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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 ph10 111 <p>
11 nigel 75 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 ph10 111 <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 93 <li><a name="TOC20" href="#SEC20">SEE ALSO</a>
36 ph10 99 <li><a name="TOC21" href="#SEC21">AUTHOR</a>
37     <li><a name="TOC22" href="#SEC22">REVISION</a>
38 nigel 63 </ul>
39 nigel 75 <br><a name="SEC1" href="#TOC1">PCRE NATIVE API</a><br>
40 nigel 63 <P>
41     <b>#include &#60;pcre.h&#62;</b>
42     </P>
43     <P>
44     <b>pcre *pcre_compile(const char *<i>pattern</i>, int <i>options</i>,</b>
45     <b>const char **<i>errptr</i>, int *<i>erroffset</i>,</b>
46     <b>const unsigned char *<i>tableptr</i>);</b>
47     </P>
48     <P>
49 nigel 77 <b>pcre *pcre_compile2(const char *<i>pattern</i>, int <i>options</i>,</b>
50     <b>int *<i>errorcodeptr</i>,</b>
51     <b>const char **<i>errptr</i>, int *<i>erroffset</i>,</b>
52     <b>const unsigned char *<i>tableptr</i>);</b>
53     </P>
54     <P>
55 nigel 63 <b>pcre_extra *pcre_study(const pcre *<i>code</i>, int <i>options</i>,</b>
56     <b>const char **<i>errptr</i>);</b>
57     </P>
58     <P>
59     <b>int pcre_exec(const pcre *<i>code</i>, const pcre_extra *<i>extra</i>,</b>
60     <b>const char *<i>subject</i>, int <i>length</i>, int <i>startoffset</i>,</b>
61     <b>int <i>options</i>, int *<i>ovector</i>, int <i>ovecsize</i>);</b>
62     </P>
63     <P>
64 nigel 77 <b>int pcre_dfa_exec(const pcre *<i>code</i>, const pcre_extra *<i>extra</i>,</b>
65     <b>const char *<i>subject</i>, int <i>length</i>, int <i>startoffset</i>,</b>
66     <b>int <i>options</i>, int *<i>ovector</i>, int <i>ovecsize</i>,</b>
67     <b>int *<i>workspace</i>, int <i>wscount</i>);</b>
68     </P>
69     <P>
70 nigel 63 <b>int pcre_copy_named_substring(const pcre *<i>code</i>,</b>
71     <b>const char *<i>subject</i>, int *<i>ovector</i>,</b>
72     <b>int <i>stringcount</i>, const char *<i>stringname</i>,</b>
73     <b>char *<i>buffer</i>, int <i>buffersize</i>);</b>
74     </P>
75     <P>
76     <b>int pcre_copy_substring(const char *<i>subject</i>, int *<i>ovector</i>,</b>
77     <b>int <i>stringcount</i>, int <i>stringnumber</i>, char *<i>buffer</i>,</b>
78     <b>int <i>buffersize</i>);</b>
79     </P>
80     <P>
81     <b>int pcre_get_named_substring(const pcre *<i>code</i>,</b>
82     <b>const char *<i>subject</i>, int *<i>ovector</i>,</b>
83     <b>int <i>stringcount</i>, const char *<i>stringname</i>,</b>
84     <b>const char **<i>stringptr</i>);</b>
85     </P>
86     <P>
87     <b>int pcre_get_stringnumber(const pcre *<i>code</i>,</b>
88     <b>const char *<i>name</i>);</b>
89     </P>
90     <P>
91 nigel 91 <b>int pcre_get_stringtable_entries(const pcre *<i>code</i>,</b>
92     <b>const char *<i>name</i>, char **<i>first</i>, char **<i>last</i>);</b>
93     </P>
94     <P>
95 nigel 63 <b>int pcre_get_substring(const char *<i>subject</i>, int *<i>ovector</i>,</b>
96     <b>int <i>stringcount</i>, int <i>stringnumber</i>,</b>
97     <b>const char **<i>stringptr</i>);</b>
98     </P>
99     <P>
100     <b>int pcre_get_substring_list(const char *<i>subject</i>,</b>
101     <b>int *<i>ovector</i>, int <i>stringcount</i>, const char ***<i>listptr</i>);</b>
102     </P>
103     <P>
104     <b>void pcre_free_substring(const char *<i>stringptr</i>);</b>
105     </P>
106     <P>
107     <b>void pcre_free_substring_list(const char **<i>stringptr</i>);</b>
108     </P>
109     <P>
110     <b>const unsigned char *pcre_maketables(void);</b>
111     </P>
112     <P>
113     <b>int pcre_fullinfo(const pcre *<i>code</i>, const pcre_extra *<i>extra</i>,</b>
114     <b>int <i>what</i>, void *<i>where</i>);</b>
115     </P>
116     <P>
117     <b>int pcre_info(const pcre *<i>code</i>, int *<i>optptr</i>, int</b>
118     <b>*<i>firstcharptr</i>);</b>
119     </P>
120     <P>
121 nigel 77 <b>int pcre_refcount(pcre *<i>code</i>, int <i>adjust</i>);</b>
122     </P>
123     <P>
124 nigel 63 <b>int pcre_config(int <i>what</i>, void *<i>where</i>);</b>
125     </P>
126     <P>
127     <b>char *pcre_version(void);</b>
128     </P>
129     <P>
130     <b>void *(*pcre_malloc)(size_t);</b>
131     </P>
132     <P>
133     <b>void (*pcre_free)(void *);</b>
134     </P>
135     <P>
136 nigel 73 <b>void *(*pcre_stack_malloc)(size_t);</b>
137     </P>
138     <P>
139     <b>void (*pcre_stack_free)(void *);</b>
140     </P>
141     <P>
142 nigel 63 <b>int (*pcre_callout)(pcre_callout_block *);</b>
143     </P>
144 nigel 75 <br><a name="SEC2" href="#TOC1">PCRE API OVERVIEW</a><br>
145 nigel 63 <P>
146 nigel 93 PCRE has its own native API, which is described in this document. There are
147     also some wrapper functions that correspond to the POSIX regular expression
148 nigel 77 API. These are described in the
149 nigel 75 <a href="pcreposix.html"><b>pcreposix</b></a>
150 nigel 77 documentation. Both of these APIs define a set of C function calls. A C++
151     wrapper is distributed with PCRE. It is documented in the
152     <a href="pcrecpp.html"><b>pcrecpp</b></a>
153     page.
154 nigel 63 </P>
155     <P>
156 nigel 77 The native API C function prototypes are defined in the header file
157     <b>pcre.h</b>, and on Unix systems the library itself is called <b>libpcre</b>.
158     It can normally be accessed by adding <b>-lpcre</b> to the command for linking
159     an application that uses PCRE. The header file defines the macros PCRE_MAJOR
160     and PCRE_MINOR to contain the major and minor release numbers for the library.
161 nigel 75 Applications can use these to include support for different releases of PCRE.
162 nigel 63 </P>
163     <P>
164 nigel 77 The functions <b>pcre_compile()</b>, <b>pcre_compile2()</b>, <b>pcre_study()</b>,
165     and <b>pcre_exec()</b> are used for compiling and matching regular expressions
166     in a Perl-compatible manner. A sample program that demonstrates the simplest
167     way of using them is provided in the file called <i>pcredemo.c</i> in the source
168     distribution. The
169 nigel 75 <a href="pcresample.html"><b>pcresample</b></a>
170     documentation describes how to run it.
171 nigel 63 </P>
172     <P>
173 nigel 77 A second matching function, <b>pcre_dfa_exec()</b>, which is not
174     Perl-compatible, is also provided. This uses a different algorithm for the
175 nigel 91 matching. The alternative algorithm finds all possible matches (at a given
176 nigel 93 point in the subject), and scans the subject just once. However, this algorithm
177     does not return captured substrings. A description of the two matching
178     algorithms and their advantages and disadvantages is given in the
179 nigel 77 <a href="pcrematching.html"><b>pcrematching</b></a>
180     documentation.
181     </P>
182     <P>
183 nigel 75 In addition to the main compiling and matching functions, there are convenience
184 nigel 77 functions for extracting captured substrings from a subject string that is
185     matched by <b>pcre_exec()</b>. They are:
186 nigel 63 <pre>
187     <b>pcre_copy_substring()</b>
188     <b>pcre_copy_named_substring()</b>
189     <b>pcre_get_substring()</b>
190     <b>pcre_get_named_substring()</b>
191     <b>pcre_get_substring_list()</b>
192 nigel 75 <b>pcre_get_stringnumber()</b>
193 nigel 91 <b>pcre_get_stringtable_entries()</b>
194 nigel 75 </pre>
195 nigel 63 <b>pcre_free_substring()</b> and <b>pcre_free_substring_list()</b> are also
196     provided, to free the memory used for extracted strings.
197     </P>
198     <P>
199 nigel 75 The function <b>pcre_maketables()</b> is used to build a set of character tables
200 nigel 77 in the current locale for passing to <b>pcre_compile()</b>, <b>pcre_exec()</b>,
201     or <b>pcre_dfa_exec()</b>. This is an optional facility that is provided for
202     specialist use. Most commonly, no special tables are passed, in which case
203     internal tables that are generated when PCRE is built are used.
204 nigel 63 </P>
205     <P>
206     The function <b>pcre_fullinfo()</b> is used to find out information about a
207 nigel 75 compiled pattern; <b>pcre_info()</b> is an obsolete version that returns only
208 nigel 63 some of the available information, but is retained for backwards compatibility.
209     The function <b>pcre_version()</b> returns a pointer to a string containing the
210     version of PCRE and its date of release.
211     </P>
212     <P>
213 nigel 77 The function <b>pcre_refcount()</b> maintains a reference count in a data block
214     containing a compiled pattern. This is provided for the benefit of
215     object-oriented applications.
216     </P>
217     <P>
218 nigel 63 The global variables <b>pcre_malloc</b> and <b>pcre_free</b> initially contain
219 nigel 75 the entry points of the standard <b>malloc()</b> and <b>free()</b> functions,
220 nigel 63 respectively. PCRE calls the memory management functions via these variables,
221     so a calling program can replace them if it wishes to intercept the calls. This
222     should be done before calling any PCRE functions.
223     </P>
224     <P>
225 nigel 73 The global variables <b>pcre_stack_malloc</b> and <b>pcre_stack_free</b> are also
226     indirections to memory management functions. These special functions are used
227     only when PCRE is compiled to use the heap for remembering data, instead of
228 nigel 91 recursive function calls, when running the <b>pcre_exec()</b> function. See the
229     <a href="pcrebuild.html"><b>pcrebuild</b></a>
230     documentation for details of how to do this. It is a non-standard way of
231     building PCRE, for use in environments that have limited stacks. Because of the
232     greater use of memory management, it runs more slowly. Separate functions are
233     provided so that special-purpose external code can be used for this case. When
234     used, these functions are always called in a stack-like manner (last obtained,
235     first freed), and always for memory blocks of the same size. There is a
236     discussion about PCRE's stack usage in the
237     <a href="pcrestack.html"><b>pcrestack</b></a>
238     documentation.
239 nigel 73 </P>
240     <P>
241 nigel 63 The global variable <b>pcre_callout</b> initially contains NULL. It can be set
242     by the caller to a "callout" function, which PCRE will then call at specified
243 nigel 75 points during a matching operation. Details are given in the
244     <a href="pcrecallout.html"><b>pcrecallout</b></a>
245 nigel 63 documentation.
246 ph10 227 <a name="newlines"></a></P>
247 nigel 91 <br><a name="SEC3" href="#TOC1">NEWLINES</a><br>
248 nigel 63 <P>
249 ph10 150 PCRE supports five different conventions for indicating line breaks in
250 nigel 93 strings: a single CR (carriage return) character, a single LF (linefeed)
251 ph10 150 character, the two-character sequence CRLF, any of the three preceding, or any
252     Unicode newline sequence. The Unicode newline sequences are the three just
253     mentioned, plus the single characters VT (vertical tab, U+000B), FF (formfeed,
254     U+000C), NEL (next line, U+0085), LS (line separator, U+2028), and PS
255     (paragraph separator, U+2029).
256 nigel 93 </P>
257     <P>
258     Each of the first three conventions is used by at least one operating system as
259     its standard newline sequence. When PCRE is built, a default can be specified.
260     The default default is LF, which is the Unix standard. When PCRE is run, the
261     default can be overridden, either when a pattern is compiled, or when it is
262     matched.
263     </P>
264     <P>
265 ph10 227 At compile time, the newline convention can be specified by the <i>options</i>
266     argument of <b>pcre_compile()</b>, or it can be specified by special text at the
267     start of the pattern itself; this overrides any other settings. See the
268     <a href="pcrepattern.html"><b>pcrepattern</b></a>
269     page for details of the special character sequences.
