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authorph10 <ph10@6239d852-aaf2-0410-a92c-79f79f948069>2020-10-07 16:27:20 +0000
committerph10 <ph10@6239d852-aaf2-0410-a92c-79f79f948069>2020-10-07 16:27:20 +0000
commitfac6bb8db9d0828e998716a47cd1ad20e18a2e0a (patch)
tree62ac35c8262da3d545a3c070cc9e289c3db8afc5
parenta4c56b7ef4ee09f62b8bcae4354a2c45efbb38ce (diff)
downloadpcre2-fac6bb8db9d0828e998716a47cd1ad20e18a2e0a.tar.gz
Documentation update
git-svn-id: svn://vcs.exim.org/pcre2/code/trunk@1277 6239d852-aaf2-0410-a92c-79f79f948069
Diffstat
-rw-r--r--doc/html/pcre2api.html13
-rw-r--r--doc/html/pcre2compat.html77
-rw-r--r--doc/html/pcre2pattern.html46
-rw-r--r--doc/pcre2.txt2343
-rw-r--r--doc/pcre2compat.379
-rw-r--r--doc/pcre2pattern.39
6 files changed, 1311 insertions, 1256 deletions
diff --git a/doc/html/pcre2api.html b/doc/html/pcre2api.html
index 36c2e3d..5cd7ae0 100644
--- a/doc/html/pcre2api.html
+++ b/doc/html/pcre2api.html
@@ -1492,10 +1492,13 @@ letters in the subject. It is equivalent to Perl's /i option, and it can be
changed within a pattern by a (?i) option setting. If either PCRE2_UTF or
PCRE2_UCP is set, Unicode properties are used for all characters with more than
one other case, and for all characters whose code points are greater than
-U+007F. For lower valued characters with only one other case, a lookup table is
-used for speed. When neither PCRE2_UTF nor PCRE2_UCP is set, a lookup table is
-used for all code points less than 256, and higher code points (available only
-in 16-bit or 32-bit mode) are treated as not having another case.
+U+007F. Note that there are two ASCII characters, K and S, that, in addition to
+their lower case ASCII equivalents, are case-equivalent with U+212A (Kelvin
+sign) and U+017F (long S) respectively. For lower valued characters with only
+one other case, a lookup table is used for speed. When neither PCRE2_UTF nor
+PCRE2_UCP is set, a lookup table is used for all code points less than 256, and
+higher code points (available only in 16-bit or 32-bit mode) are treated as not
+having another case.
<pre>
PCRE2_DOLLAR_ENDONLY
</pre>
@@ -3956,7 +3959,7 @@ Cambridge, England.
</P>
<br><a name="SEC42" href="#TOC1">REVISION</a><br>
<P>
-Last updated: 19 March 2020
+Last updated: 05 October 2020
<br>
Copyright &copy; 1997-2020 University of Cambridge.
<br>
diff --git a/doc/html/pcre2compat.html b/doc/html/pcre2compat.html
index 0c72a9a..5238918 100644
--- a/doc/html/pcre2compat.html
+++ b/doc/html/pcre2compat.html
@@ -16,10 +16,10 @@ please consult the man page, in case the conversion went wrong.
DIFFERENCES BETWEEN PCRE2 AND PERL
</b><br>
<P>
-This document describes the differences in the ways that PCRE2 and Perl handle
-regular expressions. The differences described here are with respect to Perl
-versions 5.26, but as both Perl and PCRE2 are continually changing, the
-information may sometimes be out of date.
+This document describes some of the differences in the ways that PCRE2 and Perl
+handle regular expressions. The differences described here are with respect to
+Perl version 5.32.0, but as both Perl and PCRE2 are continually changing, the
+information may at times be out of date.
</P>
<P>
1. PCRE2 has only a subset of Perl's Unicode support. Details of what it does
@@ -33,12 +33,15 @@ they do not mean what you might think. For example, (?!a){3} does not assert
that the next three characters are not "a". It just asserts that the next
character is not "a" three times (in principle; PCRE2 optimizes this to run the
assertion just once). Perl allows some repeat quantifiers on other assertions,
-for example, \b* (but not \b{3}), but these do not seem to have any use.
+for example, \b* (but not \b{3}, though oddly it does allow ^{3}), but these
+do not seem to have any use. PCRE2 does not allow any kind of quantifier on
+non-lookaround assertions.
</P>
<P>
3. Capture groups that occur inside negative lookaround assertions are counted,
but their entries in the offsets vector are set only when a negative assertion
-is a condition that has a matching branch (that is, the condition is false).
+is a condition that has a matching branch (that is, the condition is false).
+Perl may set such capture groups in other circumstances.
</P>
<P>
4. The following Perl escape sequences are not supported: \F, \l, \L, \u,
@@ -56,10 +59,12 @@ interprets them.
built with Unicode support (the default). The properties that can be tested
with \p and \P are limited to the general category properties such as Lu and
Nd, script names such as Greek or Han, and the derived properties Any and L&.
-PCRE2 does support the Cs (surrogate) property, which Perl does not; the Perl
-documentation says "Because Perl hides the need for the user to understand the
-internal representation of Unicode characters, there is no need to implement
-the somewhat messy concept of surrogates."
+Both PCRE2 and Perl support the Cs (surrogate) property, but in PCRE2 its use
+is limited. See the
+<a href="pcre2pattern.html"><b>pcre2pattern</b></a>
+documentation for details. The long synonyms for property names that Perl
+supports (such as \p{Letter}) are not supported by PCRE2, nor is it permitted
+to prefix any of these properties with "Is".
</P>
<P>
6. PCRE2 supports the \Q...\E escape for quoting substrings. Characters
@@ -79,7 +84,8 @@ other character. Note the following examples:
\QA\B\E A\B A\B
\Q\\E \ \\E
</pre>
-The \Q...\E sequence is recognized both inside and outside character classes.
+The \Q...\E sequence is recognized both inside and outside character classes
+by both PCRE2 and Perl.
</P>
<P>
7. Fairly obviously, PCRE2 does not support the (?{code}) and (??{code})
@@ -94,13 +100,13 @@ to PCRE2 release 10.23, but from release 10.30 this changed, and backtracking
into subroutine calls is now supported, as in Perl.
</P>
<P>
-9. If any of the backtracking control verbs are used in a group that is called
-as a subroutine (whether or not recursively), their effect is confined to that
-group; it does not extend to the surrounding pattern. This is not always the
-case in Perl. In particular, if (*THEN) is present in a group that is called as
-a subroutine, its action is limited to that group, even if the group does not
-contain any | characters. Note that such groups are processed as anchored
-at the point where they are tested.
+9. In PCRE2, if any of the backtracking control verbs are used in a group that
+is called as a subroutine (whether or not recursively), their effect is
+confined to that group; it does not extend to the surrounding pattern. This is
+not always the case in Perl. In particular, if (*THEN) is present in a group
+that is called as a subroutine, its action is limited to that group, even if
+the group does not contain any | characters. Note that such groups are
+processed as anchored at the point where they are tested.
</P>
<P>
10. If a pattern contains more than one backtracking control verb, the first
@@ -110,55 +116,56 @@ triggers (*PRUNE). Perl's behaviour is more complex; in many cases it is the
same as PCRE2, but there are cases where it differs.
</P>
<P>
-11. Most backtracking verbs in assertions have their normal actions. They are
-not confined to the assertion.
-</P>
-<P>
-12. There are some differences that are concerned with the settings of captured
+11. There are some differences that are concerned with the settings of captured
strings when part of a pattern is repeated. For example, matching "aba" against
the pattern /^(a(b)?)+$/ in Perl leaves $2 unset, but in PCRE2 it is set to
"b".
</P>
<P>
-13. PCRE2's handling of duplicate capture group numbers and names is not as
+12. PCRE2's handling of duplicate capture group numbers and names is not as
general as Perl's. This is a consequence of the fact the PCRE2 works internally
just with numbers, using an external table to translate between numbers and
-names. In particular, a pattern such as (?|(?&#60;a&#62;A)|(?&#60;b&#62;B), where the two
+names. In particular, a pattern such as (?|(?&#60;a&#62;A)|(?&#60;b&#62;B)), where the two
capture groups have the same number but different names, is not supported, and
causes an error at compile time. If it were allowed, it would not be possible
to distinguish which group matched, because both names map to capture group
number 1. To avoid this confusing situation, an error is given at compile time.
</P>
<P>
-14. Perl used to recognize comments in some places that PCRE2 does not, for
+13. Perl used to recognize comments in some places that PCRE2 does not, for
example, between the ( and ? at the start of a group. If the /x modifier is
set, Perl allowed white space between ( and ? though the latest Perls give an
error (for a while it was just deprecated). There may still be some cases where
Perl behaves differently.
</P>
<P>
-15. Perl, when in warning mode, gives warnings for character classes such as
+14. Perl, when in warning mode, gives warnings for character classes such as
[A-\d] or [a-[:digit:]]. It then treats the hyphens as literals. PCRE2 has no
warning features, so it gives an error in these cases because they are almost
certainly user mistakes.
</P>
<P>
-16. In PCRE2, the upper/lower case character properties Lu and Ll are not
+15. In PCRE2, the upper/lower case character properties Lu and Ll are not
affected when case-independent matching is specified. For example, \p{Lu}
always matches an upper case letter. I think Perl has changed in this respect;
-in the release at the time of writing (5.24), \p{Lu} and \p{Ll} match all
+in the release at the time of writing (5.32), \p{Lu} and \p{Ll} match all
letters, regardless of case, when case independence is specified.
</P>
<P>
+16. From release 5.32.0, Perl locks out the use of \K in lookaround
+assertions. In PCRE2, \K is acted on when it occurs in positive assertions,
+but is ignored in negative assertions.
+</P>
+<P>
17. PCRE2 provides some extensions to the Perl regular expression facilities.
-Perl 5.10 includes new features that are not in earlier versions of Perl, some
+Perl 5.10 included new features that were not in earlier versions of Perl, some
of which (such as named parentheses) were in PCRE2 for some time before. This
-list is with respect to Perl 5.26:
+list is with respect to Perl 5.32:
<br>
<br>
(a) Although lookbehind assertions in PCRE2 must match fixed length strings,
-each alternative branch of a lookbehind assertion can match a different length
-of string. Perl requires them all to have the same length.
+each alternative toplevel branch of a lookbehind assertion can match a
+different length of string. Perl requires them all to have the same length.
<br>
<br>
(b) From PCRE2 10.23, backreferences to groups of fixed length are supported
@@ -203,7 +210,7 @@ different way and is not Perl-compatible.
<br>
<br>
(l) PCRE2 recognizes some special sequences such as (*CR) or (*NO_JIT) at
-the start of a pattern that set overall options that cannot be changed within
+the start of a pattern. These set overall options that cannot be changed within
the pattern.
<br>
<br>
@@ -239,7 +246,7 @@ Cambridge, England.
REVISION
</b><br>
<P>
-Last updated: 13 July 2019
+Last updated: 06 October 2020
<br>
Copyright &copy; 1997-2019 University of Cambridge.
<br>
diff --git a/doc/html/pcre2pattern.html b/doc/html/pcre2pattern.html
index ec2e8c9..b2adf98 100644
--- a/doc/html/pcre2pattern.html
+++ b/doc/html/pcre2pattern.html
@@ -289,8 +289,11 @@ corresponding characters in the subject. As a trivial example, the pattern
The quick brown fox
</pre>
matches a portion of a subject string that is identical to itself. When
-caseless matching is specified (the PCRE2_CASELESS option), letters are matched
-independently of case.
+caseless matching is specified (the PCRE2_CASELESS option or (?i) within the
+pattern), letters are matched independently of case. Note that there are two
+ASCII characters, K and S, that, in addition to their lower case ASCII
+equivalents, are case-equivalent with Unicode U+212A (Kelvin sign) and U+017F
+(long S) respectively when either PCRE2_UTF or PCRE2_UCP is set.
</P>
<P>
The power of regular expressions comes from the ability to include wild cards,
@@ -326,6 +329,20 @@ a character class the only metacharacters are:
[ POSIX character class (if followed by POSIX syntax)
] terminates the character class
</pre>
+If a pattern is compiled with the PCRE2_EXTENDED option, most white space in
+the pattern, other than in a character class, and characters between a #
+outside a character class and the next newline, inclusive, are ignored. An
+escaping backslash can be used to include a white space or a # character as
+part of the pattern. If the PCRE2_EXTENDED_MORE option is set, the same
+applies, but in addition unescaped space and horizontal tab characters are
+ignored inside a character class. Note: only these two characters are ignored,
+not the full set of pattern white space characters that are ignored outside a
+character class. Option settings can be changed within a pattern; see the
+section entitled
+<a href="#internaloptions">"Internal Option Setting"</a>
+below.
+</P>
+<P>
The following sections describe the use of each of the metacharacters.
</P>
<br><a name="SEC5" href="#TOC1">BACKSLASH</a><br>
@@ -343,16 +360,9 @@ precede a non-alphanumeric with backslash to specify that it stands for itself.
In particular, if you want to match a backslash, you write \\.
</P>
<P>
-In a UTF mode, only ASCII digits and letters have any special meaning after a
-backslash. All other characters (in particular, those whose code points are
-greater than 127) are treated as literals.
-</P>
-<P>
-If a pattern is compiled with the PCRE2_EXTENDED option, most white space in
-the pattern (other than in a character class), and characters between a #
-outside a character class and the next newline, inclusive, are ignored. An
-escaping backslash can be used to include a white space or # character as part
-of the pattern.
+Only ASCII digits and letters have any special meaning after a backslash. All
+other characters (in particular, those whose code points are greater than 127)
+are treated as literals.
</P>
<P>
If you want to treat all characters in a sequence as literals, you can do so by
@@ -1165,8 +1175,9 @@ For example, when the pattern
matches "foobar", the first substring is still set to "foo".
</P>
<P>
-Perl documents that the use of \K within assertions is "not well defined". In
-PCRE2, \K is acted upon when it occurs inside positive assertions, but is
+Perl used to document that the use of \K within lookaround assertions is "not
+well defined", but from version 5.32.0 Perl does not support this usage at all.
+In PCRE2, \K is acted upon when it occurs inside positive assertions, but is
ignored in negative assertions. Note that when a pattern such as (?=ab\K)
matches, the reported start of the match can be greater than the end of the
match. Using \K in a lookbehind assertion at the start of a pattern can also
@@ -1443,7 +1454,10 @@ Characters in a class may be specified by their code points using \o, \x, or
\N{U+hh..} in the usual way. When caseless matching is set, any letters in a
class represent both their upper case and lower case versions, so for example,
a caseless [aeiou] matches "A" as well as "a", and a caseless [^aeiou] does not
-match "A", whereas a caseful version would.
+match "A", whereas a caseful version would. Note that there are two ASCII
+characters, K and S, that, in addition to their lower case ASCII equivalents,
+are case-equivalent with Unicode U+212A (Kelvin sign) and U+017F (long S)
+respectively when either PCRE2_UTF or PCRE2_UCP is set.
</P>
<P>
Characters that might indicate line breaks are never treated in any special way
@@ -3838,7 +3852,7 @@ Cambridge, England.
</P>
<br><a name="SEC32" href="#TOC1">REVISION</a><br>
<P>
-Last updated: 24 February 2020
+Last updated: 06 October 2020
<br>
Copyright &copy; 1997-2020 University of Cambridge.
<br>
diff --git a/doc/pcre2.txt b/doc/pcre2.txt
index 71fbc3c..0d8e5ac 100644
--- a/doc/pcre2.txt
+++ b/doc/pcre2.txt
@@ -1463,462 +1463,465 @@ COMPILING A PATTERN
it can be changed within a pattern by a (?i) option setting. If either
PCRE2_UTF or PCRE2_UCP is set, Unicode properties are used for all
characters with more than one other case, and for all characters whose
- code points are greater than U+007F. For lower valued characters with
- only one other case, a lookup table is used for speed. When neither
- PCRE2_UTF nor PCRE2_UCP is set, a lookup table is used for all code
- points less than 256, and higher code points (available only in 16-bit
- or 32-bit mode) are treated as not having another case.
+ code points are greater than U+007F. Note that there are two ASCII
+ characters, K and S, that, in addition to their lower case ASCII equiv-
+ alents, are case-equivalent with U+212A (Kelvin sign) and U+017F (long
+ S) respectively. For lower valued characters with only one other case,
+ a lookup table is used for speed. When neither PCRE2_UTF nor PCRE2_UCP
+ is set, a lookup table is used for all code points less than 256, and
+ higher code points (available only in 16-bit or 32-bit mode) are
+ treated as not having another case.
PCRE2_DOLLAR_ENDONLY
- If this bit is set, a dollar metacharacter in the pattern matches only
- at the end of the subject string. Without this option, a dollar also
- matches immediately before a newline at the end of the string (but not
- before any other newlines). The PCRE2_DOLLAR_ENDONLY option is ignored
- if PCRE2_MULTILINE is set. There is no equivalent to this option in
+ If this bit is set, a dollar metacharacter in the pattern matches only
+ at the end of the subject string. Without this option, a dollar also
+ matches immediately before a newline at the end of the string (but not
+ before any other newlines). The PCRE2_DOLLAR_ENDONLY option is ignored
+ if PCRE2_MULTILINE is set. There is no equivalent to this option in
Perl, and no way to set it within a pattern.
PCRE2_DOTALL
- If this bit is set, a dot metacharacter in the pattern matches any
- character, including one that indicates a newline. However, it only
+ If this bit is set, a dot metacharacter in the pattern matches any
+ character, including one that indicates a newline. However, it only
ever matches one character, even if newlines are coded as CRLF. Without
this option, a dot does not match when the current position in the sub-
- ject is at a newline. This option is equivalent to Perl's /s option,
+ ject is at a newline. This option is equivalent to Perl's /s option,
and it can be changed within a pattern by a (?s) option setting. A neg-
- ative class such as [^a] always matches newline characters, and the \N
- escape sequence always matches a non-newline character, independent of
+ ative class such as [^a] always matches newline characters, and the \N
+ escape sequence always matches a non-newline character, independent of
the setting of PCRE2_DOTALL.
PCRE2_DUPNAMES
- If this bit is set, names used to identify capture groups need not be
- unique. This can be helpful for certain types of pattern when it is
- known that only one instance of the named group can ever be matched.
- There are more details of named capture groups below; see also the
+ If this bit is set, names used to identify capture groups need not be
+ unique. This can be helpful for certain types of pattern when it is
+ known that only one instance of the named group can ever be matched.
+ There are more details of named capture groups below; see also the
pcre2pattern documentation.
PCRE2_ENDANCHORED
- If this bit is set, the end of any pattern match must be right at the
+ If this bit is set, the end of any pattern match must be right at the
end of the string being searched (the "subject string"). If the pattern
match succeeds by reaching (*ACCEPT), but does not reach the end of the
- subject, the match fails at the current starting point. For unanchored
- patterns, a new match is then tried at the next starting point. How-
+ subject, the match fails at the current starting point. For unanchored
+ patterns, a new match is then tried at the next starting point. How-
ever, if the match succeeds by reaching the end of the pattern, but not
- the end of the subject, backtracking occurs and an alternative match
+ the end of the subject, backtracking occurs and an alternative match
may be found. Consider these two patterns:
.(*ACCEPT)|..
.|..
- If matched against "abc" with PCRE2_ENDANCHORED set, the first matches
- "c" whereas the second matches "bc". The effect of PCRE2_ENDANCHORED
- can also be achieved by appropriate constructs in the pattern itself,
+ If matched against "abc" with PCRE2_ENDANCHORED set, the first matches
+ "c" whereas the second matches "bc". The effect of PCRE2_ENDANCHORED
+ can also be achieved by appropriate constructs in the pattern itself,
which is the only way to do it in Perl.
For DFA matching with pcre2_dfa_match(), PCRE2_ENDANCHORED applies only
- to the first (that is, the longest) matched string. Other parallel
- matches, which are necessarily substrings of the first one, must obvi-
+ to the first (that is, the longest) matched string. Other parallel
+ matches, which are necessarily substrings of the first one, must obvi-
ously end before the end of the subject.
PCRE2_EXTENDED
- If this bit is set, most white space characters in the pattern are to-
+ If this bit is set, most white space characters in the pattern are to-
tally ignored except when escaped or inside a character class. However,
- white space is not allowed within sequences such as (?> that introduce
- various parenthesized groups, nor within numerical quantifiers such as
+ white space is not allowed within sequences such as (?> that introduce
+ various parenthesized groups, nor within numerical quantifiers such as
{1,3}. Ignorable white space is permitted between an item and a follow-
- ing quantifier and between a quantifier and a following + that indi-
+ ing quantifier and between a quantifier and a following + that indi-
cates possessiveness. PCRE2_EXTENDED is equivalent to Perl's /x option,
and it can be changed within a pattern by a (?x) option setting.
- When PCRE2 is compiled without Unicode support, PCRE2_EXTENDED recog-
- nizes as white space only those characters with code points less than
+ When PCRE2 is compiled without Unicode support, PCRE2_EXTENDED recog-
+ nizes as white space only those characters with code points less than
256 that are flagged as white space in its low-character table. The ta-
ble is normally created by pcre2_maketables(), which uses the isspace()
- function to identify space characters. In most ASCII environments, the
- relevant characters are those with code points 0x0009 (tab), 0x000A
- (linefeed), 0x000B (vertical tab), 0x000C (formfeed), 0x000D (carriage
+ function to identify space characters. In most ASCII environments, the
+ relevant characters are those with code points 0x0009 (tab), 0x000A
+ (linefeed), 0x000B (vertical tab), 0x000C (formfeed), 0x000D (carriage
return), and 0x0020 (space).
When PCRE2 is compiled with Unicode support, in addition to these char-
- acters, five more Unicode "Pattern White Space" characters are recog-
+ acters, five more Unicode "Pattern White Space" characters are recog-
nized by PCRE2_EXTENDED. These are U+0085 (next line), U+200E (left-to-
- right mark), U+200F (right-to-left mark), U+2028 (line separator), and
- U+2029 (paragraph separator). This set of characters is the same as
- recognized by Perl's /x option. Note that the horizontal and vertical
- space characters that are matched by the \h and \v escapes in patterns
+ right mark), U+200F (right-to-left mark), U+2028 (line separator), and
+ U+2029 (paragraph separator). This set of characters is the same as
+ recognized by Perl's /x option. Note that the horizontal and vertical
+ space characters that are matched by the \h and \v escapes in patterns
are a much bigger set.
- As well as ignoring most white space, PCRE2_EXTENDED also causes char-
- acters between an unescaped # outside a character class and the next
- newline, inclusive, to be ignored, which makes it possible to include
+ As well as ignoring most white space, PCRE2_EXTENDED also causes char-
+ acters between an unescaped # outside a character class and the next
+ newline, inclusive, to be ignored, which makes it possible to include
comments inside complicated patterns. Note that the end of this type of
- comment is a literal newline sequence in the pattern; escape sequences
+ comment is a literal newline sequence in the pattern; escape sequences
that happen to represent a newline do not count.
Which characters are interpreted as newlines can be specified by a set-
- ting in the compile context that is passed to pcre2_compile() or by a
- special sequence at the start of the pattern, as described in the sec-
- tion entitled "Newline conventions" in the pcre2pattern documentation.
+ ting in the compile context that is passed to pcre2_compile() or by a
+ special sequence at the start of the pattern, as described in the sec-
+ tion entitled "Newline conventions" in the pcre2pattern documentation.
A default is defined when PCRE2 is built.
