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revision 182 by ph10, Wed Jun 13 15:09:54 2007 UTC revision 442 by ph10, Fri Sep 11 10:21:02 2009 UTC
# Line 135  Applications can use these to include su Line 135  Applications can use these to include su
135  The functions \fBpcre_compile()\fP, \fBpcre_compile2()\fP, \fBpcre_study()\fP,  The functions \fBpcre_compile()\fP, \fBpcre_compile2()\fP, \fBpcre_study()\fP,
136  and \fBpcre_exec()\fP are used for compiling and matching regular expressions  and \fBpcre_exec()\fP are used for compiling and matching regular expressions
137  in a Perl-compatible manner. A sample program that demonstrates the simplest  in a Perl-compatible manner. A sample program that demonstrates the simplest
138  way of using them is provided in the file called \fIpcredemo.c\fP in the source  way of using them is provided in the file called \fIpcredemo.c\fP in the PCRE
139  distribution. The  source distribution. A listing of this program is given in the
140    .\" HREF
141    \fBpcredemo\fP
142    .\"
143    documentation, and the
144  .\" HREF  .\" HREF
145  \fBpcresample\fP  \fBpcresample\fP
146  .\"  .\"
147  documentation describes how to run it.  documentation describes how to compile and run it.
148  .P  .P
149  A second matching function, \fBpcre_dfa_exec()\fP, which is not  A second matching function, \fBpcre_dfa_exec()\fP, which is not
150  Perl-compatible, is also provided. This uses a different algorithm for the  Perl-compatible, is also provided. This uses a different algorithm for the
151  matching. The alternative algorithm finds all possible matches (at a given  matching. The alternative algorithm finds all possible matches (at a given
152  point in the subject), and scans the subject just once. However, this algorithm  point in the subject), and scans the subject just once (unless there are
153  does not return captured substrings. A description of the two matching  lookbehind assertions). However, this algorithm does not return captured
154  algorithms and their advantages and disadvantages is given in the  substrings. A description of the two matching algorithms and their advantages
155    and disadvantages is given in the
156  .\" HREF  .\" HREF
157  \fBpcrematching\fP  \fBpcrematching\fP
158  .\"  .\"
# Line 218  points during a matching operation. Deta Line 223  points during a matching operation. Deta
223  documentation.  documentation.
224  .  .
225  .  .
226    .\" HTML <a name="newlines"></a>
227  .SH NEWLINES  .SH NEWLINES
228  .rs  .rs
229  .sp  .sp
# Line 235  The default default is LF, which is the Line 241  The default default is LF, which is the
241  default can be overridden, either when a pattern is compiled, or when it is  default can be overridden, either when a pattern is compiled, or when it is
242  matched.  matched.
243  .P  .P
244    At compile time, the newline convention can be specified by the \fIoptions\fP
245    argument of \fBpcre_compile()\fP, or it can be specified by special text at the
246    start of the pattern itself; this overrides any other settings. See the
247    .\" HREF
248    \fBpcrepattern\fP
249    .\"
250    page for details of the special character sequences.
251    .P
252  In the PCRE documentation the word "newline" is used to mean "the character or  In the PCRE documentation the word "newline" is used to mean "the character or
253  pair of characters that indicate a line break". The choice of newline  pair of characters that indicate a line break". The choice of newline
254  convention affects the handling of the dot, circumflex, and dollar  convention affects the handling of the dot, circumflex, and dollar
255  metacharacters, the handling of #-comments in /x mode, and, when CRLF is a  metacharacters, the handling of #-comments in /x mode, and, when CRLF is a
256  recognized line ending sequence, the match position advancement for a  recognized line ending sequence, the match position advancement for a
257  non-anchored pattern. The choice of newline convention does not affect the  non-anchored pattern. There is more detail about this in the
258  interpretation of the \en or \er escape sequences.  .\" HTML <a href="#execoptions">
259    .\" </a>
260    section on \fBpcre_exec()\fP options
261    .\"
262    below.
263    .P
264    The choice of newline convention does not affect the interpretation of
265    the \en or \er escape sequences, nor does it affect what \eR matches, which is
266    controlled in a similar way, but by separate options.
267  .  .
268  .  .
269  .SH MULTITHREADING  .SH MULTITHREADING
# Line 300  properties is available; otherwise it is Line 322  properties is available; otherwise it is
322  .sp  .sp
323  The output is an integer whose value specifies the default character sequence  The output is an integer whose value specifies the default character sequence
324  that is recognized as meaning "newline". The four values that are supported  that is recognized as meaning "newline". The four values that are supported
325  are: 10 for LF, 13 for CR, 3338 for CRLF, -2 for ANYCRLF, and -1 for ANY. The  are: 10 for LF, 13 for CR, 3338 for CRLF, -2 for ANYCRLF, and -1 for ANY.
326  default should normally be the standard sequence for your operating system.  Though they are derived from ASCII, the same values are returned in EBCDIC
327    environments. The default should normally correspond to the standard sequence
328    for your operating system.
329    .sp
330      PCRE_CONFIG_BSR
331    .sp
332    The output is an integer whose value indicates what character sequences the \eR
333    escape sequence matches by default. A value of 0 means that \eR matches any
334    Unicode line ending sequence; a value of 1 means that \eR matches only CR, LF,
335    or CRLF. The default can be overridden when a pattern is compiled or matched.