270     </P>
271     <P>
272 nigel 91 In the PCRE documentation the word "newline" is used to mean "the character or
273 nigel 93 pair of characters that indicate a line break". The choice of newline
274     convention affects the handling of the dot, circumflex, and dollar
275     metacharacters, the handling of #-comments in /x mode, and, when CRLF is a
276     recognized line ending sequence, the match position advancement for a
277 ph10 227 non-anchored pattern. There is more detail about this in the
278     <a href="#execoptions">section on <b>pcre_exec()</b> options</a>
279     below. The choice of newline convention does not affect the interpretation of
280     the \n or \r escape sequences.
281 nigel 91 </P>
282     <br><a name="SEC4" href="#TOC1">MULTITHREADING</a><br>
283     <P>
284 nigel 63 The PCRE functions can be used in multi-threading applications, with the
285 nigel 73 proviso that the memory management functions pointed to by <b>pcre_malloc</b>,
286     <b>pcre_free</b>, <b>pcre_stack_malloc</b>, and <b>pcre_stack_free</b>, and the
287     callout function pointed to by <b>pcre_callout</b>, are shared by all threads.
288 nigel 63 </P>
289     <P>
290     The compiled form of a regular expression is not altered during matching, so
291     the same compiled pattern can safely be used by several threads at once.
292     </P>
293 nigel 91 <br><a name="SEC5" href="#TOC1">SAVING PRECOMPILED PATTERNS FOR LATER USE</a><br>
294 nigel 63 <P>
295 nigel 75 The compiled form of a regular expression can be saved and re-used at a later
296     time, possibly by a different program, and even on a host other than the one on
297     which it was compiled. Details are given in the
298     <a href="pcreprecompile.html"><b>pcreprecompile</b></a>
299 ph10 155 documentation. However, compiling a regular expression with one version of PCRE
300     for use with a different version is not guaranteed to work and may cause
301     crashes.
302 nigel 75 </P>
303 nigel 91 <br><a name="SEC6" href="#TOC1">CHECKING BUILD-TIME OPTIONS</a><br>
304 nigel 75 <P>
305 nigel 63 <b>int pcre_config(int <i>what</i>, void *<i>where</i>);</b>
306     </P>
307     <P>
308     The function <b>pcre_config()</b> makes it possible for a PCRE client to
309     discover which optional features have been compiled into the PCRE library. The
310     <a href="pcrebuild.html"><b>pcrebuild</b></a>
311     documentation has more details about these optional features.
312     </P>
313     <P>
314     The first argument for <b>pcre_config()</b> is an integer, specifying which
315     information is required; the second argument is a pointer to a variable into
316     which the information is placed. The following information is available:
317     <pre>
318     PCRE_CONFIG_UTF8
319 nigel 75 </pre>
320 nigel 63 The output is an integer that is set to one if UTF-8 support is available;
321     otherwise it is set to zero.
322     <pre>
323 nigel 75 PCRE_CONFIG_UNICODE_PROPERTIES
324     </pre>
325     The output is an integer that is set to one if support for Unicode character
326     properties is available; otherwise it is set to zero.
327     <pre>
328 nigel 63 PCRE_CONFIG_NEWLINE
329 nigel 75 </pre>
330 nigel 91 The output is an integer whose value specifies the default character sequence
331 nigel 93 that is recognized as meaning "newline". The four values that are supported
332 ph10 150 are: 10 for LF, 13 for CR, 3338 for CRLF, -2 for ANYCRLF, and -1 for ANY. The
333     default should normally be the standard sequence for your operating system.
334 nigel 63 <pre>
335     PCRE_CONFIG_LINK_SIZE
336 nigel 75 </pre>
337 nigel 63 The output is an integer that contains the number of bytes used for internal
338     linkage in compiled regular expressions. The value is 2, 3, or 4. Larger values
339     allow larger regular expressions to be compiled, at the expense of slower
340     matching. The default value of 2 is sufficient for all but the most massive
341     patterns, since it allows the compiled pattern to be up to 64K in size.
342     <pre>
343     PCRE_CONFIG_POSIX_MALLOC_THRESHOLD
344 nigel 75 </pre>
345 nigel 63 The output is an integer that contains the threshold above which the POSIX
346     interface uses <b>malloc()</b> for output vectors. Further details are given in
347 nigel 75 the
348     <a href="pcreposix.html"><b>pcreposix</b></a>
349     documentation.
350 nigel 63 <pre>
351     PCRE_CONFIG_MATCH_LIMIT
352 nigel 75 </pre>
353 nigel 63 The output is an integer that gives the default limit for the number of
354     internal matching function calls in a <b>pcre_exec()</b> execution. Further
355     details are given with <b>pcre_exec()</b> below.
356 nigel 73 <pre>
357 nigel 87 PCRE_CONFIG_MATCH_LIMIT_RECURSION
358     </pre>
359     The output is an integer that gives the default limit for the depth of
360     recursion when calling the internal matching function in a <b>pcre_exec()</b>
361     execution. Further details are given with <b>pcre_exec()</b> below.
362     <pre>
363 nigel 73 PCRE_CONFIG_STACKRECURSE
364 nigel 75 </pre>
365 nigel 77 The output is an integer that is set to one if internal recursion when running
366     <b>pcre_exec()</b> is implemented by recursive function calls that use the stack
367     to remember their state. This is the usual way that PCRE is compiled. The
368     output is zero if PCRE was compiled to use blocks of data on the heap instead
369     of recursive function calls. In this case, <b>pcre_stack_malloc</b> and
370     <b>pcre_stack_free</b> are called to manage memory blocks on the heap, thus
371     avoiding the use of the stack.
372 nigel 73 </P>
373 nigel 91 <br><a name="SEC7" href="#TOC1">COMPILING A PATTERN</a><br>
374 nigel 63 <P>
375     <b>pcre *pcre_compile(const char *<i>pattern</i>, int <i>options</i>,</b>
376     <b>const char **<i>errptr</i>, int *<i>erroffset</i>,</b>
377     <b>const unsigned char *<i>tableptr</i>);</b>
378 nigel 77 <b>pcre *pcre_compile2(const char *<i>pattern</i>, int <i>options</i>,</b>
379     <b>int *<i>errorcodeptr</i>,</b>
380     <b>const char **<i>errptr</i>, int *<i>erroffset</i>,</b>
381     <b>const unsigned char *<i>tableptr</i>);</b>
382 nigel 63 </P>
383     <P>
384 nigel 77 Either of the functions <b>pcre_compile()</b> or <b>pcre_compile2()</b> can be
385     called to compile a pattern into an internal form. The only difference between
386     the two interfaces is that <b>pcre_compile2()</b> has an additional argument,
387     <i>errorcodeptr</i>, via which a numerical error code can be returned.
388 nigel 63 </P>
389     <P>
390 nigel 77 The pattern is a C string terminated by a binary zero, and is passed in the
391     <i>pattern</i> argument. A pointer to a single block of memory that is obtained
392     via <b>pcre_malloc</b> is returned. This contains the compiled code and related
393     data. The <b>pcre</b> type is defined for the returned block; this is a typedef
394     for a structure whose contents are not externally defined. It is up to the
395 nigel 91 caller to free the memory (via <b>pcre_free</b>) when it is no longer required.
396 nigel 77 </P>
397     <P>
398 nigel 63 Although the compiled code of a PCRE regex is relocatable, that is, it does not
399     depend on memory location, the complete <b>pcre</b> data block is not
400 nigel 75 fully relocatable, because it may contain a copy of the <i>tableptr</i>
401     argument, which is an address (see below).
402 nigel 63 </P>
403     <P>
404 nigel 93 The <i>options</i> argument contains various bit settings that affect the
405 nigel 75 compilation. It should be zero if no options are required. The available
406     options are described below. Some of them, in particular, those that are
407     compatible with Perl, can also be set and unset from within the pattern (see
408     the detailed description in the
409     <a href="pcrepattern.html"><b>pcrepattern</b></a>
410     documentation). For these options, the contents of the <i>options</i> argument
411     specifies their initial settings at the start of compilation and execution. The
412 nigel 91 PCRE_ANCHORED and PCRE_NEWLINE_<i>xxx</i> options can be set at the time of
413     matching as well as at compile time.
414 nigel 63 </P>
415     <P>
416     If <i>errptr</i> is NULL, <b>pcre_compile()</b> returns NULL immediately.
417     Otherwise, if compilation of a pattern fails, <b>pcre_compile()</b> returns
418     NULL, and sets the variable pointed to by <i>errptr</i> to point to a textual
419 nigel 87 error message. This is a static string that is part of the library. You must
420     not try to free it. The offset from the start of the pattern to the character
421     where the error was discovered is placed in the variable pointed to by
422 nigel 63 <i>erroffset</i>, which must not be NULL. If it is, an immediate error is given.
423     </P>
424     <P>
425 nigel 77 If <b>pcre_compile2()</b> is used instead of <b>pcre_compile()</b>, and the
426     <i>errorcodeptr</i> argument is not NULL, a non-zero error code number is
427     returned via this argument in the event of an error. This is in addition to the
428     textual error message. Error codes and messages are listed below.
429     </P>
430     <P>
431 nigel 63 If the final argument, <i>tableptr</i>, is NULL, PCRE uses a default set of
432 nigel 75 character tables that are built when PCRE is compiled, using the default C
433     locale. Otherwise, <i>tableptr</i> must be an address that is the result of a
434     call to <b>pcre_maketables()</b>. This value is stored with the compiled
435     pattern, and used again by <b>pcre_exec()</b>, unless another table pointer is
436     passed to it. For more discussion, see the section on locale support below.
437 nigel 63 </P>
438     <P>
439     This code fragment shows a typical straightforward call to <b>pcre_compile()</b>:
440     <pre>
441     pcre *re;
442     const char *error;
443     int erroffset;
444     re = pcre_compile(
445     "^A.*Z", /* the pattern */
446     0, /* default options */
447     &error, /* for error message */
448     &erroffset, /* for error offset */
449     NULL); /* use default character tables */
450 nigel 75 </pre>
451     The following names for option bits are defined in the <b>pcre.h</b> header
452     file:
453 nigel 63 <pre>
454     PCRE_ANCHORED
455 nigel 75 </pre>
456 nigel 63 If this bit is set, the pattern is forced to be "anchored", that is, it is
457 nigel 75 constrained to match only at the first matching point in the string that is
458 nigel 63 being searched (the "subject string"). This effect can also be achieved by
459     appropriate constructs in the pattern itself, which is the only way to do it in
460     Perl.
461     <pre>
462 nigel 75 PCRE_AUTO_CALLOUT
463     </pre>
464     If this bit is set, <b>pcre_compile()</b> automatically inserts callout items,
465     all with number 255, before each pattern item. For discussion of the callout
466     facility, see the
467     <a href="pcrecallout.html"><b>pcrecallout</b></a>
468     documentation.
469     <pre>
470 nigel 63 PCRE_CASELESS
471 nigel 75 </pre>
472 nigel 63 If this bit is set, letters in the pattern match both upper and lower case
473     letters. It is equivalent to Perl's /i option, and it can be changed within a
474 nigel 77 pattern by a (?i) option setting. In UTF-8 mode, PCRE always understands the
475     concept of case for characters whose values are less than 128, so caseless
476     matching is always possible. For characters with higher values, the concept of
477     case is supported if PCRE is compiled with Unicode property support, but not
478     otherwise. If you want to use caseless matching for characters 128 and above,
479     you must ensure that PCRE is compiled with Unicode property support as well as
480     with UTF-8 support.
481 nigel 63 <pre>
482     PCRE_DOLLAR_ENDONLY
483 nigel 75 </pre>
484 nigel 63 If this bit is set, a dollar metacharacter in the pattern matches only at the
485     end of the subject string. Without this option, a dollar also matches
486 nigel 91 immediately before a newline at the end of the string (but not before any other
487     newlines). The PCRE_DOLLAR_ENDONLY option is ignored if PCRE_MULTILINE is set.
488     There is no equivalent to this option in Perl, and no way to set it within a
489     pattern.
490 nigel 63 <pre>
491     PCRE_DOTALL
492 nigel 75 </pre>
493 nigel 63 If this bit is set, a dot metacharater in the pattern matches all characters,
494 nigel 91 including those that indicate newline. Without it, a dot does not match when
495     the current position is at a newline. This option is equivalent to Perl's /s
496     option, and it can be changed within a pattern by a (?s) option setting. A
497 nigel 93 negative class such as [^a] always matches newline characters, independent of
498     the setting of this option.
499 nigel 63 <pre>
500 nigel 91 PCRE_DUPNAMES
501     </pre>
502     If this bit is set, names used to identify capturing subpatterns need not be
503     unique. This can be helpful for certain types of pattern when it is known that
504     only one instance of the named subpattern can ever be matched. There are more
505     details of named subpatterns below; see also the
506     <a href="pcrepattern.html"><b>pcrepattern</b></a>
507     documentation.
