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

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-revision 428 by ph10,
Mon Aug 31 17:10:26 2009 UTC
+revision 526 by ph10,
Wed May 26 10:54:18 2010 UTC
 Line 132 
 an application that uses PCRE. The heade
  and PCRE_MINOR to contain the major and minor release numbers for the library.
  Applications can use these to include support for different releases of PCRE.
  .P
+ In a Windows environment, if you want to statically link an application program
+ against a non-dll \fBpcre.a\fP file, you must define PCRE_STATIC before
+ including \fBpcre.h\fP or \fBpcrecpp.h\fP, because otherwise the
+ \fBpcre_malloc()\fP and \fBpcre_free()\fP exported functions will be declared
+ \fB__declspec(dllimport)\fP, with unwanted results.
+ .P
  The functions \fBpcre_compile()\fP, \fBpcre_compile2()\fP, \fBpcre_study()\fP,
  and \fBpcre_exec()\fP are used for compiling and matching regular expressions
  in a Perl-compatible manner. A sample program that demonstrates the simplest
- 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
- distribution. The
+ source distribution. A listing of this program is given in the
+ .\" HREF
+ \fBpcredemo\fP
+ .\"
+ documentation, and the
  .\" HREF
  \fBpcresample\fP
  .\"
-Line 145 
 documentation describes how to compile a
+Line 155 
 documentation describes how to compile a
  A second matching function, \fBpcre_dfa_exec()\fP, which is not
  Perl-compatible, is also provided. This uses a different algorithm for the
  matching. The alternative algorithm finds all possible matches (at a given
- 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
- does not return captured substrings. A description of the two matching
+ lookbehind assertions). However, this algorithm does not return captured
- algorithms and their advantages and disadvantages is given in the
+ substrings. A description of the two matching algorithms and their advantages
+ and disadvantages is given in the
  .\" HREF
  \fBpcrematching\fP
  .\"
-Line 390 
 avoiding the use of the stack.
+Line 401 
 avoiding the use of the stack.
  Either of the functions \fBpcre_compile()\fP or \fBpcre_compile2()\fP can be
  called to compile a pattern into an internal form. The only difference between
  the two interfaces is that \fBpcre_compile2()\fP has an additional argument,
- \fIerrorcodeptr\fP, via which a numerical error code can be returned.
+ \fIerrorcodeptr\fP, via which a numerical error code can be returned. To avoid
+ too much repetition, we refer just to \fBpcre_compile()\fP below, but the
+ information applies equally to \fBpcre_compile2()\fP.
  .P
  The pattern is a C string terminated by a binary zero, and is passed in the
  \fIpattern\fP argument. A pointer to a single block of memory that is obtained
-Line 407 
 argument, which is an address (see below
+Line 420 
 argument, which is an address (see below
  The \fIoptions\fP argument contains various bit settings that affect the
  compilation. It should be zero if no options are required. The available
  options are described below. Some of them (in particular, those that are
- compatible with Perl, but also some others) can also be set and unset from
+ compatible with Perl, but some others as well) can also be set and unset from
  within the pattern (see the detailed description in the
  .\" HREF
  \fBpcrepattern\fP
  .\"
  documentation). For those options that can be different in different parts of
- the pattern, the contents of the \fIoptions\fP argument specifies their initial
+ the pattern, the contents of the \fIoptions\fP argument specifies their
- settings at the start of compilation and execution. The PCRE_ANCHORED and
+ settings at the start of compilation and execution. The PCRE_ANCHORED,
- PCRE_NEWLINE_\fIxxx\fP options can be set at the time of matching as well as at
+ PCRE_BSR_\fIxxx\fP, and PCRE_NEWLINE_\fIxxx\fP options can be set at the time
- compile time.
+ of matching as well as at compile time.
  .P
  If \fIerrptr\fP is NULL, \fBpcre_compile()\fP returns NULL immediately.
  Otherwise, if compilation of a pattern fails, \fBpcre_compile()\fP returns
  NULL, and sets the variable pointed to by \fIerrptr\fP to point to a textual
  error message. This is a static string that is part of the library. You must
- not try to free it. The offset from the start of the pattern to the character
+ not try to free it. The byte offset from the start of the pattern to the
- where the error was discovered is placed in the variable pointed to by
+ character that was being processed when the error was discovered is placed in
- \fIerroffset\fP, which must not be NULL. If it is, an immediate error is given.
