try to free it. You
712     should test the error pointer for NULL after calling \fBpcre_study()\fP, to be
713     sure that it has run successfully.
714 nigel 75 .P
715     This is a typical call to \fBpcre_study\fP():
716     .sp
717 nigel 63 pcre_extra *pe;
718     pe = pcre_study(
719     re, /* result of pcre_compile() */
720     0, /* no options exist */
721     &error); /* set to NULL or points to a message */
722 nigel 75 .sp
723 nigel 63 At present, studying a pattern is useful only for non-anchored patterns that do
724     not have a single fixed starting character. A bitmap of possible starting
725 nigel 75 bytes is created.
726     .
727     .
728 nigel 63 .\" HTML <a name="localesupport"></a>
729 nigel 75 .SH "LOCALE SUPPORT"
730 nigel 63 .rs
731     .sp
732 nigel 77 PCRE handles caseless matching, and determines whether characters are letters
733 nigel 75 digits, or whatever, by reference to a set of tables, indexed by character
734 nigel 77 value. When running in UTF-8 mode, this applies only to characters with codes
735 nigel 75 less than 128. Higher-valued codes never match escapes such as \ew or \ed, but
736     can be tested with \ep if PCRE is built with Unicode character property
737 nigel 87 support. The use of locales with Unicode is discouraged.
738 nigel 75 .P
739     An internal set of tables is created in the default C locale when PCRE is
740     built. This is used when the final argument of \fBpcre_compile()\fP is NULL,
741     and is sufficient for many applications. An alternative set of tables can,
742     however, be supplied. These may be created in a different locale from the
743     default. As more and more applications change to using Unicode, the need for
744     this locale support is expected to die away.
745     .P
746     External tables are built by calling the \fBpcre_maketables()\fP function,
747     which has no arguments, in the relevant locale. The result can then be passed
748     to \fBpcre_compile()\fP or \fBpcre_exec()\fP as often as necessary. For
749     example, to build and use tables that are appropriate for the French locale
750     (where accented characters with values greater than 128 are treated as letters),
751     the following code could be used:
752     .sp
753     setlocale(LC_CTYPE, "fr_FR");
754 nigel 63 tables = pcre_maketables();
755     re = pcre_compile(..., tables);
756 nigel 75 .sp
757     When \fBpcre_maketables()\fP runs, the tables are built in memory that is
758     obtained via \fBpcre_malloc\fP. It is the caller's responsibility to ensure
759     that the memory containing the tables remains available for as long as it is
760     needed.
761     .P
762     The pointer that is passed to \fBpcre_compile()\fP is saved with the compiled
763     pattern, and the same tables are used via this pointer by \fBpcre_study()\fP
764     and normally also by \fBpcre_exec()\fP. Thus, by default, for any single
765     pattern, compilation, studying and matching all happen in the same locale, but
766     different patterns can be compiled in different locales.
767     .P
768     It is possible to pass a table pointer or NULL (indicating the use of the
769     internal tables) to \fBpcre_exec()\fP. Although not intended for this purpose,
770     this facility could be used to match a pattern in a different locale from the
771     one in which it was compiled. Passing table pointers at run time is discussed
772     below in the section on matching a pattern.
773     .
774     .
776 nigel 63 .rs
777     .sp
778 nigel 75 .B int pcre_fullinfo(const pcre *\fIcode\fP, "const pcre_extra *\fIextra\fP,"
779 nigel 63 .ti +5n
780 nigel 75 .B int \fIwhat\fP, void *\fIwhere\fP);
781 nigel 63 .PP
782 nigel 75 The \fBpcre_fullinfo()\fP function returns information about a compiled
783     pattern. It replaces the obsolete \fBpcre_info()\fP function, which is
784 nigel 63 nevertheless retained for backwards compability (and is documented below).
785 nigel 75 .P
786     The first argument for \fBpcre_fullinfo()\fP is a pointer to the compiled
787     pattern. The second argument is the result of \fBpcre_study()\fP, or NULL if
788 nigel 63 the pattern was not studied. The third argument specifies which piece of
789     information is required, and the fourth argument is a pointer to a variable
790     to receive the data. The yield of the function is zero for success, or one of
791     the following negative numbers:
792 nigel 75 .sp
793     PCRE_ERROR_NULL the argument \fIcode\fP was NULL
794     the argument \fIwhere\fP was NULL
795 nigel 63 PCRE_ERROR_BADMAGIC the "magic number" was not found
796 nigel 75 PCRE_ERROR_BADOPTION the value of \fIwhat\fP was invalid
797     .sp
798     The "magic number" is placed at the start of each compiled pattern as an simple
799     check against passing an arbitrary memory pointer. Here is a typical call of
800     \fBpcre_fullinfo()\fP, to obtain the length of the compiled pattern:
801     .sp
802 nigel 63 int rc;
803 nigel 91 size_t length;
804 nigel 63 rc = pcre_fullinfo(
805     re, /* result of pcre_compile() */
806     pe, /* result of pcre_study(), or NULL */
807     PCRE_INFO_SIZE, /* what is required */
808     &length); /* where to put the data */
809 nigel 75 .sp
810     The possible values for the third argument are defined in \fBpcre.h\fP, and are
811 nigel 63 as follows:
812 nigel 75 .sp
814 nigel 75 .sp
815 nigel 63 Return the number of the highest back reference in the pattern. The fourth
816 nigel 75 argument should point to an \fBint\fP variable. Zero is returned if there are
817 nigel 63 no back references.
818 nigel 75 .sp
820 nigel 75 .sp
821 nigel 63 Return the number of capturing subpatterns in the pattern. The fourth argument
822 nigel 75 should point to an \fBint\fP variable.
823     .sp
825 nigel 75 .sp
826     Return a pointer to the internal default character tables within PCRE. The
827     fourth argument should point to an \fBunsigned char *\fP variable. This
828     information call is provided for internal use by the \fBpcre_study()\fP
829     function. External callers can cause PCRE to use its internal tables by passing
830     a NULL table pointer.
831     .sp
833 nigel 75 .sp
834 nigel 63 Return information about the first byte of any matched string, for a
835 nigel 91 non-anchored pattern. The fourth argument should point to an \fBint\fP
836     variable. (This option used to be called PCRE_INFO_FIRSTCHAR; the old name is
837     still recognized for backwards compatibility.)
838 nigel 75 .P
839     If there is a fixed first byte, for example, from a pattern such as
840 nigel 93 (cat|cow|coyote), its value is returned. Otherwise, if either
841 nigel 75 .sp
842 nigel 63 (a) the pattern was compiled with the PCRE_MULTILINE option, and every branch
843     starts with "^", or
844 nigel 75 .sp
845 nigel 63 (b) every branch of the pattern starts with ".*" and PCRE_DOTALL is not set
846     (if it were set, the pattern would be anchored),
847 nigel 75 .sp
848 nigel 63 -1 is returned, indicating that the pattern matches only at the start of a
849     subject string or after any newline within the string. Otherwise -2 is
850     returned. For anchored patterns, -2 is returned.
851 nigel 75 .sp
853 nigel 75 .sp
854 nigel 63 If the pattern was studied, and this resulted in the construction of a 256-bit
855     table indicating a fixed set of bytes for the first byte in any matching
856     string, a pointer to the table is returned. Otherwise NULL is returned. The
857 nigel 75 fourth argument should point to an \fBunsigned char *\fP variable.
