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revision 461 by ph10, Mon Oct 5 10:59:35 2009 UTC revision 572 by ph10, Wed Nov 17 17:55:57 2010 UTC
# Line 132  an application that uses PCRE. The heade Line 132  an application that uses PCRE. The heade
132  and PCRE_MINOR to contain the major and minor release numbers for the library.  and PCRE_MINOR to contain the major and minor release numbers for the library.
133  Applications can use these to include support for different releases of PCRE.  Applications can use these to include support for different releases of PCRE.
134  .P  .P
135    In a Windows environment, if you want to statically link an application program
136    against a non-dll \fBpcre.a\fP file, you must define PCRE_STATIC before
137    including \fBpcre.h\fP or \fBpcrecpp.h\fP, because otherwise the
138    \fBpcre_malloc()\fP and \fBpcre_free()\fP exported functions will be declared
139    \fB__declspec(dllimport)\fP, with unwanted results.
140    .P
141  The functions \fBpcre_compile()\fP, \fBpcre_compile2()\fP, \fBpcre_study()\fP,  The functions \fBpcre_compile()\fP, \fBpcre_compile2()\fP, \fBpcre_study()\fP,
142  and \fBpcre_exec()\fP are used for compiling and matching regular expressions  and \fBpcre_exec()\fP are used for compiling and matching regular expressions
143  in a Perl-compatible manner. A sample program that demonstrates the simplest  in a Perl-compatible manner. A sample program that demonstrates the simplest
# Line 429  If \fIerrptr\fP is NULL, \fBpcre_compile Line 435  If \fIerrptr\fP is NULL, \fBpcre_compile
435  Otherwise, if compilation of a pattern fails, \fBpcre_compile()\fP returns  Otherwise, if compilation of a pattern fails, \fBpcre_compile()\fP returns
436  NULL, and sets the variable pointed to by \fIerrptr\fP to point to a textual  NULL, and sets the variable pointed to by \fIerrptr\fP to point to a textual
437  error message. This is a static string that is part of the library. You must  error message. This is a static string that is part of the library. You must
438  not try to free it. The byte offset from the start of the pattern to the  not try to free it. The offset from the start of the pattern to the byte that
439  character that was being processed when the error was discovered is placed in  was being processed when the error was discovered is placed in the variable
440  the variable pointed to by \fIerroffset\fP, which must not be NULL. If it is,  pointed to by \fIerroffset\fP, which must not be NULL. If it is, an immediate
441  an immediate error is given. Some errors are not detected until checks are  error is given. Some errors are not detected until checks are carried out when
442  carried out when the whole pattern has been scanned; in this case the offset is  the whole pattern has been scanned; in this case the offset is set to the end
443  set to the end of the pattern.  of the pattern.
444    .P
445    Note that the offset is in bytes, not characters, even in UTF-8 mode. It may
446    point into the middle of a UTF-8 character (for example, when
447    PCRE_ERROR_BADUTF8 is returned for an invalid UTF-8 string).
448  .P  .P
449  If \fBpcre_compile2()\fP is used instead of \fBpcre_compile()\fP, and the  If \fBpcre_compile2()\fP is used instead of \fBpcre_compile()\fP, and the
450  \fIerrorcodeptr\fP argument is not NULL, a non-zero error code number is  \fIerrorcodeptr\fP argument is not NULL, a non-zero error code number is
# Line 513  pattern. Line 523  pattern.
523  .sp  .sp
524    PCRE_DOTALL    PCRE_DOTALL
525  .sp  .sp
526  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
527  including those that indicate newline. Without it, a dot does not match when  any value, including one that indicates a newline. However, it only ever
528  the current position is at a newline. This option is equivalent to Perl's /s  matches one character, even if newlines are coded as CRLF. Without this option,
529  option, and it can be changed within a pattern by a (?s) option setting. A  a dot does not match when the current position is at a newline. This option is
530  negative class such as [^a] always matches newline characters, independent of  equivalent to Perl's /s option, and it can be changed within a pattern by a
531  the setting of this option.  (?s) option setting. A negative class such as [^a] always matches newline
532    characters, independent of the setting of this option.