508     <pre>
509 nigel 63 PCRE_EXTENDED
510 nigel 75 </pre>
511 nigel 63 If this bit is set, whitespace data characters in the pattern are totally
512     ignored except when escaped or inside a character class. Whitespace does not
513     include the VT character (code 11). In addition, characters between an
514 nigel 91 unescaped # outside a character class and the next newline, inclusive, are also
515     ignored. This is equivalent to Perl's /x option, and it can be changed within a
516     pattern by a (?x) option setting.
517 nigel 63 </P>
518     <P>
519     This option makes it possible to include comments inside complicated patterns.
520     Note, however, that this applies only to data characters. Whitespace characters
521     may never appear within special character sequences in a pattern, for example
522     within the sequence (?( which introduces a conditional subpattern.
523     <pre>
524     PCRE_EXTRA
525 nigel 75 </pre>
526 nigel 63 This option was invented in order to turn on additional functionality of PCRE
527     that is incompatible with Perl, but it is currently of very little use. When
528     set, any backslash in a pattern that is followed by a letter that has no
529     special meaning causes an error, thus reserving these combinations for future
530     expansion. By default, as in Perl, a backslash followed by a letter with no
531 nigel 91 special meaning is treated as a literal. (Perl can, however, be persuaded to
532     give a warning for this.) There are at present no other features controlled by
533     this option. It can also be set by a (?X) option setting within a pattern.
534 nigel 63 <pre>
535 nigel 77 PCRE_FIRSTLINE
536     </pre>
537     If this option is set, an unanchored pattern is required to match before or at
538 nigel 91 the first newline in the subject string, though the matched text may continue
539     over the newline.
540 nigel 77 <pre>
541 nigel 63 PCRE_MULTILINE
542 nigel 75 </pre>
543     By default, PCRE treats the subject string as consisting of a single line of
544     characters (even if it actually contains newlines). The "start of line"
545 nigel 63 metacharacter (^) matches only at the start of the string, while the "end of
546     line" metacharacter ($) matches only at the end of the string, or before a
547     terminating newline (unless PCRE_DOLLAR_ENDONLY is set). This is the same as
548     Perl.
549     </P>
550     <P>
551     When PCRE_MULTILINE it is set, the "start of line" and "end of line" constructs
552 nigel 91 match immediately following or immediately before internal newlines in the
553     subject string, respectively, as well as at the very start and end. This is
554     equivalent to Perl's /m option, and it can be changed within a pattern by a
555     (?m) option setting. If there are no newlines in a subject string, or no
556 nigel 63 occurrences of ^ or $ in a pattern, setting PCRE_MULTILINE has no effect.
557     <pre>
558 nigel 91 PCRE_NEWLINE_CR
559     PCRE_NEWLINE_LF
560     PCRE_NEWLINE_CRLF
561 ph10 150 PCRE_NEWLINE_ANYCRLF
562 nigel 93 PCRE_NEWLINE_ANY
563 nigel 91 </pre>
564     These options override the default newline definition that was chosen when PCRE
565     was built. Setting the first or the second specifies that a newline is
566 nigel 93 indicated by a single character (CR or LF, respectively). Setting
567     PCRE_NEWLINE_CRLF specifies that a newline is indicated by the two-character
568 ph10 150 CRLF sequence. Setting PCRE_NEWLINE_ANYCRLF specifies that any of the three
569     preceding sequences should be recognized. Setting PCRE_NEWLINE_ANY specifies
570     that any Unicode newline sequence should be recognized. The Unicode newline
571     sequences are the three just mentioned, plus the single characters VT (vertical
572     tab, U+000B), FF (formfeed, U+000C), NEL (next line, U+0085), LS (line
573     separator, U+2028), and PS (paragraph separator, U+2029). The last two are
574     recognized only in UTF-8 mode.
575 nigel 91 </P>
576     <P>
577 nigel 93 The newline setting in the options word uses three bits that are treated
578 ph10 150 as a number, giving eight possibilities. Currently only six are used (default
579     plus the five values above). This means that if you set more than one newline
580 nigel 93 option, the combination may or may not be sensible. For example,
581     PCRE_NEWLINE_CR with PCRE_NEWLINE_LF is equivalent to PCRE_NEWLINE_CRLF, but
582 ph10 150 other combinations may yield unused numbers and cause an error.
583 nigel 93 </P>
584     <P>
585     The only time that a line break is specially recognized when compiling a
586     pattern is if PCRE_EXTENDED is set, and an unescaped # outside a character
587     class is encountered. This indicates a comment that lasts until after the next
588     line break sequence. In other circumstances, line break sequences are treated
589     as literal data, except that in PCRE_EXTENDED mode, both CR and LF are treated
590     as whitespace characters and are therefore ignored.
591     </P>
592     <P>
593     The newline option that is set at compile time becomes the default that is used
594     for <b>pcre_exec()</b> and <b>pcre_dfa_exec()</b>, but it can be overridden.
595 nigel 91 <pre>
596 nigel 63 PCRE_NO_AUTO_CAPTURE
597 nigel 75 </pre>
598 nigel 63 If this option is set, it disables the use of numbered capturing parentheses in
599     the pattern. Any opening parenthesis that is not followed by ? behaves as if it
600     were followed by ?: but named parentheses can still be used for capturing (and
601     they acquire numbers in the usual way). There is no equivalent of this option
602     in Perl.
603     <pre>
604     PCRE_UNGREEDY
605 nigel 75 </pre>
606 nigel 63 This option inverts the "greediness" of the quantifiers so that they are not
607     greedy by default, but become greedy if followed by "?". It is not compatible
608     with Perl. It can also be set by a (?U) option setting within the pattern.
609     <pre>
610     PCRE_UTF8
611 nigel 75 </pre>
612 nigel 63 This option causes PCRE to regard both the pattern and the subject as strings
613     of UTF-8 characters instead of single-byte character strings. However, it is
614 nigel 75 available only when PCRE is built to include UTF-8 support. If not, the use
615 nigel 63 of this option provokes an error. Details of how this option changes the
616     behaviour of PCRE are given in the
617     <a href="pcre.html#utf8support">section on UTF-8 support</a>
618     in the main
619     <a href="pcre.html"><b>pcre</b></a>
620     page.
621 nigel 71 <pre>
622     PCRE_NO_UTF8_CHECK
623 nigel 75 </pre>
624 nigel 71 When PCRE_UTF8 is set, the validity of the pattern as a UTF-8 string is
625 ph10 211 automatically checked. There is a discussion about the
626     <a href="pcre.html#utf8strings">validity of UTF-8 strings</a>
627     in the main
628     <a href="pcre.html"><b>pcre</b></a>
629     page. If an invalid UTF-8 sequence of bytes is found, <b>pcre_compile()</b>
630     returns an error. If you already know that your pattern is valid, and you want
631     to skip this check for performance reasons, you can set the PCRE_NO_UTF8_CHECK
632     option. When it is set, the effect of passing an invalid UTF-8 string as a
633     pattern is undefined. It may cause your program to crash. Note that this option
634     can also be passed to <b>pcre_exec()</b> and <b>pcre_dfa_exec()</b>, to suppress
635     the UTF-8 validity checking of subject strings.
636 nigel 71 </P>
637 nigel 91 <br><a name="SEC8" href="#TOC1">COMPILATION ERROR CODES</a><br>
638 nigel 63 <P>
639 nigel 77 The following table lists the error codes than may be returned by
640     <b>pcre_compile2()</b>, along with the error messages that may be returned by
641 nigel 93 both compiling functions. As PCRE has developed, some error codes have fallen
642     out of use. To avoid confusion, they have not been re-used.
643 nigel 77 <pre>
644     0 no error
645     1 \ at end of pattern
646     2 \c at end of pattern
647     3 unrecognized character follows \
648     4 numbers out of order in {} quantifier
649     5 number too big in {} quantifier
650     6 missing terminating ] for character class
651     7 invalid escape sequence in character class
652     8 range out of order in character class
653     9 nothing to repeat
654 nigel 93 10 [this code is not in use]
655 nigel 77 11 internal error: unexpected repeat
656     12 unrecognized character after (?
657     13 POSIX named classes are supported only within a class
658     14 missing )
659     15 reference to non-existent subpattern
660     16 erroffset passed as NULL
661     17 unknown option bit(s) set
662     18 missing ) after comment
663 nigel 93 19 [this code is not in use]
664 nigel 77 20 regular expression too large
665     21 failed to get memory
666     22 unmatched parentheses
667     23 internal error: code overflow
668     24 unrecognized character after (?&#60;
669     25 lookbehind assertion is not fixed length
670 nigel 91 26 malformed number or name after (?(
671 nigel 77 27 conditional group contains more than two branches
672     28 assertion expected after (?(
673 ph10 182 29 (?R or (?[+-]digits must be followed by )
674 nigel 77 30 unknown POSIX class name
675     31 POSIX collating elements are not supported
676     32 this version of PCRE is not compiled with PCRE_UTF8 support
677 nigel 93 33 [this code is not in use]
678 nigel 77 34 character value in \x{...} sequence is too large
679     35 invalid condition (?(0)
680     36 \C not allowed in lookbehind assertion
681     37 PCRE does not support \L, \l, \N, \U, or \u
682     38 number after (?C is &#62; 255
683     39 closing ) for (?C expected
684     40 recursive call could loop indefinitely
685     41 unrecognized character after (?P
686 nigel 93 42 syntax error in subpattern name (missing terminator)
687 nigel 91 43 two named subpatterns have the same name
688 nigel 77 44 invalid UTF-8 string
689     45 support for \P, \p, and \X has not been compiled
690     46 malformed \P or \p sequence
691     47 unknown property name after \P or \p
692 nigel 91 48 subpattern name is too long (maximum 32 characters)
693     49 too many named subpatterns (maximum 10,000)
694 ph10 202 50 [this code is not in use]
695 nigel 91 51 octal value is greater than \377 (not in UTF-8 mode)
696 nigel 93 52 internal error: overran compiling workspace
697     53 internal error: previously-checked referenced subpattern not found
698     54 DEFINE group contains more than one branch
699     55 repeating a DEFINE group is not allowed
700     56 inconsistent NEWLINE options"
701 ph10 182 57 \g is not followed by a braced name or an optionally braced
702     non-zero number
703     58 (?+ or (?- or (?(+ or (?(- must be followed by a non-zero number
704 nigel 77 </PRE>
705     </P>
706 nigel 91 <br><a name="SEC9" href="#TOC1">STUDYING A PATTERN</a><br>
707 nigel 77 <P>
708     <b>pcre_extra *pcre_study(const pcre *<i>code</i>, int <i>options</i></b>
709 nigel 63 <b>const char **<i>errptr</i>);</b>
710     </P>
711     <P>
712 nigel 75 If a compiled pattern is going to be used several times, it is worth spending
713     more time analyzing it in order to speed up the time taken for matching. The
714 nigel 63 function <b>pcre_study()</b> takes a pointer to a compiled pattern as its first
715 nigel 75 argument. If studying the pattern produces additional information that will
716     help speed up matching, <b>pcre_study()</b> returns a pointer to a
717     <b>pcre_extra</b> block, in which the <i>study_data</i> field points to the
718     results of the study.
719 nigel 63 </P>
720     <P>
721 nigel 75 The returned value from <b>pcre_study()</b> can be passed directly to
722     <b>pcre_exec()</b>. However, a <b>pcre_extra</b> block also contains other
723 nigel 63 fields that can be set by the caller before the block is passed; these are
724 nigel 75 described
725     <a href="#extradata">below</a>
726     in the section on matching a pattern.
727 nigel 63 </P>
728     <P>
729 nigel 77 If studying the pattern does not produce any additional information
730 nigel 75 <b>pcre_study()</b> returns NULL. In that circumstance, if the calling program
731     wants to pass any of the other fields to <b>pcre_exec()</b>, it must set up its
732     own <b>pcre_extra</b> block.
733 nigel 63 </P>
734     <P>
735 nigel 75 The second argument of <b>pcre_study()</b> contains option bits. At present, no
736     options are defined, and this argument should always be zero.
737     </P>
738     <P>
739 nigel 63 The third argument for <b>pcre_study()</b> is a pointer for an error message. If
740     studying succeeds (even if no data is returned), the variable it points to is
741 nigel 87 set to NULL. Otherwise it is set to point to a textual error message. This is a
742     static string that is part of the library. You must not try to free it. You
743     should test the error pointer for NULL after calling <b>pcre_study()</b>, to be
744     sure that it has run successfully.
745 nigel 63 </P>
746     <P>
747     This is a typical call to <b>pcre_study</b>():
748     <pre>
749     pcre_extra *pe;
750     pe = pcre_study(
751     re, /* result of pcre_compile() */
752     0, /* no options exist */
753     &error); /* set to NULL or points to a message */
754 nigel 75 </pre>
755 nigel 63 At present, studying a pattern is useful only for non-anchored patterns that do
756     not have a single fixed starting character. A bitmap of possible starting
757 nigel 75 bytes is created.
