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1  .TH PCRE 3  .TH PCREAPI 3 "07 September 2012" "PCRE 8.32"
2  .SH NAME  .SH NAME
3  PCRE - Perl-compatible regular expressions  PCRE - Perl-compatible regular expressions
 .SH SYNOPSIS OF PCRE API  
 .rs  
4  .sp  .sp
5  .B #include <pcre.h>  .B #include <pcre.h>
6  .PP  .
7    .
8    .SH "PCRE NATIVE API BASIC FUNCTIONS"
9    .rs
10    .sp
11  .SM  .SM
12  .br  .B pcre *pcre_compile(const char *\fIpattern\fP, int \fIoptions\fP,
13  .B pcre *pcre_compile(const char *\fIpattern\fR, int \fIoptions\fR,  .ti +5n
14    .B const char **\fIerrptr\fP, int *\fIerroffset\fP,
15    .ti +5n
16    .B const unsigned char *\fItableptr\fP);
17    .PP
18    .B pcre *pcre_compile2(const char *\fIpattern\fP, int \fIoptions\fP,
19    .ti +5n
20    .B int *\fIerrorcodeptr\fP,
21  .ti +5n  .ti +5n
22  .B const char **\fIerrptr\fR, int *\fIerroffset\fR,  .B const char **\fIerrptr\fP, int *\fIerroffset\fP,
23  .ti +5n  .ti +5n
24  .B const unsigned char *\fItableptr\fR);  .B const unsigned char *\fItableptr\fP);
25  .PP  .PP
26  .br  .B pcre_extra *pcre_study(const pcre *\fIcode\fP, int \fIoptions\fP,
 .B pcre_extra *pcre_study(const pcre *\fIcode\fR, int \fIoptions\fR,  
27  .ti +5n  .ti +5n
28  .B const char **\fIerrptr\fR);  .B const char **\fIerrptr\fP);
29  .PP  .PP
30  .br  .B void pcre_free_study(pcre_extra *\fIextra\fP);
31  .B int pcre_exec(const pcre *\fIcode\fR, "const pcre_extra *\fIextra\fR,"  .PP
32    .B int pcre_exec(const pcre *\fIcode\fP, "const pcre_extra *\fIextra\fP,"
33  .ti +5n  .ti +5n
34  .B "const char *\fIsubject\fR," int \fIlength\fR, int \fIstartoffset\fR,  .B "const char *\fIsubject\fP," int \fIlength\fP, int \fIstartoffset\fP,
35  .ti +5n  .ti +5n
36  .B int \fIoptions\fR, int *\fIovector\fR, int \fIovecsize\fR);  .B int \fIoptions\fP, int *\fIovector\fP, int \fIovecsize\fP);
37  .PP  .PP
38  .br  .B int pcre_dfa_exec(const pcre *\fIcode\fP, "const pcre_extra *\fIextra\fP,"
39  .B int pcre_copy_named_substring(const pcre *\fIcode\fR,  .ti +5n
40    .B "const char *\fIsubject\fP," int \fIlength\fP, int \fIstartoffset\fP,
41    .ti +5n
42    .B int \fIoptions\fP, int *\fIovector\fP, int \fIovecsize\fP,
43    .ti +5n
44    .B int *\fIworkspace\fP, int \fIwscount\fP);
45    .
46    .
47    .SH "PCRE NATIVE API STRING EXTRACTION FUNCTIONS"
48    .rs
49    .sp
50    .B int pcre_copy_named_substring(const pcre *\fIcode\fP,
51  .ti +5n  .ti +5n
52  .B const char *\fIsubject\fR, int *\fIovector\fR,  .B const char *\fIsubject\fP, int *\fIovector\fP,
53  .ti +5n  .ti +5n
54  .B int \fIstringcount\fR, const char *\fIstringname\fR,  .B int \fIstringcount\fP, const char *\fIstringname\fP,
55  .ti +5n  .ti +5n
56  .B char *\fIbuffer\fR, int \fIbuffersize\fR);  .B char *\fIbuffer\fP, int \fIbuffersize\fP);
57  .PP  .PP
58  .br  .B int pcre_copy_substring(const char *\fIsubject\fP, int *\fIovector\fP,
 .B int pcre_copy_substring(const char *\fIsubject\fR, int *\fIovector\fR,  
59  .ti +5n  .ti +5n
60  .B int \fIstringcount\fR, int \fIstringnumber\fR, char *\fIbuffer\fR,  .B int \fIstringcount\fP, int \fIstringnumber\fP, char *\fIbuffer\fP,
61  .ti +5n  .ti +5n
62  .B int \fIbuffersize\fR);  .B int \fIbuffersize\fP);
63  .PP  .PP
64  .br  .B int pcre_get_named_substring(const pcre *\fIcode\fP,
 .B int pcre_get_named_substring(const pcre *\fIcode\fR,  
65  .ti +5n  .ti +5n
66  .B const char *\fIsubject\fR, int *\fIovector\fR,  .B const char *\fIsubject\fP, int *\fIovector\fP,
67  .ti +5n  .ti +5n
68  .B int \fIstringcount\fR, const char *\fIstringname\fR,  .B int \fIstringcount\fP, const char *\fIstringname\fP,
69    .ti +5n
70    .B const char **\fIstringptr\fP);
71    .PP
72    .B int pcre_get_stringnumber(const pcre *\fIcode\fP,
73  .ti +5n  .ti +5n
74  .B const char **\fIstringptr\fR);  .B const char *\fIname\fP);
75  .PP  .PP
76  .br  .B int pcre_get_stringtable_entries(const pcre *\fIcode\fP,
 .B int pcre_get_stringnumber(const pcre *\fIcode\fR,  
77  .ti +5n  .ti +5n
78  .B const char *\fIname\fR);  .B const char *\fIname\fP, char **\fIfirst\fP, char **\fIlast\fP);
79  .PP  .PP
80  .br  .B int pcre_get_substring(const char *\fIsubject\fP, int *\fIovector\fP,
 .B int pcre_get_substring(const char *\fIsubject\fR, int *\fIovector\fR,  
81  .ti +5n  .ti +5n
82  .B int \fIstringcount\fR, int \fIstringnumber\fR,  .B int \fIstringcount\fP, int \fIstringnumber\fP,
83  .ti +5n  .ti +5n
84  .B const char **\fIstringptr\fR);  .B const char **\fIstringptr\fP);
85  .PP  .PP
86  .br  .B int pcre_get_substring_list(const char *\fIsubject\fP,
 .B int pcre_get_substring_list(const char *\fIsubject\fR,  
87  .ti +5n  .ti +5n
88  .B int *\fIovector\fR, int \fIstringcount\fR, "const char ***\fIlistptr\fR);"  .B int *\fIovector\fP, int \fIstringcount\fP, "const char ***\fIlistptr\fP);"
89  .PP  .PP
90  .br  .B void pcre_free_substring(const char *\fIstringptr\fP);
 .B void pcre_free_substring(const char *\fIstringptr\fR);  
91  .PP  .PP
92  .br  .B void pcre_free_substring_list(const char **\fIstringptr\fP);
93  .B void pcre_free_substring_list(const char **\fIstringptr\fR);  .
94    .
95    .SH "PCRE NATIVE API AUXILIARY FUNCTIONS"
96    .rs
97    .sp
98    .B pcre_jit_stack *pcre_jit_stack_alloc(int \fIstartsize\fP, int \fImaxsize\fP);
99    .PP
100    .B void pcre_jit_stack_free(pcre_jit_stack *\fIstack\fP);
101    .PP
102    .B void pcre_assign_jit_stack(pcre_extra *\fIextra\fP,
103    .ti +5n
104    .B pcre_jit_callback \fIcallback\fP, void *\fIdata\fP);
105  .PP  .PP
 .br  
106  .B const unsigned char *pcre_maketables(void);  .B const unsigned char *pcre_maketables(void);
107  .PP  .PP
108  .br  .B int pcre_fullinfo(const pcre *\fIcode\fP, "const pcre_extra *\fIextra\fP,"
 .B int pcre_fullinfo(const pcre *\fIcode\fR, "const pcre_extra *\fIextra\fR,"  
109  .ti +5n  .ti +5n
110  .B int \fIwhat\fR, void *\fIwhere\fR);  .B int \fIwhat\fP, void *\fIwhere\fP);
111  .PP  .PP
112  .br  .B int pcre_refcount(pcre *\fIcode\fP, int \fIadjust\fP);
 .B int pcre_info(const pcre *\fIcode\fR, int *\fIoptptr\fR, int  
 .B *\fIfirstcharptr\fR);  
113  .PP  .PP
114  .br  .B int pcre_config(int \fIwhat\fP, void *\fIwhere\fP);
 .B int pcre_config(int \fIwhat\fR, void *\fIwhere\fR);  
115  .PP  .PP
116  .br  .B const char *pcre_version(void);
 .B char *pcre_version(void);  
117  .PP  .PP
118  .br  .B int pcre_pattern_to_host_byte_order(pcre *\fIcode\fP,
119    .ti +5n
120    .B pcre_extra *\fIextra\fP, const unsigned char *\fItables\fP);
121    .
122    .
123    .SH "PCRE NATIVE API INDIRECTED FUNCTIONS"
124    .rs
125    .sp
126  .B void *(*pcre_malloc)(size_t);  .B void *(*pcre_malloc)(size_t);
127  .PP  .PP
 .br  
128  .B void (*pcre_free)(void *);  .B void (*pcre_free)(void *);
129  .PP  .PP
130  .br  .B void *(*pcre_stack_malloc)(size_t);
131    .PP
132    .B void (*pcre_stack_free)(void *);
133    .PP
134  .B int (*pcre_callout)(pcre_callout_block *);  .B int (*pcre_callout)(pcre_callout_block *);
135    .
136  .SH PCRE API  .
137    .SH "PCRE 8-BIT, 16-BIT AND 32-BIT LIBRARIES"
138    .rs
139    .sp
140    From release 8.30, PCRE can be compiled as a library for handling 16-bit
141    character strings as well as, or instead of, the original library that handles
142    8-bit character strings. From release 8.32, PCRE can also be compiled as a
143    library for handling 32-bit character strings. To avoid too much complication,
144    this document describes the 8-bit versions of the functions, with only
145    occasional references to the 16-bit and 32-bit libraries.
146    .P
147    The 16-bit functions operate in the same way as their 8-bit counterparts; they
148    just use different data types for their arguments and results, and their names
149    start with \fBpcre16_\fP instead of \fBpcre_\fP. For every option that has UTF8
150    in its name (for example, PCRE_UTF8), there is a corresponding 16-bit name with
151    UTF8 replaced by UTF16. This facility is in fact just cosmetic; the 16-bit
152    option names define the same bit values.
153    .P
154    The 32-bit functions operate in the same way as their 8-bit counterparts; they
155    just use different data types for their arguments and results, and their names
156    start with \fBpcre32_\fP instead of \fBpcre_\fP. For every option that has UTF8
157    in its name (for example, PCRE_UTF8), there is a corresponding 32-bit name with
158    UTF8 replaced by UTF32. This facility is in fact just cosmetic; the 32-bit
159    option names define the same bit values.
160    .P
161    References to bytes and UTF-8 in this document should be read as references to
162    16-bit data quantities and UTF-16 when using the 16-bit library, unless
163    specified otherwise. More details of the specific differences for the 16-bit
164    library are given in the
165    .\" HREF
166    \fBpcre16\fP
167    .\"
168    page.
169    .
170    .P
171    References to bytes and UTF-8 in this document should be read as references to
172    32-bit data quantities and UTF-32 when using the 32-bit library, unless
173    specified otherwise. More details of the specific differences for the 32-bit
174    library are given in the
175    .\" HREF
176    \fBpcre32\fP
177    .\"
178    page.
179    .
180    .
181    .SH "PCRE API OVERVIEW"
182  .rs  .rs
183  .sp  .sp
184  PCRE has its own native API, which is described in this document. There is also  PCRE has its own native API, which is described in this document. There are
185  a set of wrapper functions that correspond to the POSIX regular expression API.  also some wrapper functions (for the 8-bit library only) that correspond to the
186  These are described in the \fBpcreposix\fR documentation.  POSIX regular expression API, but they do not give access to all the
187    functionality. They are described in the
188  The native API function prototypes are defined in the header file \fBpcre.h\fR,  .\" HREF
189  and on Unix systems the library itself is called \fBlibpcre.a\fR, so can be  \fBpcreposix\fP
190  accessed by adding \fB-lpcre\fR to the command for linking an application which  .\"
191  calls it. The header file defines the macros PCRE_MAJOR and PCRE_MINOR to  documentation. Both of these APIs define a set of C function calls. A C++
192  contain the major and minor release numbers for the library. Applications can  wrapper (again for the 8-bit library only) is also distributed with PCRE. It is
193  use these to include support for different releases.  documented in the
194    .\" HREF
195  The functions \fBpcre_compile()\fR, \fBpcre_study()\fR, and \fBpcre_exec()\fR  \fBpcrecpp\fP
196  are used for compiling and matching regular expressions. A sample program that  .\"
197  demonstrates the simplest way of using them is given in the file  page.
198  \fIpcredemo.c\fR. The \fBpcresample\fR documentation describes how to run it.  .P
199    The native API C function prototypes are defined in the header file
200  There are convenience functions for extracting captured substrings from a  \fBpcre.h\fP, and on Unix-like systems the (8-bit) library itself is called
201  matched subject string. They are:  \fBlibpcre\fP. It can normally be accessed by adding \fB-lpcre\fP to the
202    command for linking an application that uses PCRE. The header file defines the
203    \fBpcre_copy_substring()\fR  macros PCRE_MAJOR and PCRE_MINOR to contain the major and minor release numbers
204    \fBpcre_copy_named_substring()\fR  for the library. Applications can use these to include support for different
205    \fBpcre_get_substring()\fR  releases of PCRE.
206    \fBpcre_get_named_substring()\fR  .P
207    \fBpcre_get_substring_list()\fR  In a Windows environment, if you want to statically link an application program
208    against a non-dll \fBpcre.a\fP file, you must define PCRE_STATIC before
209  \fBpcre_free_substring()\fR and \fBpcre_free_substring_list()\fR are also  including \fBpcre.h\fP or \fBpcrecpp.h\fP, because otherwise the
210    \fBpcre_malloc()\fP and \fBpcre_free()\fP exported functions will be declared
211    \fB__declspec(dllimport)\fP, with unwanted results.
212    .P
213    The functions \fBpcre_compile()\fP, \fBpcre_compile2()\fP, \fBpcre_study()\fP,
214    and \fBpcre_exec()\fP are used for compiling and matching regular expressions
215    in a Perl-compatible manner. A sample program that demonstrates the simplest
216    way of using them is provided in the file called \fIpcredemo.c\fP in the PCRE
217    source distribution. A listing of this program is given in the
218    .\" HREF
219    \fBpcredemo\fP
220    .\"
221    documentation, and the
222    .\" HREF
223    \fBpcresample\fP
224    .\"
225    documentation describes how to compile and run it.
226    .P
227    Just-in-time compiler support is an optional feature of PCRE that can be built
228    in appropriate hardware environments. It greatly speeds up the matching
229    performance of many patterns. Simple programs can easily request that it be
230    used if available, by setting an option that is ignored when it is not
231    relevant. More complicated programs might need to make use of the functions
232    \fBpcre_jit_stack_alloc()\fP, \fBpcre_jit_stack_free()\fP, and
233    \fBpcre_assign_jit_stack()\fP in order to control the JIT code's memory usage.
234    These functions are discussed in the
235    .\" HREF
236    \fBpcrejit\fP
237    .\"
238    documentation.
239    .P
240    A second matching function, \fBpcre_dfa_exec()\fP, which is not
241    Perl-compatible, is also provided. This uses a different algorithm for the
242    matching. The alternative algorithm finds all possible matches (at a given
243    point in the subject), and scans the subject just once (unless there are
244    lookbehind assertions). However, this algorithm does not return captured
245    substrings. A description of the two matching algorithms and their advantages
246    and disadvantages is given in the
247    .\" HREF
248    \fBpcrematching\fP
249    .\"
250    documentation.
251    .P
252    In addition to the main compiling and matching functions, there are convenience
253    functions for extracting captured substrings from a subject string that is
254    matched by \fBpcre_exec()\fP. They are:
255    .sp
256      \fBpcre_copy_substring()\fP
257      \fBpcre_copy_named_substring()\fP
258      \fBpcre_get_substring()\fP
259      \fBpcre_get_named_substring()\fP
260      \fBpcre_get_substring_list()\fP
261      \fBpcre_get_stringnumber()\fP
262      \fBpcre_get_stringtable_entries()\fP
263    .sp
264    \fBpcre_free_substring()\fP and \fBpcre_free_substring_list()\fP are also
265  provided, to free the memory used for extracted strings.  provided, to free the memory used for extracted strings.
266    .P
267  The function \fBpcre_maketables()\fR is used (optionally) to build a set of  The function \fBpcre_maketables()\fP is used to build a set of character tables
268  character tables in the current locale for passing to \fBpcre_compile()\fR.  in the current locale for passing to \fBpcre_compile()\fP, \fBpcre_exec()\fP,
269    or \fBpcre_dfa_exec()\fP. This is an optional facility that is provided for
270  The function \fBpcre_fullinfo()\fR is used to find out information about a  specialist use. Most commonly, no special tables are passed, in which case
271  compiled pattern; \fBpcre_info()\fR is an obsolete version which returns only  internal tables that are generated when PCRE is built are used.
272  some of the available information, but is retained for backwards compatibility.  .P
273  The function \fBpcre_version()\fR returns a pointer to a string containing the  The function \fBpcre_fullinfo()\fP is used to find out information about a
274  version of PCRE and its date of release.  compiled pattern. The function \fBpcre_version()\fP returns a pointer to a
275    string containing the version of PCRE and its date of release.
276  The global variables \fBpcre_malloc\fR and \fBpcre_free\fR initially contain  .P
277  the entry points of the standard \fBmalloc()\fR and \fBfree()\fR functions  The function \fBpcre_refcount()\fP maintains a reference count in a data block
278    containing a compiled pattern. This is provided for the benefit of
279    object-oriented applications.
280    .P
281    The global variables \fBpcre_malloc\fP and \fBpcre_free\fP initially contain
282    the entry points of the standard \fBmalloc()\fP and \fBfree()\fP functions,
283  respectively. PCRE calls the memory management functions via these variables,  respectively. PCRE calls the memory management functions via these variables,
284  so a calling program can replace them if it wishes to intercept the calls. This  so a calling program can replace them if it wishes to intercept the calls. This
285  should be done before calling any PCRE functions.  should be done before calling any PCRE functions.
286    .P
287  The global variable \fBpcre_callout\fR initially contains NULL. It can be set  The global variables \fBpcre_stack_malloc\fP and \fBpcre_stack_free\fP are also
288    indirections to memory management functions. These special functions are used
289    only when PCRE is compiled to use the heap for remembering data, instead of
290    recursive function calls, when running the \fBpcre_exec()\fP function. See the
291    .\" HREF
292    \fBpcrebuild\fP
293    .\"
294    documentation for details of how to do this. It is a non-standard way of
295    building PCRE, for use in environments that have limited stacks. Because of the
296    greater use of memory management, it runs more slowly. Separate functions are
297    provided so that special-purpose external code can be used for this case. When
298    used, these functions are always called in a stack-like manner (last obtained,
299    first freed), and always for memory blocks of the same size. There is a
300    discussion about PCRE's stack usage in the
301    .\" HREF
302    \fBpcrestack\fP
303    .\"
304    documentation.
305    .P
306    The global variable \fBpcre_callout\fP initially contains NULL. It can be set
307  by the caller to a "callout" function, which PCRE will then call at specified  by the caller to a "callout" function, which PCRE will then call at specified
308  points during a matching operation. Details are given in the \fBpcrecallout\fR  points during a matching operation. Details are given in the
309    .\" HREF
310    \fBpcrecallout\fP
311    .\"
312  documentation.  documentation.
313    .
314    .
315    .\" HTML <a name="newlines"></a>
316    .SH NEWLINES
317    .rs
318    .sp
319    PCRE supports five different conventions for indicating line breaks in
320    strings: a single CR (carriage return) character, a single LF (linefeed)
321    character, the two-character sequence CRLF, any of the three preceding, or any
322    Unicode newline sequence. The Unicode newline sequences are the three just
323    mentioned, plus the single characters VT (vertical tab, U+000B), FF (form feed,
324    U+000C), NEL (next line, U+0085), LS (line separator, U+2028), and PS
325    (paragraph separator, U+2029).
326    .P
327    Each of the first three conventions is used by at least one operating system as
328    its standard newline sequence. When PCRE is built, a default can be specified.
329    The default default is LF, which is the Unix standard. When PCRE is run, the
330    default can be overridden, either when a pattern is compiled, or when it is
331    matched.
332    .P
333    At compile time, the newline convention can be specified by the \fIoptions\fP
334    argument of \fBpcre_compile()\fP, or it can be specified by special text at the
335    start of the pattern itself; this overrides any other settings. See the
336    .\" HREF
337    \fBpcrepattern\fP
338    .\"
339    page for details of the special character sequences.
340    .P
341    In the PCRE documentation the word "newline" is used to mean "the character or
342    pair of characters that indicate a line break". The choice of newline
343    convention affects the handling of the dot, circumflex, and dollar
344    metacharacters, the handling of #-comments in /x mode, and, when CRLF is a
345    recognized line ending sequence, the match position advancement for a
346    non-anchored pattern. There is more detail about this in the
347    .\" HTML <a href="#execoptions">
348    .\" </a>
349    section on \fBpcre_exec()\fP options
350    .\"
351    below.
352    .P
353    The choice of newline convention does not affect the interpretation of
354    the \en or \er escape sequences, nor does it affect what \eR matches, which is
355    controlled in a similar way, but by separate options.
356    .
357    .
358  .SH MULTITHREADING  .SH MULTITHREADING
359  .rs  .rs
360  .sp  .sp
361  The PCRE functions can be used in multi-threading applications, with the  The PCRE functions can be used in multi-threading applications, with the
362  proviso that the memory management functions pointed to by \fBpcre_malloc\fR  proviso that the memory management functions pointed to by \fBpcre_malloc\fP,
363  and \fBpcre_free\fR, and the callout function pointed to by \fBpcre_callout\fR,  \fBpcre_free\fP, \fBpcre_stack_malloc\fP, and \fBpcre_stack_free\fP, and the
364  are shared by all threads.  callout function pointed to by \fBpcre_callout\fP, are shared by all threads.