PCRE2_EXTENDED_MORE
- This option has the effect of PCRE2_EXTENDED, but, in addition, un-
- escaped space and horizontal tab characters are ignored inside a char-
- acter class. Note: only these two characters are ignored, not the full
- set of pattern white space characters that are ignored outside a char-
- acter class. PCRE2_EXTENDED_MORE is equivalent to Perl's /xx option,
+ This option has the effect of PCRE2_EXTENDED, but, in addition, un-
+ escaped space and horizontal tab characters are ignored inside a char-
+ acter class. Note: only these two characters are ignored, not the full
+ set of pattern white space characters that are ignored outside a char-
+ acter class. PCRE2_EXTENDED_MORE is equivalent to Perl's /xx option,
and it can be changed within a pattern by a (?xx) option setting.
PCRE2_FIRSTLINE
If this option is set, the start of an unanchored pattern match must be
- before or at the first newline in the subject string following the
- start of matching, though the matched text may continue over the new-
+ before or at the first newline in the subject string following the
+ start of matching, though the matched text may continue over the new-
line. If startoffset is non-zero, the limiting newline is not necessar-
- ily the first newline in the subject. For example, if the subject
+ ily the first newline in the subject. For example, if the subject
string is "abc\nxyz" (where \n represents a single-character newline) a
- pattern match for "yz" succeeds with PCRE2_FIRSTLINE if startoffset is
- greater than 3. See also PCRE2_USE_OFFSET_LIMIT, which provides a more
- general limiting facility. If PCRE2_FIRSTLINE is set with an offset
- limit, a match must occur in the first line and also within the offset
+ pattern match for "yz" succeeds with PCRE2_FIRSTLINE if startoffset is
+ greater than 3. See also PCRE2_USE_OFFSET_LIMIT, which provides a more
+ general limiting facility. If PCRE2_FIRSTLINE is set with an offset
+ limit, a match must occur in the first line and also within the offset
limit. In other words, whichever limit comes first is used.
PCRE2_LITERAL
If this option is set, all meta-characters in the pattern are disabled,
- and it is treated as a literal string. Matching literal strings with a
+ and it is treated as a literal string. Matching literal strings with a
regular expression engine is not the most efficient way of doing it. If
- you are doing a lot of literal matching and are worried about effi-
+ you are doing a lot of literal matching and are worried about effi-
ciency, you should consider using other approaches. The only other main
options that are allowed with PCRE2_LITERAL are: PCRE2_ANCHORED,
PCRE2_ENDANCHORED, PCRE2_AUTO_CALLOUT, PCRE2_CASELESS, PCRE2_FIRSTLINE,
PCRE2_MATCH_INVALID_UTF, PCRE2_NO_START_OPTIMIZE, PCRE2_NO_UTF_CHECK,
- PCRE2_UTF, and PCRE2_USE_OFFSET_LIMIT. The extra options PCRE2_EX-
+ PCRE2_UTF, and PCRE2_USE_OFFSET_LIMIT. The extra options PCRE2_EX-
TRA_MATCH_LINE and PCRE2_EXTRA_MATCH_WORD are also supported. Any other
options cause an error.
PCRE2_MATCH_INVALID_UTF
- This option forces PCRE2_UTF (see below) and also enables support for
- matching by pcre2_match() in subject strings that contain invalid UTF
- sequences. This facility is not supported for DFA matching. For de-
+ This option forces PCRE2_UTF (see below) and also enables support for
+ matching by pcre2_match() in subject strings that contain invalid UTF
+ sequences. This facility is not supported for DFA matching. For de-
tails, see the pcre2unicode documentation.
PCRE2_MATCH_UNSET_BACKREF
- If this option is set, a backreference to an unset capture group
- matches an empty string (by default this causes the current matching
+ If this option is set, a backreference to an unset capture group
+ matches an empty string (by default this causes the current matching
alternative to fail). A pattern such as (\1)(a) succeeds when this op-
- tion is set (assuming it can find an "a" in the subject), whereas it
- fails by default, for Perl compatibility. Setting this option makes
+ tion is set (assuming it can find an "a" in the subject), whereas it
+ fails by default, for Perl compatibility. Setting this option makes
PCRE2 behave more like ECMAscript (aka JavaScript).
PCRE2_MULTILINE
- By default, for the purposes of matching "start of line" and "end of
- line", PCRE2 treats the subject string as consisting of a single line
- of characters, even if it actually contains newlines. The "start of
- line" metacharacter (^) matches only at the start of the string, and
- the "end of line" metacharacter ($) matches only at the end of the
- string, or before a terminating newline (except when PCRE2_DOLLAR_EN-
+ By default, for the purposes of matching "start of line" and "end of
+ line", PCRE2 treats the subject string as consisting of a single line
+ of characters, even if it actually contains newlines. The "start of
+ line" metacharacter (^) matches only at the start of the string, and
+ the "end of line" metacharacter ($) matches only at the end of the
+ string, or before a terminating newline (except when PCRE2_DOLLAR_EN-
DONLY is set). Note, however, that unless PCRE2_DOTALL is set, the "any
- character" metacharacter (.) does not match at a newline. This behav-
+ character" metacharacter (.) does not match at a newline. This behav-
iour (for ^, $, and dot) is the same as Perl.
- When PCRE2_MULTILINE it is set, the "start of line" and "end of line"
- constructs match immediately following or immediately before internal
- newlines in the subject string, respectively, as well as at the very
- start and end. This is equivalent to Perl's /m option, and it can be
+ When PCRE2_MULTILINE it is set, the "start of line" and "end of line"
+ constructs match immediately following or immediately before internal
+ newlines in the subject string, respectively, as well as at the very
+ start and end. This is equivalent to Perl's /m option, and it can be
changed within a pattern by a (?m) option setting. Note that the "start
of line" metacharacter does not match after a newline at the end of the
- subject, for compatibility with Perl. However, you can change this by
- setting the PCRE2_ALT_CIRCUMFLEX option. If there are no newlines in a
- subject string, or no occurrences of ^ or $ in a pattern, setting
+ subject, for compatibility with Perl. However, you can change this by
+ setting the PCRE2_ALT_CIRCUMFLEX option. If there are no newlines in a
+ subject string, or no occurrences of ^ or $ in a pattern, setting
PCRE2_MULTILINE has no effect.
PCRE2_NEVER_BACKSLASH_C
- This option locks out the use of \C in the pattern that is being com-
- piled. This escape can cause unpredictable behaviour in UTF-8 or
- UTF-16 modes, because it may leave the current matching point in the
+ This option locks out the use of \C in the pattern that is being com-
+ piled. This escape can cause unpredictable behaviour in UTF-8 or
+ UTF-16 modes, because it may leave the current matching point in the
middle of a multi-code-unit character. This option may be useful in ap-
plications that process patterns from external sources. Note that there
is also a build-time option that permanently locks out the use of \C.
PCRE2_NEVER_UCP
- This option locks out the use of Unicode properties for handling \B,
+ This option locks out the use of Unicode properties for handling \B,
\b, \D, \d, \S, \s, \W, \w, and some of the POSIX character classes, as
- described for the PCRE2_UCP option below. In particular, it prevents
- the creator of the pattern from enabling this facility by starting the
- pattern with (*UCP). This option may be useful in applications that
+ described for the PCRE2_UCP option below. In particular, it prevents
+ the creator of the pattern from enabling this facility by starting the
+ pattern with (*UCP). This option may be useful in applications that
process patterns from external sources. The option combination PCRE_UCP
and PCRE_NEVER_UCP causes an error.
PCRE2_NEVER_UTF
- This option locks out interpretation of the pattern as UTF-8, UTF-16,
+ This option locks out interpretation of the pattern as UTF-8, UTF-16,
or UTF-32, depending on which library is in use. In particular, it pre-
- vents the creator of the pattern from switching to UTF interpretation
- by starting the pattern with (*UTF). This option may be useful in ap-
+ vents the creator of the pattern from switching to UTF interpretation
+ by starting the pattern with (*UTF). This option may be useful in ap-
plications that process patterns from external sources. The combination
of PCRE2_UTF and PCRE2_NEVER_UTF causes an error.
PCRE2_NO_AUTO_CAPTURE
If this option is set, it disables the use of numbered capturing paren-
- theses in the pattern. Any opening parenthesis that is not followed by
- ? behaves as if it were followed by ?: but named parentheses can still
+ theses in the pattern. Any opening parenthesis that is not followed by
+ ? behaves as if it were followed by ?: but named parentheses can still
be used for capturing (and they acquire numbers in the usual way). This
- is the same as Perl's /n option. Note that, when this option is set,
- references to capture groups (backreferences or recursion/subroutine
- calls) may only refer to named groups, though the reference can be by
+ is the same as Perl's /n option. Note that, when this option is set,
+ references to capture groups (backreferences or recursion/subroutine
+ calls) may only refer to named groups, though the reference can be by
name or by number.
PCRE2_NO_AUTO_POSSESS
If this option is set, it disables "auto-possessification", which is an
- optimization that, for example, turns a+b into a++b in order to avoid
- backtracks into a+ that can never be successful. However, if callouts
- are in use, auto-possessification means that some callouts are never
+ optimization that, for example, turns a+b into a++b in order to avoid
+ backtracks into a+ that can never be successful. However, if callouts
+ are in use, auto-possessification means that some callouts are never
taken. You can set this option if you want the matching functions to do
- a full unoptimized search and run all the callouts, but it is mainly
+ a full unoptimized search and run all the callouts, but it is mainly
provided for testing purposes.
PCRE2_NO_DOTSTAR_ANCHOR
If this option is set, it disables an optimization that is applied when
- .* is the first significant item in a top-level branch of a pattern,
- and all the other branches also start with .* or with \A or \G or ^.
- The optimization is automatically disabled for .* if it is inside an
+ .* is the first significant item in a top-level branch of a pattern,
+ and all the other branches also start with .* or with \A or \G or ^.
+ The optimization is automatically disabled for .* if it is inside an
atomic group or a capture group that is the subject of a backreference,
- or if the pattern contains (*PRUNE) or (*SKIP). When the optimization
- is not disabled, such a pattern is automatically anchored if
+ or if the pattern contains (*PRUNE) or (*SKIP). When the optimization
+ is not disabled, such a pattern is automatically anchored if
PCRE2_DOTALL is set for all the .* items and PCRE2_MULTILINE is not set
- for any ^ items. Otherwise, the fact that any match must start either
- at the start of the subject or following a newline is remembered. Like
+ for any ^ items. Otherwise, the fact that any match must start either
+ at the start of the subject or following a newline is remembered. Like
other optimizations, this can cause callouts to be skipped.
PCRE2_NO_START_OPTIMIZE
- This is an option whose main effect is at matching time. It does not
+ This is an option whose main effect is at matching time. It does not
change what pcre2_compile() generates, but it does affect the output of
the JIT compiler.
- There are a number of optimizations that may occur at the start of a
- match, in order to speed up the process. For example, if it is known
- that an unanchored match must start with a specific code unit value,
- the matching code searches the subject for that value, and fails imme-
- diately if it cannot find it, without actually running the main match-
- ing function. This means that a special item such as (*COMMIT) at the
- start of a pattern is not considered until after a suitable starting
- point for the match has been found. Also, when callouts or (*MARK)
- items are in use, these "start-up" optimizations can cause them to be
- skipped if the pattern is never actually used. The start-up optimiza-
- tions are in effect a pre-scan of the subject that takes place before
+ There are a number of optimizations that may occur at the start of a
+ match, in order to speed up the process. For example, if it is known
+ that an unanchored match must start with a specific code unit value,
+ the matching code searches the subject for that value, and fails imme-
+ diately if it cannot find it, without actually running the main match-
+ ing function. This means that a special item such as (*COMMIT) at the
+ start of a pattern is not considered until after a suitable starting
+ point for the match has been found. Also, when callouts or (*MARK)
+ items are in use, these "start-up" optimizations can cause them to be
+ skipped if the pattern is never actually used. The start-up optimiza-
+ tions are in effect a pre-scan of the subject that takes place before
the pattern is run.
The PCRE2_NO_START_OPTIMIZE option disables the start-up optimizations,
- possibly causing performance to suffer, but ensuring that in cases
- where the result is "no match", the callouts do occur, and that items
+ possibly causing performance to suffer, but ensuring that in cases
+ where the result is "no match", the callouts do occur, and that items
such as (*COMMIT) and (*MARK) are considered at every possible starting
position in the subject string.
- Setting PCRE2_NO_START_OPTIMIZE may change the outcome of a matching
+ Setting PCRE2_NO_START_OPTIMIZE may change the outcome of a matching
operation. Consider the pattern
(*COMMIT)ABC
- When this is compiled, PCRE2 records the fact that a match must start
- with the character "A". Suppose the subject string is "DEFABC". The
- start-up optimization scans along the subject, finds "A" and runs the
- first match attempt from there. The (*COMMIT) item means that the pat-
- tern must match the current starting position, which in this case, it
- does. However, if the same match is run with PCRE2_NO_START_OPTIMIZE
- set, the initial scan along the subject string does not happen. The
- first match attempt is run starting from "D" and when this fails,
- (*COMMIT) prevents any further matches being tried, so the overall re-
+ When this is compiled, PCRE2 records the fact that a match must start
+ with the character "A". Suppose the subject string is "DEFABC". The
+ start-up optimization scans along the subject, finds "A" and runs the
+ first match attempt from there. The (*COMMIT) item means that the pat-
+ tern must match the current starting position, which in this case, it
+ does. However, if the same match is run with PCRE2_NO_START_OPTIMIZE
+ set, the initial scan along the subject string does not happen. The
+ first match attempt is run starting from "D" and when this fails,
+ (*COMMIT) prevents any further matches being tried, so the overall re-
sult is "no match".
- As another start-up optimization makes use of a minimum length for a
+ As another start-up optimization makes use of a minimum length for a
matching subject, which is recorded when possible. Consider the pattern
(*MARK:1)B(*MARK:2)(X|Y)
- The minimum length for a match is two characters. If the subject is
+ The minimum length for a match is two characters. If the subject is
"XXBB", the "starting character" optimization skips "XX", then tries to
- match "BB", which is long enough. In the process, (*MARK:2) is encoun-
- tered and remembered. When the match attempt fails, the next "B" is
- found, but there is only one character left, so there are no more at-
- tempts, and "no match" is returned with the "last mark seen" set to
- "2". If NO_START_OPTIMIZE is set, however, matches are tried at every
- possible starting position, including at the end of the subject, where
- (*MARK:1) is encountered, but there is no "B", so the "last mark seen"
- that is returned is "1". In this case, the optimizations do not affect
+ match "BB", which is long enough. In the process, (*MARK:2) is encoun-
+ tered and remembered. When the match attempt fails, the next "B" is
+ found, but there is only one character left, so there are no more at-
+ tempts, and "no match" is returned with the "last mark seen" set to
+ "2". If NO_START_OPTIMIZE is set, however, matches are tried at every
+ possible starting position, including at the end of the subject, where
+ (*MARK:1) is encountered, but there is no "B", so the "last mark seen"
+ that is returned is "1". In this case, the optimizations do not affect
the overall match result, which is still "no match", but they do affect
the auxiliary information that is returned.
PCRE2_NO_UTF_CHECK
- When PCRE2_UTF is set, the validity of the pattern as a UTF string is
- automatically checked. There are discussions about the validity of
- UTF-8 strings, UTF-16 strings, and UTF-32 strings in the pcre2unicode
- document. If an invalid UTF sequence is found, pcre2_compile() returns
+ When PCRE2_UTF is set, the validity of the pattern as a UTF string is
+ automatically checked. There are discussions about the validity of
+ UTF-8 strings, UTF-16 strings, and UTF-32 strings in the pcre2unicode
+ document. If an invalid UTF sequence is found, pcre2_compile() returns
a negative error code.
- If you know that your pattern is a valid UTF string, and you want to
- skip this check for performance reasons, you can set the
+ If you know that your pattern is a valid UTF string, and you want to
+ skip this check for performance reasons, you can set the
PCRE2_NO_UTF_CHECK option. When it is set, the effect of passing an in-
- valid UTF string as a pattern is undefined. It may cause your program
+ valid UTF string as a pattern is undefined. It may cause your program
to crash or loop.
Note that this option can also be passed to pcre2_match() and
- pcre_dfa_match(), to suppress UTF validity checking of the subject
+ pcre_dfa_match(), to suppress UTF validity checking of the subject
string.
Note also that setting PCRE2_NO_UTF_CHECK at compile time does not dis-
- able the error that is given if an escape sequence for an invalid Uni-
- code code point is encountered in the pattern. In particular, the so-
- called "surrogate" code points (0xd800 to 0xdfff) are invalid. If you
- want to allow escape sequences such as \x{d800} you can set the
- PCRE2_EXTRA_ALLOW_SURROGATE_ESCAPES extra option, as described in the
- section entitled "Extra compile options" below. However, this is pos-
+ able the error that is given if an escape sequence for an invalid Uni-
+ code code point is encountered in the pattern. In particular, the so-
+ called "surrogate" code points (0xd800 to 0xdfff) are invalid. If you
+ want to allow escape sequences such as \x{d800} you can set the
+ PCRE2_EXTRA_ALLOW_SURROGATE_ESCAPES extra option, as described in the
+ section entitled "Extra compile options" below. However, this is pos-
sible only in UTF-8 and UTF-32 modes, because these values are not rep-
resentable in UTF-16.
PCRE2_UCP
This option has two effects. Firstly, it change the way PCRE2 processes
- \B, \b, \D, \d, \S, \s, \W, \w, and some of the POSIX character
- classes. By default, only ASCII characters are recognized, but if
+ \B, \b, \D, \d, \S, \s, \W, \w, and some of the POSIX character
+ classes. By default, only ASCII characters are recognized, but if
PCRE2_UCP is set, Unicode properties are used instead to classify char-
- acters. More details are given in the section on generic character
- types in the pcre2pattern page. If you set PCRE2_UCP, matching one of
+ acters. More details are given in the section on generic character
+ types in the pcre2pattern page. If you set PCRE2_UCP, matching one of
the items it affects takes much longer.
- The second effect of PCRE2_UCP is to force the use of Unicode proper-
- ties for upper/lower casing operations on characters with code points
- greater than 127, even when PCRE2_UTF is not set. This makes it possi-
+ The second effect of PCRE2_UCP is to force the use of Unicode proper-
+ ties for upper/lower casing operations on characters with code points
+ greater than 127, even when PCRE2_UTF is not set. This makes it possi-
ble, for example, to process strings in the 16-bit UCS-2 code. This op-
- tion is available only if PCRE2 has been compiled with Unicode support
+ tion is available only if PCRE2 has been compiled with Unicode support
(which is the default).
PCRE2_UNGREEDY
- This option inverts the "greediness" of the quantifiers so that they
- are not greedy by default, but become greedy if followed by "?". It is
- not compatible with Perl. It can also be set by a (?U) option setting
+ This option inverts the "greediness" of the quantifiers so that they
+ are not greedy by default, but become greedy if followed by "?". It is
+ not compatible with Perl. It can also be set by a (?U) option setting
within the pattern.
PCRE2_USE_OFFSET_LIMIT
This option must be set for pcre2_compile() if pcre2_set_offset_limit()
- is going to be used to set a non-default offset limit in a match con-
- text for matches that use this pattern. An error is generated if an
- offset limit is set without this option. For more details, see the de-
- scription of pcre2_set_offset_limit() in the section that describes
+ is going to be used to set a non-default offset limit in a match con-
+ text for matches that use this pattern. An error is generated if an
+ offset limit is set without this option. For more details, see the de-
+ scription of pcre2_set_offset_limit() in the section that describes
match contexts. See also the PCRE2_FIRSTLINE option above.
PCRE2_UTF
- This option causes PCRE2 to regard both the pattern and the subject
- strings that are subsequently processed as strings of UTF characters
- instead of single-code-unit strings. It is available when PCRE2 is
- built to include Unicode support (which is the default). If Unicode
+ This option causes PCRE2 to regard both the pattern and the subject
+ strings that are subsequently processed as strings of UTF characters
+ instead of single-code-unit strings. It is available when PCRE2 is
+ built to include Unicode support (which is the default). If Unicode
support is not available, the use of this option provokes an error. De-
- tails of how PCRE2_UTF changes the behaviour of PCRE2 are given in the
+ tails of how PCRE2_UTF changes the behaviour of PCRE2 are given in the
pcre2unicode page. In particular, note that it changes the way
PCRE2_CASELESS handles characters with code points greater than 127.
Extra compile options
- The option bits that can be set in a compile context by calling the
+ The option bits that can be set in a compile context by calling the
pcre2_set_compile_extra_options() function are as follows:
PCRE2_EXTRA_ALLOW_SURROGATE_ESCAPES
- This option applies when compiling a pattern in UTF-8 or UTF-32 mode.
- It is forbidden in UTF-16 mode, and ignored in non-UTF modes. Unicode
+ This option applies when compiling a pattern in UTF-8 or UTF-32 mode.
+ It is forbidden in UTF-16 mode, and ignored in non-UTF modes. Unicode
"surrogate" code points in the range 0xd800 to 0xdfff are used in pairs
- in UTF-16 to encode code points with values in the range 0x10000 to
- 0x10ffff. The surrogates cannot therefore be represented in UTF-16.
+ in UTF-16 to encode code points with values in the range 0x10000 to
+ 0x10ffff. The surrogates cannot therefore be represented in UTF-16.
They can be represented in UTF-8 and UTF-32, but are defined as invalid
- code points, and cause errors if encountered in a UTF-8 or UTF-32
+ code points, and cause errors if encountered in a UTF-8 or UTF-32
string that is being checked for validity by PCRE2.
- These values also cause errors if encountered in escape sequences such
+ These values also cause errors if encountered in escape sequences such
as \x{d912} within a pattern. However, it seems that some applications,
when using PCRE2 to check for unwanted characters in UTF-8 strings, ex-
- plicitly test for the surrogates using escape sequences. The
- PCRE2_NO_UTF_CHECK option does not disable the error that occurs, be-
+ plicitly test for the surrogates using escape sequences. The
+ PCRE2_NO_UTF_CHECK option does not disable the error that occurs, be-
cause it applies only to the testing of input strings for UTF validity.
- If the extra option PCRE2_EXTRA_ALLOW_SURROGATE_ESCAPES is set, surro-
- gate code point values in UTF-8 and UTF-32 patterns no longer provoke
- errors and are incorporated in the compiled pattern. However, they can
- only match subject characters if the matching function is called with
+ If the extra option PCRE2_EXTRA_ALLOW_SURROGATE_ESCAPES is set, surro-
+ gate code point values in UTF-8 and UTF-32 patterns no longer provoke
+ errors and are incorporated in the compiled pattern. However, they can
+ only match subject characters if the matching function is called with
PCRE2_NO_UTF_CHECK set.
PCRE2_EXTRA_ALT_BSUX
- The original option PCRE2_ALT_BSUX causes PCRE2 to process \U, \u, and
- \x in the way that ECMAscript (aka JavaScript) does. Additional func-
+ The original option PCRE2_ALT_BSUX causes PCRE2 to process \U, \u, and
+ \x in the way that ECMAscript (aka JavaScript) does. Additional func-
tionality was defined by ECMAscript 6; setting PCRE2_EXTRA_ALT_BSUX has
- the effect of PCRE2_ALT_BSUX, but in addition it recognizes \u{hhh..}
+ the effect of PCRE2_ALT_BSUX, but in addition it recognizes \u{hhh..}
as a hexadecimal character code, where hhh.. is any number of hexadeci-
mal digits.
PCRE2_EXTRA_BAD_ESCAPE_IS_LITERAL
- This is a dangerous option. Use with care. By default, an unrecognized
- escape such as \j or a malformed one such as \x{2z} causes a compile-
+ This is a dangerous option. Use with care. By default, an unrecognized
+ escape such as \j or a malformed one such as \x{2z} causes a compile-
time error when detected by pcre2_compile(). Perl is somewhat inconsis-
- tent in handling such items: for example, \j is treated as a literal
- "j", and non-hexadecimal digits in \x{} are just ignored, though warn-
- ings are given in both cases if Perl's warning switch is enabled. How-
- ever, a malformed octal number after \o{ always causes an error in
+ tent in handling such items: for example, \j is treated as a literal
+ "j", and non-hexadecimal digits in \x{} are just ignored, though warn-
+ ings are given in both cases if Perl's warning switch is enabled. How-
+ ever, a malformed octal number after \o{ always causes an error in
Perl.