336  .sp  .sp
337    PCRE_CONFIG_LINK_SIZE    PCRE_CONFIG_LINK_SIZE
338  .sp  .sp
# Line 323  documentation. Line 354  documentation.
354  .sp  .sp
355    PCRE_CONFIG_MATCH_LIMIT    PCRE_CONFIG_MATCH_LIMIT
356  .sp  .sp
357  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
358  internal matching function calls in a \fBpcre_exec()\fP execution. Further  internal matching function calls in a \fBpcre_exec()\fP execution. Further
359  details are given with \fBpcre_exec()\fP below.  details are given with \fBpcre_exec()\fP below.
360  .sp  .sp
361    PCRE_CONFIG_MATCH_LIMIT_RECURSION    PCRE_CONFIG_MATCH_LIMIT_RECURSION
362  .sp  .sp
363  The output is an integer that gives the default limit for the depth of  The output is a long integer that gives the default limit for the depth of
364  recursion when calling the internal matching function in a \fBpcre_exec()\fP  recursion when calling the internal matching function in a \fBpcre_exec()\fP
365  execution. Further details are given with \fBpcre_exec()\fP below.  execution. Further details are given with \fBpcre_exec()\fP below.
366  .sp  .sp
# Line 380  argument, which is an address (see below Line 411  argument, which is an address (see below
411  .P  .P
412  The \fIoptions\fP argument contains various bit settings that affect the  The \fIoptions\fP argument contains various bit settings that affect the
413  compilation. It should be zero if no options are required. The available  compilation. It should be zero if no options are required. The available
414  options are described below. Some of them, in particular, those that are  options are described below. Some of them (in particular, those that are
415  compatible with Perl, can also be set and unset from within the pattern (see  compatible with Perl, but also some others) can also be set and unset from
416  the detailed description in the  within the pattern (see the detailed description in the
417  .\" HREF  .\" HREF
418  \fBpcrepattern\fP  \fBpcrepattern\fP
419  .\"  .\"
420  documentation). For these options, the contents of the \fIoptions\fP argument  documentation). For those options that can be different in different parts of
421  specifies their initial settings at the start of compilation and execution. The  the pattern, the contents of the \fIoptions\fP argument specifies their initial
422  PCRE_ANCHORED and PCRE_NEWLINE_\fIxxx\fP options can be set at the time of  settings at the start of compilation and execution. The PCRE_ANCHORED and
423  matching as well as at compile time.  PCRE_NEWLINE_\fIxxx\fP options can be set at the time of matching as well as at
424    compile time.
425  .P  .P
426  If \fIerrptr\fP is NULL, \fBpcre_compile()\fP returns NULL immediately.  If \fIerrptr\fP is NULL, \fBpcre_compile()\fP returns NULL immediately.
427  Otherwise, if compilation of a pattern fails, \fBpcre_compile()\fP returns  Otherwise, if compilation of a pattern fails, \fBpcre_compile()\fP returns
# Line 444  facility, see the Line 476  facility, see the
476  .\"  .\"
477  documentation.  documentation.
478  .sp  .sp
479      PCRE_BSR_ANYCRLF
480      PCRE_BSR_UNICODE
481    .sp
482    These options (which are mutually exclusive) control what the \eR escape
483    sequence matches. The choice is either to match only CR, LF, or CRLF, or to
484    match any Unicode newline sequence. The default is specified when PCRE is
485    built. It can be overridden from within the pattern, or by setting an option
486    when a compiled pattern is matched.
487    .sp
488    PCRE_CASELESS    PCRE_CASELESS
489  .sp  .sp
490  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
# Line 516  If this option is set, an unanchored pat Line 557  If this option is set, an unanchored pat
557  the first newline in the subject string, though the matched text may continue  the first newline in the subject string, though the matched text may continue
558  over the newline.  over the newline.
559  .sp  .sp
560      PCRE_JAVASCRIPT_COMPAT
561    .sp
562    If this option is set, PCRE's behaviour is changed in some ways so that it is
563    compatible with JavaScript rather than Perl. The changes are as follows:
564    .P
565    (1) A lone closing square bracket in a pattern causes a compile-time error,
566    because this is illegal in JavaScript (by default it is treated as a data
567    character). Thus, the pattern AB]CD becomes illegal when this option is set.
568    .P
569    (2) At run time, a back reference to an unset subpattern group matches an empty
570    string (by default this causes the current matching alternative to fail). A
571    pattern such as (\e1)(a) succeeds when this option is set (assuming it can find
572    an "a" in the subject), whereas it fails by default, for Perl compatibility.
573    .sp
574    PCRE_MULTILINE    PCRE_MULTILINE
575  .sp  .sp
576  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
# Line 601  page. Line 656  page.
656    PCRE_NO_UTF8_CHECK    PCRE_NO_UTF8_CHECK
657  .sp  .sp
658  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
659  automatically checked. If an invalid UTF-8 sequence of bytes is found,  automatically checked. There is a discussion about the
660  \fBpcre_compile()\fP returns an error. If you already know that your pattern is  .\" HTML <a href="pcre.html#utf8strings">
661  valid, and you want to skip this check for performance reasons, you can set the  .\" </a>
662  PCRE_NO_UTF8_CHECK option. When it is set, the effect of passing an invalid  validity of UTF-8 strings
663  UTF-8 string as a pattern is undefined. It may cause your program to crash.  .\"
664  Note that this option can also be passed to \fBpcre_exec()\fP and  in the main
665  \fBpcre_dfa_exec()\fP, to suppress the UTF-8 validity checking of subject  .\" HREF
666  strings.  \fBpcre\fP
667    .\"
668    page. If an invalid UTF-8 sequence of bytes is found, \fBpcre_compile()\fP
669    returns an error. If you already know that your pattern is valid, and you want
670    to skip this check for performance reasons, you can set the PCRE_NO_UTF8_CHECK
671    option. When it is set, the effect of passing an invalid UTF-8 string as a
672    pattern is undefined. It may cause your program to crash. Note that this option
673    can also be passed to \fBpcre_exec()\fP and \fBpcre_dfa_exec()\fP, to suppress
674    the UTF-8 validity checking of subject strings.