365    .P
366  The compiled form of a regular expression is not altered during matching, so  The compiled form of a regular expression is not altered during matching, so
367  the same compiled pattern can safely be used by several threads at once.  the same compiled pattern can safely be used by several threads at once.
368    .P
369  .SH CHECKING BUILD-TIME OPTIONS  If the just-in-time optimization feature is being used, it needs separate
370    memory stack areas for each thread. See the
371    .\" HREF
372    \fBpcrejit\fP
373    .\"
374    documentation for more details.
375    .
376    .
377    .SH "SAVING PRECOMPILED PATTERNS FOR LATER USE"
378    .rs
379    .sp
380    The compiled form of a regular expression can be saved and re-used at a later
381    time, possibly by a different program, and even on a host other than the one on
382    which it was compiled. Details are given in the
383    .\" HREF
384    \fBpcreprecompile\fP
385    .\"
386    documentation, which includes a description of the
387    \fBpcre_pattern_to_host_byte_order()\fP function. However, compiling a regular
388    expression with one version of PCRE for use with a different version is not
389    guaranteed to work and may cause crashes.
390    .
391    .
392    .SH "CHECKING BUILD-TIME OPTIONS"
393  .rs  .rs
394  .sp  .sp
395  .B int pcre_config(int \fIwhat\fR, void *\fIwhere\fR);  .B int pcre_config(int \fIwhat\fP, void *\fIwhere\fP);
396  .PP  .PP
397  The function \fBpcre_config()\fR makes it possible for a PCRE client to  The function \fBpcre_config()\fP makes it possible for a PCRE client to
398  discover which optional features have been compiled into the PCRE library. The  discover which optional features have been compiled into the PCRE library. The
399  .\" HREF  .\" HREF
400  \fBpcrebuild\fR  \fBpcrebuild\fP
401  .\"  .\"
402  documentation has more details about these optional features.  documentation has more details about these optional features.
403    .P
404  The first argument for \fBpcre_config()\fR is an integer, specifying which  The first argument for \fBpcre_config()\fP is an integer, specifying which
405  information is required; the second argument is a pointer to a variable into  information is required; the second argument is a pointer to a variable into
406  which the information is placed. The following information is available:  which the information is placed. The returned value is zero on success, or the
407    negative error code PCRE_ERROR_BADOPTION if the value in the first argument is
408    not recognized. The following information is available:
409    .sp
410    PCRE_CONFIG_UTF8    PCRE_CONFIG_UTF8
411    .sp
412  The output is an integer that is set to one if UTF-8 support is available;  The output is an integer that is set to one if UTF-8 support is available;
413  otherwise it is set to zero.  otherwise it is set to zero. This value should normally be given to the 8-bit
414    version of this function, \fBpcre_config()\fP. If it is given to the 16-bit
415    or 32-bit version of this function, the result is PCRE_ERROR_BADOPTION.
416    .sp
417      PCRE_CONFIG_UTF16
418    .sp
419    The output is an integer that is set to one if UTF-16 support is available;
420    otherwise it is set to zero. This value should normally be given to the 16-bit
421    version of this function, \fBpcre16_config()\fP. If it is given to the 8-bit
422    or 32-bit version of this function, the result is PCRE_ERROR_BADOPTION.
423    .sp
424      PCRE_CONFIG_UTF32
425    .sp
426    The output is an integer that is set to one if UTF-32 support is available;
427    otherwise it is set to zero. This value should normally be given to the 32-bit
428    version of this function, \fBpcre32_config()\fP. If it is given to the 8-bit
429    or 16-bit version of this function, the result is PCRE_ERROR_BADOPTION.
430    .sp
431      PCRE_CONFIG_UNICODE_PROPERTIES
432    .sp
433    The output is an integer that is set to one if support for Unicode character
434    properties is available; otherwise it is set to zero.
435    .sp
436      PCRE_CONFIG_JIT
437    .sp
438    The output is an integer that is set to one if support for just-in-time
439    compiling is available; otherwise it is set to zero.
440    .sp
441      PCRE_CONFIG_JITTARGET
442    .sp
443    The output is a pointer to a zero-terminated "const char *" string. If JIT
444    support is available, the string contains the name of the architecture for
445    which the JIT compiler is configured, for example "x86 32bit (little endian +
446    unaligned)". If JIT support is not available, the result is NULL.
447    .sp
448    PCRE_CONFIG_NEWLINE    PCRE_CONFIG_NEWLINE
449    .sp
450  The output is an integer that is set to the value of the code that is used for  The output is an integer whose value specifies the default character sequence
451  the newline character. It is either linefeed (10) or carriage return (13), and  that is recognized as meaning "newline". The values that are supported in
452  should normally be the standard character for your operating system.  ASCII/Unicode environments are: 10 for LF, 13 for CR, 3338 for CRLF, -2 for
453    ANYCRLF, and -1 for ANY. In EBCDIC environments, CR, ANYCRLF, and ANY yield the
454    same values. However, the value for LF is normally 21, though some EBCDIC
455    environments use 37. The corresponding values for CRLF are 3349 and 3365. The
456    default should normally correspond to the standard sequence for your operating
457    system.
458    .sp
459      PCRE_CONFIG_BSR
460    .sp
461    The output is an integer whose value indicates what character sequences the \eR
462    escape sequence matches by default. A value of 0 means that \eR matches any
463    Unicode line ending sequence; a value of 1 means that \eR matches only CR, LF,
464    or CRLF. The default can be overridden when a pattern is compiled or matched.
465    .sp
466    PCRE_CONFIG_LINK_SIZE    PCRE_CONFIG_LINK_SIZE
467    .sp
468  The output is an integer that contains the number of bytes used for internal  The output is an integer that contains the number of bytes used for internal
469  linkage in compiled regular expressions. The value is 2, 3, or 4. Larger values  linkage in compiled regular expressions. For the 8-bit library, the value can
470  allow larger regular expressions to be compiled, at the expense of slower  be 2, 3, or 4. For the 16-bit library, the value is either 2 or 4 and is still
471  matching. The default value of 2 is sufficient for all but the most massive  a number of bytes. For the 32-bit library, the value is either 2 or 4 and is
472  patterns, since it allows the compiled pattern to be up to 64K in size.  still a number of bytes. The default value of 2 is sufficient for all but the
473    most massive patterns, since it allows the compiled pattern to be up to 64K in
474    size. Larger values allow larger regular expressions to be compiled, at the
475    expense of slower matching.
476    .sp
477    PCRE_CONFIG_POSIX_MALLOC_THRESHOLD    PCRE_CONFIG_POSIX_MALLOC_THRESHOLD
478    .sp
479  The output is an integer that contains the threshold above which the POSIX  The output is an integer that contains the threshold above which the POSIX
480  interface uses \fBmalloc()\fR for output vectors. Further details are given in  interface uses \fBmalloc()\fP for output vectors. Further details are given in
481  the \fBpcreposix\fR documentation.  the
482    .\" HREF
483    \fBpcreposix\fP
484    .\"
485    documentation.
486    .sp
487    PCRE_CONFIG_MATCH_LIMIT    PCRE_CONFIG_MATCH_LIMIT
488    .sp
489  The output is an integer that gives the default limit for the number of  The output is a long integer that gives the default limit for the number of
490  internal matching function calls in a \fBpcre_exec()\fR execution. Further  internal matching function calls in a \fBpcre_exec()\fP execution. Further
491  details are given with \fBpcre_exec()\fR below.  details are given with \fBpcre_exec()\fP below.
492    .sp
493  .SH COMPILING A PATTERN    PCRE_CONFIG_MATCH_LIMIT_RECURSION
494  .rs  .sp
495  .sp  The output is a long integer that gives the default limit for the depth of
496  .B pcre *pcre_compile(const char *\fIpattern\fR, int \fIoptions\fR,  recursion when calling the internal matching function in a \fBpcre_exec()\fP
497  .ti +5n  execution. Further details are given with \fBpcre_exec()\fP below.
498  .B const char **\fIerrptr\fR, int *\fIerroffset\fR,  .sp
499  .ti +5n    PCRE_CONFIG_STACKRECURSE
500  .B const unsigned char *\fItableptr\fR);  .sp
501  .PP  The output is an integer that is set to one if internal recursion when running
502    \fBpcre_exec()\fP is implemented by recursive function calls that use the stack
503  The function \fBpcre_compile()\fR is called to compile a pattern into an  to remember their state. This is the usual way that PCRE is compiled. The
504  internal form. The pattern is a C string terminated by a binary zero, and  output is zero if PCRE was compiled to use blocks of data on the heap instead
505  is passed in the argument \fIpattern\fR. A pointer to a single block of memory  of recursive function calls. In this case, \fBpcre_stack_malloc\fP and
506  that is obtained via \fBpcre_malloc\fR is returned. This contains the compiled  \fBpcre_stack_free\fP are called to manage memory blocks on the heap, thus
507  code and related data. The \fBpcre\fR type is defined for the returned block;  avoiding the use of the stack.
508  this is a typedef for a structure whose contents are not externally defined. It  .
509  is up to the caller to free the memory when it is no longer required.  .
510    .SH "COMPILING A PATTERN"
511    .rs
512    .sp
513    .B pcre *pcre_compile(const char *\fIpattern\fP, int \fIoptions\fP,
514    .ti +5n
515    .B const char **\fIerrptr\fP, int *\fIerroffset\fP,
516    .ti +5n
517    .B const unsigned char *\fItableptr\fP);
518    .sp
519    .B pcre *pcre_compile2(const char *\fIpattern\fP, int \fIoptions\fP,
520    .ti +5n
521    .B int *\fIerrorcodeptr\fP,
522    .ti +5n
523    .B const char **\fIerrptr\fP, int *\fIerroffset\fP,
524    .ti +5n
525    .B const unsigned char *\fItableptr\fP);
526    .P
527    Either of the functions \fBpcre_compile()\fP or \fBpcre_compile2()\fP can be
528    called to compile a pattern into an internal form. The only difference between
529    the two interfaces is that \fBpcre_compile2()\fP has an additional argument,
530    \fIerrorcodeptr\fP, via which a numerical error code can be returned. To avoid
531    too much repetition, we refer just to \fBpcre_compile()\fP below, but the
532    information applies equally to \fBpcre_compile2()\fP.
533    .P
534    The pattern is a C string terminated by a binary zero, and is passed in the
535    \fIpattern\fP argument. A pointer to a single block of memory that is obtained
536    via \fBpcre_malloc\fP is returned. This contains the compiled code and related
537    data. The \fBpcre\fP type is defined for the returned block; this is a typedef
538    for a structure whose contents are not externally defined. It is up to the
539    caller to free the memory (via \fBpcre_free\fP) when it is no longer required.
540    .P
541  Although the compiled code of a PCRE regex is relocatable, that is, it does not  Although the compiled code of a PCRE regex is relocatable, that is, it does not
542  depend on memory location, the complete \fBpcre\fR data block is not  depend on memory location, the complete \fBpcre\fP data block is not
543  fully relocatable, because it contains a copy of the \fItableptr\fR argument,  fully relocatable, because it may contain a copy of the \fItableptr\fP
544  which is an address (see below).  argument, which is an address (see below).
545    .P
546  The \fIoptions\fR argument contains independent bits that affect the  The \fIoptions\fP argument contains various bit settings that affect the
547  compilation. It should be zero if no options are required. Some of the options,  compilation. It should be zero if no options are required. The available
548  in particular, those that are compatible with Perl, can also be set and unset  options are described below. Some of them (in particular, those that are
549  from within the pattern (see the detailed description of regular expressions  compatible with Perl, but some others as well) can also be set and unset from
550  in the \fBpcrepattern\fR documentation). For these options, the contents of the  within the pattern (see the detailed description in the
551  \fIoptions\fR argument specifies their initial settings at the start of  .\" HREF
552  compilation and execution. The PCRE_ANCHORED option can be set at the time of  \fBpcrepattern\fP
553  matching as well as at compile time.  .\"
554    documentation). For those options that can be different in different parts of
555  If \fIerrptr\fR is NULL, \fBpcre_compile()\fR returns NULL immediately.  the pattern, the contents of the \fIoptions\fP argument specifies their
556  Otherwise, if compilation of a pattern fails, \fBpcre_compile()\fR returns  settings at the start of compilation and execution. The PCRE_ANCHORED,
557  NULL, and sets the variable pointed to by \fIerrptr\fR to point to a textual  PCRE_BSR_\fIxxx\fP, PCRE_NEWLINE_\fIxxx\fP, PCRE_NO_UTF8_CHECK, and
558  error message. The offset from the start of the pattern to the character where  PCRE_NO_START_OPTIMIZE options can be set at the time of matching as well as at
559  the error was discovered is placed in the variable pointed to by  compile time.
560  \fIerroffset\fR, which must not be NULL. If it is, an immediate error is given.  .P
561    If \fIerrptr\fP is NULL, \fBpcre_compile()\fP returns NULL immediately.
562  If the final argument, \fItableptr\fR, is NULL, PCRE uses a default set of  Otherwise, if compilation of a pattern fails, \fBpcre_compile()\fP returns
563  character tables which are built when it is compiled, using the default C  NULL, and sets the variable pointed to by \fIerrptr\fP to point to a textual
564  locale. Otherwise, \fItableptr\fR must be the result of a call to  error message. This is a static string that is part of the library. You must
565  \fBpcre_maketables()\fR. See the section on locale support below.  not try to free it. Normally, the offset from the start of the pattern to the
566    byte that was being processed when the error was discovered is placed in the
567  This code fragment shows a typical straightforward call to \fBpcre_compile()\fR:  variable pointed to by \fIerroffset\fP, which must not be NULL (if it is, an
568    immediate error is given). However, for an invalid UTF-8 string, the offset is
569    that of the first byte of the failing character.
570    .P
571    Some errors are not detected until the whole pattern has been scanned; in these
572    cases, the offset passed back is the length of the pattern. Note that the
573    offset is in bytes, not characters, even in UTF-8 mode. It may sometimes point
574    into the middle of a UTF-8 character.
575    .P
576    If \fBpcre_compile2()\fP is used instead of \fBpcre_compile()\fP, and the
577    \fIerrorcodeptr\fP argument is not NULL, a non-zero error code number is
578    returned via this argument in the event of an error. This is in addition to the
579    textual error message. Error codes and messages are listed below.
580    .P
581    If the final argument, \fItableptr\fP, is NULL, PCRE uses a default set of
582    character tables that are built when PCRE is compiled, using the default C
583    locale. Otherwise, \fItableptr\fP must be an address that is the result of a
584    call to \fBpcre_maketables()\fP. This value is stored with the compiled
585    pattern, and used again by \fBpcre_exec()\fP, unless another table pointer is
586    passed to it. For more discussion, see the section on locale support below.
587    .P
588    This code fragment shows a typical straightforward call to \fBpcre_compile()\fP:
589    .sp
590    pcre *re;    pcre *re;
591    const char *error;    const char *error;
592    int erroffset;    int erroffset;
# Line 265  This code fragment shows a typical strai Line 596  This code fragment shows a typical strai
596      &error,           /* for error message */      &error,           /* for error message */
597      &erroffset,       /* for error offset */      &erroffset,       /* for error offset */
598      NULL);            /* use default character tables */      NULL);            /* use default character tables */
599    .sp
600  The following option bits are defined:  The following names for option bits are defined in the \fBpcre.h\fP header
601    file:
602    .sp
603    PCRE_ANCHORED    PCRE_ANCHORED
604    .sp
605  If this bit is set, the pattern is forced to be "anchored", that is, it is  If this bit is set, the pattern is forced to be "anchored", that is, it is
606  constrained to match only at the first matching point in the string which is  constrained to match only at the first matching point in the string that is
607  being searched (the "subject string"). This effect can also be achieved by  being searched (the "subject string"). This effect can also be achieved by
608  appropriate constructs in the pattern itself, which is the only way to do it in  appropriate constructs in the pattern itself, which is the only way to do it in
609  Perl.  Perl.
610    .sp
611      PCRE_AUTO_CALLOUT
612    .sp
613    If this bit is set, \fBpcre_compile()\fP automatically inserts callout items,
614    all with number 255, before each pattern item. For discussion of the callout
615    facility, see the
616    .\" HREF
617    \fBpcrecallout\fP
618    .\"
619    documentation.
620    .sp
621      PCRE_BSR_ANYCRLF
622      PCRE_BSR_UNICODE
623    .sp
624    These options (which are mutually exclusive) control what the \eR escape
625    sequence matches. The choice is either to match only CR, LF, or CRLF, or to
626    match any Unicode newline sequence. The default is specified when PCRE is
627    built. It can be overridden from within the pattern, or by setting an option
628    when a compiled pattern is matched.
629    .sp
630    PCRE_CASELESS    PCRE_CASELESS
631    .sp
632  If this bit is set, letters in the pattern match both upper and lower case  If this bit is set, letters in the pattern match both upper and lower case
633  letters. It is equivalent to Perl's /i option, and it can be changed within a  letters. It is equivalent to Perl's /i option, and it can be changed within a
634  pattern by a (?i) option setting.  pattern by a (?i) option setting. In UTF-8 mode, PCRE always understands the
635    concept of case for characters whose values are less than 128, so caseless
636    matching is always possible. For characters with higher values, the concept of
637    case is supported if PCRE is compiled with Unicode property support, but not
638    otherwise. If you want to use caseless matching for characters 128 and above,
639    you must ensure that PCRE is compiled with Unicode property support as well as
640    with UTF-8 support.
641    .sp
642    PCRE_DOLLAR_ENDONLY    PCRE_DOLLAR_ENDONLY
643    .sp
644  If this bit is set, a dollar metacharacter in the pattern matches only at the  If this bit is set, a dollar metacharacter in the pattern matches only at the
645  end of the subject string. Without this option, a dollar also matches  end of the subject string. Without this option, a dollar also matches
646  immediately before the final character if it is a newline (but not before any  immediately before a newline at the end of the string (but not before any other
647  other newlines). The PCRE_DOLLAR_ENDONLY option is ignored if PCRE_MULTILINE is  newlines). The PCRE_DOLLAR_ENDONLY option is ignored if PCRE_MULTILINE is set.
648  set. There is no equivalent to this option in Perl, and no way to set it within  There is no equivalent to this option in Perl, and no way to set it within a
649  a pattern.  pattern.
650    .sp
651    PCRE_DOTALL    PCRE_DOTALL
652    .sp
653  If this bit is set, a dot metacharater in the pattern matches all characters,  If this bit is set, a dot metacharacter in the pattern matches a character of
654  including newlines. Without it, newlines are excluded. This option is  any value, including one that indicates a newline. However, it only ever
655    matches one character, even if newlines are coded as CRLF. Without this option,
656    a dot does not match when the current position is at a newline. This option is
657  equivalent to Perl's /s option, and it can be changed within a pattern by a  equivalent to Perl's /s option, and it can be changed within a pattern by a
658  (?s) option setting. A negative class such as [^a] always matches a newline  (?s) option setting. A negative class such as [^a] always matches newline
659  character, independent of the setting of this option.  characters, independent of the setting of this option.
660    .sp
661      PCRE_DUPNAMES
662    .sp
663    If this bit is set, names used to identify capturing subpatterns need not be
664    unique. This can be helpful for certain types of pattern when it is known that
665    only one instance of the named subpattern can ever be matched. There are more
666    details of named subpatterns below; see also the
667    .\" HREF
668    \fBpcrepattern\fP
669    .\"
670    documentation.
671    .sp
672    PCRE_EXTENDED    PCRE_EXTENDED
673    .sp
674  If this bit is set, whitespace data characters in the pattern are totally  If this bit is set, white space data characters in the pattern are totally
675  ignored except when escaped or inside a character class. Whitespace does not  ignored except when escaped or inside a character class. White space does not
676  include the VT character (code 11). In addition, characters between an  include the VT character (code 11). In addition, characters between an
677  unescaped # outside a character class and the next newline character,  unescaped # outside a character class and the next newline, inclusive, are also
678  inclusive, are also ignored. This is equivalent to Perl's /x option, and it can  ignored. This is equivalent to Perl's /x option, and it can be changed within a
679  be changed within a pattern by a (?x) option setting.  pattern by a (?x) option setting.
680    .P
681    Which characters are interpreted as newlines is controlled by the options
682    passed to \fBpcre_compile()\fP or by a special sequence at the start of the
683    pattern, as described in the section entitled
684    .\" HTML <a href="pcrepattern.html#newlines">
685    .\" </a>
686    "Newline conventions"
687    .\"
688    in the \fBpcrepattern\fP documentation. Note that the end of this type of
689    comment is a literal newline sequence in the pattern; escape sequences that
690    happen to represent a newline do not count.
691    .P
692  This option makes it possible to include comments inside complicated patterns.  This option makes it possible to include comments inside complicated patterns.
693  Note, however, that this applies only to data characters. Whitespace characters  Note, however, that this applies only to data characters. White space characters
694  may never appear within special character sequences in a pattern, for example  may never appear within special character sequences in a pattern, for example
695  within the sequence (?( which introduces a conditional subpattern.  within the sequence (?( that introduces a conditional subpattern.
696    .sp
697    PCRE_EXTRA    PCRE_EXTRA
698    .sp
699  This option was invented in order to turn on additional functionality of PCRE  This option was invented in order to turn on additional functionality of PCRE
700  that is incompatible with Perl, but it is currently of very little use. When  that is incompatible with Perl, but it is currently of very little use. When
701  set, any backslash in a pattern that is followed by a letter that has no  set, any backslash in a pattern that is followed by a letter that has no
702  special meaning causes an error, thus reserving these combinations for future  special meaning causes an error, thus reserving these combinations for future
703  expansion. By default, as in Perl, a backslash followed by a letter with no  expansion. By default, as in Perl, a backslash followed by a letter with no
704  special meaning is treated as a literal. There are at present no other features  special meaning is treated as a literal. (Perl can, however, be persuaded to
705  controlled by this option. It can also be set by a (?X) option setting within a  give an error for this, by running it with the -w option.) There are at present
706  pattern.  no other features controlled by this option. It can also be set by a (?X)
707    option setting within a pattern.
708    .sp
709      PCRE_FIRSTLINE
710    .sp
711    If this option is set, an unanchored pattern is required to match before or at
712    the first newline in the subject string, though the matched text may continue
713    over the newline.
