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1  .TH PCRE 3  .TH PCREAPI 3
2  .SH NAME  .SH NAME
3  PCRE - Perl-compatible regular expressions  PCRE - Perl-compatible regular expressions
4  .SH SYNOPSIS OF PCRE API  .SH "PCRE NATIVE API BASIC FUNCTIONS"
5  .rs  .rs
6  .sp  .sp
7  .B #include <pcre.h>  .B #include <pcre.h>
8  .PP  .PP
9  .SM  .SM
10  .br  .B pcre *pcre_compile(const char *\fIpattern\fP, int \fIoptions\fP,
 .B pcre *pcre_compile(const char *\fIpattern\fR, int \fIoptions\fR,  
11  .ti +5n  .ti +5n
12  .B const char **\fIerrptr\fR, int *\fIerroffset\fR,  .B const char **\fIerrptr\fP, int *\fIerroffset\fP,
13  .ti +5n  .ti +5n
14  .B const unsigned char *\fItableptr\fR);  .B const unsigned char *\fItableptr\fP);
15  .PP  .PP
16  .br  .B pcre *pcre_compile2(const char *\fIpattern\fP, int \fIoptions\fP,
 .B pcre_extra *pcre_study(const pcre *\fIcode\fR, int \fIoptions\fR,  
17  .ti +5n  .ti +5n
18  .B const char **\fIerrptr\fR);  .B int *\fIerrorcodeptr\fP,
19    .ti +5n
20    .B const char **\fIerrptr\fP, int *\fIerroffset\fP,
21    .ti +5n
22    .B const unsigned char *\fItableptr\fP);
23    .PP
24    .B pcre_extra *pcre_study(const pcre *\fIcode\fP, int \fIoptions\fP,
25    .ti +5n
26    .B const char **\fIerrptr\fP);
27    .PP
28    .B void pcre_free_study(pcre_extra *\fIextra\fP);
29    .PP
30    .B int pcre_exec(const pcre *\fIcode\fP, "const pcre_extra *\fIextra\fP,"
31    .ti +5n
32    .B "const char *\fIsubject\fP," int \fIlength\fP, int \fIstartoffset\fP,
33    .ti +5n
34    .B int \fIoptions\fP, int *\fIovector\fP, int \fIovecsize\fP);
35    .
36    .
37    .SH "PCRE NATIVE API AUXILIARY FUNCTIONS"
38    .rs
39    .sp
40    .B pcre_jit_stack *pcre_jit_stack_alloc(int \fIstartsize\fP, int \fImaxsize\fP);
41    .PP
42    .B void pcre_jit_stack_free(pcre_jit_stack *\fIstack\fP);
43    .PP
44    .B void pcre_assign_jit_stack(pcre_extra *\fIextra\fP,
45    .ti +5n
46    .B pcre_jit_callback \fIcallback\fP, void *\fIdata\fP);
47  .PP  .PP
48  .br  .B int pcre_dfa_exec(const pcre *\fIcode\fP, "const pcre_extra *\fIextra\fP,"
49  .B int pcre_exec(const pcre *\fIcode\fR, "const pcre_extra *\fIextra\fR,"  .ti +5n
50    .B "const char *\fIsubject\fP," int \fIlength\fP, int \fIstartoffset\fP,
51  .ti +5n  .ti +5n
52  .B "const char *\fIsubject\fR," int \fIlength\fR, int \fIstartoffset\fR,  .B int \fIoptions\fP, int *\fIovector\fP, int \fIovecsize\fP,
53  .ti +5n  .ti +5n
54  .B int \fIoptions\fR, int *\fIovector\fR, int \fIovecsize\fR);  .B int *\fIworkspace\fP, int \fIwscount\fP);
55  .PP  .PP
56  .br  .B int pcre_copy_named_substring(const pcre *\fIcode\fP,
 .B int pcre_copy_named_substring(const pcre *\fIcode\fR,  
57  .ti +5n  .ti +5n
58  .B const char *\fIsubject\fR, int *\fIovector\fR,  .B const char *\fIsubject\fP, int *\fIovector\fP,
59  .ti +5n  .ti +5n
60  .B int \fIstringcount\fR, const char *\fIstringname\fR,  .B int \fIstringcount\fP, const char *\fIstringname\fP,
61  .ti +5n  .ti +5n
62  .B char *\fIbuffer\fR, int \fIbuffersize\fR);  .B char *\fIbuffer\fP, int \fIbuffersize\fP);
63  .PP  .PP
64  .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,  
65  .ti +5n  .ti +5n
66  .B int \fIstringcount\fR, int \fIstringnumber\fR, char *\fIbuffer\fR,  .B int \fIstringcount\fP, int \fIstringnumber\fP, char *\fIbuffer\fP,
67  .ti +5n  .ti +5n
68  .B int \fIbuffersize\fR);  .B int \fIbuffersize\fP);
69  .PP  .PP
70  .br  .B int pcre_get_named_substring(const pcre *\fIcode\fP,
 .B int pcre_get_named_substring(const pcre *\fIcode\fR,  
71  .ti +5n  .ti +5n
72  .B const char *\fIsubject\fR, int *\fIovector\fR,  .B const char *\fIsubject\fP, int *\fIovector\fP,
73  .ti +5n  .ti +5n
74  .B int \fIstringcount\fR, const char *\fIstringname\fR,  .B int \fIstringcount\fP, const char *\fIstringname\fP,
75    .ti +5n
76    .B const char **\fIstringptr\fP);
77    .PP
78    .B int pcre_get_stringnumber(const pcre *\fIcode\fP,
79  .ti +5n  .ti +5n
80  .B const char **\fIstringptr\fR);  .B const char *\fIname\fP);
81  .PP  .PP
82  .br  .B int pcre_get_stringtable_entries(const pcre *\fIcode\fP,
 .B int pcre_get_stringnumber(const pcre *\fIcode\fR,  
83  .ti +5n  .ti +5n
84  .B const char *\fIname\fR);  .B const char *\fIname\fP, char **\fIfirst\fP, char **\fIlast\fP);
85  .PP  .PP
86  .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,  
87  .ti +5n  .ti +5n
88  .B int \fIstringcount\fR, int \fIstringnumber\fR,  .B int \fIstringcount\fP, int \fIstringnumber\fP,
89  .ti +5n  .ti +5n
90  .B const char **\fIstringptr\fR);  .B const char **\fIstringptr\fP);
91  .PP  .PP
92  .br  .B int pcre_get_substring_list(const char *\fIsubject\fP,
 .B int pcre_get_substring_list(const char *\fIsubject\fR,  
93  .ti +5n  .ti +5n
94  .B int *\fIovector\fR, int \fIstringcount\fR, "const char ***\fIlistptr\fR);"  .B int *\fIovector\fP, int \fIstringcount\fP, "const char ***\fIlistptr\fP);"
95  .PP  .PP
96  .br  .B void pcre_free_substring(const char *\fIstringptr\fP);
 .B void pcre_free_substring(const char *\fIstringptr\fR);  
97  .PP  .PP
98  .br  .B void pcre_free_substring_list(const char **\fIstringptr\fP);
 .B void pcre_free_substring_list(const char **\fIstringptr\fR);  
99  .PP  .PP
 .br  
100  .B const unsigned char *pcre_maketables(void);  .B const unsigned char *pcre_maketables(void);
101  .PP  .PP
102  .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,"  
103  .ti +5n  .ti +5n
104  .B int \fIwhat\fR, void *\fIwhere\fR);  .B int \fIwhat\fP, void *\fIwhere\fP);
105  .PP  .PP
106  .br  .B int pcre_info(const pcre *\fIcode\fP, int *\fIoptptr\fP, int
107  .B int pcre_info(const pcre *\fIcode\fR, int *\fIoptptr\fR, int  .B *\fIfirstcharptr\fP);
 .B *\fIfirstcharptr\fR);  
108  .PP  .PP
109  .br  .B int pcre_refcount(pcre *\fIcode\fP, int \fIadjust\fP);
 .B int pcre_config(int \fIwhat\fR, void *\fIwhere\fR);  
110  .PP  .PP
111  .br  .B int pcre_config(int \fIwhat\fP, void *\fIwhere\fP);
 .B char *pcre_version(void);  
112  .PP  .PP
113  .br  .B char *pcre_version(void);
114    .
115    .
116    .SH "PCRE NATIVE API INDIRECTED FUNCTIONS"
117    .rs
118    .sp
119  .B void *(*pcre_malloc)(size_t);  .B void *(*pcre_malloc)(size_t);
120  .PP  .PP
 .br  
121  .B void (*pcre_free)(void *);  .B void (*pcre_free)(void *);
122  .PP  .PP
 .br  
123  .B void *(*pcre_stack_malloc)(size_t);  .B void *(*pcre_stack_malloc)(size_t);
124  .PP  .PP
 .br  
125  .B void (*pcre_stack_free)(void *);  .B void (*pcre_stack_free)(void *);
126  .PP  .PP
 .br  
127  .B int (*pcre_callout)(pcre_callout_block *);  .B int (*pcre_callout)(pcre_callout_block *);
128    .
129  .SH PCRE API  .
130    .SH "PCRE API OVERVIEW"
131  .rs  .rs
132  .sp  .sp
133  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
134  a set of wrapper functions that correspond to the POSIX regular expression API.  also some wrapper functions that correspond to the POSIX regular expression
135  These are described in the \fBpcreposix\fR documentation.  API, but they do not give access to all the functionality. They are described
136    in the
137  The native API function prototypes are defined in the header file \fBpcre.h\fR,  .\" HREF
138  and on Unix systems the library itself is called \fBlibpcre.a\fR, so can be  \fBpcreposix\fP
139  accessed by adding \fB-lpcre\fR to the command for linking an application which  .\"
140  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++
141  contain the major and minor release numbers for the library. Applications can  wrapper is also distributed with PCRE. It is documented in the
142  use these to include support for different releases.  .\" HREF
143    \fBpcrecpp\fP
144  The functions \fBpcre_compile()\fR, \fBpcre_study()\fR, and \fBpcre_exec()\fR  .\"
145  are used for compiling and matching regular expressions. A sample program that  page.
146  demonstrates the simplest way of using them is given in the file  .P
147  \fIpcredemo.c\fR. The \fBpcresample\fR documentation describes how to run it.  The native API C function prototypes are defined in the header file
148    \fBpcre.h\fP, and on Unix systems the library itself is called \fBlibpcre\fP.
149  There are convenience functions for extracting captured substrings from a  It can normally be accessed by adding \fB-lpcre\fP to the command for linking
150  matched subject string. They are:  an application that uses PCRE. The header file defines the macros PCRE_MAJOR
151    and PCRE_MINOR to contain the major and minor release numbers for the library.
152    \fBpcre_copy_substring()\fR  Applications can use these to include support for different releases of PCRE.
153    \fBpcre_copy_named_substring()\fR  .P
154    \fBpcre_get_substring()\fR  In a Windows environment, if you want to statically link an application program
155    \fBpcre_get_named_substring()\fR  against a non-dll \fBpcre.a\fP file, you must define PCRE_STATIC before
156    \fBpcre_get_substring_list()\fR  including \fBpcre.h\fP or \fBpcrecpp.h\fP, because otherwise the
157    \fBpcre_malloc()\fP and \fBpcre_free()\fP exported functions will be declared
158  \fBpcre_free_substring()\fR and \fBpcre_free_substring_list()\fR are also  \fB__declspec(dllimport)\fP, with unwanted results.
159    .P
160    The functions \fBpcre_compile()\fP, \fBpcre_compile2()\fP, \fBpcre_study()\fP,
161    and \fBpcre_exec()\fP are used for compiling and matching regular expressions
162    in a Perl-compatible manner. A sample program that demonstrates the simplest
163    way of using them is provided in the file called \fIpcredemo.c\fP in the PCRE
164    source distribution. A listing of this program is given in the
165    .\" HREF
166    \fBpcredemo\fP
167    .\"
168    documentation, and the
169    .\" HREF
170    \fBpcresample\fP
171    .\"
172    documentation describes how to compile and run it.
173    .P
174    Just-in-time compiler support is an optional feature of PCRE that can be built
175    in appropriate hardware environments. It greatly speeds up the matching
176    performance of many patterns. Simple programs can easily request that it be
177    used if available, by setting an option that is ignored when it is not
178    relevant. More complicated programs might need to make use of the functions
179    \fBpcre_jit_stack_alloc()\fP, \fBpcre_jit_stack_free()\fP, and
180    \fBpcre_assign_jit_stack()\fP in order to control the JIT code's memory usage.
181    These functions are discussed in the
182    .\" HREF
183    \fBpcrejit\fP
184    .\"
185    documentation.
186    .P
187    A second matching function, \fBpcre_dfa_exec()\fP, which is not
188    Perl-compatible, is also provided. This uses a different algorithm for the
189    matching. The alternative algorithm finds all possible matches (at a given
190    point in the subject), and scans the subject just once (unless there are
191    lookbehind assertions). However, this algorithm does not return captured
192    substrings. A description of the two matching algorithms and their advantages
193    and disadvantages is given in the
194    .\" HREF
195    \fBpcrematching\fP
196    .\"
197    documentation.
198    .P
199    In addition to the main compiling and matching functions, there are convenience
200    functions for extracting captured substrings from a subject string that is
201    matched by \fBpcre_exec()\fP. They are:
202    .sp
203      \fBpcre_copy_substring()\fP
204      \fBpcre_copy_named_substring()\fP
205      \fBpcre_get_substring()\fP
206      \fBpcre_get_named_substring()\fP
207      \fBpcre_get_substring_list()\fP
208      \fBpcre_get_stringnumber()\fP
209      \fBpcre_get_stringtable_entries()\fP
210    .sp
211    \fBpcre_free_substring()\fP and \fBpcre_free_substring_list()\fP are also
212  provided, to free the memory used for extracted strings.  provided, to free the memory used for extracted strings.
213    .P
214  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
215  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,
216    or \fBpcre_dfa_exec()\fP. This is an optional facility that is provided for
217  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
218  compiled pattern; \fBpcre_info()\fR is an obsolete version which returns only  internal tables that are generated when PCRE is built are used.
219    .P
220    The function \fBpcre_fullinfo()\fP is used to find out information about a
221    compiled pattern; \fBpcre_info()\fP is an obsolete version that returns only
222  some of the available information, but is retained for backwards compatibility.  some of the available information, but is retained for backwards compatibility.
223  The function \fBpcre_version()\fR returns a pointer to a string containing the  The function \fBpcre_version()\fP returns a pointer to a string containing the
224  version of PCRE and its date of release.  version of PCRE and its date of release.
225    .P
226  The global variables \fBpcre_malloc\fR and \fBpcre_free\fR initially contain  The function \fBpcre_refcount()\fP maintains a reference count in a data block
227  the entry points of the standard \fBmalloc()\fR and \fBfree()\fR functions  containing a compiled pattern. This is provided for the benefit of
228    object-oriented applications.
229    .P
230    The global variables \fBpcre_malloc\fP and \fBpcre_free\fP initially contain
231    the entry points of the standard \fBmalloc()\fP and \fBfree()\fP functions,
232  respectively. PCRE calls the memory management functions via these variables,  respectively. PCRE calls the memory management functions via these variables,
233  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
234  should be done before calling any PCRE functions.  should be done before calling any PCRE functions.
235    .P
236  The global variables \fBpcre_stack_malloc\fR and \fBpcre_stack_free\fR are also  The global variables \fBpcre_stack_malloc\fP and \fBpcre_stack_free\fP are also
237  indirections to memory management functions. These special functions are used  indirections to memory management functions. These special functions are used
238  only when PCRE is compiled to use the heap for remembering data, instead of  only when PCRE is compiled to use the heap for remembering data, instead of
239  recursive function calls. This is a non-standard way of building PCRE, for use  recursive function calls, when running the \fBpcre_exec()\fP function. See the
240  in environments that have limited stacks. Because of the greater use of memory  .\" HREF
241  management, it runs more slowly. Separate functions are provided so that  \fBpcrebuild\fP
242  special-purpose external code can be used for this case. When used, these  .\"
243  functions are always called in a stack-like manner (last obtained, first  documentation for details of how to do this. It is a non-standard way of
244  freed), and always for memory blocks of the same size.  building PCRE, for use in environments that have limited stacks. Because of the
245    greater use of memory management, it runs more slowly. Separate functions are
246  The global variable \fBpcre_callout\fR initially contains NULL. It can be set  provided so that special-purpose external code can be used for this case. When
247    used, these functions are always called in a stack-like manner (last obtained,
248    first freed), and always for memory blocks of the same size. There is a
249    discussion about PCRE's stack usage in the
250    .\" HREF
251    \fBpcrestack\fP
252    .\"
253    documentation.
254    .P
255    The global variable \fBpcre_callout\fP initially contains NULL. It can be set
256  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
257  points during a matching operation. Details are given in the \fBpcrecallout\fR  points during a matching operation. Details are given in the
258    .\" HREF
259    \fBpcrecallout\fP
260    .\"
261  documentation.  documentation.
262    .
263    .
264    .\" HTML <a name="newlines"></a>
265    .SH NEWLINES
266    .rs
267    .sp
268    PCRE supports five different conventions for indicating line breaks in
269    strings: a single CR (carriage return) character, a single LF (linefeed)
270    character, the two-character sequence CRLF, any of the three preceding, or any
271    Unicode newline sequence. The Unicode newline sequences are the three just
272    mentioned, plus the single characters VT (vertical tab, U+000B), FF (formfeed,
273    U+000C), NEL (next line, U+0085), LS (line separator, U+2028), and PS
274    (paragraph separator, U+2029).
275    .P
276    Each of the first three conventions is used by at least one operating system as
277    its standard newline sequence. When PCRE is built, a default can be specified.
278    The default default is LF, which is the Unix standard. When PCRE is run, the
279    default can be overridden, either when a pattern is compiled, or when it is
280    matched.