675  .  .
676  .  .
677  .SH "COMPILATION ERROR CODES"  .SH "COMPILATION ERROR CODES"
# Line 631  out of use. To avoid confusion, they hav Line 694  out of use. To avoid confusion, they hav
694     9  nothing to repeat     9  nothing to repeat
695    10  [this code is not in use]    10  [this code is not in use]
696    11  internal error: unexpected repeat    11  internal error: unexpected repeat
697    12  unrecognized character after (?    12  unrecognized character after (? or (?-
698    13  POSIX named classes are supported only within a class    13  POSIX named classes are supported only within a class
699    14  missing )    14  missing )
700    15  reference to non-existent subpattern    15  reference to non-existent subpattern
# Line 639  out of use. To avoid confusion, they hav Line 702  out of use. To avoid confusion, they hav
702    17  unknown option bit(s) set    17  unknown option bit(s) set
703    18  missing ) after comment    18  missing ) after comment
704    19  [this code is not in use]    19  [this code is not in use]
705    20  regular expression too large    20  regular expression is too large
706    21  failed to get memory    21  failed to get memory
707    22  unmatched parentheses    22  unmatched parentheses
708    23  internal error: code overflow    23  internal error: code overflow
# Line 668  out of use. To avoid confusion, they hav Line 731  out of use. To avoid confusion, they hav
731    46  malformed \eP or \ep sequence    46  malformed \eP or \ep sequence
732    47  unknown property name after \eP or \ep    47  unknown property name after \eP or \ep
733    48  subpattern name is too long (maximum 32 characters)    48  subpattern name is too long (maximum 32 characters)
734    49  too many named subpatterns (maximum 10,000)    49  too many named subpatterns (maximum 10000)
735    50  repeated subpattern is too long    50  [this code is not in use]
736    51  octal value is greater than \e377 (not in UTF-8 mode)    51  octal value is greater than \e377 (not in UTF-8 mode)
737    52  internal error: overran compiling workspace    52  internal error: overran compiling workspace
738    53  internal error: previously-checked referenced subpattern not found    53  internal error: previously-checked referenced subpattern not found
739    54  DEFINE group contains more than one branch    54  DEFINE group contains more than one branch
740    55  repeating a DEFINE group is not allowed    55  repeating a DEFINE group is not allowed
741    56  inconsistent NEWLINE options"    56  inconsistent NEWLINE options
742    57  \eg is not followed by a braced name or an optionally braced    57  \eg is not followed by a braced, angle-bracketed, or quoted
743          non-zero number          name/number or by a plain number
744    58  (?+ or (?- or (?(+ or (?(- must be followed by a non-zero number    58  a numbered reference must not be zero
745      59  (*VERB) with an argument is not supported
746      60  (*VERB) not recognized
747      61  number is too big
748      62  subpattern name expected
749      63  digit expected after (?+
750      64  ] is an invalid data character in JavaScript compatibility mode
751    .sp
752    The numbers 32 and 10000 in errors 48 and 49 are defaults; different values may
753    be used if the limits were changed when PCRE was built.
754  .  .
755  .  .
756  .SH "STUDYING A PATTERN"  .SH "STUDYING A PATTERN"
# Line 874  table indicating a fixed set of bytes fo Line 946  table indicating a fixed set of bytes fo
946  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
947  fourth argument should point to an \fBunsigned char *\fP variable.  fourth argument should point to an \fBunsigned char *\fP variable.
948  .sp  .sp
949      PCRE_INFO_HASCRORLF
950    .sp
951    Return 1 if the pattern contains any explicit matches for CR or LF characters,
952    otherwise 0. The fourth argument should point to an \fBint\fP variable. An
953    explicit match is either a literal CR or LF character, or \er or \en.
954    .sp
955    PCRE_INFO_JCHANGED    PCRE_INFO_JCHANGED
956  .sp  .sp
957  Return 1 if the (?J) option setting is used in the pattern, otherwise 0. The  Return 1 if the (?J) or (?-J) option setting is used in the pattern, otherwise
958  fourth argument should point to an \fBint\fP variable. The (?J) internal option  0. The fourth argument should point to an \fBint\fP variable. (?J) and
959  setting changes the local PCRE_DUPNAMES option.  (?-J) set and unset the local PCRE_DUPNAMES option, respectively.
960  .sp  .sp
961    PCRE_INFO_LASTLITERAL    PCRE_INFO_LASTLITERAL
962  .sp  .sp
# Line 934  different for each compiled pattern. Line 1012  different for each compiled pattern.
1012  .sp  .sp
1013    PCRE_INFO_OKPARTIAL    PCRE_INFO_OKPARTIAL
1014  .sp  .sp
1015  Return 1 if the pattern can be used for partial matching, otherwise 0. The  Return 1 if the pattern can be used for partial matching with
1016  fourth argument should point to an \fBint\fP variable. The  \fBpcre_exec()\fP, otherwise 0. The fourth argument should point to an
1017    \fBint\fP variable. From release 8.00, this always returns 1, because the
1018    restrictions that previously applied to partial matching have been lifted. The
1019  .\" HREF  .\" HREF
1020  \fBpcrepartial\fP  \fBpcrepartial\fP
1021  .\"  .\"
1022  documentation lists the restrictions that apply to patterns when partial  documentation gives details of partial matching.
 matching is used.  
