ViewVC logotype

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

Parent Directory Parent Directory | Revision Log Revision Log

Revision 91 - (hide annotations) (download) (as text)
Sat Feb 24 21:41:34 2007 UTC (8 years, 2 months ago) by nigel
File MIME type: text/html
File size: 79800 byte(s)
Load pcre-6.7 into code/trunk.

1 nigel 63 <html>
2     <head>
3     <title>pcreapi specification</title>
4     </head>
5     <body bgcolor="#FFFFFF" text="#00005A" link="#0066FF" alink="#3399FF" vlink="#2222BB">
6 nigel 75 <h1>pcreapi man page</h1>
7     <p>
8     Return to the <a href="index.html">PCRE index page</a>.
9     </p>
10     <p>
11     This page is part of the PCRE HTML documentation. It was generated automatically
12     from the original man page. If there is any nonsense in it, please consult the
13     man page, in case the conversion went wrong.
14     <br>
15 nigel 63 <ul>
16 nigel 75 <li><a name="TOC1" href="#SEC1">PCRE NATIVE API</a>
17     <li><a name="TOC2" href="#SEC2">PCRE API OVERVIEW</a>
18 nigel 91 <li><a name="TOC3" href="#SEC3">NEWLINES</a>
19     <li><a name="TOC4" href="#SEC4">MULTITHREADING</a>
20     <li><a name="TOC5" href="#SEC5">SAVING PRECOMPILED PATTERNS FOR LATER USE</a>
21     <li><a name="TOC6" href="#SEC6">CHECKING BUILD-TIME OPTIONS</a>
22     <li><a name="TOC7" href="#SEC7">COMPILING A PATTERN</a>
23     <li><a name="TOC8" href="#SEC8">COMPILATION ERROR CODES</a>
24     <li><a name="TOC9" href="#SEC9">STUDYING A PATTERN</a>
25     <li><a name="TOC10" href="#SEC10">LOCALE SUPPORT</a>
26     <li><a name="TOC11" href="#SEC11">INFORMATION ABOUT A PATTERN</a>
27     <li><a name="TOC12" href="#SEC12">OBSOLETE INFO FUNCTION</a>
28     <li><a name="TOC13" href="#SEC13">REFERENCE COUNTS</a>
29     <li><a name="TOC14" href="#SEC14">MATCHING A PATTERN: THE TRADITIONAL FUNCTION</a>
30     <li><a name="TOC15" href="#SEC15">EXTRACTING CAPTURED SUBSTRINGS BY NUMBER</a>
31     <li><a name="TOC16" href="#SEC16">EXTRACTING CAPTURED SUBSTRINGS BY NAME</a>
32     <li><a name="TOC17" href="#SEC17">DUPLICATE SUBPATTERN NAMES</a>
33     <li><a name="TOC18" href="#SEC18">FINDING ALL POSSIBLE MATCHES</a>
34     <li><a name="TOC19" href="#SEC19">MATCHING A PATTERN: THE ALTERNATIVE FUNCTION</a>
35 nigel 63 </ul>
36 nigel 75 <br><a name="SEC1" href="#TOC1">PCRE NATIVE API</a><br>
37 nigel 63 <P>
38     <b>#include &#60;pcre.h&#62;</b>
39     </P>
40     <P>
41     <b>pcre *pcre_compile(const char *<i>pattern</i>, int <i>options</i>,</b>
42     <b>const char **<i>errptr</i>, int *<i>erroffset</i>,</b>
43     <b>const unsigned char *<i>tableptr</i>);</b>
44     </P>
45     <P>
46 nigel 77 <b>pcre *pcre_compile2(const char *<i>pattern</i>, int <i>options</i>,</b>
47     <b>int *<i>errorcodeptr</i>,</b>
48     <b>const char **<i>errptr</i>, int *<i>erroffset</i>,</b>
49     <b>const unsigned char *<i>tableptr</i>);</b>
50     </P>
51     <P>
52 nigel 63 <b>pcre_extra *pcre_study(const pcre *<i>code</i>, int <i>options</i>,</b>
53     <b>const char **<i>errptr</i>);</b>
54     </P>
55     <P>
56     <b>int pcre_exec(const pcre *<i>code</i>, const pcre_extra *<i>extra</i>,</b>
57     <b>const char *<i>subject</i>, int <i>length</i>, int <i>startoffset</i>,</b>
58     <b>int <i>options</i>, int *<i>ovector</i>, int <i>ovecsize</i>);</b>
59     </P>
60     <P>
61 nigel 77 <b>int pcre_dfa_exec(const pcre *<i>code</i>, const pcre_extra *<i>extra</i>,</b>
62     <b>const char *<i>subject</i>, int <i>length</i>, int <i>startoffset</i>,</b>
63     <b>int <i>options</i>, int *<i>ovector</i>, int <i>ovecsize</i>,</b>
64     <b>int *<i>workspace</i>, int <i>wscount</i>);</b>
65     </P>
66     <P>
67 nigel 63 <b>int pcre_copy_named_substring(const pcre *<i>code</i>,</b>
68     <b>const char *<i>subject</i>, int *<i>ovector</i>,</b>
69     <b>int <i>stringcount</i>, const char *<i>stringname</i>,</b>
70     <b>char *<i>buffer</i>, int <i>buffersize</i>);</b>
71     </P>
72     <P>
73     <b>int pcre_copy_substring(const char *<i>subject</i>, int *<i>ovector</i>,</b>
74     <b>int <i>stringcount</i>, int <i>stringnumber</i>, char *<i>buffer</i>,</b>
75     <b>int <i>buffersize</i>);</b>
76     </P>
77     <P>
78     <b>int pcre_get_named_substring(const pcre *<i>code</i>,</b>
79     <b>const char *<i>subject</i>, int *<i>ovector</i>,</b>
80     <b>int <i>stringcount</i>, const char *<i>stringname</i>,</b>
81     <b>const char **<i>stringptr</i>);</b>
82     </P>
83     <P>
84     <b>int pcre_get_stringnumber(const pcre *<i>code</i>,</b>
85     <b>const char *<i>name</i>);</b>
86     </P>
87     <P>
88 nigel 91 <b>int pcre_get_stringtable_entries(const pcre *<i>code</i>,</b>
89     <b>const char *<i>name</i>, char **<i>first</i>, char **<i>last</i>);</b>
90     </P>
91     <P>
92 nigel 63 <b>int pcre_get_substring(const char *<i>subject</i>, int *<i>ovector</i>,</b>
93     <b>int <i>stringcount</i>, int <i>stringnumber</i>,</b>
94     <b>const char **<i>stringptr</i>);</b>
95     </P>
96     <P>
97     <b>int pcre_get_substring_list(const char *<i>subject</i>,</b>
98     <b>int *<i>ovector</i>, int <i>stringcount</i>, const char ***<i>listptr</i>);</b>
99     </P>
100     <P>
101     <b>void pcre_free_substring(const char *<i>stringptr</i>);</b>
102     </P>
103     <P>
104     <b>void pcre_free_substring_list(const char **<i>stringptr</i>);</b>
105     </P>
106     <P>
107     <b>const unsigned char *pcre_maketables(void);</b>
108     </P>
109     <P>
110     <b>int pcre_fullinfo(const pcre *<i>code</i>, const pcre_extra *<i>extra</i>,</b>
111     <b>int <i>what</i>, void *<i>where</i>);</b>
112     </P>
113     <P>
114     <b>int pcre_info(const pcre *<i>code</i>, int *<i>optptr</i>, int</b>
115     <b>*<i>firstcharptr</i>);</b>
116     </P>
117     <P>
118 nigel 77 <b>int pcre_refcount(pcre *<i>code</i>, int <i>adjust</i>);</b>
119     </P>
120     <P>
121 nigel 63 <b>int pcre_config(int <i>what</i>, void *<i>where</i>);</b>
122     </P>
123     <P>
124     <b>char *pcre_version(void);</b>
125     </P>
126     <P>
127     <b>void *(*pcre_malloc)(size_t);</b>
128     </P>
129     <P>
130     <b>void (*pcre_free)(void *);</b>
131     </P>
132     <P>
133 nigel 73 <b>void *(*pcre_stack_malloc)(size_t);</b>
134     </P>
135     <P>
136     <b>void (*pcre_stack_free)(void *);</b>
137     </P>
138     <P>
139 nigel 63 <b>int (*pcre_callout)(pcre_callout_block *);</b>
140     </P>
141 nigel 75 <br><a name="SEC2" href="#TOC1">PCRE API OVERVIEW</a><br>
142 nigel 63 <P>
143 nigel 77 PCRE has its own native API, which is described in this document. There is
144     also a set of wrapper functions that correspond to the POSIX regular expression
145     API. These are described in the
146 nigel 75 <a href="pcreposix.html"><b>pcreposix</b></a>
147 nigel 77 documentation. Both of these APIs define a set of C function calls. A C++
148     wrapper is distributed with PCRE. It is documented in the
149     <a href="pcrecpp.html"><b>pcrecpp</b></a>
150     page.
151 nigel 63 </P>
152     <P>
153 nigel 77 The native API C function prototypes are defined in the header file
154     <b>pcre.h</b>, and on Unix systems the library itself is called <b>libpcre</b>.
155     It can normally be accessed by adding <b>-lpcre</b> to the command for linking
156     an application that uses PCRE. The header file defines the macros PCRE_MAJOR
157     and PCRE_MINOR to contain the major and minor release numbers for the library.
158 nigel 75 Applications can use these to include support for different releases of PCRE.
159 nigel 63 </P>
160     <P>
161 nigel 77 The functions <b>pcre_compile()</b>, <b>pcre_compile2()</b>, <b>pcre_study()</b>,
162     and <b>pcre_exec()</b> are used for compiling and matching regular expressions
163     in a Perl-compatible manner. A sample program that demonstrates the simplest
164     way of using them is provided in the file called <i>pcredemo.c</i> in the source
165     distribution. The
166 nigel 75 <a href="pcresample.html"><b>pcresample</b></a>
167     documentation describes how to run it.
168 nigel 63 </P>
169     <P>
170 nigel 77 A second matching function, <b>pcre_dfa_exec()</b>, which is not
171     Perl-compatible, is also provided. This uses a different algorithm for the
172 nigel 91 matching. The alternative algorithm finds all possible matches (at a given
173     point in the subject). However, this algorithm does not return captured
174 nigel 77 substrings. A description of the two matching algorithms and their advantages
175     and disadvantages is given in the
176     <a href="pcrematching.html"><b>pcrematching</b></a>
177     documentation.
178     </P>
179     <P>
180 nigel 75 In addition to the main compiling and matching functions, there are convenience
181 nigel 77 functions for extracting captured substrings from a subject string that is
182     matched by <b>pcre_exec()</b>. They are:
183 nigel 63 <pre>
184     <b>pcre_copy_substring()</b>
185     <b>pcre_copy_named_substring()</b>
186     <b>pcre_get_substring()</b>
187     <b>pcre_get_named_substring()</b>
188     <b>pcre_get_substring_list()</b>
189 nigel 75 <b>pcre_get_stringnumber()</b>
190 nigel 91 <b>pcre_get_stringtable_entries()</b>
191 nigel 75 </pre>
192 nigel 63 <b>pcre_free_substring()</b> and <b>pcre_free_substring_list()</b> are also
193     provided, to free the memory used for extracted strings.
194     </P>
195     <P>
196 nigel 75 The function <b>pcre_maketables()</b> is used to build a set of character tables
197 nigel 77 in the current locale for passing to <b>pcre_compile()</b>, <b>pcre_exec()</b>,
198     or <b>pcre_dfa_exec()</b>. This is an optional facility that is provided for
199     specialist use. Most commonly, no special tables are passed, in which case
200     internal tables that are generated when PCRE is built are used.