858     .sp
860 nigel 75 .sp
861 nigel 65 Return the value of the rightmost literal byte that must exist in any matched
862     string, other than at its start, if such a byte has been recorded. The fourth
863 nigel 75 argument should point to an \fBint\fP variable. If there is no such byte, -1 is
864 nigel 65 returned. For anchored patterns, a last literal byte is recorded only if it
865     follows something of variable length. For example, for the pattern
866 nigel 75 /^a\ed+z\ed+/ the returned value is "z", but for /^a\edz\ed/ the returned value
867 nigel 65 is -1.
868 nigel 75 .sp
872 nigel 75 .sp
873 nigel 63 PCRE supports the use of named as well as numbered capturing parentheses. The
874     names are just an additional way of identifying the parentheses, which still
875 nigel 91 acquire numbers. Several convenience functions such as
876     \fBpcre_get_named_substring()\fP are provided for extracting captured
877     substrings by name. It is also possible to extract the data directly, by first
878     converting the name to a number in order to access the correct pointers in the
879     output vector (described with \fBpcre_exec()\fP below). To do the conversion,
880     you need to use the name-to-number map, which is described by these three
881     values.
882 nigel 75 .P
883 nigel 63 The map consists of a number of fixed-size entries. PCRE_INFO_NAMECOUNT gives
884     the number of entries, and PCRE_INFO_NAMEENTRYSIZE gives the size of each
885 nigel 75 entry; both of these return an \fBint\fP value. The entry size depends on the
886 nigel 63 length of the longest name. PCRE_INFO_NAMETABLE returns a pointer to the first
887 nigel 75 entry of the table (a pointer to \fBchar\fP). The first two bytes of each entry
888 nigel 63 are the number of the capturing parenthesis, most significant byte first. The
889     rest of the entry is the corresponding name, zero terminated. The names are in
890 nigel 91 alphabetical order. When PCRE_DUPNAMES is set, duplicate names are in order of
891     their parentheses numbers. For example, consider the following pattern (assume
892 nigel 63 PCRE_EXTENDED is set, so white space - including newlines - is ignored):
893 nigel 75 .sp
894     .\" JOIN
895 nigel 93 (?<date> (?<year>(\ed\ed)?\ed\ed) -
896     (?<month>\ed\ed) - (?<day>\ed\ed) )
897 nigel 75 .sp
898 nigel 63 There are four named subpatterns, so the table has four entries, and each entry
899     in the table is eight bytes long. The table is as follows, with non-printing
900 nigel 75 bytes shows in hexadecimal, and undefined bytes shown as ??:
901     .sp
902 nigel 63 00 01 d a t e 00 ??
903     00 05 d a y 00 ?? ??
904     00 04 m o n t h 00
905     00 02 y e a r 00 ??
906 nigel 75 .sp
907     When writing code to extract data from named subpatterns using the
908 nigel 91 name-to-number map, remember that the length of the entries is likely to be
909 nigel 75 different for each compiled pattern.
910     .sp
911 nigel 63 PCRE_INFO_OPTIONS
912 nigel 75 .sp
913 nigel 63 Return a copy of the options with which the pattern was compiled. The fourth
914 nigel 75 argument should point to an \fBunsigned long int\fP variable. These option bits
915     are those specified in the call to \fBpcre_compile()\fP, modified by any
916 nigel 63 top-level option settings within the pattern itself.
917 nigel 75 .P
918 nigel 63 A pattern is automatically anchored by PCRE if all of its top-level
919     alternatives begin with one of the following:
920 nigel 75 .sp
921 nigel 63 ^ unless PCRE_MULTILINE is set
922 nigel 75 \eA always
923     \eG always
924     .\" JOIN
925 nigel 63 .* if PCRE_DOTALL is set and there are no back
926     references to the subpattern in which .* appears
927 nigel 75 .sp
928 nigel 63 For such patterns, the PCRE_ANCHORED bit is set in the options returned by
929 nigel 75 \fBpcre_fullinfo()\fP.
930     .sp
931 nigel 63 PCRE_INFO_SIZE
932 nigel 75 .sp
933 nigel 63 Return the size of the compiled pattern, that is, the value that was passed as
934 nigel 75 the argument to \fBpcre_malloc()\fP when PCRE was getting memory in which to
935     place the compiled data. The fourth argument should point to a \fBsize_t\fP
936 nigel 63 variable.
937 nigel 75 .sp
939 nigel 75 .sp
940     Return the size of the data block pointed to by the \fIstudy_data\fP field in
941     a \fBpcre_extra\fP block. That is, it is the value that was passed to
942     \fBpcre_malloc()\fP when PCRE was getting memory into which to place the data
943     created by \fBpcre_study()\fP. The fourth argument should point to a
944     \fBsize_t\fP variable.
945     .
946     .
948 nigel 63 .rs
949     .sp
950 nigel 75 .B int pcre_info(const pcre *\fIcode\fP, int *\fIoptptr\fP, int
951     .B *\fIfirstcharptr\fP);
952 nigel 63 .PP
953 nigel 75 The \fBpcre_info()\fP function is now obsolete because its interface is too
954 nigel 63 restrictive to return all the available data about a compiled pattern. New
955 nigel 75 programs should use \fBpcre_fullinfo()\fP instead. The yield of
956     \fBpcre_info()\fP is the number of capturing subpatterns, or one of the
957 nigel 63 following negative numbers:
958 nigel 75 .sp
959     PCRE_ERROR_NULL the argument \fIcode\fP was NULL
960 nigel 63 PCRE_ERROR_BADMAGIC the "magic number" was not found
961 nigel 75 .sp
962     If the \fIoptptr\fP argument is not NULL, a copy of the options with which the
963 nigel 63 pattern was compiled is placed in the integer it points to (see
964     PCRE_INFO_OPTIONS above).
965 nigel 75 .P
966     If the pattern is not anchored and the \fIfirstcharptr\fP argument is not NULL,
967 nigel 63 it is used to pass back information about the first character of any matched
968     string (see PCRE_INFO_FIRSTBYTE above).
969 nigel 75 .
970     .
971 nigel 77 .SH "REFERENCE COUNTS"
972 nigel 63 .rs
973     .sp
974 nigel 77 .B int pcre_refcount(pcre *\fIcode\fP, int \fIadjust\fP);
975     .PP
976     The \fBpcre_refcount()\fP function is used to maintain a reference count in the
977     data block that contains a compiled pattern. It is provided for the benefit of
978     applications that operate in an object-oriented manner, where different parts
979     of the application may be using the same compiled pattern, but you want to free
980     the block when they are all done.
981     .P
982     When a pattern is compiled, the reference count field is initialized to zero.
983     It is changed only by calling this function, whose action is to add the
984     \fIadjust\fP value (which may be positive or negative) to it. The yield of the
985     function is the new value. However, the value of the count is constrained to
986     lie between 0 and 65535, inclusive. If the new value is outside these limits,
987     it is forced to the appropriate limit value.
988     .P
989     Except when it is zero, the reference count is not correctly preserved if a
990     pattern is compiled on one host and then transferred to a host whose byte-order
991     is different. (This seems a highly unlikely scenario.)
992     .
993     .