758     <a name="localesupport"></a></P>
759 nigel 91 <br><a name="SEC10" href="#TOC1">LOCALE SUPPORT</a><br>
760 nigel 63 <P>
761 ph10 142 PCRE handles caseless matching, and determines whether characters are letters,
762 nigel 75 digits, or whatever, by reference to a set of tables, indexed by character
763 nigel 77 value. When running in UTF-8 mode, this applies only to characters with codes
764 nigel 75 less than 128. Higher-valued codes never match escapes such as \w or \d, but
765     can be tested with \p if PCRE is built with Unicode character property
766 ph10 142 support. The use of locales with Unicode is discouraged. If you are handling
767     characters with codes greater than 128, you should either use UTF-8 and
768     Unicode, or use locales, but not try to mix the two.
769 nigel 63 </P>
770     <P>
771 ph10 142 PCRE contains an internal set of tables that are used when the final argument
772     of <b>pcre_compile()</b> is NULL. These are sufficient for many applications.
773     Normally, the internal tables recognize only ASCII characters. However, when
774     PCRE is built, it is possible to cause the internal tables to be rebuilt in the
775     default "C" locale of the local system, which may cause them to be different.
776 nigel 63 </P>
777     <P>
778 ph10 142 The internal tables can always be overridden by tables supplied by the
779     application that calls PCRE. These may be created in a different locale from
780     the default. As more and more applications change to using Unicode, the need
781     for this locale support is expected to die away.
782     </P>
783     <P>
784 nigel 75 External tables are built by calling the <b>pcre_maketables()</b> function,
785     which has no arguments, in the relevant locale. The result can then be passed
786     to <b>pcre_compile()</b> or <b>pcre_exec()</b> as often as necessary. For
787     example, to build and use tables that are appropriate for the French locale
788     (where accented characters with values greater than 128 are treated as letters),
789     the following code could be used:
790 nigel 63 <pre>
791 nigel 75 setlocale(LC_CTYPE, "fr_FR");
792 nigel 63 tables = pcre_maketables();
793     re = pcre_compile(..., tables);
794 nigel 75 </pre>
795 ph10 142 The locale name "fr_FR" is used on Linux and other Unix-like systems; if you
796     are using Windows, the name for the French locale is "french".
797     </P>
798     <P>
799 nigel 75 When <b>pcre_maketables()</b> runs, the tables are built in memory that is
800     obtained via <b>pcre_malloc</b>. It is the caller's responsibility to ensure
801     that the memory containing the tables remains available for as long as it is
802     needed.
803 nigel 63 </P>
804     <P>
805 nigel 75 The pointer that is passed to <b>pcre_compile()</b> is saved with the compiled
806 nigel 63 pattern, and the same tables are used via this pointer by <b>pcre_study()</b>
807 nigel 75 and normally also by <b>pcre_exec()</b>. Thus, by default, for any single
808     pattern, compilation, studying and matching all happen in the same locale, but
809     different patterns can be compiled in different locales.
810 nigel 63 </P>
811     <P>
812 nigel 75 It is possible to pass a table pointer or NULL (indicating the use of the
813     internal tables) to <b>pcre_exec()</b>. Although not intended for this purpose,
814     this facility could be used to match a pattern in a different locale from the
815     one in which it was compiled. Passing table pointers at run time is discussed
816     below in the section on matching a pattern.
817     </P>
818 nigel 91 <br><a name="SEC11" href="#TOC1">INFORMATION ABOUT A PATTERN</a><br>
819 nigel 75 <P>
820 nigel 63 <b>int pcre_fullinfo(const pcre *<i>code</i>, const pcre_extra *<i>extra</i>,</b>
821     <b>int <i>what</i>, void *<i>where</i>);</b>
822     </P>
823     <P>
824     The <b>pcre_fullinfo()</b> function returns information about a compiled
825     pattern. It replaces the obsolete <b>pcre_info()</b> function, which is
826     nevertheless retained for backwards compability (and is documented below).
827     </P>
828     <P>
829     The first argument for <b>pcre_fullinfo()</b> is a pointer to the compiled
830     pattern. The second argument is the result of <b>pcre_study()</b>, or NULL if
831     the pattern was not studied. The third argument specifies which piece of
832     information is required, and the fourth argument is a pointer to a variable
833     to receive the data. The yield of the function is zero for success, or one of
834     the following negative numbers:
835     <pre>
836     PCRE_ERROR_NULL the argument <i>code</i> was NULL
837     the argument <i>where</i> was NULL
838     PCRE_ERROR_BADMAGIC the "magic number" was not found
839     PCRE_ERROR_BADOPTION the value of <i>what</i> was invalid
840 nigel 75 </pre>
841     The "magic number" is placed at the start of each compiled pattern as an simple
842     check against passing an arbitrary memory pointer. Here is a typical call of
843     <b>pcre_fullinfo()</b>, to obtain the length of the compiled pattern:
844 nigel 63 <pre>
845     int rc;
846 nigel 91 size_t length;
847 nigel 63 rc = pcre_fullinfo(
848     re, /* result of pcre_compile() */
849     pe, /* result of pcre_study(), or NULL */
850     PCRE_INFO_SIZE, /* what is required */
851     &length); /* where to put the data */
852 nigel 75 </pre>
853 nigel 63 The possible values for the third argument are defined in <b>pcre.h</b>, and are
854     as follows:
855     <pre>
856     PCRE_INFO_BACKREFMAX
857 nigel 75 </pre>
858 nigel 63 Return the number of the highest back reference in the pattern. The fourth
859     argument should point to an <b>int</b> variable. Zero is returned if there are
860     no back references.
861     <pre>
862     PCRE_INFO_CAPTURECOUNT
863 nigel 75 </pre>
864 nigel 63 Return the number of capturing subpatterns in the pattern. The fourth argument
865 nigel 75 should point to an <b>int</b> variable.
866 nigel 63 <pre>
867 nigel 77 PCRE_INFO_DEFAULT_TABLES
868 nigel 75 </pre>
869     Return a pointer to the internal default character tables within PCRE. The
870     fourth argument should point to an <b>unsigned char *</b> variable. This
871     information call is provided for internal use by the <b>pcre_study()</b>
872     function. External callers can cause PCRE to use its internal tables by passing
873     a NULL table pointer.
874     <pre>
875 nigel 63 PCRE_INFO_FIRSTBYTE
876 nigel 75 </pre>
877 nigel 63 Return information about the first byte of any matched string, for a
878 nigel 91 non-anchored pattern. The fourth argument should point to an <b>int</b>
879     variable. (This option used to be called PCRE_INFO_FIRSTCHAR; the old name is
880     still recognized for backwards compatibility.)
881 nigel 63 </P>
882     <P>
883 nigel 75 If there is a fixed first byte, for example, from a pattern such as
884 nigel 93 (cat|cow|coyote), its value is returned. Otherwise, if either
885 nigel 75 <br>
886     <br>
887 nigel 63 (a) the pattern was compiled with the PCRE_MULTILINE option, and every branch
888     starts with "^", or
889 nigel 75 <br>
890     <br>
891 nigel 63 (b) every branch of the pattern starts with ".*" and PCRE_DOTALL is not set
892     (if it were set, the pattern would be anchored),
893 nigel 75 <br>
894     <br>
895 nigel 63 -1 is returned, indicating that the pattern matches only at the start of a
896     subject string or after any newline within the string. Otherwise -2 is
897     returned. For anchored patterns, -2 is returned.
898     <pre>
899     PCRE_INFO_FIRSTTABLE
900 nigel 75 </pre>
901 nigel 63 If the pattern was studied, and this resulted in the construction of a 256-bit
902     table indicating a fixed set of bytes for the first byte in any matching
903     string, a pointer to the table is returned. Otherwise NULL is returned. The
904     fourth argument should point to an <b>unsigned char *</b> variable.
905     <pre>
906 ph10 227 PCRE_INFO_HASCRORLF
907     </pre>
908     Return 1 if the pattern contains any explicit matches for CR or LF characters,
909     otherwise 0. The fourth argument should point to an <b>int</b> variable.
910     <pre>
911 ph10 172 PCRE_INFO_JCHANGED
912     </pre>
913     Return 1 if the (?J) option setting is used in the pattern, otherwise 0. The
914     fourth argument should point to an <b>int</b> variable. The (?J) internal option
915 ph10 182 setting changes the local PCRE_DUPNAMES option.
916 ph10 172 <pre>
917 nigel 63 PCRE_INFO_LASTLITERAL
918 nigel 75 </pre>
919 nigel 65 Return the value of the rightmost literal byte that must exist in any matched
920     string, other than at its start, if such a byte has been recorded. The fourth
921     argument should point to an <b>int</b> variable. If there is no such byte, -1 is
922     returned. For anchored patterns, a last literal byte is recorded only if it
923     follows something of variable length. For example, for the pattern
924     /^a\d+z\d+/ the returned value is "z", but for /^a\dz\d/ the returned value
925     is -1.
926 nigel 63 <pre>
927     PCRE_INFO_NAMECOUNT
928     PCRE_INFO_NAMEENTRYSIZE
929     PCRE_INFO_NAMETABLE
930 nigel 75 </pre>
931 nigel 63 PCRE supports the use of named as well as numbered capturing parentheses. The
932     names are just an additional way of identifying the parentheses, which still
933 nigel 91 acquire numbers. Several convenience functions such as
934     <b>pcre_get_named_substring()</b> are provided for extracting captured
935     substrings by name. It is also possible to extract the data directly, by first
936     converting the name to a number in order to access the correct pointers in the
937     output vector (described with <b>pcre_exec()</b> below). To do the conversion,
938     you need to use the name-to-number map, which is described by these three
939     values.
940 nigel 63 </P>
941     <P>
942     The map consists of a number of fixed-size entries. PCRE_INFO_NAMECOUNT gives
943     the number of entries, and PCRE_INFO_NAMEENTRYSIZE gives the size of each
944     entry; both of these return an <b>int</b> value. The entry size depends on the
945     length of the longest name. PCRE_INFO_NAMETABLE returns a pointer to the first
946     entry of the table (a pointer to <b>char</b>). The first two bytes of each entry
947     are the number of the capturing parenthesis, most significant byte first. The
948     rest of the entry is the corresponding name, zero terminated. The names are in
949 nigel 91 alphabetical order. When PCRE_DUPNAMES is set, duplicate names are in order of
950     their parentheses numbers. For example, consider the following pattern (assume
951 nigel 63 PCRE_EXTENDED is set, so white space - including newlines - is ignored):
952     <pre>
953 nigel 93 (?&#60;date&#62; (?&#60;year&#62;(\d\d)?\d\d) - (?&#60;month&#62;\d\d) - (?&#60;day&#62;\d\d) )
954 nigel 75 </pre>
955 nigel 63 There are four named subpatterns, so the table has four entries, and each entry
956     in the table is eight bytes long. The table is as follows, with non-printing
957 nigel 75 bytes shows in hexadecimal, and undefined bytes shown as ??:
958 nigel 63 <pre>
959     00 01 d a t e 00 ??
960     00 05 d a y 00 ?? ??
961     00 04 m o n t h 00
962     00 02 y e a r 00 ??
963 nigel 75 </pre>
964     When writing code to extract data from named subpatterns using the
965 nigel 91 name-to-number map, remember that the length of the entries is likely to be
966 nigel 75 different for each compiled pattern.
967 nigel 63 <pre>
968 ph10 172 PCRE_INFO_OKPARTIAL
969     </pre>
970     Return 1 if the pattern can be used for partial matching, otherwise 0. The
971     fourth argument should point to an <b>int</b> variable. The
972     <a href="pcrepartial.html"><b>pcrepartial</b></a>
973     documentation lists the restrictions that apply to patterns when partial
974     matching is used.
975     <pre>
976 nigel 63 PCRE_INFO_OPTIONS
977 nigel 75 </pre>
978 nigel 63 Return a copy of the options with which the pattern was compiled. The fourth
979     argument should point to an <b>unsigned long int</b> variable. These option bits
980     are those specified in the call to <b>pcre_compile()</b>, modified by any
981 ph10 197 top-level option settings at the start of the pattern itself. In other words,
982     they are the options that will be in force when matching starts. For example,
983     if the pattern /(?im)abc(?-i)d/ is compiled with the PCRE_EXTENDED option, the
984     result is PCRE_CASELESS, PCRE_MULTILINE, and PCRE_EXTENDED.
985 nigel 63 </P>
986     <P>
987     A pattern is automatically anchored by PCRE if all of its top-level
988     alternatives begin with one of the following:
989     <pre>
990     ^ unless PCRE_MULTILINE is set
991     \A always
992     \G always
993 nigel 75 .* if PCRE_DOTALL is set and there are no back references to the subpattern in which .* appears
994     </pre>
995 nigel 63 For such patterns, the PCRE_ANCHORED bit is set in the options returned by
996     <b>pcre_fullinfo()</b>.