1023  .sp  .sp
1024    PCRE_INFO_OPTIONS    PCRE_INFO_OPTIONS
1025  .sp  .sp
1026  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
1027  argument should point to an \fBunsigned long int\fP variable. These option bits  argument should point to an \fBunsigned long int\fP variable. These option bits
1028  are those specified in the call to \fBpcre_compile()\fP, modified by any  are those specified in the call to \fBpcre_compile()\fP, modified by any
1029  top-level option settings within the pattern itself.  top-level option settings at the start of the pattern itself. In other words,
1030    they are the options that will be in force when matching starts. For example,
1031    if the pattern /(?im)abc(?-i)d/ is compiled with the PCRE_EXTENDED option, the
1032    result is PCRE_CASELESS, PCRE_MULTILINE, and PCRE_EXTENDED.
1033  .P  .P
1034  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
1035  alternatives begin with one of the following:  alternatives begin with one of the following:
# Line 1137  with a \fBpcre_extra\fP block in which \ Line 1219  with a \fBpcre_extra\fP block in which \
1219  PCRE_EXTRA_MATCH_LIMIT_RECURSION is set in the \fIflags\fP field. If the limit  PCRE_EXTRA_MATCH_LIMIT_RECURSION is set in the \fIflags\fP field. If the limit
1220  is exceeded, \fBpcre_exec()\fP returns PCRE_ERROR_RECURSIONLIMIT.  is exceeded, \fBpcre_exec()\fP returns PCRE_ERROR_RECURSIONLIMIT.
1221  .P  .P
1222  The \fIpcre_callout\fP field is used in conjunction with the "callout" feature,  The \fIcallout_data\fP field is used in conjunction with the "callout" feature,
1223  which is described in the  and is described in the
1224  .\" HREF  .\" HREF
1225  \fBpcrecallout\fP  \fBpcrecallout\fP
1226  .\"  .\"
# Line 1158  called. See the Line 1240  called. See the
1240  .\"  .\"
1241  documentation for a discussion of saving compiled patterns for later use.  documentation for a discussion of saving compiled patterns for later use.
1242  .  .
1243    .\" HTML <a name="execoptions"></a>
1244  .SS "Option bits for \fBpcre_exec()\fP"  .SS "Option bits for \fBpcre_exec()\fP"
1245  .rs  .rs
1246  .sp  .sp
1247  The unused bits of the \fIoptions\fP argument for \fBpcre_exec()\fP must be  The unused bits of the \fIoptions\fP argument for \fBpcre_exec()\fP must be
1248  zero. The only bits that may be set are PCRE_ANCHORED, PCRE_NEWLINE_\fIxxx\fP,  zero. The only bits that may be set are PCRE_ANCHORED, PCRE_NEWLINE_\fIxxx\fP,
1249  PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY, PCRE_NO_UTF8_CHECK and PCRE_PARTIAL.  PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY, PCRE_NOTEMPTY_ATSTART,
1250    PCRE_NO_START_OPTIMIZE, PCRE_NO_UTF8_CHECK, PCRE_PARTIAL_SOFT, and
1251    PCRE_PARTIAL_HARD.
1252  .sp  .sp
1253    PCRE_ANCHORED    PCRE_ANCHORED
1254  .sp  .sp
# Line 1172  matching position. If a pattern was comp Line 1257  matching position. If a pattern was comp
1257  to be anchored by virtue of its contents, it cannot be made unachored at  to be anchored by virtue of its contents, it cannot be made unachored at
1258  matching time.  matching time.
1259  .sp  .sp
1260      PCRE_BSR_ANYCRLF
1261      PCRE_BSR_UNICODE
1262    .sp
1263    These options (which are mutually exclusive) control what the \eR escape
1264    sequence matches. The choice is either to match only CR, LF, or CRLF, or to
1265    match any Unicode newline sequence. These options override the choice that was
1266    made or defaulted when the pattern was compiled.
1267    .sp
1268    PCRE_NEWLINE_CR    PCRE_NEWLINE_CR
1269    PCRE_NEWLINE_LF    PCRE_NEWLINE_LF
1270    PCRE_NEWLINE_CRLF    PCRE_NEWLINE_CRLF
# Line 1183  the pattern was compiled. For details, s Line 1276  the pattern was compiled. For details, s
1276  \fBpcre_compile()\fP above. During matching, the newline choice affects the  \fBpcre_compile()\fP above. During matching, the newline choice affects the
1277  behaviour of the dot, circumflex, and dollar metacharacters. It may also alter  behaviour of the dot, circumflex, and dollar metacharacters. It may also alter
1278  the way the match position is advanced after a match failure for an unanchored  the way the match position is advanced after a match failure for an unanchored
1279  pattern. When PCRE_NEWLINE_CRLF, PCRE_NEWLINE_ANYCRLF, or PCRE_NEWLINE_ANY is  pattern.
1280  set, and a match attempt fails when the current position is at a CRLF sequence,  .P
1281  the match position is advanced by two characters instead of one, in other  When PCRE_NEWLINE_CRLF, PCRE_NEWLINE_ANYCRLF, or PCRE_NEWLINE_ANY is set, and a
1282  words, to after the CRLF.  match attempt for an unanchored pattern fails when the current position is at a
1283    CRLF sequence, and the pattern contains no explicit matches for CR or LF
1284    characters, the match position is advanced by two characters instead of one, in
1285    other words, to after the CRLF.