714    .sp
715      PCRE_JAVASCRIPT_COMPAT
716    .sp
717    If this option is set, PCRE's behaviour is changed in some ways so that it is
718    compatible with JavaScript rather than Perl. The changes are as follows:
719    .P
720    (1) A lone closing square bracket in a pattern causes a compile-time error,
721    because this is illegal in JavaScript (by default it is treated as a data
722    character). Thus, the pattern AB]CD becomes illegal when this option is set.
723    .P
724    (2) At run time, a back reference to an unset subpattern group matches an empty
725    string (by default this causes the current matching alternative to fail). A
726    pattern such as (\e1)(a) succeeds when this option is set (assuming it can find
727    an "a" in the subject), whereas it fails by default, for Perl compatibility.
728    .P
729    (3) \eU matches an upper case "U" character; by default \eU causes a compile
730    time error (Perl uses \eU to upper case subsequent characters).
731    .P
732    (4) \eu matches a lower case "u" character unless it is followed by four
733    hexadecimal digits, in which case the hexadecimal number defines the code point
734    to match. By default, \eu causes a compile time error (Perl uses it to upper
735    case the following character).
736    .P
737    (5) \ex matches a lower case "x" character unless it is followed by two
738    hexadecimal digits, in which case the hexadecimal number defines the code point
739    to match. By default, as in Perl, a hexadecimal number is always expected after
740    \ex, but it may have zero, one, or two digits (so, for example, \exz matches a
741    binary zero character followed by z).
742    .sp
743    PCRE_MULTILINE    PCRE_MULTILINE
744    .sp
745  By default, PCRE treats the subject string as consisting of a single "line" of  By default, PCRE treats the subject string as consisting of a single line of
746  characters (even if it actually contains several newlines). The "start of line"  characters (even if it actually contains newlines). The "start of line"
747  metacharacter (^) matches only at the start of the string, while the "end of  metacharacter (^) matches only at the start of the string, while the "end of
748  line" metacharacter ($) matches only at the end of the string, or before a  line" metacharacter ($) matches only at the end of the string, or before a
749  terminating newline (unless PCRE_DOLLAR_ENDONLY is set). This is the same as  terminating newline (unless PCRE_DOLLAR_ENDONLY is set). This is the same as
750  Perl.  Perl.
751    .P
752  When PCRE_MULTILINE it is set, the "start of line" and "end of line" constructs  When PCRE_MULTILINE it is set, the "start of line" and "end of line" constructs
753  match immediately following or immediately before any newline in the subject  match immediately following or immediately before internal newlines in the
754  string, respectively, as well as at the very start and end. This is equivalent  subject string, respectively, as well as at the very start and end. This is
755  to Perl's /m option, and it can be changed within a pattern by a (?m) option  equivalent to Perl's /m option, and it can be changed within a pattern by a
756  setting. If there are no "\\n" characters in a subject string, or no  (?m) option setting. If there are no newlines in a subject string, or no
757  occurrences of ^ or $ in a pattern, setting PCRE_MULTILINE has no effect.  occurrences of ^ or $ in a pattern, setting PCRE_MULTILINE has no effect.
758    .sp
759      PCRE_NEWLINE_CR
760      PCRE_NEWLINE_LF
761      PCRE_NEWLINE_CRLF
762      PCRE_NEWLINE_ANYCRLF
763      PCRE_NEWLINE_ANY
764    .sp
765    These options override the default newline definition that was chosen when PCRE
766    was built. Setting the first or the second specifies that a newline is
767    indicated by a single character (CR or LF, respectively). Setting
768    PCRE_NEWLINE_CRLF specifies that a newline is indicated by the two-character
769    CRLF sequence. Setting PCRE_NEWLINE_ANYCRLF specifies that any of the three
770    preceding sequences should be recognized. Setting PCRE_NEWLINE_ANY specifies
771    that any Unicode newline sequence should be recognized.
772    .P
773    In an ASCII/Unicode environment, the Unicode newline sequences are the three
774    just mentioned, plus the single characters VT (vertical tab, U+000B), FF (form
775    feed, U+000C), NEL (next line, U+0085), LS (line separator, U+2028), and PS
776    (paragraph separator, U+2029). For the 8-bit library, the last two are
777    recognized only in UTF-8 mode.
778    .P
779    When PCRE is compiled to run in an EBCDIC (mainframe) environment, the code for
780    CR is 0x0d, the same as ASCII. However, the character code for LF is normally
781    0x15, though in some EBCDIC environments 0x25 is used. Whichever of these is
782    not LF is made to correspond to Unicode's NEL character. EBCDIC codes are all
783    less than 256. For more details, see the
784    .\" HREF
785    \fBpcrebuild\fP
786    .\"
787    documentation.
788    .P
789    The newline setting in the options word uses three bits that are treated
790    as a number, giving eight possibilities. Currently only six are used (default
791    plus the five values above). This means that if you set more than one newline
792    option, the combination may or may not be sensible. For example,
793    PCRE_NEWLINE_CR with PCRE_NEWLINE_LF is equivalent to PCRE_NEWLINE_CRLF, but
794    other combinations may yield unused numbers and cause an error.
795    .P
796    The only time that a line break in a pattern is specially recognized when
797    compiling is when PCRE_EXTENDED is set. CR and LF are white space characters,
798    and so are ignored in this mode. Also, an unescaped # outside a character class
799    indicates a comment that lasts until after the next line break sequence. In
800    other circumstances, line break sequences in patterns are treated as literal
801    data.
802    .P
803    The newline option that is set at compile time becomes the default that is used
804    for \fBpcre_exec()\fP and \fBpcre_dfa_exec()\fP, but it can be overridden.
805    .sp
806    PCRE_NO_AUTO_CAPTURE    PCRE_NO_AUTO_CAPTURE
807    .sp
808  If this option is set, it disables the use of numbered capturing parentheses in  If this option is set, it disables the use of numbered capturing parentheses in
809  the pattern. Any opening parenthesis that is not followed by ? behaves as if it  the pattern. Any opening parenthesis that is not followed by ? behaves as if it
810  were followed by ?: but named parentheses can still be used for capturing (and  were followed by ?: but named parentheses can still be used for capturing (and
811  they acquire numbers in the usual way). There is no equivalent of this option  they acquire numbers in the usual way). There is no equivalent of this option
812  in Perl.  in Perl.
813    .sp
814      NO_START_OPTIMIZE
815    .sp
816    This is an option that acts at matching time; that is, it is really an option
817    for \fBpcre_exec()\fP or \fBpcre_dfa_exec()\fP. If it is set at compile time,
818    it is remembered with the compiled pattern and assumed at matching time. For
819    details see the discussion of PCRE_NO_START_OPTIMIZE
820    .\" HTML <a href="#execoptions">
821    .\" </a>
822    below.
823    .\"
824    .sp
825      PCRE_UCP
826    .sp
827    This option changes the way PCRE processes \eB, \eb, \eD, \ed, \eS, \es, \eW,
828    \ew, and some of the POSIX character classes. By default, only ASCII characters
829    are recognized, but if PCRE_UCP is set, Unicode properties are used instead to
830    classify characters. More details are given in the section on
831    .\" HTML <a href="pcre.html#genericchartypes">
832    .\" </a>
833    generic character types
834    .\"
835    in the
836    .\" HREF
837    \fBpcrepattern\fP
838    .\"
839    page. If you set PCRE_UCP, matching one of the items it affects takes much
840    longer. The option is available only if PCRE has been compiled with Unicode
841    property support.
842    .sp
843    PCRE_UNGREEDY    PCRE_UNGREEDY
844    .sp
845  This option inverts the "greediness" of the quantifiers so that they are not  This option inverts the "greediness" of the quantifiers so that they are not
846  greedy by default, but become greedy if followed by "?". It is not compatible  greedy by default, but become greedy if followed by "?". It is not compatible
847  with Perl. It can also be set by a (?U) option setting within the pattern.  with Perl. It can also be set by a (?U) option setting within the pattern.
848    .sp
849    PCRE_UTF8    PCRE_UTF8
850    .sp
851  This option causes PCRE to regard both the pattern and the subject as strings  This option causes PCRE to regard both the pattern and the subject as strings
852  of UTF-8 characters instead of single-byte character strings. However, it is  of UTF-8 characters instead of single-byte strings. However, it is available
853  available only if PCRE has been built to include UTF-8 support. If not, the use  only when PCRE is built to include UTF support. If not, the use of this option
854  of this option provokes an error. Details of how this option changes the  provokes an error. Details of how this option changes the behaviour of PCRE are
855  behaviour of PCRE are given in the  given in the
 .\" HTML <a href="pcre.html#utf8support">  
 .\" </a>  
 section on UTF-8 support  
 .\"  
 in the main  
856  .\" HREF  .\" HREF
857  \fBpcre\fR  \fBpcreunicode\fP
858  .\"  .\"
859  page.  page.
860    .sp
861    PCRE_NO_UTF8_CHECK    PCRE_NO_UTF8_CHECK
862    .sp
863  When PCRE_UTF8 is set, the validity of the pattern as a UTF-8 string is  When PCRE_UTF8 is set, the validity of the pattern as a UTF-8
864  automatically checked. If an invalid UTF-8 sequence of bytes is found,  string is automatically checked. There is a discussion about the
865  \fBpcre_compile()\fR returns an error. If you already know that your pattern is  .\" HTML <a href="pcreunicode.html#utf8strings">
866  valid, and you want to skip this check for performance reasons, you can set the  .\" </a>
867  PCRE_NO_UTF8_CHECK option. When it is set, the effect of passing an invalid  validity of UTF-8 strings
868  UTF-8 string as a pattern is undefined. It may cause your program to crash.  .\"
869  Note that there is a similar option for suppressing the checking of subject  in the
870  strings passed to \fBpcre_exec()\fR.  .\" HREF
871    \fBpcreunicode\fP
872    .\"
873  .SH STUDYING A PATTERN  page. If an invalid UTF-8 sequence is found, \fBpcre_compile()\fP returns an
874  .rs  error. If you already know that your pattern is valid, and you want to skip
875  .sp  this check for performance reasons, you can set the PCRE_NO_UTF8_CHECK option.
876  .B pcre_extra *pcre_study(const pcre *\fIcode\fR, int \fIoptions\fR,  When it is set, the effect of passing an invalid UTF-8 string as a pattern is
877  .ti +5n  undefined. It may cause your program to crash. Note that this option can also
878  .B const char **\fIerrptr\fR);  be passed to \fBpcre_exec()\fP and \fBpcre_dfa_exec()\fP, to suppress the
879  .PP  validity checking of subject strings.
880  When a pattern is going to be used several times, it is worth spending more  .
881  time analyzing it in order to speed up the time taken for matching. The  .
882  function \fBpcre_study()\fR takes a pointer to a compiled pattern as its first  .SH "COMPILATION ERROR CODES"
883  argument. If studing the pattern produces additional information that will help  .rs
884  speed up matching, \fBpcre_study()\fR returns a pointer to a \fBpcre_extra\fR  .sp
885  block, in which the \fIstudy_data\fR field points to the results of the study.  The following table lists the error codes than may be returned by
886    \fBpcre_compile2()\fP, along with the error messages that may be returned by
887  The returned value from a \fBpcre_study()\fR can be passed directly to  both compiling functions. Note that error messages are always 8-bit ASCII
888  \fBpcre_exec()\fR. However, the \fBpcre_extra\fR block also contains other  strings, even in 16-bit or 32-bit mode. As PCRE has developed, some error codes
889  fields that can be set by the caller before the block is passed; these are  have fallen out of use. To avoid confusion, they have not been re-used.
890  described below. If studying the pattern does not produce any additional  .sp
891  information, \fBpcre_study()\fR returns NULL. In that circumstance, if the     0  no error
892  calling program wants to pass some of the other fields to \fBpcre_exec()\fR, it     1  \e at end of pattern
893  must set up its own \fBpcre_extra\fR block.     2  \ec at end of pattern
894       3  unrecognized character follows \e
895  The second argument contains option bits. At present, no options are defined     4  numbers out of order in {} quantifier
896  for \fBpcre_study()\fR, and this argument should always be zero.     5  number too big in {} quantifier
897       6  missing terminating ] for character class
898  The third argument for \fBpcre_study()\fR is a pointer for an error message. If     7  invalid escape sequence in character class
899       8  range out of order in character class
900       9  nothing to repeat
901      10  [this code is not in use]
902      11  internal error: unexpected repeat
903      12  unrecognized character after (? or (?-
904      13  POSIX named classes are supported only within a class
905      14  missing )
906      15  reference to non-existent subpattern
907      16  erroffset passed as NULL
908      17  unknown option bit(s) set
909      18  missing ) after comment
910      19  [this code is not in use]
911      20  regular expression is too large
912      21  failed to get memory
913      22  unmatched parentheses
914      23  internal error: code overflow
915      24  unrecognized character after (?<
916      25  lookbehind assertion is not fixed length
917      26  malformed number or name after (?(
918      27  conditional group contains more than two branches
919      28  assertion expected after (?(
920      29  (?R or (?[+-]digits must be followed by )
921      30  unknown POSIX class name
922      31  POSIX collating elements are not supported
923      32  this version of PCRE is compiled without UTF support
924      33  [this code is not in use]
925      34  character value in \ex{...} sequence is too large
926      35  invalid condition (?(0)
927      36  \eC not allowed in lookbehind assertion
928      37  PCRE does not support \eL, \el, \eN{name}, \eU, or \eu
929      38  number after (?C is > 255
930      39  closing ) for (?C expected
931      40  recursive call could loop indefinitely
932      41  unrecognized character after (?P
933      42  syntax error in subpattern name (missing terminator)
934      43  two named subpatterns have the same name
935      44  invalid UTF-8 string (specifically UTF-8)
936      45  support for \eP, \ep, and \eX has not been compiled
937      46  malformed \eP or \ep sequence
938      47  unknown property name after \eP or \ep
939      48  subpattern name is too long (maximum 32 characters)
940      49  too many named subpatterns (maximum 10000)
941      50  [this code is not in use]
942      51  octal value is greater than \e377 in 8-bit non-UTF-8 mode
943      52  internal error: overran compiling workspace
944      53  internal error: previously-checked referenced subpattern
945            not found
946      54  DEFINE group contains more than one branch
947      55  repeating a DEFINE group is not allowed
948      56  inconsistent NEWLINE options
949      57  \eg is not followed by a braced, angle-bracketed, or quoted
950            name/number or by a plain number
951      58  a numbered reference must not be zero
952      59  an argument is not allowed for (*ACCEPT), (*FAIL), or (*COMMIT)
953      60  (*VERB) not recognized
954      61  number is too big
955      62  subpattern name expected
956      63  digit expected after (?+
957      64  ] is an invalid data character in JavaScript compatibility mode
958      65  different names for subpatterns of the same number are
959            not allowed
960      66  (*MARK) must have an argument
961      67  this version of PCRE is not compiled with Unicode property
962            support
963      68  \ec must be followed by an ASCII character
964      69  \ek is not followed by a braced, angle-bracketed, or quoted name
965      70  internal error: unknown opcode in find_fixedlength()
966      71  \eN is not supported in a class
967      72  too many forward references
968      73  disallowed Unicode code point (>= 0xd800 && <= 0xdfff)
969      74  invalid UTF-16 string (specifically UTF-16)
970      75  name is too long in (*MARK), (*PRUNE), (*SKIP), or (*THEN)
971      76  character value in \eu.... sequence is too large
972      77  invalid UTF-32 string (specifically UTF-32)
973    .sp
974    The numbers 32 and 10000 in errors 48 and 49 are defaults; different values may
975    be used if the limits were changed when PCRE was built.
976    .
977    .
978    .\" HTML <a name="studyingapattern"></a>
979    .SH "STUDYING A PATTERN"
980    .rs
981    .sp
982    .B pcre_extra *pcre_study(const pcre *\fIcode\fP, int \fIoptions\fP
983    .ti +5n
984    .B const char **\fIerrptr\fP);
985    .PP
986    If a compiled pattern is going to be used several times, it is worth spending
987    more time analyzing it in order to speed up the time taken for matching. The
988    function \fBpcre_study()\fP takes a pointer to a compiled pattern as its first
989    argument. If studying the pattern produces additional information that will
990    help speed up matching, \fBpcre_study()\fP returns a pointer to a
991    \fBpcre_extra\fP block, in which the \fIstudy_data\fP field points to the
992    results of the study.
993    .P
994    The returned value from \fBpcre_study()\fP can be passed directly to
995    \fBpcre_exec()\fP or \fBpcre_dfa_exec()\fP. However, a \fBpcre_extra\fP block
996    also contains other fields that can be set by the caller before the block is
997    passed; these are described
998    .\" HTML <a href="#extradata">
999    .\" </a>
1000    below
1001    .\"
1002    in the section on matching a pattern.
1003    .P
1004    If studying the pattern does not produce any useful information,
1005    \fBpcre_study()\fP returns NULL by default. In that circumstance, if the
1006    calling program wants to pass any of the other fields to \fBpcre_exec()\fP or
1007    \fBpcre_dfa_exec()\fP, it must set up its own \fBpcre_extra\fP block. However,
1008    if \fBpcre_study()\fP is called with the PCRE_STUDY_EXTRA_NEEDED option, it
1009    returns a \fBpcre_extra\fP block even if studying did not find any additional
1010    information. It may still return NULL, however, if an error occurs in
1011    \fBpcre_study()\fP.
1012    .P
1013    The second argument of \fBpcre_study()\fP contains option bits. There are three
1014    further options in addition to PCRE_STUDY_EXTRA_NEEDED:
1015    .sp
1016      PCRE_STUDY_JIT_COMPILE
1017      PCRE_STUDY_JIT_PARTIAL_HARD_COMPILE
1018      PCRE_STUDY_JIT_PARTIAL_SOFT_COMPILE
1019    .sp
1020    If any of these are set, and the just-in-time compiler is available, the
1021    pattern is further compiled into machine code that executes much faster than
1022    the \fBpcre_exec()\fP interpretive matching function. If the just-in-time
1023    compiler is not available, these options are ignored. All undefined bits in the
1024    \fIoptions\fP argument must be zero.
1025    .P
1026    JIT compilation is a heavyweight optimization. It can take some time for
1027    patterns to be analyzed, and for one-off matches and simple patterns the
1028    benefit of faster execution might be offset by a much slower study time.
1029    Not all patterns can be optimized by the JIT compiler. For those that cannot be
1030    handled, matching automatically falls back to the \fBpcre_exec()\fP
1031    interpreter. For more details, see the
1032    .\" HREF
1033    \fBpcrejit\fP
1034    .\"
1035    documentation.
1036    .P
1037    The third argument for \fBpcre_study()\fP is a pointer for an error message. If
1038  studying succeeds (even if no data is returned), the variable it points to is  studying succeeds (even if no data is returned), the variable it points to is
1039  set to NULL. Otherwise it points to a textual error message. You should  set to NULL. Otherwise it is set to point to a textual error message. This is a
1040  therefore test the error pointer for NULL after calling \fBpcre_study()\fR, to  static string that is part of the library. You must not try to free it. You
1041  be sure that it has run successfully.  should test the error pointer for NULL after calling \fBpcre_study()\fP, to be
1042    sure that it has run successfully.
1043  This is a typical call to \fBpcre_study\fR():  .P
1044    When you are finished with a pattern, you can free the memory used for the
1045    pcre_extra *pe;  study data by calling \fBpcre_free_study()\fP. This function was added to the
1046    pe = pcre_study(  API for release 8.20. For earlier versions, the memory could be freed with
1047    \fBpcre_free()\fP, just like the pattern itself. This will still work in cases
1048    where JIT optimization is not used, but it is advisable to change to the new
1049    function when convenient.
1050    .P
1051    This is a typical way in which \fBpcre_study\fP() is used (except that in a
1052    real application there should be tests for errors):
1053    .sp
1054      int rc;
1055      pcre *re;
1056      pcre_extra *sd;
1057      re = pcre_compile("pattern", 0, &error, &erroroffset, NULL);
1058      sd = pcre_study(
1059      re,             /* result of pcre_compile() */      re,             /* result of pcre_compile() */
1060      0,              /* no options exist */      0,              /* no options */
1061      &error);        /* set to NULL or points to a message */      &error);        /* set to NULL or points to a message */
1062      rc = pcre_exec(   /* see below for details of pcre_exec() options */
1063  At present, studying a pattern is useful only for non-anchored patterns that do      re, sd, "subject", 7, 0, 0, ovector, 30);
1064  not have a single fixed starting character. A bitmap of possible starting    ...
1065  characters is created.    pcre_free_study(sd);
1066      pcre_free(re);
1067    .sp
1068    Studying a pattern does two things: first, a lower bound for the length of
1069    subject string that is needed to match the pattern is computed. This does not
1070    mean that there are any strings of that length that match, but it does
1071    guarantee that no shorter strings match. The value is used to avoid wasting
1072    time by trying to match strings that are shorter than the lower bound. You can
1073    find out the value in a calling program via the \fBpcre_fullinfo()\fP function.
1074    .P
1075    Studying a pattern is also useful for non-anchored patterns that do not have a
1076    single fixed starting character. A bitmap of possible starting bytes is
1077    created. This speeds up finding a position in the subject at which to start
1078    matching. (In 16-bit mode, the bitmap is used for 16-bit values less than 256.
1079    In 32-bit mode, the bitmap is used for 32-bit values less than 256.)
1080    .P
1081    These two optimizations apply to both \fBpcre_exec()\fP and
1082    \fBpcre_dfa_exec()\fP, and the information is also used by the JIT compiler.
1083    The optimizations can be disabled by setting the PCRE_NO_START_OPTIMIZE option
1084    when calling \fBpcre_exec()\fP or \fBpcre_dfa_exec()\fP, but if this is done,
1085    JIT execution is also disabled. You might want to do this if your pattern
1086    contains callouts or (*MARK) and you want to make use of these facilities in
1087    cases where matching fails. See the discussion of PCRE_NO_START_OPTIMIZE
1088    .\" HTML <a href="#execoptions">
1089    .\" </a>
1090    below.
1091    .\"
1092    .
1093    .