281    .P
282    At compile time, the newline convention can be specified by the \fIoptions\fP
283    argument of \fBpcre_compile()\fP, or it can be specified by special text at the
284    start of the pattern itself; this overrides any other settings. See the
285    .\" HREF
286    \fBpcrepattern\fP
287    .\"
288    page for details of the special character sequences.
289    .P
290    In the PCRE documentation the word "newline" is used to mean "the character or
291    pair of characters that indicate a line break". The choice of newline
292    convention affects the handling of the dot, circumflex, and dollar
293    metacharacters, the handling of #-comments in /x mode, and, when CRLF is a
294    recognized line ending sequence, the match position advancement for a
295    non-anchored pattern. There is more detail about this in the
296    .\" HTML <a href="#execoptions">
297    .\" </a>
298    section on \fBpcre_exec()\fP options
299    .\"
300    below.
301    .P
302    The choice of newline convention does not affect the interpretation of
303    the \en or \er escape sequences, nor does it affect what \eR matches, which is
304    controlled in a similar way, but by separate options.
305    .
306    .
307  .SH MULTITHREADING  .SH MULTITHREADING
308  .rs  .rs
309  .sp  .sp
310  The PCRE functions can be used in multi-threading applications, with the  The PCRE functions can be used in multi-threading applications, with the
311  proviso that the memory management functions pointed to by \fBpcre_malloc\fR,  proviso that the memory management functions pointed to by \fBpcre_malloc\fP,
312  \fBpcre_free\fR, \fBpcre_stack_malloc\fR, and \fBpcre_stack_free\fR, and the  \fBpcre_free\fP, \fBpcre_stack_malloc\fP, and \fBpcre_stack_free\fP, and the
313  callout function pointed to by \fBpcre_callout\fR, are shared by all threads.  callout function pointed to by \fBpcre_callout\fP, are shared by all threads.
314    .P
315  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
316  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.
317    .P
318  .SH CHECKING BUILD-TIME OPTIONS  If the just-in-time optimization feature is being used, it needs separate
319    memory stack areas for each thread. See the
320    .\" HREF
321    \fBpcrejit\fP
322    .\"
323    documentation for more details.
324    .
325    .
326    .SH "SAVING PRECOMPILED PATTERNS FOR LATER USE"
327  .rs  .rs
328  .sp  .sp
329  .B int pcre_config(int \fIwhat\fR, void *\fIwhere\fR);  The compiled form of a regular expression can be saved and re-used at a later
330    time, possibly by a different program, and even on a host other than the one on
331    which it was compiled. Details are given in the
332    .\" HREF
333    \fBpcreprecompile\fP
334    .\"
335    documentation. However, compiling a regular expression with one version of PCRE
336    for use with a different version is not guaranteed to work and may cause
337    crashes.
338    .
339    .
340    .SH "CHECKING BUILD-TIME OPTIONS"
341    .rs
342    .sp
343    .B int pcre_config(int \fIwhat\fP, void *\fIwhere\fP);
344  .PP  .PP
345  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
346  discover which optional features have been compiled into the PCRE library. The  discover which optional features have been compiled into the PCRE library. The
347  .\" HREF  .\" HREF
348  \fBpcrebuild\fR  \fBpcrebuild\fP
349  .\"  .\"
350  documentation has more details about these optional features.  documentation has more details about these optional features.
351    .P
352  The first argument for \fBpcre_config()\fR is an integer, specifying which  The first argument for \fBpcre_config()\fP is an integer, specifying which
353  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
354  which the information is placed. The following information is available:  which the information is placed. The following information is available:
355    .sp
356    PCRE_CONFIG_UTF8    PCRE_CONFIG_UTF8
357    .sp
358  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;
359  otherwise it is set to zero.  otherwise it is set to zero.
360    .sp
361      PCRE_CONFIG_UNICODE_PROPERTIES
362    .sp
363    The output is an integer that is set to one if support for Unicode character
364    properties is available; otherwise it is set to zero.
365    .sp
366      PCRE_CONFIG_JIT
367    .sp
368    The output is an integer that is set to one if support for just-in-time
369    compiling is available; otherwise it is set to zero.
370    .sp
371    PCRE_CONFIG_NEWLINE    PCRE_CONFIG_NEWLINE
372    .sp
373  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
374  the newline character. It is either linefeed (10) or carriage return (13), and  that is recognized as meaning "newline". The four values that are supported
375  should normally be the standard character for your operating system.  are: 10 for LF, 13 for CR, 3338 for CRLF, -2 for ANYCRLF, and -1 for ANY.
376    Though they are derived from ASCII, the same values are returned in EBCDIC
377    environments. The default should normally correspond to the standard sequence
378    for your operating system.
379    .sp
380      PCRE_CONFIG_BSR
381    .sp
382    The output is an integer whose value indicates what character sequences the \eR
383    escape sequence matches by default. A value of 0 means that \eR matches any
384    Unicode line ending sequence; a value of 1 means that \eR matches only CR, LF,
385    or CRLF. The default can be overridden when a pattern is compiled or matched.
386    .sp
387    PCRE_CONFIG_LINK_SIZE    PCRE_CONFIG_LINK_SIZE
388    .sp
389  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
390  linkage in compiled regular expressions. The value is 2, 3, or 4. Larger values  linkage in compiled regular expressions. The value is 2, 3, or 4. Larger values
391  allow larger regular expressions to be compiled, at the expense of slower  allow larger regular expressions to be compiled, at the expense of slower
392  matching. The default value of 2 is sufficient for all but the most massive  matching. The default value of 2 is sufficient for all but the most massive
393  patterns, since it allows the compiled pattern to be up to 64K in size.  patterns, since it allows the compiled pattern to be up to 64K in size.
394    .sp
395    PCRE_CONFIG_POSIX_MALLOC_THRESHOLD    PCRE_CONFIG_POSIX_MALLOC_THRESHOLD
396    .sp
397  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
398  interface uses \fBmalloc()\fR for output vectors. Further details are given in  interface uses \fBmalloc()\fP for output vectors. Further details are given in
399  the \fBpcreposix\fR documentation.  the
400    .\" HREF
401    \fBpcreposix\fP
402    .\"
403    documentation.
404    .sp
405    PCRE_CONFIG_MATCH_LIMIT    PCRE_CONFIG_MATCH_LIMIT
406    .sp
407  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
408  internal matching function calls in a \fBpcre_exec()\fR execution. Further  internal matching function calls in a \fBpcre_exec()\fP execution. Further
409  details are given with \fBpcre_exec()\fR below.  details are given with \fBpcre_exec()\fP below.
410    .sp
411      PCRE_CONFIG_MATCH_LIMIT_RECURSION
412    .sp
413    The output is a long integer that gives the default limit for the depth of
414    recursion when calling the internal matching function in a \fBpcre_exec()\fP
415    execution. Further details are given with \fBpcre_exec()\fP below.
416    .sp
417    PCRE_CONFIG_STACKRECURSE    PCRE_CONFIG_STACKRECURSE
418    .sp
419  The output is an integer that is set to one if internal recursion is  The output is an integer that is set to one if internal recursion when running
420  implemented by recursive function calls that use the stack to remember their  \fBpcre_exec()\fP is implemented by recursive function calls that use the stack
421  state. This is the usual way that PCRE is compiled. The output is zero if PCRE  to remember their state. This is the usual way that PCRE is compiled. The
422  was compiled to use blocks of data on the heap instead of recursive function  output is zero if PCRE was compiled to use blocks of data on the heap instead
423  calls. In this case, \fBpcre_stack_malloc\fR and \fBpcre_stack_free\fR are  of recursive function calls. In this case, \fBpcre_stack_malloc\fP and
424  called to manage memory blocks on the heap, thus avoiding the use of the stack.  \fBpcre_stack_free\fP are called to manage memory blocks on the heap, thus
425    avoiding the use of the stack.
426  .SH COMPILING A PATTERN  .
427  .rs  .
428  .sp  .SH "COMPILING A PATTERN"
429  .B pcre *pcre_compile(const char *\fIpattern\fR, int \fIoptions\fR,  .rs
430  .ti +5n  .sp
431  .B const char **\fIerrptr\fR, int *\fIerroffset\fR,  .B pcre *pcre_compile(const char *\fIpattern\fP, int \fIoptions\fP,
432  .ti +5n  .ti +5n
433  .B const unsigned char *\fItableptr\fR);  .B const char **\fIerrptr\fP, int *\fIerroffset\fP,
434  .PP  .ti +5n
435    .B const unsigned char *\fItableptr\fP);
436  The function \fBpcre_compile()\fR is called to compile a pattern into an  .sp
437  internal form. The pattern is a C string terminated by a binary zero, and  .B pcre *pcre_compile2(const char *\fIpattern\fP, int \fIoptions\fP,
438  is passed in the argument \fIpattern\fR. A pointer to a single block of memory  .ti +5n
439  that is obtained via \fBpcre_malloc\fR is returned. This contains the compiled  .B int *\fIerrorcodeptr\fP,
440  code and related data. The \fBpcre\fR type is defined for the returned block;  .ti +5n
441  this is a typedef for a structure whose contents are not externally defined. It  .B const char **\fIerrptr\fP, int *\fIerroffset\fP,
442  is up to the caller to free the memory when it is no longer required.  .ti +5n
443    .B const unsigned char *\fItableptr\fP);
444    .P
445    Either of the functions \fBpcre_compile()\fP or \fBpcre_compile2()\fP can be
446    called to compile a pattern into an internal form. The only difference between
447    the two interfaces is that \fBpcre_compile2()\fP has an additional argument,
448    \fIerrorcodeptr\fP, via which a numerical error code can be returned. To avoid
449    too much repetition, we refer just to \fBpcre_compile()\fP below, but the
450    information applies equally to \fBpcre_compile2()\fP.
451    .P
452    The pattern is a C string terminated by a binary zero, and is passed in the
453    \fIpattern\fP argument. A pointer to a single block of memory that is obtained
454    via \fBpcre_malloc\fP is returned. This contains the compiled code and related
455    data. The \fBpcre\fP type is defined for the returned block; this is a typedef
456    for a structure whose contents are not externally defined. It is up to the
457    caller to free the memory (via \fBpcre_free\fP) when it is no longer required.
458    .P
459  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
460  depend on memory location, the complete \fBpcre\fR data block is not  depend on memory location, the complete \fBpcre\fP data block is not
461  fully relocatable, because it contains a copy of the \fItableptr\fR argument,  fully relocatable, because it may contain a copy of the \fItableptr\fP
462  which is an address (see below).  argument, which is an address (see below).
463    .P
464  The \fIoptions\fR argument contains independent bits that affect the  The \fIoptions\fP argument contains various bit settings that affect the
465  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
466  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
467  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
468  in the \fBpcrepattern\fR documentation). For these options, the contents of the  within the pattern (see the detailed description in the
469  \fIoptions\fR argument specifies their initial settings at the start of  .\" HREF
470  compilation and execution. The PCRE_ANCHORED option can be set at the time of  \fBpcrepattern\fP
471  matching as well as at compile time.  .\"
472    documentation). For those options that can be different in different parts of
473  If \fIerrptr\fR is NULL, \fBpcre_compile()\fR returns NULL immediately.  the pattern, the contents of the \fIoptions\fP argument specifies their
474  Otherwise, if compilation of a pattern fails, \fBpcre_compile()\fR returns  settings at the start of compilation and execution. The PCRE_ANCHORED,
475  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
476  error message. The offset from the start of the pattern to the character where  PCRE_NO_START_OPT options can be set at the time of matching as well as at
477  the error was discovered is placed in the variable pointed to by  compile time.
478  \fIerroffset\fR, which must not be NULL. If it is, an immediate error is given.  .P
479    If \fIerrptr\fP is NULL, \fBpcre_compile()\fP returns NULL immediately.
480  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
481  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
482  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
483  \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
484    byte that was being processed when the error was discovered is placed in the
485  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
486    immediate error is given). However, for an invalid UTF-8 string, the offset is
487    that of the first byte of the failing character. Also, some errors are not
488    detected until checks are carried out when the whole pattern has been scanned;
489    in these cases the offset passed back is the length of the pattern.
490    .P
491    Note that the offset is in bytes, not characters, even in UTF-8 mode. It may
492    sometimes point into the middle of a UTF-8 character.
493    .P
494    If \fBpcre_compile2()\fP is used instead of \fBpcre_compile()\fP, and the
495    \fIerrorcodeptr\fP argument is not NULL, a non-zero error code number is
496    returned via this argument in the event of an error. This is in addition to the
497    textual error message. Error codes and messages are listed below.
498    .P
499    If the final argument, \fItableptr\fP, is NULL, PCRE uses a default set of
500    character tables that are built when PCRE is compiled, using the default C
501    locale. Otherwise, \fItableptr\fP must be an address that is the result of a
502    call to \fBpcre_maketables()\fP. This value is stored with the compiled
503    pattern, and used again by \fBpcre_exec()\fP, unless another table pointer is
504    passed to it. For more discussion, see the section on locale support below.
505    .P
506    This code fragment shows a typical straightforward call to \fBpcre_compile()\fP:
507    .sp
508    pcre *re;    pcre *re;
509    const char *error;    const char *error;
510    int erroffset;    int erroffset;
# Line 290  This code fragment shows a typical strai Line 514  This code fragment shows a typical strai
514      &error,           /* for error message */      &error,           /* for error message */
515      &erroffset,       /* for error offset */      &erroffset,       /* for error offset */
516      NULL);            /* use default character tables */      NULL);            /* use default character tables */
517    .sp
518  The following option bits are defined:  The following names for option bits are defined in the \fBpcre.h\fP header
519    file:
520    .sp
521    PCRE_ANCHORED    PCRE_ANCHORED
522    .sp
523  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
524  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
525  being searched (the "subject string"). This effect can also be achieved by  being searched (the "subject string"). This effect can also be achieved by
526  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
527  Perl.  Perl.
528    .sp
529      PCRE_AUTO_CALLOUT
530    .sp
531    If this bit is set, \fBpcre_compile()\fP automatically inserts callout items,
532    all with number 255, before each pattern item. For discussion of the callout
533    facility, see the
534    .\" HREF
535    \fBpcrecallout\fP
536    .\"
537    documentation.
538    .sp
539      PCRE_BSR_ANYCRLF
540      PCRE_BSR_UNICODE
541    .sp
542    These options (which are mutually exclusive) control what the \eR escape
543    sequence matches. The choice is either to match only CR, LF, or CRLF, or to
544    match any Unicode newline sequence. The default is specified when PCRE is
545    built. It can be overridden from within the pattern, or by setting an option
546    when a compiled pattern is matched.
547    .sp
548    PCRE_CASELESS    PCRE_CASELESS
549    .sp
550  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
551  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
552  pattern by a (?i) option setting.  pattern by a (?i) option setting. In UTF-8 mode, PCRE always understands the
553    concept of case for characters whose values are less than 128, so caseless
554    matching is always possible. For characters with higher values, the concept of
555    case is supported if PCRE is compiled with Unicode property support, but not
556    otherwise. If you want to use caseless matching for characters 128 and above,
557    you must ensure that PCRE is compiled with Unicode property support as well as
558    with UTF-8 support.
559    .sp
560    PCRE_DOLLAR_ENDONLY    PCRE_DOLLAR_ENDONLY
561    .sp
562  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
563  end of the subject string. Without this option, a dollar also matches  end of the subject string. Without this option, a dollar also matches
564  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
565  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.
566  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
567  a pattern.  pattern.
568    .sp
569    PCRE_DOTALL    PCRE_DOTALL
570    .sp
571  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
572  including newlines. Without it, newlines are excluded. This option is  any value, including one that indicates a newline. However, it only ever
573    matches one character, even if newlines are coded as CRLF. Without this option,
574    a dot does not match when the current position is at a newline. This option is
575  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
576  (?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
577  character, independent of the setting of this option.  characters, independent of the setting of this option.
578    .sp
579      PCRE_DUPNAMES
580    .sp
581    If this bit is set, names used to identify capturing subpatterns need not be
582    unique. This can be helpful for certain types of pattern when it is known that
583    only one instance of the named subpattern can ever be matched. There are more
584    details of named subpatterns below; see also the
585    .\" HREF
586    \fBpcrepattern\fP
587    .\"
588    documentation.
589    .sp
590    PCRE_EXTENDED    PCRE_EXTENDED
591    .sp
592  If this bit is set, whitespace data characters in the pattern are totally  If this bit is set, whitespace data characters in the pattern are totally
593  ignored except when escaped or inside a character class. Whitespace does not  ignored except when escaped or inside a character class. Whitespace does not
594  include the VT character (code 11). In addition, characters between an  include the VT character (code 11). In addition, characters between an
595  unescaped # outside a character class and the next newline character,  unescaped # outside a character class and the next newline, inclusive, are also
596  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
597  be changed within a pattern by a (?x) option setting.  pattern by a (?x) option setting.
598    .P
599    Which characters are interpreted as newlines is controlled by the options
600    passed to \fBpcre_compile()\fP or by a special sequence at the start of the
601    pattern, as described in the section entitled
602    .\" HTML <a href="pcrepattern.html#newlines">
603    .\" </a>
604    "Newline conventions"
605    .\"
606    in the \fBpcrepattern\fP documentation. Note that the end of this type of
607    comment is a literal newline sequence in the pattern; escape sequences that
608    happen to represent a newline do not count.
609    .P
610  This option makes it possible to include comments inside complicated patterns.  This option makes it possible to include comments inside complicated patterns.
611  Note, however, that this applies only to data characters. Whitespace characters  Note, however, that this applies only to data characters. Whitespace characters
612  may never appear within special character sequences in a pattern, for example  may never appear within special character sequences in a pattern, for example
613  within the sequence (?( which introduces a conditional subpattern.  within the sequence (?( that introduces a conditional subpattern.