997     <pre>
998     PCRE_INFO_SIZE
999 nigel 75 </pre>
1000 nigel 63 Return the size of the compiled pattern, that is, the value that was passed as
1001     the argument to <b>pcre_malloc()</b> when PCRE was getting memory in which to
1002     place the compiled data. The fourth argument should point to a <b>size_t</b>
1003     variable.
1004     <pre>
1005     PCRE_INFO_STUDYSIZE
1006 nigel 75 </pre>
1007     Return the size of the data block pointed to by the <i>study_data</i> field in
1008 nigel 63 a <b>pcre_extra</b> block. That is, it is the value that was passed to
1009     <b>pcre_malloc()</b> when PCRE was getting memory into which to place the data
1010     created by <b>pcre_study()</b>. The fourth argument should point to a
1011     <b>size_t</b> variable.
1012     </P>
1013 nigel 91 <br><a name="SEC12" href="#TOC1">OBSOLETE INFO FUNCTION</a><br>
1014 nigel 63 <P>
1015     <b>int pcre_info(const pcre *<i>code</i>, int *<i>optptr</i>, int</b>
1016     <b>*<i>firstcharptr</i>);</b>
1017     </P>
1018     <P>
1019     The <b>pcre_info()</b> function is now obsolete because its interface is too
1020     restrictive to return all the available data about a compiled pattern. New
1021     programs should use <b>pcre_fullinfo()</b> instead. The yield of
1022     <b>pcre_info()</b> is the number of capturing subpatterns, or one of the
1023     following negative numbers:
1024     <pre>
1025     PCRE_ERROR_NULL the argument <i>code</i> was NULL
1026     PCRE_ERROR_BADMAGIC the "magic number" was not found
1027 nigel 75 </pre>
1028 nigel 63 If the <i>optptr</i> argument is not NULL, a copy of the options with which the
1029     pattern was compiled is placed in the integer it points to (see
1030     PCRE_INFO_OPTIONS above).
1031     </P>
1032     <P>
1033     If the pattern is not anchored and the <i>firstcharptr</i> argument is not NULL,
1034     it is used to pass back information about the first character of any matched
1035     string (see PCRE_INFO_FIRSTBYTE above).
1036     </P>
1037 nigel 91 <br><a name="SEC13" href="#TOC1">REFERENCE COUNTS</a><br>
1038 nigel 63 <P>
1039 nigel 77 <b>int pcre_refcount(pcre *<i>code</i>, int <i>adjust</i>);</b>
1040     </P>
1041     <P>
1042     The <b>pcre_refcount()</b> function is used to maintain a reference count in the
1043     data block that contains a compiled pattern. It is provided for the benefit of
1044     applications that operate in an object-oriented manner, where different parts
1045     of the application may be using the same compiled pattern, but you want to free
1046     the block when they are all done.
1047     </P>
1048     <P>
1049     When a pattern is compiled, the reference count field is initialized to zero.
1050     It is changed only by calling this function, whose action is to add the
1051     <i>adjust</i> value (which may be positive or negative) to it. The yield of the
1052     function is the new value. However, the value of the count is constrained to
1053     lie between 0 and 65535, inclusive. If the new value is outside these limits,
1054     it is forced to the appropriate limit value.
1055     </P>
1056     <P>
1057     Except when it is zero, the reference count is not correctly preserved if a
1058     pattern is compiled on one host and then transferred to a host whose byte-order
1059     is different. (This seems a highly unlikely scenario.)
1060     </P>
1061 nigel 91 <br><a name="SEC14" href="#TOC1">MATCHING A PATTERN: THE TRADITIONAL FUNCTION</a><br>
1062 nigel 77 <P>
1063 nigel 63 <b>int pcre_exec(const pcre *<i>code</i>, const pcre_extra *<i>extra</i>,</b>
1064     <b>const char *<i>subject</i>, int <i>length</i>, int <i>startoffset</i>,</b>
1065     <b>int <i>options</i>, int *<i>ovector</i>, int <i>ovecsize</i>);</b>
1066     </P>
1067     <P>
1068     The function <b>pcre_exec()</b> is called to match a subject string against a
1069 nigel 75 compiled pattern, which is passed in the <i>code</i> argument. If the
1070 nigel 63 pattern has been studied, the result of the study should be passed in the
1071 nigel 77 <i>extra</i> argument. This function is the main matching facility of the
1072     library, and it operates in a Perl-like manner. For specialist use there is
1073     also an alternative matching function, which is described
1074     <a href="#dfamatch">below</a>
1075     in the section about the <b>pcre_dfa_exec()</b> function.
1076 nigel 63 </P>
1077     <P>
1078 nigel 75 In most applications, the pattern will have been compiled (and optionally
1079     studied) in the same process that calls <b>pcre_exec()</b>. However, it is
1080     possible to save compiled patterns and study data, and then use them later
1081     in different processes, possibly even on different hosts. For a discussion
1082     about this, see the
1083     <a href="pcreprecompile.html"><b>pcreprecompile</b></a>
1084     documentation.
1085 nigel 63 </P>
1086     <P>
1087 nigel 75 Here is an example of a simple call to <b>pcre_exec()</b>:
1088 nigel 63 <pre>
1089     int rc;
1090     int ovector[30];
1091     rc = pcre_exec(
1092     re, /* result of pcre_compile() */
1093     NULL, /* we didn't study the pattern */
1094     "some string", /* the subject string */
1095     11, /* the length of the subject string */
1096     0, /* start at offset 0 in the subject */
1097     0, /* default options */
1098 nigel 75 ovector, /* vector of integers for substring information */
1099 nigel 77 30); /* number of elements (NOT size in bytes) */
1100 nigel 75 <a name="extradata"></a></PRE>
1101 nigel 63 </P>
1102 nigel 75 <br><b>
1103     Extra data for <b>pcre_exec()</b>
1104     </b><br>
1105 nigel 63 <P>
1106     If the <i>extra</i> argument is not NULL, it must point to a <b>pcre_extra</b>
1107     data block. The <b>pcre_study()</b> function returns such a block (when it
1108     doesn't return NULL), but you can also create one for yourself, and pass
1109 nigel 87 additional information in it. The <b>pcre_extra</b> block contains the following
1110     fields (not necessarily in this order):
1111 nigel 63 <pre>
1112     unsigned long int <i>flags</i>;
1113     void *<i>study_data</i>;
1114     unsigned long int <i>match_limit</i>;
1115 nigel 87 unsigned long int <i>match_limit_recursion</i>;
1116 nigel 63 void *<i>callout_data</i>;
1117 nigel 75 const unsigned char *<i>tables</i>;
1118     </pre>
1119 nigel 63 The <i>flags</i> field is a bitmap that specifies which of the other fields
1120     are set. The flag bits are:
1121     <pre>
1122     PCRE_EXTRA_STUDY_DATA
1123     PCRE_EXTRA_MATCH_LIMIT
1124 nigel 87 PCRE_EXTRA_MATCH_LIMIT_RECURSION
1125 nigel 63 PCRE_EXTRA_CALLOUT_DATA
1126 nigel 75 PCRE_EXTRA_TABLES
1127     </pre>
1128 nigel 63 Other flag bits should be set to zero. The <i>study_data</i> field is set in the
1129     <b>pcre_extra</b> block that is returned by <b>pcre_study()</b>, together with
1130 nigel 75 the appropriate flag bit. You should not set this yourself, but you may add to
1131     the block by setting the other fields and their corresponding flag bits.
1132 nigel 63 </P>
1133     <P>
1134     The <i>match_limit</i> field provides a means of preventing PCRE from using up a
1135     vast amount of resources when running patterns that are not going to match,
1136     but which have a very large number of possibilities in their search trees. The
1137 nigel 75 classic example is the use of nested unlimited repeats.
1138 nigel 63 </P>
1139     <P>
1140 nigel 75 Internally, PCRE uses a function called <b>match()</b> which it calls repeatedly
1141 nigel 87 (sometimes recursively). The limit set by <i>match_limit</i> is imposed on the
1142     number of times this function is called during a match, which has the effect of
1143     limiting the amount of backtracking that can take place. For patterns that are
1144     not anchored, the count restarts from zero for each position in the subject
1145     string.
1146 nigel 75 </P>
1147     <P>
1148 nigel 87 The default value for the limit can be set when PCRE is built; the default
1149 nigel 63 default is 10 million, which handles all but the most extreme cases. You can
1150 nigel 87 override the default by suppling <b>pcre_exec()</b> with a <b>pcre_extra</b>
1151     block in which <i>match_limit</i> is set, and PCRE_EXTRA_MATCH_LIMIT is set in
1152     the <i>flags</i> field. If the limit is exceeded, <b>pcre_exec()</b> returns
1153     PCRE_ERROR_MATCHLIMIT.
1154 nigel 63 </P>
1155     <P>
1156 nigel 87 The <i>match_limit_recursion</i> field is similar to <i>match_limit</i>, but
1157     instead of limiting the total number of times that <b>match()</b> is called, it
1158     limits the depth of recursion. The recursion depth is a smaller number than the
1159     total number of calls, because not all calls to <b>match()</b> are recursive.
1160     This limit is of use only if it is set smaller than <i>match_limit</i>.
1161     </P>
1162     <P>
1163     Limiting the recursion depth limits the amount of stack that can be used, or,
1164     when PCRE has been compiled to use memory on the heap instead of the stack, the
1165     amount of heap memory that can be used.
1166     </P>
1167     <P>
1168     The default value for <i>match_limit_recursion</i> can be set when PCRE is
1169     built; the default default is the same value as the default for
1170     <i>match_limit</i>. You can override the default by suppling <b>pcre_exec()</b>
1171     with a <b>pcre_extra</b> block in which <i>match_limit_recursion</i> is set, and
1172     PCRE_EXTRA_MATCH_LIMIT_RECURSION is set in the <i>flags</i> field. If the limit
1173     is exceeded, <b>pcre_exec()</b> returns PCRE_ERROR_RECURSIONLIMIT.
1174     </P>
1175     <P>
1176 nigel 63 The <i>pcre_callout</i> field is used in conjunction with the "callout" feature,
1177 nigel 75 which is described in the
1178     <a href="pcrecallout.html"><b>pcrecallout</b></a>
1179     documentation.
1180 nigel 63 </P>
1181     <P>
1182 nigel 75 The <i>tables</i> field is used to pass a character tables pointer to
1183     <b>pcre_exec()</b>; this overrides the value that is stored with the compiled
1184     pattern. A non-NULL value is stored with the compiled pattern only if custom
1185     tables were supplied to <b>pcre_compile()</b> via its <i>tableptr</i> argument.
1186     If NULL is passed to <b>pcre_exec()</b> using this mechanism, it forces PCRE's
1187     internal tables to be used. This facility is helpful when re-using patterns
1188     that have been saved after compiling with an external set of tables, because
1189     the external tables might be at a different address when <b>pcre_exec()</b> is
1190     called. See the
1191     <a href="pcreprecompile.html"><b>pcreprecompile</b></a>
1192     documentation for a discussion of saving compiled patterns for later use.
1193 ph10 227 <a name="execoptions"></a></P>
1194 nigel 75 <br><b>
1195     Option bits for <b>pcre_exec()</b>
1196     </b><br>
1197 nigel 63 <P>
1198 nigel 75 The unused bits of the <i>options</i> argument for <b>pcre_exec()</b> must be
1199 nigel 91 zero. The only bits that may be set are PCRE_ANCHORED, PCRE_NEWLINE_<i>xxx</i>,
1200     PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY, PCRE_NO_UTF8_CHECK and PCRE_PARTIAL.
1201 nigel 63 <pre>
1202 nigel 75 PCRE_ANCHORED
1203     </pre>
1204     The PCRE_ANCHORED option limits <b>pcre_exec()</b> to matching at the first
1205     matching position. If a pattern was compiled with PCRE_ANCHORED, or turned out
1206     to be anchored by virtue of its contents, it cannot be made unachored at
1207     matching time.
1208     <pre>
1209 nigel 91 PCRE_NEWLINE_CR
1210     PCRE_NEWLINE_LF
1211     PCRE_NEWLINE_CRLF
1212 ph10 150 PCRE_NEWLINE_ANYCRLF
1213 nigel 93 PCRE_NEWLINE_ANY
1214 nigel 91 </pre>
1215     These options override the newline definition that was chosen or defaulted when
1216 nigel 93 the pattern was compiled. For details, see the description of
1217     <b>pcre_compile()</b> above. During matching, the newline choice affects the
1218     behaviour of the dot, circumflex, and dollar metacharacters. It may also alter
1219     the way the match position is advanced after a match failure for an unanchored
1220 ph10 227 pattern.
1221     </P>
1222     <P>
1223     When PCRE_NEWLINE_CRLF, PCRE_NEWLINE_ANYCRLF, or PCRE_NEWLINE_ANY is set, and a
1224     match attempt for an unanchored pattern fails when the current position is at a
1225     CRLF sequence, and the pattern contains no explicit matches for CR or NL
1226     characters, the match position is advanced by two characters instead of one, in
1227     other words, to after the CRLF.