- If the PCRE2_EXTRA_BAD_ESCAPE_IS_LITERAL extra option is passed to
- pcre2_compile(), all unrecognized or malformed escape sequences are
- treated as single-character escapes. For example, \j is a literal "j"
- and \x{2z} is treated as the literal string "x{2z}". Setting this op-
+ If the PCRE2_EXTRA_BAD_ESCAPE_IS_LITERAL extra option is passed to
+ pcre2_compile(), all unrecognized or malformed escape sequences are
+ treated as single-character escapes. For example, \j is a literal "j"
+ and \x{2z} is treated as the literal string "x{2z}". Setting this op-
tion means that typos in patterns may go undetected and have unexpected
- results. Also note that a sequence such as [\N{] is interpreted as a
- malformed attempt at [\N{...}] and so is treated as [N{] whereas [\N]
+ results. Also note that a sequence such as [\N{] is interpreted as a
+ malformed attempt at [\N{...}] and so is treated as [N{] whereas [\N]
gives an error because an unqualified \N is a valid escape sequence but
- is not supported in a character class. To reiterate: this is a danger-
+ is not supported in a character class. To reiterate: this is a danger-
ous option. Use with great care.
PCRE2_EXTRA_ESCAPED_CR_IS_LF
- There are some legacy applications where the escape sequence \r in a
- pattern is expected to match a newline. If this option is set, \r in a
- pattern is converted to \n so that it matches a LF (linefeed) instead
- of a CR (carriage return) character. The option does not affect a lit-
- eral CR in the pattern, nor does it affect CR specified as an explicit
+ There are some legacy applications where the escape sequence \r in a
+ pattern is expected to match a newline. If this option is set, \r in a
+ pattern is converted to \n so that it matches a LF (linefeed) instead
+ of a CR (carriage return) character. The option does not affect a lit-
+ eral CR in the pattern, nor does it affect CR specified as an explicit
code point such as \x{0D}.
PCRE2_EXTRA_MATCH_LINE
- This option is provided for use by the -x option of pcre2grep. It
- causes the pattern only to match complete lines. This is achieved by
- automatically inserting the code for "^(?:" at the start of the com-
- piled pattern and ")$" at the end. Thus, when PCRE2_MULTILINE is set,
- the matched line may be in the middle of the subject string. This op-
+ This option is provided for use by the -x option of pcre2grep. It
+ causes the pattern only to match complete lines. This is achieved by
+ automatically inserting the code for "^(?:" at the start of the com-
+ piled pattern and ")$" at the end. Thus, when PCRE2_MULTILINE is set,
+ the matched line may be in the middle of the subject string. This op-
tion can be used with PCRE2_LITERAL.
PCRE2_EXTRA_MATCH_WORD
- This option is provided for use by the -w option of pcre2grep. It
- causes the pattern only to match strings that have a word boundary at
- the start and the end. This is achieved by automatically inserting the
- code for "\b(?:" at the start of the compiled pattern and ")\b" at the
- end. The option may be used with PCRE2_LITERAL. However, it is ignored
+ This option is provided for use by the -w option of pcre2grep. It
+ causes the pattern only to match strings that have a word boundary at
+ the start and the end. This is achieved by automatically inserting the
+ code for "\b(?:" at the start of the compiled pattern and ")\b" at the
+ end. The option may be used with PCRE2_LITERAL. However, it is ignored
if PCRE2_EXTRA_MATCH_LINE is also set.
@@ -1941,16 +1944,16 @@ JUST-IN-TIME (JIT) COMPILATION
void pcre2_jit_stack_free(pcre2_jit_stack *jit_stack);
- These functions provide support for JIT compilation, which, if the
- just-in-time compiler is available, further processes a compiled pat-
+ These functions provide support for JIT compilation, which, if the
+ just-in-time compiler is available, further processes a compiled pat-
tern into machine code that executes much faster than the pcre2_match()
- interpretive matching function. Full details are given in the pcre2jit
+ interpretive matching function. Full details are given in the pcre2jit
documentation.
- JIT compilation is a heavyweight optimization. It can take some time
- for patterns to be analyzed, and for one-off matches and simple pat-
- terns the benefit of faster execution might be offset by a much slower
- compilation time. Most (but not all) patterns can be optimized by the
+ JIT compilation is a heavyweight optimization. It can take some time
+ for patterns to be analyzed, and for one-off matches and simple pat-
+ terns the benefit of faster execution might be offset by a much slower
+ compilation time. Most (but not all) patterns can be optimized by the
JIT compiler.
@@ -1961,46 +1964,46 @@ LOCALE SUPPORT
void pcre2_maketables_free(pcre2_general_context *gcontext,
const uint8_t *tables);
- PCRE2 handles caseless matching, and determines whether characters are
- letters, digits, or whatever, by reference to a set of tables, indexed
+ PCRE2 handles caseless matching, and determines whether characters are
+ letters, digits, or whatever, by reference to a set of tables, indexed
by character code point. However, this applies only to characters whose
- code points are less than 256. By default, higher-valued code points
+ code points are less than 256. By default, higher-valued code points
never match escapes such as \w or \d.
- When PCRE2 is built with Unicode support (the default), the Unicode
+ When PCRE2 is built with Unicode support (the default), the Unicode
properties of all characters can be tested with \p and \P, or, alterna-
- tively, the PCRE2_UCP option can be set when a pattern is compiled;
- this causes \w and friends to use Unicode property support instead of
- the built-in tables. PCRE2_UCP also causes upper/lower casing opera-
- tions on characters with code points greater than 127 to use Unicode
+ tively, the PCRE2_UCP option can be set when a pattern is compiled;
+ this causes \w and friends to use Unicode property support instead of
+ the built-in tables. PCRE2_UCP also causes upper/lower casing opera-
+ tions on characters with code points greater than 127 to use Unicode
properties. These effects apply even when PCRE2_UTF is not set.
- The use of locales with Unicode is discouraged. If you are handling
- characters with code points greater than 127, you should either use
+ The use of locales with Unicode is discouraged. If you are handling
+ characters with code points greater than 127, you should either use
Unicode support, or use locales, but not try to mix the two.
- PCRE2 contains a built-in set of character tables that are used by de-
- fault. These are sufficient for many applications. Normally, the in-
- ternal tables recognize only ASCII characters. However, when PCRE2 is
+ PCRE2 contains a built-in set of character tables that are used by de-
+ fault. These are sufficient for many applications. Normally, the in-
+ ternal tables recognize only ASCII characters. However, when PCRE2 is
built, it is possible to cause the internal tables to be rebuilt in the
default "C" locale of the local system, which may cause them to be dif-
ferent.
- The built-in tables can be overridden by tables supplied by the appli-
- cation that calls PCRE2. These may be created in a different locale
- from the default. As more and more applications change to using Uni-
+ The built-in tables can be overridden by tables supplied by the appli-
+ cation that calls PCRE2. These may be created in a different locale
+ from the default. As more and more applications change to using Uni-
code, the need for this locale support is expected to die away.
- External tables are built by calling the pcre2_maketables() function,
+ External tables are built by calling the pcre2_maketables() function,
in the relevant locale. The only argument to this function is a general
- context, which can be used to pass a custom memory allocator. If the
+ context, which can be used to pass a custom memory allocator. If the
argument is NULL, the system malloc() is used. The result can be passed
to pcre2_compile() as often as necessary, by creating a compile context
- and calling pcre2_set_character_tables() to set the tables pointer
+ and calling pcre2_set_character_tables() to set the tables pointer
therein.
- For example, to build and use tables that are appropriate for the
- French locale (where accented characters with values greater than 127
+ For example, to build and use tables that are appropriate for the
+ French locale (where accented characters with values greater than 127
are treated as letters), the following code could be used:
setlocale(LC_CTYPE, "fr_FR");
@@ -2009,31 +2012,31 @@ LOCALE SUPPORT
pcre2_set_character_tables(ccontext, tables);
re = pcre2_compile(..., ccontext);
- The locale name "fr_FR" is used on Linux and other Unix-like systems;
+ The locale name "fr_FR" is used on Linux and other Unix-like systems;
if you are using Windows, the name for the French locale is "french".
The pointer that is passed (via the compile context) to pcre2_compile()
is saved with the compiled pattern, and the same tables are used by the
- matching functions. Thus, for any single pattern, compilation and
- matching both happen in the same locale, but different patterns can be
+ matching functions. Thus, for any single pattern, compilation and
+ matching both happen in the same locale, but different patterns can be
processed in different locales.
- It is the caller's responsibility to ensure that the memory containing
+ It is the caller's responsibility to ensure that the memory containing
the tables remains available while they are still in use. When they are
- no longer needed, you can discard them using pcre2_maketables_free(),
- which should pass as its first parameter the same global context that
+ no longer needed, you can discard them using pcre2_maketables_free(),
+ which should pass as its first parameter the same global context that
was used to create the tables.
Saving locale tables
- The tables described above are just a sequence of binary bytes, which
- makes them independent of hardware characteristics such as endianness
- or whether the processor is 32-bit or 64-bit. A copy of the result of
- pcre2_maketables() can therefore be saved in a file or elsewhere and
- re-used later, even in a different program or on another computer. The
- size of the tables (number of bytes) must be obtained by calling
- pcre2_config() with the PCRE2_CONFIG_TABLES_LENGTH option because
- pcre2_maketables() does not return this value. Note that the
+ The tables described above are just a sequence of binary bytes, which
+ makes them independent of hardware characteristics such as endianness
+ or whether the processor is 32-bit or 64-bit. A copy of the result of
+ pcre2_maketables() can therefore be saved in a file or elsewhere and
+ re-used later, even in a different program or on another computer. The
+ size of the tables (number of bytes) must be obtained by calling
+ pcre2_config() with the PCRE2_CONFIG_TABLES_LENGTH option because
+ pcre2_maketables() does not return this value. Note that the
pcre2_dftables program, which is part of the PCRE2 build system, can be
used stand-alone to create a file that contains a set of binary tables.
See the pcre2build documentation for details.
@@ -2043,13 +2046,13 @@ INFORMATION ABOUT A COMPILED PATTERN
int pcre2_pattern_info(const pcre2 *code, uint32_t what, void *where);
- The pcre2_pattern_info() function returns general information about a
+ The pcre2_pattern_info() function returns general information about a
compiled pattern. For information about callouts, see the next section.
- The first argument for pcre2_pattern_info() is a pointer to the com-
+ The first argument for pcre2_pattern_info() is a pointer to the com-
piled pattern. The second argument specifies which piece of information
- is required, and the third argument is a pointer to a variable to re-
- ceive the data. If the third argument is NULL, the first argument is
- ignored, and the function returns the size in bytes of the variable
+ is required, and the third argument is a pointer to a variable to re-
+ ceive the data. If the third argument is NULL, the first argument is
+ ignored, and the function returns the size in bytes of the variable
that is required for the information requested. Otherwise, the yield of
the function is zero for success, or one of the following negative num-
bers:
@@ -2060,8 +2063,8 @@ INFORMATION ABOUT A COMPILED PATTERN
PCRE2_ERROR_UNSET the requested field is not set
The "magic number" is placed at the start of each compiled pattern as a
- simple check against passing an arbitrary memory pointer. Here is a
- typical call of pcre2_pattern_info(), to obtain the length of the com-
+ simple check against passing an arbitrary memory pointer. Here is a
+ typical call of pcre2_pattern_info(), to obtain the length of the com-
piled pattern:
int rc;
@@ -2079,22 +2082,22 @@ INFORMATION ABOUT A COMPILED PATTERN
PCRE2_INFO_EXTRAOPTIONS
Return copies of the pattern's options. The third argument should point
- to a uint32_t variable. PCRE2_INFO_ARGOPTIONS returns exactly the op-
- tions that were passed to pcre2_compile(), whereas PCRE2_INFO_ALLOP-
- TIONS returns the compile options as modified by any top-level (*XXX)
- option settings such as (*UTF) at the start of the pattern itself.
- PCRE2_INFO_EXTRAOPTIONS returns the extra options that were set in the
- compile context by calling the pcre2_set_compile_extra_options() func-
+ to a uint32_t variable. PCRE2_INFO_ARGOPTIONS returns exactly the op-
+ tions that were passed to pcre2_compile(), whereas PCRE2_INFO_ALLOP-
+ TIONS returns the compile options as modified by any top-level (*XXX)
+ option settings such as (*UTF) at the start of the pattern itself.
+ PCRE2_INFO_EXTRAOPTIONS returns the extra options that were set in the
+ compile context by calling the pcre2_set_compile_extra_options() func-
tion.
- For example, if the pattern /(*UTF)abc/ is compiled with the PCRE2_EX-
- TENDED option, the result for PCRE2_INFO_ALLOPTIONS is PCRE2_EXTENDED
- and PCRE2_UTF. Option settings such as (?i) that can change within a
+ For example, if the pattern /(*UTF)abc/ is compiled with the PCRE2_EX-
+ TENDED option, the result for PCRE2_INFO_ALLOPTIONS is PCRE2_EXTENDED
+ and PCRE2_UTF. Option settings such as (?i) that can change within a
pattern do not affect the result of PCRE2_INFO_ALLOPTIONS, even if they
- appear right at the start of the pattern. (This was different in some
+ appear right at the start of the pattern. (This was different in some
earlier releases.)
- A pattern compiled without PCRE2_ANCHORED is automatically anchored by
+ A pattern compiled without PCRE2_ANCHORED is automatically anchored by
PCRE2 if the first significant item in every top-level branch is one of
the following:
@@ -2103,7 +2106,7 @@ INFORMATION ABOUT A COMPILED PATTERN
\G always
.* sometimes - see below
- When .* is the first significant item, anchoring is possible only when
+ When .* is the first significant item, anchoring is possible only when
all the following are true:
.* is not in an atomic group
@@ -2113,94 +2116,94 @@ INFORMATION ABOUT A COMPILED PATTERN
Neither (*PRUNE) nor (*SKIP) appears in the pattern
PCRE2_NO_DOTSTAR_ANCHOR is not set
- For patterns that are auto-anchored, the PCRE2_ANCHORED bit is set in
+ For patterns that are auto-anchored, the PCRE2_ANCHORED bit is set in
the options returned for PCRE2_INFO_ALLOPTIONS.
PCRE2_INFO_BACKREFMAX
- Return the number of the highest backreference in the pattern. The
- third argument should point to a uint32_t variable. Named capture
- groups acquire numbers as well as names, and these count towards the
- highest backreference. Backreferences such as \4 or \g{12} match the
+ Return the number of the highest backreference in the pattern. The
+ third argument should point to a uint32_t variable. Named capture
+ groups acquire numbers as well as names, and these count towards the
+ highest backreference. Backreferences such as \4 or \g{12} match the
captured characters of the given group, but in addition, the check that
a capture group is set in a conditional group such as (?(3)a|b) is also
a backreference. Zero is returned if there are no backreferences.
PCRE2_INFO_BSR
- The output is a uint32_t integer whose value indicates what character
- sequences the \R escape sequence matches. A value of PCRE2_BSR_UNICODE
- means that \R matches any Unicode line ending sequence; a value of
+ The output is a uint32_t integer whose value indicates what character
+ sequences the \R escape sequence matches. A value of PCRE2_BSR_UNICODE
+ means that \R matches any Unicode line ending sequence; a value of
PCRE2_BSR_ANYCRLF means that \R matches only CR, LF, or CRLF.
PCRE2_INFO_CAPTURECOUNT
- Return the highest capture group number in the pattern. In patterns
+ Return the highest capture group number in the pattern. In patterns
where (?| is not used, this is also the total number of capture groups.
The third argument should point to a uint32_t variable.
PCRE2_INFO_DEPTHLIMIT
- If the pattern set a backtracking depth limit by including an item of
- the form (*LIMIT_DEPTH=nnnn) at the start, the value is returned. The
+ If the pattern set a backtracking depth limit by including an item of
+ the form (*LIMIT_DEPTH=nnnn) at the start, the value is returned. The
third argument should point to a uint32_t integer. If no such value has
- been set, the call to pcre2_pattern_info() returns the error PCRE2_ER-
+ been set, the call to pcre2_pattern_info() returns the error PCRE2_ER-
ROR_UNSET. Note that this limit will only be used during matching if it
- is less than the limit set or defaulted by the caller of the match
+ is less than the limit set or defaulted by the caller of the match
function.
PCRE2_INFO_FIRSTBITMAP
- In the absence of a single first code unit for a non-anchored pattern,
- pcre2_compile() may construct a 256-bit table that defines a fixed set
- of values for the first code unit in any match. For example, a pattern
- that starts with [abc] results in a table with three bits set. When
- code unit values greater than 255 are supported, the flag bit for 255
- means "any code unit of value 255 or above". If such a table was con-
- structed, a pointer to it is returned. Otherwise NULL is returned. The
+ In the absence of a single first code unit for a non-anchored pattern,
+ pcre2_compile() may construct a 256-bit table that defines a fixed set
+ of values for the first code unit in any match. For example, a pattern
+ that starts with [abc] results in a table with three bits set. When
+ code unit values greater than 255 are supported, the flag bit for 255
+ means "any code unit of value 255 or above". If such a table was con-
+ structed, a pointer to it is returned. Otherwise NULL is returned. The
third argument should point to a const uint8_t * variable.
PCRE2_INFO_FIRSTCODETYPE
Return information about the first code unit of any matched string, for
- a non-anchored pattern. The third argument should point to a uint32_t
- variable. If there is a fixed first value, for example, the letter "c"
- from a pattern such as (cat|cow|coyote), 1 is returned, and the value
- can be retrieved using PCRE2_INFO_FIRSTCODEUNIT. If there is no fixed
- first value, but it is known that a match can occur only at the start
- of the subject or following a newline in the subject, 2 is returned.
+ a non-anchored pattern. The third argument should point to a uint32_t
+ variable. If there is a fixed first value, for example, the letter "c"
+ from a pattern such as (cat|cow|coyote), 1 is returned, and the value
+ can be retrieved using PCRE2_INFO_FIRSTCODEUNIT. If there is no fixed
+ first value, but it is known that a match can occur only at the start
+ of the subject or following a newline in the subject, 2 is returned.
Otherwise, and for anchored patterns, 0 is returned.
PCRE2_INFO_FIRSTCODEUNIT
- Return the value of the first code unit of any matched string for a
- pattern where PCRE2_INFO_FIRSTCODETYPE returns 1; otherwise return 0.
- The third argument should point to a uint32_t variable. In the 8-bit
- library, the value is always less than 256. In the 16-bit library the
- value can be up to 0xffff. In the 32-bit library in UTF-32 mode the
+ Return the value of the first code unit of any matched string for a
+ pattern where PCRE2_INFO_FIRSTCODETYPE returns 1; otherwise return 0.
+ The third argument should point to a uint32_t variable. In the 8-bit
+ library, the value is always less than 256. In the 16-bit library the
+ value can be up to 0xffff. In the 32-bit library in UTF-32 mode the
value can be up to 0x10ffff, and up to 0xffffffff when not using UTF-32
mode.
PCRE2_INFO_FRAMESIZE
Return the size (in bytes) of the data frames that are used to remember
- backtracking positions when the pattern is processed by pcre2_match()
- without the use of JIT. The third argument should point to a size_t
+ backtracking positions when the pattern is processed by pcre2_match()
+ without the use of JIT. The third argument should point to a size_t
variable. The frame size depends on the number of capturing parentheses
in the pattern. Each additional capture group adds two PCRE2_SIZE vari-
ables.
PCRE2_INFO_HASBACKSLASHC
- Return 1 if the pattern contains any instances of \C, otherwise 0. The
+ Return 1 if the pattern contains any instances of \C, otherwise 0. The
third argument should point to a uint32_t variable.
PCRE2_INFO_HASCRORLF
- Return 1 if the pattern contains any explicit matches for CR or LF
- characters, otherwise 0. The third argument should point to a uint32_t
- variable. An explicit match is either a literal CR or LF character, or
- \r or \n or one of the equivalent hexadecimal or octal escape se-
+ Return 1 if the pattern contains any explicit matches for CR or LF
+ characters, otherwise 0. The third argument should point to a uint32_t
+ variable. An explicit match is either a literal CR or LF character, or
+ \r or \n or one of the equivalent hexadecimal or octal escape se-
quences.
PCRE2_INFO_HEAPLIMIT
@@ -2208,45 +2211,45 @@ INFORMATION ABOUT A COMPILED PATTERN
If the pattern set a heap memory limit by including an item of the form
(*LIMIT_HEAP=nnnn) at the start, the value is returned. The third argu-
ment should point to a uint32_t integer. If no such value has been set,
- the call to pcre2_pattern_info() returns the error PCRE2_ERROR_UNSET.
- Note that this limit will only be used during matching if it is less
+ the call to pcre2_pattern_info() returns the error PCRE2_ERROR_UNSET.
+ Note that this limit will only be used during matching if it is less
than the limit set or defaulted by the caller of the match function.
PCRE2_INFO_JCHANGED
- Return 1 if the (?J) or (?-J) option setting is used in the pattern,
- otherwise 0. The third argument should point to a uint32_t variable.
- (?J) and (?-J) set and unset the local PCRE2_DUPNAMES option, respec-
+ Return 1 if the (?J) or (?-J) option setting is used in the pattern,
+ otherwise 0. The third argument should point to a uint32_t variable.
+ (?J) and (?-J) set and unset the local PCRE2_DUPNAMES option, respec-
tively.
PCRE2_INFO_JITSIZE
- If the compiled pattern was successfully processed by pcre2_jit_com-
- pile(), return the size of the JIT compiled code, otherwise return
+ If the compiled pattern was successfully processed by pcre2_jit_com-
+ pile(), return the size of the JIT compiled code, otherwise return
zero. The third argument should point to a size_t variable.
PCRE2_INFO_LASTCODETYPE
- Returns 1 if there is a rightmost literal code unit that must exist in
- any matched string, other than at its start. The third argument should
+ Returns 1 if there is a rightmost literal code unit that must exist in
+ any matched string, other than at its start. The third argument should
point to a uint32_t variable. If there is no such value, 0 is returned.
- When 1 is returned, the code unit value itself can be retrieved using
+ When 1 is returned, the code unit value itself can be retrieved using
PCRE2_INFO_LASTCODEUNIT. For anchored patterns, a last literal value is
- recorded only if it follows something of variable length. For example,
- for the pattern /^a\d+z\d+/ the returned value is 1 (with "z" returned
- from PCRE2_INFO_LASTCODEUNIT), but for /^a\dz\d/ the returned value is
+ recorded only if it follows something of variable length. For example,
+ for the pattern /^a\d+z\d+/ the returned value is 1 (with "z" returned
+ from PCRE2_INFO_LASTCODEUNIT), but for /^a\dz\d/ the returned value is
0.
PCRE2_INFO_LASTCODEUNIT
- Return the value of the rightmost literal code unit that must exist in
- any matched string, other than at its start, for a pattern where
+ Return the value of the rightmost literal code unit that must exist in
+ any matched string, other than at its start, for a pattern where
PCRE2_INFO_LASTCODETYPE returns 1. Otherwise, return 0. The third argu-
ment should point to a uint32_t variable.