995     .rs
996     .sp
997 nigel 75 .B int pcre_exec(const pcre *\fIcode\fP, "const pcre_extra *\fIextra\fP,"
998 nigel 63 .ti +5n
999 nigel 75 .B "const char *\fIsubject\fP," int \fIlength\fP, int \fIstartoffset\fP,
1000 nigel 63 .ti +5n
1001 nigel 75 .B int \fIoptions\fP, int *\fIovector\fP, int \fIovecsize\fP);
1002     .P
1003     The function \fBpcre_exec()\fP is called to match a subject string against a
1004     compiled pattern, which is passed in the \fIcode\fP argument. If the
1005 nigel 63 pattern has been studied, the result of the study should be passed in the
1006 nigel 77 \fIextra\fP argument. This function is the main matching facility of the
1007     library, and it operates in a Perl-like manner. For specialist use there is
1008     also an alternative matching function, which is described
1009     .\" HTML <a href="#dfamatch">
1010     .\" </a>
1011     below
1012     .\"
1013     in the section about the \fBpcre_dfa_exec()\fP function.
1014 nigel 75 .P
1015     In most applications, the pattern will have been compiled (and optionally
1016     studied) in the same process that calls \fBpcre_exec()\fP. However, it is
1017     possible to save compiled patterns and study data, and then use them later
1018     in different processes, possibly even on different hosts. For a discussion
1019     about this, see the
1020     .\" HREF
1021     \fBpcreprecompile\fP
1022     .\"
1023     documentation.
1024     .P
1025     Here is an example of a simple call to \fBpcre_exec()\fP:
1026     .sp
1027 nigel 63 int rc;
1028     int ovector[30];
1029     rc = pcre_exec(
1030     re, /* result of pcre_compile() */
1031     NULL, /* we didn't study the pattern */
1032     "some string", /* the subject string */
1033     11, /* the length of the subject string */
1034     0, /* start at offset 0 in the subject */
1035     0, /* default options */
1036 nigel 75 ovector, /* vector of integers for substring information */
1037 nigel 77 30); /* number of elements (NOT size in bytes) */
1038 nigel 75 .
1039     .\" HTML <a name="extradata"></a>
1040     .SS "Extra data for \fBpcre_exec()\fR"
1041     .rs
1042     .sp
1043     If the \fIextra\fP argument is not NULL, it must point to a \fBpcre_extra\fP
1044     data block. The \fBpcre_study()\fP function returns such a block (when it
1045 nigel 63 doesn't return NULL), but you can also create one for yourself, and pass
1046 nigel 87 additional information in it. The \fBpcre_extra\fP block contains the following
1047     fields (not necessarily in this order):
1048 nigel 75 .sp
1049     unsigned long int \fIflags\fP;
1050     void *\fIstudy_data\fP;
1051     unsigned long int \fImatch_limit\fP;
1052 nigel 87 unsigned long int \fImatch_limit_recursion\fP;
1053 nigel 75 void *\fIcallout_data\fP;
1054     const unsigned char *\fItables\fP;
1055     .sp
1056     The \fIflags\fP field is a bitmap that specifies which of the other fields
1057 nigel 63 are set. The flag bits are:
1058 nigel 75 .sp
1063 nigel 75 PCRE_EXTRA_TABLES
1064     .sp
1065     Other flag bits should be set to zero. The \fIstudy_data\fP field is set in the
1066     \fBpcre_extra\fP block that is returned by \fBpcre_study()\fP, together with
1067     the appropriate flag bit. You should not set this yourself, but you may add to
1068     the block by setting the other fields and their corresponding flag bits.
1069     .P
1070     The \fImatch_limit\fP field provides a means of preventing PCRE from using up a
1071 nigel 63 vast amount of resources when running patterns that are not going to match,
1072     but which have a very large number of possibilities in their search trees. The
1073 nigel 75 classic example is the use of nested unlimited repeats.
1074     .P
1075     Internally, PCRE uses a function called \fBmatch()\fP which it calls repeatedly
1076 nigel 87 (sometimes recursively). The limit set by \fImatch_limit\fP is imposed on the
1077     number of times this function is called during a match, which has the effect of
1078     limiting the amount of backtracking that can take place. For patterns that are
1079     not anchored, the count restarts from zero for each position in the subject
1080     string.
1081 nigel 75 .P
1082 nigel 87 The default value for the limit can be set when PCRE is built; the default
1083 nigel 63 default is 10 million, which handles all but the most extreme cases. You can
1084 nigel 87 override the default by suppling \fBpcre_exec()\fP with a \fBpcre_extra\fP
1085     block in which \fImatch_limit\fP is set, and PCRE_EXTRA_MATCH_LIMIT is set in
1086     the \fIflags\fP field. If the limit is exceeded, \fBpcre_exec()\fP returns
1088 nigel 75 .P
1089 nigel 87 The \fImatch_limit_recursion\fP field is similar to \fImatch_limit\fP, but
1090     instead of limiting the total number of times that \fBmatch()\fP is called, it
1091     limits the depth of recursion. The recursion depth is a smaller number than the
1092     total number of calls, because not all calls to \fBmatch()\fP are recursive.
1093     This limit is of use only if it is set smaller than \fImatch_limit\fP.
1094     .P
1095     Limiting the recursion depth limits the amount of stack that can be used, or,
1096     when PCRE has been compiled to use memory on the heap instead of the stack, the
1097     amount of heap memory that can be used.
1098     .P
1099     The default value for \fImatch_limit_recursion\fP can be set when PCRE is
1100     built; the default default is the same value as the default for
1101     \fImatch_limit\fP. You can override the default by suppling \fBpcre_exec()\fP
1102     with a \fBpcre_extra\fP block in which \fImatch_limit_recursion\fP is set, and
1103     PCRE_EXTRA_MATCH_LIMIT_RECURSION is set in the \fIflags\fP field. If the limit
1104     is exceeded, \fBpcre_exec()\fP returns PCRE_ERROR_RECURSIONLIMIT.
1105     .P
1106 nigel 75 The \fIpcre_callout\fP field is used in conjunction with the "callout" feature,
1107     which is described in the
1108     .\" HREF
1109     \fBpcrecallout\fP
1110     .\"
1111     documentation.
1112     .P
1113     The \fItables\fP field is used to pass a character tables pointer to
1114     \fBpcre_exec()\fP; this overrides the value that is stored with the compiled
1115     pattern. A non-NULL value is stored with the compiled pattern only if custom
1116     tables were supplied to \fBpcre_compile()\fP via its \fItableptr\fP argument.
1117     If NULL is passed to \fBpcre_exec()\fP using this mechanism, it forces PCRE's
1118     internal tables to be used. This facility is helpful when re-using patterns
1119     that have been saved after compiling with an external set of tables, because
1120     the external tables might be at a different address when \fBpcre_exec()\fP is
1121     called. See the
1122     .\" HREF
1123     \fBpcreprecompile\fP
1124     .\"
1125     documentation for a discussion of saving compiled patterns for later use.
1126     .
1127     .SS "Option bits for \fBpcre_exec()\fP"
1128     .rs
1129     .sp
1130     The unused bits of the \fIoptions\fP argument for \fBpcre_exec()\fP must be
1131 nigel 91 zero. The only bits that may be set are PCRE_ANCHORED, PCRE_NEWLINE_\fIxxx\fP,
1133 nigel 75 .sp
1135     .sp
1136     The PCRE_ANCHORED option limits \fBpcre_exec()\fP to matching at the first
1137     matching position. If a pattern was compiled with PCRE_ANCHORED, or turned out
1138     to be anchored by virtue of its contents, it cannot be made unachored at
1139     matching time.
