/[pcre]/code/trunk/doc/pcreapi.3
ViewVC logotype

Diff of /code/trunk/doc/pcreapi.3

Parent Directory Parent Directory | Revision Log Revision Log | View Patch Patch

revision 71 by nigel, Sat Feb 24 21:40:24 2007 UTC revision 1194 by ph10, Wed Oct 31 17:42:29 2012 UTC
# Line 1  Line 1 
1  .TH PCRE 3  .TH PCREAPI 3 "31 October 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 int pcre_jit_exec(const pcre *\fIcode\fP, "const pcre_extra *\fIextra\fP,"
99    .ti +5n
100    .B "const char *\fIsubject\fP," int \fIlength\fP, int \fIstartoffset\fP,
101    .ti +5n
102    .B int \fIoptions\fP, int *\fIovector\fP, int \fIovecsize\fP,
103    .ti +5n
104    .B pcre_jit_stack *\fIjstack\fP);
105    .PP
106    .B pcre_jit_stack *pcre_jit_stack_alloc(int \fIstartsize\fP, int \fImaxsize\fP);
107    .PP
108    .B void pcre_jit_stack_free(pcre_jit_stack *\fIstack\fP);
109    .PP
110    .B void pcre_assign_jit_stack(pcre_extra *\fIextra\fP,
111    .ti +5n
112    .B pcre_jit_callback \fIcallback\fP, void *\fIdata\fP);
113  .PP  .PP
 .br  
114  .B const unsigned char *pcre_maketables(void);  .B const unsigned char *pcre_maketables(void);
115  .PP  .PP
116  .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,"  
117  .ti +5n  .ti +5n
118  .B int \fIwhat\fR, void *\fIwhere\fR);  .B int \fIwhat\fP, void *\fIwhere\fP);
119  .PP  .PP
120  .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);  
121  .PP  .PP
122  .br  .B int pcre_config(int \fIwhat\fP, void *\fIwhere\fP);
 .B int pcre_config(int \fIwhat\fR, void *\fIwhere\fR);  
123  .PP  .PP
124  .br  .B const char *pcre_version(void);
 .B char *pcre_version(void);  
125  .PP  .PP
126  .br  .B int pcre_pattern_to_host_byte_order(pcre *\fIcode\fP,
127    .ti +5n
128    .B pcre_extra *\fIextra\fP, const unsigned char *\fItables\fP);
129    .
130    .
131    .SH "PCRE NATIVE API INDIRECTED FUNCTIONS"
132    .rs
133    .sp
134  .B void *(*pcre_malloc)(size_t);  .B void *(*pcre_malloc)(size_t);
135  .PP  .PP
 .br  
136  .B void (*pcre_free)(void *);  .B void (*pcre_free)(void *);
137  .PP  .PP
138  .br  .B void *(*pcre_stack_malloc)(size_t);
139    .PP
140    .B void (*pcre_stack_free)(void *);
141    .PP
142  .B int (*pcre_callout)(pcre_callout_block *);  .B int (*pcre_callout)(pcre_callout_block *);
143    .
144  .SH PCRE API  .
145    .SH "PCRE 8-BIT, 16-BIT AND 32-BIT LIBRARIES"
146    .rs
147    .sp
148    From release 8.30, PCRE can be compiled as a library for handling 16-bit
149    character strings as well as, or instead of, the original library that handles
150    8-bit character strings. From release 8.32, PCRE can also be compiled as a
151    library for handling 32-bit character strings. To avoid too much complication,
152    this document describes the 8-bit versions of the functions, with only
153    occasional references to the 16-bit and 32-bit libraries.
154    .P
155    The 16-bit and 32-bit functions operate in the same way as their 8-bit
156    counterparts; they just use different data types for their arguments and
157    results, and their names start with \fBpcre16_\fP or \fBpcre32_\fP instead of
158    \fBpcre_\fP. For every option that has UTF8 in its name (for example,
159    PCRE_UTF8), there are corresponding 16-bit and 32-bit names with UTF8 replaced
160    by UTF16 or UTF32, respectively. This facility is in fact just cosmetic; the
161    16-bit and 32-bit option names define the same bit values.
162    .P
163    References to bytes and UTF-8 in this document should be read as references to
164    16-bit data quantities and UTF-16 when using the 16-bit library, or 32-bit data
165    quantities and UTF-32 when using the 32-bit library, unless specified
166    otherwise. More details of the specific differences for the 16-bit and 32-bit
167    libraries are given in the
168    .\" HREF
169    \fBpcre16\fP
170    .\"
171    and
172    .\" HREF
173    \fBpcre32\fP
174    .\"
175    pages.
176    .
177    .
178    .SH "PCRE API OVERVIEW"
179  .rs  .rs
180  .sp  .sp
181  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
182  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
183  These are described in the \fBpcreposix\fR documentation.  POSIX regular expression API, but they do not give access to all the
184    functionality. They are described in the
185  The native API function prototypes are defined in the header file \fBpcre.h\fR,  .\" HREF
186  and on Unix systems the library itself is called \fBlibpcre.a\fR, so can be  \fBpcreposix\fP
187  accessed by adding \fB-lpcre\fR to the command for linking an application which  .\"
188  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++
189  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
190  use these to include support for different releases.  documented in the
191    .\" HREF
192  The functions \fBpcre_compile()\fR, \fBpcre_study()\fR, and \fBpcre_exec()\fR  \fBpcrecpp\fP
193  are used for compiling and matching regular expressions. A sample program that  .\"
194  demonstrates the simplest way of using them is given in the file  page.
195  \fIpcredemo.c\fR. The \fBpcresample\fR documentation describes how to run it.  .P
196    The native API C function prototypes are defined in the header file
197  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
198  matched subject string. They are:  \fBlibpcre\fP. It can normally be accessed by adding \fB-lpcre\fP to the
199    command for linking an application that uses PCRE. The header file defines the
200    \fBpcre_copy_substring()\fR  macros PCRE_MAJOR and PCRE_MINOR to contain the major and minor release numbers
201    \fBpcre_copy_named_substring()\fR  for the library. Applications can use these to include support for different
202    \fBpcre_get_substring()\fR  releases of PCRE.
203    \fBpcre_get_named_substring()\fR  .P
204    \fBpcre_get_substring_list()\fR  In a Windows environment, if you want to statically link an application program
205    against a non-dll \fBpcre.a\fP file, you must define PCRE_STATIC before
206  \fBpcre_free_substring()\fR and \fBpcre_free_substring_list()\fR are also  including \fBpcre.h\fP or \fBpcrecpp.h\fP, because otherwise the
207    \fBpcre_malloc()\fP and \fBpcre_free()\fP exported functions will be declared
208    \fB__declspec(dllimport)\fP, with unwanted results.
209    .P
210    The functions \fBpcre_compile()\fP, \fBpcre_compile2()\fP, \fBpcre_study()\fP,
211    and \fBpcre_exec()\fP are used for compiling and matching regular expressions
212    in a Perl-compatible manner. A sample program that demonstrates the simplest
213    way of using them is provided in the file called \fIpcredemo.c\fP in the PCRE
214    source distribution. A listing of this program is given in the
215    .\" HREF
216    \fBpcredemo\fP
217    .\"
218    documentation, and the
219    .\" HREF
220    \fBpcresample\fP
221    .\"
222    documentation describes how to compile and run it.
223    .P
224    Just-in-time compiler support is an optional feature of PCRE that can be built
225    in appropriate hardware environments. It greatly speeds up the matching
226    performance of many patterns. Simple programs can easily request that it be
227    used if available, by setting an option that is ignored when it is not
228    relevant. More complicated programs might need to make use of the functions
229    \fBpcre_jit_stack_alloc()\fP, \fBpcre_jit_stack_free()\fP, and
230    \fBpcre_assign_jit_stack()\fP in order to control the JIT code's memory usage.
231    .P
232    From release 8.32 there is also a direct interface for JIT execution, which
233    gives improved performance. The JIT-specific functions are discussed in the
234    .\" HREF
235    \fBpcrejit\fP
236    .\"
237    documentation.
238    .P
239    A second matching function, \fBpcre_dfa_exec()\fP, which is not
240    Perl-compatible, is also provided. This uses a different algorithm for the
241    matching. The alternative algorithm finds all possible matches (at a given
242    point in the subject), and scans the subject just once (unless there are
243    lookbehind assertions). However, this algorithm does not return captured
244    substrings. A description of the two matching algorithms and their advantages
245    and disadvantages is given in the
246    .\" HREF
247    \fBpcrematching\fP
248    .\"
249    documentation.
250    .P
251    In addition to the main compiling and matching functions, there are convenience
252    functions for extracting captured substrings from a subject string that is
253    matched by \fBpcre_exec()\fP. They are:
254    .sp
255      \fBpcre_copy_substring()\fP
256      \fBpcre_copy_named_substring()\fP
257      \fBpcre_get_substring()\fP
258      \fBpcre_get_named_substring()\fP
259      \fBpcre_get_substring_list()\fP
260      \fBpcre_get_stringnumber()\fP
261      \fBpcre_get_stringtable_entries()\fP
262    .sp
263    \fBpcre_free_substring()\fP and \fBpcre_free_substring_list()\fP are also
264  provided, to free the memory used for extracted strings.  provided, to free the memory used for extracted strings.
265    .P
266  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
267  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,
268    or \fBpcre_dfa_exec()\fP. This is an optional facility that is provided for
269  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
270  compiled pattern; \fBpcre_info()\fR is an obsolete version which returns only  internal tables that are generated when PCRE is built are used.
271  some of the available information, but is retained for backwards compatibility.  .P
272  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
273  version of PCRE and its date of release.  compiled pattern. The function \fBpcre_version()\fP returns a pointer to a
274    string containing the version of PCRE and its date of release.
275  The global variables \fBpcre_malloc\fR and \fBpcre_free\fR initially contain  .P
276  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
277    containing a compiled pattern. This is provided for the benefit of
278    object-oriented applications.
279    .P
280    The global variables \fBpcre_malloc\fP and \fBpcre_free\fP initially contain
281    the entry points of the standard \fBmalloc()\fP and \fBfree()\fP functions,
282  respectively. PCRE calls the memory management functions via these variables,  respectively. PCRE calls the memory management functions via these variables,
283  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
284  should be done before calling any PCRE functions.  should be done before calling any PCRE functions.
285    .P
286  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
287    indirections to memory management functions. These special functions are used
288    only when PCRE is compiled to use the heap for remembering data, instead of
289    recursive function calls, when running the \fBpcre_exec()\fP function. See the
290    .\" HREF
291    \fBpcrebuild\fP
292    .\"
293    documentation for details of how to do this. It is a non-standard way of
294    building PCRE, for use in environments that have limited stacks. Because of the
295    greater use of memory management, it runs more slowly. Separate functions are
296    provided so that special-purpose external code can be used for this case. When
297    used, these functions are always called in a stack-like manner (last obtained,
298    first freed), and always for memory blocks of the same size. There is a
299    discussion about PCRE's stack usage in the
300    .\" HREF
301    \fBpcrestack\fP
302    .\"
303    documentation.
304    .P
305    The global variable \fBpcre_callout\fP initially contains NULL. It can be set
306  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
307  points during a matching operation. Details are given in the \fBpcrecallout\fR  points during a matching operation. Details are given in the
308    .\" HREF
309    \fBpcrecallout\fP
310    .\"
311  documentation.  documentation.
312    .
313    .
314    .\" HTML <a name="newlines"></a>
315    .SH NEWLINES
316    .rs
317    .sp
318    PCRE supports five different conventions for indicating line breaks in
319    strings: a single CR (carriage return) character, a single LF (linefeed)
320    character, the two-character sequence CRLF, any of the three preceding, or any
321    Unicode newline sequence. The Unicode newline sequences are the three just
322    mentioned, plus the single characters VT (vertical tab, U+000B), FF (form feed,
323    U+000C), NEL (next line, U+0085), LS (line separator, U+2028), and PS
324    (paragraph separator, U+2029).
325    .P
326    Each of the first three conventions is used by at least one operating system as
327    its standard newline sequence. When PCRE is built, a default can be specified.
328    The default default is LF, which is the Unix standard. When PCRE is run, the
329    default can be overridden, either when a pattern is compiled, or when it is
330    matched.
331    .P
332    At compile time, the newline convention can be specified by the \fIoptions\fP
333    argument of \fBpcre_compile()\fP, or it can be specified by special text at the
334    start of the pattern itself; this overrides any other settings. See the
335    .\" HREF
336    \fBpcrepattern\fP
337    .\"
338    page for details of the special character sequences.
339    .P
340    In the PCRE documentation the word "newline" is used to mean "the character or
341    pair of characters that indicate a line break". The choice of newline
342    convention affects the handling of the dot, circumflex, and dollar
343    metacharacters, the handling of #-comments in /x mode, and, when CRLF is a
344    recognized line ending sequence, the match position advancement for a
345    non-anchored pattern. There is more detail about this in the
346    .\" HTML <a href="#execoptions">
347    .\" </a>
348    section on \fBpcre_exec()\fP options
349    .\"
350    below.
351    .P
352    The choice of newline convention does not affect the interpretation of
353    the \en or \er escape sequences, nor does it affect what \eR matches, which is
354    controlled in a similar way, but by separate options.
355    .
356    .
357  .SH MULTITHREADING  .SH MULTITHREADING
358  .rs  .rs
359  .sp  .sp
360  The PCRE functions can be used in multi-threading applications, with the  The PCRE functions can be used in multi-threading applications, with the
361  proviso that the memory management functions pointed to by \fBpcre_malloc\fR  proviso that the memory management functions pointed to by \fBpcre_malloc\fP,
362  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
363  are shared by all threads.  callout function pointed to by \fBpcre_callout\fP, are shared by all threads.
364    .P
365  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
366  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.
367    .P
368  .SH CHECKING BUILD-TIME OPTIONS  If the just-in-time optimization feature is being used, it needs separate
369    memory stack areas for each thread. See the
370    .\" HREF
371    \fBpcrejit\fP
372    .\"
373    documentation for more details.
374    .
375    .
376    .SH "SAVING PRECOMPILED PATTERNS FOR LATER USE"
377    .rs
378    .sp
379    The compiled form of a regular expression can be saved and re-used at a later
380    time, possibly by a different program, and even on a host other than the one on
381    which it was compiled. Details are given in the
382    .\" HREF
383    \fBpcreprecompile\fP
384    .\"
385    documentation, which includes a description of the
386    \fBpcre_pattern_to_host_byte_order()\fP function. However, compiling a regular
387    expression with one version of PCRE for use with a different version is not
388    guaranteed to work and may cause crashes.
389    .
390    .
391    .SH "CHECKING BUILD-TIME OPTIONS"
392  .rs  .rs
393  .sp  .sp
394  .B int pcre_config(int \fIwhat\fR, void *\fIwhere\fR);  .B int pcre_config(int \fIwhat\fP, void *\fIwhere\fP);
395  .PP  .PP
396  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
397  discover which optional features have been compiled into the PCRE library. The  discover which optional features have been compiled into the PCRE library. The
398  .\" HREF  .\" HREF
399  \fBpcrebuild\fR  \fBpcrebuild\fP
400  .\"  .\"
401  documentation has more details about these optional features.  documentation has more details about these optional features.
402    .P
403  The first argument for \fBpcre_config()\fR is an integer, specifying which  The first argument for \fBpcre_config()\fP is an integer, specifying which
404  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
405  which the information is placed. The following information is available:  which the information is placed. The returned value is zero on success, or the
406    negative error code PCRE_ERROR_BADOPTION if the value in the first argument is
407    not recognized. The following information is available:
408    .sp
409    PCRE_CONFIG_UTF8    PCRE_CONFIG_UTF8
410    .sp
411  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;
412  otherwise it is set to zero.  otherwise it is set to zero. This value should normally be given to the 8-bit
413    version of this function, \fBpcre_config()\fP. If it is given to the 16-bit
414    or 32-bit version of this function, the result is PCRE_ERROR_BADOPTION.
415    .sp
416      PCRE_CONFIG_UTF16
417    .sp
418    The output is an integer that is set to one if UTF-16 support is available;
419    otherwise it is set to zero. This value should normally be given to the 16-bit
420    version of this function, \fBpcre16_config()\fP. If it is given to the 8-bit
421    or 32-bit version of this function, the result is PCRE_ERROR_BADOPTION.
422    .sp
423      PCRE_CONFIG_UTF32
424    .sp
425    The output is an integer that is set to one if UTF-32 support is available;
426    otherwise it is set to zero. This value should normally be given to the 32-bit
427    version of this function, \fBpcre32_config()\fP. If it is given to the 8-bit
428    or 16-bit version of this function, the result is PCRE_ERROR_BADOPTION.
429    .sp
430      PCRE_CONFIG_UNICODE_PROPERTIES
431    .sp
432    The output is an integer that is set to one if support for Unicode character
433    properties is available; otherwise it is set to zero.
434    .sp
435      PCRE_CONFIG_JIT
436    .sp
437    The output is an integer that is set to one if support for just-in-time
438    compiling is available; otherwise it is set to zero.
439    .sp
440      PCRE_CONFIG_JITTARGET
441    .sp
442    The output is a pointer to a zero-terminated "const char *" string. If JIT
443    support is available, the string contains the name of the architecture for
444    which the JIT compiler is configured, for example "x86 32bit (little endian +
445    unaligned)". If JIT support is not available, the result is NULL.