201 nigel 63 </P>
202     <P>
203     The function <b>pcre_fullinfo()</b> is used to find out information about a
204 nigel 75 compiled pattern; <b>pcre_info()</b> is an obsolete version that returns only
205 nigel 63 some of the available information, but is retained for backwards compatibility.
206     The function <b>pcre_version()</b> returns a pointer to a string containing the
207     version of PCRE and its date of release.
208     </P>
209     <P>
210 nigel 77 The function <b>pcre_refcount()</b> maintains a reference count in a data block
211     containing a compiled pattern. This is provided for the benefit of
212     object-oriented applications.
213     </P>
214     <P>
215 nigel 63 The global variables <b>pcre_malloc</b> and <b>pcre_free</b> initially contain
216 nigel 75 the entry points of the standard <b>malloc()</b> and <b>free()</b> functions,
217 nigel 63 respectively. PCRE calls the memory management functions via these variables,
218     so a calling program can replace them if it wishes to intercept the calls. This
219     should be done before calling any PCRE functions.
220     </P>
221     <P>
222 nigel 73 The global variables <b>pcre_stack_malloc</b> and <b>pcre_stack_free</b> are also
223     indirections to memory management functions. These special functions are used
224     only when PCRE is compiled to use the heap for remembering data, instead of
225 nigel 91 recursive function calls, when running the <b>pcre_exec()</b> function. See the
226     <a href="pcrebuild.html"><b>pcrebuild</b></a>
227     documentation for details of how to do this. It is a non-standard way of
228     building PCRE, for use in environments that have limited stacks. Because of the
229     greater use of memory management, it runs more slowly. Separate functions are
230     provided so that special-purpose external code can be used for this case. When
231     used, these functions are always called in a stack-like manner (last obtained,
232     first freed), and always for memory blocks of the same size. There is a
233     discussion about PCRE's stack usage in the
234     <a href="pcrestack.html"><b>pcrestack</b></a>
235     documentation.
236 nigel 73 </P>
237     <P>
238 nigel 63 The global variable <b>pcre_callout</b> initially contains NULL. It can be set
239     by the caller to a "callout" function, which PCRE will then call at specified
240 nigel 75 points during a matching operation. Details are given in the
241     <a href="pcrecallout.html"><b>pcrecallout</b></a>
242 nigel 63 documentation.
243     </P>
244 nigel 91 <br><a name="SEC3" href="#TOC1">NEWLINES</a><br>
245 nigel 63 <P>
246 nigel 91 PCRE supports three different conventions for indicating line breaks in
247     strings: a single CR character, a single LF character, or the two-character
248     sequence CRLF. All three are used as "standard" by different operating systems.
249     When PCRE is built, a default can be specified. The default default is LF,
250     which is the Unix standard. When PCRE is run, the default can be overridden,
251     either when a pattern is compiled, or when it is matched.
252     <br>
253     <br>
254     In the PCRE documentation the word "newline" is used to mean "the character or
255     pair of characters that indicate a line break".
256     </P>
257     <br><a name="SEC4" href="#TOC1">MULTITHREADING</a><br>
258     <P>
259 nigel 63 The PCRE functions can be used in multi-threading applications, with the
260 nigel 73 proviso that the memory management functions pointed to by <b>pcre_malloc</b>,
261     <b>pcre_free</b>, <b>pcre_stack_malloc</b>, and <b>pcre_stack_free</b>, and the
262     callout function pointed to by <b>pcre_callout</b>, are shared by all threads.
263 nigel 63 </P>
264     <P>
265     The compiled form of a regular expression is not altered during matching, so
266     the same compiled pattern can safely be used by several threads at once.
267     </P>
268 nigel 91 <br><a name="SEC5" href="#TOC1">SAVING PRECOMPILED PATTERNS FOR LATER USE</a><br>
269 nigel 63 <P>
270 nigel 75 The compiled form of a regular expression can be saved and re-used at a later
271     time, possibly by a different program, and even on a host other than the one on
272     which it was compiled. Details are given in the
273     <a href="pcreprecompile.html"><b>pcreprecompile</b></a>
274     documentation.
275     </P>
276 nigel 91 <br><a name="SEC6" href="#TOC1">CHECKING BUILD-TIME OPTIONS</a><br>
277 nigel 75 <P>
278 nigel 63 <b>int pcre_config(int <i>what</i>, void *<i>where</i>);</b>
279     </P>
280     <P>
281     The function <b>pcre_config()</b> makes it possible for a PCRE client to
282     discover which optional features have been compiled into the PCRE library. The
283     <a href="pcrebuild.html"><b>pcrebuild</b></a>
284     documentation has more details about these optional features.
285     </P>
286     <P>
287     The first argument for <b>pcre_config()</b> is an integer, specifying which
288     information is required; the second argument is a pointer to a variable into
289     which the information is placed. The following information is available:
290     <pre>
292 nigel 75 </pre>
293 nigel 63 The output is an integer that is set to one if UTF-8 support is available;
294     otherwise it is set to zero.
295     <pre>
297     </pre>
298     The output is an integer that is set to one if support for Unicode character
299     properties is available; otherwise it is set to zero.
300     <pre>
302 nigel 75 </pre>
303 nigel 91 The output is an integer whose value specifies the default character sequence
304     that is recognized as meaning "newline". The three values that are supported
305     are: 10 for LF, 13 for CR, and 3338 for CRLF. The default should normally be
306     the standard sequence for your operating system.
307 nigel 63 <pre>
309 nigel 75 </pre>
310 nigel 63 The output is an integer that contains the number of bytes used for internal
311     linkage in compiled regular expressions. The value is 2, 3, or 4. Larger values
312     allow larger regular expressions to be compiled, at the expense of slower
313     matching. The default value of 2 is sufficient for all but the most massive
314     patterns, since it allows the compiled pattern to be up to 64K in size.
315     <pre>
317 nigel 75 </pre>
318 nigel 63 The output is an integer that contains the threshold above which the POSIX
319     interface uses <b>malloc()</b> for output vectors. Further details are given in
320 nigel 75 the
321     <a href="pcreposix.html"><b>pcreposix</b></a>
322     documentation.
323 nigel 63 <pre>
325 nigel 75 </pre>
326 nigel 63 The output is an integer that gives the default limit for the number of
327     internal matching function calls in a <b>pcre_exec()</b> execution. Further
328     details are given with <b>pcre_exec()</b> below.
329 nigel 73 <pre>
331     </pre>
332     The output is an integer that gives the default limit for the depth of
333     recursion when calling the internal matching function in a <b>pcre_exec()</b>
334     execution. Further details are given with <b>pcre_exec()</b> below.
335     <pre>
337 nigel 75 </pre>
338 nigel 77 The output is an integer that is set to one if internal recursion when running
339     <b>pcre_exec()</b> is implemented by recursive function calls that use the stack
340     to remember their state. This is the usual way that PCRE is compiled. The
341     output is zero if PCRE was compiled to use blocks of data on the heap instead
342     of recursive function calls. In this case, <b>pcre_stack_malloc</b> and
343     <b>pcre_stack_free</b> are called to manage memory blocks on the heap, thus
344     avoiding the use of the stack.
345 nigel 73 </P>
346 nigel 91 <br><a name="SEC7" href="#TOC1">COMPILING A PATTERN</a><br>
347 nigel 63 <P>
348     <b>pcre *pcre_compile(const char *<i>pattern</i>, int <i>options</i>,</b>
349     <b>const char **<i>errptr</i>, int *<i>erroffset</i>,</b>
350     <b>const unsigned char *<i>tableptr</i>);</b>
351 nigel 77 <b>pcre *pcre_compile2(const char *<i>pattern</i>, int <i>options</i>,</b>
352     <b>int *<i>errorcodeptr</i>,</b>
353     <b>const char **<i>errptr</i>, int *<i>erroffset</i>,</b>
354     <b>const unsigned char *<i>tableptr</i>);</b>
355 nigel 63 </P>
356     <P>
357 nigel 77 Either of the functions <b>pcre_compile()</b> or <b>pcre_compile2()</b> can be
358     called to compile a pattern into an internal form. The only difference between
359     the two interfaces is that <b>pcre_compile2()</b> has an additional argument,
360     <i>errorcodeptr</i>, via which a numerical error code can be returned.
361 nigel 63 </P>
362     <P>
363 nigel 77 The pattern is a C string terminated by a binary zero, and is passed in the
364     <i>pattern</i> argument. A pointer to a single block of memory that is obtained
365     via <b>pcre_malloc</b> is returned. This contains the compiled code and related
366     data. The <b>pcre</b> type is defined for the returned block; this is a typedef
367     for a structure whose contents are not externally defined. It is up to the
368 nigel 91 caller to free the memory (via <b>pcre_free</b>) when it is no longer required.
369 nigel 77 </P>
370     <P>
371 nigel 63 Although the compiled code of a PCRE regex is relocatable, that is, it does not
372     depend on memory location, the complete <b>pcre</b> data block is not
373 nigel 75 fully relocatable, because it may contain a copy of the <i>tableptr</i>
374     argument, which is an address (see below).
375 nigel 63 </P>
376     <P>
377     The <i>options</i> argument contains independent bits that affect the
378 nigel 75 compilation. It should be zero if no options are required. The available
379     options are described below. Some of them, in particular, those that are
380     compatible with Perl, can also be set and unset from within the pattern (see
381     the detailed description in the
382     <a href="pcrepattern.html"><b>pcrepattern</b></a>
383     documentation). For these options, the contents of the <i>options</i> argument
384     specifies their initial settings at the start of compilation and execution. The
385 nigel 91 PCRE_ANCHORED and PCRE_NEWLINE_<i>xxx</i> options can be set at the time of
386     matching as well as at compile time.
387 nigel 63 </P>
388     <P>
389     If <i>errptr</i> is NULL, <b>pcre_compile()</b> returns NULL immediately.
390     Otherwise, if compilation of a pattern fails, <b>pcre_compile()</b> returns
391     NULL, and sets the variable pointed to by <i>errptr</i> to point to a textual
392 nigel 87 error message. This is a static string that is part of the library. You must
393     not try to free it. The offset from the start of the pattern to the character
394     where the error was discovered is placed in the variable pointed to by
395 nigel 63 <i>erroffset</i>, which must not be NULL. If it is, an immediate error is given.
396     </P>
397     <P>
398 nigel 77 If <b>pcre_compile2()</b> is used instead of <b>pcre_compile()</b>, and the
399     <i>errorcodeptr</i> argument is not NULL, a non-zero error code number is
400     returned via this argument in the event of an error. This is in addition to the
401     textual error message. Error codes and messages are listed below.
402     </P>
403     <P>
404 nigel 63 If the final argument, <i>tableptr</i>, is NULL, PCRE uses a default set of
405 nigel 75 character tables that are built when PCRE is compiled, using the default C
406     locale. Otherwise, <i>tableptr</i> must be an address that is the result of a
407     call to <b>pcre_maketables()</b>. This value is stored with the compiled
408     pattern, and used again by <b>pcre_exec()</b>, unless another table pointer is
409     passed to it. For more discussion, see the section on locale support below.