PCRE2_INFO_MATCHEMPTY
- Return 1 if the pattern might match an empty string, otherwise 0. The
+ Return 1 if the pattern might match an empty string, otherwise 0. The
third argument should point to a uint32_t variable. When a pattern con-
tains recursive subroutine calls it is not always possible to determine
whether or not it can match an empty string. PCRE2 takes a cautious ap-
@@ -2254,44 +2257,44 @@ INFORMATION ABOUT A COMPILED PATTERN
PCRE2_INFO_MATCHLIMIT
- If the pattern set a match limit by including an item of the form
- (*LIMIT_MATCH=nnnn) at the start, the value is returned. The third ar-
- gument should point to a uint32_t integer. If no such value has been
+ If the pattern set a match limit by including an item of the form
+ (*LIMIT_MATCH=nnnn) at the start, the value is returned. The third ar-
+ gument should point to a uint32_t integer. If no such value has been
set, the call to pcre2_pattern_info() returns the error PCRE2_ERROR_UN-
- SET. Note that this limit will only be used during matching if it is
- less than the limit set or defaulted by the caller of the match func-
+ SET. Note that this limit will only be used during matching if it is
+ less than the limit set or defaulted by the caller of the match func-
tion.
PCRE2_INFO_MAXLOOKBEHIND
- A lookbehind assertion moves back a certain number of characters (not
- code units) when it starts to process each of its branches. This re-
- quest returns the largest of these backward moves. The third argument
+ A lookbehind assertion moves back a certain number of characters (not
+ code units) when it starts to process each of its branches. This re-
+ quest returns the largest of these backward moves. The third argument
should point to a uint32_t integer. The simple assertions \b and \B re-
- quire a one-character lookbehind and cause PCRE2_INFO_MAXLOOKBEHIND to
- return 1 in the absence of anything longer. \A also registers a one-
- character lookbehind, though it does not actually inspect the previous
+ quire a one-character lookbehind and cause PCRE2_INFO_MAXLOOKBEHIND to
+ return 1 in the absence of anything longer. \A also registers a one-
+ character lookbehind, though it does not actually inspect the previous
character.
Note that this information is useful for multi-segment matching only if
- the pattern contains no nested lookbehinds. For example, the pattern
- (?<=a(?<=ba)c) returns a maximum lookbehind of 2, but when it is pro-
- cessed, the first lookbehind moves back by two characters, matches one
- character, then the nested lookbehind also moves back by two charac-
+ the pattern contains no nested lookbehinds. For example, the pattern
+ (?<=a(?<=ba)c) returns a maximum lookbehind of 2, but when it is pro-
+ cessed, the first lookbehind moves back by two characters, matches one
+ character, then the nested lookbehind also moves back by two charac-
ters. This puts the matching point three characters earlier than it was
- at the start. PCRE2_INFO_MAXLOOKBEHIND is really only useful as a de-
- bugging tool. See the pcre2partial documentation for a discussion of
+ at the start. PCRE2_INFO_MAXLOOKBEHIND is really only useful as a de-
+ bugging tool. See the pcre2partial documentation for a discussion of
multi-segment matching.
PCRE2_INFO_MINLENGTH
- If a minimum length for matching subject strings was computed, its
+ If a minimum length for matching subject strings was computed, its
value is returned. Otherwise the returned value is 0. This value is not
- computed when PCRE2_NO_START_OPTIMIZE is set. The value is a number of
- characters, which in UTF mode may be different from the number of code
- units. The third argument should point to a uint32_t variable. The
- 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
+ computed when PCRE2_NO_START_OPTIMIZE is set. The value is a number of
+ characters, which in UTF mode may be different from the number of code
+ units. The third argument should point to a uint32_t variable. The
+ 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.
PCRE2_INFO_NAMECOUNT
@@ -2299,51 +2302,51 @@ INFORMATION ABOUT A COMPILED PATTERN
PCRE2_INFO_NAMETABLE
PCRE2 supports the use of named as well as numbered capturing parenthe-
- ses. The names are just an additional way of identifying the parenthe-
+ ses. The names are just an additional way of identifying the parenthe-
ses, which still acquire numbers. Several convenience functions such as
- pcre2_substring_get_byname() are provided for extracting captured sub-
- strings by name. It is also possible to extract the data directly, by
- first converting the name to a number in order to access the correct
- pointers in the output vector (described with pcre2_match() below). To
+ pcre2_substring_get_byname() are provided for extracting captured sub-
+ strings by name. It is also possible to extract the data directly, by
+ first converting the name to a number in order to access the correct
+ pointers in the output vector (described with pcre2_match() below). To
do the conversion, you need to use the name-to-number map, which is de-
scribed by these three values.
- The map consists of a number of fixed-size entries. PCRE2_INFO_NAME-
- COUNT gives the number of entries, and PCRE2_INFO_NAMEENTRYSIZE gives
- the size of each entry in code units; both of these return a uint32_t
+ The map consists of a number of fixed-size entries. PCRE2_INFO_NAME-
+ COUNT gives the number of entries, and PCRE2_INFO_NAMEENTRYSIZE gives
+ the size of each entry in code units; both of these return a uint32_t
value. The entry size depends on the length of the longest name.
PCRE2_INFO_NAMETABLE returns a pointer to the first entry of the table.
This is a PCRE2_SPTR pointer to a block of code units. In the 8-bit li-
- brary, the first two bytes of each entry are the number of the captur-
- ing parenthesis, most significant byte first. In the 16-bit library,
- the pointer points to 16-bit code units, the first of which contains
- the parenthesis number. In the 32-bit library, the pointer points to
- 32-bit code units, the first of which contains the parenthesis number.
+ brary, the first two bytes of each entry are the number of the captur-
+ ing parenthesis, most significant byte first. In the 16-bit library,
+ the pointer points to 16-bit code units, the first of which contains
+ the parenthesis number. In the 32-bit library, the pointer points to
+ 32-bit code units, the first of which contains the parenthesis number.
The rest of the entry is the corresponding name, zero terminated.
- The names are in alphabetical order. If (?| is used to create multiple
+ The names are in alphabetical order. If (?| is used to create multiple
capture groups with the same number, as described in the section on du-
plicate group numbers in the pcre2pattern page, the groups may be given
- the same name, but there is only one entry in the table. Different
+ the same name, but there is only one entry in the table. Different
names for groups of the same number are not permitted.
- Duplicate names for capture groups with different numbers are permit-
+ Duplicate names for capture groups with different numbers are permit-
ted, but only if PCRE2_DUPNAMES is set. 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 capture groups may have lower num-
+ 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 capture groups may have lower num-
bers.
- As a simple example of the name/number table, consider the following
- pattern after compilation by the 8-bit library (assume PCRE2_EXTENDED
+ As a simple example of the name/number table, consider the following
+ pattern after compilation by the 8-bit library (assume PCRE2_EXTENDED
is set, so white space - including newlines - is ignored):
(?<date> (?<year>(\d\d)?\d\d) -
(?<month>\d\d) - (?<day>\d\d) )
There are four named capture groups, so the table has four entries, and
- each entry in the table is eight bytes long. The table is as follows,
+ each entry in the table is eight bytes long. The table is as follows,
with non-printing bytes shows in hexadecimal, and undefined bytes shown
as ??:
@@ -2352,8 +2355,8 @@ INFORMATION ABOUT A COMPILED PATTERN
00 04 m o n t h 00
00 02 y e a r 00 ??
- When writing code to extract data from named capture groups using the
- name-to-number map, remember that the length of the entries is likely
+ When writing code to extract data from named capture groups using the
+ name-to-number map, remember that the length of the entries is likely
to be different for each compiled pattern.
PCRE2_INFO_NEWLINE
@@ -2372,14 +2375,14 @@ INFORMATION ABOUT A COMPILED PATTERN
PCRE2_INFO_SIZE
- Return the size of the compiled pattern in bytes (for all three li-
- braries). The third argument should point to a size_t variable. This
- value includes the size of the general data block that precedes the
- code units of the compiled pattern itself. The value that is used when
- pcre2_compile() is getting memory in which to place the compiled pat-
+ Return the size of the compiled pattern in bytes (for all three li-
+ braries). The third argument should point to a size_t variable. This
+ value includes the size of the general data block that precedes the
+ code units of the compiled pattern itself. The value that is used when
+ pcre2_compile() is getting memory in which to place the compiled pat-
tern may be slightly larger than the value returned by this option, be-
- cause there are cases where the code that calculates the size has to
- over-estimate. Processing a pattern with the JIT compiler does not al-
+ cause there are cases where the code that calculates the size has to
+ over-estimate. Processing a pattern with the JIT compiler does not al-
ter the value returned by this option.
@@ -2390,30 +2393,30 @@ INFORMATION ABOUT A PATTERN'S CALLOUTS
void *user_data);
A script language that supports the use of string arguments in callouts
- might like to scan all the callouts in a pattern before running the
+ might like to scan all the callouts in a pattern before running the
match. This can be done by calling pcre2_callout_enumerate(). The first
- argument is a pointer to a compiled pattern, the second points to a
- callback function, and the third is arbitrary user data. The callback
- function is called for every callout in the pattern in the order in
+ argument is a pointer to a compiled pattern, the second points to a
+ callback function, and the third is arbitrary user data. The callback
+ function is called for every callout in the pattern in the order in
which they appear. Its first argument is a pointer to a callout enumer-
- ation block, and its second argument is the user_data value that was
- passed to pcre2_callout_enumerate(). The contents of the callout enu-
- meration block are described in the pcre2callout documentation, which
+ ation block, and its second argument is the user_data value that was
+ passed to pcre2_callout_enumerate(). The contents of the callout enu-
+ meration block are described in the pcre2callout documentation, which
also gives further details about callouts.
SERIALIZATION AND PRECOMPILING
- It is possible to save compiled patterns on disc or elsewhere, and
- reload them later, subject to a number of restrictions. The host on
- which the patterns are reloaded must be running the same version of
+ It is possible to save compiled patterns on disc or elsewhere, and
+ reload them later, subject to a number of restrictions. The host on
+ which the patterns are reloaded must be running the same version of
PCRE2, with the same code unit width, and must also have the same endi-
- anness, pointer width, and PCRE2_SIZE type. Before compiled patterns
- can be saved, they must be converted to a "serialized" form, which in
- the case of PCRE2 is really just a bytecode dump. The functions whose
- names begin with pcre2_serialize_ are used for converting to and from
- the serialized form. They are described in the pcre2serialize documen-
- tation. Note that PCRE2 serialization does not convert compiled pat-
+ anness, pointer width, and PCRE2_SIZE type. Before compiled patterns
+ can be saved, they must be converted to a "serialized" form, which in
+ the case of PCRE2 is really just a bytecode dump. The functions whose
+ names begin with pcre2_serialize_ are used for converting to and from
+ the serialized form. They are described in the pcre2serialize documen-
+ tation. Note that PCRE2 serialization does not convert compiled pat-
terns to an abstract format like Java or .NET serialization.
@@ -2427,58 +2430,58 @@ THE MATCH DATA BLOCK
void pcre2_match_data_free(pcre2_match_data *match_data);
- Information about a successful or unsuccessful match is placed in a
- match data block, which is an opaque structure that is accessed by
- function calls. In particular, the match data block contains a vector
- of offsets into the subject string that define the matched part of the
- subject and any substrings that were captured. This is known as the
+ Information about a successful or unsuccessful match is placed in a
+ match data block, which is an opaque structure that is accessed by
+ function calls. In particular, the match data block contains a vector
+ of offsets into the subject string that define the matched part of the
+ subject and any substrings that were captured. This is known as the
ovector.
- Before calling pcre2_match(), pcre2_dfa_match(), or pcre2_jit_match()
+ Before calling pcre2_match(), pcre2_dfa_match(), or pcre2_jit_match()
you must create a match data block by calling one of the creation func-
- tions above. For pcre2_match_data_create(), the first argument is the
- number of pairs of offsets in the ovector. One pair of offsets is re-
- quired to identify the string that matched the whole pattern, with an
- additional pair for each captured substring. For example, a value of 4
- creates enough space to record the matched portion of the subject plus
- three captured substrings. A minimum of at least 1 pair is imposed by
+ tions above. For pcre2_match_data_create(), the first argument is the
+ number of pairs of offsets in the ovector. One pair of offsets is re-
+ quired to identify the string that matched the whole pattern, with an
+ additional pair for each captured substring. For example, a value of 4
+ creates enough space to record the matched portion of the subject plus
+ three captured substrings. A minimum of at least 1 pair is imposed by
pcre2_match_data_create(), so it is always possible to return the over-
all matched string.
The second argument of pcre2_match_data_create() is a pointer to a gen-
- eral context, which can specify custom memory management for obtaining
+ eral context, which can specify custom memory management for obtaining
the memory for the match data block. If you are not using custom memory
management, pass NULL, which causes malloc() to be used.
- For pcre2_match_data_create_from_pattern(), the first argument is a
+ For pcre2_match_data_create_from_pattern(), the first argument is a
pointer to a compiled pattern. The ovector is created to be exactly the
right size to hold all the substrings a pattern might capture. The sec-
- ond argument is again a pointer to a general context, but in this case
+ ond argument is again a pointer to a general context, but in this case
if NULL is passed, the memory is obtained using the same allocator that
was used for the compiled pattern (custom or default).
- A match data block can be used many times, with the same or different
- compiled patterns. You can extract information from a match data block
- after a match operation has finished, using functions that are de-
+ A match data block can be used many times, with the same or different
+ compiled patterns. You can extract information from a match data block
+ after a match operation has finished, using functions that are de-
scribed in the sections on matched strings and other match data below.
- When a call of pcre2_match() fails, valid data is available in the
- match block only when the error is PCRE2_ERROR_NOMATCH, PCRE2_ER-
- ROR_PARTIAL, or one of the error codes for an invalid UTF string. Ex-
+ When a call of pcre2_match() fails, valid data is available in the
+ match block only when the error is PCRE2_ERROR_NOMATCH, PCRE2_ER-
+ ROR_PARTIAL, or one of the error codes for an invalid UTF string. Ex-
actly what is available depends on the error, and is detailed below.
- When one of the matching functions is called, pointers to the compiled
- pattern and the subject string are set in the match data block so that
- they can be referenced by the extraction functions after a successful
+ When one of the matching functions is called, pointers to the compiled
+ pattern and the subject string are set in the match data block so that
+ they can be referenced by the extraction functions after a successful
match. After running a match, you must not free a compiled pattern or a
- subject string until after all operations on the match data block (for
- that match) have taken place, unless, in the case of the subject
- string, you have used the PCRE2_COPY_MATCHED_SUBJECT option, which is
- described in the section entitled "Option bits for pcre2_match()" be-
+ subject string until after all operations on the match data block (for
+ that match) have taken place, unless, in the case of the subject
+ string, you have used the PCRE2_COPY_MATCHED_SUBJECT option, which is
+ described in the section entitled "Option bits for pcre2_match()" be-
low.
- When a match data block itself is no longer needed, it should be freed
- by calling pcre2_match_data_free(). If this function is called with a
+ When a match data block itself is no longer needed, it should be freed
+ by calling pcre2_match_data_free(). If this function is called with a
NULL argument, it returns immediately, without doing anything.
@@ -2489,15 +2492,15 @@ MATCHING A PATTERN: THE TRADITIONAL FUNCTION
uint32_t options, pcre2_match_data *match_data,
pcre2_match_context *mcontext);
- The function pcre2_match() is called to match a subject string against
- a compiled pattern, which is passed in the code argument. You can call
+ The function pcre2_match() is called to match a subject string against
+ a compiled pattern, which is passed in the code argument. You can call
pcre2_match() with the same code argument as many times as you like, in
- order to find multiple matches in the subject string or to match dif-
+ order to find multiple matches in the subject string or to match dif-
ferent subject strings with the same pattern.
- This function is the main matching facility of the library, and it op-
- erates in a Perl-like manner. For specialist use there is also an al-
- ternative matching function, which is described below in the section
+ This function is the main matching facility of the library, and it op-
+ erates in a Perl-like manner. For specialist use there is also an al-
+ ternative matching function, which is described below in the section
about the pcre2_dfa_match() function.
Here is an example of a simple call to pcre2_match():
@@ -2512,215 +2515,215 @@ MATCHING A PATTERN: THE TRADITIONAL FUNCTION
md, /* the match data block */
NULL); /* a match context; NULL means use defaults */
- If the subject string is zero-terminated, the length can be given as
+ If the subject string is zero-terminated, the length can be given as
PCRE2_ZERO_TERMINATED. A match context must be provided if certain less
common matching parameters are to be changed. For details, see the sec-
tion on the match context above.
The string to be matched by pcre2_match()
- The subject string is passed to pcre2_match() as a pointer in subject,
- a length in length, and a starting offset in startoffset. The length
- and offset are in code units, not characters. That is, they are in
- bytes for the 8-bit library, 16-bit code units for the 16-bit library,
- and 32-bit code units for the 32-bit library, whether or not UTF pro-
+ The subject string is passed to pcre2_match() as a pointer in subject,
+ a length in length, and a starting offset in startoffset. The length
+ and offset are in code units, not characters. That is, they are in
+ bytes for the 8-bit library, 16-bit code units for the 16-bit library,
+ and 32-bit code units for the 32-bit library, whether or not UTF pro-
cessing is enabled.
If startoffset is greater than the length of the subject, pcre2_match()
- returns PCRE2_ERROR_BADOFFSET. When the starting offset is zero, the
- search for a match starts at the beginning of the subject, and this is
+ returns PCRE2_ERROR_BADOFFSET. When the starting offset is zero, the
+ search for a match starts at the beginning of the subject, and this is
by far the most common case. In UTF-8 or UTF-16 mode, the starting off-
- set must point to the start of a character, or to the end of the sub-
- ject (in UTF-32 mode, one code unit equals one character, so all off-
- sets are valid). Like the pattern string, the subject may contain bi-
+ set must point to the start of a character, or to the end of the sub-
+ ject (in UTF-32 mode, one code unit equals one character, so all off-
+ sets are valid). Like the pattern string, the subject may contain bi-
nary zeros.
- A non-zero starting offset is useful when searching for another match
- in the same subject by calling pcre2_match() again after a previous
- success. Setting startoffset differs from passing over a shortened
- string and setting PCRE2_NOTBOL in the case of a pattern that begins
+ A non-zero starting offset is useful when searching for another match
+ in the same subject by calling pcre2_match() again after a previous
+ success. Setting startoffset differs from passing over a shortened
+ string and setting PCRE2_NOTBOL in the case of a pattern that begins
with any kind of lookbehind. For example, consider the pattern
\Biss\B
- which finds occurrences of "iss" in the middle of words. (\B matches
- only if the current position in the subject is not a word boundary.)
+ which finds occurrences of "iss" in the middle of words. (\B matches
+ only if the current position in the subject is not a word boundary.)
When applied to the string "Mississipi" the first call to pcre2_match()
- finds the first occurrence. If pcre2_match() is called again with just
- the remainder of the subject, namely "issipi", it does not match, be-
- cause \B is always false at the start of the subject, which is deemed
- to be a word boundary. However, if pcre2_match() is passed the entire
+ finds the first occurrence. If pcre2_match() is called again with just
+ the remainder of the subject, namely "issipi", it does not match, be-
+ cause \B is always false at the start of the subject, which is deemed
+ to be a word boundary. However, if pcre2_match() is passed the entire
string again, but with startoffset set to 4, it finds the second occur-
- rence of "iss" because it is able to look behind the starting point to
+ rence of "iss" because it is able to look behind the starting point to
discover that it is preceded by a letter.
- Finding all the matches in a subject is tricky when the pattern can
+ Finding all the matches in a subject is tricky when the pattern can
match an empty string. It is possible to emulate Perl's /g behaviour by
- first trying the match again at the same offset, with the
- PCRE2_NOTEMPTY_ATSTART and PCRE2_ANCHORED options, and then if that
- fails, advancing the starting offset and trying an ordinary match
- again. There is some code that demonstrates how to do this in the
- pcre2demo sample program. In the most general case, you have to check
- to see if the newline convention recognizes CRLF as a newline, and if
- so, and the current character is CR followed by LF, advance the start-
+ first trying the match again at the same offset, with the
+ PCRE2_NOTEMPTY_ATSTART and PCRE2_ANCHORED options, and then if that
+ fails, advancing the starting offset and trying an ordinary match
+ again. There is some code that demonstrates how to do this in the
+ pcre2demo sample program. In the most general case, you have to check
+ to see if the newline convention recognizes CRLF as a newline, and if
+ so, and the current character is CR followed by LF, advance the start-
ing offset by two characters instead of one.
If a non-zero starting offset is passed when the pattern is anchored, a
single attempt to match at the given offset is made. This can only suc-
- ceed if the pattern does not require the match to be at the start of
- the subject. In other words, the anchoring must be the result of set-
- ting the PCRE2_ANCHORED option or the use of .* with PCRE2_DOTALL, not
+ ceed if the pattern does not require the match to be at the start of
+ the subject. In other words, the anchoring must be the result of set-
+ ting the PCRE2_ANCHORED option or the use of .* with PCRE2_DOTALL, not
by starting the pattern with ^ or \A.
Option bits for pcre2_match()
The unused bits of the options argument for pcre2_match() must be zero.
- The only bits that may be set are PCRE2_ANCHORED,
- PCRE2_COPY_MATCHED_SUBJECT, PCRE2_ENDANCHORED, PCRE2_NOTBOL, PCRE2_NO-
+ The only bits that may be set are PCRE2_ANCHORED,
+ PCRE2_COPY_MATCHED_SUBJECT, PCRE2_ENDANCHORED, PCRE2_NOTBOL, PCRE2_NO-
TEOL, PCRE2_NOTEMPTY, PCRE2_NOTEMPTY_ATSTART, PCRE2_NO_JIT,
- PCRE2_NO_UTF_CHECK, PCRE2_PARTIAL_HARD, and PCRE2_PARTIAL_SOFT. Their
+ PCRE2_NO_UTF_CHECK, PCRE2_PARTIAL_HARD, and PCRE2_PARTIAL_SOFT. Their
action is described below.
- Setting PCRE2_ANCHORED or PCRE2_ENDANCHORED at match time is not sup-
- ported by the just-in-time (JIT) compiler. If it is set, JIT matching
- is disabled and the interpretive code in pcre2_match() is run. Apart
- from PCRE2_NO_JIT (obviously), the remaining options are supported for
+ Setting PCRE2_ANCHORED or PCRE2_ENDANCHORED at match time is not sup-
+ ported by the just-in-time (JIT) compiler. If it is set, JIT matching
+ is disabled and the interpretive code in pcre2_match() is run. Apart
+ from PCRE2_NO_JIT (obviously), the remaining options are supported for
JIT matching.
PCRE2_ANCHORED
The PCRE2_ANCHORED option limits pcre2_match() to matching at the first
- matching position. If a pattern was compiled with PCRE2_ANCHORED, or
- turned out to be anchored by virtue of its contents, it cannot be made
- unachored at matching time. Note that setting the option at match time
+ matching position. If a pattern was compiled with PCRE2_ANCHORED, or
+ turned out to be anchored by virtue of its contents, it cannot be made
+ unachored at matching time. Note that setting the option at match time
disables JIT matching.
PCRE2_COPY_MATCHED_SUBJECT
- By default, a pointer to the subject is remembered in the match data
- block so that, after a successful match, it can be referenced by the
- substring extraction functions. This means that the subject's memory
- must not be freed until all such operations are complete. For some ap-
- plications where the lifetime of the subject string is not guaranteed,
- it may be necessary to make a copy of the subject string, but it is
- wasteful to do this unless the match is successful. After a successful
- match, if PCRE2_COPY_MATCHED_SUBJECT is set, the subject is copied and
- the new pointer is remembered in the match data block instead of the
- original subject pointer. The memory allocator that was used for the
- match block itself is used. The copy is automatically freed when
- pcre2_match_data_free() is called to free the match data block. It is
+ By default, a pointer to the subject is remembered in the match data
+ block so that, after a successful match, it can be referenced by the
+ substring extraction functions. This means that the subject's memory
+ must not be freed until all such operations are complete. For some ap-
+ plications where the lifetime of the subject string is not guaranteed,
+ it may be necessary to make a copy of the subject string, but it is
+ wasteful to do this unless the match is successful. After a successful
+ match, if PCRE2_COPY_MATCHED_SUBJECT is set, the subject is copied and
+ the new pointer is remembered in the match data block instead of the
+ original subject pointer. The memory allocator that was used for the
+ match block itself is used. The copy is automatically freed when
+ pcre2_match_data_free() is called to free the match data block. It is
also automatically freed if the match data block is re-used for another
match operation.