533  .sp  .sp
534    PCRE_DUPNAMES    PCRE_DUPNAMES
535  .sp  .sp
# Line 540  unescaped # outside a character class an Line 551  unescaped # outside a character class an
551  ignored. This is equivalent to Perl's /x option, and it can be changed within a  ignored. This is equivalent to Perl's /x option, and it can be changed within a
552  pattern by a (?x) option setting.  pattern by a (?x) option setting.
553  .P  .P
554    Which characters are interpreted as newlines
555    is controlled by the options passed to \fBpcre_compile()\fP or by a special
556    sequence at the start of the pattern, as described in the section entitled
557    .\" HTML <a href="pcrepattern.html#newlines">
558    .\" </a>
559    "Newline conventions"
560    .\"
561    in the \fBpcrepattern\fP documentation. Note that the end of this type of
562    comment is a literal newline sequence in the pattern; escape sequences that
563    happen to represent a newline do not count.
564    .P
565  This option makes it possible to include comments inside complicated patterns.  This option makes it possible to include comments inside complicated patterns.
566  Note, however, that this applies only to data characters. Whitespace characters  Note, however, that this applies only to data characters. Whitespace characters
567  may never appear within special character sequences in a pattern, for example  may never appear within special character sequences in a pattern, for example
568  within the sequence (?( which introduces a conditional subpattern.  within the sequence (?( that introduces a conditional subpattern.
569  .sp  .sp
570    PCRE_EXTRA    PCRE_EXTRA
571  .sp  .sp
# Line 553  set, any backslash in a pattern that is Line 575  set, any backslash in a pattern that is
575  special meaning causes an error, thus reserving these combinations for future  special meaning causes an error, thus reserving these combinations for future
576  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
577  special meaning is treated as a literal. (Perl can, however, be persuaded to  special meaning is treated as a literal. (Perl can, however, be persuaded to
578  give a warning for this.) There are at present no other features controlled by  give an error for this, by running it with the -w option.) There are at present
579  this option. It can also be set by a (?X) option setting within a pattern.  no other features controlled by this option. It can also be set by a (?X)
580    option setting within a pattern.
581  .sp  .sp
582    PCRE_FIRSTLINE    PCRE_FIRSTLINE
583  .sp  .sp
# Line 617  option, the combination may or may not b Line 640  option, the combination may or may not b
640  PCRE_NEWLINE_CR with PCRE_NEWLINE_LF is equivalent to PCRE_NEWLINE_CRLF, but  PCRE_NEWLINE_CR with PCRE_NEWLINE_LF is equivalent to PCRE_NEWLINE_CRLF, but
641  other combinations may yield unused numbers and cause an error.  other combinations may yield unused numbers and cause an error.
642  .P  .P
643  The only time that a line break is specially recognized when compiling a  The only time that a line break in a pattern is specially recognized when
644  pattern is if PCRE_EXTENDED is set, and an unescaped # outside a character  compiling is when PCRE_EXTENDED is set. CR and LF are whitespace characters,
645  class is encountered. This indicates a comment that lasts until after the next  and so are ignored in this mode. Also, an unescaped # outside a character class
646  line break sequence. In other circumstances, line break sequences are treated  indicates a comment that lasts until after the next line break sequence. In
647  as literal data, except that in PCRE_EXTENDED mode, both CR and LF are treated  other circumstances, line break sequences in patterns are treated as literal
648  as whitespace characters and are therefore ignored.  data.
649  .P  .P
650  The newline option that is set at compile time becomes the default that is used  The newline option that is set at compile time becomes the default that is used
651  for \fBpcre_exec()\fP and \fBpcre_dfa_exec()\fP, but it can be overridden.  for \fBpcre_exec()\fP and \fBpcre_dfa_exec()\fP, but it can be overridden.
# Line 635  were followed by ?: but named parenthese Line 658  were followed by ?: but named parenthese
658  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
659  in Perl.  in Perl.