410 nigel 63 </P>
411     <P>
412     This code fragment shows a typical straightforward call to <b>pcre_compile()</b>:
413     <pre>
414     pcre *re;
415     const char *error;
416     int erroffset;
417     re = pcre_compile(
418     "^A.*Z", /* the pattern */
419     0, /* default options */
420     &error, /* for error message */
421     &erroffset, /* for error offset */
422     NULL); /* use default character tables */
423 nigel 75 </pre>
424     The following names for option bits are defined in the <b>pcre.h</b> header
425     file:
426 nigel 63 <pre>
428 nigel 75 </pre>
429 nigel 63 If this bit is set, the pattern is forced to be "anchored", that is, it is
430 nigel 75 constrained to match only at the first matching point in the string that is
431 nigel 63 being searched (the "subject string"). This effect can also be achieved by
432     appropriate constructs in the pattern itself, which is the only way to do it in
433     Perl.
434     <pre>
435 nigel 75 PCRE_AUTO_CALLOUT
436     </pre>
437     If this bit is set, <b>pcre_compile()</b> automatically inserts callout items,
438     all with number 255, before each pattern item. For discussion of the callout
439     facility, see the
440     <a href="pcrecallout.html"><b>pcrecallout</b></a>
441     documentation.
442     <pre>
443 nigel 63 PCRE_CASELESS
444 nigel 75 </pre>
445 nigel 63 If this bit is set, letters in the pattern match both upper and lower case
446     letters. It is equivalent to Perl's /i option, and it can be changed within a
447 nigel 77 pattern by a (?i) option setting. In UTF-8 mode, PCRE always understands the
448     concept of case for characters whose values are less than 128, so caseless
449     matching is always possible. For characters with higher values, the concept of
450     case is supported if PCRE is compiled with Unicode property support, but not
451     otherwise. If you want to use caseless matching for characters 128 and above,
452     you must ensure that PCRE is compiled with Unicode property support as well as
453     with UTF-8 support.
454 nigel 63 <pre>
456 nigel 75 </pre>
457 nigel 63 If this bit is set, a dollar metacharacter in the pattern matches only at the
458     end of the subject string. Without this option, a dollar also matches
459 nigel 91 immediately before a newline at the end of the string (but not before any other
460     newlines). The PCRE_DOLLAR_ENDONLY option is ignored if PCRE_MULTILINE is set.
461     There is no equivalent to this option in Perl, and no way to set it within a
462     pattern.
463 nigel 63 <pre>
465 nigel 75 </pre>
466 nigel 63 If this bit is set, a dot metacharater in the pattern matches all characters,
467 nigel 91 including those that indicate newline. Without it, a dot does not match when
468     the current position is at a newline. This option is equivalent to Perl's /s
469     option, and it can be changed within a pattern by a (?s) option setting. A
470     negative class such as [^a] always matches newlines, independent of the setting
471     of this option.
472 nigel 63 <pre>
473 nigel 91 PCRE_DUPNAMES
474     </pre>
475     If this bit is set, names used to identify capturing subpatterns need not be
476     unique. This can be helpful for certain types of pattern when it is known that
477     only one instance of the named subpattern can ever be matched. There are more
478     details of named subpatterns below; see also the
479     <a href="pcrepattern.html"><b>pcrepattern</b></a>
480     documentation.
481     <pre>
482 nigel 63 PCRE_EXTENDED
483 nigel 75 </pre>
484 nigel 63 If this bit is set, whitespace data characters in the pattern are totally
485     ignored except when escaped or inside a character class. Whitespace does not
486     include the VT character (code 11). In addition, characters between an
487 nigel 91 unescaped # outside a character class and the next newline, inclusive, are also
488     ignored. This is equivalent to Perl's /x option, and it can be changed within a
489     pattern by a (?x) option setting.
490 nigel 63 </P>
491     <P>
492     This option makes it possible to include comments inside complicated patterns.
493     Note, however, that this applies only to data characters. Whitespace characters
494     may never appear within special character sequences in a pattern, for example
495     within the sequence (?( which introduces a conditional subpattern.
496     <pre>
497     PCRE_EXTRA
498 nigel 75 </pre>
499 nigel 63 This option was invented in order to turn on additional functionality of PCRE
500     that is incompatible with Perl, but it is currently of very little use. When
501     set, any backslash in a pattern that is followed by a letter that has no
502     special meaning causes an error, thus reserving these combinations for future
503     expansion. By default, as in Perl, a backslash followed by a letter with no
504 nigel 91 special meaning is treated as a literal. (Perl can, however, be persuaded to
505     give a warning for this.) There are at present no other features controlled by
506     this option. It can also be set by a (?X) option setting within a pattern.
507 nigel 63 <pre>
508 nigel 77 PCRE_FIRSTLINE
509     </pre>
510     If this option is set, an unanchored pattern is required to match before or at
511 nigel 91 the first newline in the subject string, though the matched text may continue
512     over the newline.
513 nigel 77 <pre>
514 nigel 63 PCRE_MULTILINE
515 nigel 75 </pre>
516     By default, PCRE treats the subject string as consisting of a single line of
517     characters (even if it actually contains newlines). The "start of line"
518 nigel 63 metacharacter (^) matches only at the start of the string, while the "end of
519     line" metacharacter ($) matches only at the end of the string, or before a
520     terminating newline (unless PCRE_DOLLAR_ENDONLY is set). This is the same as
521     Perl.
522     </P>
523     <P>
524     When PCRE_MULTILINE it is set, the "start of line" and "end of line" constructs
525 nigel 91 match immediately following or immediately before internal newlines in the
526     subject string, respectively, as well as at the very start and end. This is
527     equivalent to Perl's /m option, and it can be changed within a pattern by a
528     (?m) option setting. If there are no newlines in a subject string, or no
529 nigel 63 occurrences of ^ or $ in a pattern, setting PCRE_MULTILINE has no effect.
530     <pre>
531 nigel 91 PCRE_NEWLINE_CR
534     </pre>
535     These options override the default newline definition that was chosen when PCRE
536     was built. Setting the first or the second specifies that a newline is
537     indicated by a single character (CR or LF, respectively). Setting both of them
538     specifies that a newline is indicated by the two-character CRLF sequence. For
539     convenience, PCRE_NEWLINE_CRLF is defined to contain both bits. The only time
540     that a line break is relevant when compiling a pattern is if PCRE_EXTENDED is
541     set, and an unescaped # outside a character class is encountered. This
542     indicates a comment that lasts until after the next newline.
543     </P>
544     <P>
545     The newline option set at compile time becomes the default that is used for
546     <b>pcre_exec()</b> and <b>pcre_dfa_exec()</b>, but it can be overridden.
547     <pre>
549 nigel 75 </pre>
550 nigel 63 If this option is set, it disables the use of numbered capturing parentheses in
551     the pattern. Any opening parenthesis that is not followed by ? behaves as if it
552     were followed by ?: but named parentheses can still be used for capturing (and
553     they acquire numbers in the usual way). There is no equivalent of this option
554     in Perl.
555     <pre>
557 nigel 75 </pre>
558 nigel 63 This option inverts the "greediness" of the quantifiers so that they are not
559     greedy by default, but become greedy if followed by "?". It is not compatible
560     with Perl. It can also be set by a (?U) option setting within the pattern.
561     <pre>
562     PCRE_UTF8
563 nigel 75 </pre>
564 nigel 63 This option causes PCRE to regard both the pattern and the subject as strings
565     of UTF-8 characters instead of single-byte character strings. However, it is
566 nigel 75 available only when PCRE is built to include UTF-8 support. If not, the use
567 nigel 63 of this option provokes an error. Details of how this option changes the
568     behaviour of PCRE are given in the
569     <a href="pcre.html#utf8support">section on UTF-8 support</a>
570     in the main
571     <a href="pcre.html"><b>pcre</b></a>
572     page.
573 nigel 71 <pre>
575 nigel 75 </pre>
576 nigel 71 When PCRE_UTF8 is set, the validity of the pattern as a UTF-8 string is
577     automatically checked. If an invalid UTF-8 sequence of bytes is found,
578     <b>pcre_compile()</b> returns an error. If you already know that your pattern is
579     valid, and you want to skip this check for performance reasons, you can set the
580     PCRE_NO_UTF8_CHECK option. When it is set, the effect of passing an invalid
581     UTF-8 string as a pattern is undefined. It may cause your program to crash.
582 nigel 77 Note that this option can also be passed to <b>pcre_exec()</b> and
583     <b>pcre_dfa_exec()</b>, to suppress the UTF-8 validity checking of subject
584     strings.
585 nigel 71 </P>
586 nigel 91 <br><a name="SEC8" href="#TOC1">COMPILATION ERROR CODES</a><br>
587 nigel 63 <P>
588 nigel 77 The following table lists the error codes than may be returned by
589     <b>pcre_compile2()</b>, along with the error messages that may be returned by
590     both compiling functions.
591     <pre>
592     0 no error
593     1 \ at end of pattern
594     2 \c at end of pattern
595     3 unrecognized character follows \
596     4 numbers out of order in {} quantifier
597     5 number too big in {} quantifier
598     6 missing terminating ] for character class
599     7 invalid escape sequence in character class
600     8 range out of order in character class
601     9 nothing to repeat
602     10 operand of unlimited repeat could match the empty string
603     11 internal error: unexpected repeat
604     12 unrecognized character after (?
605     13 POSIX named classes are supported only within a class
606     14 missing )
607     15 reference to non-existent subpattern
608     16 erroffset passed as NULL
609     17 unknown option bit(s) set
610     18 missing ) after comment
611     19 parentheses nested too deeply
612     20 regular expression too large
613     21 failed to get memory
614     22 unmatched parentheses
615     23 internal error: code overflow
616     24 unrecognized character after (?&#60;
617     25 lookbehind assertion is not fixed length
618 nigel 91 26 malformed number or name after (?(
619 nigel 77 27 conditional group contains more than two branches
620     28 assertion expected after (?(
621     29 (?R or (?digits must be followed by )
622     30 unknown POSIX class name
623     31 POSIX collating elements are not supported
624     32 this version of PCRE is not compiled with PCRE_UTF8 support
625     33 spare error
626     34 character value in \x{...} sequence is too large
627     35 invalid condition (?(0)
628     36 \C not allowed in lookbehind assertion
629     37 PCRE does not support \L, \l, \N, \U, or \u
630     38 number after (?C is &#62; 255
631     39 closing ) for (?C expected
632     40 recursive call could loop indefinitely
633     41 unrecognized character after (?P
634     42 syntax error after (?P
635 nigel 91 43 two named subpatterns have the same name
636 nigel 77 44 invalid UTF-8 string
637     45 support for \P, \p, and \X has not been compiled
638     46 malformed \P or \p sequence
639     47 unknown property name after \P or \p
640 nigel 91 48 subpattern name is too long (maximum 32 characters)
641     49 too many named subpatterns (maximum 10,000)
642     50 repeated subpattern is too long
643     51 octal value is greater than \377 (not in UTF-8 mode)
644 nigel 77 </PRE>
645     </P>
646 nigel 91 <br><a name="SEC9" href="#TOC1">STUDYING A PATTERN</a><br>
647 nigel 77 <P>
648     <b>pcre_extra *pcre_study(const pcre *<i>code</i>, int <i>options</i></b>
649 nigel 63 <b>const char **<i>errptr</i>);</b>
650     </P>
651     <P>
652 nigel 75 If a compiled pattern is going to be used several times, it is worth spending
653     more time analyzing it in order to speed up the time taken for matching. The
654 nigel 63 function <b>pcre_study()</b> takes a pointer to a compiled pattern as its first
655 nigel 75 argument. If studying the pattern produces additional information that will
656     help speed up matching, <b>pcre_study()</b> returns a pointer to a
657     <b>pcre_extra</b> block, in which the <i>study_data</i> field points to the
658     results of the study.
659 nigel 63 </P>
660     <P>
661 nigel 75 The returned value from <b>pcre_study()</b> can be passed directly to
662     <b>pcre_exec()</b>. However, a <b>pcre_extra</b> block also contains other
663 nigel 63 fields that can be set by the caller before the block is passed; these are
664 nigel 75 described
665     <a href="#extradata">below</a>
666     in the section on matching a pattern.