PCRE2_ENDANCHORED
- If the PCRE2_ENDANCHORED option is set, any string that pcre2_match()
- matches must be right at the end of the subject string. Note that set-
+ If the PCRE2_ENDANCHORED option is set, any string that pcre2_match()
+ matches must be right at the end of the subject string. Note that set-
ting the option at match time disables JIT matching.
PCRE2_NOTBOL
This option specifies that first character of the subject string is not
- the beginning of a line, so the circumflex metacharacter should not
- match before it. Setting this without having set PCRE2_MULTILINE at
+ the beginning of a line, so the circumflex metacharacter should not
+ match before it. Setting this without having set PCRE2_MULTILINE at
compile time causes circumflex never to match. This option affects only
the behaviour of the circumflex metacharacter. It does not affect \A.
PCRE2_NOTEOL
This option specifies that the end of the subject string is not the end
- of a line, so the dollar metacharacter should not match it nor (except
- in multiline mode) a newline immediately before it. Setting this with-
- out having set PCRE2_MULTILINE at compile time causes dollar never to
+ of a line, so the dollar metacharacter should not match it nor (except
+ in multiline mode) a newline immediately before it. Setting this with-
+ out having set PCRE2_MULTILINE at compile time causes dollar never to
match. This option affects only the behaviour of the dollar metacharac-
ter. It does not affect \Z or \z.
PCRE2_NOTEMPTY
An empty string is not considered to be a valid match if this option is
- set. If there are alternatives in the pattern, they are tried. If all
- the alternatives match the empty string, the entire match fails. For
+ set. If there are alternatives in the pattern, they are tried. If all
+ the alternatives match the empty string, the entire match fails. For
example, if the pattern
a?b?
- is applied to a string not beginning with "a" or "b", it matches an
+ is applied to a string not beginning with "a" or "b", it matches an
empty string at the start of the subject. With PCRE2_NOTEMPTY set, this
- match is not valid, so pcre2_match() searches further into the string
+ match is not valid, so pcre2_match() searches further into the string
for occurrences of "a" or "b".
PCRE2_NOTEMPTY_ATSTART
- This is like PCRE2_NOTEMPTY, except that it locks out an empty string
+ This is like PCRE2_NOTEMPTY, except that it locks out an empty string
match only at the first matching position, that is, at the start of the
- subject plus the starting offset. An empty string match later in the
+ subject plus the starting offset. An empty string match later in the
subject is permitted. If the pattern is anchored, such a match can oc-
cur only if the pattern contains \K.
PCRE2_NO_JIT
- By default, if a pattern has been successfully processed by
- pcre2_jit_compile(), JIT is automatically used when pcre2_match() is
- called with options that JIT supports. Setting PCRE2_NO_JIT disables
+ By default, if a pattern has been successfully processed by
+ pcre2_jit_compile(), JIT is automatically used when pcre2_match() is
+ called with options that JIT supports. Setting PCRE2_NO_JIT disables
the use of JIT; it forces matching to be done by the interpreter.
PCRE2_NO_UTF_CHECK
When PCRE2_UTF is set at compile time, the validity of the subject as a
- UTF string is checked unless PCRE2_NO_UTF_CHECK is passed to
+ UTF string is checked unless PCRE2_NO_UTF_CHECK is passed to
pcre2_match() or PCRE2_MATCH_INVALID_UTF was passed to pcre2_compile().
The latter special case is discussed in detail in the pcre2unicode doc-
umentation.
- In the default case, if a non-zero starting offset is given, the check
- is applied only to that part of the subject that could be inspected
- during matching, and there is a check that the starting offset points
- to the first code unit of a character or to the end of the subject. If
- there are no lookbehind assertions in the pattern, the check starts at
+ In the default case, if a non-zero starting offset is given, the check
+ is applied only to that part of the subject that could be inspected
+ during matching, and there is a check that the starting offset points
+ to the first code unit of a character or to the end of the subject. If
+ there are no lookbehind assertions in the pattern, the check starts at
the starting offset. Otherwise, it starts at the length of the longest
- lookbehind before the starting offset, or at the start of the subject
- if there are not that many characters before the starting offset. Note
+ lookbehind before the starting offset, or at the start of the subject
+ if there are not that many characters before the starting offset. Note
that the sequences \b and \B are one-character lookbehinds.
The check is carried out before any other processing takes place, and a
- negative error code is returned if the check fails. There are several
- UTF error codes for each code unit width, corresponding to different
- problems with the code unit sequence. There are discussions about the
- validity of UTF-8 strings, UTF-16 strings, and UTF-32 strings in the
+ negative error code is returned if the check fails. There are several
+ UTF error codes for each code unit width, corresponding to different
+ problems with the code unit sequence. There are discussions about the
+ validity of UTF-8 strings, UTF-16 strings, and UTF-32 strings in the
pcre2unicode documentation.
If you know that your subject is valid, and you want to skip this check
for performance reasons, you can set the PCRE2_NO_UTF_CHECK option when
- calling pcre2_match(). You might want to do this for the second and
- subsequent calls to pcre2_match() if you are making repeated calls to
+ calling pcre2_match(). You might want to do this for the second and
+ subsequent calls to pcre2_match() if you are making repeated calls to
find multiple matches in the same subject string.
- Warning: Unless PCRE2_MATCH_INVALID_UTF was set at compile time, when
- PCRE2_NO_UTF_CHECK is set at match time the effect of passing an in-
+ Warning: Unless PCRE2_MATCH_INVALID_UTF was set at compile time, when
+ PCRE2_NO_UTF_CHECK is set at match time the effect of passing an in-
valid string as a subject, or an invalid value of startoffset, is unde-
- fined. Your program may crash or loop indefinitely or give wrong re-
+ fined. Your program may crash or loop indefinitely or give wrong re-
sults.
PCRE2_PARTIAL_HARD
PCRE2_PARTIAL_SOFT
These options turn on the partial matching feature. A partial match oc-
- curs if the end of the subject string is reached successfully, but
+ curs if the end of the subject string is reached successfully, but
there are not enough subject characters to complete the match. In addi-
- tion, either at least one character must have been inspected or the
- pattern must contain a lookbehind, or the pattern must be one that
+ tion, either at least one character must have been inspected or the
+ pattern must contain a lookbehind, or the pattern must be one that
could match an empty string.
- If this situation arises when PCRE2_PARTIAL_SOFT (but not PCRE2_PAR-
+ If this situation arises when PCRE2_PARTIAL_SOFT (but not PCRE2_PAR-
TIAL_HARD) is set, matching continues by testing any remaining alterna-
- tives. Only if no complete match can be found is PCRE2_ERROR_PARTIAL
- returned instead of PCRE2_ERROR_NOMATCH. In other words, PCRE2_PAR-
- TIAL_SOFT specifies that the caller is prepared to handle a partial
+ tives. Only if no complete match can be found is PCRE2_ERROR_PARTIAL
+ returned instead of PCRE2_ERROR_NOMATCH. In other words, PCRE2_PAR-
+ TIAL_SOFT specifies that the caller is prepared to handle a partial
match, but only if no complete match can be found.
- If PCRE2_PARTIAL_HARD is set, it overrides PCRE2_PARTIAL_SOFT. In this
- case, if a partial match is found, pcre2_match() immediately returns
- PCRE2_ERROR_PARTIAL, without considering any other alternatives. In
+ If PCRE2_PARTIAL_HARD is set, it overrides PCRE2_PARTIAL_SOFT. In this
+ case, if a partial match is found, pcre2_match() immediately returns
+ PCRE2_ERROR_PARTIAL, without considering any other alternatives. In
other words, when PCRE2_PARTIAL_HARD is set, a partial match is consid-
ered to be more important that an alternative complete match.
@@ -2730,38 +2733,38 @@ MATCHING A PATTERN: THE TRADITIONAL FUNCTION
NEWLINE HANDLING WHEN MATCHING
- When PCRE2 is built, a default newline convention is set; this is usu-
- ally the standard convention for the operating system. The default can
- be overridden in a compile context by calling pcre2_set_newline(). It
- can also be overridden by starting a pattern string with, for example,
- (*CRLF), as described in the section on newline conventions in the
- pcre2pattern page. During matching, the newline choice affects the be-
- haviour of the dot, circumflex, and dollar metacharacters. It may also
- alter the way the match starting position is advanced after a match
+ When PCRE2 is built, a default newline convention is set; this is usu-
+ ally the standard convention for the operating system. The default can
+ be overridden in a compile context by calling pcre2_set_newline(). It
+ can also be overridden by starting a pattern string with, for example,
+ (*CRLF), as described in the section on newline conventions in the
+ pcre2pattern page. During matching, the newline choice affects the be-
+ haviour of the dot, circumflex, and dollar metacharacters. It may also
+ alter the way the match starting position is advanced after a match
failure for an unanchored pattern.
When PCRE2_NEWLINE_CRLF, PCRE2_NEWLINE_ANYCRLF, or PCRE2_NEWLINE_ANY is
- set as the newline convention, and a match attempt for an unanchored
+ set as the newline convention, and a match attempt for an unanchored
pattern fails when the current starting position is at a CRLF sequence,
- and the pattern contains no explicit matches for CR or LF characters,
- the match position is advanced by two characters instead of one, in
+ and the pattern contains no explicit matches for CR or LF characters,
+ the match position is advanced by two characters instead of one, in
other words, to after the CRLF.
The above rule is a compromise that makes the most common cases work as
- expected. For example, if the pattern is .+A (and the PCRE2_DOTALL op-
- tion is not set), it does not match the string "\r\nA" because, after
- failing at the start, it skips both the CR and the LF before retrying.
- However, the pattern [\r\n]A does match that string, because it con-
+ expected. For example, if the pattern is .+A (and the PCRE2_DOTALL op-
+ tion is not set), it does not match the string "\r\nA" because, after
+ failing at the start, it skips both the CR and the LF before retrying.
+ However, the pattern [\r\n]A does match that string, because it con-
tains an explicit CR or LF reference, and so advances only by one char-
acter after the first failure.
An explicit match for CR of LF is either a literal appearance of one of
- those characters in the pattern, or one of the \r or \n or equivalent
+ those characters in the pattern, or one of the \r or \n or equivalent
octal or hexadecimal escape sequences. Implicit matches such as [^X] do
- not count, nor does \s, even though it includes CR and LF in the char-
+ not count, nor does \s, even though it includes CR and LF in the char-
acters that it matches.
- Notwithstanding the above, anomalous effects may still occur when CRLF
+ Notwithstanding the above, anomalous effects may still occur when CRLF
is a valid newline sequence and explicit \r or \n escapes appear in the
pattern.
@@ -2772,82 +2775,82 @@ HOW PCRE2_MATCH() RETURNS A STRING AND CAPTURED SUBSTRINGS
PCRE2_SIZE *pcre2_get_ovector_pointer(pcre2_match_data *match_data);
- In general, a pattern matches a certain portion of the subject, and in
- addition, further substrings from the subject may be picked out by
- parenthesized parts of the pattern. Following the usage in Jeffrey
- Friedl's book, this is called "capturing" in what follows, and the
- phrase "capture group" (Perl terminology) is used for a fragment of a
- pattern that picks out a substring. PCRE2 supports several other kinds
+ In general, a pattern matches a certain portion of the subject, and in
+ addition, further substrings from the subject may be picked out by
+ parenthesized parts of the pattern. Following the usage in Jeffrey
+ Friedl's book, this is called "capturing" in what follows, and the
+ phrase "capture group" (Perl terminology) is used for a fragment of a
+ pattern that picks out a substring. PCRE2 supports several other kinds
of parenthesized group that do not cause substrings to be captured. The
- pcre2_pattern_info() function can be used to find out how many capture
+ pcre2_pattern_info() function can be used to find out how many capture
groups there are in a compiled pattern.
- You can use auxiliary functions for accessing captured substrings by
+ You can use auxiliary functions for accessing captured substrings by
number or by name, as described in sections below.
Alternatively, you can make direct use of the vector of PCRE2_SIZE val-
- ues, called the ovector, which contains the offsets of captured
- strings. It is part of the match data block. The function
- pcre2_get_ovector_pointer() returns the address of the ovector, and
+ ues, called the ovector, which contains the offsets of captured
+ strings. It is part of the match data block. The function
+ pcre2_get_ovector_pointer() returns the address of the ovector, and
pcre2_get_ovector_count() returns the number of pairs of values it con-
tains.
Within the ovector, the first in each pair of values is set to the off-
set of the first code unit of a substring, and the second is set to the
- offset of the first code unit after the end of a substring. These val-
- ues are always code unit offsets, not character offsets. That is, they
+ offset of the first code unit after the end of a substring. These val-
+ ues are always code unit offsets, not character offsets. That is, they
are byte offsets in the 8-bit library, 16-bit offsets in the 16-bit li-
brary, and 32-bit offsets in the 32-bit library.
- After a partial match (error return PCRE2_ERROR_PARTIAL), only the
- first pair of offsets (that is, ovector[0] and ovector[1]) are set.
- They identify the part of the subject that was partially matched. See
+ After a partial match (error return PCRE2_ERROR_PARTIAL), only the
+ first pair of offsets (that is, ovector[0] and ovector[1]) are set.
+ They identify the part of the subject that was partially matched. See
the pcre2partial documentation for details of partial matching.
- After a fully successful match, the first pair of offsets identifies
- the portion of the subject string that was matched by the entire pat-
- tern. The next pair is used for the first captured substring, and so
- on. The value returned by pcre2_match() is one more than the highest
- numbered pair that has been set. For example, if two substrings have
- been captured, the returned value is 3. If there are no captured sub-
+ After a fully successful match, the first pair of offsets identifies
+ the portion of the subject string that was matched by the entire pat-
+ tern. The next pair is used for the first captured substring, and so
+ on. The value returned by pcre2_match() is one more than the highest
+ numbered pair that has been set. For example, if two substrings have
+ been captured, the returned value is 3. If there are no captured sub-
strings, the return value from a successful match is 1, indicating that
just the first pair of offsets has been set.
- If a pattern uses the \K escape sequence within a positive assertion,
+ If a pattern uses the \K escape sequence within a positive assertion,
the reported start of a successful match can be greater than the end of
- the match. For example, if the pattern (?=ab\K) is matched against
+ the match. For example, if the pattern (?=ab\K) is matched against
"ab", the start and end offset values for the match are 2 and 0.
- If a capture group is matched repeatedly within a single match opera-
+ If a capture group is matched repeatedly within a single match opera-
tion, it is the last portion of the subject that it matched that is re-
turned.
If the ovector is too small to hold all the captured substring offsets,
- as much as possible is filled in, and the function returns a value of
- zero. If captured substrings are not of interest, pcre2_match() may be
+ as much as possible is filled in, and the function returns a value of
+ zero. If captured substrings are not of interest, pcre2_match() may be
called with a match data block whose ovector is of minimum length (that
is, one pair).
- It is possible for capture group number n+1 to match some part of the
- subject when group n has not been used at all. For example, if the
+ It is possible for capture group number n+1 to match some part of the
+ subject when group n has not been used at all. For example, if the
string "abc" is matched against the pattern (a|(z))(bc) the return from
- the function is 4, and groups 1 and 3 are matched, but 2 is not. When
- this happens, both values in the offset pairs corresponding to unused
+ the function is 4, and groups 1 and 3 are matched, but 2 is not. When
+ this happens, both values in the offset pairs corresponding to unused
groups are set to PCRE2_UNSET.
- Offset values that correspond to unused groups at the end of the ex-
- pression are also set to PCRE2_UNSET. For example, if the string "abc"
- is matched against the pattern (abc)(x(yz)?)? groups 2 and 3 are not
- matched. The return from the function is 2, because the highest used
- capture group number is 1. The offsets for for the second and third
- capture groupss (assuming the vector is large enough, of course) are
+ Offset values that correspond to unused groups at the end of the ex-
+ pression are also set to PCRE2_UNSET. For example, if the string "abc"
+ is matched against the pattern (abc)(x(yz)?)? groups 2 and 3 are not
+ matched. The return from the function is 2, because the highest used
+ capture group number is 1. The offsets for for the second and third
+ capture groupss (assuming the vector is large enough, of course) are
set to PCRE2_UNSET.
Elements in the ovector that do not correspond to capturing parentheses
in the pattern are never changed. That is, if a pattern contains n cap-
turing parentheses, no more than ovector[0] to ovector[2n+1] are set by
- pcre2_match(). The other elements retain whatever values they previ-
- ously had. After a failed match attempt, the contents of the ovector
+ pcre2_match(). The other elements retain whatever values they previ-
+ ously had. After a failed match attempt, the contents of the ovector
are unchanged.
@@ -2857,69 +2860,69 @@ OTHER INFORMATION ABOUT A MATCH
PCRE2_SIZE pcre2_get_startchar(pcre2_match_data *match_data);
- As well as the offsets in the ovector, other information about a match
- is retained in the match data block and can be retrieved by the above
- functions in appropriate circumstances. If they are called at other
+ As well as the offsets in the ovector, other information about a match
+ is retained in the match data block and can be retrieved by the above
+ functions in appropriate circumstances. If they are called at other
times, the result is undefined.
- After a successful match, a partial match (PCRE2_ERROR_PARTIAL), or a
- failure to match (PCRE2_ERROR_NOMATCH), a mark name may be available.
- The function pcre2_get_mark() can be called to access this name, which
- can be specified in the pattern by any of the backtracking control
+ After a successful match, a partial match (PCRE2_ERROR_PARTIAL), or a
+ failure to match (PCRE2_ERROR_NOMATCH), a mark name may be available.
+ The function pcre2_get_mark() can be called to access this name, which
+ can be specified in the pattern by any of the backtracking control
verbs, not just (*MARK). The same function applies to all the verbs. It
returns a pointer to the zero-terminated name, which is within the com-
piled pattern. If no name is available, NULL is returned. The length of
- the name (excluding the terminating zero) is stored in the code unit
- that precedes the name. You should use this length instead of relying
+ the name (excluding the terminating zero) is stored in the code unit
+ that precedes the name. You should use this length instead of relying
on the terminating zero if the name might contain a binary zero.
- After a successful match, the name that is returned is the last mark
+ After a successful match, the name that is returned is the last mark
name encountered on the matching path through the pattern. Instances of
- backtracking verbs without names do not count. Thus, for example, if
+ backtracking verbs without names do not count. Thus, for example, if
the matching path contains (*MARK:A)(*PRUNE), the name "A" is returned.
After a "no match" or a partial match, the last encountered name is re-
turned. For example, consider this pattern:
^(*MARK:A)((*MARK:B)a|b)c
- When it matches "bc", the returned name is A. The B mark is "seen" in
- the first branch of the group, but it is not on the matching path. On
- the other hand, when this pattern fails to match "bx", the returned
+ When it matches "bc", the returned name is A. The B mark is "seen" in
+ the first branch of the group, but it is not on the matching path. On
+ the other hand, when this pattern fails to match "bx", the returned
name is B.
- Warning: By default, certain start-of-match optimizations are used to
- give a fast "no match" result in some situations. For example, if the
- anchoring is removed from the pattern above, there is an initial check
- for the presence of "c" in the subject before running the matching en-
+ Warning: By default, certain start-of-match optimizations are used to
+ give a fast "no match" result in some situations. For example, if the
+ anchoring is removed from the pattern above, there is an initial check
+ for the presence of "c" in the subject before running the matching en-
gine. This check fails for "bx", causing a match failure without seeing
- any marks. You can disable the start-of-match optimizations by setting
- the PCRE2_NO_START_OPTIMIZE option for pcre2_compile() or by starting
+ any marks. You can disable the start-of-match optimizations by setting
+ the PCRE2_NO_START_OPTIMIZE option for pcre2_compile() or by starting
the pattern with (*NO_START_OPT).
- After a successful match, a partial match, or one of the invalid UTF
- errors (for example, PCRE2_ERROR_UTF8_ERR5), pcre2_get_startchar() can
+ After a successful match, a partial match, or one of the invalid UTF
+ errors (for example, PCRE2_ERROR_UTF8_ERR5), pcre2_get_startchar() can
be called. After a successful or partial match it returns the code unit
- offset of the character at which the match started. For a non-partial
- match, this can be different to the value of ovector[0] if the pattern
- contains the \K escape sequence. After a partial match, however, this
- value is always the same as ovector[0] because \K does not affect the
+ offset of the character at which the match started. For a non-partial
+ match, this can be different to the value of ovector[0] if the pattern
+ contains the \K escape sequence. After a partial match, however, this
+ value is always the same as ovector[0] because \K does not affect the
result of a partial match.
- After a UTF check failure, pcre2_get_startchar() can be used to obtain
+ After a UTF check failure, pcre2_get_startchar() can be used to obtain
the code unit offset of the invalid UTF character. Details are given in
the pcre2unicode page.
ERROR RETURNS FROM pcre2_match()
- If pcre2_match() fails, it returns a negative number. This can be con-
- verted to a text string by calling the pcre2_get_error_message() func-
- tion (see "Obtaining a textual error message" below). Negative error
- codes are also returned by other functions, and are documented with
- them. The codes are given names in the header file. If UTF checking is
+ If pcre2_match() fails, it returns a negative number. This can be con-
+ verted to a text string by calling the pcre2_get_error_message() func-
+ tion (see "Obtaining a textual error message" below). Negative error
+ codes are also returned by other functions, and are documented with
+ them. The codes are given names in the header file. If UTF checking is
in force and an invalid UTF subject string is detected, one of a number
- of UTF-specific negative error codes is returned. Details are given in
- the pcre2unicode page. The following are the other errors that may be
+ of UTF-specific negative error codes is returned. Details are given in
+ the pcre2unicode page. The following are the other errors that may be
returned by pcre2_match():
PCRE2_ERROR_NOMATCH
@@ -2928,20 +2931,20 @@ ERROR RETURNS FROM pcre2_match()
PCRE2_ERROR_PARTIAL
- The subject string did not match, but it did match partially. See the
+ The subject string did not match, but it did match partially. See the
pcre2partial documentation for details of partial matching.
PCRE2_ERROR_BADMAGIC
PCRE2 stores a 4-byte "magic number" at the start of the compiled code,
- to catch the case when it is passed a junk pointer. This is the error
+ to catch the case when it is passed a junk pointer. This is the error
that is returned when the magic number is not present.
PCRE2_ERROR_BADMODE
- This error is given when a compiled pattern is passed to a function in
- a library of a different code unit width, for example, a pattern com-
- piled by the 8-bit library is passed to a 16-bit or 32-bit library
+ This error is given when a compiled pattern is passed to a function in
+ a library of a different code unit width, for example, a pattern com-
+ piled by the 8-bit library is passed to a 16-bit or 32-bit library
function.
PCRE2_ERROR_BADOFFSET
@@ -2955,15 +2958,15 @@ ERROR RETURNS FROM pcre2_match()
PCRE2_ERROR_BADUTFOFFSET
The UTF code unit sequence that was passed as a subject was checked and
- found to be valid (the PCRE2_NO_UTF_CHECK option was not set), but the
- value of startoffset did not point to the beginning of a UTF character
+ found to be valid (the PCRE2_NO_UTF_CHECK option was not set), but the
+ value of startoffset did not point to the beginning of a UTF character
or the end of the subject.
PCRE2_ERROR_CALLOUT
- This error is never generated by pcre2_match() itself. It is provided
- for use by callout functions that want to cause pcre2_match() or
- pcre2_callout_enumerate() to return a distinctive error code. See the
+ This error is never generated by pcre2_match() itself. It is provided
+ for use by callout functions that want to cause pcre2_match() or
+ pcre2_callout_enumerate() to return a distinctive error code. See the
pcre2callout documentation for details.