+ the variable pointed to by \fIerroffset\fP, which must not be NULL. If it is,
+ an immediate error is given. Some errors are not detected until checks are
+ carried out when the whole pattern has been scanned; in this case the offset is
+ set to the end of the pattern.
  .P
  If \fBpcre_compile2()\fP is used instead of \fBpcre_compile()\fP, and the
  \fIerrorcodeptr\fP argument is not NULL, a non-zero error code number is
-Line 543 
 set, any backslash in a pattern that is
+Line 559 
 set, any backslash in a pattern that is
  special meaning causes an error, thus reserving these combinations for future
  expansion. By default, as in Perl, a backslash followed by a letter with no
  special meaning is treated as a literal. (Perl can, however, be persuaded to
- 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
- 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)
+ option setting within a pattern.
  .sp
    PCRE_FIRSTLINE
  .sp
-Line 625 
 were followed by ?: but named parenthese
+Line 642 
 were followed by ?: but named parenthese
  they acquire numbers in the usual way). There is no equivalent of this option
  in Perl.
  .sp
+   PCRE_UCP
+ .sp
+ This option changes the way PCRE processes \eb, \ed, \es, \ew, and some of the
+ POSIX character classes. By default, only ASCII characters are recognized, but
+ if PCRE_UCP is set, Unicode properties are used instead to classify characters.
+ More details are given in the section on
+ .\" HTML <a href="pcre.html#genericchartypes">
+ .\" </a>
+ generic character types
+ .\"
+ in the
+ .\" HREF
+ \fBpcrepattern\fP
+ .\"
+ page. If you set PCRE_UCP, matching one of the items it affects takes much
+ longer. The option is available only if PCRE has been compiled with Unicode
+ property support.
+ .sp
    PCRE_UNGREEDY
  .sp
  This option inverts the "greediness" of the quantifiers so that they are not
-Line 737 
 out of use. To avoid confusion, they hav
+Line 772 
 out of use. To avoid confusion, they hav
  \eg is not followed by a braced, angle-bracketed, or quoted
          name/number or by a plain number
  a numbered reference must not be zero
- (*VERB) with an argument is not supported
+ an argument is not allowed for (*ACCEPT), (*FAIL), or (*COMMIT)
  (*VERB) not recognized
  number is too big
  subpattern name expected
  digit expected after (?+
  ] is an invalid data character in JavaScript compatibility mode
+ different names for subpatterns of the same number are not allowed
+ (*MARK) must have an argument
+ this version of PCRE is not compiled with PCRE_UCP support
  .sp
  The numbers 32 and 10000 in errors 48 and 49 are defaults; different values may
  be used if the limits were changed when PCRE was built.
-Line 764 
 help speed up matching, \fBpcre_study()\
+Line 802 
 help speed up matching, \fBpcre_study()\
  results of the study.
  .P
  The returned value from \fBpcre_study()\fP can be passed directly to
- \fBpcre_exec()\fP. However, a \fBpcre_extra\fP block also contains other
+ \fBpcre_exec()\fP or \fBpcre_dfa_exec()\fP. However, a \fBpcre_extra\fP block
- fields that can be set by the caller before the block is passed; these are
+ also contains other fields that can be set by the caller before the block is
- described
+ passed; these are described
  .\" HTML <a href="#extradata">
  .\" </a>
  below
  .\"
  in the section on matching a pattern.
  .P
- If studying the pattern does not produce any additional information
+ If studying the pattern does not produce any useful information,
  \fBpcre_study()\fP returns NULL. In that circumstance, if the calling program
- wants to pass any of the other fields to \fBpcre_exec()\fP, it must set up its
+ wants to pass any of the other fields to \fBpcre_exec()\fP or
- own \fBpcre_extra\fP block.
+ \fBpcre_dfa_exec()\fP, it must set up its own \fBpcre_extra\fP block.
  .P
  The second argument of \fBpcre_study()\fP contains option bits. At present, no
  options are defined, and this argument should always be zero.
-Line 796 
 This is a typical call to \fBpcre_study\
+Line 834 
 This is a typical call to \fBpcre_study\
 ,              /* no options exist */
      &error);        /* set to NULL or points to a message */
  .sp
- At present, studying a pattern is useful only for non-anchored patterns that do
+ Studying a pattern does two things: first, a lower bound for the length of
- not have a single fixed starting character. A bitmap of possible starting
+ subject string that is needed to match the pattern is computed. This does not
- bytes is created.