660  .sp  .sp
661      PCRE_UCP
662    .sp
663    This option changes the way PCRE processes \eB, \eb, \eD, \ed, \eS, \es, \eW,
664    \ew, and some of the POSIX character classes. By default, only ASCII characters
665    are recognized, but if PCRE_UCP is set, Unicode properties are used instead to
666    classify characters. More details are given in the section on
667    .\" HTML <a href="pcre.html#genericchartypes">
668    .\" </a>
669    generic character types
670    .\"
671    in the
672    .\" HREF
673    \fBpcrepattern\fP
674    .\"
675    page. If you set PCRE_UCP, matching one of the items it affects takes much
676    longer. The option is available only if PCRE has been compiled with Unicode
677    property support.
678    .sp
679    PCRE_UNGREEDY    PCRE_UNGREEDY
680  .sp  .sp
681  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
# Line 740  out of use. To avoid confusion, they hav Line 781  out of use. To avoid confusion, they hav
781    50  [this code is not in use]    50  [this code is not in use]
782    51  octal value is greater than \e377 (not in UTF-8 mode)    51  octal value is greater than \e377 (not in UTF-8 mode)
783    52  internal error: overran compiling workspace    52  internal error: overran compiling workspace
784    53  internal error: previously-checked referenced subpattern not found    53  internal error: previously-checked referenced subpattern
785            not found
786    54  DEFINE group contains more than one branch    54  DEFINE group contains more than one branch
787    55  repeating a DEFINE group is not allowed    55  repeating a DEFINE group is not allowed
788    56  inconsistent NEWLINE options    56  inconsistent NEWLINE options
789    57  \eg is not followed by a braced, angle-bracketed, or quoted    57  \eg is not followed by a braced, angle-bracketed, or quoted
790          name/number or by a plain number          name/number or by a plain number
791    58  a numbered reference must not be zero    58  a numbered reference must not be zero
792    59  (*VERB) with an argument is not supported    59  an argument is not allowed for (*ACCEPT), (*FAIL), or (*COMMIT)
793    60  (*VERB) not recognized    60  (*VERB) not recognized
794    61  number is too big    61  number is too big
795    62  subpattern name expected    62  subpattern name expected
796    63  digit expected after (?+    63  digit expected after (?+
797    64  ] is an invalid data character in JavaScript compatibility mode    64  ] is an invalid data character in JavaScript compatibility mode
798      65  different names for subpatterns of the same number are
799            not allowed
800      66  (*MARK) must have an argument
801      67  this version of PCRE is not compiled with PCRE_UCP support
802  .sp  .sp
803  The numbers 32 and 10000 in errors 48 and 49 are defaults; different values may  The numbers 32 and 10000 in errors 48 and 49 are defaults; different values may
804  be used if the limits were changed when PCRE was built.  be used if the limits were changed when PCRE was built.
# Line 818  Studying a pattern is also useful for no Line 864  Studying a pattern is also useful for no
864  single fixed starting character. A bitmap of possible starting bytes is  single fixed starting character. A bitmap of possible starting bytes is
865  created. This speeds up finding a position in the subject at which to start  created. This speeds up finding a position in the subject at which to start
866  matching.  matching.
867    .P
868    The two optimizations just described can be disabled by setting the
869    PCRE_NO_START_OPTIMIZE option when calling \fBpcre_exec()\fP or
870    \fBpcre_dfa_exec()\fP. You might want to do this if your pattern contains
871    callouts or (*MARK), and you want to make use of these facilities in cases
872    where matching fails. See the discussion of PCRE_NO_START_OPTIMIZE
873    .\" HTML <a href="#execoptions">
874    .\" </a>
875    below.
876    .\"
877  .  .
878  .  .
879  .\" HTML <a name="localesupport"></a>  .\" HTML <a name="localesupport"></a>
# Line 827  matching. Line 883  matching.
883  PCRE handles caseless matching, and determines whether characters are letters,  PCRE handles caseless matching, and determines whether characters are letters,
884  digits, or whatever, by reference to a set of tables, indexed by character  digits, or whatever, by reference to a set of tables, indexed by character
885  value. When running in UTF-8 mode, this applies only to characters with codes  value. When running in UTF-8 mode, this applies only to characters with codes
886  less than 128. Higher-valued codes never match escapes such as \ew or \ed, but  less than 128. By default, higher-valued codes never match escapes such as \ew
887  can be tested with \ep if PCRE is built with Unicode character property  or \ed, but they can be tested with \ep if PCRE is built with Unicode character
888  support. The use of locales with Unicode is discouraged. If you are handling  property support. Alternatively, the PCRE_UCP option can be set at compile
889  characters with codes greater than 128, you should either use UTF-8 and  time; this causes \ew and friends to use Unicode property support instead of
890  Unicode, or use locales, but not try to mix the two.  built-in tables. The use of locales with Unicode is discouraged. If you are
891    handling characters with codes greater than 128, you should either use UTF-8
892    and Unicode, or use locales, but not try to mix the two.