1094  .\" HTML <a name="localesupport"></a>  .\" HTML <a name="localesupport"></a>
1095  .SH LOCALE SUPPORT  .SH "LOCALE SUPPORT"
1096  .rs  .rs
1097  .sp  .sp
1098  PCRE handles caseless matching, and determines whether characters are letters,  PCRE handles caseless matching, and determines whether characters are letters,
1099  digits, or whatever, by reference to a set of tables. When running in UTF-8  digits, or whatever, by reference to a set of tables, indexed by character
1100  mode, this applies only to characters with codes less than 256. The library  value. When running in UTF-8 mode, this applies only to characters
1101  contains a default set of tables that is created in the default C locale when  with codes less than 128. By default, higher-valued codes never match escapes
1102  PCRE is compiled. This is used when the final argument of \fBpcre_compile()\fR  such as \ew or \ed, but they can be tested with \ep if PCRE is built with
1103  is NULL, and is sufficient for many applications.  Unicode character property support. Alternatively, the PCRE_UCP option can be
1104    set at compile time; this causes \ew and friends to use Unicode property
1105  An alternative set of tables can, however, be supplied. Such tables are built  support instead of built-in tables. The use of locales with Unicode is
1106  by calling the \fBpcre_maketables()\fR function, which has no arguments, in the  discouraged. If you are handling characters with codes greater than 128, you
1107  relevant locale. The result can then be passed to \fBpcre_compile()\fR as often  should either use UTF-8 and Unicode, or use locales, but not try to mix the
1108  as necessary. For example, to build and use tables that are appropriate for the  two.
1109  French locale (where accented characters with codes greater than 128 are  .P
1110  treated as letters), the following code could be used:  PCRE contains an internal set of tables that are used when the final argument
1111    of \fBpcre_compile()\fP is NULL. These are sufficient for many applications.
1112    setlocale(LC_CTYPE, "fr");  Normally, the internal tables recognize only ASCII characters. However, when
1113    PCRE is built, it is possible to cause the internal tables to be rebuilt in the
1114    default "C" locale of the local system, which may cause them to be different.
1115    .P
1116    The internal tables can always be overridden by tables supplied by the
1117    application that calls PCRE. These may be created in a different locale from
1118    the default. As more and more applications change to using Unicode, the need
1119    for this locale support is expected to die away.
1120    .P
1121    External tables are built by calling the \fBpcre_maketables()\fP function,
1122    which has no arguments, in the relevant locale. The result can then be passed
1123    to \fBpcre_compile()\fP or \fBpcre_exec()\fP as often as necessary. For
1124    example, to build and use tables that are appropriate for the French locale
1125    (where accented characters with values greater than 128 are treated as letters),
1126    the following code could be used:
1127    .sp
1128      setlocale(LC_CTYPE, "fr_FR");
1129    tables = pcre_maketables();    tables = pcre_maketables();
1130    re = pcre_compile(..., tables);    re = pcre_compile(..., tables);
1131    .sp
1132  The tables are built in memory that is obtained via \fBpcre_malloc\fR. The  The locale name "fr_FR" is used on Linux and other Unix-like systems; if you
1133  pointer that is passed to \fBpcre_compile\fR is saved with the compiled  are using Windows, the name for the French locale is "french".
1134  pattern, and the same tables are used via this pointer by \fBpcre_study()\fR  .P
1135  and \fBpcre_exec()\fR. Thus, for any single pattern, compilation, studying and  When \fBpcre_maketables()\fP runs, the tables are built in memory that is
1136  matching all happen in the same locale, but different patterns can be compiled  obtained via \fBpcre_malloc\fP. It is the caller's responsibility to ensure
1137  in different locales. It is the caller's responsibility to ensure that the  that the memory containing the tables remains available for as long as it is
1138  memory containing the tables remains available for as long as it is needed.  needed.
1139    .P
1140  .SH INFORMATION ABOUT A PATTERN  The pointer that is passed to \fBpcre_compile()\fP is saved with the compiled
1141  .rs  pattern, and the same tables are used via this pointer by \fBpcre_study()\fP
1142  .sp  and normally also by \fBpcre_exec()\fP. Thus, by default, for any single
1143  .B int pcre_fullinfo(const pcre *\fIcode\fR, "const pcre_extra *\fIextra\fR,"  pattern, compilation, studying and matching all happen in the same locale, but
1144  .ti +5n  different patterns can be compiled in different locales.
1145  .B int \fIwhat\fR, void *\fIwhere\fR);  .P
1146  .PP  It is possible to pass a table pointer or NULL (indicating the use of the
1147  The \fBpcre_fullinfo()\fR function returns information about a compiled  internal tables) to \fBpcre_exec()\fP. Although not intended for this purpose,
1148  pattern. It replaces the obsolete \fBpcre_info()\fR function, which is  this facility could be used to match a pattern in a different locale from the
1149  nevertheless retained for backwards compability (and is documented below).  one in which it was compiled. Passing table pointers at run time is discussed
1150    below in the section on matching a pattern.
1151  The first argument for \fBpcre_fullinfo()\fR is a pointer to the compiled  .
1152  pattern. The second argument is the result of \fBpcre_study()\fR, or NULL if  .
1153    .\" HTML <a name="infoaboutpattern"></a>
1154    .SH "INFORMATION ABOUT A PATTERN"
1155    .rs
1156    .sp
1157    .B int pcre_fullinfo(const pcre *\fIcode\fP, "const pcre_extra *\fIextra\fP,"
1158    .ti +5n
1159    .B int \fIwhat\fP, void *\fIwhere\fP);
1160    .PP
1161    The \fBpcre_fullinfo()\fP function returns information about a compiled
1162    pattern. It replaces the \fBpcre_info()\fP function, which was removed from the
1163    library at version 8.30, after more than 10 years of obsolescence.
1164    .P
1165    The first argument for \fBpcre_fullinfo()\fP is a pointer to the compiled
1166    pattern. The second argument is the result of \fBpcre_study()\fP, or NULL if
1167  the pattern was not studied. The third argument specifies which piece of  the pattern was not studied. The third argument specifies which piece of
1168  information is required, and the fourth argument is a pointer to a variable  information is required, and the fourth argument is a pointer to a variable
1169  to receive the data. The yield of the function is zero for success, or one of  to receive the data. The yield of the function is zero for success, or one of
1170  the following negative numbers:  the following negative numbers:
1171    .sp
1172    PCRE_ERROR_NULL       the argument \fIcode\fR was NULL    PCRE_ERROR_NULL           the argument \fIcode\fP was NULL
1173                          the argument \fIwhere\fR was NULL                              the argument \fIwhere\fP was NULL
1174    PCRE_ERROR_BADMAGIC   the "magic number" was not found    PCRE_ERROR_BADMAGIC       the "magic number" was not found
1175    PCRE_ERROR_BADOPTION  the value of \fIwhat\fR was invalid    PCRE_ERROR_BADENDIANNESS  the pattern was compiled with different
1176                                endianness
1177  Here is a typical call of \fBpcre_fullinfo()\fR, to obtain the length of the    PCRE_ERROR_BADOPTION      the value of \fIwhat\fP was invalid
1178  compiled pattern:  .sp
1179    The "magic number" is placed at the start of each compiled pattern as an simple
1180    check against passing an arbitrary memory pointer. The endianness error can
1181    occur if a compiled pattern is saved and reloaded on a different host. Here is
1182    a typical call of \fBpcre_fullinfo()\fP, to obtain the length of the compiled
1183    pattern:
1184    .sp
1185    int rc;    int rc;
1186    unsigned long int length;    size_t length;
1187    rc = pcre_fullinfo(    rc = pcre_fullinfo(
1188      re,               /* result of pcre_compile() */      re,               /* result of pcre_compile() */
1189      pe,               /* result of pcre_study(), or NULL */      sd,               /* result of pcre_study(), or NULL */
1190      PCRE_INFO_SIZE,   /* what is required */      PCRE_INFO_SIZE,   /* what is required */
1191      &length);         /* where to put the data */      &length);         /* where to put the data */
1192    .sp
1193  The possible values for the third argument are defined in \fBpcre.h\fR, and are  The possible values for the third argument are defined in \fBpcre.h\fP, and are
1194  as follows:  as follows:
1195    .sp
1196    PCRE_INFO_BACKREFMAX    PCRE_INFO_BACKREFMAX
1197    .sp
1198  Return the number of the highest back reference in the pattern. The fourth  Return the number of the highest back reference in the pattern. The fourth
1199  argument should point to an \fBint\fR variable. Zero is returned if there are  argument should point to an \fBint\fP variable. Zero is returned if there are
1200  no back references.  no back references.
1201    .sp
1202    PCRE_INFO_CAPTURECOUNT    PCRE_INFO_CAPTURECOUNT
1203    .sp
1204  Return the number of capturing subpatterns in the pattern. The fourth argument  Return the number of capturing subpatterns in the pattern. The fourth argument
1205  should point to an \fbint\fR variable.  should point to an \fBint\fP variable.
1206    .sp
1207      PCRE_INFO_DEFAULT_TABLES
1208    .sp
1209    Return a pointer to the internal default character tables within PCRE. The
1210    fourth argument should point to an \fBunsigned char *\fP variable. This
1211    information call is provided for internal use by the \fBpcre_study()\fP
1212    function. External callers can cause PCRE to use its internal tables by passing
1213    a NULL table pointer.
1214    .sp
1215    PCRE_INFO_FIRSTBYTE    PCRE_INFO_FIRSTBYTE
1216    .sp
1217  Return information about the first byte of any matched string, for a  Return information about the first data unit of any matched string, for a
1218  non-anchored pattern. (This option used to be called PCRE_INFO_FIRSTCHAR; the  non-anchored pattern. (The name of this option refers to the 8-bit library,
1219  old name is still recognized for backwards compatibility.)  where data units are bytes.) The fourth argument should point to an \fBint\fP
1220    variable.
1221  If there is a fixed first byte, e.g. from a pattern such as (cat|cow|coyote),  .P
1222  it is returned in the integer pointed to by \fIwhere\fR. Otherwise, if either  If there is a fixed first value, for example, the letter "c" from a pattern
1223    such as (cat|cow|coyote), its value is returned. In the 8-bit library, the
1224    value is always less than 256. In the 16-bit library the value can be up to
1225    0xffff. In the 32-bit library the value can be up to 0x10ffff.
1226    .P
1227    If there is no fixed first value, and if either
1228    .sp
1229  (a) the pattern was compiled with the PCRE_MULTILINE option, and every branch  (a) the pattern was compiled with the PCRE_MULTILINE option, and every branch
1230  starts with "^", or  starts with "^", or
1231    .sp
1232  (b) every branch of the pattern starts with ".*" and PCRE_DOTALL is not set  (b) every branch of the pattern starts with ".*" and PCRE_DOTALL is not set
1233  (if it were set, the pattern would be anchored),  (if it were set, the pattern would be anchored),
1234    .sp
1235  -1 is returned, indicating that the pattern matches only at the start of a  -1 is returned, indicating that the pattern matches only at the start of a
1236  subject string or after any newline within the string. Otherwise -2 is  subject string or after any newline within the string. Otherwise -2 is
1237  returned. For anchored patterns, -2 is returned.  returned. For anchored patterns, -2 is returned.
1238    .P
1239    Since for the 32-bit library using the non-UTF-32 mode, this function is unable
1240    to return the full 32-bit range of the character, this value is deprecated;
1241    instead the PCRE_INFO_FIRSTCHARACTERFLAGS and PCRE_INFO_FIRSTCHARACTER values should
1242    be used.
1243    .sp
1244    PCRE_INFO_FIRSTTABLE    PCRE_INFO_FIRSTTABLE
1245    .sp
1246  If the pattern was studied, and this resulted in the construction of a 256-bit  If the pattern was studied, and this resulted in the construction of a 256-bit
1247  table indicating a fixed set of bytes for the first byte in any matching  table indicating a fixed set of values for the first data unit in any matching
1248  string, a pointer to the table is returned. Otherwise NULL is returned. The  string, a pointer to the table is returned. Otherwise NULL is returned. The
1249  fourth argument should point to an \fBunsigned char *\fR variable.  fourth argument should point to an \fBunsigned char *\fP variable.
1250    .sp
1251      PCRE_INFO_HASCRORLF
1252    .sp
1253    Return 1 if the pattern contains any explicit matches for CR or LF characters,
1254    otherwise 0. The fourth argument should point to an \fBint\fP variable. An
1255    explicit match is either a literal CR or LF character, or \er or \en.
1256    .sp
1257      PCRE_INFO_JCHANGED
1258    .sp
1259    Return 1 if the (?J) or (?-J) option setting is used in the pattern, otherwise
1260    0. The fourth argument should point to an \fBint\fP variable. (?J) and
1261    (?-J) set and unset the local PCRE_DUPNAMES option, respectively.
1262    .sp
1263      PCRE_INFO_JIT
1264    .sp
1265    Return 1 if the pattern was studied with one of the JIT options, and
1266    just-in-time compiling was successful. The fourth argument should point to an
1267    \fBint\fP variable. A return value of 0 means that JIT support is not available
1268    in this version of PCRE, or that the pattern was not studied with a JIT option,
1269    or that the JIT compiler could not handle this particular pattern. See the
1270    .\" HREF
1271    \fBpcrejit\fP
1272    .\"
1273    documentation for details of what can and cannot be handled.
1274    .sp
1275      PCRE_INFO_JITSIZE
1276    .sp
1277    If the pattern was successfully studied with a JIT option, return the size of
1278    the JIT compiled code, otherwise return zero. The fourth argument should point
1279    to a \fBsize_t\fP variable.
1280    .sp
1281    PCRE_INFO_LASTLITERAL    PCRE_INFO_LASTLITERAL
1282    .sp
1283  Return the value of the rightmost literal byte that must exist in any matched  Return the value of the rightmost literal data unit that must exist in any
1284  string, other than at its start, if such a byte has been recorded. The fourth  matched string, other than at its start, if such a value has been recorded. The
1285  argument should point to an \fBint\fR variable. If there is no such byte, -1 is  fourth argument should point to an \fBint\fP variable. If there is no such
1286  returned. For anchored patterns, a last literal byte is recorded only if it  value, -1 is returned. For anchored patterns, a last literal value is recorded
1287  follows something of variable length. For example, for the pattern  only if it follows something of variable length. For example, for the pattern
1288  /^a\\d+z\\d+/ the returned value is "z", but for /^a\\dz\\d/ the returned value  /^a\ed+z\ed+/ the returned value is "z", but for /^a\edz\ed/ the returned value
1289  is -1.  is -1.
1290    .P
1291    Since for the 32-bit library using the non-UTF-32 mode, this function is unable
1292    to return the full 32-bit range of the character, this value is deprecated;
1293    instead the PCRE_INFO_REQUIREDCHARFLAGS and PCRE_INFO_REQUIREDCHAR values should
1294    be used.
1295    .sp
1296      PCRE_INFO_MAXLOOKBEHIND
1297    .sp
1298    Return the number of characters (NB not bytes) in the longest lookbehind
1299    assertion in the pattern. Note that the simple assertions \eb and \eB require a
1300    one-character lookbehind. This information is useful when doing multi-segment
1301    matching using the partial matching facilities.
1302    .sp
1303      PCRE_INFO_MINLENGTH
1304    .sp
1305    If the pattern was studied and a minimum length for matching subject strings
1306    was computed, its value is returned. Otherwise the returned value is -1. The
1307    value is a number of characters, which in UTF-8 mode may be different from the
1308    number of bytes. The fourth argument should point to an \fBint\fP variable. A
1309    non-negative value is a lower bound to the length of any matching string. There
1310    may not be any strings of that length that do actually match, but every string
1311    that does match is at least that long.
1312    .sp
1313    PCRE_INFO_NAMECOUNT    PCRE_INFO_NAMECOUNT
1314    PCRE_INFO_NAMEENTRYSIZE    PCRE_INFO_NAMEENTRYSIZE
1315    PCRE_INFO_NAMETABLE    PCRE_INFO_NAMETABLE
1316    .sp
1317  PCRE supports the use of named as well as numbered capturing parentheses. The  PCRE supports the use of named as well as numbered capturing parentheses. The
1318  names are just an additional way of identifying the parentheses, which still  names are just an additional way of identifying the parentheses, which still
1319  acquire a number. A caller that wants to extract data from a named subpattern  acquire numbers. Several convenience functions such as
1320  must convert the name to a number in order to access the correct pointers in  \fBpcre_get_named_substring()\fP are provided for extracting captured
1321  the output vector (described with \fBpcre_exec()\fR below). In order to do  substrings by name. It is also possible to extract the data directly, by first
1322  this, it must first use these three values to obtain the name-to-number mapping  converting the name to a number in order to access the correct pointers in the
1323  table for the pattern.  output vector (described with \fBpcre_exec()\fP below). To do the conversion,
1324    you need to use the name-to-number map, which is described by these three
1325    values.
1326    .P
1327  The map consists of a number of fixed-size entries. PCRE_INFO_NAMECOUNT gives  The map consists of a number of fixed-size entries. PCRE_INFO_NAMECOUNT gives
1328  the number of entries, and PCRE_INFO_NAMEENTRYSIZE gives the size of each  the number of entries, and PCRE_INFO_NAMEENTRYSIZE gives the size of each
1329  entry; both of these return an \fBint\fR value. The entry size depends on the  entry; both of these return an \fBint\fP value. The entry size depends on the
1330  length of the longest name. PCRE_INFO_NAMETABLE returns a pointer to the first  length of the longest name. PCRE_INFO_NAMETABLE returns a pointer to the first
1331  entry of the table (a pointer to \fBchar\fR). The first two bytes of each entry  entry of the table. This is a pointer to \fBchar\fP in the 8-bit library, where
1332  are the number of the capturing parenthesis, most significant byte first. The  the first two bytes of each entry are the number of the capturing parenthesis,
1333  rest of the entry is the corresponding name, zero terminated. The names are in  most significant byte first. In the 16-bit library, the pointer points to
1334  alphabetical order. For example, consider the following pattern (assume  16-bit data units, the first of which contains the parenthesis number.
1335  PCRE_EXTENDED is set, so white space - including newlines - is ignored):  In the 32-bit library, the pointer points to 32-bit data units, the first of
1336    which contains the parenthesis number. The rest
1337    (?P<date> (?P<year>(\\d\\d)?\\d\\d) -  of the entry is the corresponding name, zero terminated.
1338    (?P<month>\\d\\d) - (?P<day>\\d\\d) )  .P
1339    The names are in alphabetical order. Duplicate names may appear if (?| is used
1340    to create multiple groups with the same number, as described in the
1341    .\" HTML <a href="pcrepattern.html#dupsubpatternnumber">
1342    .\" </a>
1343    section on duplicate subpattern numbers
1344    .\"
1345    in the
1346    .\" HREF
1347    \fBpcrepattern\fP
1348    .\"
1349    page. Duplicate names for subpatterns with different numbers are permitted only
1350    if PCRE_DUPNAMES is set. In all cases of duplicate names, they appear in the
1351    table in the order in which they were found in the pattern. In the absence of
1352    (?| this is the order of increasing number; when (?| is used this is not
1353    necessarily the case because later subpatterns may have lower numbers.
1354    .P
1355    As a simple example of the name/number table, consider the following pattern
1356    after compilation by the 8-bit library (assume PCRE_EXTENDED is set, so white
1357    space - including newlines - is ignored):
1358    .sp
1359    .\" JOIN
1360      (?<date> (?<year>(\ed\ed)?\ed\ed) -
1361      (?<month>\ed\ed) - (?<day>\ed\ed) )
1362    .sp
1363  There are four named subpatterns, so the table has four entries, and each entry  There are four named subpatterns, so the table has four entries, and each entry
1364  in the table is eight bytes long. The table is as follows, with non-printing  in the table is eight bytes long. The table is as follows, with non-printing
1365  bytes shows in hex, and undefined bytes shown as ??:  bytes shows in hexadecimal, and undefined bytes shown as ??:
1366    .sp
1367    00 01 d  a  t  e  00 ??    00 01 d  a  t  e  00 ??
1368    00 05 d  a  y  00 ?? ??    00 05 d  a  y  00 ?? ??
1369    00 04 m  o  n  t  h  00    00 04 m  o  n  t  h  00
1370    00 02 y  e  a  r  00 ??    00 02 y  e  a  r  00 ??
1371    .sp
1372  When writing code to extract data from named subpatterns, remember that the  When writing code to extract data from named subpatterns using the
1373  length of each entry may be different for each compiled pattern.  name-to-number map, remember that the length of the entries is likely to be
1374    different for each compiled pattern.
1375    .sp
1376      PCRE_INFO_OKPARTIAL
1377    .sp
1378    Return 1 if the pattern can be used for partial matching with
1379    \fBpcre_exec()\fP, otherwise 0. The fourth argument should point to an
1380    \fBint\fP variable. From release 8.00, this always returns 1, because the
1381    restrictions that previously applied to partial matching have been lifted. The
1382    .\" HREF
1383    \fBpcrepartial\fP
1384    .\"
1385    documentation gives details of partial matching.
1386    .sp
1387    PCRE_INFO_OPTIONS    PCRE_INFO_OPTIONS
1388    .sp
1389  Return a copy of the options with which the pattern was compiled. The fourth  Return a copy of the options with which the pattern was compiled. The fourth
1390  argument should point to an \fBunsigned long int\fR variable. These option bits  argument should point to an \fBunsigned long int\fP variable. These option bits
1391  are those specified in the call to \fBpcre_compile()\fR, modified by any  are those specified in the call to \fBpcre_compile()\fP, modified by any
1392  top-level option settings within the pattern itself.  top-level option settings at the start of the pattern itself. In other words,
1393    they are the options that will be in force when matching starts. For example,
1394    if the pattern /(?im)abc(?-i)d/ is compiled with the PCRE_EXTENDED option, the
1395    result is PCRE_CASELESS, PCRE_MULTILINE, and PCRE_EXTENDED.
1396    .P
1397  A pattern is automatically anchored by PCRE if all of its top-level  A pattern is automatically anchored by PCRE if all of its top-level
1398  alternatives begin with one of the following:  alternatives begin with one of the following:
1399    .sp
1400    ^     unless PCRE_MULTILINE is set    ^     unless PCRE_MULTILINE is set
1401    \\A    always    \eA    always
1402    \\G    always    \eG    always
1403    .\" JOIN
1404    .*    if PCRE_DOTALL is set and there are no back    .*    if PCRE_DOTALL is set and there are no back
1405            references to the subpattern in which .* appears            references to the subpattern in which .* appears
1406    .sp
1407  For such patterns, the PCRE_ANCHORED bit is set in the options returned by  For such patterns, the PCRE_ANCHORED bit is set in the options returned by
1408  \fBpcre_fullinfo()\fR.  \fBpcre_fullinfo()\fP.