1140     .sp
1141 nigel 91 PCRE_NEWLINE_CR
1144 nigel 93 PCRE_NEWLINE_ANY
1145 nigel 91 .sp
1146     These options override the newline definition that was chosen or defaulted when
1147 nigel 93 the pattern was compiled. For details, see the description of
1148     \fBpcre_compile()\fP above. During matching, the newline choice affects the
1149     behaviour of the dot, circumflex, and dollar metacharacters. It may also alter
1150     the way the match position is advanced after a match failure for an unanchored
1151     pattern. When PCRE_NEWLINE_CRLF or PCRE_NEWLINE_ANY is set, and a match attempt
1152     fails when the current position is at a CRLF sequence, the match position is
1153     advanced by two characters instead of one, in other words, to after the CRLF.
1154 nigel 91 .sp
1155 nigel 63 PCRE_NOTBOL
1156 nigel 75 .sp
1157     This option specifies that first character of the subject string is not the
1158     beginning of a line, so the circumflex metacharacter should not match before
1159     it. Setting this without PCRE_MULTILINE (at compile time) causes circumflex
1160     never to match. This option affects only the behaviour of the circumflex
1161     metacharacter. It does not affect \eA.
1162     .sp
1163 nigel 63 PCRE_NOTEOL
1164 nigel 75 .sp
1165     This option specifies that the end of the subject string is not the end of a
1166     line, so the dollar metacharacter should not match it nor (except in multiline
1167     mode) a newline immediately before it. Setting this without PCRE_MULTILINE (at
1168     compile time) causes dollar never to match. This option affects only the
1169     behaviour of the dollar metacharacter. It does not affect \eZ or \ez.
1170     .sp
1171 nigel 63 PCRE_NOTEMPTY
1172 nigel 75 .sp
1173 nigel 63 An empty string is not considered to be a valid match if this option is set. If
1174     there are alternatives in the pattern, they are tried. If all the alternatives
1175     match the empty string, the entire match fails. For example, if the pattern
1176 nigel 75 .sp
1177 nigel 63 a?b?
1178 nigel 75 .sp
1179 nigel 63 is applied to a string not beginning with "a" or "b", it matches the empty
1180     string at the start of the subject. With PCRE_NOTEMPTY set, this match is not
1181     valid, so PCRE searches further into the string for occurrences of "a" or "b".
1182 nigel 75 .P
1183 nigel 63 Perl has no direct equivalent of PCRE_NOTEMPTY, but it does make a special case
1184 nigel 75 of a pattern match of the empty string within its \fBsplit()\fP function, and
1185 nigel 63 when using the /g modifier. It is possible to emulate Perl's behaviour after
1186     matching a null string by first trying the match again at the same offset with
1187 nigel 75 PCRE_NOTEMPTY and PCRE_ANCHORED, and then if that fails by advancing the
1188     starting offset (see below) and trying an ordinary match again. There is some
1189     code that demonstrates how to do this in the \fIpcredemo.c\fP sample program.
1190     .sp
1192     .sp
1193     When PCRE_UTF8 is set at compile time, the validity of the subject as a UTF-8
1194     string is automatically checked when \fBpcre_exec()\fP is subsequently called.
1195     The value of \fIstartoffset\fP is also checked to ensure that it points to the
1196     start of a UTF-8 character. If an invalid UTF-8 sequence of bytes is found,
1197     \fBpcre_exec()\fP returns the error PCRE_ERROR_BADUTF8. If \fIstartoffset\fP
1198     contains an invalid value, PCRE_ERROR_BADUTF8_OFFSET is returned.
1199     .P
1200     If you already know that your subject is valid, and you want to skip these
1201     checks for performance reasons, you can set the PCRE_NO_UTF8_CHECK option when
1202     calling \fBpcre_exec()\fP. You might want to do this for the second and
1203     subsequent calls to \fBpcre_exec()\fP if you are making repeated calls to find
1204     all the matches in a single subject string. However, you should be sure that
1205     the value of \fIstartoffset\fP points to the start of a UTF-8 character. When
1206     PCRE_NO_UTF8_CHECK is set, the effect of passing an invalid UTF-8 string as a
1207     subject, or a value of \fIstartoffset\fP that does not point to the start of a
1208     UTF-8 character, is undefined. Your program may crash.
1209     .sp
1211     .sp
1212     This option turns on the partial matching feature. If the subject string fails
1213     to match the pattern, but at some point during the matching process the end of
1214     the subject was reached (that is, the subject partially matches the pattern and
1215     the failure to match occurred only because there were not enough subject
1216     characters), \fBpcre_exec()\fP returns PCRE_ERROR_PARTIAL instead of
1217     PCRE_ERROR_NOMATCH. When PCRE_PARTIAL is used, there are restrictions on what
1218     may appear in the pattern. These are discussed in the
1219     .\" HREF
1220     \fBpcrepartial\fP
1221     .\"
1222     documentation.
1223     .
1224     .SS "The string to be matched by \fBpcre_exec()\fP"
1225     .rs
1226     .sp
1227     The subject string is passed to \fBpcre_exec()\fP as a pointer in
1228     \fIsubject\fP, a length in \fIlength\fP, and a starting byte offset in
1229     \fIstartoffset\fP. In UTF-8 mode, the byte offset must point to the start of a
1230     UTF-8 character. Unlike the pattern string, the subject may contain binary zero
1231     bytes. When the starting offset is zero, the search for a match starts at the
1232     beginning of the subject, and this is by far the most common case.
1233     .P
1234 nigel 63 A non-zero starting offset is useful when searching for another match in the
1235 nigel 75 same subject by calling \fBpcre_exec()\fP again after a previous success.
1236     Setting \fIstartoffset\fP differs from just passing over a shortened string and
1237 nigel 63 setting PCRE_NOTBOL in the case of a pattern that begins with any kind of
1238     lookbehind. For example, consider the pattern
1239 nigel 75 .sp
1240     \eBiss\eB
1241     .sp
1242     which finds occurrences of "iss" in the middle of words. (\eB matches only if
1243 nigel 63 the current position in the subject is not a word boundary.) When applied to
1244 nigel 75 the string "Mississipi" the first call to \fBpcre_exec()\fP finds the first
1245     occurrence. If \fBpcre_exec()\fP is called again with just the remainder of the
1246     subject, namely "issipi", it does not match, because \eB is always false at the
1247 nigel 63 start of the subject, which is deemed to be a word boundary. However, if
1248 nigel 75 \fBpcre_exec()\fP is passed the entire string again, but with \fIstartoffset\fP
1249 nigel 63 set to 4, it finds the second occurrence of "iss" because it is able to look
1250     behind the starting point to discover that it is preceded by a letter.
1251 nigel 75 .P
1252 nigel 63 If a non-zero starting offset is passed when the pattern is anchored, one
1253 nigel 75 attempt to match at the given offset is made. This can only succeed if the
1254 nigel 63 pattern does not require the match to be at the start of the subject.
1255 nigel 75 .
1256     .SS "How \fBpcre_exec()\fP returns captured substrings"
1257     .rs
1258     .sp
1259 nigel 63 In general, a pattern matches a certain portion of the subject, and in
1260     addition, further substrings from the subject may be picked out by parts of the
1261     pattern. Following the usage in Jeffrey Friedl's book, this is called
1262     "capturing" in what follows, and the phrase "capturing subpattern" is used for
1263     a fragment of a pattern that picks out a substring. PCRE supports several other
1264     kinds of parenthesized subpattern that do not cause substrings to be captured.