614    .sp
615    PCRE_EXTRA    PCRE_EXTRA
616    .sp
617  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
618  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
619  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
620  special meaning causes an error, thus reserving these combinations for future  special meaning causes an error, thus reserving these combinations for future
621  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
622  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
623  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
624  pattern.  no other features controlled by this option. It can also be set by a (?X)
625    option setting within a pattern.
626    .sp
627      PCRE_FIRSTLINE
628    .sp
629    If this option is set, an unanchored pattern is required to match before or at
630    the first newline in the subject string, though the matched text may continue
631    over the newline.
632    .sp
633      PCRE_JAVASCRIPT_COMPAT
634    .sp
635    If this option is set, PCRE's behaviour is changed in some ways so that it is
636    compatible with JavaScript rather than Perl. The changes are as follows:
637    .P
638    (1) A lone closing square bracket in a pattern causes a compile-time error,
639    because this is illegal in JavaScript (by default it is treated as a data
640    character). Thus, the pattern AB]CD becomes illegal when this option is set.
641    .P
642    (2) At run time, a back reference to an unset subpattern group matches an empty
643    string (by default this causes the current matching alternative to fail). A
644    pattern such as (\e1)(a) succeeds when this option is set (assuming it can find
645    an "a" in the subject), whereas it fails by default, for Perl compatibility.
646    .P
647    (3) \eU matches an upper case "U" character; by default \eU causes a compile
648    time error (Perl uses \eU to upper case subsequent characters).
649    .P
650    (4) \eu matches a lower case "u" character unless it is followed by four
651    hexadecimal digits, in which case the hexadecimal number defines the code point
652    to match. By default, \eu causes a compile time error (Perl uses it to upper
653    case the following character).
654    .P
655    (5) \ex matches a lower case "x" character unless it is followed by two
656    hexadecimal digits, in which case the hexadecimal number defines the code point
657    to match. By default, as in Perl, a hexadecimal number is always expected after
658    \ex, but it may have zero, one, or two digits (so, for example, \exz matches a
659    binary zero character followed by z).
660    .sp
661    PCRE_MULTILINE    PCRE_MULTILINE
662    .sp
663  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
664  characters (even if it actually contains several newlines). The "start of line"  characters (even if it actually contains newlines). The "start of line"
665  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
666  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
667  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
668  Perl.  Perl.
669    .P
670  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
671  match immediately following or immediately before any newline in the subject  match immediately following or immediately before internal newlines in the
672  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
673  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
674  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
675  occurrences of ^ or $ in a pattern, setting PCRE_MULTILINE has no effect.  occurrences of ^ or $ in a pattern, setting PCRE_MULTILINE has no effect.
676    .sp
677      PCRE_NEWLINE_CR
678      PCRE_NEWLINE_LF
679      PCRE_NEWLINE_CRLF
680      PCRE_NEWLINE_ANYCRLF
681      PCRE_NEWLINE_ANY
682    .sp
683    These options override the default newline definition that was chosen when PCRE
684    was built. Setting the first or the second specifies that a newline is
685    indicated by a single character (CR or LF, respectively). Setting
686    PCRE_NEWLINE_CRLF specifies that a newline is indicated by the two-character
687    CRLF sequence. Setting PCRE_NEWLINE_ANYCRLF specifies that any of the three
688    preceding sequences should be recognized. Setting PCRE_NEWLINE_ANY specifies
689    that any Unicode newline sequence should be recognized. The Unicode newline
690    sequences are the three just mentioned, plus the single characters VT (vertical
691    tab, U+000B), FF (formfeed, U+000C), NEL (next line, U+0085), LS (line
692    separator, U+2028), and PS (paragraph separator, U+2029). The last two are
693    recognized only in UTF-8 mode.
694    .P
695    The newline setting in the options word uses three bits that are treated
696    as a number, giving eight possibilities. Currently only six are used (default
697    plus the five values above). This means that if you set more than one newline
698    option, the combination may or may not be sensible. For example,
699    PCRE_NEWLINE_CR with PCRE_NEWLINE_LF is equivalent to PCRE_NEWLINE_CRLF, but
700    other combinations may yield unused numbers and cause an error.
701    .P
702    The only time that a line break in a pattern is specially recognized when
703    compiling is when PCRE_EXTENDED is set. CR and LF are whitespace characters,
704    and so are ignored in this mode. Also, an unescaped # outside a character class
705    indicates a comment that lasts until after the next line break sequence. In
706    other circumstances, line break sequences in patterns are treated as literal
707    data.
708    .P
709    The newline option that is set at compile time becomes the default that is used
710    for \fBpcre_exec()\fP and \fBpcre_dfa_exec()\fP, but it can be overridden.
711    .sp
712    PCRE_NO_AUTO_CAPTURE    PCRE_NO_AUTO_CAPTURE
713    .sp
714  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
715  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
716  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
717  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
718  in Perl.  in Perl.
719    .sp
720      NO_START_OPTIMIZE
721    .sp
722    This is an option that acts at matching time; that is, it is really an option
723    for \fBpcre_exec()\fP or \fBpcre_dfa_exec()\fP. If it is set at compile time,
724    it is remembered with the compiled pattern and assumed at matching time. For
725    details see the discussion of PCRE_NO_START_OPTIMIZE
726    .\" HTML <a href="#execoptions">
727    .\" </a>
728    below.
729    .\"
730    .sp
731      PCRE_UCP
732    .sp
733    This option changes the way PCRE processes \eB, \eb, \eD, \ed, \eS, \es, \eW,
734    \ew, and some of the POSIX character classes. By default, only ASCII characters
735    are recognized, but if PCRE_UCP is set, Unicode properties are used instead to
736    classify characters. More details are given in the section on
737    .\" HTML <a href="pcre.html#genericchartypes">
738    .\" </a>
739    generic character types
740    .\"
741    in the
742    .\" HREF
743    \fBpcrepattern\fP
744    .\"
745    page. If you set PCRE_UCP, matching one of the items it affects takes much
746    longer. The option is available only if PCRE has been compiled with Unicode
747    property support.
748    .sp
749    PCRE_UNGREEDY    PCRE_UNGREEDY
750    .sp
751  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
752  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
753  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.
754    .sp
755    PCRE_UTF8    PCRE_UTF8
756    .sp
757  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
758  of UTF-8 characters instead of single-byte character strings. However, it is  of UTF-8 characters instead of single-byte character strings. However, it is
759  available only if PCRE has been built to include UTF-8 support. If not, the use  available only when PCRE is built to include UTF-8 support. If not, the use
760  of this option provokes an error. Details of how this option changes the  of this option provokes an error. Details of how this option changes the
761  behaviour of PCRE are given in the  behaviour of PCRE are given in the
 .\" HTML <a href="pcre.html#utf8support">  
 .\" </a>  
 section on UTF-8 support  
 .\"  
 in the main  
762  .\" HREF  .\" HREF
763  \fBpcre\fR  \fBpcreunicode\fP
764  .\"  .\"
765  page.  page.
766    .sp
767    PCRE_NO_UTF8_CHECK    PCRE_NO_UTF8_CHECK
768    .sp
769  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
770  automatically checked. If an invalid UTF-8 sequence of bytes is found,  automatically checked. There is a discussion about the
771  \fBpcre_compile()\fR returns an error. If you already know that your pattern is  .\" HTML <a href="pcre.html#utf8strings">
772  valid, and you want to skip this check for performance reasons, you can set the  .\" </a>
773  PCRE_NO_UTF8_CHECK option. When it is set, the effect of passing an invalid  validity of UTF-8 strings
774  UTF-8 string as a pattern is undefined. It may cause your program to crash.  .\"
775  Note that there is a similar option for suppressing the checking of subject  in the main
776  strings passed to \fBpcre_exec()\fR.  .\" HREF
777    \fBpcre\fP
778    .\"
779  .SH STUDYING A PATTERN  page. If an invalid UTF-8 sequence of bytes is found, \fBpcre_compile()\fP
780  .rs  returns an error. If you already know that your pattern is valid, and you want
781  .sp  to skip this check for performance reasons, you can set the PCRE_NO_UTF8_CHECK
782  .B pcre_extra *pcre_study(const pcre *\fIcode\fR, int \fIoptions\fR,  option. When it is set, the effect of passing an invalid UTF-8 string as a
783  .ti +5n  pattern is undefined. It may cause your program to crash. Note that this option
784  .B const char **\fIerrptr\fR);  can also be passed to \fBpcre_exec()\fP and \fBpcre_dfa_exec()\fP, to suppress
785  .PP  the UTF-8 validity checking of subject strings.
786  When a pattern is going to be used several times, it is worth spending more  .
787  time analyzing it in order to speed up the time taken for matching. The  .
788  function \fBpcre_study()\fR takes a pointer to a compiled pattern as its first  .SH "COMPILATION ERROR CODES"
789  argument. If studing the pattern produces additional information that will help  .rs
790  speed up matching, \fBpcre_study()\fR returns a pointer to a \fBpcre_extra\fR  .sp
791  block, in which the \fIstudy_data\fR field points to the results of the study.  The following table lists the error codes than may be returned by
792    \fBpcre_compile2()\fP, along with the error messages that may be returned by
793  The returned value from a \fBpcre_study()\fR can be passed directly to  both compiling functions. As PCRE has developed, some error codes have fallen
794  \fBpcre_exec()\fR. However, the \fBpcre_extra\fR block also contains other  out of use. To avoid confusion, they have not been re-used.
795  fields that can be set by the caller before the block is passed; these are  .sp
796  described below. If studying the pattern does not produce any additional     0  no error
797  information, \fBpcre_study()\fR returns NULL. In that circumstance, if the     1  \e at end of pattern
798  calling program wants to pass some of the other fields to \fBpcre_exec()\fR, it     2  \ec at end of pattern
799  must set up its own \fBpcre_extra\fR block.     3  unrecognized character follows \e
800       4  numbers out of order in {} quantifier
801  The second argument contains option bits. At present, no options are defined     5  number too big in {} quantifier
802  for \fBpcre_study()\fR, and this argument should always be zero.     6  missing terminating ] for character class
803       7  invalid escape sequence in character class
804  The third argument for \fBpcre_study()\fR is a pointer for an error message. If     8  range out of order in character class
805       9  nothing to repeat
806      10  [this code is not in use]
807      11  internal error: unexpected repeat
808      12  unrecognized character after (? or (?-
809      13  POSIX named classes are supported only within a class
810      14  missing )
811      15  reference to non-existent subpattern
812      16  erroffset passed as NULL
813      17  unknown option bit(s) set
814      18  missing ) after comment
815      19  [this code is not in use]
816      20  regular expression is too large
817      21  failed to get memory
818      22  unmatched parentheses
819      23  internal error: code overflow
820      24  unrecognized character after (?<
821      25  lookbehind assertion is not fixed length
822      26  malformed number or name after (?(
823      27  conditional group contains more than two branches
824      28  assertion expected after (?(
825      29  (?R or (?[+-]digits must be followed by )
826      30  unknown POSIX class name
827      31  POSIX collating elements are not supported
828      32  this version of PCRE is not compiled with PCRE_UTF8 support
829      33  [this code is not in use]
830      34  character value in \ex{...} sequence is too large
831      35  invalid condition (?(0)
832      36  \eC not allowed in lookbehind assertion
833      37  PCRE does not support \eL, \el, \eN{name}, \eU, or \eu
834      38  number after (?C is > 255
835      39  closing ) for (?C expected
836      40  recursive call could loop indefinitely
837      41  unrecognized character after (?P
838      42  syntax error in subpattern name (missing terminator)
839      43  two named subpatterns have the same name
840      44  invalid UTF-8 string
841      45  support for \eP, \ep, and \eX has not been compiled
842      46  malformed \eP or \ep sequence
843      47  unknown property name after \eP or \ep
844      48  subpattern name is too long (maximum 32 characters)
845      49  too many named subpatterns (maximum 10000)
846      50  [this code is not in use]
847      51  octal value is greater than \e377 (not in UTF-8 mode)
848      52  internal error: overran compiling workspace
849      53  internal error: previously-checked referenced subpattern
850            not found
851      54  DEFINE group contains more than one branch
852      55  repeating a DEFINE group is not allowed
853      56  inconsistent NEWLINE options
854      57  \eg is not followed by a braced, angle-bracketed, or quoted
855            name/number or by a plain number
856      58  a numbered reference must not be zero
857      59  an argument is not allowed for (*ACCEPT), (*FAIL), or (*COMMIT)
858      60  (*VERB) not recognized
859      61  number is too big
860      62  subpattern name expected
861      63  digit expected after (?+
862      64  ] is an invalid data character in JavaScript compatibility mode
863      65  different names for subpatterns of the same number are
864            not allowed
865      66  (*MARK) must have an argument
866      67  this version of PCRE is not compiled with PCRE_UCP support
867      68  \ec must be followed by an ASCII character
868      69  \ek is not followed by a braced, angle-bracketed, or quoted name
869    .sp
870    The numbers 32 and 10000 in errors 48 and 49 are defaults; different values may
871    be used if the limits were changed when PCRE was built.
872    .
873    .
874    .\" HTML <a name="studyingapattern"></a>
875    .SH "STUDYING A PATTERN"
876    .rs
877    .sp
878    .B pcre_extra *pcre_study(const pcre *\fIcode\fP, int \fIoptions\fP
879    .ti +5n
880    .B const char **\fIerrptr\fP);
881    .PP
882    If a compiled pattern is going to be used several times, it is worth spending
883    more time analyzing it in order to speed up the time taken for matching. The
884    function \fBpcre_study()\fP takes a pointer to a compiled pattern as its first
885    argument. If studying the pattern produces additional information that will
886    help speed up matching, \fBpcre_study()\fP returns a pointer to a
887    \fBpcre_extra\fP block, in which the \fIstudy_data\fP field points to the
888    results of the study.
889    .P
890    The returned value from \fBpcre_study()\fP can be passed directly to
891    \fBpcre_exec()\fP or \fBpcre_dfa_exec()\fP. However, a \fBpcre_extra\fP block
892    also contains other fields that can be set by the caller before the block is
893    passed; these are described
894    .\" HTML <a href="#extradata">
895    .\" </a>
896    below
897    .\"
898    in the section on matching a pattern.
899    .P
900    If studying the pattern does not produce any useful information,
901    \fBpcre_study()\fP returns NULL. In that circumstance, if the calling program
902    wants to pass any of the other fields to \fBpcre_exec()\fP or
903    \fBpcre_dfa_exec()\fP, it must set up its own \fBpcre_extra\fP block.
904    .P
905    The second argument of \fBpcre_study()\fP contains option bits. There is only
906    one option: PCRE_STUDY_JIT_COMPILE. If this is set, and the just-in-time
907    compiler is available, the pattern is further compiled into machine code that
908    executes much faster than the \fBpcre_exec()\fP matching function. If
909    the just-in-time compiler is not available, this option is ignored. All other
910    bits in the \fIoptions\fP argument must be zero.
911    .P
912    JIT compilation is a heavyweight optimization. It can take some time for
913    patterns to be analyzed, and for one-off matches and simple patterns the
914    benefit of faster execution might be offset by a much slower study time.
915    Not all patterns can be optimized by the JIT compiler. For those that cannot be
916    handled, matching automatically falls back to the \fBpcre_exec()\fP
917    interpreter. For more details, see the
918    .\" HREF
919    \fBpcrejit\fP
920    .\"
921    documentation.
922    .P
923    The third argument for \fBpcre_study()\fP is a pointer for an error message. If
924  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
925  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
926  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
927  be sure that it has run successfully.  should test the error pointer for NULL after calling \fBpcre_study()\fP, to be
928    sure that it has run successfully.
929  This is a typical call to \fBpcre_study\fR():  .P
930    When you are finished with a pattern, you can free the memory used for the
931    pcre_extra *pe;  study data by calling \fBpcre_free_study()\fP. This function was added to the
932    pe = pcre_study(  API for release 8.20. For earlier versions, the memory could be freed with
933    \fBpcre_free()\fP, just like the pattern itself. This will still work in cases
934    where PCRE_STUDY_JIT_COMPILE is not used, but it is advisable to change to the
935    new function when convenient.
936    .P
937    This is a typical way in which \fBpcre_study\fP() is used (except that in a
938    real application there should be tests for errors):
939    .sp
940      int rc;
941      pcre *re;
942      pcre_extra *sd;
943      re = pcre_compile("pattern", 0, &error, &erroroffset, NULL);
944      sd = pcre_study(
945      re,             /* result of pcre_compile() */      re,             /* result of pcre_compile() */
946      0,              /* no options exist */      0,              /* no options */
947      &error);        /* set to NULL or points to a message */      &error);        /* set to NULL or points to a message */
948      rc = pcre_exec(   /* see below for details of pcre_exec() options */
949  At present, studying a pattern is useful only for non-anchored patterns that do      re, sd, "subject", 7, 0, 0, ovector, 30);
950  not have a single fixed starting character. A bitmap of possible starting    ...
951  characters is created.    pcre_free_study(sd);
952      pcre_free(re);
953    .sp
954    Studying a pattern does two things: first, a lower bound for the length of
955    subject string that is needed to match the pattern is computed. This does not
956    mean that there are any strings of that length that match, but it does
957    guarantee that no shorter strings match. The value is used by
958    \fBpcre_exec()\fP and \fBpcre_dfa_exec()\fP to avoid wasting time by trying to
959    match strings that are shorter than the lower bound. You can find out the value
960    in a calling program via the \fBpcre_fullinfo()\fP function.
961    .P
962    Studying a pattern is also useful for non-anchored patterns that do not have a
963    single fixed starting character. A bitmap of possible starting bytes is
964    created. This speeds up finding a position in the subject at which to start
965    matching.