PCRE2_ERROR_DEPTHLIMIT
@@ -2976,14 +2979,14 @@ ERROR RETURNS FROM pcre2_match()
PCRE2_ERROR_INTERNAL
- An unexpected internal error has occurred. This error could be caused
+ An unexpected internal error has occurred. This error could be caused
by a bug in PCRE2 or by overwriting of the compiled pattern.
PCRE2_ERROR_JIT_STACKLIMIT
This error is returned when a pattern that was successfully studied us-
ing JIT is being matched, but the memory available for the just-in-time
- processing stack is not large enough. See the pcre2jit documentation
+ processing stack is not large enough. See the pcre2jit documentation
for more details.
PCRE2_ERROR_MATCHLIMIT
@@ -2992,11 +2995,11 @@ ERROR RETURNS FROM pcre2_match()
PCRE2_ERROR_NOMEMORY
- If a pattern contains many nested backtracking points, heap memory is
- used to remember them. This error is given when the memory allocation
- function (default or custom) fails. Note that a different error,
- PCRE2_ERROR_HEAPLIMIT, is given if the amount of memory needed exceeds
- the heap limit. PCRE2_ERROR_NOMEMORY is also returned if
+ If a pattern contains many nested backtracking points, heap memory is
+ used to remember them. This error is given when the memory allocation
+ function (default or custom) fails. Note that a different error,
+ PCRE2_ERROR_HEAPLIMIT, is given if the amount of memory needed exceeds
+ the heap limit. PCRE2_ERROR_NOMEMORY is also returned if
PCRE2_COPY_MATCHED_SUBJECT is set and memory allocation fails.
PCRE2_ERROR_NULL
@@ -3005,12 +3008,12 @@ ERROR RETURNS FROM pcre2_match()
PCRE2_ERROR_RECURSELOOP
- This error is returned when pcre2_match() detects a recursion loop
- within the pattern. Specifically, it means that either the whole pat-
+ This error is returned when pcre2_match() detects a recursion loop
+ within the pattern. Specifically, it means that either the whole pat-
tern or a capture group has been called recursively for the second time
- at the same position in the subject string. Some simple patterns that
- might do this are detected and faulted at compile time, but more com-
- plicated cases, in particular mutual recursions between two different
+ at the same position in the subject string. Some simple patterns that
+ might do this are detected and faulted at compile time, but more com-
+ plicated cases, in particular mutual recursions between two different
groups, cannot be detected until matching is attempted.
@@ -3019,20 +3022,20 @@ OBTAINING A TEXTUAL ERROR MESSAGE
int pcre2_get_error_message(int errorcode, PCRE2_UCHAR *buffer,
PCRE2_SIZE bufflen);
- A text message for an error code from any PCRE2 function (compile,
- match, or auxiliary) can be obtained by calling pcre2_get_error_mes-
- sage(). The code is passed as the first argument, with the remaining
- two arguments specifying a code unit buffer and its length in code
- units, into which the text message is placed. The message is returned
- in code units of the appropriate width for the library that is being
+ A text message for an error code from any PCRE2 function (compile,
+ match, or auxiliary) can be obtained by calling pcre2_get_error_mes-
+ sage(). The code is passed as the first argument, with the remaining
+ two arguments specifying a code unit buffer and its length in code
+ units, into which the text message is placed. The message is returned
+ in code units of the appropriate width for the library that is being
used.
- The returned message is terminated with a trailing zero, and the func-
- tion returns the number of code units used, excluding the trailing
+ The returned message is terminated with a trailing zero, and the func-
+ tion returns the number of code units used, excluding the trailing
zero. If the error number is unknown, the negative error code PCRE2_ER-
- ROR_BADDATA is returned. If the buffer is too small, the message is
+ ROR_BADDATA is returned. If the buffer is too small, the message is
truncated (but still with a trailing zero), and the negative error code
- PCRE2_ERROR_NOMEMORY is returned. None of the messages are very long;
+ PCRE2_ERROR_NOMEMORY is returned. None of the messages are very long;
a buffer size of 120 code units is ample.
@@ -3051,39 +3054,39 @@ EXTRACTING CAPTURED SUBSTRINGS BY NUMBER
void pcre2_substring_free(PCRE2_UCHAR *buffer);
- Captured substrings can be accessed directly by using the ovector as
+ Captured substrings can be accessed directly by using the ovector as
described above. For convenience, auxiliary functions are provided for
- extracting captured substrings as new, separate, zero-terminated
+ extracting captured substrings as new, separate, zero-terminated
strings. A substring that contains a binary zero is correctly extracted
- and has a further zero added on the end, but the result is not, of
+ and has a further zero added on the end, but the result is not, of
course, a C string.
The functions in this section identify substrings by number. The number
zero refers to the entire matched substring, with higher numbers refer-
- ring to substrings captured by parenthesized groups. After a partial
- match, only substring zero is available. An attempt to extract any
- other substring gives the error PCRE2_ERROR_PARTIAL. The next section
+ ring to substrings captured by parenthesized groups. After a partial
+ match, only substring zero is available. An attempt to extract any
+ other substring gives the error PCRE2_ERROR_PARTIAL. The next section
describes similar functions for extracting captured substrings by name.
- If a pattern uses the \K escape sequence within a positive assertion,
+ If a pattern uses the \K escape sequence within a positive assertion,
the reported start of a successful match can be greater than the end of
- the match. For example, if the pattern (?=ab\K) is matched against
- "ab", the start and end offset values for the match are 2 and 0. In
- this situation, calling these functions with a zero substring number
+ the match. For example, if the pattern (?=ab\K) is matched against
+ "ab", the start and end offset values for the match are 2 and 0. In
+ this situation, calling these functions with a zero substring number
extracts a zero-length empty string.
- You can find the length in code units of a captured substring without
- extracting it by calling pcre2_substring_length_bynumber(). The first
- argument is a pointer to the match data block, the second is the group
- number, and the third is a pointer to a variable into which the length
- is placed. If you just want to know whether or not the substring has
+ You can find the length in code units of a captured substring without
+ extracting it by calling pcre2_substring_length_bynumber(). The first
+ argument is a pointer to the match data block, the second is the group
+ number, and the third is a pointer to a variable into which the length
+ is placed. If you just want to know whether or not the substring has
been captured, you can pass the third argument as NULL.
- The pcre2_substring_copy_bynumber() function copies a captured sub-
- string into a supplied buffer, whereas pcre2_substring_get_bynumber()
- copies it into new memory, obtained using the same memory allocation
- function that was used for the match data block. The first two argu-
- ments of these functions are a pointer to the match data block and a
+ The pcre2_substring_copy_bynumber() function copies a captured sub-
+ string into a supplied buffer, whereas pcre2_substring_get_bynumber()
+ copies it into new memory, obtained using the same memory allocation
+ function that was used for the match data block. The first two argu-
+ ments of these functions are a pointer to the match data block and a
capture group number.
The final arguments of pcre2_substring_copy_bynumber() are a pointer to
@@ -3092,25 +3095,25 @@ EXTRACTING CAPTURED SUBSTRINGS BY NUMBER
for the extracted substring, excluding the terminating zero.
For pcre2_substring_get_bynumber() the third and fourth arguments point
- to variables that are updated with a pointer to the new memory and the
- number of code units that comprise the substring, again excluding the
- terminating zero. When the substring is no longer needed, the memory
+ to variables that are updated with a pointer to the new memory and the
+ number of code units that comprise the substring, again excluding the
+ terminating zero. When the substring is no longer needed, the memory
should be freed by calling pcre2_substring_free().
- The return value from all these functions is zero for success, or a
- negative error code. If the pattern match failed, the match failure
- code is returned. If a substring number greater than zero is used af-
- ter a partial match, PCRE2_ERROR_PARTIAL is returned. Other possible
+ The return value from all these functions is zero for success, or a
+ negative error code. If the pattern match failed, the match failure
+ code is returned. If a substring number greater than zero is used af-
+ ter a partial match, PCRE2_ERROR_PARTIAL is returned. Other possible
error codes are:
PCRE2_ERROR_NOMEMORY
- The buffer was too small for pcre2_substring_copy_bynumber(), or the
+ The buffer was too small for pcre2_substring_copy_bynumber(), or the
attempt to get memory failed for pcre2_substring_get_bynumber().
PCRE2_ERROR_NOSUBSTRING
- There is no substring with that number in the pattern, that is, the
+ There is no substring with that number in the pattern, that is, the
number is greater than the number of capturing parentheses.
PCRE2_ERROR_UNAVAILABLE
@@ -3121,8 +3124,8 @@ EXTRACTING CAPTURED SUBSTRINGS BY NUMBER
PCRE2_ERROR_UNSET
- The substring did not participate in the match. For example, if the
- pattern is (abc)|(def) and the subject is "def", and the ovector con-
+ The substring did not participate in the match. For example, if the
+ pattern is (abc)|(def) and the subject is "def", and the ovector con-
tains at least two capturing slots, substring number 1 is unset.
@@ -3133,31 +3136,31 @@ EXTRACTING A LIST OF ALL CAPTURED SUBSTRINGS
void pcre2_substring_list_free(PCRE2_SPTR *list);
- The pcre2_substring_list_get() function extracts all available sub-
- strings and builds a list of pointers to them. It also (optionally)
- builds a second list that contains their lengths (in code units), ex-
- cluding a terminating zero that is added to each of them. All this is
+ The pcre2_substring_list_get() function extracts all available sub-
+ strings and builds a list of pointers to them. It also (optionally)
+ builds a second list that contains their lengths (in code units), ex-
+ cluding a terminating zero that is added to each of them. All this is
done in a single block of memory that is obtained using the same memory
allocation function that was used to get the match data block.
- This function must be called only after a successful match. If called
+ This function must be called only after a successful match. If called
after a partial match, the error code PCRE2_ERROR_PARTIAL is returned.
- The address of the memory block is returned via listptr, which is also
+ The address of the memory block is returned via listptr, which is also
the start of the list of string pointers. The end of the list is marked
- by a NULL pointer. The address of the list of lengths is returned via
- lengthsptr. If your strings do not contain binary zeros and you do not
+ by a NULL pointer. The address of the list of lengths is returned via
+ lengthsptr. If your strings do not contain binary zeros and you do not
therefore need the lengths, you may supply NULL as the lengthsptr argu-
- ment to disable the creation of a list of lengths. The yield of the
- function is zero if all went well, or PCRE2_ERROR_NOMEMORY if the mem-
- ory block could not be obtained. When the list is no longer needed, it
+ ment to disable the creation of a list of lengths. The yield of the
+ function is zero if all went well, or PCRE2_ERROR_NOMEMORY if the mem-
+ ory block could not be obtained. When the list is no longer needed, it
should be freed by calling pcre2_substring_list_free().
If this function encounters a substring that is unset, which can happen
- when capture group number n+1 matches some part of the subject, but
- group n has not been used at all, it returns an empty string. This can
+ when capture group number n+1 matches some part of the subject, but
+ group n has not been used at all, it returns an empty string. This can
be distinguished from a genuine zero-length substring by inspecting the
- appropriate offset in the ovector, which contain PCRE2_UNSET for unset
+ appropriate offset in the ovector, which contain PCRE2_UNSET for unset
substrings, or by calling pcre2_substring_length_bynumber().
@@ -3177,7 +3180,7 @@ EXTRACTING CAPTURED SUBSTRINGS BY NAME
void pcre2_substring_free(PCRE2_UCHAR *buffer);
- To extract a substring by name, you first have to find associated num-
+ To extract a substring by name, you first have to find associated num-
ber. For example, for this pattern:
(a+)b(?<xxx>\d+)...
@@ -3185,32 +3188,32 @@ EXTRACTING CAPTURED SUBSTRINGS BY NAME
the number of the capture group called "xxx" is 2. If the name is known
to be unique (PCRE2_DUPNAMES was not set), you can find the number from
the name by calling pcre2_substring_number_from_name(). The first argu-
- ment is the compiled pattern, and the second is the name. The yield of
- the function is the group number, PCRE2_ERROR_NOSUBSTRING if there is
- no group with that name, or PCRE2_ERROR_NOUNIQUESUBSTRING if there is
- more than one group with that name. Given the number, you can extract
- the substring directly from the ovector, or use one of the "bynumber"
+ ment is the compiled pattern, and the second is the name. The yield of
+ the function is the group number, PCRE2_ERROR_NOSUBSTRING if there is
+ no group with that name, or PCRE2_ERROR_NOUNIQUESUBSTRING if there is
+ more than one group with that name. Given the number, you can extract
+ the substring directly from the ovector, or use one of the "bynumber"
functions described above.
- For convenience, there are also "byname" functions that correspond to
+ For convenience, there are also "byname" functions that correspond to
the "bynumber" functions, the only difference being that the second ar-
- gument is a name instead of a number. If PCRE2_DUPNAMES is set and
+ gument is a name instead of a number. If PCRE2_DUPNAMES is set and
there are duplicate names, these functions scan all the groups with the
- given name, and return the captured substring from the first named
+ given name, and return the captured substring from the first named
group that is set.
- If there are no groups with the given name, PCRE2_ERROR_NOSUBSTRING is
- returned. If all groups with the name have numbers that are greater
+ If there are no groups with the given name, PCRE2_ERROR_NOSUBSTRING is
+ returned. If all groups with the name have numbers that are greater
than the number of slots in the ovector, PCRE2_ERROR_UNAVAILABLE is re-
- turned. If there is at least one group with a slot in the ovector, but
+ turned. If there is at least one group with a slot in the ovector, but
no group is found to be set, PCRE2_ERROR_UNSET is returned.
Warning: If the pattern uses the (?| feature to set up multiple capture
- groups with the same number, as described in the section on duplicate
+ groups with the same number, as described in the section on duplicate
group numbers in the pcre2pattern page, you cannot use names to distin-
- guish the different capture groups, because names are not included in
- the compiled code. The matching process uses only numbers. For this
- reason, the use of different names for groups with the same number
+ guish the different capture groups, because names are not included in
+ the compiled code. The matching process uses only numbers. For this
+ reason, the use of different names for groups with the same number
causes an error at compile time.
@@ -3223,126 +3226,126 @@ CREATING A NEW STRING WITH SUBSTITUTIONS
PCRE2_SIZE rlength, PCRE2_UCHAR *outputbuffer,
PCRE2_SIZE *outlengthptr);
- This function optionally calls pcre2_match() and then makes a copy of
- the subject string in outputbuffer, replacing parts that were matched
- with the replacement string, whose length is supplied in rlength. This
- can be given as PCRE2_ZERO_TERMINATED for a zero-terminated string.
+ This function optionally calls pcre2_match() and then makes a copy of
+ the subject string in outputbuffer, replacing parts that were matched
+ with the replacement string, whose length is supplied in rlength. This
+ can be given as PCRE2_ZERO_TERMINATED for a zero-terminated string.
There is an option (see PCRE2_SUBSTITUTE_REPLACEMENT_ONLY below) to re-
- turn just the replacement string(s). The default action is to perform
- just one replacement if the pattern matches, but there is an option
- that requests multiple replacements (see PCRE2_SUBSTITUTE_GLOBAL be-
+ turn just the replacement string(s). The default action is to perform
+ just one replacement if the pattern matches, but there is an option
+ that requests multiple replacements (see PCRE2_SUBSTITUTE_GLOBAL be-
low).
- If successful, pcre2_substitute() returns the number of substitutions
- that were carried out. This may be zero if no match was found, and is
- never greater than one unless PCRE2_SUBSTITUTE_GLOBAL is set. A nega-
+ If successful, pcre2_substitute() returns the number of substitutions
+ that were carried out. This may be zero if no match was found, and is
+ never greater than one unless PCRE2_SUBSTITUTE_GLOBAL is set. A nega-
tive value is returned if an error is detected.
- Matches in which a \K item in a lookahead in the pattern causes the
- match to end before it starts are not supported, and give rise to an
+ Matches in which a \K item in a lookahead in the pattern causes the
+ match to end before it starts are not supported, and give rise to an
error return. For global replacements, matches in which \K in a lookbe-
- hind causes the match to start earlier than the point that was reached
+ hind causes the match to start earlier than the point that was reached
in the previous iteration are also not supported.
- The first seven arguments of pcre2_substitute() are the same as for
+ The first seven arguments of pcre2_substitute() are the same as for
pcre2_match(), except that the partial matching options are not permit-
- ted, and match_data may be passed as NULL, in which case a match data
- block is obtained and freed within this function, using memory manage-
- ment functions from the match context, if provided, or else those that
+ ted, and match_data may be passed as NULL, in which case a match data
+ block is obtained and freed within this function, using memory manage-
+ ment functions from the match context, if provided, or else those that
were used to allocate memory for the compiled code.
- If match_data is not NULL and PCRE2_SUBSTITUTE_MATCHED is not set, the
+ If match_data is not NULL and PCRE2_SUBSTITUTE_MATCHED is not set, the
provided block is used for all calls to pcre2_match(), and its contents
- afterwards are the result of the final call. For global changes, this
+ afterwards are the result of the final call. For global changes, this
will always be a no-match error. The contents of the ovector within the
match data block may or may not have been changed.
- As well as the usual options for pcre2_match(), a number of additional
- options can be set in the options argument of pcre2_substitute(). One
- such option is PCRE2_SUBSTITUTE_MATCHED. When this is set, an external
- match_data block must be provided, and it must have been used for an
- external call to pcre2_match(). The data in the match_data block (re-
+ As well as the usual options for pcre2_match(), a number of additional
+ options can be set in the options argument of pcre2_substitute(). One
+ such option is PCRE2_SUBSTITUTE_MATCHED. When this is set, an external
+ match_data block must be provided, and it must have been used for an
+ external call to pcre2_match(). The data in the match_data block (re-
turn code, offset vector) is used for the first substitution instead of
- calling pcre2_match() from within pcre2_substitute(). This allows an
+ calling pcre2_match() from within pcre2_substitute(). This allows an
application to check for a match before choosing to substitute, without
having to repeat the match.
- The contents of the externally supplied match data block are not
- changed when PCRE2_SUBSTITUTE_MATCHED is set. If PCRE2_SUBSTI-
- TUTE_GLOBAL is also set, pcre2_match() is called after the first sub-
- stitution to check for further matches, but this is done using an in-
- ternally obtained match data block, thus always leaving the external
+ The contents of the externally supplied match data block are not
+ changed when PCRE2_SUBSTITUTE_MATCHED is set. If PCRE2_SUBSTI-
+ TUTE_GLOBAL is also set, pcre2_match() is called after the first sub-
+ stitution to check for further matches, but this is done using an in-
+ ternally obtained match data block, thus always leaving the external
block unchanged.
- The code argument is not used for matching before the first substitu-
- tion when PCRE2_SUBSTITUTE_MATCHED is set, but it must be provided,
- even when PCRE2_SUBSTITUTE_GLOBAL is not set, because it contains in-
+ The code argument is not used for matching before the first substitu-
+ tion when PCRE2_SUBSTITUTE_MATCHED is set, but it must be provided,
+ even when PCRE2_SUBSTITUTE_GLOBAL is not set, because it contains in-
formation such as the UTF setting and the number of capturing parenthe-
ses in the pattern.
- The default action of pcre2_substitute() is to return a copy of the
+ The default action of pcre2_substitute() is to return a copy of the
subject string with matched substrings replaced. However, if PCRE2_SUB-
- STITUTE_REPLACEMENT_ONLY is set, only the replacement substrings are
+ STITUTE_REPLACEMENT_ONLY is set, only the replacement substrings are
returned. In the global case, multiple replacements are concatenated in
- the output buffer. Substitution callouts (see below) can be used to
+ the output buffer. Substitution callouts (see below) can be used to
separate them if necessary.
- The outlengthptr argument of pcre2_substitute() must point to a vari-
- able that contains the length, in code units, of the output buffer. If
- the function is successful, the value is updated to contain the length
- in code units of the new string, excluding the trailing zero that is
+ The outlengthptr argument of pcre2_substitute() must point to a vari-
+ able that contains the length, in code units, of the output buffer. If
+ the function is successful, the value is updated to contain the length
+ in code units of the new string, excluding the trailing zero that is
automatically added.
- If the function is not successful, the value set via outlengthptr de-
- pends on the type of error. For syntax errors in the replacement
+ If the function is not successful, the value set via outlengthptr de-
+ pends on the type of error. For syntax errors in the replacement
string, the value is the offset in the replacement string where the er-
- ror was detected. For other errors, the value is PCRE2_UNSET by de-
+ ror was detected. For other errors, the value is PCRE2_UNSET by de-
fault. This includes the case of the output buffer being too small, un-
less PCRE2_SUBSTITUTE_OVERFLOW_LENGTH is set.
- PCRE2_SUBSTITUTE_OVERFLOW_LENGTH changes what happens when the output
+ PCRE2_SUBSTITUTE_OVERFLOW_LENGTH changes what happens when the output
buffer is too small. The default action is to return PCRE2_ERROR_NOMEM-
- ORY immediately. If this option is set, however, pcre2_substitute()
+ ORY immediately. If this option is set, however, pcre2_substitute()
continues to go through the motions of matching and substituting (with-
- out, of course, writing anything) in order to compute the size of buf-
- fer that is needed. This value is passed back via the outlengthptr
- variable, with the result of the function still being PCRE2_ER-
+ out, of course, writing anything) in order to compute the size of buf-
+ fer that is needed. This value is passed back via the outlengthptr
+ variable, with the result of the function still being PCRE2_ER-
ROR_NOMEMORY.
- Passing a buffer size of zero is a permitted way of finding out how
- much memory is needed for given substitution. However, this does mean
+ Passing a buffer size of zero is a permitted way of finding out how
+ much memory is needed for given substitution. However, this does mean
that the entire operation is carried out twice. Depending on the appli-
- cation, it may be more efficient to allocate a large buffer and free
- the excess afterwards, instead of using PCRE2_SUBSTITUTE_OVER-
+ cation, it may be more efficient to allocate a large buffer and free
+ the excess afterwards, instead of using PCRE2_SUBSTITUTE_OVER-
FLOW_LENGTH.
- The replacement string, which is interpreted as a UTF string in UTF
- mode, is checked for UTF validity unless PCRE2_NO_UTF_CHECK is set. An
+ The replacement string, which is interpreted as a UTF string in UTF
+ mode, is checked for UTF validity unless PCRE2_NO_UTF_CHECK is set. An
invalid UTF replacement string causes an immediate return with the rel-
evant UTF error code.
- If PCRE2_SUBSTITUTE_LITERAL is set, the replacement string is not in-
+ If PCRE2_SUBSTITUTE_LITERAL is set, the replacement string is not in-
terpreted in any way. By default, however, a dollar character is an es-
- cape character that can specify the insertion of characters from cap-
- ture groups and names from (*MARK) or other control verbs in the pat-
+ cape character that can specify the insertion of characters from cap-
+ ture groups and names from (*MARK) or other control verbs in the pat-
tern. The following forms are always recognized:
$$ insert a dollar character
$<n> or ${<n>} insert the contents of group <n>
$*MARK or ${*MARK} insert a control verb name
- Either a group number or a group name can be given for <n>. Curly
- brackets are required only if the following character would be inter-
+ Either a group number or a group name can be given for <n>. Curly
+ brackets are required only if the following character would be inter-
preted as part of the number or name. The number may be zero to include
- the entire matched string. For example, if the pattern a(b)c is
- matched with "=abc=" and the replacement string "+$1$0$1+", the result
+ the entire matched string. For example, if the pattern a(b)c is
+ matched with "=abc=" and the replacement string "+$1$0$1+", the result
is "=+babcb+=".