893  .P  .P
894  PCRE contains an internal set of tables that are used when the final argument  PCRE contains an internal set of tables that are used when the final argument
895  of \fBpcre_compile()\fP is NULL. These are sufficient for many applications.  of \fBpcre_compile()\fP is NULL. These are sufficient for many applications.
# Line 1210  fields (not necessarily in this order): Line 1268  fields (not necessarily in this order):
1268    unsigned long int \fImatch_limit_recursion\fP;    unsigned long int \fImatch_limit_recursion\fP;
1269    void *\fIcallout_data\fP;    void *\fIcallout_data\fP;
1270    const unsigned char *\fItables\fP;    const unsigned char *\fItables\fP;
1271      unsigned char **\fImark\fP;
1272  .sp  .sp
1273  The \fIflags\fP field is a bitmap that specifies which of the other fields  The \fIflags\fP field is a bitmap that specifies which of the other fields
1274  are set. The flag bits are:  are set. The flag bits are:
# Line 1219  are set. The flag bits are: Line 1278  are set. The flag bits are:
1278    PCRE_EXTRA_MATCH_LIMIT_RECURSION    PCRE_EXTRA_MATCH_LIMIT_RECURSION
1279    PCRE_EXTRA_CALLOUT_DATA    PCRE_EXTRA_CALLOUT_DATA
1280    PCRE_EXTRA_TABLES    PCRE_EXTRA_TABLES
1281      PCRE_EXTRA_MARK
1282  .sp  .sp
1283  Other flag bits should be set to zero. The \fIstudy_data\fP field is set in the  Other flag bits should be set to zero. The \fIstudy_data\fP field is set in the
1284  \fBpcre_extra\fP block that is returned by \fBpcre_study()\fP, together with  \fBpcre_extra\fP block that is returned by \fBpcre_study()\fP, together with
# Line 1281  called. See the Line 1341  called. See the
1341  \fBpcreprecompile\fP  \fBpcreprecompile\fP
1342  .\"  .\"
1343  documentation for a discussion of saving compiled patterns for later use.  documentation for a discussion of saving compiled patterns for later use.
1344    .P
1345    If PCRE_EXTRA_MARK is set in the \fIflags\fP field, the \fImark\fP field must
1346    be set to point to a \fBchar *\fP variable. If the pattern contains any
1347    backtracking control verbs such as (*MARK:NAME), and the execution ends up with
1348    a name to pass back, a pointer to the name string (zero terminated) is placed
1349    in the variable pointed to by the \fImark\fP field. The names are within the
1350    compiled pattern; if you wish to retain such a name you must copy it before
1351    freeing the memory of a compiled pattern. If there is no name to pass back, the
1352    variable pointed to by the \fImark\fP field set to NULL. For details of the
1353    backtracking control verbs, see the section entitled
1354    .\" HTML <a href="pcrepattern#backtrackcontrol">
1355    .\" </a>
1356    "Backtracking control"
1357    .\"
1358    in the
1359    .\" HREF
1360    \fBpcrepattern\fP
1361    .\"
1362    documentation.
1363    .
1364  .  .
1365  .\" HTML <a name="execoptions"></a>  .\" HTML <a name="execoptions"></a>
1366  .SS "Option bits for \fBpcre_exec()\fP"  .SS "Option bits for \fBpcre_exec()\fP"
# Line 1386  the Line 1466  the
1466  .\" HREF  .\" HREF
1467  \fBpcredemo\fP  \fBpcredemo\fP
1468  .\"  .\"
1469  sample program.  sample program. In the most general case, you have to check to see if the
1470    newline convention recognizes CRLF as a newline, and if so, and the current
1471    character is CR followed by LF, advance the starting offset by two characters
1472    instead of one.