1265 nigel 75 .P
1266 nigel 63 Captured substrings are returned to the caller via a vector of integer offsets
1267 nigel 75 whose address is passed in \fIovector\fP. The number of elements in the vector
1268     is passed in \fIovecsize\fP, which must be a non-negative number. \fBNote\fP:
1269     this argument is NOT the size of \fIovector\fP in bytes.
1270     .P
1271     The first two-thirds of the vector is used to pass back captured substrings,
1272     each substring using a pair of integers. The remaining third of the vector is
1273     used as workspace by \fBpcre_exec()\fP while matching capturing subpatterns,
1274     and is not available for passing back information. The length passed in
1275     \fIovecsize\fP should always be a multiple of three. If it is not, it is
1276     rounded down.
1277     .P
1278     When a match is successful, information about captured substrings is returned
1279     in pairs of integers, starting at the beginning of \fIovector\fP, and
1280 nigel 63 continuing up to two-thirds of its length at the most. The first element of a
1281     pair is set to the offset of the first character in a substring, and the second
1282     is set to the offset of the first character after the end of a substring. The
1283 nigel 75 first pair, \fIovector[0]\fP and \fIovector[1]\fP, identify the portion of the
1284 nigel 63 subject string matched by the entire pattern. The next pair is used for the
1285 nigel 75 first capturing subpattern, and so on. The value returned by \fBpcre_exec()\fP
1286 nigel 91 is one more than the highest numbered pair that has been set. For example, if
1287     two substrings have been captured, the returned value is 3. If there are no
1288     capturing subpatterns, the return value from a successful match is 1,
1289     indicating that just the first pair of offsets has been set.
1290 nigel 75 .P
1291 nigel 63 If a capturing subpattern is matched repeatedly, it is the last portion of the
1292 nigel 75 string that it matched that is returned.
1293     .P
1294     If the vector is too small to hold all the captured substring offsets, it is
1295     used as far as possible (up to two-thirds of its length), and the function
1296     returns a value of zero. In particular, if the substring offsets are not of
1297     interest, \fBpcre_exec()\fP may be called with \fIovector\fP passed as NULL and
1298     \fIovecsize\fP as zero. However, if the pattern contains back references and
1299     the \fIovector\fP is not big enough to remember the related substrings, PCRE
1300     has to get additional memory for use during matching. Thus it is usually
1301     advisable to supply an \fIovector\fP.
1302     .P
1303 nigel 91 The \fBpcre_info()\fP function can be used to find out how many capturing
1304 nigel 63 subpatterns there are in a compiled pattern. The smallest size for
1305 nigel 75 \fIovector\fP that will allow for \fIn\fP captured substrings, in addition to
1306     the offsets of the substring matched by the whole pattern, is (\fIn\fP+1)*3.
1307 nigel 91 .P
1308     It is possible for capturing subpattern number \fIn+1\fP to match some part of
1309     the subject when subpattern \fIn\fP has not been used at all. For example, if
1310     the string "abc" is matched against the pattern (a|(z))(bc) the return from the
1311     function is 4, and subpatterns 1 and 3 are matched, but 2 is not. When this
1312     happens, both values in the offset pairs corresponding to unused subpatterns
1313     are set to -1.
1314     .P
1315     Offset values that correspond to unused subpatterns at the end of the
1316     expression are also set to -1. For example, if the string "abc" is matched
1317     against the pattern (abc)(x(yz)?)? subpatterns 2 and 3 are not matched. The
1318     return from the function is 2, because the highest used capturing subpattern
1319     number is 1. However, you can refer to the offsets for the second and third
1320     capturing subpatterns if you wish (assuming the vector is large enough, of
1321     course).
1322     .P
1323     Some convenience functions are provided for extracting the captured substrings
1324     as separate strings. These are described below.
1325 nigel 75 .
1326 nigel 77 .\" HTML <a name="errorlist"></a>
1327 nigel 91 .SS "Error return values from \fBpcre_exec()\fP"
1328 nigel 75 .rs
1329     .sp
1330     If \fBpcre_exec()\fP fails, it returns a negative number. The following are
1331 nigel 63 defined in the header file:
1332 nigel 75 .sp
1333 nigel 63 PCRE_ERROR_NOMATCH (-1)
1334 nigel 75 .sp
1335 nigel 63 The subject string did not match the pattern.
1336 nigel 75 .sp
1337 nigel 63 PCRE_ERROR_NULL (-2)
1338 nigel 75 .sp
1339     Either \fIcode\fP or \fIsubject\fP was passed as NULL, or \fIovector\fP was
1340     NULL and \fIovecsize\fP was not zero.
1341     .sp
1342 nigel 63 PCRE_ERROR_BADOPTION (-3)
1343 nigel 75 .sp
1344     An unrecognized bit was set in the \fIoptions\fP argument.
1345     .sp
1346 nigel 63 PCRE_ERROR_BADMAGIC (-4)
1347 nigel 75 .sp
1348 nigel 63 PCRE stores a 4-byte "magic number" at the start of the compiled code, to catch
1349 nigel 75 the case when it is passed a junk pointer and to detect when a pattern that was
1350     compiled in an environment of one endianness is run in an environment with the
1351     other endianness. This is the error that PCRE gives when the magic number is
1352     not present.
1353     .sp
1354 nigel 93 PCRE_ERROR_UNKNOWN_OPCODE (-5)
1355 nigel 75 .sp
1356 nigel 63 While running the pattern match, an unknown item was encountered in the
1357     compiled pattern. This error could be caused by a bug in PCRE or by overwriting
1358     of the compiled pattern.
1359 nigel 75 .sp
1360 nigel 63 PCRE_ERROR_NOMEMORY (-6)
1361 nigel 75 .sp
1362     If a pattern contains back references, but the \fIovector\fP that is passed to
1363     \fBpcre_exec()\fP is not big enough to remember the referenced substrings, PCRE
1364 nigel 63 gets a block of memory at the start of matching to use for this purpose. If the
1365 nigel 75 call via \fBpcre_malloc()\fP fails, this error is given. The memory is
1366     automatically freed at the end of matching.
1367     .sp
1368 nigel 63 PCRE_ERROR_NOSUBSTRING (-7)
1369 nigel 75 .sp
1370     This error is used by the \fBpcre_copy_substring()\fP,
1371     \fBpcre_get_substring()\fP, and \fBpcre_get_substring_list()\fP functions (see
1372     below). It is never returned by \fBpcre_exec()\fP.
1373     .sp
1374 nigel 63 PCRE_ERROR_MATCHLIMIT (-8)
1375 nigel 75 .sp
1376 nigel 87 The backtracking limit, as specified by the \fImatch_limit\fP field in a
1377     \fBpcre_extra\fP structure (or defaulted) was reached. See the description
1378     above.
1379     .sp
1380 nigel 63 PCRE_ERROR_CALLOUT (-9)
1381 nigel 75 .sp
1382     This error is never generated by \fBpcre_exec()\fP itself. It is provided for
1383 nigel 63 use by callout functions that want to yield a distinctive error code. See the
1384 nigel 75 .\" HREF
1385     \fBpcrecallout\fP
1386     .\"
1387     documentation for details.
1388     .sp
1389 nigel 73 PCRE_ERROR_BADUTF8 (-10)
1390 nigel 75 .sp
1391 nigel 71 A string that contains an invalid UTF-8 byte sequence was passed as a subject.
1392 nigel 75 .sp
1393 nigel 73 PCRE_ERROR_BADUTF8_OFFSET (-11)
1394 nigel 75 .sp
1395 nigel 73 The UTF-8 byte sequence that was passed as a subject was valid, but the value
1396 nigel 75 of \fIstartoffset\fP did not point to the beginning of a UTF-8 character.