446    .sp
447    PCRE_CONFIG_NEWLINE    PCRE_CONFIG_NEWLINE
448    .sp
449  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
450  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
451  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
452    ANYCRLF, and -1 for ANY. In EBCDIC environments, CR, ANYCRLF, and ANY yield the
453    same values. However, the value for LF is normally 21, though some EBCDIC
454    environments use 37. The corresponding values for CRLF are 3349 and 3365. The
455    default should normally correspond to the standard sequence for your operating
456    system.
457    .sp
458      PCRE_CONFIG_BSR
459    .sp
460    The output is an integer whose value indicates what character sequences the \eR
461    escape sequence matches by default. A value of 0 means that \eR matches any
462    Unicode line ending sequence; a value of 1 means that \eR matches only CR, LF,
463    or CRLF. The default can be overridden when a pattern is compiled or matched.
464    .sp
465    PCRE_CONFIG_LINK_SIZE    PCRE_CONFIG_LINK_SIZE
466    .sp
467  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
468  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
469  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
470  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
471  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
472    most massive patterns, since it allows the compiled pattern to be up to 64K in
473    size. Larger values allow larger regular expressions to be compiled, at the
474    expense of slower matching.
475    .sp
476    PCRE_CONFIG_POSIX_MALLOC_THRESHOLD    PCRE_CONFIG_POSIX_MALLOC_THRESHOLD
477    .sp
478  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
479  interface uses \fBmalloc()\fR for output vectors. Further details are given in  interface uses \fBmalloc()\fP for output vectors. Further details are given in
480  the \fBpcreposix\fR documentation.  the
481    .\" HREF
482    \fBpcreposix\fP
483    .\"
484    documentation.
485    .sp
486    PCRE_CONFIG_MATCH_LIMIT    PCRE_CONFIG_MATCH_LIMIT
487    .sp
488  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
489  internal matching function calls in a \fBpcre_exec()\fR execution. Further  internal matching function calls in a \fBpcre_exec()\fP execution. Further
490  details are given with \fBpcre_exec()\fR below.  details are given with \fBpcre_exec()\fP below.
491    .sp
492  .SH COMPILING A PATTERN    PCRE_CONFIG_MATCH_LIMIT_RECURSION
493  .rs  .sp
494  .sp  The output is a long integer that gives the default limit for the depth of
495  .B pcre *pcre_compile(const char *\fIpattern\fR, int \fIoptions\fR,  recursion when calling the internal matching function in a \fBpcre_exec()\fP
496  .ti +5n  execution. Further details are given with \fBpcre_exec()\fP below.
497  .B const char **\fIerrptr\fR, int *\fIerroffset\fR,  .sp
498  .ti +5n    PCRE_CONFIG_STACKRECURSE
499  .B const unsigned char *\fItableptr\fR);  .sp
500  .PP  The output is an integer that is set to one if internal recursion when running
501    \fBpcre_exec()\fP is implemented by recursive function calls that use the stack
502  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
503  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
504  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
505  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
506  code and related data. The \fBpcre\fR type is defined for the returned block;  avoiding the use of the stack.
507  this is a typedef for a structure whose contents are not externally defined. It  .
508  is up to the caller to free the memory when it is no longer required.  .
509    .SH "COMPILING A PATTERN"
510    .rs
511    .sp
512    .B pcre *pcre_compile(const char *\fIpattern\fP, int \fIoptions\fP,
513    .ti +5n
514    .B const char **\fIerrptr\fP, int *\fIerroffset\fP,
515    .ti +5n
516    .B const unsigned char *\fItableptr\fP);
517    .sp
518    .B pcre *pcre_compile2(const char *\fIpattern\fP, int \fIoptions\fP,
519    .ti +5n
520    .B int *\fIerrorcodeptr\fP,
521    .ti +5n
522    .B const char **\fIerrptr\fP, int *\fIerroffset\fP,
523    .ti +5n
524    .B const unsigned char *\fItableptr\fP);
525    .P
526    Either of the functions \fBpcre_compile()\fP or \fBpcre_compile2()\fP can be
527    called to compile a pattern into an internal form. The only difference between
528    the two interfaces is that \fBpcre_compile2()\fP has an additional argument,
529    \fIerrorcodeptr\fP, via which a numerical error code can be returned. To avoid
530    too much repetition, we refer just to \fBpcre_compile()\fP below, but the
531    information applies equally to \fBpcre_compile2()\fP.
532    .P
533    The pattern is a C string terminated by a binary zero, and is passed in the
534    \fIpattern\fP argument. A pointer to a single block of memory that is obtained
535    via \fBpcre_malloc\fP is returned. This contains the compiled code and related
536    data. The \fBpcre\fP type is defined for the returned block; this is a typedef
537    for a structure whose contents are not externally defined. It is up to the
538    caller to free the memory (via \fBpcre_free\fP) when it is no longer required.
539    .P
540  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
541  depend on memory location, the complete \fBpcre\fR data block is not  depend on memory location, the complete \fBpcre\fP data block is not
542  fully relocatable, because it contains a copy of the \fItableptr\fR argument,  fully relocatable, because it may contain a copy of the \fItableptr\fP
543  which is an address (see below).  argument, which is an address (see below).
544    .P
545  The \fIoptions\fR argument contains independent bits that affect the  The \fIoptions\fP argument contains various bit settings that affect the
546  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
547  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
548  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
549  in the \fBpcrepattern\fR documentation). For these options, the contents of the  within the pattern (see the detailed description in the
550  \fIoptions\fR argument specifies their initial settings at the start of  .\" HREF
551  compilation and execution. The PCRE_ANCHORED option can be set at the time of  \fBpcrepattern\fP
552  matching as well as at compile time.  .\"
553    documentation). For those options that can be different in different parts of
554  If \fIerrptr\fR is NULL, \fBpcre_compile()\fR returns NULL immediately.  the pattern, the contents of the \fIoptions\fP argument specifies their
555  Otherwise, if compilation of a pattern fails, \fBpcre_compile()\fR returns  settings at the start of compilation and execution. The PCRE_ANCHORED,
556  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
557  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
558  the error was discovered is placed in the variable pointed to by  compile time.
559  \fIerroffset\fR, which must not be NULL. If it is, an immediate error is given.  .P
560    If \fIerrptr\fP is NULL, \fBpcre_compile()\fP returns NULL immediately.
561  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
562  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
563  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
564  \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
565    byte that was being processed when the error was discovered is placed in the
566  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
567    immediate error is given). However, for an invalid UTF-8 string, the offset is
568    that of the first byte of the failing character.
569    .P
570    Some errors are not detected until the whole pattern has been scanned; in these
571    cases, the offset passed back is the length of the pattern. Note that the
572    offset is in bytes, not characters, even in UTF-8 mode. It may sometimes point
573    into the middle of a UTF-8 character.
574    .P
575    If \fBpcre_compile2()\fP is used instead of \fBpcre_compile()\fP, and the
576    \fIerrorcodeptr\fP argument is not NULL, a non-zero error code number is
577    returned via this argument in the event of an error. This is in addition to the
578    textual error message. Error codes and messages are listed below.
579    .P
580    If the final argument, \fItableptr\fP, is NULL, PCRE uses a default set of
581    character tables that are built when PCRE is compiled, using the default C
582    locale. Otherwise, \fItableptr\fP must be an address that is the result of a
583    call to \fBpcre_maketables()\fP. This value is stored with the compiled
584    pattern, and used again by \fBpcre_exec()\fP, unless another table pointer is
585    passed to it. For more discussion, see the section on locale support below.
586    .P
587    This code fragment shows a typical straightforward call to \fBpcre_compile()\fP:
588    .sp
589    pcre *re;    pcre *re;
590    const char *error;    const char *error;
591    int erroffset;    int erroffset;
# Line 265  This code fragment shows a typical strai Line 595  This code fragment shows a typical strai
595      &error,           /* for error message */      &error,           /* for error message */
596      &erroffset,       /* for error offset */      &erroffset,       /* for error offset */
597      NULL);            /* use default character tables */      NULL);            /* use default character tables */
598    .sp
599  The following option bits are defined:  The following names for option bits are defined in the \fBpcre.h\fP header
600    file:
601    .sp
602    PCRE_ANCHORED    PCRE_ANCHORED
603    .sp
604  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
605  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
606  being searched (the "subject string"). This effect can also be achieved by  being searched (the "subject string"). This effect can also be achieved by
607  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
608  Perl.  Perl.
609    .sp
610      PCRE_AUTO_CALLOUT
611    .sp
612    If this bit is set, \fBpcre_compile()\fP automatically inserts callout items,
613    all with number 255, before each pattern item. For discussion of the callout
614    facility, see the
615    .\" HREF
616    \fBpcrecallout\fP
617    .\"
618    documentation.
619    .sp
620      PCRE_BSR_ANYCRLF
621      PCRE_BSR_UNICODE
622    .sp
623    These options (which are mutually exclusive) control what the \eR escape
624    sequence matches. The choice is either to match only CR, LF, or CRLF, or to
625    match any Unicode newline sequence. The default is specified when PCRE is
626    built. It can be overridden from within the pattern, or by setting an option
627    when a compiled pattern is matched.
628    .sp
629    PCRE_CASELESS    PCRE_CASELESS
630    .sp
631  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
632  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
633  pattern by a (?i) option setting.  pattern by a (?i) option setting. In UTF-8 mode, PCRE always understands the
634    concept of case for characters whose values are less than 128, so caseless
635    matching is always possible. For characters with higher values, the concept of
636    case is supported if PCRE is compiled with Unicode property support, but not
637    otherwise. If you want to use caseless matching for characters 128 and above,
638    you must ensure that PCRE is compiled with Unicode property support as well as
639    with UTF-8 support.
640    .sp
641    PCRE_DOLLAR_ENDONLY    PCRE_DOLLAR_ENDONLY
642    .sp
643  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
644  end of the subject string. Without this option, a dollar also matches  end of the subject string. Without this option, a dollar also matches
645  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
646  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.
647  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
648  a pattern.  pattern.
649    .sp
650    PCRE_DOTALL    PCRE_DOTALL
651    .sp
652  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
653  including newlines. Without it, newlines are excluded. This option is  any value, including one that indicates a newline. However, it only ever
654    matches one character, even if newlines are coded as CRLF. Without this option,
655    a dot does not match when the current position is at a newline. This option is
656  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
657  (?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
658  character, independent of the setting of this option.  characters, independent of the setting of this option.
659    .sp
660      PCRE_DUPNAMES
661    .sp
662    If this bit is set, names used to identify capturing subpatterns need not be
663    unique. This can be helpful for certain types of pattern when it is known that
664    only one instance of the named subpattern can ever be matched. There are more
665    details of named subpatterns below; see also the
666    .\" HREF
667    \fBpcrepattern\fP
668    .\"
669    documentation.
670    .sp
671    PCRE_EXTENDED    PCRE_EXTENDED
672    .sp
673  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
674  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
675  include the VT character (code 11). In addition, characters between an  include the VT character (code 11). In addition, characters between an
676  unescaped # outside a character class and the next newline character,  unescaped # outside a character class and the next newline, inclusive, are also
677  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
678  be changed within a pattern by a (?x) option setting.  pattern by a (?x) option setting.
679    .P
680    Which characters are interpreted as newlines is controlled by the options
681    passed to \fBpcre_compile()\fP or by a special sequence at the start of the
682    pattern, as described in the section entitled
683    .\" HTML <a href="pcrepattern.html#newlines">
684    .\" </a>
685    "Newline conventions"
686    .\"
687    in the \fBpcrepattern\fP documentation. Note that the end of this type of
688    comment is a literal newline sequence in the pattern; escape sequences that
689    happen to represent a newline do not count.
690    .P
691  This option makes it possible to include comments inside complicated patterns.  This option makes it possible to include comments inside complicated patterns.
692  Note, however, that this applies only to data characters. Whitespace characters  Note, however, that this applies only to data characters. White space characters
693  may never appear within special character sequences in a pattern, for example  may never appear within special character sequences in a pattern, for example
694  within the sequence (?( which introduces a conditional subpattern.  within the sequence (?( that introduces a conditional subpattern.
695    .sp
696    PCRE_EXTRA    PCRE_EXTRA
697    .sp
698  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
699  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
700  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
701  special meaning causes an error, thus reserving these combinations for future  special meaning causes an error, thus reserving these combinations for future
702  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
703  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
704  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
705  pattern.  no other features controlled by this option. It can also be set by a (?X)
706    option setting within a pattern.
707    .sp
708      PCRE_FIRSTLINE
709    .sp
710    If this option is set, an unanchored pattern is required to match before or at
711    the first newline in the subject string, though the matched text may continue
712    over the newline.
713    .sp
714      PCRE_JAVASCRIPT_COMPAT
715    .sp
716    If this option is set, PCRE's behaviour is changed in some ways so that it is
717    compatible with JavaScript rather than Perl. The changes are as follows:
718    .P
719    (1) A lone closing square bracket in a pattern causes a compile-time error,
720    because this is illegal in JavaScript (by default it is treated as a data
721    character). Thus, the pattern AB]CD becomes illegal when this option is set.
722    .P
723    (2) At run time, a back reference to an unset subpattern group matches an empty
724    string (by default this causes the current matching alternative to fail). A
725    pattern such as (\e1)(a) succeeds when this option is set (assuming it can find
726    an "a" in the subject), whereas it fails by default, for Perl compatibility.
727    .P
728    (3) \eU matches an upper case "U" character; by default \eU causes a compile
729    time error (Perl uses \eU to upper case subsequent characters).
730    .P
731    (4) \eu matches a lower case "u" character unless it is followed by four
732    hexadecimal digits, in which case the hexadecimal number defines the code point
733    to match. By default, \eu causes a compile time error (Perl uses it to upper
734    case the following character).
735    .P
736    (5) \ex matches a lower case "x" character unless it is followed by two
737    hexadecimal digits, in which case the hexadecimal number defines the code point
738    to match. By default, as in Perl, a hexadecimal number is always expected after
739    \ex, but it may have zero, one, or two digits (so, for example, \exz matches a
740    binary zero character followed by z).
741    .sp
742    PCRE_MULTILINE    PCRE_MULTILINE
743    .sp
744  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
745  characters (even if it actually contains several newlines). The "start of line"  characters (even if it actually contains newlines). The "start of line"
746  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
747  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
748  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
749  Perl.  Perl.
750    .P
751  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
752  match immediately following or immediately before any newline in the subject  match immediately following or immediately before internal newlines in the
753  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
754  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
755  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
756  occurrences of ^ or $ in a pattern, setting PCRE_MULTILINE has no effect.  occurrences of ^ or $ in a pattern, setting PCRE_MULTILINE has no effect.
757    .sp
758      PCRE_NEWLINE_CR
759      PCRE_NEWLINE_LF
760      PCRE_NEWLINE_CRLF
761      PCRE_NEWLINE_ANYCRLF
762      PCRE_NEWLINE_ANY
763    .sp
764    These options override the default newline definition that was chosen when PCRE
765    was built. Setting the first or the second specifies that a newline is
766    indicated by a single character (CR or LF, respectively). Setting
767    PCRE_NEWLINE_CRLF specifies that a newline is indicated by the two-character
768    CRLF sequence. Setting PCRE_NEWLINE_ANYCRLF specifies that any of the three
769    preceding sequences should be recognized. Setting PCRE_NEWLINE_ANY specifies
770    that any Unicode newline sequence should be recognized.
771    .P
772    In an ASCII/Unicode environment, the Unicode newline sequences are the three
773    just mentioned, plus the single characters VT (vertical tab, U+000B), FF (form
774    feed, U+000C), NEL (next line, U+0085), LS (line separator, U+2028), and PS
775    (paragraph separator, U+2029). For the 8-bit library, the last two are
776    recognized only in UTF-8 mode.
777    .P
778    When PCRE is compiled to run in an EBCDIC (mainframe) environment, the code for
779    CR is 0x0d, the same as ASCII. However, the character code for LF is normally
780    0x15, though in some EBCDIC environments 0x25 is used. Whichever of these is
781    not LF is made to correspond to Unicode's NEL character. EBCDIC codes are all
782    less than 256. For more details, see the
783    .\" HREF
784    \fBpcrebuild\fP
785    .\"
786    documentation.
787    .P
788    The newline setting in the options word uses three bits that are treated
789    as a number, giving eight possibilities. Currently only six are used (default
790    plus the five values above). This means that if you set more than one newline
791    option, the combination may or may not be sensible. For example,
792    PCRE_NEWLINE_CR with PCRE_NEWLINE_LF is equivalent to PCRE_NEWLINE_CRLF, but
793    other combinations may yield unused numbers and cause an error.
794    .P
795    The only time that a line break in a pattern is specially recognized when
796    compiling is when PCRE_EXTENDED is set. CR and LF are white space characters,
797    and so are ignored in this mode. Also, an unescaped # outside a character class
798    indicates a comment that lasts until after the next line break sequence. In
799    other circumstances, line break sequences in patterns are treated as literal
800    data.
801    .P
802    The newline option that is set at compile time becomes the default that is used
803    for \fBpcre_exec()\fP and \fBpcre_dfa_exec()\fP, but it can be overridden.
804    .sp
805    PCRE_NO_AUTO_CAPTURE    PCRE_NO_AUTO_CAPTURE
806    .sp
807  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
808  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
809  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
810  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
811  in Perl.  in Perl.
812    .sp
813      NO_START_OPTIMIZE
814    .sp
815    This is an option that acts at matching time; that is, it is really an option
816    for \fBpcre_exec()\fP or \fBpcre_dfa_exec()\fP. If it is set at compile time,
817    it is remembered with the compiled pattern and assumed at matching time. For
818    details see the discussion of PCRE_NO_START_OPTIMIZE
819    .\" HTML <a href="#execoptions">
820    .\" </a>
821    below.