1473  .sp  .sp
1474    PCRE_NO_START_OPTIMIZE    PCRE_NO_START_OPTIMIZE
1475  .sp  .sp
1476  There are a number of optimizations that \fBpcre_exec()\fP uses at the start of  There are a number of optimizations that \fBpcre_exec()\fP uses at the start of
1477  a match, in order to speed up the process. For example, if it is known that a  a match, in order to speed up the process. For example, if it is known that an
1478  match must start with a specific character, it searches the subject for that  unanchored match must start with a specific character, it searches the subject
1479  character, and fails immediately if it cannot find it, without actually running  for that character, and fails immediately if it cannot find it, without
1480  the main matching function. When callouts are in use, these optimizations can  actually running the main matching function. This means that a special item
1481  cause them to be skipped. This option disables the "start-up" optimizations,  such as (*COMMIT) at the start of a pattern is not considered until after a
1482  causing performance to suffer, but ensuring that the callouts do occur.  suitable starting point for the match has been found. When callouts or (*MARK)
1483    items are in use, these "start-up" optimizations can cause them to be skipped
1484    if the pattern is never actually used. The start-up optimizations are in effect
1485    a pre-scan of the subject that takes place before the pattern is run.
1486    .P
1487    The PCRE_NO_START_OPTIMIZE option disables the start-up optimizations, possibly
1488    causing performance to suffer, but ensuring that in cases where the result is
1489    "no match", the callouts do occur, and that items such as (*COMMIT) and (*MARK)
1490    are considered at every possible starting position in the subject string.
1491    Setting PCRE_NO_START_OPTIMIZE can change the outcome of a matching operation.
1492    Consider the pattern
1493    .sp
1494      (*COMMIT)ABC
1495    .sp
1496    When this is compiled, PCRE records the fact that a match must start with the
1497    character "A". Suppose the subject string is "DEFABC". The start-up
1498    optimization scans along the subject, finds "A" and runs the first match
1499    attempt from there. The (*COMMIT) item means that the pattern must match the
1500    current starting position, which in this case, it does. However, if the same
1501    match is run with PCRE_NO_START_OPTIMIZE set, the initial scan along the
1502    subject string does not happen. The first match attempt is run starting from
1503    "D" and when this fails, (*COMMIT) prevents any further matches being tried, so
1504    the overall result is "no match". If the pattern is studied, more start-up
1505    optimizations may be used. For example, a minimum length for the subject may be
1506    recorded. Consider the pattern
1507    .sp
1508      (*MARK:A)(X|Y)
1509    .sp
1510    The minimum length for a match is one character. If the subject is "ABC", there
1511    will be attempts to match "ABC", "BC", "C", and then finally an empty string.
1512    If the pattern is studied, the final attempt does not take place, because PCRE
1513    knows that the subject is too short, and so the (*MARK) is never encountered.
1514    In this case, studying the pattern does not affect the overall match result,
1515    which is still "no match", but it does affect the auxiliary information that is
1516    returned.
1517  .sp  .sp
1518    PCRE_NO_UTF8_CHECK    PCRE_NO_UTF8_CHECK
1519  .sp  .sp
# Line 1414  in the main Line 1531  in the main
1531  \fBpcre\fP  \fBpcre\fP
1532  .\"  .\"
1533  page. If an invalid UTF-8 sequence of bytes is found, \fBpcre_exec()\fP returns  page. If an invalid UTF-8 sequence of bytes is found, \fBpcre_exec()\fP returns
1534  the error PCRE_ERROR_BADUTF8. If \fIstartoffset\fP contains an invalid value,  the error PCRE_ERROR_BADUTF8 or, if PCRE_PARTIAL_HARD is set and the problem is
1535  PCRE_ERROR_BADUTF8_OFFSET is returned.  a truncated UTF-8 character at the end of the subject, PCRE_ERROR_SHORTUTF8. If
1536    \fIstartoffset\fP contains a value that does not point to the start of a UTF-8
1537    character (or to the end of the subject), PCRE_ERROR_BADUTF8_OFFSET is
1538    returned.