1228     </P>
1229     <P>
1230     The above rule is a compromise that makes the most common cases work as
1231     expected. For example, if the pattern is .+A (and the PCRE_DOTALL option is not
1232     set), it does not match the string "\r\nA" because, after failing at the
1233     start, it skips both the CR and the LF before retrying. However, the pattern
1234     [\r\n]A does match that string, because it contains an explicit CR or LF
1235     reference, and so advances only by one character after the first failure.
1236     Note than an explicit CR or LF reference occurs for negated character classes
1237     such as [^X] because they can match CR or LF characters.
1238     </P>
1239     <P>
1240     Notwithstanding the above, anomalous effects may still occur when CRLF is a
1241     valid newline sequence and explicit \r or \n escapes appear in the pattern.
1242 nigel 91 <pre>
1243 nigel 63 PCRE_NOTBOL
1244 nigel 75 </pre>
1245     This option specifies that first character of the subject string is not the
1246     beginning of a line, so the circumflex metacharacter should not match before
1247     it. Setting this without PCRE_MULTILINE (at compile time) causes circumflex
1248     never to match. This option affects only the behaviour of the circumflex
1249     metacharacter. It does not affect \A.
1250 nigel 63 <pre>
1251     PCRE_NOTEOL
1252 nigel 75 </pre>
1253     This option specifies that the end of the subject string is not the end of a
1254     line, so the dollar metacharacter should not match it nor (except in multiline
1255     mode) a newline immediately before it. Setting this without PCRE_MULTILINE (at
1256     compile time) causes dollar never to match. This option affects only the
1257     behaviour of the dollar metacharacter. It does not affect \Z or \z.
1258 nigel 63 <pre>
1259     PCRE_NOTEMPTY
1260 nigel 75 </pre>
1261 nigel 63 An empty string is not considered to be a valid match if this option is set. If
1262     there are alternatives in the pattern, they are tried. If all the alternatives
1263     match the empty string, the entire match fails. For example, if the pattern
1264     <pre>
1265     a?b?
1266 nigel 75 </pre>
1267 nigel 63 is applied to a string not beginning with "a" or "b", it matches the empty
1268     string at the start of the subject. With PCRE_NOTEMPTY set, this match is not
1269     valid, so PCRE searches further into the string for occurrences of "a" or "b".
1270     </P>
1271     <P>
1272     Perl has no direct equivalent of PCRE_NOTEMPTY, but it does make a special case
1273     of a pattern match of the empty string within its <b>split()</b> function, and
1274     when using the /g modifier. It is possible to emulate Perl's behaviour after
1275     matching a null string by first trying the match again at the same offset with
1276 nigel 75 PCRE_NOTEMPTY and PCRE_ANCHORED, and then if that fails by advancing the
1277     starting offset (see below) and trying an ordinary match again. There is some
1278     code that demonstrates how to do this in the <i>pcredemo.c</i> sample program.
1279     <pre>
1280     PCRE_NO_UTF8_CHECK
1281     </pre>
1282     When PCRE_UTF8 is set at compile time, the validity of the subject as a UTF-8
1283     string is automatically checked when <b>pcre_exec()</b> is subsequently called.
1284     The value of <i>startoffset</i> is also checked to ensure that it points to the
1285 ph10 211 start of a UTF-8 character. There is a discussion about the validity of UTF-8
1286     strings in the
1287     <a href="pcre.html#utf8strings">section on UTF-8 support</a>
1288     in the main
1289     <a href="pcre.html"><b>pcre</b></a>
1290     page. If an invalid UTF-8 sequence of bytes is found, <b>pcre_exec()</b> returns
1291     the error PCRE_ERROR_BADUTF8. If <i>startoffset</i> contains an invalid value,
1292     PCRE_ERROR_BADUTF8_OFFSET is returned.
1293 nigel 63 </P>
1294     <P>
1295 nigel 75 If you already know that your subject is valid, and you want to skip these
1296     checks for performance reasons, you can set the PCRE_NO_UTF8_CHECK option when
1297     calling <b>pcre_exec()</b>. You might want to do this for the second and
1298     subsequent calls to <b>pcre_exec()</b> if you are making repeated calls to find
1299     all the matches in a single subject string. However, you should be sure that
1300     the value of <i>startoffset</i> points to the start of a UTF-8 character. When
1301     PCRE_NO_UTF8_CHECK is set, the effect of passing an invalid UTF-8 string as a
1302     subject, or a value of <i>startoffset</i> that does not point to the start of a
1303     UTF-8 character, is undefined. Your program may crash.
1304     <pre>
1305     PCRE_PARTIAL
1306     </pre>
1307     This option turns on the partial matching feature. If the subject string fails
1308     to match the pattern, but at some point during the matching process the end of
1309     the subject was reached (that is, the subject partially matches the pattern and
1310     the failure to match occurred only because there were not enough subject
1311     characters), <b>pcre_exec()</b> returns PCRE_ERROR_PARTIAL instead of
1312     PCRE_ERROR_NOMATCH. When PCRE_PARTIAL is used, there are restrictions on what
1313     may appear in the pattern. These are discussed in the
1314     <a href="pcrepartial.html"><b>pcrepartial</b></a>
1315     documentation.
1316     </P>
1317     <br><b>
1318     The string to be matched by <b>pcre_exec()</b>
1319     </b><br>
1320     <P>
1321 nigel 63 The subject string is passed to <b>pcre_exec()</b> as a pointer in
1322 nigel 73 <i>subject</i>, a length in <i>length</i>, and a starting byte offset in
1323 nigel 75 <i>startoffset</i>. In UTF-8 mode, the byte offset must point to the start of a
1324     UTF-8 character. Unlike the pattern string, the subject may contain binary zero
1325     bytes. When the starting offset is zero, the search for a match starts at the
1326     beginning of the subject, and this is by far the most common case.
1327 nigel 63 </P>
1328     <P>
1329     A non-zero starting offset is useful when searching for another match in the
1330     same subject by calling <b>pcre_exec()</b> again after a previous success.
1331     Setting <i>startoffset</i> differs from just passing over a shortened string and
1332     setting PCRE_NOTBOL in the case of a pattern that begins with any kind of
1333     lookbehind. For example, consider the pattern
1334     <pre>
1335     \Biss\B
1336 nigel 75 </pre>
1337 nigel 63 which finds occurrences of "iss" in the middle of words. (\B matches only if
1338     the current position in the subject is not a word boundary.) When applied to
1339     the string "Mississipi" the first call to <b>pcre_exec()</b> finds the first
1340     occurrence. If <b>pcre_exec()</b> is called again with just the remainder of the
1341     subject, namely "issipi", it does not match, because \B is always false at the
1342     start of the subject, which is deemed to be a word boundary. However, if
1343     <b>pcre_exec()</b> is passed the entire string again, but with <i>startoffset</i>
1344     set to 4, it finds the second occurrence of "iss" because it is able to look
1345     behind the starting point to discover that it is preceded by a letter.
1346     </P>
1347     <P>
1348     If a non-zero starting offset is passed when the pattern is anchored, one
1349 nigel 75 attempt to match at the given offset is made. This can only succeed if the
1350 nigel 63 pattern does not require the match to be at the start of the subject.
1351     </P>
1352 nigel 75 <br><b>
1353     How <b>pcre_exec()</b> returns captured substrings
1354     </b><br>
1355 nigel 63 <P>
1356     In general, a pattern matches a certain portion of the subject, and in
1357     addition, further substrings from the subject may be picked out by parts of the
1358     pattern. Following the usage in Jeffrey Friedl's book, this is called
1359     "capturing" in what follows, and the phrase "capturing subpattern" is used for
1360     a fragment of a pattern that picks out a substring. PCRE supports several other
1361     kinds of parenthesized subpattern that do not cause substrings to be captured.
1362     </P>
1363     <P>
1364     Captured substrings are returned to the caller via a vector of integer offsets
1365     whose address is passed in <i>ovector</i>. The number of elements in the vector
1366 nigel 75 is passed in <i>ovecsize</i>, which must be a non-negative number. <b>Note</b>:
1367     this argument is NOT the size of <i>ovector</i> in bytes.
1368 nigel 63 </P>
1369     <P>
1370 nigel 75 The first two-thirds of the vector is used to pass back captured substrings,
1371     each substring using a pair of integers. The remaining third of the vector is
1372     used as workspace by <b>pcre_exec()</b> while matching capturing subpatterns,
1373     and is not available for passing back information. The length passed in
1374     <i>ovecsize</i> should always be a multiple of three. If it is not, it is
1375     rounded down.
1376     </P>
1377     <P>
1378     When a match is successful, information about captured substrings is returned
1379     in pairs of integers, starting at the beginning of <i>ovector</i>, and
1380 nigel 63 continuing up to two-thirds of its length at the most. The first element of a
1381     pair is set to the offset of the first character in a substring, and the second
1382     is set to the offset of the first character after the end of a substring. The
1383     first pair, <i>ovector[0]</i> and <i>ovector[1]</i>, identify the portion of the
1384     subject string matched by the entire pattern. The next pair is used for the
1385     first capturing subpattern, and so on. The value returned by <b>pcre_exec()</b>
1386 nigel 91 is one more than the highest numbered pair that has been set. For example, if
1387     two substrings have been captured, the returned value is 3. If there are no
1388     capturing subpatterns, the return value from a successful match is 1,
1389     indicating that just the first pair of offsets has been set.
1390 nigel 63 </P>
1391     <P>
1392     If a capturing subpattern is matched repeatedly, it is the last portion of the
1393 nigel 75 string that it matched that is returned.
1394 nigel 63 </P>
1395     <P>
1396 nigel 75 If the vector is too small to hold all the captured substring offsets, it is
1397     used as far as possible (up to two-thirds of its length), and the function
1398     returns a value of zero. In particular, if the substring offsets are not of
1399     interest, <b>pcre_exec()</b> may be called with <i>ovector</i> passed as NULL and
1400 nigel 63 <i>ovecsize</i> as zero. However, if the pattern contains back references and
1401 nigel 75 the <i>ovector</i> is not big enough to remember the related substrings, PCRE
1402     has to get additional memory for use during matching. Thus it is usually
1403     advisable to supply an <i>ovector</i>.
1404 nigel 63 </P>
1405     <P>
1406 nigel 91 The <b>pcre_info()</b> function can be used to find out how many capturing
1407 nigel 63 subpatterns there are in a compiled pattern. The smallest size for
1408     <i>ovector</i> that will allow for <i>n</i> captured substrings, in addition to
1409     the offsets of the substring matched by the whole pattern, is (<i>n</i>+1)*3.
1410 nigel 91 </P>
1411     <P>
1412     It is possible for capturing subpattern number <i>n+1</i> to match some part of
1413     the subject when subpattern <i>n</i> has not been used at all. For example, if
1414     the string "abc" is matched against the pattern (a|(z))(bc) the return from the
1415     function is 4, and subpatterns 1 and 3 are matched, but 2 is not. When this
1416     happens, both values in the offset pairs corresponding to unused subpatterns
1417     are set to -1.
1418     </P>
1419     <P>
1420     Offset values that correspond to unused subpatterns at the end of the
1421     expression are also set to -1. For example, if the string "abc" is matched
1422     against the pattern (abc)(x(yz)?)? subpatterns 2 and 3 are not matched. The
1423     return from the function is 2, because the highest used capturing subpattern
1424     number is 1. However, you can refer to the offsets for the second and third
1425     capturing subpatterns if you wish (assuming the vector is large enough, of
1426     course).
1427     </P>
1428     <P>
1429     Some convenience functions are provided for extracting the captured substrings
1430     as separate strings. These are described below.
1431 nigel 77 <a name="errorlist"></a></P>
1432 nigel 75 <br><b>
1433 nigel 91 Error return values from <b>pcre_exec()</b>
1434 nigel 75 </b><br>
1435 nigel 63 <P>
1436     If <b>pcre_exec()</b> fails, it returns a negative number. The following are
1437     defined in the header file:
1438     <pre>
1439     PCRE_ERROR_NOMATCH (-1)
1440 nigel 75 </pre>
1441 nigel 63 The subject string did not match the pattern.
1442     <pre>
1443     PCRE_ERROR_NULL (-2)
1444 nigel 75 </pre>
1445 nigel 63 Either <i>code</i> or <i>subject</i> was passed as NULL, or <i>ovector</i> was
1446     NULL and <i>ovecsize</i> was not zero.
1447     <pre>
1448     PCRE_ERROR_BADOPTION (-3)
1449 nigel 75 </pre>
1450 nigel 63 An unrecognized bit was set in the <i>options</i> argument.
1451     <pre>
1452     PCRE_ERROR_BADMAGIC (-4)
1453 nigel 75 </pre>
1454 nigel 63 PCRE stores a 4-byte "magic number" at the start of the compiled code, to catch
1455 nigel 75 the case when it is passed a junk pointer and to detect when a pattern that was
1456     compiled in an environment of one endianness is run in an environment with the
1457     other endianness. This is the error that PCRE gives when the magic number is
1458     not present.