1397     .sp
1398 nigel 77 PCRE_ERROR_PARTIAL (-12)
1399 nigel 75 .sp
1400     The subject string did not match, but it did match partially. See the
1401     .\" HREF
1402     \fBpcrepartial\fP
1403     .\"
1404     documentation for details of partial matching.
1405     .sp
1406 nigel 77 PCRE_ERROR_BADPARTIAL (-13)
1407 nigel 75 .sp
1408     The PCRE_PARTIAL option was used with a compiled pattern containing items that
1409     are not supported for partial matching. See the
1410     .\" HREF
1411     \fBpcrepartial\fP
1412     .\"
1413     documentation for details of partial matching.
1414     .sp
1415 nigel 77 PCRE_ERROR_INTERNAL (-14)
1416 nigel 75 .sp
1417     An unexpected internal error has occurred. This error could be caused by a bug
1418     in PCRE or by overwriting of the compiled pattern.
1419     .sp
1420 nigel 77 PCRE_ERROR_BADCOUNT (-15)
1421 nigel 75 .sp
1422     This error is given if the value of the \fIovecsize\fP argument is negative.
1423 nigel 93 .sp
1425     .sp
1426     The internal recursion limit, as specified by the \fImatch_limit_recursion\fP
1427     field in a \fBpcre_extra\fP structure (or defaulted) was reached. See the
1428     description above.
1429     .sp
1431     .sp
1432     When a group that can match an empty substring is repeated with an unbounded
1433     upper limit, the subject position at the start of the group must be remembered,
1434     so that a test for an empty string can be made when the end of the group is
1435     reached. Some workspace is required for this; if it runs out, this error is
1436     given.
1437     .sp
1439     .sp
1440     An invalid combination of PCRE_NEWLINE_\fIxxx\fP options was given.
1441     .P
1442     Error numbers -16 to -20 are not used by \fBpcre_exec()\fP.
1443 nigel 75 .
1444     .
1446 nigel 63 .rs
1447     .sp
1448 nigel 75 .B int pcre_copy_substring(const char *\fIsubject\fP, int *\fIovector\fP,
1449 nigel 63 .ti +5n
1450 nigel 75 .B int \fIstringcount\fP, int \fIstringnumber\fP, char *\fIbuffer\fP,
1451 nigel 63 .ti +5n
1452 nigel 75 .B int \fIbuffersize\fP);
1453 nigel 63 .PP
1454 nigel 75 .B int pcre_get_substring(const char *\fIsubject\fP, int *\fIovector\fP,
1455 nigel 63 .ti +5n
1456 nigel 75 .B int \fIstringcount\fP, int \fIstringnumber\fP,
1457 nigel 63 .ti +5n
1458 nigel 75 .B const char **\fIstringptr\fP);
1459 nigel 63 .PP
1460 nigel 75 .B int pcre_get_substring_list(const char *\fIsubject\fP,
1461 nigel 63 .ti +5n
1462 nigel 75 .B int *\fIovector\fP, int \fIstringcount\fP, "const char ***\fIlistptr\fP);"
1463 nigel 63 .PP
1464     Captured substrings can be accessed directly by using the offsets returned by
1465 nigel 75 \fBpcre_exec()\fP in \fIovector\fP. For convenience, the functions
1466     \fBpcre_copy_substring()\fP, \fBpcre_get_substring()\fP, and
1467     \fBpcre_get_substring_list()\fP are provided for extracting captured substrings
1468 nigel 63 as new, separate, zero-terminated strings. These functions identify substrings
1469     by number. The next section describes functions for extracting named
1470 nigel 91 substrings.
1471 nigel 75 .P
1472 nigel 91 A substring that contains a binary zero is correctly extracted and has a
1473     further zero added on the end, but the result is not, of course, a C string.
1474     However, you can process such a string by referring to the length that is
1475     returned by \fBpcre_copy_substring()\fP and \fBpcre_get_substring()\fP.
1476     Unfortunately, the interface to \fBpcre_get_substring_list()\fP is not adequate
1477     for handling strings containing binary zeros, because the end of the final
1478     string is not independently indicated.
1479     .P
1480 nigel 63 The first three arguments are the same for all three of these functions:
1481 nigel 75 \fIsubject\fP is the subject string that has just been successfully matched,
1482     \fIovector\fP is a pointer to the vector of integer offsets that was passed to
1483     \fBpcre_exec()\fP, and \fIstringcount\fP is the number of substrings that were
1484 nigel 63 captured by the match, including the substring that matched the entire regular
1485 nigel 75 expression. This is the value returned by \fBpcre_exec()\fP if it is greater
1486     than zero. If \fBpcre_exec()\fP returned zero, indicating that it ran out of
1487     space in \fIovector\fP, the value passed as \fIstringcount\fP should be the
1488     number of elements in the vector divided by three.
1489     .P
1490     The functions \fBpcre_copy_substring()\fP and \fBpcre_get_substring()\fP
1491     extract a single substring, whose number is given as \fIstringnumber\fP. A
1492     value of zero extracts the substring that matched the entire pattern, whereas
1493     higher values extract the captured substrings. For \fBpcre_copy_substring()\fP,
1494     the string is placed in \fIbuffer\fP, whose length is given by
1495     \fIbuffersize\fP, while for \fBpcre_get_substring()\fP a new block of memory is
1496     obtained via \fBpcre_malloc\fP, and its address is returned via
1497     \fIstringptr\fP. The yield of the function is the length of the string, not
1498 nigel 93 including the terminating zero, or one of these error codes:
1499 nigel 75 .sp
1500 nigel 63 PCRE_ERROR_NOMEMORY (-6)
1501 nigel 75 .sp
1502     The buffer was too small for \fBpcre_copy_substring()\fP, or the attempt to get
1503     memory failed for \fBpcre_get_substring()\fP.
1504     .sp
1505 nigel 63 PCRE_ERROR_NOSUBSTRING (-7)
1506 nigel 75 .sp
1507     There is no substring whose number is \fIstringnumber\fP.
1508     .P
1509     The \fBpcre_get_substring_list()\fP function extracts all available substrings
1510 nigel 63 and builds a list of pointers to them. All this is done in a single block of
1511 nigel 75 memory that is obtained via \fBpcre_malloc\fP. The address of the memory block
1512     is returned via \fIlistptr\fP, which is also the start of the list of string
1513 nigel 63 pointers. The end of the list is marked by a NULL pointer. The yield of the
1514 nigel 93 function is zero if all went well, or the error code
1515 nigel 75 .sp
1516 nigel 63 PCRE_ERROR_NOMEMORY (-6)
1517 nigel 75 .sp
1518 nigel 63 if the attempt to get the memory block failed.
1519 nigel 75 .P
1520 nigel 63 When any of these functions encounter a substring that is unset, which can
1521 nigel 75 happen when capturing subpattern number \fIn+1\fP matches some part of the
1522     subject, but subpattern \fIn\fP has not been used at all, they return an empty
1523 nigel 63 string. This can be distinguished from a genuine zero-length substring by
1524 nigel 75 inspecting the appropriate offset in \fIovector\fP, which is negative for unset
1525 nigel 63 substrings.