+ mean that there are any strings of that length that match, but it does
+ guarantee that no shorter strings match. The value is used by
+ \fBpcre_exec()\fP and \fBpcre_dfa_exec()\fP to avoid wasting time by trying to
+ match strings that are shorter than the lower bound. You can find out the value
+ in a calling program via the \fBpcre_fullinfo()\fP function.
+ .P
+ Studying a pattern is also useful for non-anchored patterns that do not have a
+ single fixed starting character. A bitmap of possible starting bytes is
+ created. This speeds up finding a position in the subject at which to start
+ matching.
  .
  .
  .\" HTML <a name="localesupport"></a>
-Line 808 
 bytes is created.
+Line 855 
 bytes is created.
  PCRE handles caseless matching, and determines whether characters are letters,
  digits, or whatever, by reference to a set of tables, indexed by character
  value. When running in UTF-8 mode, this applies only to characters with codes
- 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
- 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
- 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
- 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
- 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
+ handling characters with codes greater than 128, you should either use UTF-8
+ and Unicode, or use locales, but not try to mix the two.
  .P
  PCRE contains an internal set of tables that are used when the final argument
  of \fBpcre_compile()\fP is NULL. These are sufficient for many applications.
-Line 963 
 follows something of variable length. Fo
+Line 1012 
 follows something of variable length. Fo
  /^a\ed+z\ed+/ the returned value is "z", but for /^a\edz\ed/ the returned value
  is -1.
  .sp
+   PCRE_INFO_MINLENGTH
+ .sp
+ If the pattern was studied and a minimum length for matching subject strings
+ was computed, its value is returned. Otherwise the returned value is -1. The
+ value is a number of characters, not bytes (this may be relevant in UTF-8
+ mode). The fourth argument should point to an \fBint\fP variable. A
+ non-negative value is a lower bound to the length of any matching string. There
+ may not be any strings of that length that do actually match, but every string
+ that does match is at least that long.
+ .sp
    PCRE_INFO_NAMECOUNT
    PCRE_INFO_NAMEENTRYSIZE
    PCRE_INFO_NAMETABLE
-Line 983 
 entry; both of these return an \fBint\fP
+Line 1042 
 entry; both of these return an \fBint\fP
  length of the longest name. PCRE_INFO_NAMETABLE returns a pointer to the first
  entry of the table (a pointer to \fBchar\fP). The first two bytes of each entry
  are the number of the capturing parenthesis, most significant byte first. The
- rest of the entry is the corresponding name, zero terminated. The names are in
+ rest of the entry is the corresponding name, zero terminated.
- alphabetical order. When PCRE_DUPNAMES is set, duplicate names are in order of
+ .P
- their parentheses numbers. For example, consider the following pattern (assume
+ The names are in alphabetical order. Duplicate names may appear if (?| is used
- PCRE_EXTENDED is set, so white space - including newlines - is ignored):
+ to create multiple groups with the same number, as described in the
+ .\" HTML <a href="pcrepattern.html#dupsubpatternnumber">
+ .\" </a>
+ section on duplicate subpattern numbers
+ .\"
+ in the
+ .\" HREF
+ \fBpcrepattern\fP
+ .\"
+ page. Duplicate names for subpatterns with different numbers are permitted only
+ if PCRE_DUPNAMES is set. In all cases of duplicate names, they appear in the
+ table in the order in which they were found in the pattern. In the absence of
+ (?| this is the order of increasing number; when (?| is used this is not
+ necessarily the case because later subpatterns may have lower numbers.
+ .P
+ As a simple example of the name/number table, consider the following pattern
+ (assume PCRE_EXTENDED is set, so white space - including newlines - is
+ ignored):
  .sp
  .\" JOIN
    (?<date> (?<year>(\ed\ed)?\ed\ed) -
-Line 1007 
 different for each compiled pattern.
+Line 1083 
 different for each compiled pattern.
  .sp
    PCRE_INFO_OKPARTIAL
  .sp
- 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
- fourth argument should point to an \fBint\fP variable. From release 8.00, this
+ \fBpcre_exec()\fP, otherwise 0. The fourth argument should point to an
- always returns 1, because the restrictions that previously applied to partial
+ \fBint\fP variable. From release 8.00, this always returns 1, because the
- matching have been lifted. The
+ restrictions that previously applied to partial matching have been lifted. The
  .\" HREF
  \fBpcrepartial\fP
  .\"
-Line 1051 
 variable.
+Line 1127 
 variable.