667 nigel 63 </P>
668     <P>
669 nigel 77 If studying the pattern does not produce any additional information
670 nigel 75 <b>pcre_study()</b> returns NULL. In that circumstance, if the calling program
671     wants to pass any of the other fields to <b>pcre_exec()</b>, it must set up its
672     own <b>pcre_extra</b> block.
673 nigel 63 </P>
674     <P>
675 nigel 75 The second argument of <b>pcre_study()</b> contains option bits. At present, no
676     options are defined, and this argument should always be zero.
677     </P>
678     <P>
679 nigel 63 The third argument for <b>pcre_study()</b> is a pointer for an error message. If
680     studying succeeds (even if no data is returned), the variable it points to is
681 nigel 87 set to NULL. Otherwise it is set to point to a textual error message. This is a
682     static string that is part of the library. You must not try to free it. You
683     should test the error pointer for NULL after calling <b>pcre_study()</b>, to be
684     sure that it has run successfully.
685 nigel 63 </P>
686     <P>
687     This is a typical call to <b>pcre_study</b>():
688     <pre>
689     pcre_extra *pe;
690     pe = pcre_study(
691     re, /* result of pcre_compile() */
692     0, /* no options exist */
693     &error); /* set to NULL or points to a message */
694 nigel 75 </pre>
695 nigel 63 At present, studying a pattern is useful only for non-anchored patterns that do
696     not have a single fixed starting character. A bitmap of possible starting
697 nigel 75 bytes is created.
698     <a name="localesupport"></a></P>
699 nigel 91 <br><a name="SEC10" href="#TOC1">LOCALE SUPPORT</a><br>
700 nigel 63 <P>
701 nigel 77 PCRE handles caseless matching, and determines whether characters are letters
702 nigel 75 digits, or whatever, by reference to a set of tables, indexed by character
703 nigel 77 value. When running in UTF-8 mode, this applies only to characters with codes
704 nigel 75 less than 128. Higher-valued codes never match escapes such as \w or \d, but
705     can be tested with \p if PCRE is built with Unicode character property
706 nigel 87 support. The use of locales with Unicode is discouraged.
707 nigel 63 </P>
708     <P>
709 nigel 75 An internal set of tables is created in the default C locale when PCRE is
710     built. This is used when the final argument of <b>pcre_compile()</b> is NULL,
711     and is sufficient for many applications. An alternative set of tables can,
712     however, be supplied. These may be created in a different locale from the
713     default. As more and more applications change to using Unicode, the need for
714     this locale support is expected to die away.
715 nigel 63 </P>
716     <P>
717 nigel 75 External tables are built by calling the <b>pcre_maketables()</b> function,
718     which has no arguments, in the relevant locale. The result can then be passed
719     to <b>pcre_compile()</b> or <b>pcre_exec()</b> as often as necessary. For
720     example, to build and use tables that are appropriate for the French locale
721     (where accented characters with values greater than 128 are treated as letters),
722     the following code could be used:
723 nigel 63 <pre>
724 nigel 75 setlocale(LC_CTYPE, "fr_FR");
725 nigel 63 tables = pcre_maketables();
726     re = pcre_compile(..., tables);
727 nigel 75 </pre>
728     When <b>pcre_maketables()</b> runs, the tables are built in memory that is
729     obtained via <b>pcre_malloc</b>. It is the caller's responsibility to ensure
730     that the memory containing the tables remains available for as long as it is
731     needed.
732 nigel 63 </P>
733     <P>
734 nigel 75 The pointer that is passed to <b>pcre_compile()</b> is saved with the compiled
735 nigel 63 pattern, and the same tables are used via this pointer by <b>pcre_study()</b>
736 nigel 75 and normally also by <b>pcre_exec()</b>. Thus, by default, for any single
737     pattern, compilation, studying and matching all happen in the same locale, but
738     different patterns can be compiled in different locales.
739 nigel 63 </P>
740     <P>
741 nigel 75 It is possible to pass a table pointer or NULL (indicating the use of the
742     internal tables) to <b>pcre_exec()</b>. Although not intended for this purpose,
743     this facility could be used to match a pattern in a different locale from the
744     one in which it was compiled. Passing table pointers at run time is discussed
745     below in the section on matching a pattern.
746     </P>
747 nigel 91 <br><a name="SEC11" href="#TOC1">INFORMATION ABOUT A PATTERN</a><br>
748 nigel 75 <P>
749 nigel 63 <b>int pcre_fullinfo(const pcre *<i>code</i>, const pcre_extra *<i>extra</i>,</b>
750     <b>int <i>what</i>, void *<i>where</i>);</b>
751     </P>
752     <P>
753     The <b>pcre_fullinfo()</b> function returns information about a compiled
754     pattern. It replaces the obsolete <b>pcre_info()</b> function, which is
755     nevertheless retained for backwards compability (and is documented below).
756     </P>
757     <P>
758     The first argument for <b>pcre_fullinfo()</b> is a pointer to the compiled
759     pattern. The second argument is the result of <b>pcre_study()</b>, or NULL if
760     the pattern was not studied. The third argument specifies which piece of
761     information is required, and the fourth argument is a pointer to a variable
762     to receive the data. The yield of the function is zero for success, or one of
763     the following negative numbers:
764     <pre>
765     PCRE_ERROR_NULL the argument <i>code</i> was NULL
766     the argument <i>where</i> was NULL
767     PCRE_ERROR_BADMAGIC the "magic number" was not found
768     PCRE_ERROR_BADOPTION the value of <i>what</i> was invalid
769 nigel 75 </pre>
770     The "magic number" is placed at the start of each compiled pattern as an simple
771     check against passing an arbitrary memory pointer. Here is a typical call of
772     <b>pcre_fullinfo()</b>, to obtain the length of the compiled pattern:
773 nigel 63 <pre>
774     int rc;
775 nigel 91 size_t length;
776 nigel 63 rc = pcre_fullinfo(
777     re, /* result of pcre_compile() */
778     pe, /* result of pcre_study(), or NULL */
779     PCRE_INFO_SIZE, /* what is required */
780     &length); /* where to put the data */
781 nigel 75 </pre>
782 nigel 63 The possible values for the third argument are defined in <b>pcre.h</b>, and are
783     as follows:
784     <pre>
786 nigel 75 </pre>
787 nigel 63 Return the number of the highest back reference in the pattern. The fourth
788     argument should point to an <b>int</b> variable. Zero is returned if there are
789     no back references.
790     <pre>
792 nigel 75 </pre>
793 nigel 63 Return the number of capturing subpatterns in the pattern. The fourth argument
794 nigel 75 should point to an <b>int</b> variable.
795 nigel 63 <pre>
797 nigel 75 </pre>
798     Return a pointer to the internal default character tables within PCRE. The
799     fourth argument should point to an <b>unsigned char *</b> variable. This
800     information call is provided for internal use by the <b>pcre_study()</b>
801     function. External callers can cause PCRE to use its internal tables by passing
802     a NULL table pointer.
803     <pre>
805 nigel 75 </pre>
806 nigel 63 Return information about the first byte of any matched string, for a
807 nigel 91 non-anchored pattern. The fourth argument should point to an <b>int</b>
808     variable. (This option used to be called PCRE_INFO_FIRSTCHAR; the old name is
809     still recognized for backwards compatibility.)
810 nigel 63 </P>
811     <P>
812 nigel 75 If there is a fixed first byte, for example, from a pattern such as
813 nigel 91 (cat|cow|coyote). Otherwise, if either
814 nigel 75 <br>
815     <br>
816 nigel 63 (a) the pattern was compiled with the PCRE_MULTILINE option, and every branch
817     starts with "^", or
818 nigel 75 <br>
819     <br>
820 nigel 63 (b) every branch of the pattern starts with ".*" and PCRE_DOTALL is not set
821     (if it were set, the pattern would be anchored),
822 nigel 75 <br>
823     <br>
824 nigel 63 -1 is returned, indicating that the pattern matches only at the start of a
825     subject string or after any newline within the string. Otherwise -2 is
826     returned. For anchored patterns, -2 is returned.
827     <pre>
829 nigel 75 </pre>
830 nigel 63 If the pattern was studied, and this resulted in the construction of a 256-bit
831     table indicating a fixed set of bytes for the first byte in any matching
832     string, a pointer to the table is returned. Otherwise NULL is returned. The
833     fourth argument should point to an <b>unsigned char *</b> variable.
834     <pre>
836 nigel 75 </pre>
837 nigel 65 Return the value of the rightmost literal byte that must exist in any matched
838     string, other than at its start, if such a byte has been recorded. The fourth
839     argument should point to an <b>int</b> variable. If there is no such byte, -1 is
840     returned. For anchored patterns, a last literal byte is recorded only if it
841     follows something of variable length. For example, for the pattern
842     /^a\d+z\d+/ the returned value is "z", but for /^a\dz\d/ the returned value
843     is -1.
844 nigel 63 <pre>
848 nigel 75 </pre>
849 nigel 63 PCRE supports the use of named as well as numbered capturing parentheses. The
850     names are just an additional way of identifying the parentheses, which still
851 nigel 91 acquire numbers. Several convenience functions such as
852     <b>pcre_get_named_substring()</b> are provided for extracting captured
853     substrings by name. It is also possible to extract the data directly, by first
854     converting the name to a number in order to access the correct pointers in the
855     output vector (described with <b>pcre_exec()</b> below). To do the conversion,
856     you need to use the name-to-number map, which is described by these three
857     values.
858 nigel 63 </P>
859     <P>
860     The map consists of a number of fixed-size entries. PCRE_INFO_NAMECOUNT gives
861     the number of entries, and PCRE_INFO_NAMEENTRYSIZE gives the size of each
862     entry; both of these return an <b>int</b> value. The entry size depends on the
863     length of the longest name. PCRE_INFO_NAMETABLE returns a pointer to the first
864     entry of the table (a pointer to <b>char</b>). The first two bytes of each entry
865     are the number of the capturing parenthesis, most significant byte first. The
866     rest of the entry is the corresponding name, zero terminated. The names are in
867 nigel 91 alphabetical order. When PCRE_DUPNAMES is set, duplicate names are in order of
868     their parentheses numbers. For example, consider the following pattern (assume
869 nigel 63 PCRE_EXTENDED is set, so white space - including newlines - is ignored):
870     <pre>
871 nigel 75 (?P&#60;date&#62; (?P&#60;year&#62;(\d\d)?\d\d) - (?P&#60;month&#62;\d\d) - (?P&#60;day&#62;\d\d) )
872     </pre>
873 nigel 63 There are four named subpatterns, so the table has four entries, and each entry
874     in the table is eight bytes long. The table is as follows, with non-printing
875 nigel 75 bytes shows in hexadecimal, and undefined bytes shown as ??:
876 nigel 63 <pre>
877     00 01 d a t e 00 ??
878     00 05 d a y 00 ?? ??
879     00 04 m o n t h 00
880     00 02 y e a r 00 ??
881 nigel 75 </pre>
882     When writing code to extract data from named subpatterns using the
883 nigel 91 name-to-number map, remember that the length of the entries is likely to be
884 nigel 75 different for each compiled pattern.
885 nigel 63 <pre>
887 nigel 75 </pre>
888 nigel 63 Return a copy of the options with which the pattern was compiled. The fourth
889     argument should point to an <b>unsigned long int</b> variable. These option bits
890     are those specified in the call to <b>pcre_compile()</b>, modified by any
891     top-level option settings within the pattern itself.