1526 nigel 75 .P
1527     The two convenience functions \fBpcre_free_substring()\fP and
1528     \fBpcre_free_substring_list()\fP can be used to free the memory returned by
1529     a previous call of \fBpcre_get_substring()\fP or
1530     \fBpcre_get_substring_list()\fP, respectively. They do nothing more than call
1531     the function pointed to by \fBpcre_free\fP, which of course could be called
1532 nigel 63 directly from a C program. However, PCRE is used in some situations where it is
1533 nigel 91 linked via a special interface to another programming language that cannot use
1534 nigel 75 \fBpcre_free\fP directly; it is for these cases that the functions are
1535 nigel 63 provided.
1536 nigel 75 .
1537     .
1539 nigel 63 .rs
1540     .sp
1541 nigel 75 .B int pcre_get_stringnumber(const pcre *\fIcode\fP,
1542 nigel 63 .ti +5n
1543 nigel 75 .B const char *\fIname\fP);
1544 nigel 63 .PP
1545 nigel 75 .B int pcre_copy_named_substring(const pcre *\fIcode\fP,
1546 nigel 63 .ti +5n
1547 nigel 75 .B const char *\fIsubject\fP, int *\fIovector\fP,
1548     .ti +5n
1549     .B int \fIstringcount\fP, const char *\fIstringname\fP,
1550     .ti +5n
1551     .B char *\fIbuffer\fP, int \fIbuffersize\fP);
1552 nigel 63 .PP
1553 nigel 75 .B int pcre_get_named_substring(const pcre *\fIcode\fP,
1554 nigel 63 .ti +5n
1555 nigel 75 .B const char *\fIsubject\fP, int *\fIovector\fP,
1556 nigel 63 .ti +5n
1557 nigel 75 .B int \fIstringcount\fP, const char *\fIstringname\fP,
1558 nigel 63 .ti +5n
1559 nigel 75 .B const char **\fIstringptr\fP);
1560 nigel 63 .PP
1561 nigel 75 To extract a substring by name, you first have to find associated number.
1562     For example, for this pattern
1563     .sp
1564 nigel 93 (a+)b(?<xxx>\ed+)...
1565 nigel 75 .sp
1566 nigel 91 the number of the subpattern called "xxx" is 2. If the name is known to be
1567     unique (PCRE_DUPNAMES was not set), you can find the number from the name by
1568     calling \fBpcre_get_stringnumber()\fP. The first argument is the compiled
1569     pattern, and the second is the name. The yield of the function is the
1570 nigel 75 subpattern number, or PCRE_ERROR_NOSUBSTRING (-7) if there is no subpattern of
1571     that name.
1572     .P
1573     Given the number, you can extract the substring directly, or use one of the
1574     functions described in the previous section. For convenience, there are also
1575     two functions that do the whole job.
1576     .P
1577 nigel 91 Most of the arguments of \fBpcre_copy_named_substring()\fP and
1578     \fBpcre_get_named_substring()\fP are the same as those for the similarly named
1579 nigel 75 functions that extract by number. As these are described in the previous
1580     section, they are not re-described here. There are just two differences:
1581     .P
1582 nigel 63 First, instead of a substring number, a substring name is given. Second, there
1583     is an extra argument, given at the start, which is a pointer to the compiled
1584     pattern. This is needed in order to gain access to the name-to-number
1585     translation table.
1586 nigel 75 .P
1587     These functions call \fBpcre_get_stringnumber()\fP, and if it succeeds, they
1588 ph10 127 then call \fBpcre_copy_substring()\fP or \fBpcre_get_substring()\fP, as
1589     appropriate. \fBNOTE:\fP If PCRE_DUPNAMES is set and there are duplicate names,
1590     the behaviour may not be what you want (see the next section).
1591 nigel 77 .
1592     .
1594     .rs
1595     .sp
1596     .B int pcre_get_stringtable_entries(const pcre *\fIcode\fP,
1597     .ti +5n
1598     .B const char *\fIname\fP, char **\fIfirst\fP, char **\fIlast\fP);
1599     .PP
1600     When a pattern is compiled with the PCRE_DUPNAMES option, names for subpatterns
1601     are not required to be unique. Normally, patterns with duplicate names are such
1602     that in any one match, only one of the named subpatterns participates. An
1603     example is shown in the
1604     .\" HREF
1605     \fBpcrepattern\fP
1606     .\"
1607     documentation. When duplicates are present, \fBpcre_copy_named_substring()\fP
1608     and \fBpcre_get_named_substring()\fP return the first substring corresponding
1609     to the given name that is set. If none are set, an empty string is returned.
1610     The \fBpcre_get_stringnumber()\fP function returns one of the numbers that are
1611     associated with the name, but it is not defined which it is.
1612     .sp
1613     If you want to get full details of all captured substrings for a given name,
1614     you must use the \fBpcre_get_stringtable_entries()\fP function. The first
1615     argument is the compiled pattern, and the second is the name. The third and
1616     fourth are pointers to variables which are updated by the function. After it
1617     has run, they point to the first and last entries in the name-to-number table
1618     for the given name. The function itself returns the length of each entry, or
1619 nigel 93 PCRE_ERROR_NOSUBSTRING (-7) if there are none. The format of the table is
1620     described above in the section entitled \fIInformation about a pattern\fP.
1621     Given all the relevant entries for the name, you can extract each of their
1622     numbers, and hence the captured data, if any.
1623 nigel 91 .
1624     .
1626     .rs
1627     .sp
1628     The traditional matching function uses a similar algorithm to Perl, which stops
1629     when it finds the first match, starting at a given point in the subject. If you
1630     want to find all possible matches, or the longest possible match, consider
1631     using the alternative matching function (see below) instead. If you cannot use
1632     the alternative function, but still need to find all possible matches, you
1633     can kludge it up by making use of the callout facility, which is described in
1634     the
1635     .\" HREF
1636     \fBpcrecallout\fP
1637     .\"
1638     documentation.
1639 nigel 75 .P
1640 nigel 77 What you have to do is to insert a callout right at the end of the pattern.
1641     When your callout function is called, extract and save the current matched
1642     substring. Then return 1, which forces \fBpcre_exec()\fP to backtrack and try
1643     other alternatives. Ultimately, when it runs out of matches, \fBpcre_exec()\fP
1644     will yield PCRE_ERROR_NOMATCH.
1645     .
1646     .
1647     .\" HTML <a name="dfamatch"></a>
1649     .rs
1650     .sp
1651     .B int pcre_dfa_exec(const pcre *\fIcode\fP, "const pcre_extra *\fIextra\fP,"
1652     .ti +5n
1653     .B "const char *\fIsubject\fP," int \fIlength\fP, int \fIstartoffset\fP,
1654     .ti +5n
1655     .B int \fIoptions\fP, int *\fIovector\fP, int \fIovecsize\fP,
1656     .ti +5n
1657     .B int *\fIworkspace\fP, int \fIwscount\fP);
1658     .P
1659     The function \fBpcre_dfa_exec()\fP is called to match a subject string against
1660 nigel 93 a compiled pattern, using a matching algorithm that scans the subject string
1661     just once, and does not backtrack. This has different characteristics to the
1662     normal algorithm, and is not compatible with Perl. Some of the features of PCRE
1663     patterns are not supported. Nevertheless, there are times when this kind of
1664     matching can be useful. For a discussion of the two matching algorithms, see
1665     the
1666 nigel 77 .\" HREF
1667     \fBpcrematching\fP
1668     .\"
1669     documentation.