1539  .P  .P
1540  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
1541  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
1542  calling \fBpcre_exec()\fP. You might want to do this for the second and  calling \fBpcre_exec()\fP. You might want to do this for the second and
1543  subsequent calls to \fBpcre_exec()\fP if you are making repeated calls to find  subsequent calls to \fBpcre_exec()\fP if you are making repeated calls to find
1544  all the matches in a single subject string. However, you should be sure that  all the matches in a single subject string. However, you should be sure that
1545  the value of \fIstartoffset\fP points to the start of a UTF-8 character. When  the value of \fIstartoffset\fP points to the start of a UTF-8 character (or the
1546  PCRE_NO_UTF8_CHECK is set, the effect of passing an invalid UTF-8 string as a  end of the subject). When PCRE_NO_UTF8_CHECK is set, the effect of passing an
1547  subject, or a value of \fIstartoffset\fP that does not point to the start of a  invalid UTF-8 string as a subject or an invalid value of \fIstartoffset\fP is
1548  UTF-8 character, is undefined. Your program may crash.  undefined. Your program may crash.
1549  .sp  .sp
1550    PCRE_PARTIAL_HARD    PCRE_PARTIAL_HARD
1551    PCRE_PARTIAL_SOFT    PCRE_PARTIAL_SOFT
# Line 1434  These options turn on the partial matchi Line 1554  These options turn on the partial matchi
1554  compatibility, PCRE_PARTIAL is a synonym for PCRE_PARTIAL_SOFT. A partial match  compatibility, PCRE_PARTIAL is a synonym for PCRE_PARTIAL_SOFT. A partial match
1555  occurs if the end of the subject string is reached successfully, but there are  occurs if the end of the subject string is reached successfully, but there are
1556  not enough subject characters to complete the match. If this happens when  not enough subject characters to complete the match. If this happens when
1557  PCRE_PARTIAL_HARD is set, \fBpcre_exec()\fP immediately returns  PCRE_PARTIAL_SOFT (but not PCRE_PARTIAL_HARD) is set, matching continues by
1558  PCRE_ERROR_PARTIAL. Otherwise, if PCRE_PARTIAL_SOFT is set, matching continues  testing any remaining alternatives. Only if no complete match can be found is
1559  by testing any other alternatives. Only if they all fail is PCRE_ERROR_PARTIAL  PCRE_ERROR_PARTIAL returned instead of PCRE_ERROR_NOMATCH. In other words,
1560  returned (instead of PCRE_ERROR_NOMATCH). The portion of the string that  PCRE_PARTIAL_SOFT says that the caller is prepared to handle a partial match,
1561  was inspected when the partial match was found is set as the first matching  but only if no complete match can be found.
1562  string. There is a more detailed discussion in the  .P
1563    If PCRE_PARTIAL_HARD is set, it overrides PCRE_PARTIAL_SOFT. In this case, if a
1564    partial match is found, \fBpcre_exec()\fP immediately returns
1565    PCRE_ERROR_PARTIAL, without considering any other alternatives. In other words,
1566    when PCRE_PARTIAL_HARD is set, a partial match is considered to be more
1567    important that an alternative complete match.
1568    .P
1569    In both cases, the portion of the string that was inspected when the partial
1570    match was found is set as the first matching string. There is a more detailed
1571    discussion of partial and multi-segment matching, with examples, in the
1572  .\" HREF  .\" HREF
1573  \fBpcrepartial\fP  \fBpcrepartial\fP
1574  .\"  .\"
1575  documentation.  documentation.
1576  .  .
1577    .
1578  .SS "The string to be matched by \fBpcre_exec()\fP"  .SS "The string to be matched by \fBpcre_exec()\fP"
1579  .rs  .rs
1580  .sp  .sp
1581  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
1582  \fIsubject\fP, a length (in bytes) in \fIlength\fP, and a starting byte offset  \fIsubject\fP, a length (in bytes) in \fIlength\fP, and a starting byte offset
1583  in \fIstartoffset\fP. In UTF-8 mode, the byte offset must point to the start of  in \fIstartoffset\fP. If this is negative or greater than the length of the
1584  a UTF-8 character. Unlike the pattern string, the subject may contain binary  subject, \fBpcre_exec()\fP returns PCRE_ERROR_BADOFFSET. When the starting
1585  zero bytes. When the starting offset is zero, the search for a match starts at  offset is zero, the search for a match starts at the beginning of the subject,
1586  the beginning of the subject, and this is by far the most common case.  and this is by far the most common case. In UTF-8 mode, the byte offset must
1587    point to the start of a UTF-8 character (or the end of the subject). Unlike the
1588    pattern string, the subject may contain binary zero bytes.