892     </P>
893     <P>
894     A pattern is automatically anchored by PCRE if all of its top-level
895     alternatives begin with one of the following:
896     <pre>
897     ^ unless PCRE_MULTILINE is set
898     \A always
899     \G always
900 nigel 75 .* if PCRE_DOTALL is set and there are no back references to the subpattern in which .* appears
901     </pre>
902 nigel 63 For such patterns, the PCRE_ANCHORED bit is set in the options returned by
903     <b>pcre_fullinfo()</b>.
904     <pre>
906 nigel 75 </pre>
907 nigel 63 Return the size of the compiled pattern, that is, the value that was passed as
908     the argument to <b>pcre_malloc()</b> when PCRE was getting memory in which to
909     place the compiled data. The fourth argument should point to a <b>size_t</b>
910     variable.
911     <pre>
913 nigel 75 </pre>
914     Return the size of the data block pointed to by the <i>study_data</i> field in
915 nigel 63 a <b>pcre_extra</b> block. That is, it is the value that was passed to
916     <b>pcre_malloc()</b> when PCRE was getting memory into which to place the data
917     created by <b>pcre_study()</b>. The fourth argument should point to a
918     <b>size_t</b> variable.
919     </P>
920 nigel 91 <br><a name="SEC12" href="#TOC1">OBSOLETE INFO FUNCTION</a><br>
921 nigel 63 <P>
922     <b>int pcre_info(const pcre *<i>code</i>, int *<i>optptr</i>, int</b>
923     <b>*<i>firstcharptr</i>);</b>
924     </P>
925     <P>
926     The <b>pcre_info()</b> function is now obsolete because its interface is too
927     restrictive to return all the available data about a compiled pattern. New
928     programs should use <b>pcre_fullinfo()</b> instead. The yield of
929     <b>pcre_info()</b> is the number of capturing subpatterns, or one of the
930     following negative numbers:
931     <pre>
932     PCRE_ERROR_NULL the argument <i>code</i> was NULL
933     PCRE_ERROR_BADMAGIC the "magic number" was not found
934 nigel 75 </pre>
935 nigel 63 If the <i>optptr</i> argument is not NULL, a copy of the options with which the
936     pattern was compiled is placed in the integer it points to (see
937     PCRE_INFO_OPTIONS above).
938     </P>
939     <P>
940     If the pattern is not anchored and the <i>firstcharptr</i> argument is not NULL,
941     it is used to pass back information about the first character of any matched
942     string (see PCRE_INFO_FIRSTBYTE above).
943     </P>
944 nigel 91 <br><a name="SEC13" href="#TOC1">REFERENCE COUNTS</a><br>
945 nigel 63 <P>
946 nigel 77 <b>int pcre_refcount(pcre *<i>code</i>, int <i>adjust</i>);</b>
947     </P>
948     <P>
949     The <b>pcre_refcount()</b> function is used to maintain a reference count in the
950     data block that contains a compiled pattern. It is provided for the benefit of
951     applications that operate in an object-oriented manner, where different parts
952     of the application may be using the same compiled pattern, but you want to free
953     the block when they are all done.
954     </P>
955     <P>
956     When a pattern is compiled, the reference count field is initialized to zero.
957     It is changed only by calling this function, whose action is to add the
958     <i>adjust</i> value (which may be positive or negative) to it. The yield of the
959     function is the new value. However, the value of the count is constrained to
960     lie between 0 and 65535, inclusive. If the new value is outside these limits,
961     it is forced to the appropriate limit value.
962     </P>
963     <P>
964     Except when it is zero, the reference count is not correctly preserved if a
965     pattern is compiled on one host and then transferred to a host whose byte-order
966     is different. (This seems a highly unlikely scenario.)
967     </P>
968 nigel 91 <br><a name="SEC14" href="#TOC1">MATCHING A PATTERN: THE TRADITIONAL FUNCTION</a><br>
969 nigel 77 <P>
970 nigel 63 <b>int pcre_exec(const pcre *<i>code</i>, const pcre_extra *<i>extra</i>,</b>
971     <b>const char *<i>subject</i>, int <i>length</i>, int <i>startoffset</i>,</b>
972     <b>int <i>options</i>, int *<i>ovector</i>, int <i>ovecsize</i>);</b>
973     </P>
974     <P>
975     The function <b>pcre_exec()</b> is called to match a subject string against a
976 nigel 75 compiled pattern, which is passed in the <i>code</i> argument. If the
977 nigel 63 pattern has been studied, the result of the study should be passed in the
978 nigel 77 <i>extra</i> argument. This function is the main matching facility of the
979     library, and it operates in a Perl-like manner. For specialist use there is
980     also an alternative matching function, which is described
981     <a href="#dfamatch">below</a>
982     in the section about the <b>pcre_dfa_exec()</b> function.
983 nigel 63 </P>
984     <P>
985 nigel 75 In most applications, the pattern will have been compiled (and optionally
986     studied) in the same process that calls <b>pcre_exec()</b>. However, it is
987     possible to save compiled patterns and study data, and then use them later
988     in different processes, possibly even on different hosts. For a discussion
989     about this, see the
990     <a href="pcreprecompile.html"><b>pcreprecompile</b></a>
991     documentation.
992 nigel 63 </P>
993     <P>
994 nigel 75 Here is an example of a simple call to <b>pcre_exec()</b>:
995 nigel 63 <pre>
996     int rc;
997     int ovector[30];
998     rc = pcre_exec(
999     re, /* result of pcre_compile() */
1000     NULL, /* we didn't study the pattern */
1001     "some string", /* the subject string */
1002     11, /* the length of the subject string */
1003     0, /* start at offset 0 in the subject */
1004     0, /* default options */
1005 nigel 75 ovector, /* vector of integers for substring information */
1006 nigel 77 30); /* number of elements (NOT size in bytes) */
1007 nigel 75 <a name="extradata"></a></PRE>
1008 nigel 63 </P>
1009 nigel 75 <br><b>
1010     Extra data for <b>pcre_exec()</b>
1011     </b><br>
1012 nigel 63 <P>
1013     If the <i>extra</i> argument is not NULL, it must point to a <b>pcre_extra</b>
1014     data block. The <b>pcre_study()</b> function returns such a block (when it
1015     doesn't return NULL), but you can also create one for yourself, and pass
1016 nigel 87 additional information in it. The <b>pcre_extra</b> block contains the following
1017     fields (not necessarily in this order):
1018 nigel 63 <pre>
1019     unsigned long int <i>flags</i>;
1020     void *<i>study_data</i>;
1021     unsigned long int <i>match_limit</i>;
1022 nigel 87 unsigned long int <i>match_limit_recursion</i>;
1023 nigel 63 void *<i>callout_data</i>;
1024 nigel 75 const unsigned char *<i>tables</i>;
1025     </pre>
1026 nigel 63 The <i>flags</i> field is a bitmap that specifies which of the other fields
1027     are set. The flag bits are:
1028     <pre>
1033 nigel 75 PCRE_EXTRA_TABLES
1034     </pre>
1035 nigel 63 Other flag bits should be set to zero. The <i>study_data</i> field is set in the
1036     <b>pcre_extra</b> block that is returned by <b>pcre_study()</b>, together with
1037 nigel 75 the appropriate flag bit. You should not set this yourself, but you may add to
1038     the block by setting the other fields and their corresponding flag bits.
1039 nigel 63 </P>
1040     <P>
1041     The <i>match_limit</i> field provides a means of preventing PCRE from using up a
1042     vast amount of resources when running patterns that are not going to match,
1043     but which have a very large number of possibilities in their search trees. The
1044 nigel 75 classic example is the use of nested unlimited repeats.
1045 nigel 63 </P>
1046     <P>
1047 nigel 75 Internally, PCRE uses a function called <b>match()</b> which it calls repeatedly
1048 nigel 87 (sometimes recursively). The limit set by <i>match_limit</i> is imposed on the
1049     number of times this function is called during a match, which has the effect of
1050     limiting the amount of backtracking that can take place. For patterns that are
1051     not anchored, the count restarts from zero for each position in the subject
1052     string.
1053 nigel 75 </P>
1054     <P>
1055 nigel 87 The default value for the limit can be set when PCRE is built; the default
1056 nigel 63 default is 10 million, which handles all but the most extreme cases. You can
1057 nigel 87 override the default by suppling <b>pcre_exec()</b> with a <b>pcre_extra</b>
1058     block in which <i>match_limit</i> is set, and PCRE_EXTRA_MATCH_LIMIT is set in
1059     the <i>flags</i> field. If the limit is exceeded, <b>pcre_exec()</b> returns
1061 nigel 63 </P>
1062     <P>
1063 nigel 87 The <i>match_limit_recursion</i> field is similar to <i>match_limit</i>, but
1064     instead of limiting the total number of times that <b>match()</b> is called, it
1065     limits the depth of recursion. The recursion depth is a smaller number than the
1066     total number of calls, because not all calls to <b>match()</b> are recursive.
1067     This limit is of use only if it is set smaller than <i>match_limit</i>.
1068     </P>
1069     <P>
1070     Limiting the recursion depth limits the amount of stack that can be used, or,
1071     when PCRE has been compiled to use memory on the heap instead of the stack, the
1072     amount of heap memory that can be used.
1073     </P>
1074     <P>
1075     The default value for <i>match_limit_recursion</i> can be set when PCRE is
1076     built; the default default is the same value as the default for
1077     <i>match_limit</i>. You can override the default by suppling <b>pcre_exec()</b>
1078     with a <b>pcre_extra</b> block in which <i>match_limit_recursion</i> is set, and
1079     PCRE_EXTRA_MATCH_LIMIT_RECURSION is set in the <i>flags</i> field. If the limit
1080     is exceeded, <b>pcre_exec()</b> returns PCRE_ERROR_RECURSIONLIMIT.
1081     </P>
1082     <P>
1083 nigel 63 The <i>pcre_callout</i> field is used in conjunction with the "callout" feature,
1084 nigel 75 which is described in the
1085     <a href="pcrecallout.html"><b>pcrecallout</b></a>
1086     documentation.
1087 nigel 63 </P>
1088     <P>
1089 nigel 75 The <i>tables</i> field is used to pass a character tables pointer to
1090     <b>pcre_exec()</b>; this overrides the value that is stored with the compiled
1091     pattern. A non-NULL value is stored with the compiled pattern only if custom
1092     tables were supplied to <b>pcre_compile()</b> via its <i>tableptr</i> argument.
1093     If NULL is passed to <b>pcre_exec()</b> using this mechanism, it forces PCRE's
1094     internal tables to be used. This facility is helpful when re-using patterns
1095     that have been saved after compiling with an external set of tables, because
1096     the external tables might be at a different address when <b>pcre_exec()</b> is
1097     called. See the
1098     <a href="pcreprecompile.html"><b>pcreprecompile</b></a>
1099     documentation for a discussion of saving compiled patterns for later use.
1100 nigel 63 </P>
1101 nigel 75 <br><b>
1102     Option bits for <b>pcre_exec()</b>
1103     </b><br>
1104 nigel 63 <P>
1105 nigel 75 The unused bits of the <i>options</i> argument for <b>pcre_exec()</b> must be
1106 nigel 91 zero. The only bits that may be set are PCRE_ANCHORED, PCRE_NEWLINE_<i>xxx</i>,
1108 nigel 63 <pre>
1109 nigel 75 PCRE_ANCHORED
1110     </pre>
1111     The PCRE_ANCHORED option limits <b>pcre_exec()</b> to matching at the first
1112     matching position. If a pattern was compiled with PCRE_ANCHORED, or turned out
1113     to be anchored by virtue of its contents, it cannot be made unachored at
1114     matching time.