  Return the size of the data block pointed to by the \fIstudy_data\fP field in
  a \fBpcre_extra\fP block. That is, it is the value that was passed to
  \fBpcre_malloc()\fP when PCRE was getting memory into which to place the data
- created by \fBpcre_study()\fP. The fourth argument should point to a
+ created by \fBpcre_study()\fP. If \fBpcre_extra\fP is NULL, or there is no
+ study data, zero is returned. The fourth argument should point to a
  \fBsize_t\fP variable.
  .
  .
-Line 1113 
 is different. (This seems a highly unlik
+Line 1190 
 is different. (This seems a highly unlik
  .P
  The function \fBpcre_exec()\fP is called to match a subject string against a
  compiled pattern, which is passed in the \fIcode\fP argument. If the
- pattern has been studied, the result of the study should be passed in the
+ pattern was studied, the result of the study should be passed in the
  \fIextra\fP argument. This function is the main matching facility of the
  library, and it operates in a Perl-like manner. For specialist use there is
  also an alternative matching function, which is described
-Line 1163 
 fields (not necessarily in this order):
+Line 1240 
 fields (not necessarily in this order):
    unsigned long int \fImatch_limit_recursion\fP;
    void *\fIcallout_data\fP;
    const unsigned char *\fItables\fP;
+   unsigned char **\fImark\fP;
  .sp
  The \fIflags\fP field is a bitmap that specifies which of the other fields
  are set. The flag bits are:
-Line 1172 
 are set. The flag bits are:
+Line 1250 
 are set. The flag bits are:
    PCRE_EXTRA_MATCH_LIMIT_RECURSION
    PCRE_EXTRA_CALLOUT_DATA
    PCRE_EXTRA_TABLES
+   PCRE_EXTRA_MARK
  .sp
  Other flag bits should be set to zero. The \fIstudy_data\fP field is set in the
  \fBpcre_extra\fP block that is returned by \fBpcre_study()\fP, together with
-Line 1181 
 the block by setting the other fields an
+Line 1260 
 the block by setting the other fields an
  The \fImatch_limit\fP field provides a means of preventing PCRE from using up a
  vast amount of resources when running patterns that are not going to match,
  but which have a very large number of possibilities in their search trees. The
- classic example is the use of nested unlimited repeats.
+ classic example is a pattern that uses nested unlimited repeats.
  .P
  Internally, PCRE uses a function called \fBmatch()\fP which it calls repeatedly
  (sometimes recursively). The limit set by \fImatch_limit\fP is imposed on the
-Line 1214 
 with a \fBpcre_extra\fP block in which \
+Line 1293 
 with a \fBpcre_extra\fP block in which \
  PCRE_EXTRA_MATCH_LIMIT_RECURSION is set in the \fIflags\fP field. If the limit
  is exceeded, \fBpcre_exec()\fP returns PCRE_ERROR_RECURSIONLIMIT.
  .P
- 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,
- which is described in the
+ and is described in the
  .\" HREF
  \fBpcrecallout\fP
  .\"
-Line 1234 
 called. See the
+Line 1313 
 called. See the
  \fBpcreprecompile\fP
  .\"
  documentation for a discussion of saving compiled patterns for later use.
+ .P
+ If PCRE_EXTRA_MARK is set in the \fIflags\fP field, the \fImark\fP field must
+ be set to point to a \fBchar *\fP variable. If the pattern contains any
+ backtracking control verbs such as (*MARK:NAME), and the execution ends up with
+ a name to pass back, a pointer to the name string (zero terminated) is placed
+ in the variable pointed to by the \fImark\fP field. The names are within the
+ compiled pattern; if you wish to retain such a name you must copy it before
+ freeing the memory of a compiled pattern. If there is no name to pass back, the
+ variable pointed to by the \fImark\fP field set to NULL. For details of the
+ backtracking control verbs, see the section entitled
+ .\" HTML <a href="pcrepattern#backtrackcontrol">
+ .\" </a>
+ "Backtracking control"
+ .\"
+ in the
+ .\" HREF
+ \fBpcrepattern\fP
+ .\"
+ documentation.
+ .
  .
  .\" HTML <a name="execoptions"></a>
  .SS "Option bits for \fBpcre_exec()\fP"
-Line 1241 
 documentation for a discussion of saving
+Line 1340 
 documentation for a discussion of saving
  .sp
  The unused bits of the \fIoptions\fP argument for \fBpcre_exec()\fP must be
  zero. The only bits that may be set are PCRE_ANCHORED, PCRE_NEWLINE_\fIxxx\fP,
- PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY, PCRE_NO_START_OPTIMIZE,
+ PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY, PCRE_NOTEMPTY_ATSTART,
- PCRE_NO_UTF8_CHECK, PCRE_PARTIAL_SOFT, and PCRE_PARTIAL_HARD.