966    .P
967    These two optimizations apply to both \fBpcre_exec()\fP and
968    \fBpcre_dfa_exec()\fP. However, they are not used by \fBpcre_exec()\fP if
969    \fBpcre_study()\fP is called with the PCRE_STUDY_JIT_COMPILE option, and
970    just-in-time compiling is successful. The optimizations can be disabled by
971    setting the PCRE_NO_START_OPTIMIZE option when calling \fBpcre_exec()\fP or
972    \fBpcre_dfa_exec()\fP. You might want to do this if your pattern contains
973    callouts or (*MARK) (which cannot be handled by the JIT compiler), and you want
974    to make use of these facilities in cases where matching fails. See the
975    discussion of PCRE_NO_START_OPTIMIZE
976    .\" HTML <a href="#execoptions">
977    .\" </a>
978    below.
979    .\"
980    .
981    .
982  .\" HTML <a name="localesupport"></a>  .\" HTML <a name="localesupport"></a>
983  .SH LOCALE SUPPORT  .SH "LOCALE SUPPORT"
984  .rs  .rs
985  .sp  .sp
986  PCRE handles caseless matching, and determines whether characters are letters,  PCRE handles caseless matching, and determines whether characters are letters,
987  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
988  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 with codes
989  contains a default set of tables that is created in the default C locale when  less than 128. By default, higher-valued codes never match escapes such as \ew
990  PCRE is compiled. This is used when the final argument of \fBpcre_compile()\fR  or \ed, but they can be tested with \ep if PCRE is built with Unicode character
991  is NULL, and is sufficient for many applications.  property support. Alternatively, the PCRE_UCP option can be set at compile
992    time; this causes \ew and friends to use Unicode property support instead of
993  An alternative set of tables can, however, be supplied. Such tables are built  built-in tables. The use of locales with Unicode is discouraged. If you are
994  by calling the \fBpcre_maketables()\fR function, which has no arguments, in the  handling characters with codes greater than 128, you should either use UTF-8
995  relevant locale. The result can then be passed to \fBpcre_compile()\fR as often  and Unicode, or use locales, but not try to mix the two.
996  as necessary. For example, to build and use tables that are appropriate for the  .P
997  French locale (where accented characters with codes greater than 128 are  PCRE contains an internal set of tables that are used when the final argument
998  treated as letters), the following code could be used:  of \fBpcre_compile()\fP is NULL. These are sufficient for many applications.
999    Normally, the internal tables recognize only ASCII characters. However, when
1000    setlocale(LC_CTYPE, "fr");  PCRE is built, it is possible to cause the internal tables to be rebuilt in the
1001    default "C" locale of the local system, which may cause them to be different.
1002    .P
1003    The internal tables can always be overridden by tables supplied by the
1004    application that calls PCRE. These may be created in a different locale from
1005    the default. As more and more applications change to using Unicode, the need
1006    for this locale support is expected to die away.
1007    .P
1008    External tables are built by calling the \fBpcre_maketables()\fP function,
1009    which has no arguments, in the relevant locale. The result can then be passed
1010    to \fBpcre_compile()\fP or \fBpcre_exec()\fP as often as necessary. For
1011    example, to build and use tables that are appropriate for the French locale
1012    (where accented characters with values greater than 128 are treated as letters),
1013    the following code could be used:
1014    .sp
1015      setlocale(LC_CTYPE, "fr_FR");
1016    tables = pcre_maketables();    tables = pcre_maketables();
1017    re = pcre_compile(..., tables);    re = pcre_compile(..., tables);
1018    .sp
1019  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
1020  pointer that is passed to \fBpcre_compile\fR is saved with the compiled  are using Windows, the name for the French locale is "french".
1021  pattern, and the same tables are used via this pointer by \fBpcre_study()\fR  .P
1022  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
1023  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
1024  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
1025  memory containing the tables remains available for as long as it is needed.  needed.
1026    .P
1027  .SH INFORMATION ABOUT A PATTERN  The pointer that is passed to \fBpcre_compile()\fP is saved with the compiled
1028    pattern, and the same tables are used via this pointer by \fBpcre_study()\fP
1029    and normally also by \fBpcre_exec()\fP. Thus, by default, for any single
1030    pattern, compilation, studying and matching all happen in the same locale, but
1031    different patterns can be compiled in different locales.
1032    .P
1033    It is possible to pass a table pointer or NULL (indicating the use of the
1034    internal tables) to \fBpcre_exec()\fP. Although not intended for this purpose,
1035    this facility could be used to match a pattern in a different locale from the
1036    one in which it was compiled. Passing table pointers at run time is discussed
1037    below in the section on matching a pattern.
1038    .
1039    .
1040    .\" HTML <a name="infoaboutpattern"></a>
1041    .SH "INFORMATION ABOUT A PATTERN"
1042  .rs  .rs
1043  .sp  .sp
1044  .B int pcre_fullinfo(const pcre *\fIcode\fR, "const pcre_extra *\fIextra\fR,"  .B int pcre_fullinfo(const pcre *\fIcode\fP, "const pcre_extra *\fIextra\fP,"
1045  .ti +5n  .ti +5n
1046  .B int \fIwhat\fR, void *\fIwhere\fR);  .B int \fIwhat\fP, void *\fIwhere\fP);
1047  .PP  .PP
1048  The \fBpcre_fullinfo()\fR function returns information about a compiled  The \fBpcre_fullinfo()\fP function returns information about a compiled
1049  pattern. It replaces the obsolete \fBpcre_info()\fR function, which is  pattern. It replaces the obsolete \fBpcre_info()\fP function, which is
1050  nevertheless retained for backwards compability (and is documented below).  nevertheless retained for backwards compability (and is documented below).
1051    .P
1052  The first argument for \fBpcre_fullinfo()\fR is a pointer to the compiled  The first argument for \fBpcre_fullinfo()\fP is a pointer to the compiled
1053  pattern. The second argument is the result of \fBpcre_study()\fR, or NULL if  pattern. The second argument is the result of \fBpcre_study()\fP, or NULL if
1054  the pattern was not studied. The third argument specifies which piece of  the pattern was not studied. The third argument specifies which piece of
1055  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
1056  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
1057  the following negative numbers:  the following negative numbers:
1058    .sp
1059    PCRE_ERROR_NULL       the argument \fIcode\fR was NULL    PCRE_ERROR_NULL       the argument \fIcode\fP was NULL
1060                          the argument \fIwhere\fR was NULL                          the argument \fIwhere\fP was NULL
1061    PCRE_ERROR_BADMAGIC   the "magic number" was not found    PCRE_ERROR_BADMAGIC   the "magic number" was not found
1062    PCRE_ERROR_BADOPTION  the value of \fIwhat\fR was invalid    PCRE_ERROR_BADOPTION  the value of \fIwhat\fP was invalid
1063    .sp
1064  Here is a typical call of \fBpcre_fullinfo()\fR, to obtain the length of the  The "magic number" is placed at the start of each compiled pattern as an simple
1065  compiled pattern:  check against passing an arbitrary memory pointer. Here is a typical call of
1066    \fBpcre_fullinfo()\fP, to obtain the length of the compiled pattern:
1067    .sp
1068    int rc;    int rc;
1069    unsigned long int length;    size_t length;
1070    rc = pcre_fullinfo(    rc = pcre_fullinfo(
1071      re,               /* result of pcre_compile() */      re,               /* result of pcre_compile() */
1072      pe,               /* result of pcre_study(), or NULL */      sd,               /* result of pcre_study(), or NULL */
1073      PCRE_INFO_SIZE,   /* what is required */      PCRE_INFO_SIZE,   /* what is required */
1074      &length);         /* where to put the data */      &length);         /* where to put the data */
1075    .sp
1076  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
1077  as follows:  as follows:
1078    .sp
1079    PCRE_INFO_BACKREFMAX    PCRE_INFO_BACKREFMAX
1080    .sp
1081  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
1082  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
1083  no back references.  no back references.
1084    .sp
1085    PCRE_INFO_CAPTURECOUNT    PCRE_INFO_CAPTURECOUNT
1086    .sp
1087  Return the number of capturing subpatterns in the pattern. The fourth argument  Return the number of capturing subpatterns in the pattern. The fourth argument
1088  should point to an \fbint\fR variable.  should point to an \fBint\fP variable.
1089    .sp
1090      PCRE_INFO_DEFAULT_TABLES
1091    .sp
1092    Return a pointer to the internal default character tables within PCRE. The
1093    fourth argument should point to an \fBunsigned char *\fP variable. This
1094    information call is provided for internal use by the \fBpcre_study()\fP
1095    function. External callers can cause PCRE to use its internal tables by passing
1096    a NULL table pointer.
1097    .sp
1098    PCRE_INFO_FIRSTBYTE    PCRE_INFO_FIRSTBYTE
1099    .sp
1100  Return information about the first byte of any matched string, for a  Return information about the first byte of any matched string, for a
1101  non-anchored pattern. (This option used to be called PCRE_INFO_FIRSTCHAR; the  non-anchored pattern. The fourth argument should point to an \fBint\fP
1102  old name is still recognized for backwards compatibility.)  variable. (This option used to be called PCRE_INFO_FIRSTCHAR; the old name is
1103    still recognized for backwards compatibility.)
1104  If there is a fixed first byte, e.g. from a pattern such as (cat|cow|coyote),  .P
1105  it is returned in the integer pointed to by \fIwhere\fR. Otherwise, if either  If there is a fixed first byte, for example, from a pattern such as
1106    (cat|cow|coyote), its value is returned. Otherwise, if either
1107    .sp
1108  (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
1109  starts with "^", or  starts with "^", or
1110    .sp
1111  (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
1112  (if it were set, the pattern would be anchored),  (if it were set, the pattern would be anchored),
1113    .sp
1114  -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
1115  subject string or after any newline within the string. Otherwise -2 is  subject string or after any newline within the string. Otherwise -2 is
1116  returned. For anchored patterns, -2 is returned.  returned. For anchored patterns, -2 is returned.
1117    .sp
1118    PCRE_INFO_FIRSTTABLE    PCRE_INFO_FIRSTTABLE
1119    .sp
1120  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
1121  table indicating a fixed set of bytes for the first byte in any matching  table indicating a fixed set of bytes for the first byte in any matching
1122  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
1123  fourth argument should point to an \fBunsigned char *\fR variable.  fourth argument should point to an \fBunsigned char *\fP variable.
1124    .sp
1125      PCRE_INFO_HASCRORLF
1126    .sp
1127    Return 1 if the pattern contains any explicit matches for CR or LF characters,
1128    otherwise 0. The fourth argument should point to an \fBint\fP variable. An
1129    explicit match is either a literal CR or LF character, or \er or \en.
1130    .sp
1131      PCRE_INFO_JCHANGED
1132    .sp
1133    Return 1 if the (?J) or (?-J) option setting is used in the pattern, otherwise
1134    0. The fourth argument should point to an \fBint\fP variable. (?J) and
1135    (?-J) set and unset the local PCRE_DUPNAMES option, respectively.
1136    .sp
1137      PCRE_INFO_JIT
1138    .sp
1139    Return 1 if the pattern was studied with the PCRE_STUDY_JIT_COMPILE option, and
1140    just-in-time compiling was successful. The fourth argument should point to an
1141    \fBint\fP variable. A return value of 0 means that JIT support is not available
1142    in this version of PCRE, or that the pattern was not studied with the
1143    PCRE_STUDY_JIT_COMPILE option, or that the JIT compiler could not handle this
1144    particular pattern. See the
1145    .\" HREF
1146    \fBpcrejit\fP
1147    .\"
1148    documentation for details of what can and cannot be handled.
1149    .sp
1150      PCRE_INFO_JITSIZE
1151    .sp
1152    If the pattern was successfully studied with the PCRE_STUDY_JIT_COMPILE option,
1153    return the size of the JIT compiled code, otherwise return zero. The fourth
1154    argument should point to a \fBsize_t\fP variable.
1155    .sp
1156    PCRE_INFO_LASTLITERAL    PCRE_INFO_LASTLITERAL
1157    .sp
1158  Return the value of the rightmost literal byte that must exist in any matched  Return the value of the rightmost literal byte that must exist in any matched
1159  string, other than at its start, if such a byte has been recorded. The fourth  string, other than at its start, if such a byte has been recorded. The fourth
1160  argument should point to an \fBint\fR variable. If there is no such byte, -1 is  argument should point to an \fBint\fP variable. If there is no such byte, -1 is
1161  returned. For anchored patterns, a last literal byte is recorded only if it  returned. For anchored patterns, a last literal byte is recorded only if it
1162  follows something of variable length. For example, for the pattern  follows something of variable length. For example, for the pattern
1163  /^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
1164  is -1.  is -1.
1165    .sp
1166      PCRE_INFO_MINLENGTH
1167    .sp
1168    If the pattern was studied and a minimum length for matching subject strings
1169    was computed, its value is returned. Otherwise the returned value is -1. The
1170    value is a number of characters, not bytes (this may be relevant in UTF-8
1171    mode). The fourth argument should point to an \fBint\fP variable. A
1172    non-negative value is a lower bound to the length of any matching string. There
1173    may not be any strings of that length that do actually match, but every string
1174    that does match is at least that long.
1175    .sp
1176    PCRE_INFO_NAMECOUNT    PCRE_INFO_NAMECOUNT
1177    PCRE_INFO_NAMEENTRYSIZE    PCRE_INFO_NAMEENTRYSIZE
1178    PCRE_INFO_NAMETABLE    PCRE_INFO_NAMETABLE
1179    .sp
1180  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
1181  names are just an additional way of identifying the parentheses, which still  names are just an additional way of identifying the parentheses, which still
1182  acquire a number. A caller that wants to extract data from a named subpattern  acquire numbers. Several convenience functions such as
1183  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
1184  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
1185  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
1186  table for the pattern.  output vector (described with \fBpcre_exec()\fP below). To do the conversion,
1187    you need to use the name-to-number map, which is described by these three
1188    values.
1189    .P
1190  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
1191  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
1192  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
1193  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
1194  entry of the table (a pointer to \fBchar\fR). The first two bytes of each entry  entry of the table (a pointer to \fBchar\fP). The first two bytes of each entry
1195  are the number of the capturing parenthesis, most significant byte first. The  are the number of the capturing parenthesis, most significant byte first. The
1196  rest of the entry is the corresponding name, zero terminated. The names are in  rest of the entry is the corresponding name, zero terminated.
1197  alphabetical order. For example, consider the following pattern (assume  .P
1198  PCRE_EXTENDED is set, so white space - including newlines - is ignored):  The names are in alphabetical order. Duplicate names may appear if (?| is used
1199    to create multiple groups with the same number, as described in the
1200    (?P<date> (?P<year>(\\d\\d)?\\d\\d) -  .\" HTML <a href="pcrepattern.html#dupsubpatternnumber">
1201    (?P<month>\\d\\d) - (?P<day>\\d\\d) )  .\" </a>
1202    section on duplicate subpattern numbers
1203    .\"
1204    in the
1205    .\" HREF
1206    \fBpcrepattern\fP
1207    .\"
1208    page. Duplicate names for subpatterns with different numbers are permitted only
1209    if PCRE_DUPNAMES is set. In all cases of duplicate names, they appear in the
1210    table in the order in which they were found in the pattern. In the absence of
1211    (?| this is the order of increasing number; when (?| is used this is not
1212    necessarily the case because later subpatterns may have lower numbers.
1213    .P
1214    As a simple example of the name/number table, consider the following pattern
1215    (assume PCRE_EXTENDED is set, so white space - including newlines - is
1216    ignored):
1217    .sp
1218    .\" JOIN
1219      (?<date> (?<year>(\ed\ed)?\ed\ed) -
1220      (?<month>\ed\ed) - (?<day>\ed\ed) )
1221    .sp
1222  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
1223  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
1224  bytes shows in hex, and undefined bytes shown as ??:  bytes shows in hexadecimal, and undefined bytes shown as ??:
1225    .sp
1226    00 01 d  a  t  e  00 ??    00 01 d  a  t  e  00 ??
1227    00 05 d  a  y  00 ?? ??    00 05 d  a  y  00 ?? ??
1228    00 04 m  o  n  t  h  00    00 04 m  o  n  t  h  00
1229    00 02 y  e  a  r  00 ??    00 02 y  e  a  r  00 ??
1230    .sp
1231  When writing code to extract data from named subpatterns, remember that the  When writing code to extract data from named subpatterns using the
1232  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
1233    different for each compiled pattern.
1234    .sp
1235      PCRE_INFO_OKPARTIAL
1236    .sp
1237    Return 1 if the pattern can be used for partial matching with
1238    \fBpcre_exec()\fP, otherwise 0. The fourth argument should point to an
1239    \fBint\fP variable. From release 8.00, this always returns 1, because the
1240    restrictions that previously applied to partial matching have been lifted. The
1241    .\" HREF
1242    \fBpcrepartial\fP
1243    .\"
1244    documentation gives details of partial matching.
1245    .sp
1246    PCRE_INFO_OPTIONS    PCRE_INFO_OPTIONS
1247    .sp
1248  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
1249  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
1250  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
1251  top-level option settings within the pattern itself.  top-level option settings at the start of the pattern itself. In other words,
1252    they are the options that will be in force when matching starts. For example,
1253    if the pattern /(?im)abc(?-i)d/ is compiled with the PCRE_EXTENDED option, the
1254    result is PCRE_CASELESS, PCRE_MULTILINE, and PCRE_EXTENDED.
1255    .P
1256  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
1257  alternatives begin with one of the following:  alternatives begin with one of the following:
1258    .sp
1259    ^     unless PCRE_MULTILINE is set    ^     unless PCRE_MULTILINE is set
1260    \\A    always    \eA    always
1261    \\G    always    \eG    always
1262    .\" JOIN
1263    .*    if PCRE_DOTALL is set and there are no back    .*    if PCRE_DOTALL is set and there are no back
1264            references to the subpattern in which .* appears            references to the subpattern in which .* appears
1265    .sp
1266  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
1267  \fBpcre_fullinfo()\fR.  \fBpcre_fullinfo()\fP.