1115     <pre>
1116 nigel 91 PCRE_NEWLINE_CR
1119     </pre>
1120     These options override the newline definition that was chosen or defaulted when
1121     the pattern was compiled. For details, see the description <b>pcre_compile()</b>
1122     above. During matching, the newline choice affects the behaviour of the dot,
1123     circumflex, and dollar metacharacters.
1124     <pre>
1125 nigel 63 PCRE_NOTBOL
1126 nigel 75 </pre>
1127     This option specifies that first character of the subject string is not the
1128     beginning of a line, so the circumflex metacharacter should not match before
1129     it. Setting this without PCRE_MULTILINE (at compile time) causes circumflex
1130     never to match. This option affects only the behaviour of the circumflex
1131     metacharacter. It does not affect \A.
1132 nigel 63 <pre>
1133     PCRE_NOTEOL
1134 nigel 75 </pre>
1135     This option specifies that the end of the subject string is not the end of a
1136     line, so the dollar metacharacter should not match it nor (except in multiline
1137     mode) a newline immediately before it. Setting this without PCRE_MULTILINE (at
1138     compile time) causes dollar never to match. This option affects only the
1139     behaviour of the dollar metacharacter. It does not affect \Z or \z.
1140 nigel 63 <pre>
1142 nigel 75 </pre>
1143 nigel 63 An empty string is not considered to be a valid match if this option is set. If
1144     there are alternatives in the pattern, they are tried. If all the alternatives
1145     match the empty string, the entire match fails. For example, if the pattern
1146     <pre>
1147     a?b?
1148 nigel 75 </pre>
1149 nigel 63 is applied to a string not beginning with "a" or "b", it matches the empty
1150     string at the start of the subject. With PCRE_NOTEMPTY set, this match is not
1151     valid, so PCRE searches further into the string for occurrences of "a" or "b".
1152     </P>
1153     <P>
1154     Perl has no direct equivalent of PCRE_NOTEMPTY, but it does make a special case
1155     of a pattern match of the empty string within its <b>split()</b> function, and
1156     when using the /g modifier. It is possible to emulate Perl's behaviour after
1157     matching a null string by first trying the match again at the same offset with
1158 nigel 75 PCRE_NOTEMPTY and PCRE_ANCHORED, and then if that fails by advancing the
1159     starting offset (see below) and trying an ordinary match again. There is some
1160     code that demonstrates how to do this in the <i>pcredemo.c</i> sample program.
1161     <pre>
1163     </pre>
1164     When PCRE_UTF8 is set at compile time, the validity of the subject as a UTF-8
1165     string is automatically checked when <b>pcre_exec()</b> is subsequently called.
1166     The value of <i>startoffset</i> is also checked to ensure that it points to the
1167     start of a UTF-8 character. If an invalid UTF-8 sequence of bytes is found,
1168     <b>pcre_exec()</b> returns the error PCRE_ERROR_BADUTF8. If <i>startoffset</i>
1169     contains an invalid value, PCRE_ERROR_BADUTF8_OFFSET is returned.
1170 nigel 63 </P>
1171     <P>
1172 nigel 75 If you already know that your subject is valid, and you want to skip these
1173     checks for performance reasons, you can set the PCRE_NO_UTF8_CHECK option when
1174     calling <b>pcre_exec()</b>. You might want to do this for the second and
1175     subsequent calls to <b>pcre_exec()</b> if you are making repeated calls to find
1176     all the matches in a single subject string. However, you should be sure that
1177     the value of <i>startoffset</i> points to the start of a UTF-8 character. When
1178     PCRE_NO_UTF8_CHECK is set, the effect of passing an invalid UTF-8 string as a
1179     subject, or a value of <i>startoffset</i> that does not point to the start of a
1180     UTF-8 character, is undefined. Your program may crash.
1181     <pre>
1183     </pre>
1184     This option turns on the partial matching feature. If the subject string fails
1185     to match the pattern, but at some point during the matching process the end of
1186     the subject was reached (that is, the subject partially matches the pattern and
1187     the failure to match occurred only because there were not enough subject
1188     characters), <b>pcre_exec()</b> returns PCRE_ERROR_PARTIAL instead of
1189     PCRE_ERROR_NOMATCH. When PCRE_PARTIAL is used, there are restrictions on what
1190     may appear in the pattern. These are discussed in the
1191     <a href="pcrepartial.html"><b>pcrepartial</b></a>
1192     documentation.
1193     </P>
1194     <br><b>
1195     The string to be matched by <b>pcre_exec()</b>
1196     </b><br>
1197     <P>
1198 nigel 63 The subject string is passed to <b>pcre_exec()</b> as a pointer in
1199 nigel 73 <i>subject</i>, a length in <i>length</i>, and a starting byte offset in
1200 nigel 75 <i>startoffset</i>. In UTF-8 mode, the byte offset must point to the start of a
1201     UTF-8 character. Unlike the pattern string, the subject may contain binary zero
1202     bytes. When the starting offset is zero, the search for a match starts at the
1203     beginning of the subject, and this is by far the most common case.
1204 nigel 63 </P>
1205     <P>
1206     A non-zero starting offset is useful when searching for another match in the
1207     same subject by calling <b>pcre_exec()</b> again after a previous success.
1208     Setting <i>startoffset</i> differs from just passing over a shortened string and
1209     setting PCRE_NOTBOL in the case of a pattern that begins with any kind of
1210     lookbehind. For example, consider the pattern
1211     <pre>
1212     \Biss\B
1213 nigel 75 </pre>
1214 nigel 63 which finds occurrences of "iss" in the middle of words. (\B matches only if
1215     the current position in the subject is not a word boundary.) When applied to
1216     the string "Mississipi" the first call to <b>pcre_exec()</b> finds the first
1217     occurrence. If <b>pcre_exec()</b> is called again with just the remainder of the
1218     subject, namely "issipi", it does not match, because \B is always false at the
1219     start of the subject, which is deemed to be a word boundary. However, if
1220     <b>pcre_exec()</b> is passed the entire string again, but with <i>startoffset</i>
1221     set to 4, it finds the second occurrence of "iss" because it is able to look
1222     behind the starting point to discover that it is preceded by a letter.
1223     </P>
1224     <P>
1225     If a non-zero starting offset is passed when the pattern is anchored, one
1226 nigel 75 attempt to match at the given offset is made. This can only succeed if the
1227 nigel 63 pattern does not require the match to be at the start of the subject.
1228     </P>
1229 nigel 75 <br><b>
1230     How <b>pcre_exec()</b> returns captured substrings
1231     </b><br>
1232 nigel 63 <P>
1233     In general, a pattern matches a certain portion of the subject, and in
1234     addition, further substrings from the subject may be picked out by parts of the
1235     pattern. Following the usage in Jeffrey Friedl's book, this is called
1236     "capturing" in what follows, and the phrase "capturing subpattern" is used for
1237     a fragment of a pattern that picks out a substring. PCRE supports several other
1238     kinds of parenthesized subpattern that do not cause substrings to be captured.
1239     </P>
1240     <P>
1241     Captured substrings are returned to the caller via a vector of integer offsets
1242     whose address is passed in <i>ovector</i>. The number of elements in the vector
1243 nigel 75 is passed in <i>ovecsize</i>, which must be a non-negative number. <b>Note</b>:
1244     this argument is NOT the size of <i>ovector</i> in bytes.
1245 nigel 63 </P>
1246     <P>
1247 nigel 75 The first two-thirds of the vector is used to pass back captured substrings,
1248     each substring using a pair of integers. The remaining third of the vector is
1249     used as workspace by <b>pcre_exec()</b> while matching capturing subpatterns,
1250     and is not available for passing back information. The length passed in
1251     <i>ovecsize</i> should always be a multiple of three. If it is not, it is
1252     rounded down.
1253     </P>
1254     <P>
1255     When a match is successful, information about captured substrings is returned
1256     in pairs of integers, starting at the beginning of <i>ovector</i>, and
1257 nigel 63 continuing up to two-thirds of its length at the most. The first element of a
1258     pair is set to the offset of the first character in a substring, and the second
1259     is set to the offset of the first character after the end of a substring. The
1260     first pair, <i>ovector[0]</i> and <i>ovector[1]</i>, identify the portion of the
1261     subject string matched by the entire pattern. The next pair is used for the
1262     first capturing subpattern, and so on. The value returned by <b>pcre_exec()</b>
1263 nigel 91 is one more than the highest numbered pair that has been set. For example, if
1264     two substrings have been captured, the returned value is 3. If there are no
1265     capturing subpatterns, the return value from a successful match is 1,
1266     indicating that just the first pair of offsets has been set.
1267 nigel 63 </P>
1268     <P>
1269     If a capturing subpattern is matched repeatedly, it is the last portion of the
1270 nigel 75 string that it matched that is returned.
1271 nigel 63 </P>
1272     <P>
1273 nigel 75 If the vector is too small to hold all the captured substring offsets, it is
1274     used as far as possible (up to two-thirds of its length), and the function
1275     returns a value of zero. In particular, if the substring offsets are not of
1276     interest, <b>pcre_exec()</b> may be called with <i>ovector</i> passed as NULL and
1277 nigel 63 <i>ovecsize</i> as zero. However, if the pattern contains back references and
1278 nigel 75 the <i>ovector</i> is not big enough to remember the related substrings, PCRE
1279     has to get additional memory for use during matching. Thus it is usually
1280     advisable to supply an <i>ovector</i>.
1281 nigel 63 </P>
1282     <P>
1283 nigel 91 The <b>pcre_info()</b> function can be used to find out how many capturing
1284 nigel 63 subpatterns there are in a compiled pattern. The smallest size for
1285     <i>ovector</i> that will allow for <i>n</i> captured substrings, in addition to
1286     the offsets of the substring matched by the whole pattern, is (<i>n</i>+1)*3.
1287 nigel 91 </P>
1288     <P>
1289     It is possible for capturing subpattern number <i>n+1</i> to match some part of
1290     the subject when subpattern <i>n</i> has not been used at all. For example, if
1291     the string "abc" is matched against the pattern (a|(z))(bc) the return from the
1292     function is 4, and subpatterns 1 and 3 are matched, but 2 is not. When this
1293     happens, both values in the offset pairs corresponding to unused subpatterns
1294     are set to -1.
1295     </P>
1296     <P>
1297     Offset values that correspond to unused subpatterns at the end of the
1298     expression are also set to -1. For example, if the string "abc" is matched
1299     against the pattern (abc)(x(yz)?)? subpatterns 2 and 3 are not matched. The
1300     return from the function is 2, because the highest used capturing subpattern
1301     number is 1. However, you can refer to the offsets for the second and third
1302     capturing subpatterns if you wish (assuming the vector is large enough, of
1303     course).
1304     </P>
1305     <P>
1306     Some convenience functions are provided for extracting the captured substrings
1307     as separate strings. These are described below.
1308 nigel 77 <a name="errorlist"></a></P>
1309 nigel 75 <br><b>
1310 nigel 91 Error return values from <b>pcre_exec()</b>
1311 nigel 75 </b><br>
1312 nigel 63 <P>
1313     If <b>pcre_exec()</b> fails, it returns a negative number. The following are
1314     defined in the header file:
1315     <pre>
1316     PCRE_ERROR_NOMATCH (-1)
1317 nigel 75 </pre>
1318 nigel 63 The subject string did not match the pattern.
1319     <pre>
1320     PCRE_ERROR_NULL (-2)
1321 nigel 75 </pre>
1322 nigel 63 Either <i>code</i> or <i>subject</i> was passed as NULL, or <i>ovector</i> was
1323     NULL and <i>ovecsize</i> was not zero.
1324     <pre>
1326 nigel 75 </pre>
1327 nigel 63 An unrecognized bit was set in the <i>options</i> argument.