1459 nigel 63 <pre>
1460 nigel 93 PCRE_ERROR_UNKNOWN_OPCODE (-5)
1461 nigel 75 </pre>
1462 nigel 63 While running the pattern match, an unknown item was encountered in the
1463     compiled pattern. This error could be caused by a bug in PCRE or by overwriting
1464     of the compiled pattern.
1465     <pre>
1466     PCRE_ERROR_NOMEMORY (-6)
1467 nigel 75 </pre>
1468 nigel 63 If a pattern contains back references, but the <i>ovector</i> that is passed to
1469     <b>pcre_exec()</b> is not big enough to remember the referenced substrings, PCRE
1470     gets a block of memory at the start of matching to use for this purpose. If the
1471 nigel 75 call via <b>pcre_malloc()</b> fails, this error is given. The memory is
1472     automatically freed at the end of matching.
1473 nigel 63 <pre>
1474     PCRE_ERROR_NOSUBSTRING (-7)
1475 nigel 75 </pre>
1476 nigel 63 This error is used by the <b>pcre_copy_substring()</b>,
1477     <b>pcre_get_substring()</b>, and <b>pcre_get_substring_list()</b> functions (see
1478     below). It is never returned by <b>pcre_exec()</b>.
1479     <pre>
1480     PCRE_ERROR_MATCHLIMIT (-8)
1481 nigel 75 </pre>
1482 nigel 87 The backtracking limit, as specified by the <i>match_limit</i> field in a
1483     <b>pcre_extra</b> structure (or defaulted) was reached. See the description
1484     above.
1485     <pre>
1486 nigel 63 PCRE_ERROR_CALLOUT (-9)
1487 nigel 75 </pre>
1488 nigel 63 This error is never generated by <b>pcre_exec()</b> itself. It is provided for
1489     use by callout functions that want to yield a distinctive error code. See the
1490 nigel 75 <a href="pcrecallout.html"><b>pcrecallout</b></a>
1491     documentation for details.
1492 nigel 71 <pre>
1493 nigel 73 PCRE_ERROR_BADUTF8 (-10)
1494 nigel 75 </pre>
1495 nigel 71 A string that contains an invalid UTF-8 byte sequence was passed as a subject.
1496 nigel 73 <pre>
1497     PCRE_ERROR_BADUTF8_OFFSET (-11)
1498 nigel 75 </pre>
1499 nigel 73 The UTF-8 byte sequence that was passed as a subject was valid, but the value
1500     of <i>startoffset</i> did not point to the beginning of a UTF-8 character.
1501 nigel 75 <pre>
1502 nigel 77 PCRE_ERROR_PARTIAL (-12)
1503 nigel 75 </pre>
1504     The subject string did not match, but it did match partially. See the
1505     <a href="pcrepartial.html"><b>pcrepartial</b></a>
1506     documentation for details of partial matching.
1507     <pre>
1508 nigel 77 PCRE_ERROR_BADPARTIAL (-13)
1509 nigel 75 </pre>
1510     The PCRE_PARTIAL option was used with a compiled pattern containing items that
1511     are not supported for partial matching. See the
1512     <a href="pcrepartial.html"><b>pcrepartial</b></a>
1513     documentation for details of partial matching.
1514     <pre>
1515 nigel 77 PCRE_ERROR_INTERNAL (-14)
1516 nigel 75 </pre>
1517     An unexpected internal error has occurred. This error could be caused by a bug
1518     in PCRE or by overwriting of the compiled pattern.
1519     <pre>
1520 nigel 77 PCRE_ERROR_BADCOUNT (-15)
1521 nigel 75 </pre>
1522     This error is given if the value of the <i>ovecsize</i> argument is negative.
1523 nigel 93 <pre>
1524     PCRE_ERROR_RECURSIONLIMIT (-21)
1525     </pre>
1526     The internal recursion limit, as specified by the <i>match_limit_recursion</i>
1527     field in a <b>pcre_extra</b> structure (or defaulted) was reached. See the
1528     description above.
1529     <pre>
1530     PCRE_ERROR_BADNEWLINE (-23)
1531     </pre>
1532     An invalid combination of PCRE_NEWLINE_<i>xxx</i> options was given.
1533 nigel 73 </P>
1534 nigel 93 <P>
1535 ph10 197 Error numbers -16 to -20 and -22 are not used by <b>pcre_exec()</b>.
1536 nigel 93 </P>
1537 nigel 91 <br><a name="SEC15" href="#TOC1">EXTRACTING CAPTURED SUBSTRINGS BY NUMBER</a><br>
1538 nigel 63 <P>
1539     <b>int pcre_copy_substring(const char *<i>subject</i>, int *<i>ovector</i>,</b>
1540     <b>int <i>stringcount</i>, int <i>stringnumber</i>, char *<i>buffer</i>,</b>
1541     <b>int <i>buffersize</i>);</b>
1542     </P>
1543     <P>
1544     <b>int pcre_get_substring(const char *<i>subject</i>, int *<i>ovector</i>,</b>
1545     <b>int <i>stringcount</i>, int <i>stringnumber</i>,</b>
1546     <b>const char **<i>stringptr</i>);</b>
1547     </P>
1548     <P>
1549     <b>int pcre_get_substring_list(const char *<i>subject</i>,</b>
1550     <b>int *<i>ovector</i>, int <i>stringcount</i>, const char ***<i>listptr</i>);</b>
1551     </P>
1552     <P>
1553     Captured substrings can be accessed directly by using the offsets returned by
1554     <b>pcre_exec()</b> in <i>ovector</i>. For convenience, the functions
1555     <b>pcre_copy_substring()</b>, <b>pcre_get_substring()</b>, and
1556     <b>pcre_get_substring_list()</b> are provided for extracting captured substrings
1557     as new, separate, zero-terminated strings. These functions identify substrings
1558     by number. The next section describes functions for extracting named
1559 nigel 91 substrings.
1560 nigel 63 </P>
1561     <P>
1562 nigel 91 A substring that contains a binary zero is correctly extracted and has a
1563     further zero added on the end, but the result is not, of course, a C string.
1564     However, you can process such a string by referring to the length that is
1565     returned by <b>pcre_copy_substring()</b> and <b>pcre_get_substring()</b>.
1566     Unfortunately, the interface to <b>pcre_get_substring_list()</b> is not adequate
1567     for handling strings containing binary zeros, because the end of the final
1568     string is not independently indicated.
1569     </P>
1570     <P>
1571 nigel 63 The first three arguments are the same for all three of these functions:
1572 nigel 75 <i>subject</i> is the subject string that has just been successfully matched,
1573 nigel 63 <i>ovector</i> is a pointer to the vector of integer offsets that was passed to
1574     <b>pcre_exec()</b>, and <i>stringcount</i> is the number of substrings that were
1575     captured by the match, including the substring that matched the entire regular
1576 nigel 75 expression. This is the value returned by <b>pcre_exec()</b> if it is greater
1577     than zero. If <b>pcre_exec()</b> returned zero, indicating that it ran out of
1578     space in <i>ovector</i>, the value passed as <i>stringcount</i> should be the
1579     number of elements in the vector divided by three.
1580 nigel 63 </P>
1581     <P>
1582     The functions <b>pcre_copy_substring()</b> and <b>pcre_get_substring()</b>
1583     extract a single substring, whose number is given as <i>stringnumber</i>. A
1584 nigel 75 value of zero extracts the substring that matched the entire pattern, whereas
1585 nigel 63 higher values extract the captured substrings. For <b>pcre_copy_substring()</b>,
1586     the string is placed in <i>buffer</i>, whose length is given by
1587     <i>buffersize</i>, while for <b>pcre_get_substring()</b> a new block of memory is
1588     obtained via <b>pcre_malloc</b>, and its address is returned via
1589     <i>stringptr</i>. The yield of the function is the length of the string, not
1590 nigel 93 including the terminating zero, or one of these error codes:
1591 nigel 63 <pre>
1592     PCRE_ERROR_NOMEMORY (-6)
1593 nigel 75 </pre>
1594 nigel 63 The buffer was too small for <b>pcre_copy_substring()</b>, or the attempt to get
1595     memory failed for <b>pcre_get_substring()</b>.
1596     <pre>
1597     PCRE_ERROR_NOSUBSTRING (-7)
1598 nigel 75 </pre>
1599 nigel 63 There is no substring whose number is <i>stringnumber</i>.
1600     </P>
1601     <P>
1602     The <b>pcre_get_substring_list()</b> function extracts all available substrings
1603     and builds a list of pointers to them. All this is done in a single block of
1604 nigel 75 memory that is obtained via <b>pcre_malloc</b>. The address of the memory block
1605 nigel 63 is returned via <i>listptr</i>, which is also the start of the list of string
1606     pointers. The end of the list is marked by a NULL pointer. The yield of the
1607 nigel 93 function is zero if all went well, or the error code
1608 nigel 63 <pre>
1609     PCRE_ERROR_NOMEMORY (-6)
1610 nigel 75 </pre>
1611 nigel 63 if the attempt to get the memory block failed.
1612     </P>
1613     <P>
1614     When any of these functions encounter a substring that is unset, which can
1615     happen when capturing subpattern number <i>n+1</i> matches some part of the
1616     subject, but subpattern <i>n</i> has not been used at all, they return an empty
1617     string. This can be distinguished from a genuine zero-length substring by
1618     inspecting the appropriate offset in <i>ovector</i>, which is negative for unset
1619     substrings.
1620     </P>
1621     <P>
1622     The two convenience functions <b>pcre_free_substring()</b> and
1623     <b>pcre_free_substring_list()</b> can be used to free the memory returned by
1624     a previous call of <b>pcre_get_substring()</b> or
1625     <b>pcre_get_substring_list()</b>, respectively. They do nothing more than call
1626     the function pointed to by <b>pcre_free</b>, which of course could be called
1627     directly from a C program. However, PCRE is used in some situations where it is
1628 nigel 91 linked via a special interface to another programming language that cannot use
1629 nigel 63 <b>pcre_free</b> directly; it is for these cases that the functions are
1630     provided.
1631     </P>
1632 nigel 91 <br><a name="SEC16" href="#TOC1">EXTRACTING CAPTURED SUBSTRINGS BY NAME</a><br>
1633 nigel 63 <P>
1634 nigel 75 <b>int pcre_get_stringnumber(const pcre *<i>code</i>,</b>
1635     <b>const char *<i>name</i>);</b>
1636     </P>
1637     <P>
1638 nigel 63 <b>int pcre_copy_named_substring(const pcre *<i>code</i>,</b>
1639     <b>const char *<i>subject</i>, int *<i>ovector</i>,</b>
1640     <b>int <i>stringcount</i>, const char *<i>stringname</i>,</b>
1641     <b>char *<i>buffer</i>, int <i>buffersize</i>);</b>
1642     </P>
1643     <P>
1644     <b>int pcre_get_named_substring(const pcre *<i>code</i>,</b>
1645     <b>const char *<i>subject</i>, int *<i>ovector</i>,</b>
1646     <b>int <i>stringcount</i>, const char *<i>stringname</i>,</b>
1647     <b>const char **<i>stringptr</i>);</b>
1648     </P>
1649     <P>
1650 nigel 75 To extract a substring by name, you first have to find associated number.
1651     For example, for this pattern
1652 nigel 63 <pre>
1653 nigel 93 (a+)b(?&#60;xxx&#62;\d+)...
1654 nigel 75 </pre>
1655 nigel 91 the number of the subpattern called "xxx" is 2. If the name is known to be
1656     unique (PCRE_DUPNAMES was not set), you can find the number from the name by
1657     calling <b>pcre_get_stringnumber()</b>. The first argument is the compiled
1658     pattern, and the second is the name. The yield of the function is the
1659 nigel 75 subpattern number, or PCRE_ERROR_NOSUBSTRING (-7) if there is no subpattern of
1660     that name.
1661 nigel 63 </P>
1662     <P>
1663 nigel 75 Given the number, you can extract the substring directly, or use one of the
1664     functions described in the previous section. For convenience, there are also
1665     two functions that do the whole job.
1666 nigel 63 </P>
1667     <P>
1668 nigel 91 Most of the arguments of <b>pcre_copy_named_substring()</b> and
1669     <b>pcre_get_named_substring()</b> are the same as those for the similarly named
1670 nigel 75 functions that extract by number. As these are described in the previous
1671     section, they are not re-described here. There are just two differences:
1672 nigel 63 </P>
1673     <P>
1674     First, instead of a substring number, a substring name is given. Second, there
1675     is an extra argument, given at the start, which is a pointer to the compiled
1676     pattern. This is needed in order to gain access to the name-to-number
1677     translation table.