1268    .sp
1269    PCRE_INFO_SIZE    PCRE_INFO_SIZE
1270    .sp
1271  Return the size of the compiled pattern, that is, the value that was passed as  Return the size of the compiled pattern. The fourth argument should point to a
1272  the argument to \fBpcre_malloc()\fR when PCRE was getting memory in which to  \fBsize_t\fP variable. This value does not include the size of the \fBpcre\fP
1273  place the compiled data. The fourth argument should point to a \fBsize_t\fR  structure that is returned by \fBpcre_compile()\fP. The value that is passed as
1274  variable.  the argument to \fBpcre_malloc()\fP when \fBpcre_compile()\fP is getting memory
1275    in which to place the compiled data is the value returned by this option plus
1276    the size of the \fBpcre\fP structure. Studying a compiled pattern, with or
1277    without JIT, does not alter the value returned by this option.
1278    .sp
1279    PCRE_INFO_STUDYSIZE    PCRE_INFO_STUDYSIZE
1280    .sp
1281  Returns the size of the data block pointed to by the \fIstudy_data\fR field in  Return the size of the data block pointed to by the \fIstudy_data\fP field in a
1282  a \fBpcre_extra\fR block. That is, it is the value that was passed to  \fBpcre_extra\fP block. If \fBpcre_extra\fP is NULL, or there is no study data,
1283  \fBpcre_malloc()\fR when PCRE was getting memory into which to place the data  zero is returned. The fourth argument should point to a \fBsize_t\fP variable.
1284  created by \fBpcre_study()\fR. The fourth argument should point to a  The \fIstudy_data\fP field is set by \fBpcre_study()\fP to record information
1285  \fBsize_t\fR variable.  that will speed up matching (see the section entitled
1286    .\" HTML <a href="#studyingapattern">
1287  .SH OBSOLETE INFO FUNCTION  .\" </a>
1288    "Studying a pattern"
1289    .\"
1290    above). The format of the \fIstudy_data\fP block is private, but its length
1291    is made available via this option so that it can be saved and restored (see the
1292    .\" HREF
1293    \fBpcreprecompile\fP
1294    .\"
1295    documentation for details).
1296    .
1297    .
1298    .SH "OBSOLETE INFO FUNCTION"
1299  .rs  .rs
1300  .sp  .sp
1301  .B int pcre_info(const pcre *\fIcode\fR, int *\fIoptptr\fR, int  .B int pcre_info(const pcre *\fIcode\fP, int *\fIoptptr\fP, int
1302  .B *\fIfirstcharptr\fR);  .B *\fIfirstcharptr\fP);
1303  .PP  .PP
1304  The \fBpcre_info()\fR function is now obsolete because its interface is too  The \fBpcre_info()\fP function is now obsolete because its interface is too
1305  restrictive to return all the available data about a compiled pattern. New  restrictive to return all the available data about a compiled pattern. New
1306  programs should use \fBpcre_fullinfo()\fR instead. The yield of  programs should use \fBpcre_fullinfo()\fP instead. The yield of
1307  \fBpcre_info()\fR is the number of capturing subpatterns, or one of the  \fBpcre_info()\fP is the number of capturing subpatterns, or one of the
1308  following negative numbers:  following negative numbers:
1309    .sp
1310    PCRE_ERROR_NULL       the argument \fIcode\fR was NULL    PCRE_ERROR_NULL       the argument \fIcode\fP was NULL
1311    PCRE_ERROR_BADMAGIC   the "magic number" was not found    PCRE_ERROR_BADMAGIC   the "magic number" was not found
1312    .sp
1313  If the \fIoptptr\fR argument is not NULL, a copy of the options with which the  If the \fIoptptr\fP argument is not NULL, a copy of the options with which the
1314  pattern was compiled is placed in the integer it points to (see  pattern was compiled is placed in the integer it points to (see
1315  PCRE_INFO_OPTIONS above).  PCRE_INFO_OPTIONS above).
1316    .P
1317  If the pattern is not anchored and the \fIfirstcharptr\fR argument is not NULL,  If the pattern is not anchored and the \fIfirstcharptr\fP argument is not NULL,
1318  it is used to pass back information about the first character of any matched  it is used to pass back information about the first character of any matched
1319  string (see PCRE_INFO_FIRSTBYTE above).  string (see PCRE_INFO_FIRSTBYTE above).
1320    .
1321  .SH MATCHING A PATTERN  .
1322    .SH "REFERENCE COUNTS"
1323  .rs  .rs
1324  .sp  .sp
1325  .B int pcre_exec(const pcre *\fIcode\fR, "const pcre_extra *\fIextra\fR,"  .B int pcre_refcount(pcre *\fIcode\fP, int \fIadjust\fP);
1326    .PP
1327    The \fBpcre_refcount()\fP function is used to maintain a reference count in the
1328    data block that contains a compiled pattern. It is provided for the benefit of
1329    applications that operate in an object-oriented manner, where different parts
1330    of the application may be using the same compiled pattern, but you want to free
1331    the block when they are all done.
1332    .P
1333    When a pattern is compiled, the reference count field is initialized to zero.
1334    It is changed only by calling this function, whose action is to add the
1335    \fIadjust\fP value (which may be positive or negative) to it. The yield of the
1336    function is the new value. However, the value of the count is constrained to
1337    lie between 0 and 65535, inclusive. If the new value is outside these limits,
1338    it is forced to the appropriate limit value.
1339    .P
1340    Except when it is zero, the reference count is not correctly preserved if a
1341    pattern is compiled on one host and then transferred to a host whose byte-order
1342    is different. (This seems a highly unlikely scenario.)
1343    .
1344    .
1345    .SH "MATCHING A PATTERN: THE TRADITIONAL FUNCTION"
1346    .rs
1347    .sp
1348    .B int pcre_exec(const pcre *\fIcode\fP, "const pcre_extra *\fIextra\fP,"
1349  .ti +5n  .ti +5n
1350  .B "const char *\fIsubject\fR," int \fIlength\fR, int \fIstartoffset\fR,  .B "const char *\fIsubject\fP," int \fIlength\fP, int \fIstartoffset\fP,
1351  .ti +5n  .ti +5n
1352  .B int \fIoptions\fR, int *\fIovector\fR, int \fIovecsize\fR);  .B int \fIoptions\fP, int *\fIovector\fP, int \fIovecsize\fP);
1353  .PP  .P
1354  The function \fBpcre_exec()\fR is called to match a subject string against a  The function \fBpcre_exec()\fP is called to match a subject string against a
1355  pre-compiled pattern, which is passed in the \fIcode\fR argument. If the  compiled pattern, which is passed in the \fIcode\fP argument. If the
1356  pattern has been studied, the result of the study should be passed in the  pattern was studied, the result of the study should be passed in the
1357  \fIextra\fR argument.  \fIextra\fP argument. You can call \fBpcre_exec()\fP with the same \fIcode\fP
1358    and \fIextra\fP arguments as many times as you like, in order to match
1359  Here is an example of a simple call to \fBpcre_exec()\fR:  different subject strings with the same pattern.
1360    .P
1361    This function is the main matching facility of the library, and it operates in
1362    a Perl-like manner. For specialist use there is also an alternative matching
1363    function, which is described
1364    .\" HTML <a href="#dfamatch">
1365    .\" </a>
1366    below
1367    .\"
1368    in the section about the \fBpcre_dfa_exec()\fP function.
1369    .P
1370    In most applications, the pattern will have been compiled (and optionally
1371    studied) in the same process that calls \fBpcre_exec()\fP. However, it is
1372    possible to save compiled patterns and study data, and then use them later
1373    in different processes, possibly even on different hosts. For a discussion
1374    about this, see the
1375    .\" HREF
1376    \fBpcreprecompile\fP
1377    .\"
1378    documentation.
1379    .P
1380    Here is an example of a simple call to \fBpcre_exec()\fP:
1381    .sp
1382    int rc;    int rc;
1383    int ovector[30];    int ovector[30];
1384    rc = pcre_exec(    rc = pcre_exec(
# Line 684  Here is an example of a simple call to \ Line 1388  Here is an example of a simple call to \
1388      11,             /* the length of the subject string */      11,             /* the length of the subject string */
1389      0,              /* start at offset 0 in the subject */      0,              /* start at offset 0 in the subject */
1390      0,              /* default options */      0,              /* default options */
1391      ovector,        /* vector for substring information */      ovector,        /* vector of integers for substring information */
1392      30);            /* number of elements in the vector */      30);            /* number of elements (NOT size in bytes) */
1393    .
1394  If the \fIextra\fR argument is not NULL, it must point to a \fBpcre_extra\fR  .
1395  data block. The \fBpcre_study()\fR function returns such a block (when it  .\" HTML <a name="extradata"></a>
1396    .SS "Extra data for \fBpcre_exec()\fR"
1397    .rs
1398    .sp
1399    If the \fIextra\fP argument is not NULL, it must point to a \fBpcre_extra\fP
1400    data block. The \fBpcre_study()\fP function returns such a block (when it
1401  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
1402  additional information in it. The fields in the block are as follows:  additional information in it. The \fBpcre_extra\fP block contains the following
1403    fields (not necessarily in this order):
1404    unsigned long int \fIflags\fR;  .sp
1405    void *\fIstudy_data\fR;    unsigned long int \fIflags\fP;
1406    unsigned long int \fImatch_limit\fR;    void *\fIstudy_data\fP;
1407    void *\fIcallout_data\fR;    void *\fIexecutable_jit\fP;
1408      unsigned long int \fImatch_limit\fP;
1409  The \fIflags\fR field is a bitmap that specifies which of the other fields    unsigned long int \fImatch_limit_recursion\fP;
1410      void *\fIcallout_data\fP;
1411      const unsigned char *\fItables\fP;
1412      unsigned char **\fImark\fP;
1413    .sp
1414    The \fIflags\fP field is a bitmap that specifies which of the other fields
1415  are set. The flag bits are:  are set. The flag bits are:
1416    .sp
1417    PCRE_EXTRA_STUDY_DATA    PCRE_EXTRA_STUDY_DATA
1418      PCRE_EXTRA_EXECUTABLE_JIT
1419    PCRE_EXTRA_MATCH_LIMIT    PCRE_EXTRA_MATCH_LIMIT
1420      PCRE_EXTRA_MATCH_LIMIT_RECURSION
1421    PCRE_EXTRA_CALLOUT_DATA    PCRE_EXTRA_CALLOUT_DATA
1422      PCRE_EXTRA_TABLES
1423  Other flag bits should be set to zero. The \fIstudy_data\fR field is set in the    PCRE_EXTRA_MARK
1424  \fBpcre_extra\fR block that is returned by \fBpcre_study()\fR, together with  .sp
1425  the appropriate flag bit. You should not set this yourself, but you can add to  Other flag bits should be set to zero. The \fIstudy_data\fP field and sometimes
1426  the block by setting the other fields.  the \fIexecutable_jit\fP field are set in the \fBpcre_extra\fP block that is
1427    returned by \fBpcre_study()\fP, together with the appropriate flag bits. You
1428  The \fImatch_limit\fR field provides a means of preventing PCRE from using up a  should not set these yourself, but you may add to the block by setting the
1429    other fields and their corresponding flag bits.
1430    .P
1431    The \fImatch_limit\fP field provides a means of preventing PCRE from using up a
1432  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,
1433  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
1434  classic example is the use of nested unlimited repeats. Internally, PCRE uses a  classic example is a pattern that uses nested unlimited repeats.
1435  function called \fBmatch()\fR which it calls repeatedly (sometimes  .P
1436  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
1437  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
1438  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
1439  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
1440    patterns that are not anchored, the count restarts from zero for each position
1441  The default limit for the library can be set when PCRE is built; the default  in the subject string.
1442    .P
1443    When \fBpcre_exec()\fP is called with a pattern that was successfully studied
1444    with the PCRE_STUDY_JIT_COMPILE option, the way that the matching is executed
1445    is entirely different. However, there is still the possibility of runaway
1446    matching that goes on for a very long time, and so the \fImatch_limit\fP value
1447    is also used in this case (but in a different way) to limit how long the
1448    matching can continue.
1449    .P
1450    The default value for the limit can be set when PCRE is built; the default
1451  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
1452  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
1453  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
1454  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
1455  exceeded, \fBpcre_exec()\fR returns PCRE_ERROR_MATCHLIMIT.  PCRE_ERROR_MATCHLIMIT.
1456    .P
1457  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
1458  which is described in the \fBpcrecallout\fR documentation.  instead of limiting the total number of times that \fBmatch()\fP is called, it
1459    limits the depth of recursion. The recursion depth is a smaller number than the
1460  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.
1461  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.
1462  first matching position. However, if a pattern was compiled with PCRE_ANCHORED,  .P
1463  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
1464  unachored at matching time.  used, or, when PCRE has been compiled to use memory on the heap instead of the
1465    stack, the amount of heap memory that can be used. This limit is not relevant,
1466  When PCRE_UTF8 was set at compile time, the validity of the subject as a UTF-8  and is ignored, if the pattern was successfully studied with
1467  string is automatically checked, and the value of \fIstartoffset\fR is also  PCRE_STUDY_JIT_COMPILE.
1468  checked to ensure that it points to the start of a UTF-8 character. If an  .P
1469  invalid UTF-8 sequence of bytes is found, \fBpcre_exec()\fR returns the error  The default value for \fImatch_limit_recursion\fP can be set when PCRE is
1470  PCRE_ERROR_BADUTF8. If \fIstartoffset\fR contains an invalid value,  built; the default default is the same value as the default for
1471  PCRE_ERROR_BADUTF8_OFFSET is returned.  \fImatch_limit\fP. You can override the default by suppling \fBpcre_exec()\fP
1472    with a \fBpcre_extra\fP block in which \fImatch_limit_recursion\fP is set, and
1473  If you already know that your subject is valid, and you want to skip these  PCRE_EXTRA_MATCH_LIMIT_RECURSION is set in the \fIflags\fP field. If the limit
1474  checks for performance reasons, you can set the PCRE_NO_UTF8_CHECK option when  is exceeded, \fBpcre_exec()\fP returns PCRE_ERROR_RECURSIONLIMIT.
1475  calling \fBpcre_exec()\fR. You might want to do this for the second and  .P
1476  subsequent calls to \fBpcre_exec()\fR if you are making repeated calls to find  The \fIcallout_data\fP field is used in conjunction with the "callout" feature,
1477  all the matches in a single subject string. However, you should be sure that  and is described in the
1478  the value of \fIstartoffset\fR points to the start of a UTF-8 character. When  .\" HREF
1479  PCRE_NO_UTF8_CHECK is set, the effect of passing an invalid UTF-8 string as a  \fBpcrecallout\fP
1480  subject, or a value of \fIstartoffset\fR that does not point to the start of a  .\"
1481  UTF-8 character, is undefined. Your program may crash.  documentation.
1482    .P
1483  There are also three further options that can be set only at matching time:  The \fItables\fP field is used to pass a character tables pointer to
1484    \fBpcre_exec()\fP; this overrides the value that is stored with the compiled
1485    pattern. A non-NULL value is stored with the compiled pattern only if custom
1486    tables were supplied to \fBpcre_compile()\fP via its \fItableptr\fP argument.
1487    If NULL is passed to \fBpcre_exec()\fP using this mechanism, it forces PCRE's
1488    internal tables to be used. This facility is helpful when re-using patterns
1489    that have been saved after compiling with an external set of tables, because
1490    the external tables might be at a different address when \fBpcre_exec()\fP is
1491    called. See the
1492    .\" HREF
1493    \fBpcreprecompile\fP
1494    .\"
1495    documentation for a discussion of saving compiled patterns for later use.
1496    .P
1497    If PCRE_EXTRA_MARK is set in the \fIflags\fP field, the \fImark\fP field must
1498    be set to point to a \fBchar *\fP variable. If the pattern contains any
1499    backtracking control verbs such as (*MARK:NAME), and the execution ends up with
1500    a name to pass back, a pointer to the name string (zero terminated) is placed
1501    in the variable pointed to by the \fImark\fP field. The names are within the
1502    compiled pattern; if you wish to retain such a name you must copy it before
1503    freeing the memory of a compiled pattern. If there is no name to pass back, the
1504    variable pointed to by the \fImark\fP field set to NULL. For details of the
1505    backtracking control verbs, see the section entitled
1506    .\" HTML <a href="pcrepattern#backtrackcontrol">
1507    .\" </a>
1508    "Backtracking control"
1509    .\"
1510    in the
1511    .\" HREF
1512    \fBpcrepattern\fP
1513    .\"
1514    documentation.
1515    .
1516    .
1517    .\" HTML <a name="execoptions"></a>
1518    .SS "Option bits for \fBpcre_exec()\fP"
1519    .rs
1520    .sp
1521    The unused bits of the \fIoptions\fP argument for \fBpcre_exec()\fP must be
1522    zero. The only bits that may be set are PCRE_ANCHORED, PCRE_NEWLINE_\fIxxx\fP,
1523    PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY, PCRE_NOTEMPTY_ATSTART,
1524    PCRE_NO_START_OPTIMIZE, PCRE_NO_UTF8_CHECK, PCRE_PARTIAL_SOFT, and
1525    PCRE_PARTIAL_HARD.
1526    .P
1527    If the pattern was successfully studied with the PCRE_STUDY_JIT_COMPILE option,
1528    the only supported options for JIT execution are PCRE_NO_UTF8_CHECK,
1529    PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY, and PCRE_NOTEMPTY_ATSTART. Note in
1530    particular that partial matching is not supported. If an unsupported option is
1531    used, JIT execution is disabled and the normal interpretive code in
1532    \fBpcre_exec()\fP is run.