1328     <pre>
1330 nigel 75 </pre>
1331 nigel 63 PCRE stores a 4-byte "magic number" at the start of the compiled code, to catch
1332 nigel 75 the case when it is passed a junk pointer and to detect when a pattern that was
1333     compiled in an environment of one endianness is run in an environment with the
1334     other endianness. This is the error that PCRE gives when the magic number is
1335     not present.
1336 nigel 63 <pre>
1338 nigel 75 </pre>
1339 nigel 63 While running the pattern match, an unknown item was encountered in the
1340     compiled pattern. This error could be caused by a bug in PCRE or by overwriting
1341     of the compiled pattern.
1342     <pre>
1344 nigel 75 </pre>
1345 nigel 63 If a pattern contains back references, but the <i>ovector</i> that is passed to
1346     <b>pcre_exec()</b> is not big enough to remember the referenced substrings, PCRE
1347     gets a block of memory at the start of matching to use for this purpose. If the
1348 nigel 75 call via <b>pcre_malloc()</b> fails, this error is given. The memory is
1349     automatically freed at the end of matching.
1350 nigel 63 <pre>
1352 nigel 75 </pre>
1353 nigel 63 This error is used by the <b>pcre_copy_substring()</b>,
1354     <b>pcre_get_substring()</b>, and <b>pcre_get_substring_list()</b> functions (see
1355     below). It is never returned by <b>pcre_exec()</b>.
1356     <pre>
1358 nigel 75 </pre>
1359 nigel 87 The backtracking limit, as specified by the <i>match_limit</i> field in a
1360     <b>pcre_extra</b> structure (or defaulted) was reached. See the description
1361     above.
1362     <pre>
1364     </pre>
1365     The internal recursion limit, as specified by the <i>match_limit_recursion</i>
1366 nigel 63 field in a <b>pcre_extra</b> structure (or defaulted) was reached. See the
1367     description above.
1368     <pre>
1369     PCRE_ERROR_CALLOUT (-9)
1370 nigel 75 </pre>
1371 nigel 63 This error is never generated by <b>pcre_exec()</b> itself. It is provided for
1372     use by callout functions that want to yield a distinctive error code. See the
1373 nigel 75 <a href="pcrecallout.html"><b>pcrecallout</b></a>
1374     documentation for details.
1375 nigel 71 <pre>
1376 nigel 73 PCRE_ERROR_BADUTF8 (-10)
1377 nigel 75 </pre>
1378 nigel 71 A string that contains an invalid UTF-8 byte sequence was passed as a subject.
1379 nigel 73 <pre>
1381 nigel 75 </pre>
1382 nigel 73 The UTF-8 byte sequence that was passed as a subject was valid, but the value
1383     of <i>startoffset</i> did not point to the beginning of a UTF-8 character.
1384 nigel 75 <pre>
1385 nigel 77 PCRE_ERROR_PARTIAL (-12)
1386 nigel 75 </pre>
1387     The subject string did not match, but it did match partially. See the
1388     <a href="pcrepartial.html"><b>pcrepartial</b></a>
1389     documentation for details of partial matching.
1390     <pre>
1391 nigel 77 PCRE_ERROR_BADPARTIAL (-13)
1392 nigel 75 </pre>
1393     The PCRE_PARTIAL option was used with a compiled pattern containing items that
1394     are not supported for partial matching. See the
1395     <a href="pcrepartial.html"><b>pcrepartial</b></a>
1396     documentation for details of partial matching.
1397     <pre>
1398 nigel 77 PCRE_ERROR_INTERNAL (-14)
1399 nigel 75 </pre>
1400     An unexpected internal error has occurred. This error could be caused by a bug
1401     in PCRE or by overwriting of the compiled pattern.
1402     <pre>
1403 nigel 77 PCRE_ERROR_BADCOUNT (-15)
1404 nigel 75 </pre>
1405     This error is given if the value of the <i>ovecsize</i> argument is negative.
1406 nigel 73 </P>
1407 nigel 91 <br><a name="SEC15" href="#TOC1">EXTRACTING CAPTURED SUBSTRINGS BY NUMBER</a><br>
1408 nigel 63 <P>
1409     <b>int pcre_copy_substring(const char *<i>subject</i>, int *<i>ovector</i>,</b>
1410     <b>int <i>stringcount</i>, int <i>stringnumber</i>, char *<i>buffer</i>,</b>
1411     <b>int <i>buffersize</i>);</b>
1412     </P>
1413     <P>
1414     <b>int pcre_get_substring(const char *<i>subject</i>, int *<i>ovector</i>,</b>
1415     <b>int <i>stringcount</i>, int <i>stringnumber</i>,</b>
1416     <b>const char **<i>stringptr</i>);</b>
1417     </P>
1418     <P>
1419     <b>int pcre_get_substring_list(const char *<i>subject</i>,</b>
1420     <b>int *<i>ovector</i>, int <i>stringcount</i>, const char ***<i>listptr</i>);</b>
1421     </P>
1422     <P>
1423     Captured substrings can be accessed directly by using the offsets returned by
1424     <b>pcre_exec()</b> in <i>ovector</i>. For convenience, the functions
1425     <b>pcre_copy_substring()</b>, <b>pcre_get_substring()</b>, and
1426     <b>pcre_get_substring_list()</b> are provided for extracting captured substrings
1427     as new, separate, zero-terminated strings. These functions identify substrings
1428     by number. The next section describes functions for extracting named
1429 nigel 91 substrings.
1430 nigel 63 </P>
1431     <P>
1432 nigel 91 A substring that contains a binary zero is correctly extracted and has a
1433     further zero added on the end, but the result is not, of course, a C string.
1434     However, you can process such a string by referring to the length that is
1435     returned by <b>pcre_copy_substring()</b> and <b>pcre_get_substring()</b>.
1436     Unfortunately, the interface to <b>pcre_get_substring_list()</b> is not adequate
1437     for handling strings containing binary zeros, because the end of the final
1438     string is not independently indicated.
1439     </P>
1440     <P>
1441 nigel 63 The first three arguments are the same for all three of these functions:
1442 nigel 75 <i>subject</i> is the subject string that has just been successfully matched,
1443 nigel 63 <i>ovector</i> is a pointer to the vector of integer offsets that was passed to
1444     <b>pcre_exec()</b>, and <i>stringcount</i> is the number of substrings that were
1445     captured by the match, including the substring that matched the entire regular
1446 nigel 75 expression. This is the value returned by <b>pcre_exec()</b> if it is greater
1447     than zero. If <b>pcre_exec()</b> returned zero, indicating that it ran out of
1448     space in <i>ovector</i>, the value passed as <i>stringcount</i> should be the
1449     number of elements in the vector divided by three.
1450 nigel 63 </P>
1451     <P>
1452     The functions <b>pcre_copy_substring()</b> and <b>pcre_get_substring()</b>
1453     extract a single substring, whose number is given as <i>stringnumber</i>. A
1454 nigel 75 value of zero extracts the substring that matched the entire pattern, whereas
1455 nigel 63 higher values extract the captured substrings. For <b>pcre_copy_substring()</b>,
1456     the string is placed in <i>buffer</i>, whose length is given by
1457     <i>buffersize</i>, while for <b>pcre_get_substring()</b> a new block of memory is
1458     obtained via <b>pcre_malloc</b>, and its address is returned via
1459     <i>stringptr</i>. The yield of the function is the length of the string, not
1460     including the terminating zero, or one of
1461     <pre>
1463 nigel 75 </pre>
1464 nigel 63 The buffer was too small for <b>pcre_copy_substring()</b>, or the attempt to get
1465     memory failed for <b>pcre_get_substring()</b>.
1466     <pre>
1468 nigel 75 </pre>
1469 nigel 63 There is no substring whose number is <i>stringnumber</i>.
1470     </P>
1471     <P>
1472     The <b>pcre_get_substring_list()</b> function extracts all available substrings
1473     and builds a list of pointers to them. All this is done in a single block of
1474 nigel 75 memory that is obtained via <b>pcre_malloc</b>. The address of the memory block
1475 nigel 63 is returned via <i>listptr</i>, which is also the start of the list of string
1476     pointers. The end of the list is marked by a NULL pointer. The yield of the
1477     function is zero if all went well, or
1478     <pre>
1480 nigel 75 </pre>
1481 nigel 63 if the attempt to get the memory block failed.
1482     </P>
1483     <P>
1484     When any of these functions encounter a substring that is unset, which can
1485     happen when capturing subpattern number <i>n+1</i> matches some part of the
1486     subject, but subpattern <i>n</i> has not been used at all, they return an empty
1487     string. This can be distinguished from a genuine zero-length substring by
1488     inspecting the appropriate offset in <i>ovector</i>, which is negative for unset
1489     substrings.
1490     </P>
1491     <P>
1492     The two convenience functions <b>pcre_free_substring()</b> and
1493     <b>pcre_free_substring_list()</b> can be used to free the memory returned by
1494     a previous call of <b>pcre_get_substring()</b> or
1495     <b>pcre_get_substring_list()</b>, respectively. They do nothing more than call
1496     the function pointed to by <b>pcre_free</b>, which of course could be called
1497     directly from a C program. However, PCRE is used in some situations where it is
1498 nigel 91 linked via a special interface to another programming language that cannot use
1499 nigel 63 <b>pcre_free</b> directly; it is for these cases that the functions are
1500     provided.
1501     </P>
1502 nigel 91 <br><a name="SEC16" href="#TOC1">EXTRACTING CAPTURED SUBSTRINGS BY NAME</a><br>
1503 nigel 63 <P>
1504 nigel 75 <b>int pcre_get_stringnumber(const pcre *<i>code</i>,</b>
1505     <b>const char *<i>name</i>);</b>
1506     </P>
1507     <P>
1508 nigel 63 <b>int pcre_copy_named_substring(const pcre *<i>code</i>,</b>
1509     <b>const char *<i>subject</i>, int *<i>ovector</i>,</b>
1510     <b>int <i>stringcount</i>, const char *<i>stringname</i>,</b>
1511     <b>char *<i>buffer</i>, int <i>buffersize</i>);</b>
1512     </P>
1513     <P>
1514     <b>int pcre_get_named_substring(const pcre *<i>code</i>,</b>
1515     <b>const char *<i>subject</i>, int *<i>ovector</i>,</b>
1516     <b>int <i>stringcount</i>, const char *<i>stringname</i>,</b>
1517     <b>const char **<i>stringptr</i>);</b>
1518     </P>
1519     <P>
1520 nigel 75 To extract a substring by name, you first have to find associated number.
1521     For example, for this pattern
1522 nigel 63 <pre>
1523 nigel 79 (a+)b(?P&#60;xxx&#62;\d+)...
1524 nigel 75 </pre>
1525 nigel 91 the number of the subpattern called "xxx" is 2. If the name is known to be
1526     unique (PCRE_DUPNAMES was not set), you can find the number from the name by
1527     calling <b>pcre_get_stringnumber()</b>. The first argument is the compiled
1528     pattern, and the second is the name. The yield of the function is the
1529 nigel 75 subpattern number, or PCRE_ERROR_NOSUBSTRING (-7) if there is no subpattern of
1530     that name.
1531 nigel 63 </P>
1532     <P>
1533 nigel 75 Given the number, you can extract the substring directly, or use one of the
1534     functions described in the previous section. For convenience, there are also
1535     two functions that do the whole job.