- $*MARK inserts the name from the last encountered backtracking control
- verb on the matching path that has a name. (*MARK) must always include
- a name, but the other verbs need not. For example, in the case of
+ $*MARK inserts the name from the last encountered backtracking control
+ verb on the matching path that has a name. (*MARK) must always include
+ a name, but the other verbs need not. For example, in the case of
(*MARK:A)(*PRUNE) the name inserted is "A", but for (*MARK:A)(*PRUNE:B)
- the relevant name is "B". This facility can be used to perform simple
+ the relevant name is "B". This facility can be used to perform simple
simultaneous substitutions, as this pcre2test example shows:
/(*MARK:pear)apple|(*MARK:orange)lemon/g,replace=${*MARK}
@@ -3350,15 +3353,15 @@ CREATING A NEW STRING WITH SUBSTITUTIONS
2: pear orange
PCRE2_SUBSTITUTE_GLOBAL causes the function to iterate over the subject
- string, replacing every matching substring. If this option is not set,
- only the first matching substring is replaced. The search for matches
- takes place in the original subject string (that is, previous replace-
- ments do not affect it). Iteration is implemented by advancing the
- startoffset value for each search, which is always passed the entire
+ string, replacing every matching substring. If this option is not set,
+ only the first matching substring is replaced. The search for matches
+ takes place in the original subject string (that is, previous replace-
+ ments do not affect it). Iteration is implemented by advancing the
+ startoffset value for each search, which is always passed the entire
subject string. If an offset limit is set in the match context, search-
ing stops when that limit is reached.
- You can restrict the effect of a global substitution to a portion of
+ You can restrict the effect of a global substitution to a portion of
the subject string by setting either or both of startoffset and an off-
set limit. Here is a pcre2test example:
@@ -3366,73 +3369,73 @@ CREATING A NEW STRING WITH SUBSTITUTIONS
ABC ABC ABC ABC\=offset=3,offset_limit=12
2: ABC A!C A!C ABC
- When continuing with global substitutions after matching a substring
+ When continuing with global substitutions after matching a substring
with zero length, an attempt to find a non-empty match at the same off-
set is performed. If this is not successful, the offset is advanced by
one character except when CRLF is a valid newline sequence and the next
- two characters are CR, LF. In this case, the offset is advanced by two
+ two characters are CR, LF. In this case, the offset is advanced by two
characters.
PCRE2_SUBSTITUTE_UNKNOWN_UNSET causes references to capture groups that
do not appear in the pattern to be treated as unset groups. This option
- should be used with care, because it means that a typo in a group name
+ should be used with care, because it means that a typo in a group name
or number no longer causes the PCRE2_ERROR_NOSUBSTRING error.
PCRE2_SUBSTITUTE_UNSET_EMPTY causes unset capture groups (including un-
- known groups when PCRE2_SUBSTITUTE_UNKNOWN_UNSET is set) to be treated
- as empty strings when inserted as described above. If this option is
+ known groups when PCRE2_SUBSTITUTE_UNKNOWN_UNSET is set) to be treated
+ as empty strings when inserted as described above. If this option is
not set, an attempt to insert an unset group causes the PCRE2_ERROR_UN-
- SET error. This option does not influence the extended substitution
+ SET error. This option does not influence the extended substitution
syntax described below.
- PCRE2_SUBSTITUTE_EXTENDED causes extra processing to be applied to the
- replacement string. Without this option, only the dollar character is
- special, and only the group insertion forms listed above are valid.
+ PCRE2_SUBSTITUTE_EXTENDED causes extra processing to be applied to the
+ replacement string. Without this option, only the dollar character is
+ special, and only the group insertion forms listed above are valid.
When PCRE2_SUBSTITUTE_EXTENDED is set, two things change:
- Firstly, backslash in a replacement string is interpreted as an escape
+ Firstly, backslash in a replacement string is interpreted as an escape
character. The usual forms such as \n or \x{ddd} can be used to specify
- particular character codes, and backslash followed by any non-alphanu-
- meric character quotes that character. Extended quoting can be coded
+ particular character codes, and backslash followed by any non-alphanu-
+ meric character quotes that character. Extended quoting can be coded
using \Q...\E, exactly as in pattern strings.
- There are also four escape sequences for forcing the case of inserted
- letters. The insertion mechanism has three states: no case forcing,
+ There are also four escape sequences for forcing the case of inserted
+ letters. The insertion mechanism has three states: no case forcing,
force upper case, and force lower case. The escape sequences change the
current state: \U and \L change to upper or lower case forcing, respec-
- tively, and \E (when not terminating a \Q quoted sequence) reverts to
- no case forcing. The sequences \u and \l force the next character (if
- it is a letter) to upper or lower case, respectively, and then the
+ tively, and \E (when not terminating a \Q quoted sequence) reverts to
+ no case forcing. The sequences \u and \l force the next character (if
+ it is a letter) to upper or lower case, respectively, and then the
state automatically reverts to no case forcing. Case forcing applies to
- all inserted characters, including those from capture groups and let-
- ters within \Q...\E quoted sequences. If either PCRE2_UTF or PCRE2_UCP
- was set when the pattern was compiled, Unicode properties are used for
+ all inserted characters, including those from capture groups and let-
+ ters within \Q...\E quoted sequences. If either PCRE2_UTF or PCRE2_UCP
+ was set when the pattern was compiled, Unicode properties are used for
case forcing characters whose code points are greater than 127.
Note that case forcing sequences such as \U...\E do not nest. For exam-
- ple, the result of processing "\Uaa\LBB\Ecc\E" is "AAbbcc"; the final
- \E has no effect. Note also that the PCRE2_ALT_BSUX and PCRE2_EX-
+ ple, the result of processing "\Uaa\LBB\Ecc\E" is "AAbbcc"; the final
+ \E has no effect. Note also that the PCRE2_ALT_BSUX and PCRE2_EX-
TRA_ALT_BSUX options do not apply to replacement strings.
- The second effect of setting PCRE2_SUBSTITUTE_EXTENDED is to add more
- flexibility to capture group substitution. The syntax is similar to
+ The second effect of setting PCRE2_SUBSTITUTE_EXTENDED is to add more
+ flexibility to capture group substitution. The syntax is similar to
that used by Bash:
${<n>:-<string>}
${<n>:+<string1>:<string2>}
- As before, <n> may be a group number or a name. The first form speci-
- fies a default value. If group <n> is set, its value is inserted; if
- not, <string> is expanded and the result inserted. The second form
- specifies strings that are expanded and inserted when group <n> is set
- or unset, respectively. The first form is just a convenient shorthand
+ As before, <n> may be a group number or a name. The first form speci-
+ fies a default value. If group <n> is set, its value is inserted; if
+ not, <string> is expanded and the result inserted. The second form
+ specifies strings that are expanded and inserted when group <n> is set
+ or unset, respectively. The first form is just a convenient shorthand
for
${<n>:+${<n>}:<string>}
- Backslash can be used to escape colons and closing curly brackets in
- the replacement strings. A change of the case forcing state within a
- replacement string remains in force afterwards, as shown in this
+ Backslash can be used to escape colons and closing curly brackets in
+ the replacement strings. A change of the case forcing state within a
+ replacement string remains in force afterwards, as shown in this
pcre2test example:
/(some)?(body)/substitute_extended,replace=${1:+\U:\L}HeLLo
@@ -3441,8 +3444,8 @@ CREATING A NEW STRING WITH SUBSTITUTIONS
somebody
1: HELLO
- The PCRE2_SUBSTITUTE_UNSET_EMPTY option does not affect these extended
- substitutions. However, PCRE2_SUBSTITUTE_UNKNOWN_UNSET does cause un-
+ The PCRE2_SUBSTITUTE_UNSET_EMPTY option does not affect these extended
+ substitutions. However, PCRE2_SUBSTITUTE_UNKNOWN_UNSET does cause un-
known groups in the extended syntax forms to be treated as unset.
If PCRE2_SUBSTITUTE_LITERAL is set, PCRE2_SUBSTITUTE_UNKNOWN_UNSET,
@@ -3451,37 +3454,37 @@ CREATING A NEW STRING WITH SUBSTITUTIONS
Substitution errors
- In the event of an error, pcre2_substitute() returns a negative error
- code. Except for PCRE2_ERROR_NOMATCH (which is never returned), errors
+ In the event of an error, pcre2_substitute() returns a negative error
+ code. Except for PCRE2_ERROR_NOMATCH (which is never returned), errors
from pcre2_match() are passed straight back.
PCRE2_ERROR_NOSUBSTRING is returned for a non-existent substring inser-
tion, unless PCRE2_SUBSTITUTE_UNKNOWN_UNSET is set.
PCRE2_ERROR_UNSET is returned for an unset substring insertion (includ-
- ing an unknown substring when PCRE2_SUBSTITUTE_UNKNOWN_UNSET is set)
- when the simple (non-extended) syntax is used and PCRE2_SUBSTITUTE_UN-
+ ing an unknown substring when PCRE2_SUBSTITUTE_UNKNOWN_UNSET is set)
+ when the simple (non-extended) syntax is used and PCRE2_SUBSTITUTE_UN-
SET_EMPTY is not set.
- PCRE2_ERROR_NOMEMORY is returned if the output buffer is not big
+ PCRE2_ERROR_NOMEMORY is returned if the output buffer is not big
enough. If the PCRE2_SUBSTITUTE_OVERFLOW_LENGTH option is set, the size
- of buffer that is needed is returned via outlengthptr. Note that this
+ of buffer that is needed is returned via outlengthptr. Note that this
does not happen by default.
PCRE2_ERROR_NULL is returned if PCRE2_SUBSTITUTE_MATCHED is set but the
match_data argument is NULL.
- PCRE2_ERROR_BADREPLACEMENT is used for miscellaneous syntax errors in
- the replacement string, with more particular errors being PCRE2_ER-
+ PCRE2_ERROR_BADREPLACEMENT is used for miscellaneous syntax errors in
+ the replacement string, with more particular errors being PCRE2_ER-
ROR_BADREPESCAPE (invalid escape sequence), PCRE2_ERROR_REPMISSINGBRACE
- (closing curly bracket not found), PCRE2_ERROR_BADSUBSTITUTION (syntax
- error in extended group substitution), and PCRE2_ERROR_BADSUBSPATTERN
+ (closing curly bracket not found), PCRE2_ERROR_BADSUBSTITUTION (syntax
+ error in extended group substitution), and PCRE2_ERROR_BADSUBSPATTERN
(the pattern match ended before it started or the match started earlier
- than the current position in the subject, which can happen if \K is
+ than the current position in the subject, which can happen if \K is
used in an assertion).
As for all PCRE2 errors, a text message that describes the error can be
- obtained by calling the pcre2_get_error_message() function (see "Ob-
+ obtained by calling the pcre2_get_error_message() function (see "Ob-
taining a textual error message" above).
Substitution callouts
@@ -3490,15 +3493,15 @@ CREATING A NEW STRING WITH SUBSTITUTIONS
int (*callout_function)(pcre2_substitute_callout_block *, void *),
void *callout_data);
- The pcre2_set_substitution_callout() function can be used to specify a
- callout function for pcre2_substitute(). This information is passed in
+ The pcre2_set_substitution_callout() function can be used to specify a
+ callout function for pcre2_substitute(). This information is passed in
a match context. The callout function is called after each substitution
has been processed, but it can cause the replacement not to happen. The
- callout function is not called for simulated substitutions that happen
+ callout function is not called for simulated substitutions that happen
as a result of the PCRE2_SUBSTITUTE_OVERFLOW_LENGTH option.
The first argument of the callout function is a pointer to a substitute
- callout block structure, which contains the following fields, not nec-
+ callout block structure, which contains the following fields, not nec-
essarily in this order:
uint32_t version;
@@ -3509,34 +3512,34 @@ CREATING A NEW STRING WITH SUBSTITUTIONS
uint32_t oveccount;
PCRE2_SIZE output_offsets[2];
- The version field contains the version number of the block format. The
- current version is 0. The version number will increase in future if
- more fields are added, but the intention is never to remove any of the
+ The version field contains the version number of the block format. The
+ current version is 0. The version number will increase in future if
+ more fields are added, but the intention is never to remove any of the
existing fields.
The subscount field is the number of the current match. It is 1 for the
first callout, 2 for the second, and so on. The input and output point-
ers are copies of the values passed to pcre2_substitute().
- The ovector field points to the ovector, which contains the result of
+ The ovector field points to the ovector, which contains the result of
the most recent match. The oveccount field contains the number of pairs
that are set in the ovector, and is always greater than zero.
- The output_offsets vector contains the offsets of the replacement in
- the output string. This has already been processed for dollar and (if
+ The output_offsets vector contains the offsets of the replacement in
+ the output string. This has already been processed for dollar and (if
requested) backslash substitutions as described above.
- The second argument of the callout function is the value passed as
- callout_data when the function was registered. The value returned by
+ The second argument of the callout function is the value passed as
+ callout_data when the function was registered. The value returned by
the callout function is interpreted as follows:
- If the value is zero, the replacement is accepted, and, if PCRE2_SUB-
- STITUTE_GLOBAL is set, processing continues with a search for the next
- match. If the value is not zero, the current replacement is not ac-
- cepted. If the value is greater than zero, processing continues when
- PCRE2_SUBSTITUTE_GLOBAL is set. Otherwise (the value is less than zero
- or PCRE2_SUBSTITUTE_GLOBAL is not set), the the rest of the input is
- copied to the output and the call to pcre2_substitute() exits, return-
+ If the value is zero, the replacement is accepted, and, if PCRE2_SUB-
+ STITUTE_GLOBAL is set, processing continues with a search for the next
+ match. If the value is not zero, the current replacement is not ac-
+ cepted. If the value is greater than zero, processing continues when
+ PCRE2_SUBSTITUTE_GLOBAL is set. Otherwise (the value is less than zero
+ or PCRE2_SUBSTITUTE_GLOBAL is not set), the the rest of the input is
+ copied to the output and the call to pcre2_substitute() exits, return-
ing the number of matches so far.
@@ -3545,56 +3548,56 @@ DUPLICATE CAPTURE GROUP NAMES
int pcre2_substring_nametable_scan(const pcre2_code *code,
PCRE2_SPTR name, PCRE2_SPTR *first, PCRE2_SPTR *last);
- When a pattern is compiled with the PCRE2_DUPNAMES option, names for
- capture groups are not required to be unique. Duplicate names are al-
- ways allowed for groups with the same number, created by using the (?|
+ When a pattern is compiled with the PCRE2_DUPNAMES option, names for
+ capture groups are not required to be unique. Duplicate names are al-
+ ways allowed for groups with the same number, created by using the (?|
feature. Indeed, if such groups are named, they are required to use the
same names.
- Normally, patterns that use duplicate names are such that in any one
- match, only one of each set of identically-named groups participates.
+ Normally, patterns that use duplicate names are such that in any one
+ match, only one of each set of identically-named groups participates.
An example is shown in the pcre2pattern documentation.
- When duplicates are present, pcre2_substring_copy_byname() and
- pcre2_substring_get_byname() return the first substring corresponding
- to the given name that is set. Only if none are set is PCRE2_ERROR_UN-
- SET is returned. The pcre2_substring_number_from_name() function re-
- turns the error PCRE2_ERROR_NOUNIQUESUBSTRING when there are duplicate
+ When duplicates are present, pcre2_substring_copy_byname() and
+ pcre2_substring_get_byname() return the first substring corresponding
+ to the given name that is set. Only if none are set is PCRE2_ERROR_UN-
+ SET is returned. The pcre2_substring_number_from_name() function re-
+ turns the error PCRE2_ERROR_NOUNIQUESUBSTRING when there are duplicate
names.
- If you want to get full details of all captured substrings for a given
- name, you must use the pcre2_substring_nametable_scan() function. The
- first argument is the compiled pattern, and the second is the name. If
- the third and fourth arguments are NULL, the function returns a group
+ If you want to get full details of all captured substrings for a given
+ name, you must use the pcre2_substring_nametable_scan() function. The
+ first argument is the compiled pattern, and the second is the name. If
+ the third and fourth arguments are NULL, the function returns a group
number for a unique name, or PCRE2_ERROR_NOUNIQUESUBSTRING otherwise.
When the third and fourth arguments are not NULL, they must be pointers
- to variables that are updated by the function. After it has run, they
+ to variables that are updated by the function. After it has run, they
point to the first and last entries in the name-to-number table for the
- given name, and the function returns the length of each entry in code
- units. In both cases, PCRE2_ERROR_NOSUBSTRING is returned if there are
+ given name, and the function returns the length of each entry in code
+ units. In both cases, PCRE2_ERROR_NOSUBSTRING is returned if there are
no entries for the given name.
The format of the name table is described above in the section entitled
- Information about a pattern. Given all the relevant entries for the
- name, you can extract each of their numbers, and hence the captured
+ Information about a pattern. Given all the relevant entries for the
+ name, you can extract each of their numbers, and hence the captured
data.
FINDING ALL POSSIBLE MATCHES AT ONE POSITION
- The traditional matching function uses a similar algorithm to Perl,
- which stops when it finds the first match at a given point in the sub-
+ The traditional matching function uses a similar algorithm to Perl,
+ which stops when it finds the first match at a given point in the sub-
ject. If you want to find all possible matches, or the longest possible
- match at a given position, consider using the alternative matching
- function (see below) instead. If you cannot use the alternative func-
+ match at a given position, consider using the alternative matching
+ function (see below) instead. If you cannot use the alternative func-
tion, you can kludge it up by making use of the callout facility, which
is described in the pcre2callout documentation.
What you have to do is to insert a callout right at the end of the pat-
- tern. When your callout function is called, extract and save the cur-
- rent matched substring. Then return 1, which forces pcre2_match() to
- backtrack and try other alternatives. Ultimately, when it runs out of
+ tern. When your callout function is called, extract and save the cur-
+ rent matched substring. Then return 1, which forces pcre2_match() to
+ backtrack and try other alternatives. Ultimately, when it runs out of
matches, pcre2_match() will yield PCRE2_ERROR_NOMATCH.
@@ -3606,26 +3609,26 @@ MATCHING A PATTERN: THE ALTERNATIVE FUNCTION
pcre2_match_context *mcontext,
int *workspace, PCRE2_SIZE wscount);
- The function pcre2_dfa_match() is called to match a subject string
- against a compiled pattern, using a matching algorithm that scans the
+ The function pcre2_dfa_match() is called to match a subject string
+ against a compiled pattern, using a matching algorithm that scans the
subject string just once (not counting lookaround assertions), and does
- not backtrack. This has different characteristics to the normal algo-
- rithm, and is not compatible with Perl. Some of the features of PCRE2
- patterns are not supported. Nevertheless, there are times when this
- kind of matching can be useful. For a discussion of the two matching
+ not backtrack. This has different characteristics to the normal algo-
+ rithm, and is not compatible with Perl. Some of the features of PCRE2
+ patterns are not supported. Nevertheless, there are times when this
+ kind of matching can be useful. For a discussion of the two matching
algorithms, and a list of features that pcre2_dfa_match() does not sup-
port, see the pcre2matching documentation.
- The arguments for the pcre2_dfa_match() function are the same as for
+ The arguments for the pcre2_dfa_match() function are the same as for
pcre2_match(), plus two extras. The ovector within the match data block
is used in a different way, and this is described below. The other com-
- mon arguments are used in the same way as for pcre2_match(), so their
+ mon arguments are used in the same way as for pcre2_match(), so their
description is not repeated here.
- The two additional arguments provide workspace for the function. The
- workspace vector should contain at least 20 elements. It is used for
+ The two additional arguments provide workspace for the function. The
+ workspace vector should contain at least 20 elements. It is used for
keeping track of multiple paths through the pattern tree. More
- workspace is needed for patterns and subjects where there are a lot of
+ workspace is needed for patterns and subjects where there are a lot of
potential matches.
Here is an example of a simple call to pcre2_dfa_match():
@@ -3645,45 +3648,45 @@ MATCHING A PATTERN: THE ALTERNATIVE FUNCTION
Option bits for pcre_dfa_match()
- The unused bits of the options argument for pcre2_dfa_match() must be
- zero. The only bits that may be set are PCRE2_ANCHORED,
- PCRE2_COPY_MATCHED_SUBJECT, PCRE2_ENDANCHORED, PCRE2_NOTBOL, PCRE2_NO-
+ The unused bits of the options argument for pcre2_dfa_match() must be
+ zero. The only bits that may be set are PCRE2_ANCHORED,
+ PCRE2_COPY_MATCHED_SUBJECT, PCRE2_ENDANCHORED, PCRE2_NOTBOL, PCRE2_NO-
TEOL, PCRE2_NOTEMPTY, PCRE2_NOTEMPTY_ATSTART, PCRE2_NO_UTF_CHECK,
- PCRE2_PARTIAL_HARD, PCRE2_PARTIAL_SOFT, PCRE2_DFA_SHORTEST, and
- PCRE2_DFA_RESTART. All but the last four of these are exactly the same
+ PCRE2_PARTIAL_HARD, PCRE2_PARTIAL_SOFT, PCRE2_DFA_SHORTEST, and
+ PCRE2_DFA_RESTART. All but the last four of these are exactly the same
as for pcre2_match(), so their description is not repeated here.
PCRE2_PARTIAL_HARD
PCRE2_PARTIAL_SOFT
- These have the same general effect as they do for pcre2_match(), but
- the details are slightly different. When PCRE2_PARTIAL_HARD is set for
- pcre2_dfa_match(), it returns PCRE2_ERROR_PARTIAL if the end of the
+ These have the same general effect as they do for pcre2_match(), but
+ the details are slightly different. When PCRE2_PARTIAL_HARD is set for
+ pcre2_dfa_match(), it returns PCRE2_ERROR_PARTIAL if the end of the
subject is reached and there is still at least one matching possibility
that requires additional characters. This happens even if some complete
- matches have already been found. When PCRE2_PARTIAL_SOFT is set, the
- return code PCRE2_ERROR_NOMATCH is converted into PCRE2_ERROR_PARTIAL
- if the end of the subject is reached, there have been no complete
+ matches have already been found. When PCRE2_PARTIAL_SOFT is set, the
+ return code PCRE2_ERROR_NOMATCH is converted into PCRE2_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 por-
- tion of the string that was inspected when the longest partial match
+ tion of the string that was inspected when the longest partial match
was found is set as the first matching string in both cases. There is a
- more detailed discussion of partial and multi-segment matching, with
+ more detailed discussion of partial and multi-segment matching, with
examples, in the pcre2partial documentation.
PCRE2_DFA_SHORTEST
- Setting the PCRE2_DFA_SHORTEST option causes the matching algorithm to
+ Setting the PCRE2_DFA_SHORTEST option causes the matching algorithm to
stop as soon as it has found one match. Because of the way the alterna-
- tive algorithm works, this is necessarily the shortest possible match
+ tive algorithm works, this is necessarily the shortest possible match
at the first possible matching point in the subject string.
PCRE2_DFA_RESTART
- When pcre2_dfa_match() returns a partial match, it is possible to call
+ When pcre2_dfa_match() returns a partial match, it is possible to call
it again, with additional subject characters, and have it continue with
the same match. The PCRE2_DFA_RESTART option requests this action; when
- it is set, the workspace and wscount options must reference the same
- vector as before because data about the match so far is left in them
+ it is set, the workspace and wscount options must reference the same
+ vector as before because data about the match so far is left in them
after a partial match. There is more discussion of this facility in the
pcre2partial documentation.