1286    .P
1287    The above rule is a compromise that makes the most common cases work as
1288    expected. For example, if the pattern is .+A (and the PCRE_DOTALL option is not
1289    set), it does not match the string "\er\enA" because, after failing at the
1290    start, it skips both the CR and the LF before retrying. However, the pattern
1291    [\er\en]A does match that string, because it contains an explicit CR or LF
1292    reference, and so advances only by one character after the first failure.
1293    .P
1294    An explicit match for CR of LF is either a literal appearance of one of those
1295    characters, or one of the \er or \en escape sequences. Implicit matches such as
1296    [^X] do not count, nor does \es (which includes CR and LF in the characters
1297    that it matches).
1298    .P
1299    Notwithstanding the above, anomalous effects may still occur when CRLF is a
1300    valid newline sequence and explicit \er or \en escapes appear in the pattern.
1301  .sp  .sp
1302    PCRE_NOTBOL    PCRE_NOTBOL
1303  .sp  .sp
# Line 1212  match the empty string, the entire match Line 1323  match the empty string, the entire match
1323  .sp  .sp
1324    a?b?    a?b?
1325  .sp  .sp
1326  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
1327  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
1328  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".
1329  .P  .sp
1330  Perl has no direct equivalent of PCRE_NOTEMPTY, but it does make a special case    PCRE_NOTEMPTY_ATSTART
1331  of a pattern match of the empty string within its \fBsplit()\fP function, and  .sp
1332  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
1333  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
1334  PCRE_NOTEMPTY and PCRE_ANCHORED, and then if that fails by advancing the  can occur only if the pattern contains \eK.
1335  starting offset (see below) and trying an ordinary match again. There is some  .P
1336  code that demonstrates how to do this in the \fIpcredemo.c\fP sample program.  Perl has no direct equivalent of PCRE_NOTEMPTY or PCRE_NOTEMPTY_ATSTART, but it
1337    does make a special case of a pattern match of the empty string within its
1338    \fBsplit()\fP function, and when using the /g modifier. It is possible to
1339    emulate Perl's behaviour after matching a null string by first trying the match
1340    again at the same offset with PCRE_NOTEMPTY_ATSTART and PCRE_ANCHORED, and then
1341    if that fails, by advancing the starting offset (see below) and trying an
1342    ordinary match again. There is some code that demonstrates how to do this in
1343    the
1344    .\" HREF
1345    \fBpcredemo\fP
1346    .\"
1347    sample program.
1348    .sp
1349      PCRE_NO_START_OPTIMIZE
1350    .sp
1351    There are a number of optimizations that \fBpcre_exec()\fP uses at the start of
1352    a match, in order to speed up the process. For example, if it is known that a
1353    match must start with a specific character, it searches the subject for that
1354    character, and fails immediately if it cannot find it, without actually running
1355    the main matching function. When callouts are in use, these optimizations can
1356    cause them to be skipped. This option disables the "start-up" optimizations,
1357    causing performance to suffer, but ensuring that the callouts do occur.
1358  .sp  .sp
1359    PCRE_NO_UTF8_CHECK    PCRE_NO_UTF8_CHECK
1360  .sp  .sp
1361  When PCRE_UTF8 is set at compile time, the validity of the subject as a UTF-8  When PCRE_UTF8 is set at compile time, the validity of the subject as a UTF-8
1362  string is automatically checked when \fBpcre_exec()\fP is subsequently called.  string is automatically checked when \fBpcre_exec()\fP is subsequently called.
1363  The value of \fIstartoffset\fP is also checked to ensure that it points to the  The value of \fIstartoffset\fP is also checked to ensure that it points to the
1364  start of a UTF-8 character. If an invalid UTF-8 sequence of bytes is found,  start of a UTF-8 character. There is a discussion about the validity of UTF-8
1365  \fBpcre_exec()\fP returns the error PCRE_ERROR_BADUTF8. If \fIstartoffset\fP  strings in the
1366  contains an invalid value, PCRE_ERROR_BADUTF8_OFFSET is returned.  .\" HTML <a href="pcre.html#utf8strings">
1367    .\" </a>
1368    section on UTF-8 support
1369    .\"
1370    in the main
1371    .\" HREF
1372    \fBpcre\fP
1373    .\"
1374    page. If an invalid UTF-8 sequence of bytes is found, \fBpcre_exec()\fP returns
1375    the error PCRE_ERROR_BADUTF8. If \fIstartoffset\fP contains an invalid value,
1376    PCRE_ERROR_BADUTF8_OFFSET is returned.
1377  .P  .P
1378  If you already know that your subject is valid, and you want to skip these  If you already know that your subject is valid, and you want to skip these
1379  checks for performance reasons, you can set the PCRE_NO_UTF8_CHECK option when  checks for performance reasons, you can set the PCRE_NO_UTF8_CHECK option when
# Line 1243  PCRE_NO_UTF8_CHECK is set, the effect of Line 1385  PCRE_NO_UTF8_CHECK is set, the effect of
1385  subject, or a value of \fIstartoffset\fP that does not point to the start of a  subject, or a value of \fIstartoffset\fP that does not point to the start of a