1589  .P  .P
1590  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
1591  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 1473  start of the subject, which is deemed to Line 1605  start of the subject, which is deemed to
1605  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
1606  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.
1607  .P  .P
1608    Finding all the matches in a subject is tricky when the pattern can match an
1609    empty string. It is possible to emulate Perl's /g behaviour by first trying the
1610    match again at the same offset, with the PCRE_NOTEMPTY_ATSTART and
1611    PCRE_ANCHORED options, and then if that fails, advancing the starting offset
1612    and trying an ordinary match again. There is some code that demonstrates how to
1613    do this in the
1614    .\" HREF
1615    \fBpcredemo\fP
1616    .\"
1617    sample program. In the most general case, you have to check to see if the
1618    newline convention recognizes CRLF as a newline, and if so, and the current
1619    character is CR followed by LF, advance the starting offset by two characters
1620    instead of one.
1621    .P
1622  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
1623  attempt to match at the given offset is made. This can only succeed if the  attempt to match at the given offset is made. This can only succeed if the
1624  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.
1625  .  .
1626    .
1627  .SS "How \fBpcre_exec()\fP returns captured substrings"  .SS "How \fBpcre_exec()\fP returns captured substrings"
1628  .rs  .rs
1629  .sp  .sp
# Line 1543  Offset values that correspond to unused Line 1690  Offset values that correspond to unused
1690  expression are also set to -1. For example, if the string "abc" is matched  expression are also set to -1. For example, if the string "abc" is matched
1691  against the pattern (abc)(x(yz)?)? subpatterns 2 and 3 are not matched. The  against the pattern (abc)(x(yz)?)? subpatterns 2 and 3 are not matched. The
1692  return from the function is 2, because the highest used capturing subpattern  return from the function is 2, because the highest used capturing subpattern
1693  number is 1. However, you can refer to the offsets for the second and third  number is 1, and the offsets for for the second and third capturing subpatterns
1694  capturing subpatterns if you wish (assuming the vector is large enough, of  (assuming the vector is large enough, of course) are set to -1.
1695  course).  .P
1696    \fBNote\fP: Elements of \fIovector\fP that do not correspond to capturing
1697    parentheses in the pattern are never changed. That is, if a pattern contains
1698    \fIn\fP capturing parentheses, no more than \fIovector[0]\fP to
1699    \fIovector[2n+1]\fP are set by \fBpcre_exec()\fP. The other elements retain
1700    whatever values they previously had.
1701  .P  .P
1702  Some convenience functions are provided for extracting the captured substrings  Some convenience functions are provided for extracting the captured substrings
1703  as separate strings. These are described below.  as separate strings. These are described below.
# Line 1591  If a pattern contains back references, b Line 1743  If a pattern contains back references, b
1743  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
1744  call via \fBpcre_malloc()\fP fails, this error is given. The memory is  call via \fBpcre_malloc()\fP fails, this error is given. The memory is
1745  automatically freed at the end of matching.  automatically freed at the end of matching.
1746    .P
1747    This error is also given if \fBpcre_stack_malloc()\fP fails in
1748    \fBpcre_exec()\fP. This can happen only when PCRE has been compiled with
1749    \fB--disable-stack-for-recursion\fP.
1750  .sp  .sp
1751    PCRE_ERROR_NOSUBSTRING    (-7)    PCRE_ERROR_NOSUBSTRING    (-7)
1752  .sp  .sp
# Line 1616  documentation for details. Line 1772  documentation for details.
1772    PCRE_ERROR_BADUTF8        (-10)    PCRE_ERROR_BADUTF8        (-10)
1773  .sp  .sp
1774  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.
1775    However, if PCRE_PARTIAL_HARD is set and the problem is a truncated UTF-8
1776    character at the end of the subject, PCRE_ERROR_SHORTUTF8 is used instead.