1409    .sp
1410    PCRE_INFO_SIZE    PCRE_INFO_SIZE
1411    .sp
1412  Return the size of the compiled pattern, that is, the value that was passed as  Return the size of the compiled pattern in bytes (for both libraries). The
1413  the argument to \fBpcre_malloc()\fR when PCRE was getting memory in which to  fourth argument should point to a \fBsize_t\fP variable. This value does not
1414  place the compiled data. The fourth argument should point to a \fBsize_t\fR  include the size of the \fBpcre\fP structure that is returned by
1415  variable.  \fBpcre_compile()\fP. The value that is passed as the argument to
1416    \fBpcre_malloc()\fP when \fBpcre_compile()\fP is getting memory in which to
1417    PCRE_INFO_STUDYSIZE  place the compiled data is the value returned by this option plus the size of
1418    the \fBpcre\fP structure. Studying a compiled pattern, with or without JIT,
1419  Returns the size of the data block pointed to by the \fIstudy_data\fR field in  does not alter the value returned by this option.
1420  a \fBpcre_extra\fR block. That is, it is the value that was passed to  .sp
1421  \fBpcre_malloc()\fR when PCRE was getting memory into which to place the data    PCRE_INFO_STUDYSIZE
1422  created by \fBpcre_study()\fR. The fourth argument should point to a  .sp
1423  \fBsize_t\fR variable.  Return the size in bytes of the data block pointed to by the \fIstudy_data\fP
1424    field in a \fBpcre_extra\fP block. If \fBpcre_extra\fP is NULL, or there is no
1425  .SH OBSOLETE INFO FUNCTION  study data, zero is returned. The fourth argument should point to a
1426  .rs  \fBsize_t\fP variable. The \fIstudy_data\fP field is set by \fBpcre_study()\fP
1427  .sp  to record information that will speed up matching (see the section entitled
1428  .B int pcre_info(const pcre *\fIcode\fR, int *\fIoptptr\fR, int  .\" HTML <a href="#studyingapattern">
1429  .B *\fIfirstcharptr\fR);  .\" </a>
1430  .PP  "Studying a pattern"
1431  The \fBpcre_info()\fR function is now obsolete because its interface is too  .\"
1432  restrictive to return all the available data about a compiled pattern. New  above). The format of the \fIstudy_data\fP block is private, but its length
1433  programs should use \fBpcre_fullinfo()\fR instead. The yield of  is made available via this option so that it can be saved and restored (see the
1434  \fBpcre_info()\fR is the number of capturing subpatterns, or one of the  .\" HREF
1435  following negative numbers:  \fBpcreprecompile\fP
1436    .\"
1437    PCRE_ERROR_NULL       the argument \fIcode\fR was NULL  documentation for details).
1438    PCRE_ERROR_BADMAGIC   the "magic number" was not found  .sp
1439      PCRE_INFO_FIRSTCHARACTERFLAGS
1440  If the \fIoptptr\fR argument is not NULL, a copy of the options with which the  .sp
1441  pattern was compiled is placed in the integer it points to (see  Return information about the first data unit of any matched string, for a
1442  PCRE_INFO_OPTIONS above).  non-anchored pattern. The fourth argument should point to an \fBint\fP
1443    variable.
1444  If the pattern is not anchored and the \fIfirstcharptr\fR argument is not NULL,  .P
1445  it is used to pass back information about the first character of any matched  If there is a fixed first value, for example, the letter "c" from a pattern
1446  string (see PCRE_INFO_FIRSTBYTE above).  such as (cat|cow|coyote), 1 is returned, and the character value can be
1447    retrieved using PCRE_INFO_FIRSTCHARACTER.
1448  .SH MATCHING A PATTERN  .P
1449  .rs  If there is no fixed first value, and if either
1450  .sp  .sp
1451  .B int pcre_exec(const pcre *\fIcode\fR, "const pcre_extra *\fIextra\fR,"  (a) the pattern was compiled with the PCRE_MULTILINE option, and every branch
1452  .ti +5n  starts with "^", or
1453  .B "const char *\fIsubject\fR," int \fIlength\fR, int \fIstartoffset\fR,  .sp
1454  .ti +5n  (b) every branch of the pattern starts with ".*" and PCRE_DOTALL is not set
1455  .B int \fIoptions\fR, int *\fIovector\fR, int \fIovecsize\fR);  (if it were set, the pattern would be anchored),
1456  .PP  .sp
1457  The function \fBpcre_exec()\fR is called to match a subject string against a  2 is returned, indicating that the pattern matches only at the start of a
1458  pre-compiled pattern, which is passed in the \fIcode\fR argument. If the  subject string or after any newline within the string. Otherwise 0 is
1459  pattern has been studied, the result of the study should be passed in the  returned. For anchored patterns, 0 is returned.
1460  \fIextra\fR argument.  .sp
1461      PCRE_INFO_FIRSTCHARACTER
1462  Here is an example of a simple call to \fBpcre_exec()\fR:  .sp
1463    Return the fixed first character value, if PCRE_INFO_FIRSTCHARACTERFLAGS returned 1;
1464    otherwise returns 0. The fourth argument should point to an \fBuint_t\fP
1465    variable.
1466    .P
1467    In the 8-bit library, the value is always less than 256. In the 16-bit library
1468    the value can be up to 0xffff. In the 32-bit library in UTF-32 mode the value
1469    can be up to 0x10ffff, and up to 0xffffffff when not using UTF-32 mode.
1470    .P
1471    If there is no fixed first value, and if either
1472    .sp
1473    (a) the pattern was compiled with the PCRE_MULTILINE option, and every branch
1474    starts with "^", or
1475    .sp
1476    (b) every branch of the pattern starts with ".*" and PCRE_DOTALL is not set
1477    (if it were set, the pattern would be anchored),
1478    .sp
1479    -1 is returned, indicating that the pattern matches only at the start of a
1480    subject string or after any newline within the string. Otherwise -2 is
1481    returned. For anchored patterns, -2 is returned.
1482    .sp
1483      PCRE_INFO_REQUIREDCHARFLAGS
1484    .sp
1485    Returns 1 if there is a rightmost literal data unit that must exist in any matched
1486    string, other than at its start. The fourth argument should  point to an \fBint\fP
1487    variable. If there is no such value, 0 is returned. If returning 1, the character
1488    value itself can be retrieved using PCRE_INFO_REQUIREDCHAR.
1489    .P
1490    For anchored patterns, a last literal value is recorded only if it follows something
1491    of variable length. For example, for the pattern /^a\ed+z\ed+/ the returned value
1492    1 (with "z" returned from PCRE_INFO_REQUIREDCHAR), but for /^a\edz\ed/ the returned
1493    value is 0.
1494    .sp
1495      PCRE_INFO_REQUIREDCHAR
1496    .sp
1497    Return the value of the rightmost literal data unit that must exist in any
1498    matched string, other than at its start, if such a value has been recorded. The
1499    fourth argument should point to an \fBuint32_t\fP variable. If there is no such
1500    value, 0 is returned.
1501    .
1502    .
1503    .SH "REFERENCE COUNTS"
1504    .rs
1505    .sp
1506    .B int pcre_refcount(pcre *\fIcode\fP, int \fIadjust\fP);
1507    .PP
1508    The \fBpcre_refcount()\fP function is used to maintain a reference count in the
1509    data block that contains a compiled pattern. It is provided for the benefit of
1510    applications that operate in an object-oriented manner, where different parts
1511    of the application may be using the same compiled pattern, but you want to free
1512    the block when they are all done.
1513    .P
1514    When a pattern is compiled, the reference count field is initialized to zero.
1515    It is changed only by calling this function, whose action is to add the
1516    \fIadjust\fP value (which may be positive or negative) to it. The yield of the
1517    function is the new value. However, the value of the count is constrained to
1518    lie between 0 and 65535, inclusive. If the new value is outside these limits,
1519    it is forced to the appropriate limit value.
1520    .P
1521    Except when it is zero, the reference count is not correctly preserved if a
1522    pattern is compiled on one host and then transferred to a host whose byte-order
1523    is different. (This seems a highly unlikely scenario.)
1524    .
1525    .
1526    .SH "MATCHING A PATTERN: THE TRADITIONAL FUNCTION"
1527    .rs
1528    .sp
1529    .B int pcre_exec(const pcre *\fIcode\fP, "const pcre_extra *\fIextra\fP,"
1530    .ti +5n
1531    .B "const char *\fIsubject\fP," int \fIlength\fP, int \fIstartoffset\fP,
1532    .ti +5n
1533    .B int \fIoptions\fP, int *\fIovector\fP, int \fIovecsize\fP);
1534    .P
1535    The function \fBpcre_exec()\fP is called to match a subject string against a
1536    compiled pattern, which is passed in the \fIcode\fP argument. If the
1537    pattern was studied, the result of the study should be passed in the
1538    \fIextra\fP argument. You can call \fBpcre_exec()\fP with the same \fIcode\fP
1539    and \fIextra\fP arguments as many times as you like, in order to match
1540    different subject strings with the same pattern.
1541    .P
1542    This function is the main matching facility of the library, and it operates in
1543    a Perl-like manner. For specialist use there is also an alternative matching
1544    function, which is described
1545    .\" HTML <a href="#dfamatch">
1546    .\" </a>
1547    below
1548    .\"
1549    in the section about the \fBpcre_dfa_exec()\fP function.
1550    .P
1551    In most applications, the pattern will have been compiled (and optionally
1552    studied) in the same process that calls \fBpcre_exec()\fP. However, it is
1553    possible to save compiled patterns and study data, and then use them later
1554    in different processes, possibly even on different hosts. For a discussion
1555    about this, see the
1556    .\" HREF
1557    \fBpcreprecompile\fP
1558    .\"
1559    documentation.
1560    .P
1561    Here is an example of a simple call to \fBpcre_exec()\fP:
1562    .sp
1563    int rc;    int rc;
1564    int ovector[30];    int ovector[30];
1565    rc = pcre_exec(    rc = pcre_exec(
# Line 659  Here is an example of a simple call to \ Line 1569  Here is an example of a simple call to \
1569      11,             /* the length of the subject string */      11,             /* the length of the subject string */
1570      0,              /* start at offset 0 in the subject */      0,              /* start at offset 0 in the subject */
1571      0,              /* default options */      0,              /* default options */
1572      ovector,        /* vector for substring information */      ovector,        /* vector of integers for substring information */
1573      30);            /* number of elements in the vector */      30);            /* number of elements (NOT size in bytes) */
1574    .
1575  If the \fIextra\fR argument is not NULL, it must point to a \fBpcre_extra\fR  .
1576  data block. The \fBpcre_study()\fR function returns such a block (when it  .\" HTML <a name="extradata"></a>
1577    .SS "Extra data for \fBpcre_exec()\fR"
1578    .rs
1579    .sp
1580    If the \fIextra\fP argument is not NULL, it must point to a \fBpcre_extra\fP
1581    data block. The \fBpcre_study()\fP function returns such a block (when it
1582  doesn't return NULL), but you can also create one for yourself, and pass  doesn't return NULL), but you can also create one for yourself, and pass
1583  additional information in it. The fields in the block are as follows:  additional information in it. The \fBpcre_extra\fP block contains the following
1584    fields (not necessarily in this order):
1585    unsigned long int \fIflags\fR;  .sp
1586    void *\fIstudy_data\fR;    unsigned long int \fIflags\fP;
1587    unsigned long int \fImatch_limit\fR;    void *\fIstudy_data\fP;
1588    void *\fIcallout_data\fR;    void *\fIexecutable_jit\fP;
1589      unsigned long int \fImatch_limit\fP;
1590  The \fIflags\fR field is a bitmap that specifies which of the other fields    unsigned long int \fImatch_limit_recursion\fP;
1591  are set. The flag bits are:    void *\fIcallout_data\fP;
1592      const unsigned char *\fItables\fP;
1593    PCRE_EXTRA_STUDY_DATA    unsigned char **\fImark\fP;
1594    PCRE_EXTRA_MATCH_LIMIT  .sp
1595    In the 16-bit version of this structure, the \fImark\fP field has type
1596    "PCRE_UCHAR16 **".
1597    .sp
1598    In the 32-bit version of this structure, the \fImark\fP field has type
1599    "PCRE_UCHAR32 **".
1600    .P
1601    The \fIflags\fP field is used to specify which of the other fields are set. The
1602    flag bits are:
1603    .sp
1604    PCRE_EXTRA_CALLOUT_DATA    PCRE_EXTRA_CALLOUT_DATA
1605      PCRE_EXTRA_EXECUTABLE_JIT
1606  Other flag bits should be set to zero. The \fIstudy_data\fR field is set in the    PCRE_EXTRA_MARK
1607  \fBpcre_extra\fR block that is returned by \fBpcre_study()\fR, together with    PCRE_EXTRA_MATCH_LIMIT
1608  the appropriate flag bit. You should not set this yourself, but you can add to    PCRE_EXTRA_MATCH_LIMIT_RECURSION
1609  the block by setting the other fields.    PCRE_EXTRA_STUDY_DATA
1610      PCRE_EXTRA_TABLES
1611  The \fImatch_limit\fR field provides a means of preventing PCRE from using up a  .sp
1612    Other flag bits should be set to zero. The \fIstudy_data\fP field and sometimes
1613    the \fIexecutable_jit\fP field are set in the \fBpcre_extra\fP block that is
1614    returned by \fBpcre_study()\fP, together with the appropriate flag bits. You
1615    should not set these yourself, but you may add to the block by setting other
1616    fields and their corresponding flag bits.
1617    .P
1618    The \fImatch_limit\fP field provides a means of preventing PCRE from using up a
1619  vast amount of resources when running patterns that are not going to match,  vast amount of resources when running patterns that are not going to match,
1620  but which have a very large number of possibilities in their search trees. The  but which have a very large number of possibilities in their search trees. The
1621  classic example is the use of nested unlimited repeats. Internally, PCRE uses a  classic example is a pattern that uses nested unlimited repeats.
1622  function called \fBmatch()\fR which it calls repeatedly (sometimes  .P
1623  recursively). The limit is imposed on the number of times this function is  Internally, \fBpcre_exec()\fP uses a function called \fBmatch()\fP, which it
1624  called during a match, which has the effect of limiting the amount of recursion  calls repeatedly (sometimes recursively). The limit set by \fImatch_limit\fP is
1625  and backtracking that can take place. For patterns that are not anchored, the  imposed on the number of times this function is called during a match, which
1626  count starts from zero for each position in the subject string.  has the effect of limiting the amount of backtracking that can take place. For
1627    patterns that are not anchored, the count restarts from zero for each position
1628  The default limit for the library can be set when PCRE is built; the default  in the subject string.
1629    .P
1630    When \fBpcre_exec()\fP is called with a pattern that was successfully studied
1631    with a JIT option, the way that the matching is executed is entirely different.
1632    However, there is still the possibility of runaway matching that goes on for a
1633    very long time, and so the \fImatch_limit\fP value is also used in this case
1634    (but in a different way) to limit how long the matching can continue.
1635    .P
1636    The default value for the limit can be set when PCRE is built; the default
1637  default is 10 million, which handles all but the most extreme cases. You can  default is 10 million, which handles all but the most extreme cases. You can
1638  reduce the default by suppling \fBpcre_exec()\fR with a \fRpcre_extra\fR block  override the default by suppling \fBpcre_exec()\fP with a \fBpcre_extra\fP
1639  in which \fImatch_limit\fR is set to a smaller value, and  block in which \fImatch_limit\fP is set, and PCRE_EXTRA_MATCH_LIMIT is set in
1640  PCRE_EXTRA_MATCH_LIMIT is set in the \fIflags\fR field. If the limit is  the \fIflags\fP field. If the limit is exceeded, \fBpcre_exec()\fP returns
1641  exceeded, \fBpcre_exec()\fR returns PCRE_ERROR_MATCHLIMIT.  PCRE_ERROR_MATCHLIMIT.
1642    .P
1643  The \fIpcre_callout\fR field is used in conjunction with the "callout" feature,  The \fImatch_limit_recursion\fP field is similar to \fImatch_limit\fP, but
1644  which is described in the \fBpcrecallout\fR documentation.  instead of limiting the total number of times that \fBmatch()\fP is called, it
1645    limits the depth of recursion. The recursion depth is a smaller number than the
1646  The PCRE_ANCHORED option can be passed in the \fIoptions\fR argument, whose  total number of calls, because not all calls to \fBmatch()\fP are recursive.
1647  unused bits must be zero. This limits \fBpcre_exec()\fR to matching at the  This limit is of use only if it is set smaller than \fImatch_limit\fP.
1648  first matching position. However, if a pattern was compiled with PCRE_ANCHORED,  .P
1649  or turned out to be anchored by virtue of its contents, it cannot be made  Limiting the recursion depth limits the amount of machine stack that can be
1650  unachored at matching time.  used, or, when PCRE has been compiled to use memory on the heap instead of the
1651    stack, the amount of heap memory that can be used. This limit is not relevant,
1652  When PCRE_UTF8 was set at compile time, the validity of the subject as a UTF-8  and is ignored, when matching is done using JIT compiled code.
1653  string is automatically checked. If an invalid UTF-8 sequence of bytes is  .P
1654  found, \fBpcre_exec()\fR returns the error PCRE_ERROR_BADUTF8. If you already  The default value for \fImatch_limit_recursion\fP can be set when PCRE is
1655  know that your subject is valid, and you want to skip this check for  built; the default default is the same value as the default for
1656  performance reasons, you can set the PCRE_NO_UTF8_CHECK option when calling  \fImatch_limit\fP. You can override the default by suppling \fBpcre_exec()\fP
1657  \fBpcre_exec()\fR. When this option is set, the effect of passing an invalid  with a \fBpcre_extra\fP block in which \fImatch_limit_recursion\fP is set, and
1658  UTF-8 string as a subject is undefined. It may cause your program to crash.  PCRE_EXTRA_MATCH_LIMIT_RECURSION is set in the \fIflags\fP field. If the limit
1659    is exceeded, \fBpcre_exec()\fP returns PCRE_ERROR_RECURSIONLIMIT.
1660  There are also three further options that can be set only at matching time:  .P
1661    The \fIcallout_data\fP field is used in conjunction with the "callout" feature,
1662    and is described in the
1663    .\" HREF
1664    \fBpcrecallout\fP
1665    .\"
1666    documentation.
1667    .P
1668    The \fItables\fP field is used to pass a character tables pointer to
1669    \fBpcre_exec()\fP; this overrides the value that is stored with the compiled
1670    pattern. A non-NULL value is stored with the compiled pattern only if custom
1671    tables were supplied to \fBpcre_compile()\fP via its \fItableptr\fP argument.
1672    If NULL is passed to \fBpcre_exec()\fP using this mechanism, it forces PCRE's
1673    internal tables to be used. This facility is helpful when re-using patterns
1674    that have been saved after compiling with an external set of tables, because
1675    the external tables might be at a different address when \fBpcre_exec()\fP is
1676    called. See the
1677    .\" HREF
1678    \fBpcreprecompile\fP
1679    .\"
1680    documentation for a discussion of saving compiled patterns for later use.
1681    .P
1682    If PCRE_EXTRA_MARK is set in the \fIflags\fP field, the \fImark\fP field must
1683    be set to point to a suitable variable. If the pattern contains any
1684    backtracking control verbs such as (*MARK:NAME), and the execution ends up with
1685    a name to pass back, a pointer to the name string (zero terminated) is placed
1686    in the variable pointed to by the \fImark\fP field. The names are within the
1687    compiled pattern; if you wish to retain such a name you must copy it before
1688    freeing the memory of a compiled pattern. If there is no name to pass back, the
1689    variable pointed to by the \fImark\fP field is set to NULL. For details of the
1690    backtracking control verbs, see the section entitled
1691    .\" HTML <a href="pcrepattern#backtrackcontrol">
1692    .\" </a>
1693    "Backtracking control"
1694    .\"
1695    in the
1696    .\" HREF
1697    \fBpcrepattern\fP
1698    .\"
1699    documentation.
1700    .
1701    .
1702    .\" HTML <a name="execoptions"></a>
1703    .SS "Option bits for \fBpcre_exec()\fP"
1704    .rs
1705    .sp
1706    The unused bits of the \fIoptions\fP argument for \fBpcre_exec()\fP must be
1707    zero. The only bits that may be set are PCRE_ANCHORED, PCRE_NEWLINE_\fIxxx\fP,
1708    PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY, PCRE_NOTEMPTY_ATSTART,
1709    PCRE_NO_START_OPTIMIZE, PCRE_NO_UTF8_CHECK, PCRE_PARTIAL_HARD, and
1710    PCRE_PARTIAL_SOFT.
1711    .P
1712    If the pattern was successfully studied with one of the just-in-time (JIT)
1713    compile options, the only supported options for JIT execution are
1714    PCRE_NO_UTF8_CHECK, PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY,
1715    PCRE_NOTEMPTY_ATSTART, PCRE_PARTIAL_HARD, and PCRE_PARTIAL_SOFT. If an
1716    unsupported option is used, JIT execution is disabled and the normal
1717    interpretive code in \fBpcre_exec()\fP is run.
1718    .sp
1719      PCRE_ANCHORED
1720    .sp
1721    The PCRE_ANCHORED option limits \fBpcre_exec()\fP to matching at the first
1722    matching position. If a pattern was compiled with PCRE_ANCHORED, or turned out
1723    to be anchored by virtue of its contents, it cannot be made unachored at
1724    matching time.
1725    .sp
1726      PCRE_BSR_ANYCRLF
1727      PCRE_BSR_UNICODE
1728    .sp
1729    These options (which are mutually exclusive) control what the \eR escape
1730    sequence matches. The choice is either to match only CR, LF, or CRLF, or to
1731    match any Unicode newline sequence. These options override the choice that was
1732    made or defaulted when the pattern was compiled.
1733    .sp
1734      PCRE_NEWLINE_CR
1735      PCRE_NEWLINE_LF
1736      PCRE_NEWLINE_CRLF
1737      PCRE_NEWLINE_ANYCRLF
1738      PCRE_NEWLINE_ANY
1739    .sp
1740    These options override the newline definition that was chosen or defaulted when
1741    the pattern was compiled. For details, see the description of
1742    \fBpcre_compile()\fP above. During matching, the newline choice affects the
1743    behaviour of the dot, circumflex, and dollar metacharacters. It may also alter
1744    the way the match position is advanced after a match failure for an unanchored
1745    pattern.