822    .\"
823    .sp
824      PCRE_UCP
825    .sp
826    This option changes the way PCRE processes \eB, \eb, \eD, \ed, \eS, \es, \eW,
827    \ew, and some of the POSIX character classes. By default, only ASCII characters
828    are recognized, but if PCRE_UCP is set, Unicode properties are used instead to
829    classify characters. More details are given in the section on
830    .\" HTML <a href="pcre.html#genericchartypes">
831    .\" </a>
832    generic character types
833    .\"
834    in the
835    .\" HREF
836    \fBpcrepattern\fP
837    .\"
838    page. If you set PCRE_UCP, matching one of the items it affects takes much
839    longer. The option is available only if PCRE has been compiled with Unicode
840    property support.
841    .sp
842    PCRE_UNGREEDY    PCRE_UNGREEDY
843    .sp
844  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
845  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
846  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.
847    .sp
848    PCRE_UTF8    PCRE_UTF8
849    .sp
850  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
851  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
852  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
853  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
854  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  
855  .\" HREF  .\" HREF
856  \fBpcre\fR  \fBpcreunicode\fP
857  .\"  .\"
858  page.  page.
859    .sp
860    PCRE_NO_UTF8_CHECK    PCRE_NO_UTF8_CHECK
861    .sp
862  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 string is
863  automatically checked. If an invalid UTF-8 sequence of bytes is found,  automatically checked. There is a discussion about the
864  \fBpcre_compile()\fR returns an error. If you already know that your pattern is  .\" HTML <a href="pcreunicode.html#utf8strings">
865  valid, and you want to skip this check for performance reasons, you can set the  .\" </a>
866  PCRE_NO_UTF8_CHECK option. When it is set, the effect of passing an invalid  validity of UTF-8 strings
867  UTF-8 string as a pattern is undefined. It may cause your program to crash.  .\"
868  Note that there is a similar option for suppressing the checking of subject  in the
869  strings passed to \fBpcre_exec()\fR.  .\" HREF
870    \fBpcreunicode\fP
871    .\"
872  .SH STUDYING A PATTERN  page. If an invalid UTF-8 sequence is found, \fBpcre_compile()\fP returns an
873  .rs  error. If you already know that your pattern is valid, and you want to skip
874  .sp  this check for performance reasons, you can set the PCRE_NO_UTF8_CHECK option.
875  .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
876  .ti +5n  undefined. It may cause your program to crash. Note that this option can also
877  .B const char **\fIerrptr\fR);  be passed to \fBpcre_exec()\fP and \fBpcre_dfa_exec()\fP, to suppress the
878  .PP  validity checking of subject strings only. If the same string is being matched
879  When a pattern is going to be used several times, it is worth spending more  many times, the option can be safely set for the second and subsequent
880  time analyzing it in order to speed up the time taken for matching. The  matchings to improve performance.
881  function \fBpcre_study()\fR takes a pointer to a compiled pattern as its first  .
882  argument. If studing the pattern produces additional information that will help  .
883  speed up matching, \fBpcre_study()\fR returns a pointer to a \fBpcre_extra\fR  .SH "COMPILATION ERROR CODES"
884  block, in which the \fIstudy_data\fR field points to the results of the study.  .rs
885    .sp
886  The returned value from a \fBpcre_study()\fR can be passed directly to  The following table lists the error codes than may be returned by
887  \fBpcre_exec()\fR. However, the \fBpcre_extra\fR block also contains other  \fBpcre_compile2()\fP, along with the error messages that may be returned by
888  fields that can be set by the caller before the block is passed; these are  both compiling functions. Note that error messages are always 8-bit ASCII
889  described below. If studying the pattern does not produce any additional  strings, even in 16-bit or 32-bit mode. As PCRE has developed, some error codes
890  information, \fBpcre_study()\fR returns NULL. In that circumstance, if the  have fallen out of use. To avoid confusion, they have not been re-used.
891  calling program wants to pass some of the other fields to \fBpcre_exec()\fR, it  .sp
892  must set up its own \fBpcre_extra\fR block.     0  no error
893       1  \e at end of pattern
894  The second argument contains option bits. At present, no options are defined     2  \ec at end of pattern
895  for \fBpcre_study()\fR, and this argument should always be zero.     3  unrecognized character follows \e
896       4  numbers out of order in {} quantifier
897  The third argument for \fBpcre_study()\fR is a pointer for an error message. If     5  number too big in {} quantifier
898       6  missing terminating ] for character class
899       7  invalid escape sequence in character class
900       8  range out of order in character class
901       9  nothing to repeat
902      10  [this code is not in use]
903      11  internal error: unexpected repeat
904      12  unrecognized character after (? or (?-
905      13  POSIX named classes are supported only within a class
906      14  missing )
907      15  reference to non-existent subpattern
908      16  erroffset passed as NULL
909      17  unknown option bit(s) set
910      18  missing ) after comment
911      19  [this code is not in use]
912      20  regular expression is too large
913      21  failed to get memory
914      22  unmatched parentheses
915      23  internal error: code overflow
916      24  unrecognized character after (?<
917      25  lookbehind assertion is not fixed length
918      26  malformed number or name after (?(
919      27  conditional group contains more than two branches
920      28  assertion expected after (?(
921      29  (?R or (?[+-]digits must be followed by )
922      30  unknown POSIX class name
923      31  POSIX collating elements are not supported
924      32  this version of PCRE is compiled without UTF support
925      33  [this code is not in use]
926      34  character value in \ex{...} sequence is too large
927      35  invalid condition (?(0)
928      36  \eC not allowed in lookbehind assertion
929      37  PCRE does not support \eL, \el, \eN{name}, \eU, or \eu
930      38  number after (?C is > 255
931      39  closing ) for (?C expected
932      40  recursive call could loop indefinitely
933      41  unrecognized character after (?P
934      42  syntax error in subpattern name (missing terminator)
935      43  two named subpatterns have the same name
936      44  invalid UTF-8 string (specifically UTF-8)
937      45  support for \eP, \ep, and \eX has not been compiled
938      46  malformed \eP or \ep sequence
939      47  unknown property name after \eP or \ep
940      48  subpattern name is too long (maximum 32 characters)
941      49  too many named subpatterns (maximum 10000)
942      50  [this code is not in use]
943      51  octal value is greater than \e377 in 8-bit non-UTF-8 mode
944      52  internal error: overran compiling workspace
945      53  internal error: previously-checked referenced subpattern
946            not found
947      54  DEFINE group contains more than one branch
948      55  repeating a DEFINE group is not allowed
949      56  inconsistent NEWLINE options
950      57  \eg is not followed by a braced, angle-bracketed, or quoted
951            name/number or by a plain number
952      58  a numbered reference must not be zero
953      59  an argument is not allowed for (*ACCEPT), (*FAIL), or (*COMMIT)
954      60  (*VERB) not recognized
955      61  number is too big
956      62  subpattern name expected
957      63  digit expected after (?+
958      64  ] is an invalid data character in JavaScript compatibility mode
959      65  different names for subpatterns of the same number are
960            not allowed
961      66  (*MARK) must have an argument
962      67  this version of PCRE is not compiled with Unicode property
963            support
964      68  \ec must be followed by an ASCII character
965      69  \ek is not followed by a braced, angle-bracketed, or quoted name
966      70  internal error: unknown opcode in find_fixedlength()
967      71  \eN is not supported in a class
968      72  too many forward references
969      73  disallowed Unicode code point (>= 0xd800 && <= 0xdfff)
970      74  invalid UTF-16 string (specifically UTF-16)
971      75  name is too long in (*MARK), (*PRUNE), (*SKIP), or (*THEN)
972      76  character value in \eu.... sequence is too large
973      77  invalid UTF-32 string (specifically UTF-32)
974    .sp
975    The numbers 32 and 10000 in errors 48 and 49 are defaults; different values may
976    be used if the limits were changed when PCRE was built.
977    .
978    .
979    .\" HTML <a name="studyingapattern"></a>
980    .SH "STUDYING A PATTERN"
981    .rs
982    .sp
983    .B pcre_extra *pcre_study(const pcre *\fIcode\fP, int \fIoptions\fP
984    .ti +5n
985    .B const char **\fIerrptr\fP);
986    .PP
987    If a compiled pattern is going to be used several times, it is worth spending
988    more time analyzing it in order to speed up the time taken for matching. The
989    function \fBpcre_study()\fP takes a pointer to a compiled pattern as its first
990    argument. If studying the pattern produces additional information that will
991    help speed up matching, \fBpcre_study()\fP returns a pointer to a
992    \fBpcre_extra\fP block, in which the \fIstudy_data\fP field points to the
993    results of the study.
994    .P
995    The returned value from \fBpcre_study()\fP can be passed directly to
996    \fBpcre_exec()\fP or \fBpcre_dfa_exec()\fP. However, a \fBpcre_extra\fP block
997    also contains other fields that can be set by the caller before the block is
998    passed; these are described
999    .\" HTML <a href="#extradata">
1000    .\" </a>
1001    below
1002    .\"
1003    in the section on matching a pattern.
1004    .P
1005    If studying the pattern does not produce any useful information,
1006    \fBpcre_study()\fP returns NULL by default. In that circumstance, if the
1007    calling program wants to pass any of the other fields to \fBpcre_exec()\fP or
1008    \fBpcre_dfa_exec()\fP, it must set up its own \fBpcre_extra\fP block. However,
1009    if \fBpcre_study()\fP is called with the PCRE_STUDY_EXTRA_NEEDED option, it
1010    returns a \fBpcre_extra\fP block even if studying did not find any additional
1011    information. It may still return NULL, however, if an error occurs in
1012    \fBpcre_study()\fP.
1013    .P
1014    The second argument of \fBpcre_study()\fP contains option bits. There are three
1015    further options in addition to PCRE_STUDY_EXTRA_NEEDED:
1016    .sp
1017      PCRE_STUDY_JIT_COMPILE
1018      PCRE_STUDY_JIT_PARTIAL_HARD_COMPILE
1019      PCRE_STUDY_JIT_PARTIAL_SOFT_COMPILE
1020    .sp
1021    If any of these are set, and the just-in-time compiler is available, the
1022    pattern is further compiled into machine code that executes much faster than
1023    the \fBpcre_exec()\fP interpretive matching function. If the just-in-time
1024    compiler is not available, these options are ignored. All undefined bits in the
1025    \fIoptions\fP argument must be zero.
1026    .P
1027    JIT compilation is a heavyweight optimization. It can take some time for
1028    patterns to be analyzed, and for one-off matches and simple patterns the
1029    benefit of faster execution might be offset by a much slower study time.
1030    Not all patterns can be optimized by the JIT compiler. For those that cannot be
1031    handled, matching automatically falls back to the \fBpcre_exec()\fP
1032    interpreter. For more details, see the
1033    .\" HREF
1034    \fBpcrejit\fP
1035    .\"
1036    documentation.
1037    .P
1038    The third argument for \fBpcre_study()\fP is a pointer for an error message. If
1039  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
1040  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
1041  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
1042  be sure that it has run successfully.  should test the error pointer for NULL after calling \fBpcre_study()\fP, to be
1043    sure that it has run successfully.
1044  This is a typical call to \fBpcre_study\fR():  .P
1045    When you are finished with a pattern, you can free the memory used for the
1046    pcre_extra *pe;  study data by calling \fBpcre_free_study()\fP. This function was added to the
1047    pe = pcre_study(  API for release 8.20. For earlier versions, the memory could be freed with
1048    \fBpcre_free()\fP, just like the pattern itself. This will still work in cases
1049    where JIT optimization is not used, but it is advisable to change to the new
1050    function when convenient.
1051    .P
1052    This is a typical way in which \fBpcre_study\fP() is used (except that in a
1053    real application there should be tests for errors):
1054    .sp
1055      int rc;
1056      pcre *re;
1057      pcre_extra *sd;
1058      re = pcre_compile("pattern", 0, &error, &erroroffset, NULL);
1059      sd = pcre_study(
1060      re,             /* result of pcre_compile() */      re,             /* result of pcre_compile() */
1061      0,              /* no options exist */      0,              /* no options */
1062      &error);        /* set to NULL or points to a message */      &error);        /* set to NULL or points to a message */
1063      rc = pcre_exec(   /* see below for details of pcre_exec() options */
1064  At present, studying a pattern is useful only for non-anchored patterns that do      re, sd, "subject", 7, 0, 0, ovector, 30);
1065  not have a single fixed starting character. A bitmap of possible starting    ...
1066  characters is created.    pcre_free_study(sd);
1067      pcre_free(re);
1068    .sp
1069    Studying a pattern does two things: first, a lower bound for the length of
1070    subject string that is needed to match the pattern is computed. This does not
1071    mean that there are any strings of that length that match, but it does
1072    guarantee that no shorter strings match. The value is used to avoid wasting
1073    time by trying to match strings that are shorter than the lower bound. You can
1074    find out the value in a calling program via the \fBpcre_fullinfo()\fP function.
1075    .P
1076    Studying a pattern is also useful for non-anchored patterns that do not have a
1077    single fixed starting character. A bitmap of possible starting bytes is
1078    created. This speeds up finding a position in the subject at which to start
1079    matching. (In 16-bit mode, the bitmap is used for 16-bit values less than 256.
1080    In 32-bit mode, the bitmap is used for 32-bit values less than 256.)
1081    .P
1082    These two optimizations apply to both \fBpcre_exec()\fP and
1083    \fBpcre_dfa_exec()\fP, and the information is also used by the JIT compiler.
1084    The optimizations can be disabled by setting the PCRE_NO_START_OPTIMIZE option
1085    when calling \fBpcre_exec()\fP or \fBpcre_dfa_exec()\fP, but if this is done,
1086    JIT execution is also disabled. You might want to do this if your pattern
1087    contains callouts or (*MARK) and you want to make use of these facilities in
1088    cases where matching fails. See the discussion of PCRE_NO_START_OPTIMIZE
1089    .\" HTML <a href="#execoptions">
1090    .\" </a>
1091    below.
1092    .\"
1093    .
1094    .
1095  .\" HTML <a name="localesupport"></a>  .\" HTML <a name="localesupport"></a>
1096  .SH LOCALE SUPPORT  .SH "LOCALE SUPPORT"
1097  .rs  .rs
1098  .sp  .sp
1099  PCRE handles caseless matching, and determines whether characters are letters,  PCRE handles caseless matching, and determines whether characters are letters,
1100  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
1101  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
1102  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
1103  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
1104  is NULL, and is sufficient for many applications.  Unicode character property support. Alternatively, the PCRE_UCP option can be
1105    set at compile time; this causes \ew and friends to use Unicode property
1106  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
1107  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
1108  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
1109  as necessary. For example, to build and use tables that are appropriate for the  two.
1110  French locale (where accented characters with codes greater than 128 are  .P
1111  treated as letters), the following code could be used:  PCRE contains an internal set of tables that are used when the final argument
1112    of \fBpcre_compile()\fP is NULL. These are sufficient for many applications.
1113    setlocale(LC_CTYPE, "fr");  Normally, the internal tables recognize only ASCII characters. However, when
1114    PCRE is built, it is possible to cause the internal tables to be rebuilt in the
1115    default "C" locale of the local system, which may cause them to be different.
1116    .P
1117    The internal tables can always be overridden by tables supplied by the
1118    application that calls PCRE. These may be created in a different locale from
1119    the default. As more and more applications change to using Unicode, the need
1120    for this locale support is expected to die away.
1121    .P
1122    External tables are built by calling the \fBpcre_maketables()\fP function,
1123    which has no arguments, in the relevant locale. The result can then be passed
1124    to \fBpcre_compile()\fP or \fBpcre_exec()\fP as often as necessary. For
1125    example, to build and use tables that are appropriate for the French locale
1126    (where accented characters with values greater than 128 are treated as letters),
1127    the following code could be used:
1128    .sp
1129      setlocale(LC_CTYPE, "fr_FR");
1130    tables = pcre_maketables();    tables = pcre_maketables();
1131    re = pcre_compile(..., tables);    re = pcre_compile(..., tables);
1132    .sp
1133  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
1134  pointer that is passed to \fBpcre_compile\fR is saved with the compiled  are using Windows, the name for the French locale is "french".
1135  pattern, and the same tables are used via this pointer by \fBpcre_study()\fR  .P
1136  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
1137  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
1138  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
1139  memory containing the tables remains available for as long as it is needed.  needed.
1140    .P
1141  .SH INFORMATION ABOUT A PATTERN  The pointer that is passed to \fBpcre_compile()\fP is saved with the compiled
1142  .rs  pattern, and the same tables are used via this pointer by \fBpcre_study()\fP
1143  .sp  and normally also by \fBpcre_exec()\fP. Thus, by default, for any single
1144  .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
1145  .ti +5n  different patterns can be compiled in different locales.
1146  .B int \fIwhat\fR, void *\fIwhere\fR);  .P
1147  .PP  It is possible to pass a table pointer or NULL (indicating the use of the
1148  The \fBpcre_fullinfo()\fR function returns information about a compiled  internal tables) to \fBpcre_exec()\fP. Although not intended for this purpose,
1149  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
1150  nevertheless retained for backwards compability (and is documented below).  one in which it was compiled. Passing table pointers at run time is discussed
1151    below in the section on matching a pattern.
1152  The first argument for \fBpcre_fullinfo()\fR is a pointer to the compiled  .
1153  pattern. The second argument is the result of \fBpcre_study()\fR, or NULL if  .