1678     </P>
1679     <P>
1680     These functions call <b>pcre_get_stringnumber()</b>, and if it succeeds, they
1681 ph10 128 then call <b>pcre_copy_substring()</b> or <b>pcre_get_substring()</b>, as
1682     appropriate. <b>NOTE:</b> If PCRE_DUPNAMES is set and there are duplicate names,
1683     the behaviour may not be what you want (see the next section).
1684 nigel 63 </P>
1685 nigel 91 <br><a name="SEC17" href="#TOC1">DUPLICATE SUBPATTERN NAMES</a><br>
1686 nigel 63 <P>
1687 nigel 91 <b>int pcre_get_stringtable_entries(const pcre *<i>code</i>,</b>
1688     <b>const char *<i>name</i>, char **<i>first</i>, char **<i>last</i>);</b>
1689     </P>
1690     <P>
1691     When a pattern is compiled with the PCRE_DUPNAMES option, names for subpatterns
1692     are not required to be unique. Normally, patterns with duplicate names are such
1693     that in any one match, only one of the named subpatterns participates. An
1694     example is shown in the
1695     <a href="pcrepattern.html"><b>pcrepattern</b></a>
1696 ph10 208 documentation.
1697     </P>
1698     <P>
1699     When duplicates are present, <b>pcre_copy_named_substring()</b> and
1700     <b>pcre_get_named_substring()</b> return the first substring corresponding to
1701     the given name that is set. If none are set, PCRE_ERROR_NOSUBSTRING (-7) is
1702     returned; no data is returned. The <b>pcre_get_stringnumber()</b> function
1703     returns one of the numbers that are associated with the name, but it is not
1704     defined which it is.
1705     </P>
1706     <P>
1707 nigel 91 If you want to get full details of all captured substrings for a given name,
1708     you must use the <b>pcre_get_stringtable_entries()</b> function. The first
1709     argument is the compiled pattern, and the second is the name. The third and
1710     fourth are pointers to variables which are updated by the function. After it
1711     has run, they point to the first and last entries in the name-to-number table
1712     for the given name. The function itself returns the length of each entry, or
1713 nigel 93 PCRE_ERROR_NOSUBSTRING (-7) if there are none. The format of the table is
1714     described above in the section entitled <i>Information about a pattern</i>.
1715     Given all the relevant entries for the name, you can extract each of their
1716     numbers, and hence the captured data, if any.
1717 nigel 91 </P>
1718     <br><a name="SEC18" href="#TOC1">FINDING ALL POSSIBLE MATCHES</a><br>
1719     <P>
1720 nigel 77 The traditional matching function uses a similar algorithm to Perl, which stops
1721     when it finds the first match, starting at a given point in the subject. If you
1722     want to find all possible matches, or the longest possible match, consider
1723     using the alternative matching function (see below) instead. If you cannot use
1724     the alternative function, but still need to find all possible matches, you
1725     can kludge it up by making use of the callout facility, which is described in
1726     the
1727     <a href="pcrecallout.html"><b>pcrecallout</b></a>
1728     documentation.
1729     </P>
1730     <P>
1731     What you have to do is to insert a callout right at the end of the pattern.
1732     When your callout function is called, extract and save the current matched
1733     substring. Then return 1, which forces <b>pcre_exec()</b> to backtrack and try
1734     other alternatives. Ultimately, when it runs out of matches, <b>pcre_exec()</b>
1735     will yield PCRE_ERROR_NOMATCH.
1736     <a name="dfamatch"></a></P>
1737 nigel 91 <br><a name="SEC19" href="#TOC1">MATCHING A PATTERN: THE ALTERNATIVE FUNCTION</a><br>
1738 nigel 77 <P>
1739     <b>int pcre_dfa_exec(const pcre *<i>code</i>, const pcre_extra *<i>extra</i>,</b>
1740     <b>const char *<i>subject</i>, int <i>length</i>, int <i>startoffset</i>,</b>
1741     <b>int <i>options</i>, int *<i>ovector</i>, int <i>ovecsize</i>,</b>
1742     <b>int *<i>workspace</i>, int <i>wscount</i>);</b>
1743     </P>
1744     <P>
1745     The function <b>pcre_dfa_exec()</b> is called to match a subject string against
1746 nigel 93 a compiled pattern, using a matching algorithm that scans the subject string
1747     just once, and does not backtrack. This has different characteristics to the
1748     normal algorithm, and is not compatible with Perl. Some of the features of PCRE
1749     patterns are not supported. Nevertheless, there are times when this kind of
1750     matching can be useful. For a discussion of the two matching algorithms, see
1751     the
1752 nigel 77 <a href="pcrematching.html"><b>pcrematching</b></a>
1753     documentation.
1754     </P>
1755     <P>
1756     The arguments for the <b>pcre_dfa_exec()</b> function are the same as for
1757     <b>pcre_exec()</b>, plus two extras. The <i>ovector</i> argument is used in a
1758     different way, and this is described below. The other common arguments are used
1759     in the same way as for <b>pcre_exec()</b>, so their description is not repeated
1760     here.
1761     </P>
1762     <P>
1763     The two additional arguments provide workspace for the function. The workspace
1764     vector should contain at least 20 elements. It is used for keeping track of
1765     multiple paths through the pattern tree. More workspace will be needed for
1766 nigel 91 patterns and subjects where there are a lot of potential matches.
1767 nigel 77 </P>
1768     <P>
1769 nigel 87 Here is an example of a simple call to <b>pcre_dfa_exec()</b>:
1770 nigel 77 <pre>
1771     int rc;
1772     int ovector[10];
1773     int wspace[20];
1774 nigel 87 rc = pcre_dfa_exec(
1775 nigel 77 re, /* result of pcre_compile() */
1776     NULL, /* we didn't study the pattern */
1777     "some string", /* the subject string */
1778     11, /* the length of the subject string */
1779     0, /* start at offset 0 in the subject */
1780     0, /* default options */
1781     ovector, /* vector of integers for substring information */
1782     10, /* number of elements (NOT size in bytes) */
1783     wspace, /* working space vector */
1784     20); /* number of elements (NOT size in bytes) */
1785     </PRE>
1786     </P>
1787     <br><b>
1788     Option bits for <b>pcre_dfa_exec()</b>
1789     </b><br>
1790     <P>
1791     The unused bits of the <i>options</i> argument for <b>pcre_dfa_exec()</b> must be
1792 nigel 91 zero. The only bits that may be set are PCRE_ANCHORED, PCRE_NEWLINE_<i>xxx</i>,
1793     PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY, PCRE_NO_UTF8_CHECK, PCRE_PARTIAL,
1794 nigel 77 PCRE_DFA_SHORTEST, and PCRE_DFA_RESTART. All but the last three of these are
1795     the same as for <b>pcre_exec()</b>, so their description is not repeated here.
1796     <pre>
1797     PCRE_PARTIAL
1798     </pre>
1799     This has the same general effect as it does for <b>pcre_exec()</b>, but the
1800     details are slightly different. When PCRE_PARTIAL is set for
1801     <b>pcre_dfa_exec()</b>, the return code PCRE_ERROR_NOMATCH is converted into
1802     PCRE_ERROR_PARTIAL if the end of the subject is reached, there have been no
1803     complete matches, but there is still at least one matching possibility. The
1804     portion of the string that provided the partial match is set as the first
1805     matching string.
1806     <pre>
1807     PCRE_DFA_SHORTEST
1808     </pre>
1809     Setting the PCRE_DFA_SHORTEST option causes the matching algorithm to stop as
1810 nigel 93 soon as it has found one match. Because of the way the alternative algorithm
1811     works, this is necessarily the shortest possible match at the first possible
1812     matching point in the subject string.
1813 nigel 77 <pre>
1814     PCRE_DFA_RESTART
1815     </pre>
1816     When <b>pcre_dfa_exec()</b> is called with the PCRE_PARTIAL option, and returns
1817     a partial match, it is possible to call it again, with additional subject
1818     characters, and have it continue with the same match. The PCRE_DFA_RESTART
1819     option requests this action; when it is set, the <i>workspace</i> and
1820     <i>wscount</i> options must reference the same vector as before because data
1821     about the match so far is left in them after a partial match. There is more
1822     discussion of this facility in the
1823     <a href="pcrepartial.html"><b>pcrepartial</b></a>
1824     documentation.
1825     </P>
1826     <br><b>
1827     Successful returns from <b>pcre_dfa_exec()</b>
1828     </b><br>
1829     <P>
1830     When <b>pcre_dfa_exec()</b> succeeds, it may have matched more than one
1831     substring in the subject. Note, however, that all the matches from one run of
1832     the function start at the same point in the subject. The shorter matches are
1833     all initial substrings of the longer matches. For example, if the pattern
1834     <pre>
1835     &#60;.*&#62;
1836     </pre>
1837     is matched against the string
1838     <pre>
1839     This is &#60;something&#62; &#60;something else&#62; &#60;something further&#62; no more
1840     </pre>
1841     the three matched strings are
1842     <pre>
1843     &#60;something&#62;
1844     &#60;something&#62; &#60;something else&#62;
1845     &#60;something&#62; &#60;something else&#62; &#60;something further&#62;
1846     </pre>
1847     On success, the yield of the function is a number greater than zero, which is
1848     the number of matched substrings. The substrings themselves are returned in
1849     <i>ovector</i>. Each string uses two elements; the first is the offset to the
1850 nigel 93 start, and the second is the offset to the end. In fact, all the strings have
1851     the same start offset. (Space could have been saved by giving this only once,
1852     but it was decided to retain some compatibility with the way <b>pcre_exec()</b>
1853     returns data, even though the meaning of the strings is different.)
1854 nigel 77 </P>
1855     <P>
1856     The strings are returned in reverse order of length; that is, the longest
1857     matching string is given first. If there were too many matches to fit into
1858     <i>ovector</i>, the yield of the function is zero, and the vector is filled with
1859     the longest matches.
1860     </P>
1861     <br><b>
1862     Error returns from <b>pcre_dfa_exec()</b>
1863     </b><br>
1864     <P>
1865     The <b>pcre_dfa_exec()</b> function returns a negative number when it fails.
1866     Many of the errors are the same as for <b>pcre_exec()</b>, and these are
1867     described
1868     <a href="#errorlist">above.</a>
1869     There are in addition the following errors that are specific to
1870     <b>pcre_dfa_exec()</b>:
1871     <pre>
1872     PCRE_ERROR_DFA_UITEM (-16)
1873     </pre>
1874     This return is given if <b>pcre_dfa_exec()</b> encounters an item in the pattern
1875     that it does not support, for instance, the use of \C or a back reference.
1876     <pre>
1877     PCRE_ERROR_DFA_UCOND (-17)
1878     </pre>
1879 nigel 93 This return is given if <b>pcre_dfa_exec()</b> encounters a condition item that
1880     uses a back reference for the condition, or a test for recursion in a specific
1881     group. These are not supported.
1882 nigel 77 <pre>
1883     PCRE_ERROR_DFA_UMLIMIT (-18)
1884     </pre>
1885     This return is given if <b>pcre_dfa_exec()</b> is called with an <i>extra</i>
1886     block that contains a setting of the <i>match_limit</i> field. This is not
1887     supported (it is meaningless).
1888     <pre>
1889     PCRE_ERROR_DFA_WSSIZE (-19)
1890     </pre>
1891     This return is given if <b>pcre_dfa_exec()</b> runs out of space in the
1892     <i>workspace</i> vector.
1893     <pre>
1894     PCRE_ERROR_DFA_RECURSE (-20)
1895     </pre>
1896     When a recursive subpattern is processed, the matching function calls itself
1897     recursively, using private vectors for <i>ovector</i> and <i>workspace</i>. This
1898     error is given if the output vector is not large enough. This should be
1899     extremely rare, as a vector of size 1000 is used.
1900     </P>
1901 nigel 93 <br><a name="SEC20" href="#TOC1">SEE ALSO</a><br>
1902 nigel 77 <P>
1903 nigel 93 <b>pcrebuild</b>(3), <b>pcrecallout</b>(3), <b>pcrecpp(3)</b>(3),
1904     <b>pcrematching</b>(3), <b>pcrepartial</b>(3), <b>pcreposix</b>(3),
1905     <b>pcreprecompile</b>(3), <b>pcresample</b>(3), <b>pcrestack</b>(3).
1906     </P>
1907 ph10 99 <br><a name="SEC21" href="#TOC1">AUTHOR</a><br>
1908 nigel 93 <P>
1909 ph10 99 Philip Hazel
1910 nigel 63 <br>
1911 ph10 99 University Computing Service
1912     <br>
1913     Cambridge CB2 3QH, England.
1914     <br>
1915     </P>
1916     <br><a name="SEC22" href="#TOC1">REVISION</a><br>
1917     <P>
1918 ph10 227 Last updated: 21 August 2007
1919 ph10 99 <br>
1920     Copyright &copy; 1997-2007 University of Cambridge.
1921     <br>
1922 nigel 75 <p>
1923     Return to the <a href="index.html">PCRE index page</a>.
1924     </p>

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