1777  .sp  .sp
1778    PCRE_ERROR_BADUTF8_OFFSET (-11)    PCRE_ERROR_BADUTF8_OFFSET (-11)
1779  .sp  .sp
1780  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 valid, but the value
1781  of \fIstartoffset\fP did not point to the beginning of a UTF-8 character.  of \fIstartoffset\fP did not point to the beginning of a UTF-8 character or the
1782    end of the subject.
1783  .sp  .sp
1784    PCRE_ERROR_PARTIAL        (-12)    PCRE_ERROR_PARTIAL        (-12)
1785  .sp  .sp
# Line 1655  description above. Line 1814  description above.
1814    PCRE_ERROR_BADNEWLINE     (-23)    PCRE_ERROR_BADNEWLINE     (-23)
1815  .sp  .sp
1816  An invalid combination of PCRE_NEWLINE_\fIxxx\fP options was given.  An invalid combination of PCRE_NEWLINE_\fIxxx\fP options was given.
1817    .sp
1818      PCRE_ERROR_BADOFFSET      (-24)
1819    .sp
1820    The value of \fIstartoffset\fP was negative or greater than the length of the
1821    subject, that is, the value in \fIlength\fP.
1822    .sp
1823      PCRE_ERROR_SHORTUTF8      (-25)
1824    .sp
1825    The subject string ended with an incomplete (truncated) UTF-8 character, and
1826    the PCRE_PARTIAL_HARD option was set. Without this option, PCRE_ERROR_BADUTF8
1827    is returned in this situation.
1828  .P  .P
1829  Error numbers -16 to -20 and -22 are not used by \fBpcre_exec()\fP.  Error numbers -16 to -20 and -22 are not used by \fBpcre_exec()\fP.
1830  .  .
# Line 1939  Here is an example of a simple call to \ Line 2109  Here is an example of a simple call to \
2109  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
2110  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,
2111  PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY, PCRE_NOTEMPTY_ATSTART,  PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY, PCRE_NOTEMPTY_ATSTART,
2112  PCRE_NO_UTF8_CHECK, PCRE_PARTIAL_HARD, PCRE_PARTIAL_SOFT, PCRE_DFA_SHORTEST,  PCRE_NO_UTF8_CHECK, PCRE_BSR_ANYCRLF, PCRE_BSR_UNICODE, PCRE_NO_START_OPTIMIZE,
2113  and PCRE_DFA_RESTART. All but the last four of these are exactly the same as  PCRE_PARTIAL_HARD, PCRE_PARTIAL_SOFT, PCRE_DFA_SHORTEST, and PCRE_DFA_RESTART.
2114  for \fBpcre_exec()\fP, so their description is not repeated here.  All but the last four of these are exactly the same as for \fBpcre_exec()\fP,
2115    so their description is not repeated here.
2116  .sp  .sp
2117    PCRE_PARTIAL_HARD    PCRE_PARTIAL_HARD
2118    PCRE_PARTIAL_SOFT    PCRE_PARTIAL_SOFT
# Line 1956  is converted into PCRE_ERROR_PARTIAL if Line 2127  is converted into PCRE_ERROR_PARTIAL if
2127  there have been no complete matches, but there is still at least one matching  there have been no complete matches, but there is still at least one matching
2128  possibility. The portion of the string that was inspected when the longest  possibility. The portion of the string that was inspected when the longest
2129  partial match was found is set as the first matching string in both cases.  partial match was found is set as the first matching string in both cases.
2130    There is a more detailed discussion of partial and multi-segment matching, with
2131    examples, in the
2132    .\" HREF
2133    \fBpcrepartial\fP
2134    .\"
2135    documentation.
2136  .sp  .sp
2137    PCRE_DFA_SHORTEST    PCRE_DFA_SHORTEST
2138  .sp  .sp
# Line 2075  Cambridge CB2 3QH, England. Line 2252  Cambridge CB2 3QH, England.
2252  .rs  .rs
2253  .sp  .sp
2254  .nf  .nf
2255  Last updated: 03 October 2009  Last updated: 13 November 2010
2256  Copyright (c) 1997-2009 University of Cambridge.  Copyright (c) 1997-2010 University of Cambridge.
2257  .fi  .fi

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