1154    .\" HTML <a name="infoaboutpattern"></a>
1155    .SH "INFORMATION ABOUT A PATTERN"
1156    .rs
1157    .sp
1158    .B int pcre_fullinfo(const pcre *\fIcode\fP, "const pcre_extra *\fIextra\fP,"
1159    .ti +5n
1160    .B int \fIwhat\fP, void *\fIwhere\fP);
1161    .PP
1162    The \fBpcre_fullinfo()\fP function returns information about a compiled
1163    pattern. It replaces the \fBpcre_info()\fP function, which was removed from the
1164    library at version 8.30, after more than 10 years of obsolescence.
1165    .P
1166    The first argument for \fBpcre_fullinfo()\fP is a pointer to the compiled
1167    pattern. The second argument is the result of \fBpcre_study()\fP, or NULL if
1168  the pattern was not studied. The third argument specifies which piece of  the pattern was not studied. The third argument specifies which piece of
1169  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
1170  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
1171  the following negative numbers:  the following negative numbers:
1172    .sp
1173    PCRE_ERROR_NULL       the argument \fIcode\fR was NULL    PCRE_ERROR_NULL           the argument \fIcode\fP was NULL
1174                          the argument \fIwhere\fR was NULL                              the argument \fIwhere\fP was NULL
1175    PCRE_ERROR_BADMAGIC   the "magic number" was not found    PCRE_ERROR_BADMAGIC       the "magic number" was not found
1176    PCRE_ERROR_BADOPTION  the value of \fIwhat\fR was invalid    PCRE_ERROR_BADENDIANNESS  the pattern was compiled with different
1177                                endianness
1178  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
1179  compiled pattern:  .sp
1180    The "magic number" is placed at the start of each compiled pattern as an simple
1181    check against passing an arbitrary memory pointer. The endianness error can
1182    occur if a compiled pattern is saved and reloaded on a different host. Here is
1183    a typical call of \fBpcre_fullinfo()\fP, to obtain the length of the compiled
1184    pattern:
1185    .sp
1186    int rc;    int rc;
1187    unsigned long int length;    size_t length;
1188    rc = pcre_fullinfo(    rc = pcre_fullinfo(
1189      re,               /* result of pcre_compile() */      re,               /* result of pcre_compile() */
1190      pe,               /* result of pcre_study(), or NULL */      sd,               /* result of pcre_study(), or NULL */
1191      PCRE_INFO_SIZE,   /* what is required */      PCRE_INFO_SIZE,   /* what is required */
1192      &length);         /* where to put the data */      &length);         /* where to put the data */
1193    .sp
1194  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
1195  as follows:  as follows:
1196    .sp
1197    PCRE_INFO_BACKREFMAX    PCRE_INFO_BACKREFMAX
1198    .sp
1199  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
1200  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
1201  no back references.  no back references.
1202    .sp
1203    PCRE_INFO_CAPTURECOUNT    PCRE_INFO_CAPTURECOUNT
1204    .sp
1205  Return the number of capturing subpatterns in the pattern. The fourth argument  Return the number of capturing subpatterns in the pattern. The fourth argument
1206  should point to an \fbint\fR variable.  should point to an \fBint\fP variable.
1207    .sp
1208      PCRE_INFO_DEFAULT_TABLES
1209    .sp
1210    Return a pointer to the internal default character tables within PCRE. The
1211    fourth argument should point to an \fBunsigned char *\fP variable. This
1212    information call is provided for internal use by the \fBpcre_study()\fP
1213    function. External callers can cause PCRE to use its internal tables by passing
1214    a NULL table pointer.
1215    .sp
1216    PCRE_INFO_FIRSTBYTE    PCRE_INFO_FIRSTBYTE
1217    .sp
1218  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
1219  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,
1220  old name is still recognized for backwards compatibility.)  where data units are bytes.) The fourth argument should point to an \fBint\fP
1221    variable.
1222  If there is a fixed first byte, e.g. from a pattern such as (cat|cow|coyote),  .P
1223  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
1224    such as (cat|cow|coyote), its value is returned. In the 8-bit library, the
1225    value is always less than 256. In the 16-bit library the value can be up to
1226    0xffff. In the 32-bit library the value can be up to 0x10ffff.
1227    .P
1228    If there is no fixed first value, and if either
1229    .sp
1230  (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
1231  starts with "^", or  starts with "^", or
1232    .sp
1233  (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
1234  (if it were set, the pattern would be anchored),  (if it were set, the pattern would be anchored),
1235    .sp
1236  -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
1237  subject string or after any newline within the string. Otherwise -2 is  subject string or after any newline within the string. Otherwise -2 is
1238  returned. For anchored patterns, -2 is returned.  returned. For anchored patterns, -2 is returned.
1239    .P
1240    Since for the 32-bit library using the non-UTF-32 mode, this function is unable
1241    to return the full 32-bit range of the character, this value is deprecated;
1242    instead the PCRE_INFO_FIRSTCHARACTERFLAGS and PCRE_INFO_FIRSTCHARACTER values
1243    should be used.
1244    .sp
1245    PCRE_INFO_FIRSTTABLE    PCRE_INFO_FIRSTTABLE
1246    .sp
1247  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
1248  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
1249  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
1250  fourth argument should point to an \fBunsigned char *\fR variable.  fourth argument should point to an \fBunsigned char *\fP variable.
1251    .sp
1252      PCRE_INFO_HASCRORLF
1253    .sp
1254    Return 1 if the pattern contains any explicit matches for CR or LF characters,
1255    otherwise 0. The fourth argument should point to an \fBint\fP variable. An
1256    explicit match is either a literal CR or LF character, or \er or \en.
1257    .sp
1258      PCRE_INFO_JCHANGED
1259    .sp
1260    Return 1 if the (?J) or (?-J) option setting is used in the pattern, otherwise
1261    0. The fourth argument should point to an \fBint\fP variable. (?J) and
1262    (?-J) set and unset the local PCRE_DUPNAMES option, respectively.
1263    .sp
1264      PCRE_INFO_JIT
1265    .sp
1266    Return 1 if the pattern was studied with one of the JIT options, and
1267    just-in-time compiling was successful. The fourth argument should point to an
1268    \fBint\fP variable. A return value of 0 means that JIT support is not available
1269    in this version of PCRE, or that the pattern was not studied with a JIT option,
1270    or that the JIT compiler could not handle this particular pattern. See the
1271    .\" HREF
1272    \fBpcrejit\fP
1273    .\"
1274    documentation for details of what can and cannot be handled.
1275    .sp
1276      PCRE_INFO_JITSIZE
1277    .sp
1278    If the pattern was successfully studied with a JIT option, return the size of
1279    the JIT compiled code, otherwise return zero. The fourth argument should point
1280    to a \fBsize_t\fP variable.
1281    .sp
1282    PCRE_INFO_LASTLITERAL    PCRE_INFO_LASTLITERAL
1283    .sp
1284  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
1285  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
1286  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
1287  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
1288  follows something of variable length. For example, for the pattern  only if it follows something of variable length. For example, for the pattern
1289  /^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
1290  is -1.  is -1.
1291    .P
1292    Since for the 32-bit library using the non-UTF-32 mode, this function is unable
1293    to return the full 32-bit range of the character, this value is deprecated;
1294    instead the PCRE_INFO_REQUIREDCHARFLAGS and PCRE_INFO_REQUIREDCHAR values should
1295    be used.
1296    .sp
1297      PCRE_INFO_MAXLOOKBEHIND
1298    .sp
1299    Return the number of characters (NB not bytes) in the longest lookbehind
1300    assertion in the pattern. Note that the simple assertions \eb and \eB require a
1301    one-character lookbehind. This information is useful when doing multi-segment
1302    matching using the partial matching facilities.
1303    .sp
1304      PCRE_INFO_MINLENGTH
1305    .sp
1306    If the pattern was studied and a minimum length for matching subject strings
1307    was computed, its value is returned. Otherwise the returned value is -1. The
1308    value is a number of characters, which in UTF-8 mode may be different from the
1309    number of bytes. The fourth argument should point to an \fBint\fP variable. A
1310    non-negative value is a lower bound to the length of any matching string. There
1311    may not be any strings of that length that do actually match, but every string
1312    that does match is at least that long.
1313    .sp
1314    PCRE_INFO_NAMECOUNT    PCRE_INFO_NAMECOUNT
1315    PCRE_INFO_NAMEENTRYSIZE    PCRE_INFO_NAMEENTRYSIZE
1316    PCRE_INFO_NAMETABLE    PCRE_INFO_NAMETABLE
1317    .sp
1318  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
1319  names are just an additional way of identifying the parentheses, which still  names are just an additional way of identifying the parentheses, which still
1320  acquire a number. A caller that wants to extract data from a named subpattern  acquire numbers. Several convenience functions such as
1321  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
1322  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
1323  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
1324  table for the pattern.  output vector (described with \fBpcre_exec()\fP below). To do the conversion,
1325    you need to use the name-to-number map, which is described by these three
1326    values.
1327    .P
1328  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
1329  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
1330  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
1331  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
1332  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
1333  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,
1334  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
1335  alphabetical order. For example, consider the following pattern (assume  16-bit data units, the first of which contains the parenthesis number.
1336  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
1337    which contains the parenthesis number. The rest
1338    (?P<date> (?P<year>(\\d\\d)?\\d\\d) -  of the entry is the corresponding name, zero terminated.
1339    (?P<month>\\d\\d) - (?P<day>\\d\\d) )  .P
1340    The names are in alphabetical order. Duplicate names may appear if (?| is used
1341    to create multiple groups with the same number, as described in the
1342    .\" HTML <a href="pcrepattern.html#dupsubpatternnumber">
1343    .\" </a>
1344    section on duplicate subpattern numbers
1345    .\"
1346    in the
1347    .\" HREF
1348    \fBpcrepattern\fP
1349    .\"
1350    page. Duplicate names for subpatterns with different numbers are permitted only
1351    if PCRE_DUPNAMES is set. In all cases of duplicate names, they appear in the
1352    table in the order in which they were found in the pattern. In the absence of
1353    (?| this is the order of increasing number; when (?| is used this is not
1354    necessarily the case because later subpatterns may have lower numbers.
1355    .P
1356    As a simple example of the name/number table, consider the following pattern
1357    after compilation by the 8-bit library (assume PCRE_EXTENDED is set, so white
1358    space - including newlines - is ignored):
1359    .sp
1360    .\" JOIN
1361      (?<date> (?<year>(\ed\ed)?\ed\ed) -
1362      (?<month>\ed\ed) - (?<day>\ed\ed) )
1363    .sp
1364  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
1365  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
1366  bytes shows in hex, and undefined bytes shown as ??:  bytes shows in hexadecimal, and undefined bytes shown as ??:
1367    .sp
1368    00 01 d  a  t  e  00 ??    00 01 d  a  t  e  00 ??
1369    00 05 d  a  y  00 ?? ??    00 05 d  a  y  00 ?? ??
1370    00 04 m  o  n  t  h  00    00 04 m  o  n  t  h  00
1371    00 02 y  e  a  r  00 ??    00 02 y  e  a  r  00 ??
1372    .sp
1373  When writing code to extract data from named subpatterns, remember that the  When writing code to extract data from named subpatterns using the
1374  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
1375    different for each compiled pattern.
1376    .sp
1377      PCRE_INFO_OKPARTIAL
1378    .sp
1379    Return 1 if the pattern can be used for partial matching with
1380    \fBpcre_exec()\fP, otherwise 0. The fourth argument should point to an
1381    \fBint\fP variable. From release 8.00, this always returns 1, because the
1382    restrictions that previously applied to partial matching have been lifted. The
1383    .\" HREF
1384    \fBpcrepartial\fP
1385    .\"
1386    documentation gives details of partial matching.
1387    .sp
1388    PCRE_INFO_OPTIONS    PCRE_INFO_OPTIONS
1389    .sp
1390  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
1391  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
1392  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
1393  top-level option settings within the pattern itself.  top-level option settings at the start of the pattern itself. In other words,
1394    they are the options that will be in force when matching starts. For example,
1395    if the pattern /(?im)abc(?-i)d/ is compiled with the PCRE_EXTENDED option, the
1396    result is PCRE_CASELESS, PCRE_MULTILINE, and PCRE_EXTENDED.
1397    .P
1398  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
1399  alternatives begin with one of the following:  alternatives begin with one of the following:
1400    .sp
1401    ^     unless PCRE_MULTILINE is set    ^     unless PCRE_MULTILINE is set
1402    \\A    always    \eA    always
1403    \\G    always    \eG    always
1404    .\" JOIN
1405    .*    if PCRE_DOTALL is set and there are no back    .*    if PCRE_DOTALL is set and there are no back
1406            references to the subpattern in which .* appears            references to the subpattern in which .* appears
1407    .sp
1408  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
1409  \fBpcre_fullinfo()\fR.  \fBpcre_fullinfo()\fP.
1410    .sp
1411    PCRE_INFO_SIZE    PCRE_INFO_SIZE
1412    .sp
1413  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
1414  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
1415  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
1416  variable.  \fBpcre_compile()\fP. The value that is passed as the argument to
1417    \fBpcre_malloc()\fP when \fBpcre_compile()\fP is getting memory in which to
1418    place the compiled data is the value returned by this option plus the size of
1419    the \fBpcre\fP structure. Studying a compiled pattern, with or without JIT,
1420    does not alter the value returned by this option.
1421    .sp
1422    PCRE_INFO_STUDYSIZE    PCRE_INFO_STUDYSIZE
1423    .sp
1424  Returns the size of the data block pointed to by the \fIstudy_data\fR field in  Return the size in bytes of the data block pointed to by the \fIstudy_data\fP
1425  a \fBpcre_extra\fR block. That is, it is the value that was passed to  field in a \fBpcre_extra\fP block. If \fBpcre_extra\fP is NULL, or there is no
1426  \fBpcre_malloc()\fR when PCRE was getting memory into which to place the data  study data, zero is returned. The fourth argument should point to a
1427  created by \fBpcre_study()\fR. The fourth argument should point to a  \fBsize_t\fP variable. The \fIstudy_data\fP field is set by \fBpcre_study()\fP
1428  \fBsize_t\fR variable.  to record information that will speed up matching (see the section entitled
1429    .\" HTML <a href="#studyingapattern">
1430  .SH OBSOLETE INFO FUNCTION  .\" </a>
1431  .rs  "Studying a pattern"
1432  .sp  .\"
1433  .B int pcre_info(const pcre *\fIcode\fR, int *\fIoptptr\fR, int  above). The format of the \fIstudy_data\fP block is private, but its length
1434  .B *\fIfirstcharptr\fR);  is made available via this option so that it can be saved and restored (see the
1435  .PP  .\" HREF
1436  The \fBpcre_info()\fR function is now obsolete because its interface is too  \fBpcreprecompile\fP
1437  restrictive to return all the available data about a compiled pattern. New  .\"
1438  programs should use \fBpcre_fullinfo()\fR instead. The yield of  documentation for details).
1439  \fBpcre_info()\fR is the number of capturing subpatterns, or one of the  .sp
1440  following negative numbers:    PCRE_INFO_FIRSTCHARACTERFLAGS
1441    .sp
1442    PCRE_ERROR_NULL       the argument \fIcode\fR was NULL  Return information about the first data unit of any matched string, for a
1443    PCRE_ERROR_BADMAGIC   the "magic number" was not found  non-anchored pattern. The fourth argument should point to an \fBint\fP
1444    variable.
1445  If the \fIoptptr\fR argument is not NULL, a copy of the options with which the  .P
1446  pattern was compiled is placed in the integer it points to (see  If there is a fixed first value, for example, the letter "c" from a pattern
1447  PCRE_INFO_OPTIONS above).  such as (cat|cow|coyote), 1 is returned, and the character value can be
1448    retrieved using PCRE_INFO_FIRSTCHARACTER.
1449  If the pattern is not anchored and the \fIfirstcharptr\fR argument is not NULL,  .P
1450  it is used to pass back information about the first character of any matched  If there is no fixed first value, and if either
1451  string (see PCRE_INFO_FIRSTBYTE above).  .sp
1452    (a) the pattern was compiled with the PCRE_MULTILINE option, and every branch
1453  .SH MATCHING A PATTERN  starts with "^", or
1454  .rs  .sp
1455  .sp  (b) every branch of the pattern starts with ".*" and PCRE_DOTALL is not set
1456  .B int pcre_exec(const pcre *\fIcode\fR, "const pcre_extra *\fIextra\fR,"  (if it were set, the pattern would be anchored),
1457  .ti +5n  .sp
1458  .B "const char *\fIsubject\fR," int \fIlength\fR, int \fIstartoffset\fR,  2 is returned, indicating that the pattern matches only at the start of a
1459  .ti +5n  subject string or after any newline within the string. Otherwise 0 is
1460  .B int \fIoptions\fR, int *\fIovector\fR, int \fIovecsize\fR);  returned. For anchored patterns, 0 is returned.
1461  .PP  .sp
1462  The function \fBpcre_exec()\fR is called to match a subject string against a    PCRE_INFO_FIRSTCHARACTER
1463  pre-compiled pattern, which is passed in the \fIcode\fR argument. If the  .sp
1464  pattern has been studied, the result of the study should be passed in the  Return the fixed first character value, if PCRE_INFO_FIRSTCHARACTERFLAGS
1465  \fIextra\fR argument.  returned 1; otherwise returns 0. The fourth argument should point to an
1466    \fBuint_t\fP variable.