1533    .sp
1534      PCRE_ANCHORED
1535    .sp
1536    The PCRE_ANCHORED option limits \fBpcre_exec()\fP to matching at the first
1537    matching position. If a pattern was compiled with PCRE_ANCHORED, or turned out
1538    to be anchored by virtue of its contents, it cannot be made unachored at
1539    matching time.
1540    .sp
1541      PCRE_BSR_ANYCRLF
1542      PCRE_BSR_UNICODE
1543    .sp
1544    These options (which are mutually exclusive) control what the \eR escape
1545    sequence matches. The choice is either to match only CR, LF, or CRLF, or to
1546    match any Unicode newline sequence. These options override the choice that was
1547    made or defaulted when the pattern was compiled.
1548    .sp
1549      PCRE_NEWLINE_CR
1550      PCRE_NEWLINE_LF
1551      PCRE_NEWLINE_CRLF
1552      PCRE_NEWLINE_ANYCRLF
1553      PCRE_NEWLINE_ANY
1554    .sp
1555    These options override the newline definition that was chosen or defaulted when
1556    the pattern was compiled. For details, see the description of
1557    \fBpcre_compile()\fP above. During matching, the newline choice affects the
1558    behaviour of the dot, circumflex, and dollar metacharacters. It may also alter
1559    the way the match position is advanced after a match failure for an unanchored
1560    pattern.
1561    .P
1562    When PCRE_NEWLINE_CRLF, PCRE_NEWLINE_ANYCRLF, or PCRE_NEWLINE_ANY is set, and a
1563    match attempt for an unanchored pattern fails when the current position is at a
1564    CRLF sequence, and the pattern contains no explicit matches for CR or LF
1565    characters, the match position is advanced by two characters instead of one, in
1566    other words, to after the CRLF.
1567    .P
1568    The above rule is a compromise that makes the most common cases work as
1569    expected. For example, if the pattern is .+A (and the PCRE_DOTALL option is not
1570    set), it does not match the string "\er\enA" because, after failing at the
1571    start, it skips both the CR and the LF before retrying. However, the pattern
1572    [\er\en]A does match that string, because it contains an explicit CR or LF
1573    reference, and so advances only by one character after the first failure.
1574    .P
1575    An explicit match for CR of LF is either a literal appearance of one of those
1576    characters, or one of the \er or \en escape sequences. Implicit matches such as
1577    [^X] do not count, nor does \es (which includes CR and LF in the characters
1578    that it matches).
1579    .P
1580    Notwithstanding the above, anomalous effects may still occur when CRLF is a
1581    valid newline sequence and explicit \er or \en escapes appear in the pattern.
1582    .sp
1583    PCRE_NOTBOL    PCRE_NOTBOL
1584    .sp
1585  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
1586  circumflex metacharacter should not match before it. Setting this without  beginning of a line, so the circumflex metacharacter should not match before
1587  PCRE_MULTILINE (at compile time) causes circumflex never to match.  it. Setting this without PCRE_MULTILINE (at compile time) causes circumflex
1588    never to match. This option affects only the behaviour of the circumflex
1589    metacharacter. It does not affect \eA.
1590    .sp
1591    PCRE_NOTEOL    PCRE_NOTEOL
1592    .sp
1593  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
1594  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
1595  it. Setting this without PCRE_MULTILINE (at compile time) causes dollar never  mode) a newline immediately before it. Setting this without PCRE_MULTILINE (at
1596  to match.  compile time) causes dollar never to match. This option affects only the
1597    behaviour of the dollar metacharacter. It does not affect \eZ or \ez.
1598    .sp
1599    PCRE_NOTEMPTY    PCRE_NOTEMPTY
1600    .sp
1601  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
1602  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
1603  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
1604    .sp
1605    a?b?    a?b?
1606    .sp
1607  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
1608  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
1609  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".
1610    .sp
1611  Perl has no direct equivalent of PCRE_NOTEMPTY, but it does make a special case    PCRE_NOTEMPTY_ATSTART
1612  of a pattern match of the empty string within its \fBsplit()\fR function, and  .sp
1613  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
1614  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
1615  PCRE_NOTEMPTY set, and then if that fails by advancing the starting offset (see  can occur only if the pattern contains \eK.
1616  below) and trying an ordinary match again.  .P
1617    Perl has no direct equivalent of PCRE_NOTEMPTY or PCRE_NOTEMPTY_ATSTART, but it
1618  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
1619  \fIsubject\fR, a length in \fIlength\fR, and a starting byte offset in  \fBsplit()\fP function, and when using the /g modifier. It is possible to
1620  \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
1621  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
1622  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
1623    ordinary match again. There is some code that demonstrates how to do this in
1624  If the pattern was compiled with the PCRE_UTF8 option, the subject must be a  the
1625  sequence of bytes that is a valid UTF-8 string, and the starting offset must  .\" HREF
1626  point to the beginning of a UTF-8 character. If an invalid UTF-8 string or  \fBpcredemo\fP
1627  offset is passed, an error (either PCRE_ERROR_BADUTF8 or  .\"
1628  PCRE_ERROR_BADUTF8_OFFSET) is returned, unless the option PCRE_NO_UTF8_CHECK is  sample program. In the most general case, you have to check to see if the
1629  set, in which case PCRE's behaviour is not defined.  newline convention recognizes CRLF as a newline, and if so, and the current
1630    character is CR followed by LF, advance the starting offset by two characters
1631    instead of one.
1632    .sp
1633      PCRE_NO_START_OPTIMIZE
1634    .sp
1635    There are a number of optimizations that \fBpcre_exec()\fP uses at the start of
1636    a match, in order to speed up the process. For example, if it is known that an
1637    unanchored match must start with a specific character, it searches the subject
1638    for that character, and fails immediately if it cannot find it, without
1639    actually running the main matching function. This means that a special item
1640    such as (*COMMIT) at the start of a pattern is not considered until after a
1641    suitable starting point for the match has been found. When callouts or (*MARK)
1642    items are in use, these "start-up" optimizations can cause them to be skipped
1643    if the pattern is never actually used. The start-up optimizations are in effect
1644    a pre-scan of the subject that takes place before the pattern is run.
1645    .P
1646    The PCRE_NO_START_OPTIMIZE option disables the start-up optimizations, possibly
1647    causing performance to suffer, but ensuring that in cases where the result is
1648    "no match", the callouts do occur, and that items such as (*COMMIT) and (*MARK)
1649    are considered at every possible starting position in the subject string. If
1650    PCRE_NO_START_OPTIMIZE is set at compile time, it cannot be unset at matching
1651    time.
1652    .P
1653    Setting PCRE_NO_START_OPTIMIZE can change the outcome of a matching operation.
1654    Consider the pattern
1655    .sp
1656      (*COMMIT)ABC
1657    .sp
1658    When this is compiled, PCRE records the fact that a match must start with the
1659    character "A". Suppose the subject string is "DEFABC". The start-up
1660    optimization scans along the subject, finds "A" and runs the first match
1661    attempt from there. The (*COMMIT) item means that the pattern must match the
1662    current starting position, which in this case, it does. However, if the same
1663    match is run with PCRE_NO_START_OPTIMIZE set, the initial scan along the
1664    subject string does not happen. The first match attempt is run starting from
1665    "D" and when this fails, (*COMMIT) prevents any further matches being tried, so
1666    the overall result is "no match". If the pattern is studied, more start-up
1667    optimizations may be used. For example, a minimum length for the subject may be
1668    recorded. Consider the pattern
1669    .sp
1670      (*MARK:A)(X|Y)
1671    .sp
1672    The minimum length for a match is one character. If the subject is "ABC", there
1673    will be attempts to match "ABC", "BC", "C", and then finally an empty string.
1674    If the pattern is studied, the final attempt does not take place, because PCRE
1675    knows that the subject is too short, and so the (*MARK) is never encountered.
1676    In this case, studying the pattern does not affect the overall match result,
1677    which is still "no match", but it does affect the auxiliary information that is
1678    returned.
1679    .sp
1680      PCRE_NO_UTF8_CHECK
1681    .sp
1682    When PCRE_UTF8 is set at compile time, the validity of the subject as a UTF-8
1683    string is automatically checked when \fBpcre_exec()\fP is subsequently called.
1684    The value of \fIstartoffset\fP is also checked to ensure that it points to the
1685    start of a UTF-8 character. There is a discussion about the validity of UTF-8
1686    strings in the
1687    .\" HTML <a href="pcre.html#utf8strings">
1688    .\" </a>
1689    section on UTF-8 support
1690    .\"
1691    in the main
1692    .\" HREF
1693    \fBpcre\fP
1694    .\"
1695    page. If an invalid UTF-8 sequence of bytes is found, \fBpcre_exec()\fP returns
1696    the error PCRE_ERROR_BADUTF8 or, if PCRE_PARTIAL_HARD is set and the problem is
1697    a truncated UTF-8 character at the end of the subject, PCRE_ERROR_SHORTUTF8. In
1698    both cases, information about the precise nature of the error may also be
1699    returned (see the descriptions of these errors in the section entitled \fIError
1700    return values from\fP \fBpcre_exec()\fP
1701    .\" HTML <a href="#errorlist">
1702    .\" </a>
1703    below).
1704    .\"
1705    If \fIstartoffset\fP contains a value that does not point to the start of a
1706    UTF-8 character (or to the end of the subject), PCRE_ERROR_BADUTF8_OFFSET is
1707    returned.
1708    .P
1709    If you already know that your subject is valid, and you want to skip these
1710    checks for performance reasons, you can set the PCRE_NO_UTF8_CHECK option when
1711    calling \fBpcre_exec()\fP. You might want to do this for the second and
1712    subsequent calls to \fBpcre_exec()\fP if you are making repeated calls to find
1713    all the matches in a single subject string. However, you should be sure that
1714    the value of \fIstartoffset\fP points to the start of a UTF-8 character (or the
1715    end of the subject). When PCRE_NO_UTF8_CHECK is set, the effect of passing an
1716    invalid UTF-8 string as a subject or an invalid value of \fIstartoffset\fP is
1717    undefined. Your program may crash.
1718    .sp
1719      PCRE_PARTIAL_HARD
1720      PCRE_PARTIAL_SOFT
1721    .sp
1722    These options turn on the partial matching feature. For backwards
1723    compatibility, PCRE_PARTIAL is a synonym for PCRE_PARTIAL_SOFT. A partial match
1724    occurs if the end of the subject string is reached successfully, but there are
1725    not enough subject characters to complete the match. If this happens when
1726    PCRE_PARTIAL_SOFT (but not PCRE_PARTIAL_HARD) is set, matching continues by
1727    testing any remaining alternatives. Only if no complete match can be found is
1728    PCRE_ERROR_PARTIAL returned instead of PCRE_ERROR_NOMATCH. In other words,
1729    PCRE_PARTIAL_SOFT says that the caller is prepared to handle a partial match,
1730    but only if no complete match can be found.
1731    .P
1732    If PCRE_PARTIAL_HARD is set, it overrides PCRE_PARTIAL_SOFT. In this case, if a
1733    partial match is found, \fBpcre_exec()\fP immediately returns
1734    PCRE_ERROR_PARTIAL, without considering any other alternatives. In other words,
1735    when PCRE_PARTIAL_HARD is set, a partial match is considered to be more
1736    important that an alternative complete match.
1737    .P
1738    In both cases, the portion of the string that was inspected when the partial
1739    match was found is set as the first matching string. There is a more detailed
1740    discussion of partial and multi-segment matching, with examples, in the
1741    .\" HREF
1742    \fBpcrepartial\fP
1743    .\"
1744    documentation.
1745    .
1746    .
1747    .SS "The string to be matched by \fBpcre_exec()\fP"
1748    .rs
1749    .sp
1750    The subject string is passed to \fBpcre_exec()\fP as a pointer in
1751    \fIsubject\fP, a length (in bytes) in \fIlength\fP, and a starting byte offset
1752    in \fIstartoffset\fP. If this is negative or greater than the length of the
1753    subject, \fBpcre_exec()\fP returns PCRE_ERROR_BADOFFSET. When the starting
1754    offset is zero, the search for a match starts at the beginning of the subject,
1755    and this is by far the most common case. In UTF-8 mode, the byte offset must
1756    point to the start of a UTF-8 character (or the end of the subject). Unlike the
1757    pattern string, the subject may contain binary zero bytes.
1758    .P
1759  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
1760  same subject by calling \fBpcre_exec()\fR again after a previous success.  same subject by calling \fBpcre_exec()\fP again after a previous success.
1761  Setting \fIstartoffset\fR differs from just passing over a shortened string and  Setting \fIstartoffset\fP differs from just passing over a shortened string and
1762  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
1763  lookbehind. For example, consider the pattern  lookbehind. For example, consider the pattern
1764    .sp
1765    \\Biss\\B    \eBiss\eB
1766    .sp
1767  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
1768  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
1769  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
1770  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
1771  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
1772  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
1773  \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
1774  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
1775  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.
1776    .P
1777    Finding all the matches in a subject is tricky when the pattern can match an
1778    empty string. It is possible to emulate Perl's /g behaviour by first trying the
1779    match again at the same offset, with the PCRE_NOTEMPTY_ATSTART and
1780    PCRE_ANCHORED options, and then if that fails, advancing the starting offset
1781    and trying an ordinary match again. There is some code that demonstrates how to
1782    do this in the
1783    .\" HREF
1784    \fBpcredemo\fP
1785    .\"
1786    sample program. In the most general case, you have to check to see if the
1787    newline convention recognizes CRLF as a newline, and if so, and the current
1788    character is CR followed by LF, advance the starting offset by two characters
1789    instead of one.
1790    .P
1791  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
1792  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
1793  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.
1794    .
1795    .
1796    .SS "How \fBpcre_exec()\fP returns captured substrings"
1797    .rs
1798    .sp
1799  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
1800  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
1801  pattern. Following the usage in Jeffrey Friedl's book, this is called  pattern. Following the usage in Jeffrey Friedl's book, this is called
1802  "capturing" in what follows, and the phrase "capturing subpattern" is used for  "capturing" in what follows, and the phrase "capturing subpattern" is used for
1803  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
1804  kinds of parenthesized subpattern that do not cause substrings to be captured.  kinds of parenthesized subpattern that do not cause substrings to be captured.
1805    .P
1806  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
1807  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
1808  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
1809  back captured substrings, each substring using a pair of integers. The  argument is NOT the size of \fIovector\fP in bytes.
1810  remaining third of the vector is used as workspace by \fBpcre_exec()\fR while  .P
1811  matching capturing subpatterns, and is not available for passing back  The first two-thirds of the vector is used to pass back captured substrings,
1812  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
1813  three. If it is not, it is rounded down.  used as workspace by \fBpcre_exec()\fP while matching capturing subpatterns,
1814    and is not available for passing back information. The number passed in
1815  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
1816  returned in pairs of integers, starting at the beginning of \fIovector\fR, and  rounded down.
1817  continuing up to two-thirds of its length at the most. The first element of a  .P
1818  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
1819  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
1820  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
1821  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
1822  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
1823  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
1824  subpatterns, the return value from a successful match is 1, indicating that  mode. They are not character counts.
1825  just the first pair of offsets has been set.  .P
1826    The first pair of integers, \fIovector[0]\fP and \fIovector[1]\fP, identify the
1827  Some convenience functions are provided for extracting the captured substrings  portion of the subject string matched by the entire pattern. The next pair is
1828  as separate strings. These are described in the following section.  used for the first capturing subpattern, and so on. The value returned by
1829    \fBpcre_exec()\fP is one more than the highest numbered pair that has been set.
1830  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
1831  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
1832  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.
1833  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.  
   
1834  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
1835  string that it matched that gets returned.  string that it matched that is returned.
1836    .P
1837  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
1838  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
1839  value of zero. In particular, if the substring offsets are not of interest,  returns a value of zero. If neither the actual string matched not any captured
1840  \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
1841  \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
1842  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
1843  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
1844  to supply an \fIovector\fR.  is usually advisable to supply an \fIovector\fP of reasonable size.
1845    .P
1846  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
1847    in fact the vector is exactly the right size for the final match. For example,
1848    consider the pattern
1849    .sp
1850      (a)(?:(b)c|bd)
1851    .sp
1852    If a vector of 6 elements (allowing for only 1 captured substring) is given
1853    with subject string "abd", \fBpcre_exec()\fP will try to set the second
1854    captured string, thereby recording a vector overflow, before failing to match
1855    "c" and backing up to try the second alternative. The zero return, however,
1856    does correctly indicate that the maximum number of slots (namely 2) have been
1857    filled. In similar cases where there is temporary overflow, but the final
1858    number of used slots is actually less than the maximum, a non-zero value is
1859    returned.
1860    .P
1861    The \fBpcre_fullinfo()\fP function can be used to find out how many capturing
1862  subpatterns there are in a compiled pattern. The smallest size for  subpatterns there are in a compiled pattern. The smallest size for
1863  \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
1864  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.
1865    .P
1866  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
1867    the subject when subpattern \fIn\fP has not been used at all. For example, if
1868    the string "abc" is matched against the pattern (a|(z))(bc) the return from the
1869    function is 4, and subpatterns 1 and 3 are matched, but 2 is not. When this
1870    happens, both values in the offset pairs corresponding to unused subpatterns
1871    are set to -1.
1872    .P
1873    Offset values that correspond to unused subpatterns at the end of the
1874    expression are also set to -1. For example, if the string "abc" is matched
1875    against the pattern (abc)(x(yz)?)? subpatterns 2 and 3 are not matched. The
1876    return from the function is 2, because the highest used capturing subpattern
1877    number is 1, and the offsets for for the second and third capturing subpatterns
1878    (assuming the vector is large enough, of course) are set to -1.