1386  UTF-8 character, is undefined. Your program may crash.  UTF-8 character, is undefined. Your program may crash.
1387  .sp  .sp
1388    PCRE_PARTIAL    PCRE_PARTIAL_HARD
1389      PCRE_PARTIAL_SOFT
1390  .sp  .sp
1391  This option turns on the partial matching feature. If the subject string fails  These options turn on the partial matching feature. For backwards
1392  to match the pattern, but at some point during the matching process the end of  compatibility, PCRE_PARTIAL is a synonym for PCRE_PARTIAL_SOFT. A partial match
1393  the subject was reached (that is, the subject partially matches the pattern and  occurs if the end of the subject string is reached successfully, but there are
1394  the failure to match occurred only because there were not enough subject  not enough subject characters to complete the match. If this happens when
1395  characters), \fBpcre_exec()\fP returns PCRE_ERROR_PARTIAL instead of  PCRE_PARTIAL_HARD is set, \fBpcre_exec()\fP immediately returns
1396  PCRE_ERROR_NOMATCH. When PCRE_PARTIAL is used, there are restrictions on what  PCRE_ERROR_PARTIAL. Otherwise, if PCRE_PARTIAL_SOFT is set, matching continues
1397  may appear in the pattern. These are discussed in the  by testing any other alternatives. Only if they all fail is PCRE_ERROR_PARTIAL
1398    returned (instead of PCRE_ERROR_NOMATCH). The portion of the string that
1399    was inspected when the partial match was found is set as the first matching
1400    string. There is a more detailed discussion in the
1401  .\" HREF  .\" HREF
1402  \fBpcrepartial\fP  \fBpcrepartial\fP
1403  .\"  .\"
# Line 1261  documentation. Line 1407  documentation.
1407  .rs  .rs
1408  .sp  .sp
1409  The subject string is passed to \fBpcre_exec()\fP as a pointer in  The subject string is passed to \fBpcre_exec()\fP as a pointer in
1410  \fIsubject\fP, a length in \fIlength\fP, and a starting byte offset in  \fIsubject\fP, a length (in bytes) in \fIlength\fP, and a starting byte offset
1411  \fIstartoffset\fP. In UTF-8 mode, the byte offset must point to the start of a  in \fIstartoffset\fP. In UTF-8 mode, the byte offset must point to the start of
1412  UTF-8 character. Unlike the pattern string, the subject may contain binary zero  a UTF-8 character. Unlike the pattern string, the subject may contain binary
1413  bytes. When the starting offset is zero, the search for a match starts at the  zero bytes. When the starting offset is zero, the search for a match starts at
1414  beginning of the subject, and this is by far the most common case.  the beginning of the subject, and this is by far the most common case.
1415  .P  .P
1416  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
1417  same subject by calling \fBpcre_exec()\fP again after a previous success.  same subject by calling \fBpcre_exec()\fP again after a previous success.
# Line 1299  pattern. Following the usage in Jeffrey Line 1445  pattern. Following the usage in Jeffrey
1445  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
1446  kinds of parenthesized subpattern that do not cause substrings to be captured.  kinds of parenthesized subpattern that do not cause substrings to be captured.
1447  .P  .P
1448  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
1449  whose address is passed in \fIovector\fP. The number of elements in the vector  address is passed in \fIovector\fP. The number of elements in the vector is
1450  is passed in \fIovecsize\fP, which must be a non-negative number. \fBNote\fP:  passed in \fIovecsize\fP, which must be a non-negative number. \fBNote\fP: this
1451  this argument is NOT the size of \fIovector\fP in bytes.  argument is NOT the size of \fIovector\fP in bytes.
1452  .P  .P
1453  The first two-thirds of the vector is used to pass back captured substrings,  The first two-thirds of the vector is used to pass back captured substrings,
1454  each substring using a pair of integers. The remaining third of the vector is  each substring using a pair of integers. The remaining third of the vector is
1455  used as workspace by \fBpcre_exec()\fP while matching capturing subpatterns,  used as workspace by \fBpcre_exec()\fP while matching capturing subpatterns,
1456  and is not available for passing back information. The length passed in  and is not available for passing back information. The number passed in
1457  \fIovecsize\fP should always be a multiple of three. If it is not, it is  \fIovecsize\fP should always be a multiple of three. If it is not, it is
1458  rounded down.  rounded down.
1459  .P  .P
1460  When a match is successful, information about captured substrings is returned  When a match is successful, information about captured substrings is returned
1461  in pairs of integers, starting at the beginning of \fIovector\fP, and  in pairs of integers, starting at the beginning of \fIovector\fP, and
1462  continuing up to two-thirds of its length at the most. The first element of a  continuing up to two-thirds of its length at the most. The first element of
1463  pair is set to the offset of the first character in a substring, and the second  each pair is set to the byte offset of the first character in a substring, and
1464  is set to the offset of the first character after the end of a substring. The  the second is set to the byte offset of the first character after the end of a
1465  first pair, \fIovector[0]\fP and \fIovector[1]\fP, identify the portion of the  substring. \fBNote\fP: these values are always byte offsets, even in UTF-8
1466  subject string matched by the entire pattern. The next pair is used for the  mode. They are not character counts.
1467  first capturing subpattern, and so on. The value returned by \fBpcre_exec()\fP  .P
1468  is one more than the highest numbered pair that has been set. For example, if  The first pair of integers, \fIovector[0]\fP and \fIovector[1]\fP, identify the
1469  two substrings have been captured, the returned value is 3. If there are no  portion of the subject string matched by the entire pattern. The next pair is
1470  capturing subpatterns, the return value from a successful match is 1,  used for the first capturing subpattern, and so on. The value returned by
1471  indicating that just the first pair of offsets has been set.  \fBpcre_exec()\fP is one more than the highest numbered pair that has been set.