1467  Here is an example of a simple call to \fBpcre_exec()\fR:  .P
1468    In the 8-bit library, the value is always less than 256. In the 16-bit library
1469    the value can be up to 0xffff. In the 32-bit library in UTF-32 mode the value
1470    can be up to 0x10ffff, and up to 0xffffffff when not using UTF-32 mode.
1471    .P
1472    If there is no fixed first value, and if either
1473    .sp
1474    (a) the pattern was compiled with the PCRE_MULTILINE option, and every branch
1475    starts with "^", or
1476    .sp
1477    (b) every branch of the pattern starts with ".*" and PCRE_DOTALL is not set
1478    (if it were set, the pattern would be anchored),
1479    .sp
1480    -1 is returned, indicating that the pattern matches only at the start of a
1481    subject string or after any newline within the string. Otherwise -2 is
1482    returned. For anchored patterns, -2 is returned.
1483    .sp
1484      PCRE_INFO_REQUIREDCHARFLAGS
1485    .sp
1486    Returns 1 if there is a rightmost literal data unit that must exist in any
1487    matched string, other than at its start. The fourth argument should  point to
1488    an \fBint\fP variable. If there is no such value, 0 is returned. If returning
1489    1, the character value itself can be retrieved using PCRE_INFO_REQUIREDCHAR.
1490    .P
1491    For anchored patterns, a last literal value is recorded only if it follows
1492    something of variable length. For example, for the pattern /^a\ed+z\ed+/ the
1493    returned value 1 (with "z" returned from PCRE_INFO_REQUIREDCHAR), but for
1494    /^a\edz\ed/ the returned value is 0.
1495    .sp
1496      PCRE_INFO_REQUIREDCHAR
1497    .sp
1498    Return the value of the rightmost literal data unit that must exist in any
1499    matched string, other than at its start, if such a value has been recorded. The
1500    fourth argument should point to an \fBuint32_t\fP variable. If there is no such
1501    value, 0 is returned.
1502    .
1503    .
1504    .SH "REFERENCE COUNTS"
1505    .rs
1506    .sp
1507    .B int pcre_refcount(pcre *\fIcode\fP, int \fIadjust\fP);
1508    .PP
1509    The \fBpcre_refcount()\fP function is used to maintain a reference count in the
1510    data block that contains a compiled pattern. It is provided for the benefit of
1511    applications that operate in an object-oriented manner, where different parts
1512    of the application may be using the same compiled pattern, but you want to free
1513    the block when they are all done.
1514    .P
1515    When a pattern is compiled, the reference count field is initialized to zero.
1516    It is changed only by calling this function, whose action is to add the
1517    \fIadjust\fP value (which may be positive or negative) to it. The yield of the
1518    function is the new value. However, the value of the count is constrained to
1519    lie between 0 and 65535, inclusive. If the new value is outside these limits,
1520    it is forced to the appropriate limit value.
1521    .P
1522    Except when it is zero, the reference count is not correctly preserved if a
1523    pattern is compiled on one host and then transferred to a host whose byte-order
1524    is different. (This seems a highly unlikely scenario.)
1525    .
1526    .
1527    .SH "MATCHING A PATTERN: THE TRADITIONAL FUNCTION"
1528    .rs
1529    .sp
1530    .B int pcre_exec(const pcre *\fIcode\fP, "const pcre_extra *\fIextra\fP,"
1531    .ti +5n
1532    .B "const char *\fIsubject\fP," int \fIlength\fP, int \fIstartoffset\fP,
1533    .ti +5n
1534    .B int \fIoptions\fP, int *\fIovector\fP, int \fIovecsize\fP);
1535    .P
1536    The function \fBpcre_exec()\fP is called to match a subject string against a
1537    compiled pattern, which is passed in the \fIcode\fP argument. If the
1538    pattern was studied, the result of the study should be passed in the
1539    \fIextra\fP argument. You can call \fBpcre_exec()\fP with the same \fIcode\fP
1540    and \fIextra\fP arguments as many times as you like, in order to match
1541    different subject strings with the same pattern.
1542    .P
1543    This function is the main matching facility of the library, and it operates in
1544    a Perl-like manner. For specialist use there is also an alternative matching
1545    function, which is described
1546    .\" HTML <a href="#dfamatch">
1547    .\" </a>
1548    below
1549    .\"
1550    in the section about the \fBpcre_dfa_exec()\fP function.
1551    .P
1552    In most applications, the pattern will have been compiled (and optionally
1553    studied) in the same process that calls \fBpcre_exec()\fP. However, it is
1554    possible to save compiled patterns and study data, and then use them later
1555    in different processes, possibly even on different hosts. For a discussion
1556    about this, see the
1557    .\" HREF
1558    \fBpcreprecompile\fP
1559    .\"
1560    documentation.
1561    .P
1562    Here is an example of a simple call to \fBpcre_exec()\fP:
1563    .sp
1564    int rc;    int rc;
1565    int ovector[30];    int ovector[30];
1566    rc = pcre_exec(    rc = pcre_exec(
# Line 659  Here is an example of a simple call to \ Line 1570  Here is an example of a simple call to \
1570      11,             /* the length of the subject string */      11,             /* the length of the subject string */
1571      0,              /* start at offset 0 in the subject */      0,              /* start at offset 0 in the subject */
1572      0,              /* default options */      0,              /* default options */
1573      ovector,        /* vector for substring information */      ovector,        /* vector of integers for substring information */
1574      30);            /* number of elements in the vector */      30);            /* number of elements (NOT size in bytes) */
1575    .
1576  If the \fIextra\fR argument is not NULL, it must point to a \fBpcre_extra\fR  .
1577  data block. The \fBpcre_study()\fR function returns such a block (when it  .\" HTML <a name="extradata"></a>
1578    .SS "Extra data for \fBpcre_exec()\fR"
1579    .rs
1580    .sp
1581    If the \fIextra\fP argument is not NULL, it must point to a \fBpcre_extra\fP
1582    data block. The \fBpcre_study()\fP function returns such a block (when it
1583  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
1584  additional information in it. The fields in the block are as follows:  additional information in it. The \fBpcre_extra\fP block contains the following
1585    fields (not necessarily in this order):
1586    unsigned long int \fIflags\fR;  .sp
1587    void *\fIstudy_data\fR;    unsigned long int \fIflags\fP;
1588    unsigned long int \fImatch_limit\fR;    void *\fIstudy_data\fP;
1589    void *\fIcallout_data\fR;    void *\fIexecutable_jit\fP;
1590      unsigned long int \fImatch_limit\fP;
1591  The \fIflags\fR field is a bitmap that specifies which of the other fields    unsigned long int \fImatch_limit_recursion\fP;
1592  are set. The flag bits are:    void *\fIcallout_data\fP;
1593      const unsigned char *\fItables\fP;
1594    PCRE_EXTRA_STUDY_DATA    unsigned char **\fImark\fP;
1595    PCRE_EXTRA_MATCH_LIMIT  .sp
1596    In the 16-bit version of this structure, the \fImark\fP field has type
1597    "PCRE_UCHAR16 **".
1598    .sp
1599    In the 32-bit version of this structure, the \fImark\fP field has type
1600    "PCRE_UCHAR32 **".
1601    .P
1602    The \fIflags\fP field is used to specify which of the other fields are set. The
1603    flag bits are:
1604    .sp
1605    PCRE_EXTRA_CALLOUT_DATA    PCRE_EXTRA_CALLOUT_DATA
1606      PCRE_EXTRA_EXECUTABLE_JIT
1607  Other flag bits should be set to zero. The \fIstudy_data\fR field is set in the    PCRE_EXTRA_MARK
1608  \fBpcre_extra\fR block that is returned by \fBpcre_study()\fR, together with    PCRE_EXTRA_MATCH_LIMIT
1609  the appropriate flag bit. You should not set this yourself, but you can add to    PCRE_EXTRA_MATCH_LIMIT_RECURSION
1610  the block by setting the other fields.    PCRE_EXTRA_STUDY_DATA
1611      PCRE_EXTRA_TABLES
1612  The \fImatch_limit\fR field provides a means of preventing PCRE from using up a  .sp
1613    Other flag bits should be set to zero. The \fIstudy_data\fP field and sometimes
1614    the \fIexecutable_jit\fP field are set in the \fBpcre_extra\fP block that is
1615    returned by \fBpcre_study()\fP, together with the appropriate flag bits. You
1616    should not set these yourself, but you may add to the block by setting other
1617    fields and their corresponding flag bits.
1618    .P
1619    The \fImatch_limit\fP field provides a means of preventing PCRE from using up a
1620  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,
1621  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
1622  classic example is the use of nested unlimited repeats. Internally, PCRE uses a  classic example is a pattern that uses nested unlimited repeats.
1623  function called \fBmatch()\fR which it calls repeatedly (sometimes  .P
1624  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
1625  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
1626  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
1627  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
1628    patterns that are not anchored, the count restarts from zero for each position
1629  The default limit for the library can be set when PCRE is built; the default  in the subject string.
1630    .P
1631    When \fBpcre_exec()\fP is called with a pattern that was successfully studied
1632    with a JIT option, the way that the matching is executed is entirely different.
1633    However, there is still the possibility of runaway matching that goes on for a
1634    very long time, and so the \fImatch_limit\fP value is also used in this case
1635    (but in a different way) to limit how long the matching can continue.
1636    .P
1637    The default value for the limit can be set when PCRE is built; the default
1638  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
1639  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
1640  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
1641  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
1642  exceeded, \fBpcre_exec()\fR returns PCRE_ERROR_MATCHLIMIT.  PCRE_ERROR_MATCHLIMIT.
1643    .P
1644  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
1645  which is described in the \fBpcrecallout\fR documentation.  instead of limiting the total number of times that \fBmatch()\fP is called, it
1646    limits the depth of recursion. The recursion depth is a smaller number than the
1647  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.
1648  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.
1649  first matching position. However, if a pattern was compiled with PCRE_ANCHORED,  .P
1650  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
1651  unachored at matching time.  used, or, when PCRE has been compiled to use memory on the heap instead of the
1652    stack, the amount of heap memory that can be used. This limit is not relevant,
1653  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.
1654  string is automatically checked. If an invalid UTF-8 sequence of bytes is  .P
1655  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
1656  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
1657  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
1658  \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
1659  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
1660    is exceeded, \fBpcre_exec()\fP returns PCRE_ERROR_RECURSIONLIMIT.
1661  There are also three further options that can be set only at matching time:  .P
1662    The \fIcallout_data\fP field is used in conjunction with the "callout" feature,
1663    and is described in the
1664    .\" HREF
1665    \fBpcrecallout\fP
1666    .\"
1667    documentation.
1668    .P
1669    The \fItables\fP field is used to pass a character tables pointer to
1670    \fBpcre_exec()\fP; this overrides the value that is stored with the compiled
1671    pattern. A non-NULL value is stored with the compiled pattern only if custom
1672    tables were supplied to \fBpcre_compile()\fP via its \fItableptr\fP argument.
1673    If NULL is passed to \fBpcre_exec()\fP using this mechanism, it forces PCRE's
1674    internal tables to be used. This facility is helpful when re-using patterns
1675    that have been saved after compiling with an external set of tables, because
1676    the external tables might be at a different address when \fBpcre_exec()\fP is
1677    called. See the
1678    .\" HREF
1679    \fBpcreprecompile\fP
1680    .\"
1681    documentation for a discussion of saving compiled patterns for later use.
1682    .P
1683    If PCRE_EXTRA_MARK is set in the \fIflags\fP field, the \fImark\fP field must
1684    be set to point to a suitable variable. If the pattern contains any
1685    backtracking control verbs such as (*MARK:NAME), and the execution ends up with
1686    a name to pass back, a pointer to the name string (zero terminated) is placed
1687    in the variable pointed to by the \fImark\fP field. The names are within the
1688    compiled pattern; if you wish to retain such a name you must copy it before
1689    freeing the memory of a compiled pattern. If there is no name to pass back, the
1690    variable pointed to by the \fImark\fP field is set to NULL. For details of the
1691    backtracking control verbs, see the section entitled
1692    .\" HTML <a href="pcrepattern#backtrackcontrol">
1693    .\" </a>
1694    "Backtracking control"
1695    .\"
1696    in the
1697    .\" HREF
1698    \fBpcrepattern\fP
1699    .\"
1700    documentation.
1701    .
1702    .
1703    .\" HTML <a name="execoptions"></a>
1704    .SS "Option bits for \fBpcre_exec()\fP"
1705    .rs
1706    .sp
1707    The unused bits of the \fIoptions\fP argument for \fBpcre_exec()\fP must be
1708    zero. The only bits that may be set are PCRE_ANCHORED, PCRE_NEWLINE_\fIxxx\fP,
1709    PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY, PCRE_NOTEMPTY_ATSTART,
1710    PCRE_NO_START_OPTIMIZE, PCRE_NO_UTF8_CHECK, PCRE_PARTIAL_HARD, and
1711    PCRE_PARTIAL_SOFT.
1712    .P
1713    If the pattern was successfully studied with one of the just-in-time (JIT)
1714    compile options, the only supported options for JIT execution are
1715    PCRE_NO_UTF8_CHECK, PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY,
1716    PCRE_NOTEMPTY_ATSTART, PCRE_PARTIAL_HARD, and PCRE_PARTIAL_SOFT. If an
1717    unsupported option is used, JIT execution is disabled and the normal
1718    interpretive code in \fBpcre_exec()\fP is run.
1719    .sp
1720      PCRE_ANCHORED
1721    .sp
1722    The PCRE_ANCHORED option limits \fBpcre_exec()\fP to matching at the first
1723    matching position. If a pattern was compiled with PCRE_ANCHORED, or turned out
1724    to be anchored by virtue of its contents, it cannot be made unachored at
1725    matching time.
1726    .sp
1727      PCRE_BSR_ANYCRLF
1728      PCRE_BSR_UNICODE
1729    .sp
1730    These options (which are mutually exclusive) control what the \eR escape
1731    sequence matches. The choice is either to match only CR, LF, or CRLF, or to
1732    match any Unicode newline sequence. These options override the choice that was
1733    made or defaulted when the pattern was compiled.
1734    .sp
1735      PCRE_NEWLINE_CR
1736      PCRE_NEWLINE_LF
1737      PCRE_NEWLINE_CRLF
1738      PCRE_NEWLINE_ANYCRLF
1739      PCRE_NEWLINE_ANY
1740    .sp
1741    These options override the newline definition that was chosen or defaulted when
1742    the pattern was compiled. For details, see the description of
1743    \fBpcre_compile()\fP above. During matching, the newline choice affects the
1744    behaviour of the dot, circumflex, and dollar metacharacters. It may also alter
1745    the way the match position is advanced after a match failure for an unanchored
1746    pattern.
1747    .P
1748    When PCRE_NEWLINE_CRLF, PCRE_NEWLINE_ANYCRLF, or PCRE_NEWLINE_ANY is set, and a
1749    match attempt for an unanchored pattern fails when the current position is at a
1750    CRLF sequence, and the pattern contains no explicit matches for CR or LF
1751    characters, the match position is advanced by two characters instead of one, in
1752    other words, to after the CRLF.
1753    .P
1754    The above rule is a compromise that makes the most common cases work as
1755    expected. For example, if the pattern is .+A (and the PCRE_DOTALL option is not
1756    set), it does not match the string "\er\enA" because, after failing at the
1757    start, it skips both the CR and the LF before retrying. However, the pattern
1758    [\er\en]A does match that string, because it contains an explicit CR or LF
1759    reference, and so advances only by one character after the first failure.
1760    .P
1761    An explicit match for CR of LF is either a literal appearance of one of those
1762    characters, or one of the \er or \en escape sequences. Implicit matches such as
1763    [^X] do not count, nor does \es (which includes CR and LF in the characters
1764    that it matches).
1765    .P
1766    Notwithstanding the above, anomalous effects may still occur when CRLF is a
1767    valid newline sequence and explicit \er or \en escapes appear in the pattern.
1768    .sp
1769    PCRE_NOTBOL    PCRE_NOTBOL
1770    .sp
1771  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
1772  circumflex metacharacter should not match before it. Setting this without  beginning of a line, so the circumflex metacharacter should not match before
1773  PCRE_MULTILINE (at compile time) causes circumflex never to match.  it. Setting this without PCRE_MULTILINE (at compile time) causes circumflex
1774    never to match. This option affects only the behaviour of the circumflex
1775    metacharacter. It does not affect \eA.
1776    .sp
1777    PCRE_NOTEOL    PCRE_NOTEOL
1778    .sp
1779  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
1780  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
1781  it. Setting this without PCRE_MULTILINE (at compile time) causes dollar never  mode) a newline immediately before it. Setting this without PCRE_MULTILINE (at
1782  to match.  compile time) causes dollar never to match. This option affects only the
1783    behaviour of the dollar metacharacter. It does not affect \eZ or \ez.
1784    .sp
1785    PCRE_NOTEMPTY    PCRE_NOTEMPTY
1786    .sp
1787  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
1788  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
1789  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
1790    .sp
1791    a?b?    a?b?
1792    .sp
1793  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
1794  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
1795  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".
1796    .sp
1797  Perl has no direct equivalent of PCRE_NOTEMPTY, but it does make a special case    PCRE_NOTEMPTY_ATSTART
1798  of a pattern match of the empty string within its \fBsplit()\fR function, and  .sp
1799  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
1800  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
1801  PCRE_NOTEMPTY set, and then if that fails by advancing the starting offset (see  can occur only if the pattern contains \eK.