1746    .P
1747    When PCRE_NEWLINE_CRLF, PCRE_NEWLINE_ANYCRLF, or PCRE_NEWLINE_ANY is set, and a
1748    match attempt for an unanchored pattern fails when the current position is at a
1749    CRLF sequence, and the pattern contains no explicit matches for CR or LF
1750    characters, the match position is advanced by two characters instead of one, in
1751    other words, to after the CRLF.
1752    .P
1753    The above rule is a compromise that makes the most common cases work as
1754    expected. For example, if the pattern is .+A (and the PCRE_DOTALL option is not
1755    set), it does not match the string "\er\enA" because, after failing at the
1756    start, it skips both the CR and the LF before retrying. However, the pattern
1757    [\er\en]A does match that string, because it contains an explicit CR or LF
1758    reference, and so advances only by one character after the first failure.
1759    .P
1760    An explicit match for CR of LF is either a literal appearance of one of those
1761    characters, or one of the \er or \en escape sequences. Implicit matches such as
1762    [^X] do not count, nor does \es (which includes CR and LF in the characters
1763    that it matches).
1764    .P
1765    Notwithstanding the above, anomalous effects may still occur when CRLF is a
1766    valid newline sequence and explicit \er or \en escapes appear in the pattern.
1767    .sp
1768    PCRE_NOTBOL    PCRE_NOTBOL
1769    .sp
1770  The first character of the string is not the beginning of a line, so the  This option specifies that first character of the subject string is not the
1771  circumflex metacharacter should not match before it. Setting this without  beginning of a line, so the circumflex metacharacter should not match before
1772  PCRE_MULTILINE (at compile time) causes circumflex never to match.  it. Setting this without PCRE_MULTILINE (at compile time) causes circumflex
1773    never to match. This option affects only the behaviour of the circumflex
1774    metacharacter. It does not affect \eA.
1775    .sp
1776    PCRE_NOTEOL    PCRE_NOTEOL
1777    .sp
1778  The end of the string is not the end of a line, so the dollar metacharacter  This option specifies that the end of the subject string is not the end of a
1779  should not match it nor (except in multiline mode) a newline immediately before  line, so the dollar metacharacter should not match it nor (except in multiline
1780  it. Setting this without PCRE_MULTILINE (at compile time) causes dollar never  mode) a newline immediately before it. Setting this without PCRE_MULTILINE (at
1781  to match.  compile time) causes dollar never to match. This option affects only the
1782    behaviour of the dollar metacharacter. It does not affect \eZ or \ez.
1783    .sp
1784    PCRE_NOTEMPTY    PCRE_NOTEMPTY
1785    .sp
1786  An empty string is not considered to be a valid match if this option is set. If  An empty string is not considered to be a valid match if this option is set. If
1787  there are alternatives in the pattern, they are tried. If all the alternatives  there are alternatives in the pattern, they are tried. If all the alternatives
1788  match the empty string, the entire match fails. For example, if the pattern  match the empty string, the entire match fails. For example, if the pattern
1789    .sp
1790    a?b?    a?b?
1791    .sp
1792  is applied to a string not beginning with "a" or "b", it matches the empty  is applied to a string not beginning with "a" or "b", it matches an empty
1793  string at the start of the subject. With PCRE_NOTEMPTY set, this match is not  string at the start of the subject. With PCRE_NOTEMPTY set, this match is not
1794  valid, so PCRE searches further into the string for occurrences of "a" or "b".  valid, so PCRE searches further into the string for occurrences of "a" or "b".
1795    .sp
1796  Perl has no direct equivalent of PCRE_NOTEMPTY, but it does make a special case    PCRE_NOTEMPTY_ATSTART
1797  of a pattern match of the empty string within its \fBsplit()\fR function, and  .sp
1798  when using the /g modifier. It is possible to emulate Perl's behaviour after  This is like PCRE_NOTEMPTY, except that an empty string match that is not at
1799  matching a null string by first trying the match again at the same offset with  the start of the subject is permitted. If the pattern is anchored, such a match
1800  PCRE_NOTEMPTY set, and then if that fails by advancing the starting offset (see  can occur only if the pattern contains \eK.
1801  below) and trying an ordinary match again.  .P
1802    Perl has no direct equivalent of PCRE_NOTEMPTY or PCRE_NOTEMPTY_ATSTART, but it
1803  The subject string is passed to \fBpcre_exec()\fR as a pointer in  does make a special case of a pattern match of the empty string within its
1804  \fIsubject\fR, a length in \fIlength\fR, and a starting offset in  \fBsplit()\fP function, and when using the /g modifier. It is possible to
1805  \fIstartoffset\fR. Unlike the pattern string, the subject may contain binary  emulate Perl's behaviour after matching a null string by first trying the match
1806  zero bytes. When the starting offset is zero, the search for a match starts at  again at the same offset with PCRE_NOTEMPTY_ATSTART and PCRE_ANCHORED, and then
1807  the beginning of the subject, and this is by far the most common case.  if that fails, by advancing the starting offset (see below) and trying an
1808    ordinary match again. There is some code that demonstrates how to do this in
1809  If the pattern was compiled with the PCRE_UTF8 option, the subject must be a  the
1810  sequence of bytes that is a valid UTF-8 string. If an invalid UTF-8 string is  .\" HREF
1811  passed, PCRE's behaviour is not defined.  \fBpcredemo\fP
1812    .\"
1813    sample program. In the most general case, you have to check to see if the
1814    newline convention recognizes CRLF as a newline, and if so, and the current
1815    character is CR followed by LF, advance the starting offset by two characters
1816    instead of one.
1817    .sp
1818      PCRE_NO_START_OPTIMIZE
1819    .sp
1820    There are a number of optimizations that \fBpcre_exec()\fP uses at the start of
1821    a match, in order to speed up the process. For example, if it is known that an
1822    unanchored match must start with a specific character, it searches the subject
1823    for that character, and fails immediately if it cannot find it, without
1824    actually running the main matching function. This means that a special item
1825    such as (*COMMIT) at the start of a pattern is not considered until after a
1826    suitable starting point for the match has been found. When callouts or (*MARK)
1827    items are in use, these "start-up" optimizations can cause them to be skipped
1828    if the pattern is never actually used. The start-up optimizations are in effect
1829    a pre-scan of the subject that takes place before the pattern is run.
1830    .P
1831    The PCRE_NO_START_OPTIMIZE option disables the start-up optimizations, possibly
1832    causing performance to suffer, but ensuring that in cases where the result is
1833    "no match", the callouts do occur, and that items such as (*COMMIT) and (*MARK)
1834    are considered at every possible starting position in the subject string. If
1835    PCRE_NO_START_OPTIMIZE is set at compile time, it cannot be unset at matching
1836    time. The use of PCRE_NO_START_OPTIMIZE disables JIT execution; when it is set,
1837    matching is always done using interpretively.
1838    .P
1839    Setting PCRE_NO_START_OPTIMIZE can change the outcome of a matching operation.
1840    Consider the pattern
1841    .sp
1842      (*COMMIT)ABC
1843    .sp
1844    When this is compiled, PCRE records the fact that a match must start with the
1845    character "A". Suppose the subject string is "DEFABC". The start-up
1846    optimization scans along the subject, finds "A" and runs the first match
1847    attempt from there. The (*COMMIT) item means that the pattern must match the
1848    current starting position, which in this case, it does. However, if the same
1849    match is run with PCRE_NO_START_OPTIMIZE set, the initial scan along the
1850    subject string does not happen. The first match attempt is run starting from
1851    "D" and when this fails, (*COMMIT) prevents any further matches being tried, so
1852    the overall result is "no match". If the pattern is studied, more start-up
1853    optimizations may be used. For example, a minimum length for the subject may be
1854    recorded. Consider the pattern
1855    .sp
1856      (*MARK:A)(X|Y)
1857    .sp
1858    The minimum length for a match is one character. If the subject is "ABC", there
1859    will be attempts to match "ABC", "BC", "C", and then finally an empty string.
1860    If the pattern is studied, the final attempt does not take place, because PCRE
1861    knows that the subject is too short, and so the (*MARK) is never encountered.
1862    In this case, studying the pattern does not affect the overall match result,
1863    which is still "no match", but it does affect the auxiliary information that is
1864    returned.
1865    .sp
1866      PCRE_NO_UTF8_CHECK
1867    .sp
1868    When PCRE_UTF8 is set at compile time, the validity of the subject as a UTF-8
1869    string is automatically checked when \fBpcre_exec()\fP is subsequently called.
1870    The entire string is checked before any other processing takes place. The value
1871    of \fIstartoffset\fP is also checked to ensure that it points to the start of a
1872    UTF-8 character. There is a discussion about the
1873    .\" HTML <a href="pcreunicode.html#utf8strings">
1874    .\" </a>
1875    validity of UTF-8 strings
1876    .\"
1877    in the
1878    .\" HREF
1879    \fBpcreunicode\fP
1880    .\"
1881    page. If an invalid sequence of bytes is found, \fBpcre_exec()\fP returns the
1882    error PCRE_ERROR_BADUTF8 or, if PCRE_PARTIAL_HARD is set and the problem is a
1883    truncated character at the end of the subject, PCRE_ERROR_SHORTUTF8. In both
1884    cases, information about the precise nature of the error may also be returned
1885    (see the descriptions of these errors in the section entitled \fIError return
1886    values from\fP \fBpcre_exec()\fP
1887    .\" HTML <a href="#errorlist">
1888    .\" </a>
1889    below).
1890    .\"
1891    If \fIstartoffset\fP contains a value that does not point to the start of a
1892    UTF-8 character (or to the end of the subject), PCRE_ERROR_BADUTF8_OFFSET is
1893    returned.
1894    .P
1895    If you already know that your subject is valid, and you want to skip these
1896    checks for performance reasons, you can set the PCRE_NO_UTF8_CHECK option when
1897    calling \fBpcre_exec()\fP. You might want to do this for the second and
1898    subsequent calls to \fBpcre_exec()\fP if you are making repeated calls to find
1899    all the matches in a single subject string. However, you should be sure that
1900    the value of \fIstartoffset\fP points to the start of a character (or the end
1901    of the subject). When PCRE_NO_UTF8_CHECK is set, the effect of passing an
1902    invalid string as a subject or an invalid value of \fIstartoffset\fP is
1903    undefined. Your program may crash.
1904    .sp
1905      PCRE_PARTIAL_HARD
1906      PCRE_PARTIAL_SOFT
1907    .sp
1908    These options turn on the partial matching feature. For backwards
1909    compatibility, PCRE_PARTIAL is a synonym for PCRE_PARTIAL_SOFT. A partial match
1910    occurs if the end of the subject string is reached successfully, but there are
1911    not enough subject characters to complete the match. If this happens when
1912    PCRE_PARTIAL_SOFT (but not PCRE_PARTIAL_HARD) is set, matching continues by
1913    testing any remaining alternatives. Only if no complete match can be found is
1914    PCRE_ERROR_PARTIAL returned instead of PCRE_ERROR_NOMATCH. In other words,
1915    PCRE_PARTIAL_SOFT says that the caller is prepared to handle a partial match,
1916    but only if no complete match can be found.
1917    .P
1918    If PCRE_PARTIAL_HARD is set, it overrides PCRE_PARTIAL_SOFT. In this case, if a
1919    partial match is found, \fBpcre_exec()\fP immediately returns
1920    PCRE_ERROR_PARTIAL, without considering any other alternatives. In other words,
1921    when PCRE_PARTIAL_HARD is set, a partial match is considered to be more
1922    important that an alternative complete match.
1923    .P
1924    In both cases, the portion of the string that was inspected when the partial
1925    match was found is set as the first matching string. There is a more detailed
1926    discussion of partial and multi-segment matching, with examples, in the
1927    .\" HREF
1928    \fBpcrepartial\fP
1929    .\"
1930    documentation.
1931    .
1932    .
1933    .SS "The string to be matched by \fBpcre_exec()\fP"
1934    .rs
1935    .sp
1936    The subject string is passed to \fBpcre_exec()\fP as a pointer in
1937    \fIsubject\fP, a length in bytes in \fIlength\fP, and a starting byte offset
1938    in \fIstartoffset\fP. If this is negative or greater than the length of the
1939    subject, \fBpcre_exec()\fP returns PCRE_ERROR_BADOFFSET. When the starting
1940    offset is zero, the search for a match starts at the beginning of the subject,
1941    and this is by far the most common case. In UTF-8 mode, the byte offset must
1942    point to the start of a UTF-8 character (or the end of the subject). Unlike the
1943    pattern string, the subject may contain binary zero bytes.
1944    .P
1945  A non-zero starting offset is useful when searching for another match in the  A non-zero starting offset is useful when searching for another match in the
1946  same subject by calling \fBpcre_exec()\fR again after a previous success.  same subject by calling \fBpcre_exec()\fP again after a previous success.
1947  Setting \fIstartoffset\fR differs from just passing over a shortened string and  Setting \fIstartoffset\fP differs from just passing over a shortened string and
1948  setting PCRE_NOTBOL in the case of a pattern that begins with any kind of  setting PCRE_NOTBOL in the case of a pattern that begins with any kind of
1949  lookbehind. For example, consider the pattern  lookbehind. For example, consider the pattern
1950    .sp
1951    \\Biss\\B    \eBiss\eB
1952    .sp
1953  which finds occurrences of "iss" in the middle of words. (\\B matches only if  which finds occurrences of "iss" in the middle of words. (\eB matches only if
1954  the current position in the subject is not a word boundary.) When applied to  the current position in the subject is not a word boundary.) When applied to
1955  the string "Mississipi" the first call to \fBpcre_exec()\fR finds the first  the string "Mississipi" the first call to \fBpcre_exec()\fP finds the first
1956  occurrence. If \fBpcre_exec()\fR is called again with just the remainder of the  occurrence. If \fBpcre_exec()\fP is called again with just the remainder of the
1957  subject, namely "issipi", it does not match, because \\B is always false at the  subject, namely "issipi", it does not match, because \eB is always false at the
1958  start of the subject, which is deemed to be a word boundary. However, if  start of the subject, which is deemed to be a word boundary. However, if
1959  \fBpcre_exec()\fR is passed the entire string again, but with \fIstartoffset\fR  \fBpcre_exec()\fP is passed the entire string again, but with \fIstartoffset\fP
1960  set to 4, it finds the second occurrence of "iss" because it is able to look  set to 4, it finds the second occurrence of "iss" because it is able to look
1961  behind the starting point to discover that it is preceded by a letter.  behind the starting point to discover that it is preceded by a letter.
1962    .P
1963    Finding all the matches in a subject is tricky when the pattern can match an
1964    empty string. It is possible to emulate Perl's /g behaviour by first trying the
1965    match again at the same offset, with the PCRE_NOTEMPTY_ATSTART and
1966    PCRE_ANCHORED options, and then if that fails, advancing the starting offset
1967    and trying an ordinary match again. There is some code that demonstrates how to
1968    do this in the
1969    .\" HREF
1970    \fBpcredemo\fP
1971    .\"
1972    sample program. In the most general case, you have to check to see if the
1973    newline convention recognizes CRLF as a newline, and if so, and the current
1974    character is CR followed by LF, advance the starting offset by two characters
1975    instead of one.
1976    .P
1977  If a non-zero starting offset is passed when the pattern is anchored, one  If a non-zero starting offset is passed when the pattern is anchored, one
1978  attempt to match at the given offset is tried. This can only succeed if the  attempt to match at the given offset is made. This can only succeed if the
1979  pattern does not require the match to be at the start of the subject.  pattern does not require the match to be at the start of the subject.
1980    .
1981    .
1982    .SS "How \fBpcre_exec()\fP returns captured substrings"
1983    .rs
1984    .sp
1985  In general, a pattern matches a certain portion of the subject, and in  In general, a pattern matches a certain portion of the subject, and in
1986  addition, further substrings from the subject may be picked out by parts of the  addition, further substrings from the subject may be picked out by parts of the
1987  pattern. Following the usage in Jeffrey Friedl's book, this is called  pattern. Following the usage in Jeffrey Friedl's book, this is called
1988  "capturing" in what follows, and the phrase "capturing subpattern" is used for  "capturing" in what follows, and the phrase "capturing subpattern" is used for
1989  a fragment of a pattern that picks out a substring. PCRE supports several other  a fragment of a pattern that picks out a substring. PCRE supports several other
1990  kinds of parenthesized subpattern that do not cause substrings to be captured.  kinds of parenthesized subpattern that do not cause substrings to be captured.
1991    .P
1992  Captured substrings are returned to the caller via a vector of integer offsets  Captured substrings are returned to the caller via a vector of integers whose
1993  whose address is passed in \fIovector\fR. The number of elements in the vector  address is passed in \fIovector\fP. The number of elements in the vector is
1994  is passed in \fIovecsize\fR. The first two-thirds of the vector is used to pass  passed in \fIovecsize\fP, which must be a non-negative number. \fBNote\fP: this
1995  back captured substrings, each substring using a pair of integers. The  argument is NOT the size of \fIovector\fP in bytes.
1996  remaining third of the vector is used as workspace by \fBpcre_exec()\fR while  .P
1997  matching capturing subpatterns, and is not available for passing back  The first two-thirds of the vector is used to pass back captured substrings,
1998  information. The length passed in \fIovecsize\fR should always be a multiple of  each substring using a pair of integers. The remaining third of the vector is
1999  three. If it is not, it is rounded down.  used as workspace by \fBpcre_exec()\fP while matching capturing subpatterns,
2000    and is not available for passing back information. The number passed in
2001  When a match has been successful, information about captured substrings is  \fIovecsize\fP should always be a multiple of three. If it is not, it is
2002  returned in pairs of integers, starting at the beginning of \fIovector\fR, and  rounded down.
2003  continuing up to two-thirds of its length at the most. The first element of a  .P
2004  pair is set to the offset of the first character in a substring, and the second  When a match is successful, information about captured substrings is returned
2005  is set to the offset of the first character after the end of a substring. The  in pairs of integers, starting at the beginning of \fIovector\fP, and
2006  first pair, \fIovector[0]\fR and \fIovector[1]\fR, identify the portion of the  continuing up to two-thirds of its length at the most. The first element of
2007  subject string matched by the entire pattern. The next pair is used for the  each pair is set to the byte offset of the first character in a substring, and
2008  first capturing subpattern, and so on. The value returned by \fBpcre_exec()\fR  the second is set to the byte offset of the first character after the end of a
2009  is the number of pairs that have been set. If there are no capturing  substring. \fBNote\fP: these values are always byte offsets, even in UTF-8
2010  subpatterns, the return value from a successful match is 1, indicating that  mode. They are not character counts.
2011  just the first pair of offsets has been set.  .P
2012    The first pair of integers, \fIovector[0]\fP and \fIovector[1]\fP, identify the
2013  Some convenience functions are provided for extracting the captured substrings  portion of the subject string matched by the entire pattern. The next pair is
2014  as separate strings. These are described in the following section.  used for the first capturing subpattern, and so on. The value returned by
2015    \fBpcre_exec()\fP is one more than the highest numbered pair that has been set.
2016  It is possible for an capturing subpattern number \fIn+1\fR to match some  For example, if two substrings have been captured, the returned value is 3. If
2017  part of the subject when subpattern \fIn\fR has not been used at all. For  there are no capturing subpatterns, the return value from a successful match is
2018  example, if the string "abc" is matched against the pattern (a|(z))(bc)  1, indicating that just the first pair of offsets has been set.
2019  subpatterns 1 and 3 are matched, but 2 is not. When this happens, both offset  .P
 values corresponding to the unused subpattern are set to -1.  
   
2020  If a capturing subpattern is matched repeatedly, it is the last portion of the  If a capturing subpattern is matched repeatedly, it is the last portion of the
2021  string that it matched that gets returned.  string that it matched that is returned.
2022    .P
2023  If the vector is too small to hold all the captured substrings, it is used as  If the vector is too small to hold all the captured substring offsets, it is
2024  far as possible (up to two-thirds of its length), and the function returns a  used as far as possible (up to two-thirds of its length), and the function
2025  value of zero. In particular, if the substring offsets are not of interest,  returns a value of zero. If neither the actual string matched nor any captured
2026  \fBpcre_exec()\fR may be called with \fIovector\fR passed as NULL and  substrings are of interest, \fBpcre_exec()\fP may be called with \fIovector\fP
2027  \fIovecsize\fR as zero. However, if the pattern contains back references and  passed as NULL and \fIovecsize\fP as zero. However, if the pattern contains
2028  the \fIovector\fR isn't big enough to remember the related substrings, PCRE has  back references and the \fIovector\fP is not big enough to remember the related
2029  to get additional memory for use during matching. Thus it is usually advisable  substrings, PCRE has to get additional memory for use during matching. Thus it
2030  to supply an \fIovector\fR.  is usually advisable to supply an \fIovector\fP of reasonable size.
2031    .P
2032  Note that \fBpcre_info()\fR can be used to find out how many capturing  There are some cases where zero is returned (indicating vector overflow) when
2033    in fact the vector is exactly the right size for the final match. For example,
2034    consider the pattern
2035    .sp
2036      (a)(?:(b)c|bd)
2037    .sp
2038    If a vector of 6 elements (allowing for only 1 captured substring) is given
2039    with subject string "abd", \fBpcre_exec()\fP will try to set the second
2040    captured string, thereby recording a vector overflow, before failing to match
2041    "c" and backing up to try the second alternative. The zero return, however,
2042    does correctly indicate that the maximum number of slots (namely 2) have been
2043    filled. In similar cases where there is temporary overflow, but the final
2044    number of used slots is actually less than the maximum, a non-zero value is
2045    returned.
2046    .P
2047    The \fBpcre_fullinfo()\fP function can be used to find out how many capturing
2048  subpatterns there are in a compiled pattern. The smallest size for  subpatterns there are in a compiled pattern. The smallest size for
2049  \fIovector\fR that will allow for \fIn\fR captured substrings, in addition to  \fIovector\fP that will allow for \fIn\fP captured substrings, in addition to
2050  the offsets of the substring matched by the whole pattern, is (\fIn\fR+1)*3.  the offsets of the substring matched by the whole pattern, is (\fIn\fP+1)*3.