1879    .P
1880    \fBNote\fP: Elements in the first two-thirds of \fIovector\fP that do not
1881    correspond to capturing parentheses in the pattern are never changed. That is,
1882    if a pattern contains \fIn\fP capturing parentheses, no more than
1883    \fIovector[0]\fP to \fIovector[2n+1]\fP are set by \fBpcre_exec()\fP. The other
1884    elements (in the first two-thirds) retain whatever values they previously had.
1885    .P
1886    Some convenience functions are provided for extracting the captured substrings
1887    as separate strings. These are described below.
1888    .
1889    .
1890    .\" HTML <a name="errorlist"></a>
1891    .SS "Error return values from \fBpcre_exec()\fP"
1892    .rs
1893    .sp
1894    If \fBpcre_exec()\fP fails, it returns a negative number. The following are
1895  defined in the header file:  defined in the header file:
1896    .sp
1897    PCRE_ERROR_NOMATCH        (-1)    PCRE_ERROR_NOMATCH        (-1)
1898    .sp
1899  The subject string did not match the pattern.  The subject string did not match the pattern.
1900    .sp
1901    PCRE_ERROR_NULL           (-2)    PCRE_ERROR_NULL           (-2)
1902    .sp
1903  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
1904  NULL and \fIovecsize\fR was not zero.  NULL and \fIovecsize\fP was not zero.
1905    .sp
1906    PCRE_ERROR_BADOPTION      (-3)    PCRE_ERROR_BADOPTION      (-3)
1907    .sp
1908  An unrecognized bit was set in the \fIoptions\fR argument.  An unrecognized bit was set in the \fIoptions\fP argument.
1909    .sp
1910    PCRE_ERROR_BADMAGIC       (-4)    PCRE_ERROR_BADMAGIC       (-4)
1911    .sp
1912  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
1913  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
1914  magic number isn't present.  compiled in an environment of one endianness is run in an environment with the
1915    other endianness. This is the error that PCRE gives when the magic number is
1916    PCRE_ERROR_UNKNOWN_NODE   (-5)  not present.
1917    .sp
1918      PCRE_ERROR_UNKNOWN_OPCODE (-5)
1919    .sp
1920  While running the pattern match, an unknown item was encountered in the  While running the pattern match, an unknown item was encountered in the
1921  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
1922  of the compiled pattern.  of the compiled pattern.
1923    .sp
1924    PCRE_ERROR_NOMEMORY       (-6)    PCRE_ERROR_NOMEMORY       (-6)
1925    .sp
1926  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
1927  \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
1928  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
1929  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
1930  the end of matching.  automatically freed at the end of matching.
1931    .P
1932    This error is also given if \fBpcre_stack_malloc()\fP fails in
1933    \fBpcre_exec()\fP. This can happen only when PCRE has been compiled with
1934    \fB--disable-stack-for-recursion\fP.
1935    .sp
1936    PCRE_ERROR_NOSUBSTRING    (-7)    PCRE_ERROR_NOSUBSTRING    (-7)
1937    .sp
1938  This error is used by the \fBpcre_copy_substring()\fR,  This error is used by the \fBpcre_copy_substring()\fP,
1939  \fBpcre_get_substring()\fR, and \fBpcre_get_substring_list()\fR functions (see  \fBpcre_get_substring()\fP, and \fBpcre_get_substring_list()\fP functions (see
1940  below). It is never returned by \fBpcre_exec()\fR.  below). It is never returned by \fBpcre_exec()\fP.
1941    .sp
1942    PCRE_ERROR_MATCHLIMIT     (-8)    PCRE_ERROR_MATCHLIMIT     (-8)
1943    .sp
1944  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
1945  field in a \fBpcre_extra\fR structure (or defaulted) was reached. See the  \fBpcre_extra\fP structure (or defaulted) was reached. See the description
1946  description above.  above.
1947    .sp
1948    PCRE_ERROR_CALLOUT        (-9)    PCRE_ERROR_CALLOUT        (-9)
1949    .sp
1950  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
1951  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
1952  \fBpcrecallout\fR documentation for details.  .\" HREF
1953    \fBpcrecallout\fP
1954    .\"
1955    documentation for details.
1956    .sp
1957    PCRE_ERROR_BADUTF8        (-10)    PCRE_ERROR_BADUTF8        (-10)
1958    .sp
1959  A string that contains an invalid UTF-8 byte sequence was passed as a subject.  A string that contains an invalid UTF-8 byte sequence was passed as a subject,
1960    and the PCRE_NO_UTF8_CHECK option was not set. If the size of the output vector
1961    (\fIovecsize\fP) is at least 2, the byte offset to the start of the the invalid
1962    UTF-8 character is placed in the first element, and a reason code is placed in
1963    the second element. The reason codes are listed in the
1964    .\" HTML <a href="#badutf8reasons">
1965    .\" </a>
1966    following section.
1967    .\"
1968    For backward compatibility, if PCRE_PARTIAL_HARD is set and the problem is a
1969    truncated UTF-8 character at the end of the subject (reason codes 1 to 5),
1970    PCRE_ERROR_SHORTUTF8 is returned instead of PCRE_ERROR_BADUTF8.
1971    .sp
1972    PCRE_ERROR_BADUTF8_OFFSET (-11)    PCRE_ERROR_BADUTF8_OFFSET (-11)
1973    .sp
1974  The UTF-8 byte sequence that was passed as a subject was valid, but the value  The UTF-8 byte sequence that was passed as a subject was checked and found to
1975  of \fIstartoffset\fR did not point to the beginning of a UTF-8 character.  be valid (the PCRE_NO_UTF8_CHECK option was not set), but the value of
1976    \fIstartoffset\fP did not point to the beginning of a UTF-8 character or the
1977  .SH EXTRACTING CAPTURED SUBSTRINGS BY NUMBER  end of the subject.
1978    .sp
1979      PCRE_ERROR_PARTIAL        (-12)
1980    .sp
1981    The subject string did not match, but it did match partially. See the
1982    .\" HREF
1983    \fBpcrepartial\fP
1984    .\"
1985    documentation for details of partial matching.
1986    .sp
1987      PCRE_ERROR_BADPARTIAL     (-13)
1988    .sp
1989    This code is no longer in use. It was formerly returned when the PCRE_PARTIAL
1990    option was used with a compiled pattern containing items that were not
1991    supported for partial matching. From release 8.00 onwards, there are no
1992    restrictions on partial matching.
1993    .sp
1994      PCRE_ERROR_INTERNAL       (-14)
1995    .sp
1996    An unexpected internal error has occurred. This error could be caused by a bug
1997    in PCRE or by overwriting of the compiled pattern.
1998    .sp
1999      PCRE_ERROR_BADCOUNT       (-15)
2000    .sp
2001    This error is given if the value of the \fIovecsize\fP argument is negative.
2002    .sp
2003      PCRE_ERROR_RECURSIONLIMIT (-21)
2004    .sp
2005    The internal recursion limit, as specified by the \fImatch_limit_recursion\fP
2006    field in a \fBpcre_extra\fP structure (or defaulted) was reached. See the
2007    description above.
2008    .sp
2009      PCRE_ERROR_BADNEWLINE     (-23)
2010    .sp
2011    An invalid combination of PCRE_NEWLINE_\fIxxx\fP options was given.
2012    .sp
2013      PCRE_ERROR_BADOFFSET      (-24)
2014    .sp
2015    The value of \fIstartoffset\fP was negative or greater than the length of the
2016    subject, that is, the value in \fIlength\fP.
2017    .sp
2018      PCRE_ERROR_SHORTUTF8      (-25)
2019    .sp
2020    This error is returned instead of PCRE_ERROR_BADUTF8 when the subject string
2021    ends with a truncated UTF-8 character and the PCRE_PARTIAL_HARD option is set.
2022    Information about the failure is returned as for PCRE_ERROR_BADUTF8. It is in
2023    fact sufficient to detect this case, but this special error code for
2024    PCRE_PARTIAL_HARD precedes the implementation of returned information; it is
2025    retained for backwards compatibility.
2026    .sp
2027      PCRE_ERROR_RECURSELOOP    (-26)
2028    .sp
2029    This error is returned when \fBpcre_exec()\fP detects a recursion loop within
2030    the pattern. Specifically, it means that either the whole pattern or a
2031    subpattern has been called recursively for the second time at the same position
2032    in the subject string. Some simple patterns that might do this are detected and
2033    faulted at compile time, but more complicated cases, in particular mutual
2034    recursions between two different subpatterns, cannot be detected until run
2035    time.
2036    .sp
2037      PCRE_ERROR_JIT_STACKLIMIT (-27)
2038    .sp
2039    This error is returned when a pattern that was successfully studied using the
2040    PCRE_STUDY_JIT_COMPILE option is being matched, but the memory available for
2041    the just-in-time processing stack is not large enough. See the
2042    .\" HREF
2043    \fBpcrejit\fP
2044    .\"
2045    documentation for more details.
2046    .P
2047    Error numbers -16 to -20 and -22 are not used by \fBpcre_exec()\fP.
2048    .
2049    .
2050    .\" HTML <a name="badutf8reasons"></a>
2051    .SS "Reason codes for invalid UTF-8 strings"
2052    .rs
2053    .sp
2054    When \fBpcre_exec()\fP returns either PCRE_ERROR_BADUTF8 or
2055    PCRE_ERROR_SHORTUTF8, and the size of the output vector (\fIovecsize\fP) is at
2056    least 2, the offset of the start of the invalid UTF-8 character is placed in
2057    the first output vector element (\fIovector[0]\fP) and a reason code is placed
2058    in the second element (\fIovector[1]\fP). The reason codes are given names in
2059    the \fBpcre.h\fP header file:
2060    .sp
2061      PCRE_UTF8_ERR1
2062      PCRE_UTF8_ERR2
2063      PCRE_UTF8_ERR3
2064      PCRE_UTF8_ERR4
2065      PCRE_UTF8_ERR5
2066    .sp
2067    The string ends with a truncated UTF-8 character; the code specifies how many
2068    bytes are missing (1 to 5). Although RFC 3629 restricts UTF-8 characters to be
2069    no longer than 4 bytes, the encoding scheme (originally defined by RFC 2279)
2070    allows for up to 6 bytes, and this is checked first; hence the possibility of
2071    4 or 5 missing bytes.
2072    .sp
2073      PCRE_UTF8_ERR6
2074      PCRE_UTF8_ERR7
2075      PCRE_UTF8_ERR8
2076      PCRE_UTF8_ERR9
2077      PCRE_UTF8_ERR10
2078    .sp
2079    The two most significant bits of the 2nd, 3rd, 4th, 5th, or 6th byte of the
2080    character do not have the binary value 0b10 (that is, either the most
2081    significant bit is 0, or the next bit is 1).
2082    .sp
2083      PCRE_UTF8_ERR11
2084      PCRE_UTF8_ERR12
2085    .sp
2086    A character that is valid by the RFC 2279 rules is either 5 or 6 bytes long;
2087    these code points are excluded by RFC 3629.
2088    .sp
2089      PCRE_UTF8_ERR13
2090    .sp
2091    A 4-byte character has a value greater than 0x10fff; these code points are
2092    excluded by RFC 3629.
2093    .sp
2094      PCRE_UTF8_ERR14
2095    .sp
2096    A 3-byte character has a value in the range 0xd800 to 0xdfff; this range of
2097    code points are reserved by RFC 3629 for use with UTF-16, and so are excluded
2098    from UTF-8.
2099    .sp
2100      PCRE_UTF8_ERR15
2101      PCRE_UTF8_ERR16
2102      PCRE_UTF8_ERR17
2103      PCRE_UTF8_ERR18
2104      PCRE_UTF8_ERR19
2105    .sp
2106    A 2-, 3-, 4-, 5-, or 6-byte character is "overlong", that is, it codes for a
2107    value that can be represented by fewer bytes, which is invalid. For example,
2108    the two bytes 0xc0, 0xae give the value 0x2e, whose correct coding uses just
2109    one byte.
2110    .sp
2111      PCRE_UTF8_ERR20
2112    .sp
2113    The two most significant bits of the first byte of a character have the binary
2114    value 0b10 (that is, the most significant bit is 1 and the second is 0). Such a
2115    byte can only validly occur as the second or subsequent byte of a multi-byte
2116    character.
2117    .sp
2118      PCRE_UTF8_ERR21
2119    .sp
2120    The first byte of a character has the value 0xfe or 0xff. These values can
2121    never occur in a valid UTF-8 string.
2122    .
2123    .
2124    .SH "EXTRACTING CAPTURED SUBSTRINGS BY NUMBER"
2125  .rs  .rs
2126  .sp  .sp
2127  .B int pcre_copy_substring(const char *\fIsubject\fR, int *\fIovector\fR,  .B int pcre_copy_substring(const char *\fIsubject\fP, int *\fIovector\fP,
2128  .ti +5n  .ti +5n
2129  .B int \fIstringcount\fR, int \fIstringnumber\fR, char *\fIbuffer\fR,  .B int \fIstringcount\fP, int \fIstringnumber\fP, char *\fIbuffer\fP,
2130  .ti +5n  .ti +5n
2131  .B int \fIbuffersize\fR);  .B int \fIbuffersize\fP);
2132  .PP  .PP
2133  .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,  
2134  .ti +5n  .ti +5n
2135  .B int \fIstringcount\fR, int \fIstringnumber\fR,  .B int \fIstringcount\fP, int \fIstringnumber\fP,
2136  .ti +5n  .ti +5n
2137  .B const char **\fIstringptr\fR);  .B const char **\fIstringptr\fP);
2138  .PP  .PP
2139  .br  .B int pcre_get_substring_list(const char *\fIsubject\fP,
 .B int pcre_get_substring_list(const char *\fIsubject\fR,  
2140  .ti +5n  .ti +5n
2141  .B int *\fIovector\fR, int \fIstringcount\fR, "const char ***\fIlistptr\fR);"  .B int *\fIovector\fP, int \fIstringcount\fP, "const char ***\fIlistptr\fP);"
2142  .PP  .PP
2143  Captured substrings can be accessed directly by using the offsets returned by  Captured substrings can be accessed directly by using the offsets returned by
2144  \fBpcre_exec()\fR in \fIovector\fR. For convenience, the functions  \fBpcre_exec()\fP in \fIovector\fP. For convenience, the functions
2145  \fBpcre_copy_substring()\fR, \fBpcre_get_substring()\fR, and  \fBpcre_copy_substring()\fP, \fBpcre_get_substring()\fP, and
2146  \fBpcre_get_substring_list()\fR are provided for extracting captured substrings  \fBpcre_get_substring_list()\fP are provided for extracting captured substrings
2147  as new, separate, zero-terminated strings. These functions identify substrings  as new, separate, zero-terminated strings. These functions identify substrings
2148  by number. The next section describes functions for extracting named  by number. The next section describes functions for extracting named
2149  substrings. A substring that contains a binary zero is correctly extracted and  substrings.
2150  has a further zero added on the end, but the result is not, of course,  .P
2151  a C string.  A substring that contains a binary zero is correctly extracted and has a
2152    further zero added on the end, but the result is not, of course, a C string.
2153    However, you can process such a string by referring to the length that is
2154    returned by \fBpcre_copy_substring()\fP and \fBpcre_get_substring()\fP.
2155    Unfortunately, the interface to \fBpcre_get_substring_list()\fP is not adequate
2156    for handling strings containing binary zeros, because the end of the final
2157    string is not independently indicated.
2158    .P
2159  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:
2160  \fIsubject\fR is the subject string which has just been successfully matched,  \fIsubject\fP is the subject string that has just been successfully matched,
2161  \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
2162  \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
2163  captured by the match, including the substring that matched the entire regular  captured by the match, including the substring that matched the entire regular
2164  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
2165  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
2166  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
2167  the vector divided by three.  number of elements in the vector divided by three.
2168    .P
2169  The functions \fBpcre_copy_substring()\fR and \fBpcre_get_substring()\fR  The functions \fBpcre_copy_substring()\fP and \fBpcre_get_substring()\fP
2170  extract a single substring, whose number is given as \fIstringnumber\fR. A  extract a single substring, whose number is given as \fIstringnumber\fP. A
2171  value of zero extracts the substring that matched the entire pattern, while  value of zero extracts the substring that matched the entire pattern, whereas
2172  higher values extract the captured substrings. For \fBpcre_copy_substring()\fR,  higher values extract the captured substrings. For \fBpcre_copy_substring()\fP,
2173  the string is placed in \fIbuffer\fR, whose length is given by  the string is placed in \fIbuffer\fP, whose length is given by
2174  \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
2175  obtained via \fBpcre_malloc\fR, and its address is returned via  obtained via \fBpcre_malloc\fP, and its address is returned via
2176  \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
2177  including the terminating zero, or one of  including the terminating zero, or one of these error codes:
2178    .sp
2179    PCRE_ERROR_NOMEMORY       (-6)    PCRE_ERROR_NOMEMORY       (-6)
2180    .sp
2181  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
2182  memory failed for \fBpcre_get_substring()\fR.  memory failed for \fBpcre_get_substring()\fP.
2183    .sp
2184    PCRE_ERROR_NOSUBSTRING    (-7)    PCRE_ERROR_NOSUBSTRING    (-7)
2185    .sp
2186  There is no substring whose number is \fIstringnumber\fR.  There is no substring whose number is \fIstringnumber\fP.
2187    .P
2188  The \fBpcre_get_substring_list()\fR function extracts all available substrings  The \fBpcre_get_substring_list()\fP function extracts all available substrings
2189  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
2190  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
2191  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
2192  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
2193  function is zero if all went well, or  function is zero if all went well, or the error code
2194    .sp
2195    PCRE_ERROR_NOMEMORY       (-6)    PCRE_ERROR_NOMEMORY       (-6)
2196    .sp
2197  if the attempt to get the memory block failed.  if the attempt to get the memory block failed.