1802  below) and trying an ordinary match again.  .P
1803    Perl has no direct equivalent of PCRE_NOTEMPTY or PCRE_NOTEMPTY_ATSTART, but it
1804  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
1805  \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
1806  \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
1807  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
1808  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
1809    ordinary match again. There is some code that demonstrates how to do this in
1810  If the pattern was compiled with the PCRE_UTF8 option, the subject must be a  the
1811  sequence of bytes that is a valid UTF-8 string. If an invalid UTF-8 string is  .\" HREF
1812  passed, PCRE's behaviour is not defined.  \fBpcredemo\fP
1813    .\"
1814    sample program. In the most general case, you have to check to see if the
1815    newline convention recognizes CRLF as a newline, and if so, and the current
1816    character is CR followed by LF, advance the starting offset by two characters
1817    instead of one.
1818    .sp
1819      PCRE_NO_START_OPTIMIZE
1820    .sp
1821    There are a number of optimizations that \fBpcre_exec()\fP uses at the start of
1822    a match, in order to speed up the process. For example, if it is known that an
1823    unanchored match must start with a specific character, it searches the subject
1824    for that character, and fails immediately if it cannot find it, without
1825    actually running the main matching function. This means that a special item
1826    such as (*COMMIT) at the start of a pattern is not considered until after a
1827    suitable starting point for the match has been found. When callouts or (*MARK)
1828    items are in use, these "start-up" optimizations can cause them to be skipped
1829    if the pattern is never actually used. The start-up optimizations are in effect
1830    a pre-scan of the subject that takes place before the pattern is run.
1831    .P
1832    The PCRE_NO_START_OPTIMIZE option disables the start-up optimizations, possibly
1833    causing performance to suffer, but ensuring that in cases where the result is
1834    "no match", the callouts do occur, and that items such as (*COMMIT) and (*MARK)
1835    are considered at every possible starting position in the subject string. If
1836    PCRE_NO_START_OPTIMIZE is set at compile time, it cannot be unset at matching
1837    time. The use of PCRE_NO_START_OPTIMIZE disables JIT execution; when it is set,
1838    matching is always done using interpretively.
1839    .P
1840    Setting PCRE_NO_START_OPTIMIZE can change the outcome of a matching operation.
1841    Consider the pattern
1842    .sp
1843      (*COMMIT)ABC
1844    .sp
1845    When this is compiled, PCRE records the fact that a match must start with the
1846    character "A". Suppose the subject string is "DEFABC". The start-up
1847    optimization scans along the subject, finds "A" and runs the first match
1848    attempt from there. The (*COMMIT) item means that the pattern must match the
1849    current starting position, which in this case, it does. However, if the same
1850    match is run with PCRE_NO_START_OPTIMIZE set, the initial scan along the
1851    subject string does not happen. The first match attempt is run starting from
1852    "D" and when this fails, (*COMMIT) prevents any further matches being tried, so
1853    the overall result is "no match". If the pattern is studied, more start-up
1854    optimizations may be used. For example, a minimum length for the subject may be
1855    recorded. Consider the pattern
1856    .sp
1857      (*MARK:A)(X|Y)
1858    .sp
1859    The minimum length for a match is one character. If the subject is "ABC", there
1860    will be attempts to match "ABC", "BC", "C", and then finally an empty string.
1861    If the pattern is studied, the final attempt does not take place, because PCRE
1862    knows that the subject is too short, and so the (*MARK) is never encountered.
1863    In this case, studying the pattern does not affect the overall match result,
1864    which is still "no match", but it does affect the auxiliary information that is
1865    returned.
1866    .sp
1867      PCRE_NO_UTF8_CHECK
1868    .sp
1869    When PCRE_UTF8 is set at compile time, the validity of the subject as a UTF-8
1870    string is automatically checked when \fBpcre_exec()\fP is subsequently called.
1871    The entire string is checked before any other processing takes place. The value
1872    of \fIstartoffset\fP is also checked to ensure that it points to the start of a
1873    UTF-8 character. There is a discussion about the
1874    .\" HTML <a href="pcreunicode.html#utf8strings">
1875    .\" </a>
1876    validity of UTF-8 strings
1877    .\"
1878    in the
1879    .\" HREF
1880    \fBpcreunicode\fP
1881    .\"
1882    page. If an invalid sequence of bytes is found, \fBpcre_exec()\fP returns the
1883    error PCRE_ERROR_BADUTF8 or, if PCRE_PARTIAL_HARD is set and the problem is a
1884    truncated character at the end of the subject, PCRE_ERROR_SHORTUTF8. In both
1885    cases, information about the precise nature of the error may also be returned
1886    (see the descriptions of these errors in the section entitled \fIError return
1887    values from\fP \fBpcre_exec()\fP
1888    .\" HTML <a href="#errorlist">
1889    .\" </a>
1890    below).
1891    .\"
1892    If \fIstartoffset\fP contains a value that does not point to the start of a
1893    UTF-8 character (or to the end of the subject), PCRE_ERROR_BADUTF8_OFFSET is
1894    returned.
1895    .P
1896    If you already know that your subject is valid, and you want to skip these
1897    checks for performance reasons, you can set the PCRE_NO_UTF8_CHECK option when
1898    calling \fBpcre_exec()\fP. You might want to do this for the second and
1899    subsequent calls to \fBpcre_exec()\fP if you are making repeated calls to find
1900    all the matches in a single subject string. However, you should be sure that
1901    the value of \fIstartoffset\fP points to the start of a character (or the end
1902    of the subject). When PCRE_NO_UTF8_CHECK is set, the effect of passing an
1903    invalid string as a subject or an invalid value of \fIstartoffset\fP is
1904    undefined. Your program may crash.
1905    .sp
1906      PCRE_PARTIAL_HARD
1907      PCRE_PARTIAL_SOFT
1908    .sp
1909    These options turn on the partial matching feature. For backwards
1910    compatibility, PCRE_PARTIAL is a synonym for PCRE_PARTIAL_SOFT. A partial match
1911    occurs if the end of the subject string is reached successfully, but there are
1912    not enough subject characters to complete the match. If this happens when
1913    PCRE_PARTIAL_SOFT (but not PCRE_PARTIAL_HARD) is set, matching continues by
1914    testing any remaining alternatives. Only if no complete match can be found is
1915    PCRE_ERROR_PARTIAL returned instead of PCRE_ERROR_NOMATCH. In other words,
1916    PCRE_PARTIAL_SOFT says that the caller is prepared to handle a partial match,
1917    but only if no complete match can be found.
1918    .P
1919    If PCRE_PARTIAL_HARD is set, it overrides PCRE_PARTIAL_SOFT. In this case, if a
1920    partial match is found, \fBpcre_exec()\fP immediately returns
1921    PCRE_ERROR_PARTIAL, without considering any other alternatives. In other words,
1922    when PCRE_PARTIAL_HARD is set, a partial match is considered to be more
1923    important that an alternative complete match.
1924    .P
1925    In both cases, the portion of the string that was inspected when the partial
1926    match was found is set as the first matching string. There is a more detailed
1927    discussion of partial and multi-segment matching, with examples, in the
1928    .\" HREF
1929    \fBpcrepartial\fP
1930    .\"
1931    documentation.
1932    .
1933    .
1934    .SS "The string to be matched by \fBpcre_exec()\fP"
1935    .rs
1936    .sp
1937    The subject string is passed to \fBpcre_exec()\fP as a pointer in
1938    \fIsubject\fP, a length in bytes in \fIlength\fP, and a starting byte offset
1939    in \fIstartoffset\fP. If this is negative or greater than the length of the
1940    subject, \fBpcre_exec()\fP returns PCRE_ERROR_BADOFFSET. When the starting
1941    offset is zero, the search for a match starts at the beginning of the subject,
1942    and this is by far the most common case. In UTF-8 mode, the byte offset must
1943    point to the start of a UTF-8 character (or the end of the subject). Unlike the
1944    pattern string, the subject may contain binary zero bytes.
1945    .P
1946  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
1947  same subject by calling \fBpcre_exec()\fR again after a previous success.  same subject by calling \fBpcre_exec()\fP again after a previous success.
1948  Setting \fIstartoffset\fR differs from just passing over a shortened string and  Setting \fIstartoffset\fP differs from just passing over a shortened string and
1949  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
1950  lookbehind. For example, consider the pattern  lookbehind. For example, consider the pattern
1951    .sp
1952    \\Biss\\B    \eBiss\eB
1953    .sp
1954  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
1955  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
1956  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
1957  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
1958  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
1959  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
1960  \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
1961  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
1962  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.
1963    .P
1964    Finding all the matches in a subject is tricky when the pattern can match an
1965    empty string. It is possible to emulate Perl's /g behaviour by first trying the
1966    match again at the same offset, with the PCRE_NOTEMPTY_ATSTART and
1967    PCRE_ANCHORED options, and then if that fails, advancing the starting offset
1968    and trying an ordinary match again. There is some code that demonstrates how to
1969    do this in the
1970    .\" HREF
1971    \fBpcredemo\fP
1972    .\"
1973    sample program. In the most general case, you have to check to see if the
1974    newline convention recognizes CRLF as a newline, and if so, and the current
1975    character is CR followed by LF, advance the starting offset by two characters
1976    instead of one.
1977    .P
1978  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
1979  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
1980  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.
1981    .
1982    .
1983    .SS "How \fBpcre_exec()\fP returns captured substrings"
1984    .rs
1985    .sp
1986  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
1987  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
1988  pattern. Following the usage in Jeffrey Friedl's book, this is called  pattern. Following the usage in Jeffrey Friedl's book, this is called
1989  "capturing" in what follows, and the phrase "capturing subpattern" is used for  "capturing" in what follows, and the phrase "capturing subpattern" is used for
1990  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
1991  kinds of parenthesized subpattern that do not cause substrings to be captured.  kinds of parenthesized subpattern that do not cause substrings to be captured.
1992    .P
1993  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
1994  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
1995  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
1996  back captured substrings, each substring using a pair of integers. The  argument is NOT the size of \fIovector\fP in bytes.
1997  remaining third of the vector is used as workspace by \fBpcre_exec()\fR while  .P
1998  matching capturing subpatterns, and is not available for passing back  The first two-thirds of the vector is used to pass back captured substrings,
1999  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
2000  three. If it is not, it is rounded down.  used as workspace by \fBpcre_exec()\fP while matching capturing subpatterns,
2001    and is not available for passing back information. The number passed in
2002  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
2003  returned in pairs of integers, starting at the beginning of \fIovector\fR, and  rounded down.
2004  continuing up to two-thirds of its length at the most. The first element of a  .P
2005  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
2006  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
2007  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
2008  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
2009  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
2010  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
2011  subpatterns, the return value from a successful match is 1, indicating that  mode. They are not character counts.
2012  just the first pair of offsets has been set.  .P
2013    The first pair of integers, \fIovector[0]\fP and \fIovector[1]\fP, identify the
2014  Some convenience functions are provided for extracting the captured substrings  portion of the subject string matched by the entire pattern. The next pair is
2015  as separate strings. These are described in the following section.  used for the first capturing subpattern, and so on. The value returned by
2016    \fBpcre_exec()\fP is one more than the highest numbered pair that has been set.
2017  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
2018  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
2019  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.
2020  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.  
   
2021  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
2022  string that it matched that gets returned.  string that it matched that is returned.
2023    .P
2024  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
2025  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
2026  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
2027  \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
2028  \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
2029  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
2030  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
2031  to supply an \fIovector\fR.  is usually advisable to supply an \fIovector\fP of reasonable size.
2032    .P
2033  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
2034    in fact the vector is exactly the right size for the final match. For example,
2035    consider the pattern
2036    .sp
2037      (a)(?:(b)c|bd)
2038    .sp
2039    If a vector of 6 elements (allowing for only 1 captured substring) is given
2040    with subject string "abd", \fBpcre_exec()\fP will try to set the second
2041    captured string, thereby recording a vector overflow, before failing to match
2042    "c" and backing up to try the second alternative. The zero return, however,
2043    does correctly indicate that the maximum number of slots (namely 2) have been
2044    filled. In similar cases where there is temporary overflow, but the final
2045    number of used slots is actually less than the maximum, a non-zero value is
2046    returned.
2047    .P
2048    The \fBpcre_fullinfo()\fP function can be used to find out how many capturing
2049  subpatterns there are in a compiled pattern. The smallest size for  subpatterns there are in a compiled pattern. The smallest size for
2050  \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
2051  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.
2052    .P
2053  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
2054    the subject when subpattern \fIn\fP has not been used at all. For example, if
2055    the string "abc" is matched against the pattern (a|(z))(bc) the return from the
2056    function is 4, and subpatterns 1 and 3 are matched, but 2 is not. When this
2057    happens, both values in the offset pairs corresponding to unused subpatterns
2058    are set to -1.
2059    .P
2060    Offset values that correspond to unused subpatterns at the end of the
2061    expression are also set to -1. For example, if the string "abc" is matched
2062    against the pattern (abc)(x(yz)?)? subpatterns 2 and 3 are not matched. The
2063    return from the function is 2, because the highest used capturing subpattern
2064    number is 1, and the offsets for for the second and third capturing subpatterns
2065    (assuming the vector is large enough, of course) are set to -1.
2066    .P
2067    \fBNote\fP: Elements in the first two-thirds of \fIovector\fP that do not
2068    correspond to capturing parentheses in the pattern are never changed. That is,
2069    if a pattern contains \fIn\fP capturing parentheses, no more than
2070    \fIovector[0]\fP to \fIovector[2n+1]\fP are set by \fBpcre_exec()\fP. The other
2071    elements (in the first two-thirds) retain whatever values they previously had.
2072    .P
2073    Some convenience functions are provided for extracting the captured substrings
2074    as separate strings. These are described below.
2075    .
2076    .
2077    .\" HTML <a name="errorlist"></a>
2078    .SS "Error return values from \fBpcre_exec()\fP"
2079    .rs
2080    .sp
2081    If \fBpcre_exec()\fP fails, it returns a negative number. The following are
2082  defined in the header file:  defined in the header file:
2083    .sp
2084    PCRE_ERROR_NOMATCH        (-1)    PCRE_ERROR_NOMATCH        (-1)
2085    .sp
2086  The subject string did not match the pattern.  The subject string did not match the pattern.
2087    .sp
2088    PCRE_ERROR_NULL           (-2)    PCRE_ERROR_NULL           (-2)
2089    .sp
2090  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
2091  NULL and \fIovecsize\fR was not zero.  NULL and \fIovecsize\fP was not zero.
2092    .sp
2093    PCRE_ERROR_BADOPTION      (-3)    PCRE_ERROR_BADOPTION      (-3)
2094    .sp
2095  An unrecognized bit was set in the \fIoptions\fR argument.  An unrecognized bit was set in the \fIoptions\fP argument.
2096    .sp
2097    PCRE_ERROR_BADMAGIC       (-4)    PCRE_ERROR_BADMAGIC       (-4)
2098    .sp
2099  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
2100  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
2101  magic number isn't present.  compiled in an environment of one endianness is run in an environment with the
2102    other endianness. This is the error that PCRE gives when the magic number is
2103    PCRE_ERROR_UNKNOWN_NODE   (-5)  not present.
2104    .sp
2105      PCRE_ERROR_UNKNOWN_OPCODE (-5)
2106    .sp
2107  While running the pattern match, an unknown item was encountered in the  While running the pattern match, an unknown item was encountered in the
2108  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
2109  of the compiled pattern.  of the compiled pattern.
2110    .sp
2111    PCRE_ERROR_NOMEMORY       (-6)    PCRE_ERROR_NOMEMORY       (-6)
2112    .sp
2113  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
2114  \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
2115  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
2116  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
2117  the end of matching.  automatically freed at the end of matching.
2118    .P
2119    This error is also given if \fBpcre_stack_malloc()\fP fails in
2120    \fBpcre_exec()\fP. This can happen only when PCRE has been compiled with
2121    \fB--disable-stack-for-recursion\fP.
2122    .sp
2123    PCRE_ERROR_NOSUBSTRING    (-7)    PCRE_ERROR_NOSUBSTRING    (-7)
2124    .sp
2125  This error is used by the \fBpcre_copy_substring()\fR,  This error is used by the \fBpcre_copy_substring()\fP,
2126  \fBpcre_get_substring()\fR, and \fBpcre_get_substring_list()\fR functions (see  \fBpcre_get_substring()\fP, and \fBpcre_get_substring_list()\fP functions (see
2127  below). It is never returned by \fBpcre_exec()\fR.  below). It is never returned by \fBpcre_exec()\fP.
2128    .sp
2129    PCRE_ERROR_MATCHLIMIT     (-8)    PCRE_ERROR_MATCHLIMIT     (-8)
2130    .sp
2131  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
2132  field in a \fBpcre_extra\fR structure (or defaulted) was reached. See the  \fBpcre_extra\fP structure (or defaulted) was reached. See the description
2133  description above.  above.
2134    .sp
2135    PCRE_ERROR_CALLOUT        (-9)    PCRE_ERROR_CALLOUT        (-9)
2136    .sp
2137  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
2138  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
2139  \fBpcrecallout\fR documentation for details.  .\" HREF
2140    \fBpcrecallout\fP
2141    PCRE_ERROR_BADUTF8       (-10)  .\"
2142    documentation for details.