1670     .P
1671     The arguments for the \fBpcre_dfa_exec()\fP function are the same as for
1672     \fBpcre_exec()\fP, plus two extras. The \fIovector\fP argument is used in a
1673     different way, and this is described below. The other common arguments are used
1674     in the same way as for \fBpcre_exec()\fP, so their description is not repeated
1675     here.
1676     .P
1677     The two additional arguments provide workspace for the function. The workspace
1678     vector should contain at least 20 elements. It is used for keeping track of
1679     multiple paths through the pattern tree. More workspace will be needed for
1680 nigel 91 patterns and subjects where there are a lot of potential matches.
1681 nigel 77 .P
1682 nigel 87 Here is an example of a simple call to \fBpcre_dfa_exec()\fP:
1683 nigel 77 .sp
1684     int rc;
1685     int ovector[10];
1686     int wspace[20];
1687 nigel 87 rc = pcre_dfa_exec(
1688 nigel 77 re, /* result of pcre_compile() */
1689     NULL, /* we didn't study the pattern */
1690     "some string", /* the subject string */
1691     11, /* the length of the subject string */
1692     0, /* start at offset 0 in the subject */
1693     0, /* default options */
1694     ovector, /* vector of integers for substring information */
1695     10, /* number of elements (NOT size in bytes) */
1696     wspace, /* working space vector */
1697     20); /* number of elements (NOT size in bytes) */
1698     .
1699     .SS "Option bits for \fBpcre_dfa_exec()\fP"
1700     .rs
1701     .sp
1702     The unused bits of the \fIoptions\fP argument for \fBpcre_dfa_exec()\fP must be
1703 nigel 91 zero. The only bits that may be set are PCRE_ANCHORED, PCRE_NEWLINE_\fIxxx\fP,
1705 nigel 77 PCRE_DFA_SHORTEST, and PCRE_DFA_RESTART. All but the last three of these are
1706     the same as for \fBpcre_exec()\fP, so their description is not repeated here.
1707     .sp
1709     .sp
1710     This has the same general effect as it does for \fBpcre_exec()\fP, but the
1711     details are slightly different. When PCRE_PARTIAL is set for
1712     \fBpcre_dfa_exec()\fP, the return code PCRE_ERROR_NOMATCH is converted into
1713     PCRE_ERROR_PARTIAL if the end of the subject is reached, there have been no
1714     complete matches, but there is still at least one matching possibility. The
1715     portion of the string that provided the partial match is set as the first
1716     matching string.
1717     .sp
1719     .sp
1720     Setting the PCRE_DFA_SHORTEST option causes the matching algorithm to stop as
1721 nigel 93 soon as it has found one match. Because of the way the alternative algorithm
1722     works, this is necessarily the shortest possible match at the first possible
1723     matching point in the subject string.
1724 nigel 77 .sp
1726     .sp
1727     When \fBpcre_dfa_exec()\fP is called with the PCRE_PARTIAL option, and returns
1728     a partial match, it is possible to call it again, with additional subject
1729     characters, and have it continue with the same match. The PCRE_DFA_RESTART
1730     option requests this action; when it is set, the \fIworkspace\fP and
1731     \fIwscount\fP options must reference the same vector as before because data
1732     about the match so far is left in them after a partial match. There is more
1733     discussion of this facility in the
1734     .\" HREF
1735     \fBpcrepartial\fP
1736     .\"
1737     documentation.
1738     .
1739     .SS "Successful returns from \fBpcre_dfa_exec()\fP"
1740     .rs
1741     .sp
1742     When \fBpcre_dfa_exec()\fP succeeds, it may have matched more than one
1743     substring in the subject. Note, however, that all the matches from one run of
1744     the function start at the same point in the subject. The shorter matches are
1745     all initial substrings of the longer matches. For example, if the pattern
1746     .sp
1747     <.*>
1748     .sp
1749     is matched against the string
1750     .sp
1751     This is <something> <something else> <something further> no more
1752     .sp
1753     the three matched strings are
1754     .sp
1755     <something>
1756     <something> <something else>
1757     <something> <something else> <something further>
1758     .sp
1759     On success, the yield of the function is a number greater than zero, which is
1760     the number of matched substrings. The substrings themselves are returned in
1761     \fIovector\fP. Each string uses two elements; the first is the offset to the
1762 nigel 93 start, and the second is the offset to the end. In fact, all the strings have
1763     the same start offset. (Space could have been saved by giving this only once,
1764     but it was decided to retain some compatibility with the way \fBpcre_exec()\fP
1765     returns data, even though the meaning of the strings is different.)
1766 nigel 77 .P
1767     The strings are returned in reverse order of length; that is, the longest
1768     matching string is given first. If there were too many matches to fit into
1769     \fIovector\fP, the yield of the function is zero, and the vector is filled with
1770     the longest matches.
1771     .
1772     .SS "Error returns from \fBpcre_dfa_exec()\fP"
1773     .rs
1774     .sp
1775     The \fBpcre_dfa_exec()\fP function returns a negative number when it fails.
1776     Many of the errors are the same as for \fBpcre_exec()\fP, and these are
1777     described
1778     .\" HTML <a href="#errorlist">
1779     .\" </a>
1780     above.
1781     .\"
1782     There are in addition the following errors that are specific to
1783     \fBpcre_dfa_exec()\fP:
1784     .sp
1785     PCRE_ERROR_DFA_UITEM (-16)
1786     .sp
1787     This return is given if \fBpcre_dfa_exec()\fP encounters an item in the pattern
1788     that it does not support, for instance, the use of \eC or a back reference.
1789     .sp
1790     PCRE_ERROR_DFA_UCOND (-17)
1791     .sp
1792 nigel 93 This return is given if \fBpcre_dfa_exec()\fP encounters a condition item that
1793     uses a back reference for the condition, or a test for recursion in a specific
1794     group. These are not supported.
1795 nigel 77 .sp
1797     .sp
1798     This return is given if \fBpcre_dfa_exec()\fP is called with an \fIextra\fP
1799     block that contains a setting of the \fImatch_limit\fP field. This is not
1800     supported (it is meaningless).
1801     .sp
1802     PCRE_ERROR_DFA_WSSIZE (-19)
1803     .sp
1804     This return is given if \fBpcre_dfa_exec()\fP runs out of space in the
1805     \fIworkspace\fP vector.
1806     .sp
1808     .sp
1809     When a recursive subpattern is processed, the matching function calls itself
1810     recursively, using private vectors for \fIovector\fP and \fIworkspace\fP. This
1811     error is given if the output vector is not large enough. This should be
1812     extremely rare, as a vector of size 1000 is used.
1813 nigel 93 .
1814     .
1815     .SH "SEE ALSO"
1816     .rs
1817     .sp
1818     \fBpcrebuild\fP(3), \fBpcrecallout\fP(3), \fBpcrecpp(3)\fP(3),
1819     \fBpcrematching\fP(3), \fBpcrepartial\fP(3), \fBpcreposix\fP(3),
1820     \fBpcreprecompile\fP(3), \fBpcresample\fP(3), \fBpcrestack\fP(3).
1821 ph10 99 .
1822     .
1823     .SH AUTHOR
1824     .rs
1825     .sp
1826     .nf
1827     Philip Hazel
1828     University Computing Service
1829     Cambridge CB2 3QH, England.
1830     .fi
1831     .
1832     .
1833     .SH REVISION
1834     .rs
1835     .sp
1836     .nf
1837     Last updated: 06 March 2007
1838     Copyright (c) 1997-2007 University of Cambridge.
1839     .fi


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