1472    For example, if two substrings have been captured, the returned value is 3. If
1473    there are no capturing subpatterns, the return value from a successful match is
1474    1, indicating that just the first pair of offsets has been set.
1475  .P  .P
1476  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
1477  string that it matched that is returned.  string that it matched that is returned.
1478  .P  .P
1479  If the vector is too small to hold all the captured substring offsets, it is  If the vector is too small to hold all the captured substring offsets, it is
1480  used as far as possible (up to two-thirds of its length), and the function  used as far as possible (up to two-thirds of its length), and the function
1481  returns a value of zero. In particular, if the substring offsets are not of  returns a value of zero. If the substring offsets are not of interest,
1482  interest, \fBpcre_exec()\fP may be called with \fIovector\fP passed as NULL and  \fBpcre_exec()\fP may be called with \fIovector\fP passed as NULL and
1483  \fIovecsize\fP as zero. However, if the pattern contains back references and  \fIovecsize\fP as zero. However, if the pattern contains back references and
1484  the \fIovector\fP is not big enough to remember the related substrings, PCRE  the \fIovector\fP is not big enough to remember the related substrings, PCRE
1485  has to get additional memory for use during matching. Thus it is usually  has to get additional memory for use during matching. Thus it is usually
# Line 1441  documentation for details of partial mat Line 1590  documentation for details of partial mat
1590  .sp  .sp
1591    PCRE_ERROR_BADPARTIAL     (-13)    PCRE_ERROR_BADPARTIAL     (-13)
1592  .sp  .sp
1593  The PCRE_PARTIAL option was used with a compiled pattern containing items that  This code is no longer in use. It was formerly returned when the PCRE_PARTIAL
1594  are not supported for partial matching. See the  option was used with a compiled pattern containing items that were not
1595  .\" HREF  supported for partial matching. From release 8.00 onwards, there are no
1596  \fBpcrepartial\fP  restrictions on partial matching.
 .\"  
 documentation for details of partial matching.  
1597  .sp  .sp
1598    PCRE_ERROR_INTERNAL       (-14)    PCRE_ERROR_INTERNAL       (-14)
1599  .sp  .sp
# Line 1463  The internal recursion limit, as specifi Line 1610  The internal recursion limit, as specifi
1610  field in a \fBpcre_extra\fP structure (or defaulted) was reached. See the  field in a \fBpcre_extra\fP structure (or defaulted) was reached. See the
1611  description above.  description above.
1612  .sp  .sp
   PCRE_ERROR_NULLWSLIMIT    (-22)  
 .sp  
 When a group that can match an empty substring is repeated with an unbounded  
 upper limit, the subject position at the start of the group must be remembered,  
 so that a test for an empty string can be made when the end of the group is  
 reached. Some workspace is required for this; if it runs out, this error is  
 given.  
 .sp  
1613    PCRE_ERROR_BADNEWLINE     (-23)    PCRE_ERROR_BADNEWLINE     (-23)
1614  .sp  .sp
1615  An invalid combination of PCRE_NEWLINE_\fIxxx\fP options was given.  An invalid combination of PCRE_NEWLINE_\fIxxx\fP options was given.
1616  .P  .P
1617  Error numbers -16 to -20 are not used by \fBpcre_exec()\fP.  Error numbers -16 to -20 and -22 are not used by \fBpcre_exec()\fP.
1618  .  .
1619  .  .
1620  .SH "EXTRACTING CAPTURED SUBSTRINGS BY NUMBER"  .SH "EXTRACTING CAPTURED SUBSTRINGS BY NUMBER"
# Line 1624  These functions call \fBpcre_get_stringn Line 1763  These functions call \fBpcre_get_stringn
1763  then call \fBpcre_copy_substring()\fP or \fBpcre_get_substring()\fP, as  then call \fBpcre_copy_substring()\fP or \fBpcre_get_substring()\fP, as
1764  appropriate. \fBNOTE:\fP If PCRE_DUPNAMES is set and there are duplicate names,  appropriate. \fBNOTE:\fP If PCRE_DUPNAMES is set and there are duplicate names,
1765  the behaviour may not be what you want (see the next section).  the behaviour may not be what you want (see the next section).
1766  .  .P
1767    \fBWarning:\fP If the pattern uses the "(?|" feature to set up multiple
1768    subpatterns with the same number, you cannot use names to distinguish them,
1769    because names are not included in the compiled code. The matching process uses
1770    only numbers.
1771  .  .
1772  .SH "DUPLICATE SUBPATTERN NAMES"  .SH "DUPLICATE SUBPATTERN NAMES"
1773  .rs  .rs
# Line 1640  example is shown in the Line 1783  example is shown in the
1783  .\" HREF  .\" HREF
1784  \fBpcrepattern\fP  \fBpcrepattern\fP
1785  .\"  .\"
1786  documentation. When duplicates are present, \fBpcre_copy_named_substring()\fP  documentation.
1787  and \fBpcre_get_named_substring()\fP return the first substring corresponding  .P
1788  to the given name that is set. If none are set, an empty string is returned.  When duplicates are present, \fBpcre_copy_named_substring()\fP and
1789  The \fBpcre_get_stringnumber()\fP function returns one of the numbers that are  \fBpcre_get_named_substring()\fP return the first substring corresponding to
1790  associated with the name, but it is not defined which it is.  the given name that is set. If none are set, PCRE_ERROR_NOSUBSTRING (-7) is
1791  .sp  returned; no data is returned. The \fBpcre_get_stringnumber()\fP function
1792    returns one of the numbers that are associated with the name, but it is not
1793    defined which it is.