2051    .P
2052  If \fBpcre_exec()\fR fails, it returns a negative number. The following are  It is possible for capturing subpattern number \fIn+1\fP to match some part of
2053    the subject when subpattern \fIn\fP has not been used at all. For example, if
2054    the string "abc" is matched against the pattern (a|(z))(bc) the return from the
2055    function is 4, and subpatterns 1 and 3 are matched, but 2 is not. When this
2056    happens, both values in the offset pairs corresponding to unused subpatterns
2057    are set to -1.
2058    .P
2059    Offset values that correspond to unused subpatterns at the end of the
2060    expression are also set to -1. For example, if the string "abc" is matched
2061    against the pattern (abc)(x(yz)?)? subpatterns 2 and 3 are not matched. The
2062    return from the function is 2, because the highest used capturing subpattern
2063    number is 1, and the offsets for for the second and third capturing subpatterns
2064    (assuming the vector is large enough, of course) are set to -1.
2065    .P
2066    \fBNote\fP: Elements in the first two-thirds of \fIovector\fP that do not
2067    correspond to capturing parentheses in the pattern are never changed. That is,
2068    if a pattern contains \fIn\fP capturing parentheses, no more than
2069    \fIovector[0]\fP to \fIovector[2n+1]\fP are set by \fBpcre_exec()\fP. The other
2070    elements (in the first two-thirds) retain whatever values they previously had.
2071    .P
2072    Some convenience functions are provided for extracting the captured substrings
2073    as separate strings. These are described below.
2074    .
2075    .
2076    .\" HTML <a name="errorlist"></a>
2077    .SS "Error return values from \fBpcre_exec()\fP"
2078    .rs
2079    .sp
2080    If \fBpcre_exec()\fP fails, it returns a negative number. The following are
2081  defined in the header file:  defined in the header file:
2082    .sp
2083    PCRE_ERROR_NOMATCH        (-1)    PCRE_ERROR_NOMATCH        (-1)
2084    .sp
2085  The subject string did not match the pattern.  The subject string did not match the pattern.
2086    .sp
2087    PCRE_ERROR_NULL           (-2)    PCRE_ERROR_NULL           (-2)
2088    .sp
2089  Either \fIcode\fR or \fIsubject\fR was passed as NULL, or \fIovector\fR was  Either \fIcode\fP or \fIsubject\fP was passed as NULL, or \fIovector\fP was
2090  NULL and \fIovecsize\fR was not zero.  NULL and \fIovecsize\fP was not zero.
2091    .sp
2092    PCRE_ERROR_BADOPTION      (-3)    PCRE_ERROR_BADOPTION      (-3)
2093    .sp
2094  An unrecognized bit was set in the \fIoptions\fR argument.  An unrecognized bit was set in the \fIoptions\fP argument.
2095    .sp
2096    PCRE_ERROR_BADMAGIC       (-4)    PCRE_ERROR_BADMAGIC       (-4)
2097    .sp
2098  PCRE stores a 4-byte "magic number" at the start of the compiled code, to catch  PCRE stores a 4-byte "magic number" at the start of the compiled code, to catch
2099  the case when it is passed a junk pointer. This is the error it gives when the  the case when it is passed a junk pointer and to detect when a pattern that was
2100  magic number isn't present.  compiled in an environment of one endianness is run in an environment with the
2101    other endianness. This is the error that PCRE gives when the magic number is
2102    PCRE_ERROR_UNKNOWN_NODE   (-5)  not present.
2103    .sp
2104      PCRE_ERROR_UNKNOWN_OPCODE (-5)
2105    .sp
2106  While running the pattern match, an unknown item was encountered in the  While running the pattern match, an unknown item was encountered in the
2107  compiled pattern. This error could be caused by a bug in PCRE or by overwriting  compiled pattern. This error could be caused by a bug in PCRE or by overwriting
2108  of the compiled pattern.  of the compiled pattern.
2109    .sp
2110    PCRE_ERROR_NOMEMORY       (-6)    PCRE_ERROR_NOMEMORY       (-6)
2111    .sp
2112  If a pattern contains back references, but the \fIovector\fR that is passed to  If a pattern contains back references, but the \fIovector\fP that is passed to
2113  \fBpcre_exec()\fR is not big enough to remember the referenced substrings, PCRE  \fBpcre_exec()\fP is not big enough to remember the referenced substrings, PCRE
2114  gets a block of memory at the start of matching to use for this purpose. If the  gets a block of memory at the start of matching to use for this purpose. If the
2115  call via \fBpcre_malloc()\fR fails, this error is given. The memory is freed at  call via \fBpcre_malloc()\fP fails, this error is given. The memory is
2116  the end of matching.  automatically freed at the end of matching.
2117    .P
2118    This error is also given if \fBpcre_stack_malloc()\fP fails in
2119    \fBpcre_exec()\fP. This can happen only when PCRE has been compiled with
2120    \fB--disable-stack-for-recursion\fP.
2121    .sp
2122    PCRE_ERROR_NOSUBSTRING    (-7)    PCRE_ERROR_NOSUBSTRING    (-7)
2123    .sp
2124  This error is used by the \fBpcre_copy_substring()\fR,  This error is used by the \fBpcre_copy_substring()\fP,
2125  \fBpcre_get_substring()\fR, and \fBpcre_get_substring_list()\fR functions (see  \fBpcre_get_substring()\fP, and \fBpcre_get_substring_list()\fP functions (see
2126  below). It is never returned by \fBpcre_exec()\fR.  below). It is never returned by \fBpcre_exec()\fP.
2127    .sp
2128    PCRE_ERROR_MATCHLIMIT     (-8)    PCRE_ERROR_MATCHLIMIT     (-8)
2129    .sp
2130  The recursion and backtracking limit, as specified by the \fImatch_limit\fR  The backtracking limit, as specified by the \fImatch_limit\fP field in a
2131  field in a \fBpcre_extra\fR structure (or defaulted) was reached. See the  \fBpcre_extra\fP structure (or defaulted) was reached. See the description
2132  description above.  above.
2133    .sp
2134    PCRE_ERROR_CALLOUT        (-9)    PCRE_ERROR_CALLOUT        (-9)
2135    .sp
2136  This error is never generated by \fBpcre_exec()\fR itself. It is provided for  This error is never generated by \fBpcre_exec()\fP itself. It is provided for
2137  use by callout functions that want to yield a distinctive error code. See the  use by callout functions that want to yield a distinctive error code. See the
2138  \fBpcrecallout\fR documentation for details.  .\" HREF
2139    \fBpcrecallout\fP
2140    PCRE_ERROR_BADUTF8       (-10)  .\"
2141    documentation for details.
2142  A string that contains an invalid UTF-8 byte sequence was passed as a subject.  .sp
2143      PCRE_ERROR_BADUTF8        (-10)
2144  .SH EXTRACTING CAPTURED SUBSTRINGS BY NUMBER  .sp
2145    A string that contains an invalid UTF-8 byte sequence was passed as a subject,
2146    and the PCRE_NO_UTF8_CHECK option was not set. If the size of the output vector
2147    (\fIovecsize\fP) is at least 2, the byte offset to the start of the the invalid
2148    UTF-8 character is placed in the first element, and a reason code is placed in
2149    the second element. The reason codes are listed in the
2150    .\" HTML <a href="#badutf8reasons">
2151    .\" </a>
2152    following section.
2153    .\"
2154    For backward compatibility, if PCRE_PARTIAL_HARD is set and the problem is a
2155    truncated UTF-8 character at the end of the subject (reason codes 1 to 5),
2156    PCRE_ERROR_SHORTUTF8 is returned instead of PCRE_ERROR_BADUTF8.
2157    .sp
2158      PCRE_ERROR_BADUTF8_OFFSET (-11)
2159    .sp
2160    The UTF-8 byte sequence that was passed as a subject was checked and found to
2161    be valid (the PCRE_NO_UTF8_CHECK option was not set), but the value of
2162    \fIstartoffset\fP did not point to the beginning of a UTF-8 character or the
2163    end of the subject.
2164    .sp
2165      PCRE_ERROR_PARTIAL        (-12)
2166    .sp
2167    The subject string did not match, but it did match partially. See the
2168    .\" HREF
2169    \fBpcrepartial\fP
2170    .\"
2171    documentation for details of partial matching.
2172    .sp
2173      PCRE_ERROR_BADPARTIAL     (-13)
2174    .sp
2175    This code is no longer in use. It was formerly returned when the PCRE_PARTIAL
2176    option was used with a compiled pattern containing items that were not
2177    supported for partial matching. From release 8.00 onwards, there are no
2178    restrictions on partial matching.
2179    .sp
2180      PCRE_ERROR_INTERNAL       (-14)
2181    .sp
2182    An unexpected internal error has occurred. This error could be caused by a bug
2183    in PCRE or by overwriting of the compiled pattern.
2184    .sp
2185      PCRE_ERROR_BADCOUNT       (-15)
2186    .sp
2187    This error is given if the value of the \fIovecsize\fP argument is negative.
2188    .sp
2189      PCRE_ERROR_RECURSIONLIMIT (-21)
2190    .sp
2191    The internal recursion limit, as specified by the \fImatch_limit_recursion\fP
2192    field in a \fBpcre_extra\fP structure (or defaulted) was reached. See the
2193    description above.
2194    .sp
2195      PCRE_ERROR_BADNEWLINE     (-23)
2196    .sp
2197    An invalid combination of PCRE_NEWLINE_\fIxxx\fP options was given.
2198    .sp
2199      PCRE_ERROR_BADOFFSET      (-24)
2200    .sp
2201    The value of \fIstartoffset\fP was negative or greater than the length of the
2202    subject, that is, the value in \fIlength\fP.
2203    .sp
2204      PCRE_ERROR_SHORTUTF8      (-25)
2205    .sp
2206    This error is returned instead of PCRE_ERROR_BADUTF8 when the subject string
2207    ends with a truncated UTF-8 character and the PCRE_PARTIAL_HARD option is set.
2208    Information about the failure is returned as for PCRE_ERROR_BADUTF8. It is in
2209    fact sufficient to detect this case, but this special error code for
2210    PCRE_PARTIAL_HARD precedes the implementation of returned information; it is
2211    retained for backwards compatibility.
2212    .sp
2213      PCRE_ERROR_RECURSELOOP    (-26)
2214    .sp
2215    This error is returned when \fBpcre_exec()\fP detects a recursion loop within
2216    the pattern. Specifically, it means that either the whole pattern or a
2217    subpattern has been called recursively for the second time at the same position
2218    in the subject string. Some simple patterns that might do this are detected and
2219    faulted at compile time, but more complicated cases, in particular mutual
2220    recursions between two different subpatterns, cannot be detected until run
2221    time.
2222    .sp
2223      PCRE_ERROR_JIT_STACKLIMIT (-27)
2224    .sp
2225    This error is returned when a pattern that was successfully studied using a
2226    JIT compile option is being matched, but the memory available for the
2227    just-in-time processing stack is not large enough. See the
2228    .\" HREF
2229    \fBpcrejit\fP
2230    .\"
2231    documentation for more details.
2232    .sp
2233      PCRE_ERROR_BADMODE        (-28)
2234    .sp
2235    This error is given if a pattern that was compiled by the 8-bit library is
2236    passed to a 16-bit or 32-bit library function, or vice versa.
2237    .sp
2238      PCRE_ERROR_BADENDIANNESS  (-29)
2239    .sp
2240    This error is given if a pattern that was compiled and saved is reloaded on a
2241    host with different endianness. The utility function
2242    \fBpcre_pattern_to_host_byte_order()\fP can be used to convert such a pattern
2243    so that it runs on the new host.
2244    .P
2245    Error numbers -16 to -20, -22, and -30 are not used by \fBpcre_exec()\fP.
2246    .
2247    .
2248    .\" HTML <a name="badutf8reasons"></a>
2249    .SS "Reason codes for invalid UTF-8 strings"
2250  .rs  .rs
2251  .sp  .sp
2252  .B int pcre_copy_substring(const char *\fIsubject\fR, int *\fIovector\fR,  This section applies only to the 8-bit library. The corresponding information
2253    for the 16-bit library is given in the
2254    .\" HREF
2255    \fBpcre16\fP
2256    .\"
2257    page. The corresponding information for the 32-bit library is given in the
2258    .\" HREF
2259    \fBpcre32\fP
2260    .\"
2261    page.
2262    .P
2263    When \fBpcre_exec()\fP returns either PCRE_ERROR_BADUTF8 or
2264    PCRE_ERROR_SHORTUTF8, and the size of the output vector (\fIovecsize\fP) is at
2265    least 2, the offset of the start of the invalid UTF-8 character is placed in
2266    the first output vector element (\fIovector[0]\fP) and a reason code is placed
2267    in the second element (\fIovector[1]\fP). The reason codes are given names in
2268    the \fBpcre.h\fP header file:
2269    .sp
2270      PCRE_UTF8_ERR1
2271      PCRE_UTF8_ERR2
2272      PCRE_UTF8_ERR3
2273      PCRE_UTF8_ERR4
2274      PCRE_UTF8_ERR5
2275    .sp
2276    The string ends with a truncated UTF-8 character; the code specifies how many
2277    bytes are missing (1 to 5). Although RFC 3629 restricts UTF-8 characters to be
2278    no longer than 4 bytes, the encoding scheme (originally defined by RFC 2279)
2279    allows for up to 6 bytes, and this is checked first; hence the possibility of
2280    4 or 5 missing bytes.
2281    .sp
2282      PCRE_UTF8_ERR6
2283      PCRE_UTF8_ERR7
2284      PCRE_UTF8_ERR8
2285      PCRE_UTF8_ERR9
2286      PCRE_UTF8_ERR10
2287    .sp
2288    The two most significant bits of the 2nd, 3rd, 4th, 5th, or 6th byte of the
2289    character do not have the binary value 0b10 (that is, either the most
2290    significant bit is 0, or the next bit is 1).
2291    .sp
2292      PCRE_UTF8_ERR11
2293      PCRE_UTF8_ERR12
2294    .sp
2295    A character that is valid by the RFC 2279 rules is either 5 or 6 bytes long;
2296    these code points are excluded by RFC 3629.
2297    .sp
2298      PCRE_UTF8_ERR13
2299    .sp
2300    A 4-byte character has a value greater than 0x10fff; these code points are
2301    excluded by RFC 3629.
2302    .sp
2303      PCRE_UTF8_ERR14
2304    .sp
2305    A 3-byte character has a value in the range 0xd800 to 0xdfff; this range of
2306    code points are reserved by RFC 3629 for use with UTF-16, and so are excluded
2307    from UTF-8.
2308    .sp
2309      PCRE_UTF8_ERR15
2310      PCRE_UTF8_ERR16
2311      PCRE_UTF8_ERR17
2312      PCRE_UTF8_ERR18
2313      PCRE_UTF8_ERR19
2314    .sp
2315    A 2-, 3-, 4-, 5-, or 6-byte character is "overlong", that is, it codes for a
2316    value that can be represented by fewer bytes, which is invalid. For example,
2317    the two bytes 0xc0, 0xae give the value 0x2e, whose correct coding uses just
2318    one byte.
2319    .sp
2320      PCRE_UTF8_ERR20
2321    .sp
2322    The two most significant bits of the first byte of a character have the binary
2323    value 0b10 (that is, the most significant bit is 1 and the second is 0). Such a
2324    byte can only validly occur as the second or subsequent byte of a multi-byte
2325    character.
2326    .sp
2327      PCRE_UTF8_ERR21
2328    .sp
2329    The first byte of a character has the value 0xfe or 0xff. These values can
2330    never occur in a valid UTF-8 string.
2331    .sp
2332      PCRE_UTF8_ERR2
2333    .sp
2334    Non-character. These are the last two characters in each plane (0xfffe, 0xffff,
2335    0x1fffe, 0x1ffff .. 0x10fffe, 0x10ffff), and the characters 0xfdd0..0xfdef.
2336    .
2337    .
2338    .SH "EXTRACTING CAPTURED SUBSTRINGS BY NUMBER"
2339    .rs
2340    .sp
2341    .B int pcre_copy_substring(const char *\fIsubject\fP, int *\fIovector\fP,
2342  .ti +5n  .ti +5n
2343  .B int \fIstringcount\fR, int \fIstringnumber\fR, char *\fIbuffer\fR,  .B int \fIstringcount\fP, int \fIstringnumber\fP, char *\fIbuffer\fP,
2344  .ti +5n  .ti +5n
2345  .B int \fIbuffersize\fR);  .B int \fIbuffersize\fP);
2346  .PP  .PP
2347  .br  .B int pcre_get_substring(const char *\fIsubject\fP, int *\fIovector\fP,
 .B int pcre_get_substring(const char *\fIsubject\fR, int *\fIovector\fR,  
2348  .ti +5n  .ti +5n
2349  .B int \fIstringcount\fR, int \fIstringnumber\fR,  .B int \fIstringcount\fP, int \fIstringnumber\fP,
2350  .ti +5n  .ti +5n
2351  .B const char **\fIstringptr\fR);  .B const char **\fIstringptr\fP);
2352  .PP  .PP
2353  .br  .B int pcre_get_substring_list(const char *\fIsubject\fP,
 .B int pcre_get_substring_list(const char *\fIsubject\fR,  
2354  .ti +5n  .ti +5n
2355  .B int *\fIovector\fR, int \fIstringcount\fR, "const char ***\fIlistptr\fR);"  .B int *\fIovector\fP, int \fIstringcount\fP, "const char ***\fIlistptr\fP);"
2356  .PP  .PP
2357  Captured substrings can be accessed directly by using the offsets returned by  Captured substrings can be accessed directly by using the offsets returned by
2358  \fBpcre_exec()\fR in \fIovector\fR. For convenience, the functions  \fBpcre_exec()\fP in \fIovector\fP. For convenience, the functions
2359  \fBpcre_copy_substring()\fR, \fBpcre_get_substring()\fR, and  \fBpcre_copy_substring()\fP, \fBpcre_get_substring()\fP, and
2360  \fBpcre_get_substring_list()\fR are provided for extracting captured substrings  \fBpcre_get_substring_list()\fP are provided for extracting captured substrings
2361  as new, separate, zero-terminated strings. These functions identify substrings  as new, separate, zero-terminated strings. These functions identify substrings
2362  by number. The next section describes functions for extracting named  by number. The next section describes functions for extracting named
2363  substrings. A substring that contains a binary zero is correctly extracted and  substrings.
2364  has a further zero added on the end, but the result is not, of course,  .P
2365  a C string.  A substring that contains a binary zero is correctly extracted and has a
2366    further zero added on the end, but the result is not, of course, a C string.
2367    However, you can process such a string by referring to the length that is
2368    returned by \fBpcre_copy_substring()\fP and \fBpcre_get_substring()\fP.
2369    Unfortunately, the interface to \fBpcre_get_substring_list()\fP is not adequate
2370    for handling strings containing binary zeros, because the end of the final
2371    string is not independently indicated.
2372    .P
2373  The first three arguments are the same for all three of these functions:  The first three arguments are the same for all three of these functions:
2374  \fIsubject\fR is the subject string which has just been successfully matched,  \fIsubject\fP is the subject string that has just been successfully matched,
2375  \fIovector\fR is a pointer to the vector of integer offsets that was passed to  \fIovector\fP is a pointer to the vector of integer offsets that was passed to
2376  \fBpcre_exec()\fR, and \fIstringcount\fR is the number of substrings that were  \fBpcre_exec()\fP, and \fIstringcount\fP is the number of substrings that were
2377  captured by the match, including the substring that matched the entire regular  captured by the match, including the substring that matched the entire regular
2378  expression. This is the value returned by \fBpcre_exec\fR if it is greater than  expression. This is the value returned by \fBpcre_exec()\fP if it is greater
2379  zero. If \fBpcre_exec()\fR returned zero, indicating that it ran out of space  than zero. If \fBpcre_exec()\fP returned zero, indicating that it ran out of
2380  in \fIovector\fR, the value passed as \fIstringcount\fR should be the size of  space in \fIovector\fP, the value passed as \fIstringcount\fP should be the
2381  the vector divided by three.  number of elements in the vector divided by three.
2382    .P
2383  The functions \fBpcre_copy_substring()\fR and \fBpcre_get_substring()\fR  The functions \fBpcre_copy_substring()\fP and \fBpcre_get_substring()\fP
2384  extract a single substring, whose number is given as \fIstringnumber\fR. A  extract a single substring, whose number is given as \fIstringnumber\fP. A
2385  value of zero extracts the substring that matched the entire pattern, while  value of zero extracts the substring that matched the entire pattern, whereas
2386  higher values extract the captured substrings. For \fBpcre_copy_substring()\fR,  higher values extract the captured substrings. For \fBpcre_copy_substring()\fP,
2387  the string is placed in \fIbuffer\fR, whose length is given by  the string is placed in \fIbuffer\fP, whose length is given by
2388  \fIbuffersize\fR, while for \fBpcre_get_substring()\fR a new block of memory is  \fIbuffersize\fP, while for \fBpcre_get_substring()\fP a new block of memory is
2389  obtained via \fBpcre_malloc\fR, and its address is returned via  obtained via \fBpcre_malloc\fP, and its address is returned via
2390  \fIstringptr\fR. The yield of the function is the length of the string, not  \fIstringptr\fP. The yield of the function is the length of the string, not
2391  including the terminating zero, or one of  including the terminating zero, or one of these error codes:
2392    .sp
2393    PCRE_ERROR_NOMEMORY       (-6)    PCRE_ERROR_NOMEMORY       (-6)
2394    .sp
2395  The buffer was too small for \fBpcre_copy_substring()\fR, or the attempt to get  The buffer was too small for \fBpcre_copy_substring()\fP, or the attempt to get
2396  memory failed for \fBpcre_get_substring()\fR.  memory failed for \fBpcre_get_substring()\fP.
2397    .sp
2398    PCRE_ERROR_NOSUBSTRING    (-7)    PCRE_ERROR_NOSUBSTRING    (-7)
2399    .sp
2400  There is no substring whose number is \fIstringnumber\fR.  There is no substring whose number is \fIstringnumber\fP.
