/[pcre]/code/trunk/doc/pcreapi.3
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revision 412 by ph10, Sat Apr 11 10:34:37 2009 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  .\"  .\"
# Line 145  documentation describes how to compile a Line 149  documentation describes how to compile a
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 1007  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
# Line 1213  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 1240  documentation for a discussion of saving Line 1246  documentation for a discussion of saving
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_START_OPTIMIZE,  PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY, PCRE_NOTEMPTY_ATSTART,
1250  PCRE_NO_UTF8_CHECK and PCRE_PARTIAL.  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 1316  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  .sp
1349    PCRE_NO_START_OPTIMIZE    PCRE_NO_START_OPTIMIZE
1350  .sp  .sp
# Line 1367  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 1568  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 1823  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 1863  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 1886  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 1996  Cambridge CB2 3QH, England. Line 2020  Cambridge CB2 3QH, England.
2020  .rs  .rs
2021  .sp  .sp
2022  .nf  .nf
2023  Last updated: 11 April 2009  Last updated: 11 September 2009
2024  Copyright (c) 1997-2009 University of Cambridge.  Copyright (c) 1997-2009 University of Cambridge.
2025  .fi  .fi

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