2143  A string that contains an invalid UTF-8 byte sequence was passed as a subject.  .sp
2144      PCRE_ERROR_BADUTF8        (-10)
2145  .SH EXTRACTING CAPTURED SUBSTRINGS BY NUMBER  .sp
2146    A string that contains an invalid UTF-8 byte sequence was passed as a subject,
2147    and the PCRE_NO_UTF8_CHECK option was not set. If the size of the output vector
2148    (\fIovecsize\fP) is at least 2, the byte offset to the start of the the invalid
2149    UTF-8 character is placed in the first element, and a reason code is placed in
2150    the second element. The reason codes are listed in the
2151    .\" HTML <a href="#badutf8reasons">
2152    .\" </a>
2153    following section.
2154    .\"
2155    For backward compatibility, if PCRE_PARTIAL_HARD is set and the problem is a
2156    truncated UTF-8 character at the end of the subject (reason codes 1 to 5),
2157    PCRE_ERROR_SHORTUTF8 is returned instead of PCRE_ERROR_BADUTF8.
2158    .sp
2159      PCRE_ERROR_BADUTF8_OFFSET (-11)
2160    .sp
2161    The UTF-8 byte sequence that was passed as a subject was checked and found to
2162    be valid (the PCRE_NO_UTF8_CHECK option was not set), but the value of
2163    \fIstartoffset\fP did not point to the beginning of a UTF-8 character or the
2164    end of the subject.
2165    .sp
2166      PCRE_ERROR_PARTIAL        (-12)
2167    .sp
2168    The subject string did not match, but it did match partially. See the
2169    .\" HREF
2170    \fBpcrepartial\fP
2171    .\"
2172    documentation for details of partial matching.
2173    .sp
2174      PCRE_ERROR_BADPARTIAL     (-13)
2175    .sp
2176    This code is no longer in use. It was formerly returned when the PCRE_PARTIAL
2177    option was used with a compiled pattern containing items that were not
2178    supported for partial matching. From release 8.00 onwards, there are no
2179    restrictions on partial matching.
2180    .sp
2181      PCRE_ERROR_INTERNAL       (-14)
2182    .sp
2183    An unexpected internal error has occurred. This error could be caused by a bug
2184    in PCRE or by overwriting of the compiled pattern.
2185    .sp
2186      PCRE_ERROR_BADCOUNT       (-15)
2187    .sp
2188    This error is given if the value of the \fIovecsize\fP argument is negative.
2189    .sp
2190      PCRE_ERROR_RECURSIONLIMIT (-21)
2191    .sp
2192    The internal recursion limit, as specified by the \fImatch_limit_recursion\fP
2193    field in a \fBpcre_extra\fP structure (or defaulted) was reached. See the
2194    description above.
2195    .sp
2196      PCRE_ERROR_BADNEWLINE     (-23)
2197    .sp
2198    An invalid combination of PCRE_NEWLINE_\fIxxx\fP options was given.
2199    .sp
2200      PCRE_ERROR_BADOFFSET      (-24)
2201    .sp
2202    The value of \fIstartoffset\fP was negative or greater than the length of the
2203    subject, that is, the value in \fIlength\fP.
2204    .sp
2205      PCRE_ERROR_SHORTUTF8      (-25)
2206    .sp
2207    This error is returned instead of PCRE_ERROR_BADUTF8 when the subject string
2208    ends with a truncated UTF-8 character and the PCRE_PARTIAL_HARD option is set.
2209    Information about the failure is returned as for PCRE_ERROR_BADUTF8. It is in
2210    fact sufficient to detect this case, but this special error code for
2211    PCRE_PARTIAL_HARD precedes the implementation of returned information; it is
2212    retained for backwards compatibility.
2213    .sp
2214      PCRE_ERROR_RECURSELOOP    (-26)
2215    .sp
2216    This error is returned when \fBpcre_exec()\fP detects a recursion loop within
2217    the pattern. Specifically, it means that either the whole pattern or a
2218    subpattern has been called recursively for the second time at the same position
2219    in the subject string. Some simple patterns that might do this are detected and
2220    faulted at compile time, but more complicated cases, in particular mutual
2221    recursions between two different subpatterns, cannot be detected until run
2222    time.
2223    .sp
2224      PCRE_ERROR_JIT_STACKLIMIT (-27)
2225    .sp
2226    This error is returned when a pattern that was successfully studied using a
2227    JIT compile option is being matched, but the memory available for the
2228    just-in-time processing stack is not large enough. See the
2229    .\" HREF
2230    \fBpcrejit\fP
2231    .\"
2232    documentation for more details.
2233    .sp
2234      PCRE_ERROR_BADMODE        (-28)
2235    .sp
2236    This error is given if a pattern that was compiled by the 8-bit library is
2237    passed to a 16-bit or 32-bit library function, or vice versa.
2238    .sp
2239      PCRE_ERROR_BADENDIANNESS  (-29)
2240    .sp
2241    This error is given if a pattern that was compiled and saved is reloaded on a
2242    host with different endianness. The utility function
2243    \fBpcre_pattern_to_host_byte_order()\fP can be used to convert such a pattern
2244    so that it runs on the new host.
2245    .sp
2246      PCRE_ERROR_JIT_BADOPTION
2247    .sp
2248    This error is returned when a pattern that was successfully studied using a JIT
2249    compile option is being matched, but the matching mode (partial or complete
2250    match) does not correspond to any JIT compilation mode. When the JIT fast path
2251    function is used, this error may be also given for invalid options. See the
2252    .\" HREF
2253    \fBpcrejit\fP
2254    .\"
2255    documentation for more details.
2256    .sp
2257      PCRE_ERROR_BADLENGTH      (-32)
2258    .sp
2259    This error is given if \fBpcre_exec()\fP is called with a negative value for
2260    the \fIlength\fP argument.
2261    .P
2262    Error numbers -16 to -20, -22, and 30 are not used by \fBpcre_exec()\fP.
2263    .
2264    .
2265    .\" HTML <a name="badutf8reasons"></a>
2266    .SS "Reason codes for invalid UTF-8 strings"
2267    .rs
2268    .sp
2269    This section applies only to the 8-bit library. The corresponding information
2270    for the 16-bit library is given in the
2271    .\" HREF
2272    \fBpcre16\fP
2273    .\"
2274    page. The corresponding information for the 32-bit library is given in the
2275    .\" HREF
2276    \fBpcre32\fP
2277    .\"
2278    page.
2279    .P
2280    When \fBpcre_exec()\fP returns either PCRE_ERROR_BADUTF8 or
2281    PCRE_ERROR_SHORTUTF8, and the size of the output vector (\fIovecsize\fP) is at
2282    least 2, the offset of the start of the invalid UTF-8 character is placed in
2283    the first output vector element (\fIovector[0]\fP) and a reason code is placed
2284    in the second element (\fIovector[1]\fP). The reason codes are given names in
2285    the \fBpcre.h\fP header file:
2286    .sp
2287      PCRE_UTF8_ERR1
2288      PCRE_UTF8_ERR2
2289      PCRE_UTF8_ERR3
2290      PCRE_UTF8_ERR4
2291      PCRE_UTF8_ERR5
2292    .sp
2293    The string ends with a truncated UTF-8 character; the code specifies how many
2294    bytes are missing (1 to 5). Although RFC 3629 restricts UTF-8 characters to be
2295    no longer than 4 bytes, the encoding scheme (originally defined by RFC 2279)
2296    allows for up to 6 bytes, and this is checked first; hence the possibility of
2297    4 or 5 missing bytes.
2298    .sp
2299      PCRE_UTF8_ERR6
2300      PCRE_UTF8_ERR7
2301      PCRE_UTF8_ERR8
2302      PCRE_UTF8_ERR9
2303      PCRE_UTF8_ERR10
2304    .sp
2305    The two most significant bits of the 2nd, 3rd, 4th, 5th, or 6th byte of the
2306    character do not have the binary value 0b10 (that is, either the most
2307    significant bit is 0, or the next bit is 1).
2308    .sp
2309      PCRE_UTF8_ERR11
2310      PCRE_UTF8_ERR12
2311    .sp
2312    A character that is valid by the RFC 2279 rules is either 5 or 6 bytes long;
2313    these code points are excluded by RFC 3629.
2314    .sp
2315      PCRE_UTF8_ERR13
2316    .sp
2317    A 4-byte character has a value greater than 0x10fff; these code points are
2318    excluded by RFC 3629.
2319    .sp
2320      PCRE_UTF8_ERR14
2321    .sp
2322    A 3-byte character has a value in the range 0xd800 to 0xdfff; this range of
2323    code points are reserved by RFC 3629 for use with UTF-16, and so are excluded
2324    from UTF-8.
2325    .sp
2326      PCRE_UTF8_ERR15
2327      PCRE_UTF8_ERR16
2328      PCRE_UTF8_ERR17
2329      PCRE_UTF8_ERR18
2330      PCRE_UTF8_ERR19
2331    .sp
2332    A 2-, 3-, 4-, 5-, or 6-byte character is "overlong", that is, it codes for a
2333    value that can be represented by fewer bytes, which is invalid. For example,
2334    the two bytes 0xc0, 0xae give the value 0x2e, whose correct coding uses just
2335    one byte.
2336    .sp
2337      PCRE_UTF8_ERR20
2338    .sp
2339    The two most significant bits of the first byte of a character have the binary
2340    value 0b10 (that is, the most significant bit is 1 and the second is 0). Such a
2341    byte can only validly occur as the second or subsequent byte of a multi-byte
2342    character.
2343    .sp
2344      PCRE_UTF8_ERR21
2345    .sp
2346    The first byte of a character has the value 0xfe or 0xff. These values can
2347    never occur in a valid UTF-8 string.
2348    .sp
2349      PCRE_UTF8_ERR2
2350    .sp
2351    Non-character. These are the last two characters in each plane (0xfffe, 0xffff,
2352    0x1fffe, 0x1ffff .. 0x10fffe, 0x10ffff), and the characters 0xfdd0..0xfdef.
2353    .
2354    .
2355    .SH "EXTRACTING CAPTURED SUBSTRINGS BY NUMBER"
2356  .rs  .rs
2357  .sp  .sp
2358  .B int pcre_copy_substring(const char *\fIsubject\fR, int *\fIovector\fR,  .B int pcre_copy_substring(const char *\fIsubject\fP, int *\fIovector\fP,
2359  .ti +5n  .ti +5n
2360  .B int \fIstringcount\fR, int \fIstringnumber\fR, char *\fIbuffer\fR,  .B int \fIstringcount\fP, int \fIstringnumber\fP, char *\fIbuffer\fP,
2361  .ti +5n  .ti +5n
2362  .B int \fIbuffersize\fR);  .B int \fIbuffersize\fP);
2363  .PP  .PP
2364  .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,  
2365  .ti +5n  .ti +5n
2366  .B int \fIstringcount\fR, int \fIstringnumber\fR,  .B int \fIstringcount\fP, int \fIstringnumber\fP,
2367  .ti +5n  .ti +5n
2368  .B const char **\fIstringptr\fR);  .B const char **\fIstringptr\fP);
2369  .PP  .PP
2370  .br  .B int pcre_get_substring_list(const char *\fIsubject\fP,
 .B int pcre_get_substring_list(const char *\fIsubject\fR,  
2371  .ti +5n  .ti +5n
2372  .B int *\fIovector\fR, int \fIstringcount\fR, "const char ***\fIlistptr\fR);"  .B int *\fIovector\fP, int \fIstringcount\fP, "const char ***\fIlistptr\fP);"
2373  .PP  .PP
2374  Captured substrings can be accessed directly by using the offsets returned by  Captured substrings can be accessed directly by using the offsets returned by
2375  \fBpcre_exec()\fR in \fIovector\fR. For convenience, the functions  \fBpcre_exec()\fP in \fIovector\fP. For convenience, the functions
2376  \fBpcre_copy_substring()\fR, \fBpcre_get_substring()\fR, and  \fBpcre_copy_substring()\fP, \fBpcre_get_substring()\fP, and
2377  \fBpcre_get_substring_list()\fR are provided for extracting captured substrings  \fBpcre_get_substring_list()\fP are provided for extracting captured substrings
2378  as new, separate, zero-terminated strings. These functions identify substrings  as new, separate, zero-terminated strings. These functions identify substrings
2379  by number. The next section describes functions for extracting named  by number. The next section describes functions for extracting named
2380  substrings. A substring that contains a binary zero is correctly extracted and  substrings.
2381  has a further zero added on the end, but the result is not, of course,  .P
2382  a C string.  A substring that contains a binary zero is correctly extracted and has a
2383    further zero added on the end, but the result is not, of course, a C string.
2384    However, you can process such a string by referring to the length that is
2385    returned by \fBpcre_copy_substring()\fP and \fBpcre_get_substring()\fP.
2386    Unfortunately, the interface to \fBpcre_get_substring_list()\fP is not adequate
2387    for handling strings containing binary zeros, because the end of the final
2388    string is not independently indicated.
2389    .P
2390  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:
2391  \fIsubject\fR is the subject string which has just been successfully matched,  \fIsubject\fP is the subject string that has just been successfully matched,
2392  \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
2393  \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
2394  captured by the match, including the substring that matched the entire regular  captured by the match, including the substring that matched the entire regular
2395  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
2396  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
2397  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
2398  the vector divided by three.  number of elements in the vector divided by three.
2399    .P
2400  The functions \fBpcre_copy_substring()\fR and \fBpcre_get_substring()\fR  The functions \fBpcre_copy_substring()\fP and \fBpcre_get_substring()\fP
2401  extract a single substring, whose number is given as \fIstringnumber\fR. A  extract a single substring, whose number is given as \fIstringnumber\fP. A
2402  value of zero extracts the substring that matched the entire pattern, while  value of zero extracts the substring that matched the entire pattern, whereas
2403  higher values extract the captured substrings. For \fBpcre_copy_substring()\fR,  higher values extract the captured substrings. For \fBpcre_copy_substring()\fP,
2404  the string is placed in \fIbuffer\fR, whose length is given by  the string is placed in \fIbuffer\fP, whose length is given by
2405  \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
2406  obtained via \fBpcre_malloc\fR, and its address is returned via  obtained via \fBpcre_malloc\fP, and its address is returned via
2407  \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
2408  including the terminating zero, or one of  including the terminating zero, or one of these error codes:
2409    .sp
2410    PCRE_ERROR_NOMEMORY       (-6)    PCRE_ERROR_NOMEMORY       (-6)
2411    .sp
2412  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
2413  memory failed for \fBpcre_get_substring()\fR.  memory failed for \fBpcre_get_substring()\fP.
2414    .sp
2415    PCRE_ERROR_NOSUBSTRING    (-7)    PCRE_ERROR_NOSUBSTRING    (-7)
2416    .sp
2417  There is no substring whose number is \fIstringnumber\fR.  There is no substring whose number is \fIstringnumber\fP.
2418    .P
2419  The \fBpcre_get_substring_list()\fR function extracts all available substrings  The \fBpcre_get_substring_list()\fP function extracts all available substrings
2420  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
2421  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
2422  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
2423  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
2424  function is zero if all went well, or  function is zero if all went well, or the error code
2425    .sp
2426    PCRE_ERROR_NOMEMORY       (-6)    PCRE_ERROR_NOMEMORY       (-6)
2427    .sp
2428  if the attempt to get the memory block failed.  if the attempt to get the memory block failed.
2429    .P
2430  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
2431  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
2432  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
2433  string. This can be distinguished from a genuine zero-length substring by  string. This can be distinguished from a genuine zero-length substring by
2434  inspecting the appropriate offset in \fIovector\fR, which is negative for unset  inspecting the appropriate offset in \fIovector\fP, which is negative for unset
2435  substrings.  substrings.
2436    .P
2437  The two convenience functions \fBpcre_free_substring()\fR and  The two convenience functions \fBpcre_free_substring()\fP and
2438  \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
2439  a previous call of \fBpcre_get_substring()\fR or  a previous call of \fBpcre_get_substring()\fP or
2440  \fBpcre_get_substring_list()\fR, respectively. They do nothing more than call  \fBpcre_get_substring_list()\fP, respectively. They do nothing more than call
2441  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
2442  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
2443  linked via a special interface to another programming language which cannot use  linked via a special interface to another programming language that cannot use
2444  \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
2445  provided.  provided.
2446    .
2447  .SH EXTRACTING CAPTURED SUBSTRINGS BY NAME  .
2448    .SH "EXTRACTING CAPTURED SUBSTRINGS BY NAME"
2449  .rs  .rs
2450  .sp  .sp
2451  .B int pcre_copy_named_substring(const pcre *\fIcode\fR,  .B int pcre_get_stringnumber(const pcre *\fIcode\fP,
2452  .ti +5n  .ti +5n
2453  .B const char *\fIsubject\fR, int *\fIovector\fR,  .B const char *\fIname\fP);
2454    .PP
2455    .B int pcre_copy_named_substring(const pcre *\fIcode\fP,
2456  .ti +5n  .ti +5n
2457  .B int \fIstringcount\fR, const char *\fIstringname\fR,  .B const char *\fIsubject\fP, int *\fIovector\fP,
2458  .ti +5n  .ti +5n
2459  .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,  
2460  .ti +5n  .ti +5n
2461  .B const char *\fIname\fR);  .B char *\fIbuffer\fP, int \fIbuffersize\fP);
2462  .PP  .PP
2463  .br  .B int pcre_get_named_substring(const pcre *\fIcode\fP,
 .B int pcre_get_named_substring(const pcre *\fIcode\fR,  
2464  .ti +5n  .ti +5n
2465  .B const char *\fIsubject\fR, int *\fIovector\fR,  .B const char *\fIsubject\fP, int *\fIovector\fP,
2466  .ti +5n  .ti +5n
2467  .B int \fIstringcount\fR, const char *\fIstringname\fR,  .B int \fIstringcount\fP, const char *\fIstringname\fP,
2468  .ti +5n  .ti +5n
2469  .B const char **\fIstringptr\fR);  .B const char **\fIstringptr\fP);
2470  .PP  .PP
2471  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.