2401    .P
2402  The \fBpcre_get_substring_list()\fR function extracts all available substrings  The \fBpcre_get_substring_list()\fP function extracts all available substrings
2403  and builds a list of pointers to them. All this is done in a single block of  and builds a list of pointers to them. All this is done in a single block of
2404  memory which is obtained via \fBpcre_malloc\fR. The address of the memory block  memory that is obtained via \fBpcre_malloc\fP. The address of the memory block
2405  is returned via \fIlistptr\fR, which is also the start of the list of string  is returned via \fIlistptr\fP, which is also the start of the list of string
2406  pointers. The end of the list is marked by a NULL pointer. The yield of the  pointers. The end of the list is marked by a NULL pointer. The yield of the
2407  function is zero if all went well, or  function is zero if all went well, or the error code
2408    .sp
2409    PCRE_ERROR_NOMEMORY       (-6)    PCRE_ERROR_NOMEMORY       (-6)
2410    .sp
2411  if the attempt to get the memory block failed.  if the attempt to get the memory block failed.
2412    .P
2413  When any of these functions encounter a substring that is unset, which can  When any of these functions encounter a substring that is unset, which can
2414  happen when capturing subpattern number \fIn+1\fR matches some part of the  happen when capturing subpattern number \fIn+1\fP matches some part of the
2415  subject, but subpattern \fIn\fR has not been used at all, they return an empty  subject, but subpattern \fIn\fP has not been used at all, they return an empty
2416  string. This can be distinguished from a genuine zero-length substring by  string. This can be distinguished from a genuine zero-length substring by
2417  inspecting the appropriate offset in \fIovector\fR, which is negative for unset  inspecting the appropriate offset in \fIovector\fP, which is negative for unset
2418  substrings.  substrings.
2419    .P
2420  The two convenience functions \fBpcre_free_substring()\fR and  The two convenience functions \fBpcre_free_substring()\fP and
2421  \fBpcre_free_substring_list()\fR can be used to free the memory returned by  \fBpcre_free_substring_list()\fP can be used to free the memory returned by
2422  a previous call of \fBpcre_get_substring()\fR or  a previous call of \fBpcre_get_substring()\fP or
2423  \fBpcre_get_substring_list()\fR, respectively. They do nothing more than call  \fBpcre_get_substring_list()\fP, respectively. They do nothing more than call
2424  the function pointed to by \fBpcre_free\fR, which of course could be called  the function pointed to by \fBpcre_free\fP, which of course could be called
2425  directly from a C program. However, PCRE is used in some situations where it is  directly from a C program. However, PCRE is used in some situations where it is
2426  linked via a special interface to another programming language which cannot use  linked via a special interface to another programming language that cannot use
2427  \fBpcre_free\fR directly; it is for these cases that the functions are  \fBpcre_free\fP directly; it is for these cases that the functions are
2428  provided.  provided.
2429    .
2430  .SH EXTRACTING CAPTURED SUBSTRINGS BY NAME  .
2431    .SH "EXTRACTING CAPTURED SUBSTRINGS BY NAME"
2432  .rs  .rs
2433  .sp  .sp
2434  .B int pcre_copy_named_substring(const pcre *\fIcode\fR,  .B int pcre_get_stringnumber(const pcre *\fIcode\fP,
2435  .ti +5n  .ti +5n
2436  .B const char *\fIsubject\fR, int *\fIovector\fR,  .B const char *\fIname\fP);
2437    .PP
2438    .B int pcre_copy_named_substring(const pcre *\fIcode\fP,
2439  .ti +5n  .ti +5n
2440  .B int \fIstringcount\fR, const char *\fIstringname\fR,  .B const char *\fIsubject\fP, int *\fIovector\fP,
2441  .ti +5n  .ti +5n
2442  .B char *\fIbuffer\fR, int \fIbuffersize\fR);  .B int \fIstringcount\fP, const char *\fIstringname\fP,
 .PP  
 .br  
 .B int pcre_get_stringnumber(const pcre *\fIcode\fR,  
2443  .ti +5n  .ti +5n
2444  .B const char *\fIname\fR);  .B char *\fIbuffer\fP, int \fIbuffersize\fP);
2445  .PP  .PP
2446  .br  .B int pcre_get_named_substring(const pcre *\fIcode\fP,
 .B int pcre_get_named_substring(const pcre *\fIcode\fR,  
2447  .ti +5n  .ti +5n
2448  .B const char *\fIsubject\fR, int *\fIovector\fR,  .B const char *\fIsubject\fP, int *\fIovector\fP,
2449  .ti +5n  .ti +5n
2450  .B int \fIstringcount\fR, const char *\fIstringname\fR,  .B int \fIstringcount\fP, const char *\fIstringname\fP,
2451  .ti +5n  .ti +5n
2452  .B const char **\fIstringptr\fR);  .B const char **\fIstringptr\fP);
2453  .PP  .PP
2454  To extract a substring by name, you first have to find associated number. This  To extract a substring by name, you first have to find associated number.
2455  can be done by calling \fBpcre_get_stringnumber()\fR. The first argument is the  For example, for this pattern
2456  compiled pattern, and the second is the name. For example, for this pattern  .sp
2457      (a+)b(?<xxx>\ed+)...
2458    ab(?<xxx>\\d+)...  .sp
2459    the number of the subpattern called "xxx" is 2. If the name is known to be
2460  the number of the subpattern called "xxx" is 1. Given the number, you can then  unique (PCRE_DUPNAMES was not set), you can find the number from the name by
2461  extract the substring directly, or use one of the functions described in the  calling \fBpcre_get_stringnumber()\fP. The first argument is the compiled
2462  previous section. For convenience, there are also two functions that do the  pattern, and the second is the name. The yield of the function is the
2463  whole job.  subpattern number, or PCRE_ERROR_NOSUBSTRING (-7) if there is no subpattern of
2464    that name.
2465  Most of the arguments of \fIpcre_copy_named_substring()\fR and  .P
2466  \fIpcre_get_named_substring()\fR are the same as those for the functions that  Given the number, you can extract the substring directly, or use one of the
2467  extract by number, and so are not re-described here. There are just two  functions described in the previous section. For convenience, there are also
2468  differences.  two functions that do the whole job.
2469    .P
2470    Most of the arguments of \fBpcre_copy_named_substring()\fP and
2471    \fBpcre_get_named_substring()\fP are the same as those for the similarly named
2472    functions that extract by number. As these are described in the previous
2473    section, they are not re-described here. There are just two differences:
2474    .P
2475  First, instead of a substring number, a substring name is given. Second, there  First, instead of a substring number, a substring name is given. Second, there
2476  is an extra argument, given at the start, which is a pointer to the compiled  is an extra argument, given at the start, which is a pointer to the compiled
2477  pattern. This is needed in order to gain access to the name-to-number  pattern. This is needed in order to gain access to the name-to-number
2478  translation table.  translation table.
2479    .P
2480  These functions call \fBpcre_get_stringnumber()\fR, and if it succeeds, they  These functions call \fBpcre_get_stringnumber()\fP, and if it succeeds, they
2481  then call \fIpcre_copy_substring()\fR or \fIpcre_get_substring()\fR, as  then call \fBpcre_copy_substring()\fP or \fBpcre_get_substring()\fP, as
2482  appropriate.  appropriate. \fBNOTE:\fP If PCRE_DUPNAMES is set and there are duplicate names,
2483    the behaviour may not be what you want (see the next section).
2484  .in 0  .P
2485  Last updated: 20 August 2003  \fBWarning:\fP If the pattern uses the (?| feature to set up multiple
2486  .br  subpatterns with the same number, as described in the
2487  Copyright (c) 1997-2003 University of Cambridge.  .\" HTML <a href="pcrepattern.html#dupsubpatternnumber">
2488    .\" </a>
2489    section on duplicate subpattern numbers
2490    .\"
2491    in the
2492    .\" HREF
2493    \fBpcrepattern\fP
2494    .\"
2495    page, you cannot use names to distinguish the different subpatterns, because
2496    names are not included in the compiled code. The matching process uses only
2497    numbers. For this reason, the use of different names for subpatterns of the
2498    same number causes an error at compile time.
2499    .
2500    .
2501    .SH "DUPLICATE SUBPATTERN NAMES"
2502    .rs
2503    .sp
2504    .B int pcre_get_stringtable_entries(const pcre *\fIcode\fP,
2505    .ti +5n
2506    .B const char *\fIname\fP, char **\fIfirst\fP, char **\fIlast\fP);
2507    .PP
2508    When a pattern is compiled with the PCRE_DUPNAMES option, names for subpatterns
2509    are not required to be unique. (Duplicate names are always allowed for
2510    subpatterns with the same number, created by using the (?| feature. Indeed, if
2511    such subpatterns are named, they are required to use the same names.)
2512    .P
2513    Normally, patterns with duplicate names are such that in any one match, only
2514    one of the named subpatterns participates. An example is shown in the
2515    .\" HREF
2516    \fBpcrepattern\fP
2517    .\"
2518    documentation.
2519    .P
2520    When duplicates are present, \fBpcre_copy_named_substring()\fP and
2521    \fBpcre_get_named_substring()\fP return the first substring corresponding to
2522    the given name that is set. If none are set, PCRE_ERROR_NOSUBSTRING (-7) is
2523    returned; no data is returned. The \fBpcre_get_stringnumber()\fP function
2524    returns one of the numbers that are associated with the name, but it is not
2525    defined which it is.
2526    .P
2527    If you want to get full details of all captured substrings for a given name,
2528    you must use the \fBpcre_get_stringtable_entries()\fP function. The first
2529    argument is the compiled pattern, and the second is the name. The third and
2530    fourth are pointers to variables which are updated by the function. After it
2531    has run, they point to the first and last entries in the name-to-number table
2532    for the given name. The function itself returns the length of each entry, or
2533    PCRE_ERROR_NOSUBSTRING (-7) if there are none. The format of the table is
2534    described above in the section entitled \fIInformation about a pattern\fP
2535    .\" HTML <a href="#infoaboutpattern">
2536    .\" </a>
2537    above.
2538    .\"
2539    Given all the relevant entries for the name, you can extract each of their
2540    numbers, and hence the captured data, if any.
2541    .
2542    .
2543    .SH "FINDING ALL POSSIBLE MATCHES"
2544    .rs
2545    .sp
2546    The traditional matching function uses a similar algorithm to Perl, which stops
2547    when it finds the first match, starting at a given point in the subject. If you
2548    want to find all possible matches, or the longest possible match, consider
2549    using the alternative matching function (see below) instead. If you cannot use
2550    the alternative function, but still need to find all possible matches, you
2551    can kludge it up by making use of the callout facility, which is described in
2552    the
2553    .\" HREF
2554    \fBpcrecallout\fP
2555    .\"
2556    documentation.
2557    .P
2558    What you have to do is to insert a callout right at the end of the pattern.
2559    When your callout function is called, extract and save the current matched
2560    substring. Then return 1, which forces \fBpcre_exec()\fP to backtrack and try
2561    other alternatives. Ultimately, when it runs out of matches, \fBpcre_exec()\fP
2562    will yield PCRE_ERROR_NOMATCH.
2563    .
2564    .
2565    .SH "OBTAINING AN ESTIMATE OF STACK USAGE"
2566    .rs
2567    .sp
2568    Matching certain patterns using \fBpcre_exec()\fP can use a lot of process
2569    stack, which in certain environments can be rather limited in size. Some users
2570    find it helpful to have an estimate of the amount of stack that is used by
2571    \fBpcre_exec()\fP, to help them set recursion limits, as described in the
2572    .\" HREF
2573    \fBpcrestack\fP
2574    .\"
2575    documentation. The estimate that is output by \fBpcretest\fP when called with
2576    the \fB-m\fP and \fB-C\fP options is obtained by calling \fBpcre_exec\fP with
2577    the values NULL, NULL, NULL, -999, and -999 for its first five arguments.
2578    .P
2579    Normally, if its first argument is NULL, \fBpcre_exec()\fP immediately returns
2580    the negative error code PCRE_ERROR_NULL, but with this special combination of
2581    arguments, it returns instead a negative number whose absolute value is the
2582    approximate stack frame size in bytes. (A negative number is used so that it is
2583    clear that no match has happened.) The value is approximate because in some
2584    cases, recursive calls to \fBpcre_exec()\fP occur when there are one or two
2585    additional variables on the stack.
2586    .P
2587    If PCRE has been compiled to use the heap instead of the stack for recursion,
2588    the value returned is the size of each block that is obtained from the heap.
2589    .
2590    .
2591    .\" HTML <a name="dfamatch"></a>
2592    .SH "MATCHING A PATTERN: THE ALTERNATIVE FUNCTION"
2593    .rs
2594    .sp
2595    .B int pcre_dfa_exec(const pcre *\fIcode\fP, "const pcre_extra *\fIextra\fP,"
2596    .ti +5n
2597    .B "const char *\fIsubject\fP," int \fIlength\fP, int \fIstartoffset\fP,
2598    .ti +5n
2599    .B int \fIoptions\fP, int *\fIovector\fP, int \fIovecsize\fP,
2600    .ti +5n
2601    .B int *\fIworkspace\fP, int \fIwscount\fP);
2602    .P
2603    The function \fBpcre_dfa_exec()\fP is called to match a subject string against
2604    a compiled pattern, using a matching algorithm that scans the subject string
2605    just once, and does not backtrack. This has different characteristics to the
2606    normal algorithm, and is not compatible with Perl. Some of the features of PCRE
2607    patterns are not supported. Nevertheless, there are times when this kind of
2608    matching can be useful. For a discussion of the two matching algorithms, and a
2609    list of features that \fBpcre_dfa_exec()\fP does not support, see the
2610    .\" HREF
2611    \fBpcrematching\fP
2612    .\"
2613    documentation.
2614    .P
2615    The arguments for the \fBpcre_dfa_exec()\fP function are the same as for
2616    \fBpcre_exec()\fP, plus two extras. The \fIovector\fP argument is used in a
2617    different way, and this is described below. The other common arguments are used
2618    in the same way as for \fBpcre_exec()\fP, so their description is not repeated
2619    here.
2620    .P
2621    The two additional arguments provide workspace for the function. The workspace
2622    vector should contain at least 20 elements. It is used for keeping track of
2623    multiple paths through the pattern tree. More workspace will be needed for
2624    patterns and subjects where there are a lot of potential matches.
2625    .P
2626    Here is an example of a simple call to \fBpcre_dfa_exec()\fP:
2627    .sp
2628      int rc;
2629      int ovector[10];
2630      int wspace[20];
2631      rc = pcre_dfa_exec(
2632        re,             /* result of pcre_compile() */
2633        NULL,           /* we didn't study the pattern */
2634        "some string",  /* the subject string */
2635        11,             /* the length of the subject string */
2636        0,              /* start at offset 0 in the subject */
2637        0,              /* default options */
2638        ovector,        /* vector of integers for substring information */
2639        10,             /* number of elements (NOT size in bytes) */
2640        wspace,         /* working space vector */
2641        20);            /* number of elements (NOT size in bytes) */
2642    .
2643    .SS "Option bits for \fBpcre_dfa_exec()\fP"
2644    .rs
2645    .sp
2646    The unused bits of the \fIoptions\fP argument for \fBpcre_dfa_exec()\fP must be
2647    zero. The only bits that may be set are PCRE_ANCHORED, PCRE_NEWLINE_\fIxxx\fP,
2648    PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY, PCRE_NOTEMPTY_ATSTART,
2649    PCRE_NO_UTF8_CHECK, PCRE_BSR_ANYCRLF, PCRE_BSR_UNICODE, PCRE_NO_START_OPTIMIZE,
2650    PCRE_PARTIAL_HARD, PCRE_PARTIAL_SOFT, PCRE_DFA_SHORTEST, and PCRE_DFA_RESTART.
2651    All but the last four of these are exactly the same as for \fBpcre_exec()\fP,
2652    so their description is not repeated here.
2653    .sp
2654      PCRE_PARTIAL_HARD
2655      PCRE_PARTIAL_SOFT
2656    .sp
2657    These have the same general effect as they do for \fBpcre_exec()\fP, but the
2658    details are slightly different. When PCRE_PARTIAL_HARD is set for
2659    \fBpcre_dfa_exec()\fP, it returns PCRE_ERROR_PARTIAL if the end of the subject
2660    is reached and there is still at least one matching possibility that requires
2661    additional characters. This happens even if some complete matches have also
2662    been found. When PCRE_PARTIAL_SOFT is set, the return code PCRE_ERROR_NOMATCH
2663    is converted into PCRE_ERROR_PARTIAL if the end of the subject is reached,
2664    there have been no complete matches, but there is still at least one matching
2665    possibility. The portion of the string that was inspected when the longest
2666    partial match was found is set as the first matching string in both cases.
2667    There is a more detailed discussion of partial and multi-segment matching, with
2668    examples, in the
2669    .\" HREF
2670    \fBpcrepartial\fP
2671    .\"
2672    documentation.
2673    .sp
2674      PCRE_DFA_SHORTEST
2675    .sp
2676    Setting the PCRE_DFA_SHORTEST option causes the matching algorithm to stop as
2677    soon as it has found one match. Because of the way the alternative algorithm
2678    works, this is necessarily the shortest possible match at the first possible
2679    matching point in the subject string.
2680    .sp
2681      PCRE_DFA_RESTART
2682    .sp
2683    When \fBpcre_dfa_exec()\fP returns a partial match, it is possible to call it
2684    again, with additional subject characters, and have it continue with the same
2685    match. The PCRE_DFA_RESTART option requests this action; when it is set, the
2686    \fIworkspace\fP and \fIwscount\fP options must reference the same vector as
2687    before because data about the match so far is left in them after a partial
2688    match. There is more discussion of this facility in the
2689    .\" HREF
2690    \fBpcrepartial\fP
2691    .\"
2692    documentation.
2693    .
2694    .
2695    .SS "Successful returns from \fBpcre_dfa_exec()\fP"
2696    .rs
2697    .sp
2698    When \fBpcre_dfa_exec()\fP succeeds, it may have matched more than one
2699    substring in the subject. Note, however, that all the matches from one run of
2700    the function start at the same point in the subject. The shorter matches are
2701    all initial substrings of the longer matches. For example, if the pattern
2702    .sp
2703      <.*>
2704    .sp
2705    is matched against the string
2706    .sp
2707      This is <something> <something else> <something further> no more
2708    .sp
2709    the three matched strings are
2710    .sp
2711      <something>
2712      <something> <something else>
2713      <something> <something else> <something further>
2714    .sp
2715    On success, the yield of the function is a number greater than zero, which is
2716    the number of matched substrings. The substrings themselves are returned in
2717    \fIovector\fP. Each string uses two elements; the first is the offset to the
2718    start, and the second is the offset to the end. In fact, all the strings have
2719    the same start offset. (Space could have been saved by giving this only once,
2720    but it was decided to retain some compatibility with the way \fBpcre_exec()\fP
2721    returns data, even though the meaning of the strings is different.)
2722    .P
2723    The strings are returned in reverse order of length; that is, the longest
2724    matching string is given first. If there were too many matches to fit into
2725    \fIovector\fP, the yield of the function is zero, and the vector is filled with
2726    the longest matches. Unlike \fBpcre_exec()\fP, \fBpcre_dfa_exec()\fP can use
2727    the entire \fIovector\fP for returning matched strings.
2728    .
2729    .
2730    .SS "Error returns from \fBpcre_dfa_exec()\fP"
2731    .rs
2732    .sp
2733    The \fBpcre_dfa_exec()\fP function returns a negative number when it fails.
2734    Many of the errors are the same as for \fBpcre_exec()\fP, and these are
2735    described
2736    .\" HTML <a href="#errorlist">
2737    .\" </a>
2738    above.
2739    .\"
2740    There are in addition the following errors that are specific to
2741    \fBpcre_dfa_exec()\fP:
2742    .sp
2743      PCRE_ERROR_DFA_UITEM      (-16)
2744    .sp
2745    This return is given if \fBpcre_dfa_exec()\fP encounters an item in the pattern
2746    that it does not support, for instance, the use of \eC or a back reference.
2747    .sp
2748      PCRE_ERROR_DFA_UCOND      (-17)
2749    .sp
2750    This return is given if \fBpcre_dfa_exec()\fP encounters a condition item that
2751    uses a back reference for the condition, or a test for recursion in a specific
2752    group. These are not supported.
2753    .sp
2754      PCRE_ERROR_DFA_UMLIMIT    (-18)
2755    .sp
2756    This return is given if \fBpcre_dfa_exec()\fP is called with an \fIextra\fP
2757    block that contains a setting of the \fImatch_limit\fP or
2758    \fImatch_limit_recursion\fP fields. This is not supported (these fields are
2759    meaningless for DFA matching).
2760    .sp
2761      PCRE_ERROR_DFA_WSSIZE     (-19)
2762    .sp
2763    This return is given if \fBpcre_dfa_exec()\fP runs out of space in the
2764    \fIworkspace\fP vector.
2765    .sp
2766      PCRE_ERROR_DFA_RECURSE    (-20)
2767    .sp
2768    When a recursive subpattern is processed, the matching function calls itself
2769    recursively, using private vectors for \fIovector\fP and \fIworkspace\fP. This
2770    error is given if the output vector is not large enough. This should be
2771    extremely rare, as a vector of size 1000 is used.
2772    .sp
2773      PCRE_ERROR_DFA_BADRESTART (-30)
2774    .sp
2775    When \fBpcre_dfa_exec()\fP is called with the \fBPCRE_DFA_RESTART\fP option,
2776    some plausibility checks are made on the contents of the workspace, which
2777    should contain data about the previous partial match. If any of these checks
2778    fail, this error is given.
2779    .
2780    .
2781    .SH "SEE ALSO"
2782    .rs
2783    .sp
2784    \fBpcre16\fP(3), \fBpcre32\fP(3), \fBpcrebuild\fP(3), \fBpcrecallout\fP(3),
2785    \fBpcrecpp(3)\fP(3), \fBpcrematching\fP(3), \fBpcrepartial\fP(3),
2786    \fBpcreposix\fP(3), \fBpcreprecompile\fP(3), \fBpcresample\fP(3),
2787    \fBpcrestack\fP(3).
2788    .
2789    .
2790    .SH AUTHOR
2791    .rs
2792    .sp
2793    .nf
2794    Philip Hazel
2795    University Computing Service
2796    Cambridge CB2 3QH, England.
2797    .fi
2798    .
2799    .
2800    .SH REVISION
2801    .rs
2802    .sp
2803    .nf
2804    Last updated: 07 September 2012
2805    Copyright (c) 1997-2012 University of Cambridge.
2806    .fi

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