1794    .P
1795  If you want to get full details of all captured substrings for a given name,  If you want to get full details of all captured substrings for a given name,
1796  you must use the \fBpcre_get_stringtable_entries()\fP function. The first  you must use the \fBpcre_get_stringtable_entries()\fP function. The first
1797  argument is the compiled pattern, and the second is the name. The third and  argument is the compiled pattern, and the second is the name. The third and
# Line 1697  a compiled pattern, using a matching alg Line 1843  a compiled pattern, using a matching alg
1843  just once, and does not backtrack. This has different characteristics to the  just once, and does not backtrack. This has different characteristics to the
1844  normal algorithm, and is not compatible with Perl. Some of the features of PCRE  normal algorithm, and is not compatible with Perl. Some of the features of PCRE
1845  patterns are not supported. Nevertheless, there are times when this kind of  patterns are not supported. Nevertheless, there are times when this kind of
1846  matching can be useful. For a discussion of the two matching algorithms, see  matching can be useful. For a discussion of the two matching algorithms, and a
1847  the  list of features that \fBpcre_dfa_exec()\fP does not support, see the
1848  .\" HREF  .\" HREF
1849  \fBpcrematching\fP  \fBpcrematching\fP
1850  .\"  .\"
# Line 1737  Here is an example of a simple call to \ Line 1883  Here is an example of a simple call to \
1883  .sp  .sp
1884  The unused bits of the \fIoptions\fP argument for \fBpcre_dfa_exec()\fP must be  The unused bits of the \fIoptions\fP argument for \fBpcre_dfa_exec()\fP must be
1885  zero. The only bits that may be set are PCRE_ANCHORED, PCRE_NEWLINE_\fIxxx\fP,  zero. The only bits that may be set are PCRE_ANCHORED, PCRE_NEWLINE_\fIxxx\fP,
1886  PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY, PCRE_NO_UTF8_CHECK, PCRE_PARTIAL,  PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY, PCRE_NOTEMPTY_ATSTART,
1887  PCRE_DFA_SHORTEST, and PCRE_DFA_RESTART. All but the last three of these are  PCRE_NO_UTF8_CHECK, PCRE_PARTIAL_HARD, PCRE_PARTIAL_SOFT, PCRE_DFA_SHORTEST,
1888  the same as for \fBpcre_exec()\fP, so their description is not repeated here.  and PCRE_DFA_RESTART. All but the last four of these are exactly the same as
1889  .sp  for \fBpcre_exec()\fP, so their description is not repeated here.
1890    PCRE_PARTIAL  .sp
1891  .sp    PCRE_PARTIAL_HARD
1892  This has the same general effect as it does for \fBpcre_exec()\fP, but the    PCRE_PARTIAL_SOFT
1893  details are slightly different. When PCRE_PARTIAL is set for  .sp
1894  \fBpcre_dfa_exec()\fP, the return code PCRE_ERROR_NOMATCH is converted into  These have the same general effect as they do for \fBpcre_exec()\fP, but the
1895  PCRE_ERROR_PARTIAL if the end of the subject is reached, there have been no  details are slightly different. When PCRE_PARTIAL_HARD is set for
1896  complete matches, but there is still at least one matching possibility. The  \fBpcre_dfa_exec()\fP, it returns PCRE_ERROR_PARTIAL if the end of the subject
1897  portion of the string that provided the partial match is set as the first  is reached and there is still at least one matching possibility that requires
1898  matching string.  additional characters. This happens even if some complete matches have also
1899    been found. When PCRE_PARTIAL_SOFT is set, the return code PCRE_ERROR_NOMATCH
1900    is converted into PCRE_ERROR_PARTIAL if the end of the subject is reached,
1901    there have been no complete matches, but there is still at least one matching
1902    possibility. The portion of the string that was inspected when the longest
1903    partial match was found is set as the first matching string in both cases.
1904  .sp  .sp
1905    PCRE_DFA_SHORTEST    PCRE_DFA_SHORTEST
1906  .sp  .sp
# Line 1760  matching point in the subject string. Line 1911  matching point in the subject string.
1911  .sp  .sp
1912    PCRE_DFA_RESTART    PCRE_DFA_RESTART
1913  .sp  .sp
1914  When \fBpcre_dfa_exec()\fP is called with the PCRE_PARTIAL option, and returns  When \fBpcre_dfa_exec()\fP returns a partial match, it is possible to call it
1915  a partial match, it is possible to call it again, with additional subject  again, with additional subject characters, and have it continue with the same
1916  characters, and have it continue with the same match. The PCRE_DFA_RESTART  match. The PCRE_DFA_RESTART option requests this action; when it is set, the
1917  option requests this action; when it is set, the \fIworkspace\fP and  \fIworkspace\fP and \fIwscount\fP options must reference the same vector as
1918  \fIwscount\fP options must reference the same vector as before because data  before because data about the match so far is left in them after a partial
1919  about the match so far is left in them after a partial match. There is more  match. There is more discussion of this facility in the
 discussion of this facility in the  
1920  .\" HREF  .\" HREF
1921  \fBpcrepartial\fP  \fBpcrepartial\fP
1922  .\"  .\"
# Line 1870  Cambridge CB2 3QH, England. Line 2020  Cambridge CB2 3QH, England.
2020  .rs  .rs
2021  .sp  .sp
2022  .nf  .nf
2023  Last updated: 13 June 2007  Last updated: 11 September 2009
2024  Copyright (c) 1997-2007 University of Cambridge.  Copyright (c) 1997-2009 University of Cambridge.
2025  .fi  .fi

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