1536 nigel 63 </P>
1537     <P>
1538 nigel 91 Most of the arguments of <b>pcre_copy_named_substring()</b> and
1539     <b>pcre_get_named_substring()</b> are the same as those for the similarly named
1540 nigel 75 functions that extract by number. As these are described in the previous
1541     section, they are not re-described here. There are just two differences:
1542 nigel 63 </P>
1543     <P>
1544     First, instead of a substring number, a substring name is given. Second, there
1545     is an extra argument, given at the start, which is a pointer to the compiled
1546     pattern. This is needed in order to gain access to the name-to-number
1547     translation table.
1548     </P>
1549     <P>
1550     These functions call <b>pcre_get_stringnumber()</b>, and if it succeeds, they
1551     then call <i>pcre_copy_substring()</i> or <i>pcre_get_substring()</i>, as
1552     appropriate.
1553     </P>
1554 nigel 91 <br><a name="SEC17" href="#TOC1">DUPLICATE SUBPATTERN NAMES</a><br>
1555 nigel 63 <P>
1556 nigel 91 <b>int pcre_get_stringtable_entries(const pcre *<i>code</i>,</b>
1557     <b>const char *<i>name</i>, char **<i>first</i>, char **<i>last</i>);</b>
1558     </P>
1559     <P>
1560     When a pattern is compiled with the PCRE_DUPNAMES option, names for subpatterns
1561     are not required to be unique. Normally, patterns with duplicate names are such
1562     that in any one match, only one of the named subpatterns participates. An
1563     example is shown in the
1564     <a href="pcrepattern.html"><b>pcrepattern</b></a>
1565     documentation. When duplicates are present, <b>pcre_copy_named_substring()</b>
1566     and <b>pcre_get_named_substring()</b> return the first substring corresponding
1567     to the given name that is set. If none are set, an empty string is returned.
1568     The <b>pcre_get_stringnumber()</b> function returns one of the numbers that are
1569     associated with the name, but it is not defined which it is.
1570     <br>
1571     <br>
1572     If you want to get full details of all captured substrings for a given name,
1573     you must use the <b>pcre_get_stringtable_entries()</b> function. The first
1574     argument is the compiled pattern, and the second is the name. The third and
1575     fourth are pointers to variables which are updated by the function. After it
1576     has run, they point to the first and last entries in the name-to-number table
1577     for the given name. The function itself returns the length of each entry, or
1578     PCRE_ERROR_NOSUBSTRING if there are none. The format of the table is described
1579     above in the section entitled <i>Information about a pattern</i>. Given all the
1580     relevant entries for the name, you can extract each of their numbers, and hence
1581     the captured data, if any.
1582     </P>
1583     <br><a name="SEC18" href="#TOC1">FINDING ALL POSSIBLE MATCHES</a><br>
1584     <P>
1585 nigel 77 The traditional matching function uses a similar algorithm to Perl, which stops
1586     when it finds the first match, starting at a given point in the subject. If you
1587     want to find all possible matches, or the longest possible match, consider
1588     using the alternative matching function (see below) instead. If you cannot use
1589     the alternative function, but still need to find all possible matches, you
1590     can kludge it up by making use of the callout facility, which is described in
1591     the
1592     <a href="pcrecallout.html"><b>pcrecallout</b></a>
1593     documentation.
1594     </P>
1595     <P>
1596     What you have to do is to insert a callout right at the end of the pattern.
1597     When your callout function is called, extract and save the current matched
1598     substring. Then return 1, which forces <b>pcre_exec()</b> to backtrack and try
1599     other alternatives. Ultimately, when it runs out of matches, <b>pcre_exec()</b>
1600     will yield PCRE_ERROR_NOMATCH.
1601     <a name="dfamatch"></a></P>
1602 nigel 91 <br><a name="SEC19" href="#TOC1">MATCHING A PATTERN: THE ALTERNATIVE FUNCTION</a><br>
1603 nigel 77 <P>
1604     <b>int pcre_dfa_exec(const pcre *<i>code</i>, const pcre_extra *<i>extra</i>,</b>
1605     <b>const char *<i>subject</i>, int <i>length</i>, int <i>startoffset</i>,</b>
1606     <b>int <i>options</i>, int *<i>ovector</i>, int <i>ovecsize</i>,</b>
1607     <b>int *<i>workspace</i>, int <i>wscount</i>);</b>
1608     </P>
1609     <P>
1610     The function <b>pcre_dfa_exec()</b> is called to match a subject string against
1611     a compiled pattern, using a "DFA" matching algorithm. This has different
1612     characteristics to the normal algorithm, and is not compatible with Perl. Some
1613     of the features of PCRE patterns are not supported. Nevertheless, there are
1614     times when this kind of matching can be useful. For a discussion of the two
1615     matching algorithms, see the
1616     <a href="pcrematching.html"><b>pcrematching</b></a>
1617     documentation.
1618     </P>
1619     <P>
1620     The arguments for the <b>pcre_dfa_exec()</b> function are the same as for
1621     <b>pcre_exec()</b>, plus two extras. The <i>ovector</i> argument is used in a
1622     different way, and this is described below. The other common arguments are used
1623     in the same way as for <b>pcre_exec()</b>, so their description is not repeated
1624     here.
1625     </P>
1626     <P>
1627     The two additional arguments provide workspace for the function. The workspace
1628     vector should contain at least 20 elements. It is used for keeping track of
1629     multiple paths through the pattern tree. More workspace will be needed for
1630 nigel 91 patterns and subjects where there are a lot of potential matches.
1631 nigel 77 </P>
1632     <P>
1633 nigel 87 Here is an example of a simple call to <b>pcre_dfa_exec()</b>:
1634 nigel 77 <pre>
1635     int rc;
1636     int ovector[10];
1637     int wspace[20];
1638 nigel 87 rc = pcre_dfa_exec(
1639 nigel 77 re, /* result of pcre_compile() */
1640     NULL, /* we didn't study the pattern */
1641     "some string", /* the subject string */
1642     11, /* the length of the subject string */
1643     0, /* start at offset 0 in the subject */
1644     0, /* default options */
1645     ovector, /* vector of integers for substring information */
1646     10, /* number of elements (NOT size in bytes) */
1647     wspace, /* working space vector */
1648     20); /* number of elements (NOT size in bytes) */
1649     </PRE>
1650     </P>
1651     <br><b>
1652     Option bits for <b>pcre_dfa_exec()</b>
1653     </b><br>
1654     <P>
1655     The unused bits of the <i>options</i> argument for <b>pcre_dfa_exec()</b> must be
1656 nigel 91 zero. The only bits that may be set are PCRE_ANCHORED, PCRE_NEWLINE_<i>xxx</i>,
1658 nigel 77 PCRE_DFA_SHORTEST, and PCRE_DFA_RESTART. All but the last three of these are
1659     the same as for <b>pcre_exec()</b>, so their description is not repeated here.
1660     <pre>
1662     </pre>
1663     This has the same general effect as it does for <b>pcre_exec()</b>, but the
1664     details are slightly different. When PCRE_PARTIAL is set for
1665     <b>pcre_dfa_exec()</b>, the return code PCRE_ERROR_NOMATCH is converted into
1666     PCRE_ERROR_PARTIAL if the end of the subject is reached, there have been no
1667     complete matches, but there is still at least one matching possibility. The
1668     portion of the string that provided the partial match is set as the first
1669     matching string.
1670     <pre>
1672     </pre>
1673     Setting the PCRE_DFA_SHORTEST option causes the matching algorithm to stop as
1674     soon as it has found one match. Because of the way the DFA algorithm works,
1675     this is necessarily the shortest possible match at the first possible matching
1676     point in the subject string.
1677     <pre>
1679     </pre>
1680     When <b>pcre_dfa_exec()</b> is called with the PCRE_PARTIAL option, and returns
1681     a partial match, it is possible to call it again, with additional subject
1682     characters, and have it continue with the same match. The PCRE_DFA_RESTART
1683     option requests this action; when it is set, the <i>workspace</i> and
1684     <i>wscount</i> options must reference the same vector as before because data
1685     about the match so far is left in them after a partial match. There is more
1686     discussion of this facility in the
1687     <a href="pcrepartial.html"><b>pcrepartial</b></a>
1688     documentation.
1689     </P>
1690     <br><b>
1691     Successful returns from <b>pcre_dfa_exec()</b>
1692     </b><br>
1693     <P>
1694     When <b>pcre_dfa_exec()</b> succeeds, it may have matched more than one
1695     substring in the subject. Note, however, that all the matches from one run of
1696     the function start at the same point in the subject. The shorter matches are
1697     all initial substrings of the longer matches. For example, if the pattern
1698     <pre>
1699     &#60;.*&#62;
1700     </pre>
1701     is matched against the string
1702     <pre>
1703     This is &#60;something&#62; &#60;something else&#62; &#60;something further&#62; no more
1704     </pre>
1705     the three matched strings are
1706     <pre>
1707     &#60;something&#62;
1708     &#60;something&#62; &#60;something else&#62;
1709     &#60;something&#62; &#60;something else&#62; &#60;something further&#62;
1710     </pre>
1711     On success, the yield of the function is a number greater than zero, which is
1712     the number of matched substrings. The substrings themselves are returned in
1713     <i>ovector</i>. Each string uses two elements; the first is the offset to the
1714     start, and the second is the offset to the end. All the strings have the same
1715     start offset. (Space could have been saved by giving this only once, but it was
1716     decided to retain some compatibility with the way <b>pcre_exec()</b> returns
1717     data, even though the meaning of the strings is different.)
1718     </P>
1719     <P>
1720     The strings are returned in reverse order of length; that is, the longest
1721     matching string is given first. If there were too many matches to fit into
1722     <i>ovector</i>, the yield of the function is zero, and the vector is filled with
1723     the longest matches.
1724     </P>
1725     <br><b>
1726     Error returns from <b>pcre_dfa_exec()</b>
1727     </b><br>
1728     <P>
1729     The <b>pcre_dfa_exec()</b> function returns a negative number when it fails.
1730     Many of the errors are the same as for <b>pcre_exec()</b>, and these are
1731     described
1732     <a href="#errorlist">above.</a>
1733     There are in addition the following errors that are specific to
1734     <b>pcre_dfa_exec()</b>:
1735     <pre>
1736     PCRE_ERROR_DFA_UITEM (-16)
1737     </pre>
1738     This return is given if <b>pcre_dfa_exec()</b> encounters an item in the pattern
1739     that it does not support, for instance, the use of \C or a back reference.
1740     <pre>
1741     PCRE_ERROR_DFA_UCOND (-17)
1742     </pre>
1743     This return is given if <b>pcre_dfa_exec()</b> encounters a condition item in a
1744     pattern that uses a back reference for the condition. This is not supported.
1745     <pre>
1747     </pre>
1748     This return is given if <b>pcre_dfa_exec()</b> is called with an <i>extra</i>
1749     block that contains a setting of the <i>match_limit</i> field. This is not
1750     supported (it is meaningless).
1751     <pre>
1752     PCRE_ERROR_DFA_WSSIZE (-19)
1753     </pre>
1754     This return is given if <b>pcre_dfa_exec()</b> runs out of space in the
1755     <i>workspace</i> vector.
1756     <pre>
1758     </pre>
1759     When a recursive subpattern is processed, the matching function calls itself
1760     recursively, using private vectors for <i>ovector</i> and <i>workspace</i>. This
1761     error is given if the output vector is not large enough. This should be
1762     extremely rare, as a vector of size 1000 is used.
1763     </P>
1764     <P>
1765 nigel 91 Last updated: 08 June 2006
1766 nigel 63 <br>
1767 nigel 87 Copyright &copy; 1997-2006 University of Cambridge.
1768 nigel 75 <p>
1769     Return to the <a href="index.html">PCRE index page</a>.
1770     </p>

ViewVC Help
Powered by ViewVC 1.1.12