2198    .P
2199  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
2200  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
2201  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
2202  string. This can be distinguished from a genuine zero-length substring by  string. This can be distinguished from a genuine zero-length substring by
2203  inspecting the appropriate offset in \fIovector\fR, which is negative for unset  inspecting the appropriate offset in \fIovector\fP, which is negative for unset
2204  substrings.  substrings.
2205    .P
2206  The two convenience functions \fBpcre_free_substring()\fR and  The two convenience functions \fBpcre_free_substring()\fP and
2207  \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
2208  a previous call of \fBpcre_get_substring()\fR or  a previous call of \fBpcre_get_substring()\fP or
2209  \fBpcre_get_substring_list()\fR, respectively. They do nothing more than call  \fBpcre_get_substring_list()\fP, respectively. They do nothing more than call
2210  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
2211  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
2212  linked via a special interface to another programming language which cannot use  linked via a special interface to another programming language that cannot use
2213  \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
2214  provided.  provided.
2215    .
2216  .SH EXTRACTING CAPTURED SUBSTRINGS BY NAME  .
2217    .SH "EXTRACTING CAPTURED SUBSTRINGS BY NAME"
2218  .rs  .rs
2219  .sp  .sp
2220  .B int pcre_copy_named_substring(const pcre *\fIcode\fR,  .B int pcre_get_stringnumber(const pcre *\fIcode\fP,
2221  .ti +5n  .ti +5n
2222  .B const char *\fIsubject\fR, int *\fIovector\fR,  .B const char *\fIname\fP);
2223    .PP
2224    .B int pcre_copy_named_substring(const pcre *\fIcode\fP,
2225  .ti +5n  .ti +5n
2226  .B int \fIstringcount\fR, const char *\fIstringname\fR,  .B const char *\fIsubject\fP, int *\fIovector\fP,
2227  .ti +5n  .ti +5n
2228  .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,  
2229  .ti +5n  .ti +5n
2230  .B const char *\fIname\fR);  .B char *\fIbuffer\fP, int \fIbuffersize\fP);
2231  .PP  .PP
2232  .br  .B int pcre_get_named_substring(const pcre *\fIcode\fP,
 .B int pcre_get_named_substring(const pcre *\fIcode\fR,  
2233  .ti +5n  .ti +5n
2234  .B const char *\fIsubject\fR, int *\fIovector\fR,  .B const char *\fIsubject\fP, int *\fIovector\fP,
2235  .ti +5n  .ti +5n
2236  .B int \fIstringcount\fR, const char *\fIstringname\fR,  .B int \fIstringcount\fP, const char *\fIstringname\fP,
2237  .ti +5n  .ti +5n
2238  .B const char **\fIstringptr\fR);  .B const char **\fIstringptr\fP);
2239  .PP  .PP
2240  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.
2241  can be done by calling \fBpcre_get_stringnumber()\fR. The first argument is the  For example, for this pattern
2242  compiled pattern, and the second is the name. For example, for this pattern  .sp
2243      (a+)b(?<xxx>\ed+)...
2244    ab(?<xxx>\\d+)...  .sp
2245    the number of the subpattern called "xxx" is 2. If the name is known to be
2246  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
2247  extract the substring directly, or use one of the functions described in the  calling \fBpcre_get_stringnumber()\fP. The first argument is the compiled
2248  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
2249  whole job.  subpattern number, or PCRE_ERROR_NOSUBSTRING (-7) if there is no subpattern of
2250    that name.
2251  Most of the arguments of \fIpcre_copy_named_substring()\fR and  .P
2252  \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
2253  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
2254  differences.  two functions that do the whole job.
2255    .P
2256    Most of the arguments of \fBpcre_copy_named_substring()\fP and
2257    \fBpcre_get_named_substring()\fP are the same as those for the similarly named
2258    functions that extract by number. As these are described in the previous
2259    section, they are not re-described here. There are just two differences:
2260    .P
2261  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
2262  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
2263  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
2264  translation table.  translation table.
2265    .P
2266  These functions call \fBpcre_get_stringnumber()\fR, and if it succeeds, they  These functions call \fBpcre_get_stringnumber()\fP, and if it succeeds, they
2267  then call \fIpcre_copy_substring()\fR or \fIpcre_get_substring()\fR, as  then call \fBpcre_copy_substring()\fP or \fBpcre_get_substring()\fP, as
2268  appropriate.  appropriate. \fBNOTE:\fP If PCRE_DUPNAMES is set and there are duplicate names,
2269    the behaviour may not be what you want (see the next section).
2270  .in 0  .P
2271  Last updated: 09 December 2003  \fBWarning:\fP If the pattern uses the (?| feature to set up multiple
2272  .br  subpatterns with the same number, as described in the
2273  Copyright (c) 1997-2003 University of Cambridge.  .\" HTML <a href="pcrepattern.html#dupsubpatternnumber">
2274    .\" </a>
2275    section on duplicate subpattern numbers
2276    .\"
2277    in the
2278    .\" HREF
2279    \fBpcrepattern\fP
2280    .\"
2281    page, you cannot use names to distinguish the different subpatterns, because
2282    names are not included in the compiled code. The matching process uses only
2283    numbers. For this reason, the use of different names for subpatterns of the
2284    same number causes an error at compile time.
2285    .
2286    .
2287    .SH "DUPLICATE SUBPATTERN NAMES"
2288    .rs
2289    .sp
2290    .B int pcre_get_stringtable_entries(const pcre *\fIcode\fP,
2291    .ti +5n
2292    .B const char *\fIname\fP, char **\fIfirst\fP, char **\fIlast\fP);
2293    .PP
2294    When a pattern is compiled with the PCRE_DUPNAMES option, names for subpatterns
2295    are not required to be unique. (Duplicate names are always allowed for
2296    subpatterns with the same number, created by using the (?| feature. Indeed, if
2297    such subpatterns are named, they are required to use the same names.)
2298    .P
2299    Normally, patterns with duplicate names are such that in any one match, only
2300    one of the named subpatterns participates. An example is shown in the
2301    .\" HREF
2302    \fBpcrepattern\fP
2303    .\"
2304    documentation.
2305    .P
2306    When duplicates are present, \fBpcre_copy_named_substring()\fP and
2307    \fBpcre_get_named_substring()\fP return the first substring corresponding to
2308    the given name that is set. If none are set, PCRE_ERROR_NOSUBSTRING (-7) is
2309    returned; no data is returned. The \fBpcre_get_stringnumber()\fP function
2310    returns one of the numbers that are associated with the name, but it is not
2311    defined which it is.
2312    .P
2313    If you want to get full details of all captured substrings for a given name,
2314    you must use the \fBpcre_get_stringtable_entries()\fP function. The first
2315    argument is the compiled pattern, and the second is the name. The third and
2316    fourth are pointers to variables which are updated by the function. After it
2317    has run, they point to the first and last entries in the name-to-number table
2318    for the given name. The function itself returns the length of each entry, or
2319    PCRE_ERROR_NOSUBSTRING (-7) if there are none. The format of the table is
2320    described above in the section entitled \fIInformation about a pattern\fP
2321    .\" HTML <a href="#infoaboutpattern">
2322    .\" </a>
2323    above.
2324    .\"
2325    Given all the relevant entries for the name, you can extract each of their
2326    numbers, and hence the captured data, if any.
2327    .
2328    .
2329    .SH "FINDING ALL POSSIBLE MATCHES"
2330    .rs
2331    .sp
2332    The traditional matching function uses a similar algorithm to Perl, which stops
2333    when it finds the first match, starting at a given point in the subject. If you
2334    want to find all possible matches, or the longest possible match, consider
2335    using the alternative matching function (see below) instead. If you cannot use
2336    the alternative function, but still need to find all possible matches, you
2337    can kludge it up by making use of the callout facility, which is described in
2338    the
2339    .\" HREF
2340    \fBpcrecallout\fP
2341    .\"
2342    documentation.
2343    .P
2344    What you have to do is to insert a callout right at the end of the pattern.
2345    When your callout function is called, extract and save the current matched
2346    substring. Then return 1, which forces \fBpcre_exec()\fP to backtrack and try
2347    other alternatives. Ultimately, when it runs out of matches, \fBpcre_exec()\fP
2348    will yield PCRE_ERROR_NOMATCH.
2349    .
2350    .
2351    .\" HTML <a name="dfamatch"></a>
2352    .SH "MATCHING A PATTERN: THE ALTERNATIVE FUNCTION"
2353    .rs
2354    .sp
2355    .B int pcre_dfa_exec(const pcre *\fIcode\fP, "const pcre_extra *\fIextra\fP,"
2356    .ti +5n
2357    .B "const char *\fIsubject\fP," int \fIlength\fP, int \fIstartoffset\fP,
2358    .ti +5n
2359    .B int \fIoptions\fP, int *\fIovector\fP, int \fIovecsize\fP,
2360    .ti +5n
2361    .B int *\fIworkspace\fP, int \fIwscount\fP);
2362    .P
2363    The function \fBpcre_dfa_exec()\fP is called to match a subject string against
2364    a compiled pattern, using a matching algorithm that scans the subject string
2365    just once, and does not backtrack. This has different characteristics to the
2366    normal algorithm, and is not compatible with Perl. Some of the features of PCRE
2367    patterns are not supported. Nevertheless, there are times when this kind of
2368    matching can be useful. For a discussion of the two matching algorithms, and a
2369    list of features that \fBpcre_dfa_exec()\fP does not support, see the
2370    .\" HREF
2371    \fBpcrematching\fP
2372    .\"
2373    documentation.
2374    .P
2375    The arguments for the \fBpcre_dfa_exec()\fP function are the same as for
2376    \fBpcre_exec()\fP, plus two extras. The \fIovector\fP argument is used in a
2377    different way, and this is described below. The other common arguments are used
2378    in the same way as for \fBpcre_exec()\fP, so their description is not repeated
2379    here.
2380    .P
2381    The two additional arguments provide workspace for the function. The workspace
2382    vector should contain at least 20 elements. It is used for keeping track of
2383    multiple paths through the pattern tree. More workspace will be needed for
2384    patterns and subjects where there are a lot of potential matches.
2385    .P
2386    Here is an example of a simple call to \fBpcre_dfa_exec()\fP:
2387    .sp
2388      int rc;
2389      int ovector[10];
2390      int wspace[20];
2391      rc = pcre_dfa_exec(
2392        re,             /* result of pcre_compile() */
2393        NULL,           /* we didn't study the pattern */
2394        "some string",  /* the subject string */
2395        11,             /* the length of the subject string */
2396        0,              /* start at offset 0 in the subject */
2397        0,              /* default options */
2398        ovector,        /* vector of integers for substring information */
2399        10,             /* number of elements (NOT size in bytes) */
2400        wspace,         /* working space vector */
2401        20);            /* number of elements (NOT size in bytes) */
2402    .
2403    .SS "Option bits for \fBpcre_dfa_exec()\fP"
2404    .rs
2405    .sp
2406    The unused bits of the \fIoptions\fP argument for \fBpcre_dfa_exec()\fP must be
2407    zero. The only bits that may be set are PCRE_ANCHORED, PCRE_NEWLINE_\fIxxx\fP,
2408    PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY, PCRE_NOTEMPTY_ATSTART,
2409    PCRE_NO_UTF8_CHECK, PCRE_BSR_ANYCRLF, PCRE_BSR_UNICODE, PCRE_NO_START_OPTIMIZE,
2410    PCRE_PARTIAL_HARD, PCRE_PARTIAL_SOFT, PCRE_DFA_SHORTEST, and PCRE_DFA_RESTART.
2411    All but the last four of these are exactly the same as for \fBpcre_exec()\fP,
2412    so their description is not repeated here.
2413    .sp
2414      PCRE_PARTIAL_HARD
2415      PCRE_PARTIAL_SOFT
2416    .sp
2417    These have the same general effect as they do for \fBpcre_exec()\fP, but the
2418    details are slightly different. When PCRE_PARTIAL_HARD is set for
2419    \fBpcre_dfa_exec()\fP, it returns PCRE_ERROR_PARTIAL if the end of the subject
2420    is reached and there is still at least one matching possibility that requires
2421    additional characters. This happens even if some complete matches have also
2422    been found. When PCRE_PARTIAL_SOFT is set, the return code PCRE_ERROR_NOMATCH
2423    is converted into PCRE_ERROR_PARTIAL if the end of the subject is reached,
2424    there have been no complete matches, but there is still at least one matching
2425    possibility. The portion of the string that was inspected when the longest
2426    partial match was found is set as the first matching string in both cases.
2427    There is a more detailed discussion of partial and multi-segment matching, with
2428    examples, in the
2429    .\" HREF
2430    \fBpcrepartial\fP
2431    .\"
2432    documentation.
2433    .sp
2434      PCRE_DFA_SHORTEST
2435    .sp
2436    Setting the PCRE_DFA_SHORTEST option causes the matching algorithm to stop as
2437    soon as it has found one match. Because of the way the alternative algorithm
2438    works, this is necessarily the shortest possible match at the first possible
2439    matching point in the subject string.
2440    .sp
2441      PCRE_DFA_RESTART
2442    .sp
2443    When \fBpcre_dfa_exec()\fP returns a partial match, it is possible to call it
2444    again, with additional subject characters, and have it continue with the same
2445    match. The PCRE_DFA_RESTART option requests this action; when it is set, the
2446    \fIworkspace\fP and \fIwscount\fP options must reference the same vector as
2447    before because data about the match so far is left in them after a partial
2448    match. There is more discussion of this facility in the
2449    .\" HREF
2450    \fBpcrepartial\fP
2451    .\"
2452    documentation.
2453    .
2454    .
2455    .SS "Successful returns from \fBpcre_dfa_exec()\fP"
2456    .rs
2457    .sp
2458    When \fBpcre_dfa_exec()\fP succeeds, it may have matched more than one
2459    substring in the subject. Note, however, that all the matches from one run of
2460    the function start at the same point in the subject. The shorter matches are
2461    all initial substrings of the longer matches. For example, if the pattern
2462    .sp
2463      <.*>
2464    .sp
2465    is matched against the string
2466    .sp
2467      This is <something> <something else> <something further> no more
2468    .sp
2469    the three matched strings are
2470    .sp
2471      <something>
2472      <something> <something else>
2473      <something> <something else> <something further>
2474    .sp
2475    On success, the yield of the function is a number greater than zero, which is
2476    the number of matched substrings. The substrings themselves are returned in
2477    \fIovector\fP. Each string uses two elements; the first is the offset to the
2478    start, and the second is the offset to the end. In fact, all the strings have
2479    the same start offset. (Space could have been saved by giving this only once,
2480    but it was decided to retain some compatibility with the way \fBpcre_exec()\fP
2481    returns data, even though the meaning of the strings is different.)
2482    .P
2483    The strings are returned in reverse order of length; that is, the longest
2484    matching string is given first. If there were too many matches to fit into
2485    \fIovector\fP, the yield of the function is zero, and the vector is filled with
2486    the longest matches. Unlike \fBpcre_exec()\fP, \fBpcre_dfa_exec()\fP can use
2487    the entire \fIovector\fP for returning matched strings.
2488    .
2489    .
2490    .SS "Error returns from \fBpcre_dfa_exec()\fP"
2491    .rs
2492    .sp
2493    The \fBpcre_dfa_exec()\fP function returns a negative number when it fails.
2494    Many of the errors are the same as for \fBpcre_exec()\fP, and these are
2495    described
2496    .\" HTML <a href="#errorlist">
2497    .\" </a>
2498    above.
2499    .\"
2500    There are in addition the following errors that are specific to
2501    \fBpcre_dfa_exec()\fP:
2502    .sp
2503      PCRE_ERROR_DFA_UITEM      (-16)
2504    .sp
2505    This return is given if \fBpcre_dfa_exec()\fP encounters an item in the pattern
2506    that it does not support, for instance, the use of \eC or a back reference.
2507    .sp
2508      PCRE_ERROR_DFA_UCOND      (-17)
2509    .sp
2510    This return is given if \fBpcre_dfa_exec()\fP encounters a condition item that
2511    uses a back reference for the condition, or a test for recursion in a specific
2512    group. These are not supported.
2513    .sp
2514      PCRE_ERROR_DFA_UMLIMIT    (-18)
2515    .sp
2516    This return is given if \fBpcre_dfa_exec()\fP is called with an \fIextra\fP
2517    block that contains a setting of the \fImatch_limit\fP or
2518    \fImatch_limit_recursion\fP fields. This is not supported (these fields are
2519    meaningless for DFA matching).
2520    .sp
2521      PCRE_ERROR_DFA_WSSIZE     (-19)
2522    .sp
2523    This return is given if \fBpcre_dfa_exec()\fP runs out of space in the
2524    \fIworkspace\fP vector.
2525    .sp
2526      PCRE_ERROR_DFA_RECURSE    (-20)
2527    .sp
2528    When a recursive subpattern is processed, the matching function calls itself
2529    recursively, using private vectors for \fIovector\fP and \fIworkspace\fP. This
2530    error is given if the output vector is not large enough. This should be
2531    extremely rare, as a vector of size 1000 is used.
2532    .
2533    .
2534    .SH "SEE ALSO"
2535    .rs
2536    .sp
2537    \fBpcrebuild\fP(3), \fBpcrecallout\fP(3), \fBpcrecpp(3)\fP(3),
2538    \fBpcrematching\fP(3), \fBpcrepartial\fP(3), \fBpcreposix\fP(3),
2539    \fBpcreprecompile\fP(3), \fBpcresample\fP(3), \fBpcrestack\fP(3).
2540    .
2541    .
2542    .SH AUTHOR
2543    .rs
2544    .sp
2545    .nf
2546    Philip Hazel
2547    University Computing Service
2548    Cambridge CB2 3QH, England.
2549    .fi
2550    .
2551    .
2552    .SH REVISION
2553    .rs
2554    .sp
2555    .nf
2556    Last updated: 02 December 2011
2557    Copyright (c) 1997-2011 University of Cambridge.
2558    .fi

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