+ PCRE_NO_START_OPTIMIZE, PCRE_NO_UTF8_CHECK, PCRE_PARTIAL_SOFT, and
+ PCRE_PARTIAL_HARD.
  .sp
    PCRE_ANCHORED
  .sp
-Line 1317 
 match the empty string, the entire match
+Line 1417 
 match the empty string, the entire match
  .sp
    a?b?
  .sp
- 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
  string at the start of the subject. With PCRE_NOTEMPTY set, this match is not
  valid, so PCRE searches further into the string for occurrences of "a" or "b".
- .P
+ .sp
- Perl has no direct equivalent of PCRE_NOTEMPTY, but it does make a special case
+   PCRE_NOTEMPTY_ATSTART
- of a pattern match of the empty string within its \fBsplit()\fP function, and
+ .sp
- 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
- 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
- PCRE_NOTEMPTY and PCRE_ANCHORED, and then if that fails by advancing the
+ can occur only if the pattern contains \eK.
- starting offset (see below) and trying an ordinary match again. There is some
+ .P
- 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
+ does make a special case of a pattern match of the empty string within its
+ \fBsplit()\fP function, and when using the /g modifier. It is possible to
+ emulate Perl's behaviour after matching a null string by first trying the match
+ again at the same offset with PCRE_NOTEMPTY_ATSTART and PCRE_ANCHORED, and then
+ if that fails, by advancing the starting offset (see below) and trying an
+ ordinary match again. There is some code that demonstrates how to do this in
+ the
+ .\" HREF
+ \fBpcredemo\fP
+ .\"
+ sample program.
  .sp
    PCRE_NO_START_OPTIMIZE
  .sp
-Line 1368 
 PCRE_NO_UTF8_CHECK is set, the effect of
+Line 1479 
 PCRE_NO_UTF8_CHECK is set, the effect of
  subject, or a value of \fIstartoffset\fP that does not point to the start of a
  UTF-8 character, is undefined. Your program may crash.
  .sp
    PCRE_PARTIAL_HARD
    PCRE_PARTIAL_SOFT
  .sp
  These options turn on the partial matching feature. For backwards
-Line 1379 
 PCRE_PARTIAL_HARD is set, \fBpcre_exec()
+Line 1490 
 PCRE_PARTIAL_HARD is set, \fBpcre_exec()
  PCRE_ERROR_PARTIAL. Otherwise, if PCRE_PARTIAL_SOFT is set, matching continues
  by testing any other alternatives. Only if they all fail is PCRE_ERROR_PARTIAL
  returned (instead of PCRE_ERROR_NOMATCH). The portion of the string that
- provided the partial match is set as the first matching string. There is a more
+ was inspected when the partial match was found is set as the first matching
- detailed discussion in the
+ string. There is a more detailed discussion in the
  .\" HREF
  \fBpcrepartial\fP
  .\"
-Line 1468 
 the \fIovector\fP is not big enough to r
+Line 1579 
 the \fIovector\fP is not big enough to r
  has to get additional memory for use during matching. Thus it is usually
  advisable to supply an \fIovector\fP.
  .P
- The \fBpcre_info()\fP function can be used to find out how many capturing
+ The \fBpcre_fullinfo()\fP function can be used to find out how many capturing
  subpatterns there are in a compiled pattern. The smallest size for
  \fIovector\fP that will allow for \fIn\fP captured substrings, in addition to
  the offsets of the substring matched by the whole pattern, is (\fIn\fP+1)*3.
-Line 1575 
 documentation for details of partial mat
+Line 1686 
 documentation for details of partial mat
  .sp
  This code is no longer in use. It was formerly returned when the PCRE_PARTIAL
  option was used with a compiled pattern containing items that were not
  supported for partial matching. From release 8.00 onwards, there are no
  restrictions on partial matching.
  .sp
    PCRE_ERROR_INTERNAL       (-14)
-Line 1747 
 then call \fBpcre_copy_substring()\fP or
+Line 1858 
 then call \fBpcre_copy_substring()\fP or
  appropriate. \fBNOTE:\fP If PCRE_DUPNAMES is set and there are duplicate names,
  the behaviour may not be what you want (see the next section).