2472  can be done by calling \fBpcre_get_stringnumber()\fR. The first argument is the  For example, for this pattern
2473  compiled pattern, and the second is the name. For example, for this pattern  .sp
2474      (a+)b(?<xxx>\ed+)...
2475    ab(?<xxx>\\d+)...  .sp
2476    the number of the subpattern called "xxx" is 2. If the name is known to be
2477  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
2478  extract the substring directly, or use one of the functions described in the  calling \fBpcre_get_stringnumber()\fP. The first argument is the compiled
2479  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
2480  whole job.  subpattern number, or PCRE_ERROR_NOSUBSTRING (-7) if there is no subpattern of
2481    that name.
2482  Most of the arguments of \fIpcre_copy_named_substring()\fR and  .P
2483  \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
2484  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
2485  differences.  two functions that do the whole job.
2486    .P
2487    Most of the arguments of \fBpcre_copy_named_substring()\fP and
2488    \fBpcre_get_named_substring()\fP are the same as those for the similarly named
2489    functions that extract by number. As these are described in the previous
2490    section, they are not re-described here. There are just two differences:
2491    .P
2492  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
2493  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
2494  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
2495  translation table.  translation table.
2496    .P
2497  These functions call \fBpcre_get_stringnumber()\fR, and if it succeeds, they  These functions call \fBpcre_get_stringnumber()\fP, and if it succeeds, they
2498  then call \fIpcre_copy_substring()\fR or \fIpcre_get_substring()\fR, as  then call \fBpcre_copy_substring()\fP or \fBpcre_get_substring()\fP, as
2499  appropriate.  appropriate. \fBNOTE:\fP If PCRE_DUPNAMES is set and there are duplicate names,
2500    the behaviour may not be what you want (see the next section).
2501  .in 0  .P
2502  Last updated: 20 August 2003  \fBWarning:\fP If the pattern uses the (?| feature to set up multiple
2503  .br  subpatterns with the same number, as described in the
2504  Copyright (c) 1997-2003 University of Cambridge.  .\" HTML <a href="pcrepattern.html#dupsubpatternnumber">
2505    .\" </a>
2506    section on duplicate subpattern numbers
2507    .\"
2508    in the
2509    .\" HREF
2510    \fBpcrepattern\fP
2511    .\"
2512    page, you cannot use names to distinguish the different subpatterns, because
2513    names are not included in the compiled code. The matching process uses only
2514    numbers. For this reason, the use of different names for subpatterns of the
2515    same number causes an error at compile time.
2516    .
2517    .
2518    .SH "DUPLICATE SUBPATTERN NAMES"
2519    .rs
2520    .sp
2521    .B int pcre_get_stringtable_entries(const pcre *\fIcode\fP,
2522    .ti +5n
2523    .B const char *\fIname\fP, char **\fIfirst\fP, char **\fIlast\fP);
2524    .PP
2525    When a pattern is compiled with the PCRE_DUPNAMES option, names for subpatterns
2526    are not required to be unique. (Duplicate names are always allowed for
2527    subpatterns with the same number, created by using the (?| feature. Indeed, if
2528    such subpatterns are named, they are required to use the same names.)
2529    .P
2530    Normally, patterns with duplicate names are such that in any one match, only
2531    one of the named subpatterns participates. An example is shown in the
2532    .\" HREF
2533    \fBpcrepattern\fP
2534    .\"
2535    documentation.
2536    .P
2537    When duplicates are present, \fBpcre_copy_named_substring()\fP and
2538    \fBpcre_get_named_substring()\fP return the first substring corresponding to
2539    the given name that is set. If none are set, PCRE_ERROR_NOSUBSTRING (-7) is
2540    returned; no data is returned. The \fBpcre_get_stringnumber()\fP function
2541    returns one of the numbers that are associated with the name, but it is not
2542    defined which it is.
2543    .P
2544    If you want to get full details of all captured substrings for a given name,
2545    you must use the \fBpcre_get_stringtable_entries()\fP function. The first
2546    argument is the compiled pattern, and the second is the name. The third and
2547    fourth are pointers to variables which are updated by the function. After it
2548    has run, they point to the first and last entries in the name-to-number table
2549    for the given name. The function itself returns the length of each entry, or
2550    PCRE_ERROR_NOSUBSTRING (-7) if there are none. The format of the table is
2551    described above in the section entitled \fIInformation about a pattern\fP
2552    .\" HTML <a href="#infoaboutpattern">
2553    .\" </a>
2554    above.
2555    .\"
2556    Given all the relevant entries for the name, you can extract each of their
2557    numbers, and hence the captured data, if any.
2558    .
2559    .
2560    .SH "FINDING ALL POSSIBLE MATCHES"
2561    .rs
2562    .sp
2563    The traditional matching function uses a similar algorithm to Perl, which stops
2564    when it finds the first match, starting at a given point in the subject. If you
2565    want to find all possible matches, or the longest possible match, consider
2566    using the alternative matching function (see below) instead. If you cannot use
2567    the alternative function, but still need to find all possible matches, you
2568    can kludge it up by making use of the callout facility, which is described in
2569    the
2570    .\" HREF
2571    \fBpcrecallout\fP
2572    .\"
2573    documentation.
2574    .P
2575    What you have to do is to insert a callout right at the end of the pattern.
2576    When your callout function is called, extract and save the current matched
2577    substring. Then return 1, which forces \fBpcre_exec()\fP to backtrack and try
2578    other alternatives. Ultimately, when it runs out of matches, \fBpcre_exec()\fP
2579    will yield PCRE_ERROR_NOMATCH.
2580    .
2581    .
2582    .SH "OBTAINING AN ESTIMATE OF STACK USAGE"
2583    .rs
2584    .sp
2585    Matching certain patterns using \fBpcre_exec()\fP can use a lot of process
2586    stack, which in certain environments can be rather limited in size. Some users
2587    find it helpful to have an estimate of the amount of stack that is used by
2588    \fBpcre_exec()\fP, to help them set recursion limits, as described in the
2589    .\" HREF
2590    \fBpcrestack\fP
2591    .\"
2592    documentation. The estimate that is output by \fBpcretest\fP when called with
2593    the \fB-m\fP and \fB-C\fP options is obtained by calling \fBpcre_exec\fP with
2594    the values NULL, NULL, NULL, -999, and -999 for its first five arguments.
2595    .P
2596    Normally, if its first argument is NULL, \fBpcre_exec()\fP immediately returns
2597    the negative error code PCRE_ERROR_NULL, but with this special combination of
2598    arguments, it returns instead a negative number whose absolute value is the
2599    approximate stack frame size in bytes. (A negative number is used so that it is
2600    clear that no match has happened.) The value is approximate because in some
2601    cases, recursive calls to \fBpcre_exec()\fP occur when there are one or two
2602    additional variables on the stack.
2603    .P
2604    If PCRE has been compiled to use the heap instead of the stack for recursion,
2605    the value returned is the size of each block that is obtained from the heap.
2606    .
2607    .
2608    .\" HTML <a name="dfamatch"></a>
2609    .SH "MATCHING A PATTERN: THE ALTERNATIVE FUNCTION"
2610    .rs
2611    .sp
2612    .B int pcre_dfa_exec(const pcre *\fIcode\fP, "const pcre_extra *\fIextra\fP,"
2613    .ti +5n
2614    .B "const char *\fIsubject\fP," int \fIlength\fP, int \fIstartoffset\fP,
2615    .ti +5n
2616    .B int \fIoptions\fP, int *\fIovector\fP, int \fIovecsize\fP,
2617    .ti +5n
2618    .B int *\fIworkspace\fP, int \fIwscount\fP);
2619    .P
2620    The function \fBpcre_dfa_exec()\fP is called to match a subject string against
2621    a compiled pattern, using a matching algorithm that scans the subject string
2622    just once, and does not backtrack. This has different characteristics to the
2623    normal algorithm, and is not compatible with Perl. Some of the features of PCRE
2624    patterns are not supported. Nevertheless, there are times when this kind of
2625    matching can be useful. For a discussion of the two matching algorithms, and a
2626    list of features that \fBpcre_dfa_exec()\fP does not support, see the
2627    .\" HREF
2628    \fBpcrematching\fP
2629    .\"
2630    documentation.
2631    .P
2632    The arguments for the \fBpcre_dfa_exec()\fP function are the same as for
2633    \fBpcre_exec()\fP, plus two extras. The \fIovector\fP argument is used in a
2634    different way, and this is described below. The other common arguments are used
2635    in the same way as for \fBpcre_exec()\fP, so their description is not repeated
2636    here.
2637    .P
2638    The two additional arguments provide workspace for the function. The workspace
2639    vector should contain at least 20 elements. It is used for keeping track of
2640    multiple paths through the pattern tree. More workspace will be needed for
2641    patterns and subjects where there are a lot of potential matches.
2642    .P
2643    Here is an example of a simple call to \fBpcre_dfa_exec()\fP:
2644    .sp
2645      int rc;
2646      int ovector[10];
2647      int wspace[20];
2648      rc = pcre_dfa_exec(
2649        re,             /* result of pcre_compile() */
2650        NULL,           /* we didn't study the pattern */
2651        "some string",  /* the subject string */
2652        11,             /* the length of the subject string */
2653        0,              /* start at offset 0 in the subject */
2654        0,              /* default options */
2655        ovector,        /* vector of integers for substring information */
2656        10,             /* number of elements (NOT size in bytes) */
2657        wspace,         /* working space vector */
2658        20);            /* number of elements (NOT size in bytes) */
2659    .
2660    .SS "Option bits for \fBpcre_dfa_exec()\fP"
2661    .rs
2662    .sp
2663    The unused bits of the \fIoptions\fP argument for \fBpcre_dfa_exec()\fP must be
2664    zero. The only bits that may be set are PCRE_ANCHORED, PCRE_NEWLINE_\fIxxx\fP,
2665    PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY, PCRE_NOTEMPTY_ATSTART,
2666    PCRE_NO_UTF8_CHECK, PCRE_BSR_ANYCRLF, PCRE_BSR_UNICODE, PCRE_NO_START_OPTIMIZE,
2667    PCRE_PARTIAL_HARD, PCRE_PARTIAL_SOFT, PCRE_DFA_SHORTEST, and PCRE_DFA_RESTART.
2668    All but the last four of these are exactly the same as for \fBpcre_exec()\fP,
2669    so their description is not repeated here.
2670    .sp
2671      PCRE_PARTIAL_HARD
2672      PCRE_PARTIAL_SOFT
2673    .sp
2674    These have the same general effect as they do for \fBpcre_exec()\fP, but the
2675    details are slightly different. When PCRE_PARTIAL_HARD is set for
2676    \fBpcre_dfa_exec()\fP, it returns PCRE_ERROR_PARTIAL if the end of the subject
2677    is reached and there is still at least one matching possibility that requires
2678    additional characters. This happens even if some complete matches have also
2679    been found. When PCRE_PARTIAL_SOFT is set, the return code PCRE_ERROR_NOMATCH
2680    is converted into PCRE_ERROR_PARTIAL if the end of the subject is reached,
2681    there have been no complete matches, but there is still at least one matching
2682    possibility. The portion of the string that was inspected when the longest
2683    partial match was found is set as the first matching string in both cases.
2684    There is a more detailed discussion of partial and multi-segment matching, with
2685    examples, in the
2686    .\" HREF
2687    \fBpcrepartial\fP
2688    .\"
2689    documentation.
2690    .sp
2691      PCRE_DFA_SHORTEST
2692    .sp
2693    Setting the PCRE_DFA_SHORTEST option causes the matching algorithm to stop as
2694    soon as it has found one match. Because of the way the alternative algorithm
2695    works, this is necessarily the shortest possible match at the first possible
2696    matching point in the subject string.
2697    .sp
2698      PCRE_DFA_RESTART
2699    .sp
2700    When \fBpcre_dfa_exec()\fP returns a partial match, it is possible to call it
2701    again, with additional subject characters, and have it continue with the same
2702    match. The PCRE_DFA_RESTART option requests this action; when it is set, the
2703    \fIworkspace\fP and \fIwscount\fP options must reference the same vector as
2704    before because data about the match so far is left in them after a partial
2705    match. There is more discussion of this facility in the
2706    .\" HREF
2707    \fBpcrepartial\fP
2708    .\"
2709    documentation.
2710    .
2711    .
2712    .SS "Successful returns from \fBpcre_dfa_exec()\fP"
2713    .rs
2714    .sp
2715    When \fBpcre_dfa_exec()\fP succeeds, it may have matched more than one
2716    substring in the subject. Note, however, that all the matches from one run of
2717    the function start at the same point in the subject. The shorter matches are
2718    all initial substrings of the longer matches. For example, if the pattern
2719    .sp
2720      <.*>
2721    .sp
2722    is matched against the string
2723    .sp
2724      This is <something> <something else> <something further> no more
2725    .sp
2726    the three matched strings are
2727    .sp
2728      <something>
2729      <something> <something else>
2730      <something> <something else> <something further>
2731    .sp
2732    On success, the yield of the function is a number greater than zero, which is
2733    the number of matched substrings. The substrings themselves are returned in
2734    \fIovector\fP. Each string uses two elements; the first is the offset to the
2735    start, and the second is the offset to the end. In fact, all the strings have
2736    the same start offset. (Space could have been saved by giving this only once,
2737    but it was decided to retain some compatibility with the way \fBpcre_exec()\fP
2738    returns data, even though the meaning of the strings is different.)
2739    .P
2740    The strings are returned in reverse order of length; that is, the longest
2741    matching string is given first. If there were too many matches to fit into
2742    \fIovector\fP, the yield of the function is zero, and the vector is filled with
2743    the longest matches. Unlike \fBpcre_exec()\fP, \fBpcre_dfa_exec()\fP can use
2744    the entire \fIovector\fP for returning matched strings.
2745    .
2746    .
2747    .SS "Error returns from \fBpcre_dfa_exec()\fP"
2748    .rs
2749    .sp
2750    The \fBpcre_dfa_exec()\fP function returns a negative number when it fails.
2751    Many of the errors are the same as for \fBpcre_exec()\fP, and these are
2752    described
2753    .\" HTML <a href="#errorlist">
2754    .\" </a>
2755    above.
2756    .\"
2757    There are in addition the following errors that are specific to
2758    \fBpcre_dfa_exec()\fP:
2759    .sp
2760      PCRE_ERROR_DFA_UITEM      (-16)
2761    .sp
2762    This return is given if \fBpcre_dfa_exec()\fP encounters an item in the pattern
2763    that it does not support, for instance, the use of \eC or a back reference.
2764    .sp
2765      PCRE_ERROR_DFA_UCOND      (-17)
2766    .sp
2767    This return is given if \fBpcre_dfa_exec()\fP encounters a condition item that
2768    uses a back reference for the condition, or a test for recursion in a specific
2769    group. These are not supported.
2770    .sp
2771      PCRE_ERROR_DFA_UMLIMIT    (-18)
2772    .sp
2773    This return is given if \fBpcre_dfa_exec()\fP is called with an \fIextra\fP
2774    block that contains a setting of the \fImatch_limit\fP or
2775    \fImatch_limit_recursion\fP fields. This is not supported (these fields are
2776    meaningless for DFA matching).
2777    .sp
2778      PCRE_ERROR_DFA_WSSIZE     (-19)
2779    .sp
2780    This return is given if \fBpcre_dfa_exec()\fP runs out of space in the
2781    \fIworkspace\fP vector.
2782    .sp
2783      PCRE_ERROR_DFA_RECURSE    (-20)
2784    .sp
2785    When a recursive subpattern is processed, the matching function calls itself
2786    recursively, using private vectors for \fIovector\fP and \fIworkspace\fP. This
2787    error is given if the output vector is not large enough. This should be
2788    extremely rare, as a vector of size 1000 is used.
2789    .sp
2790      PCRE_ERROR_DFA_BADRESTART (-30)
2791    .sp
2792    When \fBpcre_dfa_exec()\fP is called with the \fBPCRE_DFA_RESTART\fP option,
2793    some plausibility checks are made on the contents of the workspace, which
2794    should contain data about the previous partial match. If any of these checks
2795    fail, this error is given.
2796    .
2797    .
2798    .SH "SEE ALSO"
2799    .rs
2800    .sp
2801    \fBpcre16\fP(3), \fBpcre32\fP(3), \fBpcrebuild\fP(3), \fBpcrecallout\fP(3),
2802    \fBpcrecpp(3)\fP(3), \fBpcrematching\fP(3), \fBpcrepartial\fP(3),
2803    \fBpcreposix\fP(3), \fBpcreprecompile\fP(3), \fBpcresample\fP(3),
2804    \fBpcrestack\fP(3).
2805    .
2806    .
2807    .SH AUTHOR
2808    .rs
2809    .sp
2810    .nf
2811    Philip Hazel
2812    University Computing Service
2813    Cambridge CB2 3QH, England.
2814    .fi
2815    .
2816    .
2817    .SH REVISION
2818    .rs
2819    .sp
2820    .nf
2821    Last updated: 31 October 2012
2822    Copyright (c) 1997-2012 University of Cambridge.
2823    .fi

Legend:
Removed from v.71  
changed lines
  Added in v.1194

  ViewVC Help
Powered by ViewVC 1.1.5