  .P
- \fBWarning:\fP If the pattern uses the "(?|" feature to set up multiple
+ \fBWarning:\fP If the pattern uses the (?| feature to set up multiple
- subpatterns with the same number, you cannot use names to distinguish them,
+ subpatterns with the same number, as described in the
- because names are not included in the compiled code. The matching process uses
+ .\" HTML <a href="pcrepattern.html#dupsubpatternnumber">
- only numbers.
+ .\" </a>
+ section on duplicate subpattern numbers
+ .\"
+ in the
+ .\" HREF
+ \fBpcrepattern\fP
+ .\"
+ page, you cannot use names to distinguish the different subpatterns, because
+ names are not included in the compiled code. The matching process uses only
+ numbers. For this reason, the use of different names for subpatterns of the
+ same number causes an error at compile time.
  .
  .SH "DUPLICATE SUBPATTERN NAMES"
  .rs
-Line 1760 
 only numbers.
+Line 1881 
 only numbers.
  .B const char *\fIname\fP, char **\fIfirst\fP, char **\fIlast\fP);
  .PP
  When a pattern is compiled with the PCRE_DUPNAMES option, names for subpatterns
- are not required to be unique. Normally, patterns with duplicate names are such
+ are not required to be unique. (Duplicate names are always allowed for
- that in any one match, only one of the named subpatterns participates. An
+ subpatterns with the same number, created by using the (?| feature. Indeed, if
- example is shown in the
+ such subpatterns are named, they are required to use the same names.)
+ .P
+ Normally, patterns with duplicate names are such that in any one match, only
+ one of the named subpatterns participates. An example is shown in the
  .\" HREF
  \fBpcrepattern\fP
  .\"
-Line 1826 
 a compiled pattern, using a matching alg
+Line 1950 
 a compiled pattern, using a matching alg
  just once, and does not backtrack. This has different characteristics to the
  normal algorithm, and is not compatible with Perl. Some of the features of PCRE
  patterns are not supported. Nevertheless, there are times when this kind of
- 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
- the
+ list of features that \fBpcre_dfa_exec()\fP does not support, see the
  .\" HREF
  \fBpcrematching\fP
  .\"
-Line 1866 
 Here is an example of a simple call to \
+Line 1990 
 Here is an example of a simple call to \
  .sp
  The unused bits of the \fIoptions\fP argument for \fBpcre_dfa_exec()\fP must be
  zero. The only bits that may be set are PCRE_ANCHORED, PCRE_NEWLINE_\fIxxx\fP,
- PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY, PCRE_NO_UTF8_CHECK, PCRE_PARTIAL_HARD,
+ PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY, PCRE_NOTEMPTY_ATSTART,
- PCRE_PARTIAL_SOFT, PCRE_DFA_SHORTEST, and PCRE_DFA_RESTART. All but the last
+ PCRE_NO_UTF8_CHECK, PCRE_PARTIAL_HARD, PCRE_PARTIAL_SOFT, PCRE_DFA_SHORTEST,
- four of these are exactly the same as for \fBpcre_exec()\fP, so their
+ and PCRE_DFA_RESTART. All but the last four of these are exactly the same as
- description is not repeated here.
+ for \fBpcre_exec()\fP, so their description is not repeated here.
  .sp
    PCRE_PARTIAL_HARD
    PCRE_PARTIAL_SOFT
  .sp
  These have the same general effect as they do for \fBpcre_exec()\fP, but the
  details are slightly different. When PCRE_PARTIAL_HARD is set for
-Line 1882 
 additional characters. This happens even
+Line 2006 
 additional characters. This happens even
  been found. When PCRE_PARTIAL_SOFT is set, the return code PCRE_ERROR_NOMATCH
  is converted into PCRE_ERROR_PARTIAL if the end of the subject is reached,
  there have been no complete matches, but there is still at least one matching
- possibility. The portion of the string that provided the longest partial match
+ possibility. The portion of the string that was inspected when the longest
- is set as the first matching string in both cases.
+ partial match was found is set as the first matching string in both cases.
  .sp
    PCRE_DFA_SHORTEST
  .sp
-Line 2003 
 Cambridge CB2 3QH, England.
+Line 2127 
 Cambridge CB2 3QH, England.
  .rs
  .sp
  .nf
- Last updated: 29 August 2009
+ Last updated: 26 May 2010
- Copyright (c) 1997-2009 University of Cambridge.
+ Copyright (c) 1997-2010 University of Cambridge.
  .fi

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