@@ -3691,8 +3694,8 @@ MATCHING A PATTERN: THE ALTERNATIVE FUNCTION
When pcre2_dfa_match() succeeds, it may have matched more than one sub-
string in the subject. Note, however, that all the matches from one run
- of the function start at the same point in the subject. The shorter
- matches are all initial substrings of the longer matches. For example,
+ of the function start at the same point in the subject. The shorter
+ matches are all initial substrings of the longer matches. For example,
if the pattern
<.*>
@@ -3707,80 +3710,80 @@ MATCHING A PATTERN: THE ALTERNATIVE FUNCTION
<something> <something else>
<something>
- On success, the yield of the function is a number greater than zero,
- which is the number of matched substrings. The offsets of the sub-
- strings are returned in the ovector, and can be extracted by number in
- the same way as for pcre2_match(), but the numbers bear no relation to
- any capture groups that may exist in the pattern, because DFA matching
+ On success, the yield of the function is a number greater than zero,
+ which is the number of matched substrings. The offsets of the sub-
+ strings are returned in the ovector, and can be extracted by number in
+ the same way as for pcre2_match(), but the numbers bear no relation to
+ any capture groups that may exist in the pattern, because DFA matching
does not support capturing.
- Calls to the convenience functions that extract substrings by name re-
+ Calls to the convenience functions that extract substrings by name re-
turn the error PCRE2_ERROR_DFA_UFUNC (unsupported function) if used af-
- ter a DFA match. The convenience functions that extract substrings by
+ ter a DFA match. The convenience functions that extract substrings by
number never return PCRE2_ERROR_NOSUBSTRING.
- The matched strings are stored in the ovector in reverse order of
- length; that is, the longest matching string is first. If there were
- too many matches to fit into the ovector, the yield of the function is
+ The matched strings are stored in the ovector in reverse order of
+ length; that is, the longest matching string is first. If there were
+ too many matches to fit into the ovector, the yield of the function is
zero, and the vector is filled with the longest matches.
- NOTE: PCRE2's "auto-possessification" optimization usually applies to
- character repeats at the end of a pattern (as well as internally). For
- example, the pattern "a\d+" is compiled as if it were "a\d++". For DFA
- matching, this means that only one possible match is found. If you re-
+ NOTE: PCRE2's "auto-possessification" optimization usually applies to
+ character repeats at the end of a pattern (as well as internally). For
+ example, the pattern "a\d+" is compiled as if it were "a\d++". For DFA
+ matching, this means that only one possible match is found. If you re-
ally do want multiple matches in such cases, either use an ungreedy re-
- peat such as "a\d+?" or set the PCRE2_NO_AUTO_POSSESS option when com-
+ peat such as "a\d+?" or set the PCRE2_NO_AUTO_POSSESS option when com-
piling.
Error returns from pcre2_dfa_match()
The pcre2_dfa_match() function returns a negative number when it fails.
- Many of the errors are the same as for pcre2_match(), as described
+ Many of the errors are the same as for pcre2_match(), as described
above. There are in addition the following errors that are specific to
pcre2_dfa_match():
PCRE2_ERROR_DFA_UITEM
- This return is given if pcre2_dfa_match() encounters an item in the
- pattern that it does not support, for instance, the use of \C in a UTF
+ This return is given if pcre2_dfa_match() encounters an item in the
+ pattern that it does not support, for instance, the use of \C in a UTF
mode or a backreference.
PCRE2_ERROR_DFA_UCOND
- This return is given if pcre2_dfa_match() encounters a condition item
+ This return is given if pcre2_dfa_match() encounters a condition item
that uses a backreference for the condition, or a test for recursion in
a specific capture group. These are not supported.
PCRE2_ERROR_DFA_UINVALID_UTF
- This return is given if pcre2_dfa_match() is called for a pattern that
- was compiled with PCRE2_MATCH_INVALID_UTF. This is not supported for
+ This return is given if pcre2_dfa_match() is called for a pattern that
+ was compiled with PCRE2_MATCH_INVALID_UTF. This is not supported for
DFA matching.
PCRE2_ERROR_DFA_WSSIZE
- This return is given if pcre2_dfa_match() runs out of space in the
+ This return is given if pcre2_dfa_match() runs out of space in the
workspace vector.
PCRE2_ERROR_DFA_RECURSE
When a recursion or subroutine call is processed, the matching function
- calls itself recursively, using private memory for the ovector and
- workspace. This error is given if the internal ovector is not large
- enough. This should be extremely rare, as a vector of size 1000 is
+ calls itself recursively, using private memory for the ovector and
+ workspace. This error is given if the internal ovector is not large
+ enough. This should be extremely rare, as a vector of size 1000 is
used.
PCRE2_ERROR_DFA_BADRESTART
- When pcre2_dfa_match() is called with the PCRE2_DFA_RESTART option,
- some plausibility checks are made on the contents of the workspace,
- which should contain data about the previous partial match. If any of
+ When pcre2_dfa_match() is called with the PCRE2_DFA_RESTART option,
+ some plausibility checks are made on the contents of the workspace,
+ which should contain data about the previous partial match. If any of
these checks fail, this error is given.
SEE ALSO
- pcre2build(3), pcre2callout(3), pcre2demo(3), pcre2matching(3),
+ pcre2build(3), pcre2callout(3), pcre2demo(3), pcre2matching(3),
pcre2partial(3), pcre2posix(3), pcre2sample(3), pcre2unicode(3).
@@ -3793,7 +3796,7 @@ AUTHOR
REVISION
- Last updated: 19 March 2020
+ Last updated: 05 October 2020
Copyright (c) 1997-2020 University of Cambridge.
------------------------------------------------------------------------------
@@ -4831,10 +4834,10 @@ NAME
DIFFERENCES BETWEEN PCRE2 AND PERL
- This document describes the differences in the ways that PCRE2 and Perl
- handle regular expressions. The differences described here are with re-
- spect to Perl versions 5.26, but as both Perl and PCRE2 are continually
- changing, the information may sometimes be out of date.
+ This document describes some of the differences in the ways that PCRE2
+ and Perl handle regular expressions. The differences described here are
+ with respect to Perl version 5.32.0, but as both Perl and PCRE2 are
+ continually changing, the information may at times be out of date.
1. PCRE2 has only a subset of Perl's Unicode support. Details of what
it does have are given in the pcre2unicode page.
@@ -4845,40 +4848,43 @@ DIFFERENCES BETWEEN PCRE2 AND PERL
serts that the next character is not "a" three times (in principle;
PCRE2 optimizes this to run the assertion just once). Perl allows some
repeat quantifiers on other assertions, for example, \b* (but not
- \b{3}), but these do not seem to have any use.
+ \b{3}, though oddly it does allow ^{3}), but these do not seem to have
+ any use. PCRE2 does not allow any kind of quantifier on non-lookaround
+ assertions.
3. Capture groups that occur inside negative lookaround assertions are
counted, but their entries in the offsets vector are set only when a
negative assertion is a condition that has a matching branch (that is,
- the condition is false).
+ the condition is false). Perl may set such capture groups in other
+ circumstances.
- 4. The following Perl escape sequences are not supported: \F, \l, \L,
+ 4. The following Perl escape sequences are not supported: \F, \l, \L,
\u, \U, and \N when followed by a character name. \N on its own, match-
- ing a non-newline character, and \N{U+dd..}, matching a Unicode code
- point, are supported. The escapes that modify the case of following
- letters are implemented by Perl's general string-handling and are not
+ ing a non-newline character, and \N{U+dd..}, matching a Unicode code
+ point, are supported. The escapes that modify the case of following
+ letters are implemented by Perl's general string-handling and are not
part of its pattern matching engine. If any of these are encountered by
- PCRE2, an error is generated by default. However, if either of the
- PCRE2_ALT_BSUX or PCRE2_EXTRA_ALT_BSUX options is set, \U and \u are
+ PCRE2, an error is generated by default. However, if either of the
+ PCRE2_ALT_BSUX or PCRE2_EXTRA_ALT_BSUX options is set, \U and \u are
interpreted as ECMAScript interprets them.
5. The Perl escape sequences \p, \P, and \X are supported only if PCRE2
is built with Unicode support (the default). The properties that can be
- tested with \p and \P are limited to the general category properties
- such as Lu and Nd, script names such as Greek or Han, and the derived
- properties Any and L&. PCRE2 does support the Cs (surrogate) property,
- which Perl does not; the Perl documentation says "Because Perl hides
- the need for the user to understand the internal representation of Uni-
- code characters, there is no need to implement the somewhat messy con-
- cept of surrogates."
+ tested with \p and \P are limited to the general category properties
+ such as Lu and Nd, script names such as Greek or Han, and the derived
+ properties Any and L&. Both PCRE2 and Perl support the Cs (surrogate)
+ property, but in PCRE2 its use is limited. See the pcre2pattern docu-
+ mentation for details. The long synonyms for property names that Perl
+ supports (such as \p{Letter}) are not supported by PCRE2, nor is it
+ permitted to prefix any of these properties with "Is".
6. PCRE2 supports the \Q...\E escape for quoting substrings. Characters
in between are treated as literals. However, this is slightly different
- from Perl in that $ and @ are also handled as literals inside the
+ from Perl in that $ and @ are also handled as literals inside the
quotes. In Perl, they cause variable interpolation (but of course PCRE2
does not have variables). Also, Perl does "double-quotish backslash in-
terpolation" on any backslashes between \Q and \E which, its documenta-
- tion says, "may lead to confusing results". PCRE2 treats a backslash
+ tion says, "may lead to confusing results". PCRE2 treats a backslash
between \Q and \E just like any other character. Note the following ex-
amples:
@@ -4891,78 +4897,79 @@ DIFFERENCES BETWEEN PCRE2 AND PERL
\QA\B\E A\B A\B
\Q\\E \ \\E
- The \Q...\E sequence is recognized both inside and outside character
- classes.
+ The \Q...\E sequence is recognized both inside and outside character
+ classes by both PCRE2 and Perl.
- 7. Fairly obviously, PCRE2 does not support the (?{code}) and
+ 7. Fairly obviously, PCRE2 does not support the (?{code}) and
(??{code}) constructions. However, PCRE2 does have a "callout" feature,
which allows an external function to be called during pattern matching.
See the pcre2callout documentation for details.
- 8. Subroutine calls (whether recursive or not) were treated as atomic
- groups up to PCRE2 release 10.23, but from release 10.30 this changed,
+ 8. Subroutine calls (whether recursive or not) were treated as atomic
+ groups up to PCRE2 release 10.23, but from release 10.30 this changed,
and backtracking into subroutine calls is now supported, as in Perl.
- 9. If any of the backtracking control verbs are used in a group that is
- called as a subroutine (whether or not recursively), their effect is
- confined to that group; it does not extend to the surrounding pattern.
- This is not always the case in Perl. In particular, if (*THEN) is
- present in a group that is called as a subroutine, its action is lim-
- ited to that group, even if the group does not contain any | charac-
- ters. Note that such groups are processed as anchored at the point
- where they are tested.
-
- 10. If a pattern contains more than one backtracking control verb, the
- first one that is backtracked onto acts. For example, in the pattern
- A(*COMMIT)B(*PRUNE)C a failure in B triggers (*COMMIT), but a failure
+ 9. In PCRE2, if any of the backtracking control verbs are used in a
+ group that is called as a subroutine (whether or not recursively),
+ their effect is confined to that group; it does not extend to the sur-
+ rounding pattern. This is not always the case in Perl. In particular,
+ if (*THEN) is present in a group that is called as a subroutine, its
+ action is limited to that group, even if the group does not contain any
+ | characters. Note that such groups are processed as anchored at the
+ point where they are tested.
+
+ 10. If a pattern contains more than one backtracking control verb, the
+ first one that is backtracked onto acts. For example, in the pattern
+ A(*COMMIT)B(*PRUNE)C a failure in B triggers (*COMMIT), but a failure
in C triggers (*PRUNE). Perl's behaviour is more complex; in many cases
it is the same as PCRE2, but there are cases where it differs.
- 11. Most backtracking verbs in assertions have their normal actions.
- They are not confined to the assertion.
-
- 12. There are some differences that are concerned with the settings of
+ 11. There are some differences that are concerned with the settings of
captured strings when part of a pattern is repeated. For example,
matching "aba" against the pattern /^(a(b)?)+$/ in Perl leaves $2 un-
set, but in PCRE2 it is set to "b".
- 13. PCRE2's handling of duplicate capture group numbers and names is
+ 12. PCRE2's handling of duplicate capture group numbers and names is
not as general as Perl's. This is a consequence of the fact the PCRE2
works internally just with numbers, using an external table to trans-
late between numbers and names. In particular, a pattern such as
- (?|(?<a>A)|(?<b>B), where the two capture groups have the same number
+ (?|(?<a>A)|(?<b>B)), where the two capture groups have the same number
but different names, is not supported, and causes an error at compile
time. If it were allowed, it would not be possible to distinguish which
group matched, because both names map to capture group number 1. To
avoid this confusing situation, an error is given at compile time.
- 14. Perl used to recognize comments in some places that PCRE2 does not,
+ 13. Perl used to recognize comments in some places that PCRE2 does not,
for example, between the ( and ? at the start of a group. If the /x
modifier is set, Perl allowed white space between ( and ? though the
latest Perls give an error (for a while it was just deprecated). There
may still be some cases where Perl behaves differently.
- 15. Perl, when in warning mode, gives warnings for character classes
+ 14. Perl, when in warning mode, gives warnings for character classes
such as [A-\d] or [a-[:digit:]]. It then treats the hyphens as liter-
als. PCRE2 has no warning features, so it gives an error in these cases
because they are almost certainly user mistakes.
- 16. In PCRE2, the upper/lower case character properties Lu and Ll are
+ 15. In PCRE2, the upper/lower case character properties Lu and Ll are
not affected when case-independent matching is specified. For example,
\p{Lu} always matches an upper case letter. I think Perl has changed in
- this respect; in the release at the time of writing (5.24), \p{Lu} and
+ this respect; in the release at the time of writing (5.32), \p{Lu} and
\p{Ll} match all letters, regardless of case, when case independence is
specified.
+ 16. From release 5.32.0, Perl locks out the use of \K in lookaround as-
+ sertions. In PCRE2, \K is acted on when it occurs in positive asser-
+ tions, but is ignored in negative assertions.
+
17. PCRE2 provides some extensions to the Perl regular expression fa-
- cilities. Perl 5.10 includes new features that are not in earlier ver-
- sions of Perl, some of which (such as named parentheses) were in PCRE2
- for some time before. This list is with respect to Perl 5.26:
+ cilities. Perl 5.10 included new features that were not in earlier
+ versions of Perl, some of which (such as named parentheses) were in
+ PCRE2 for some time before. This list is with respect to Perl 5.32:
(a) Although lookbehind assertions in PCRE2 must match fixed length
- strings, each alternative branch of a lookbehind assertion can match a
- different length of string. Perl requires them all to have the same
- length.
+ strings, each alternative toplevel branch of a lookbehind assertion can
+ match a different length of string. Perl requires them all to have the
+ same length.
(b) From PCRE2 10.23, backreferences to groups of fixed length are sup-
ported in lookbehinds, provided that there is no possibility of refer-
@@ -4997,7 +5004,7 @@ DIFFERENCES BETWEEN PCRE2 AND PERL
different way and is not Perl-compatible.
(l) PCRE2 recognizes some special sequences such as (*CR) or (*NO_JIT)
- at the start of a pattern that set overall options that cannot be
+ at the start of a pattern. These set overall options that cannot be
changed within the pattern.
(m) PCRE2 supports non-atomic positive lookaround assertions. This is
@@ -5026,7 +5033,7 @@ AUTHOR
REVISION
- Last updated: 13 July 2019
+ Last updated: 06 October 2020
Copyright (c) 1997-2019 University of Cambridge.
------------------------------------------------------------------------------
@@ -6353,8 +6360,12 @@ CHARACTERS AND METACHARACTERS
The quick brown fox
matches a portion of a subject string that is identical to itself. When
- caseless matching is specified (the PCRE2_CASELESS option), letters are
- matched independently of case.
+ caseless matching is specified (the PCRE2_CASELESS option or (?i)
+ within the pattern), letters are matched independently of case. Note
+ that there are two ASCII characters, K and S, that, in addition to
+ their lower case ASCII equivalents, are case-equivalent with Unicode
+ U+212A (Kelvin sign) and U+017F (long S) respectively when either
+ PCRE2_UTF or PCRE2_UCP is set.
The power of regular expressions comes from the ability to include wild
cards, character classes, alternatives, and repetitions in the pattern.
@@ -6389,6 +6400,18 @@ CHARACTERS AND METACHARACTERS
[ POSIX character class (if followed by POSIX syntax)
] terminates the character class
+ If a pattern is compiled with the PCRE2_EXTENDED option, most white
+ space in the pattern, other than in a character class, and characters
+ between a # outside a character class and the next newline, inclusive,
+ are ignored. An escaping backslash can be used to include a white space
+ or a # character as part of the pattern. If the PCRE2_EXTENDED_MORE op-
+ tion is set, the same applies, but in addition unescaped space and hor-
+ izontal tab characters are ignored inside a character class. Note: only
+ these two characters are ignored, not the full set of pattern white
+ space characters that are ignored outside a character class. Option
+ settings can be changed within a pattern; see the section entitled "In-
+ ternal Option Setting" below.
+
The following sections describe the use of each of the metacharacters.
@@ -6406,15 +6429,9 @@ BACKSLASH
that it stands for itself. In particular, if you want to match a back-
slash, you write \\.
- In a UTF mode, only ASCII digits and letters have any special meaning
- after a backslash. All other characters (in particular, those whose
- code points are greater than 127) are treated as literals.
-
- If a pattern is compiled with the PCRE2_EXTENDED option, most white
- space in the pattern (other than in a character class), and characters
- between a # outside a character class and the next newline, inclusive,
- are ignored. An escaping backslash can be used to include a white space
- or # character as part of the pattern.
+ Only ASCII digits and letters have any special meaning after a back-
+ slash. All other characters (in particular, those whose code points are
+ greater than 127) are treated as literals.
If you want to treat all characters in a sequence as literals, you can
do so by putting them between \Q and \E. This is different from Perl in
@@ -7039,27 +7056,28 @@ BACKSLASH
matches "foobar", the first substring is still set to "foo".
- Perl documents that the use of \K within assertions is "not well de-
- fined". In PCRE2, \K is acted upon when it occurs inside positive as-
- sertions, but is ignored in negative assertions. Note that when a pat-
- tern such as (?=ab\K) matches, the reported start of the match can be
- greater than the end of the match. Using \K in a lookbehind assertion
- at the start of a pattern can also lead to odd effects. For example,
- consider this pattern:
+ Perl used to document that the use of \K within lookaround assertions
+ is "not well defined", but from version 5.32.0 Perl does not support
+ this usage at all. In PCRE2, \K is acted upon when it occurs inside
+ positive assertions, but is ignored in negative assertions. Note that
+ when a pattern such as (?=ab\K) matches, the reported start of the
+ match can be greater than the end of the match. Using \K in a lookbe-
+ hind assertion at the start of a pattern can also lead to odd effects.
+ For example, consider this pattern:
(?<=\Kfoo)bar
- If the subject is "foobar", a call to pcre2_match() with a starting
- offset of 3 succeeds and reports the matching string as "foobar", that
- is, the start of the reported match is earlier than where the match
+ If the subject is "foobar", a call to pcre2_match() with a starting
+ offset of 3 succeeds and reports the matching string as "foobar", that
+ is, the start of the reported match is earlier than where the match
started.
Simple assertions
- The final use of backslash is for certain simple assertions. An asser-
- tion specifies a condition that has to be met at a particular point in
- a match, without consuming any characters from the subject string. The
- use of groups for more complicated assertions is described below. The
+ The final use of backslash is for certain simple assertions. An asser-
+ tion specifies a condition that has to be met at a particular point in
+ a match, without consuming any characters from the subject string. The
+ use of groups for more complicated assertions is described below. The
backslashed assertions are:
\b matches at a word boundary
@@ -7070,191 +7088,191 @@ BACKSLASH
\z matches only at the end of the subject
\G matches at the first matching position in the subject
- Inside a character class, \b has a different meaning; it matches the
- backspace character. If any other of these assertions appears in a
+ Inside a character class, \b has a different meaning; it matches the
+ backspace character. If any other of these assertions appears in a
character class, an "invalid escape sequence" error is generated.
- A word boundary is a position in the subject string where the current
- character and the previous character do not both match \w or \W (i.e.
- one matches \w and the other matches \W), or the start or end of the
- string if the first or last character matches \w, respectively. When
- PCRE2 is built with Unicode support, the meanings of \w and \W can be
+ A word boundary is a position in the subject string where the current
+ character and the previous character do not both match \w or \W (i.e.
+ one matches \w and the other matches \W), or the start or end of the
+ string if the first or last character matches \w, respectively. When
+ PCRE2 is built with Unicode support, the meanings of \w and \W can be
changed by setting the PCRE2_UCP option. When this is done, it also af-
- fects \b and \B. Neither PCRE2 nor Perl has a separate "start of word"
- or "end of word" metasequence. However, whatever follows \b normally
- determines which it is. For example, the fragment \ba matches "a" at
+ fects \b and \B. Neither PCRE2 nor Perl has a separate "start of word"
+ or "end of word" metasequence. However, whatever follows \b normally
+ determines which it is. For example, the fragment \ba matches "a" at
the start of a word.
- The \A, \Z, and \z assertions differ from the traditional circumflex
+ The \A, \Z, and \z assertions differ from the traditional circumflex
and dollar (described in the next section) in that they only ever match
- at the very start and end of the subject string, whatever options are
- set. Thus, they are independent of multiline mode. These three asser-
- tions are not affected by the PCRE2_NOTBOL or PCRE2_NOTEOL options,
- which affect only the behaviour of the circumflex and dollar metachar-
- acters. However, if the startoffset argument of pcre2_match() is non-
- zero, indicating that matching is to start at a point other than the
- beginning of the subject, \A can never match. The difference between
- \Z and \z is that \Z matches before a newline at the end of the string
+ at the very start and end of the subject string, whatever options are
+ set. Thus, they are independent of multiline mode. These three asser-
+ tions are not affected by the PCRE2_NOTBOL or PCRE2_NOTEOL options,
+ which affect only the behaviour of the circumflex and dollar metachar-
+ acters. However, if the startoffset argument of pcre2_match() is non-
+ zero, indicating that matching is to start at a point other than the
+ beginning of the subject, \A can never match. The difference between
+ \Z and \z is that \Z matches before a newline at the end of the string
as well as at the very end, whereas \z matches only at the end.
- The \G assertion is true only when the current matching position is at
- the start point of the matching process, as specified by the startoff-
- set argument of pcre2_match(). It differs from \A when the value of
- startoffset is non-zero. By calling pcre2_match() multiple times with
- appropriate arguments, you can mimic Perl's /g option, and it is in
+ The \G assertion is true only when the current matching position is at
+ the start point of the matching process, as specified by the startoff-
+ set argument of pcre2_match(). It differs from \A when the value of
+ startoffset is non-zero. By calling pcre2_match() multiple times with
+ appropriate arguments, you can mimic Perl's /g option, and it is in
this kind of implementation where \G can be useful.
- Note, however, that PCRE2's implementation of \G, being true at the
- starting character of the matching process, is subtly different from
- Perl's, which defines it as true at the end of the previous match. In
- Perl, these can be different when the previously matched string was
+ Note, however, that PCRE2's implementation of \G, being true at the
+ starting character of the matching process, is subtly different from
+ Perl's, which defines it as true at the end of the previous match. In
+ Perl, these can be different when the previously matched string was
empty. Because PCRE2 does just one match at a time, it cannot reproduce
this behaviour.
- If all the alternatives of a pattern begin with \G, the expression is
+ If all the alternatives of a pattern begin with \G, the expression is
anchored to the starting match position, and the "anchored" flag is set
in the compiled regular expression.
CIRCUMFLEX AND DOLLAR
- The circumflex and dollar metacharacters are zero-width assertions.
- That is, they test for a particular condition being true without con-
+ The circumflex and dollar metacharacters are zero-width assertions.
+ That is, they test for a particular condition being true without con-
suming any characters from the subject string. These two metacharacters
- are concerned with matching the starts and ends of lines. If the new-
- line convention is set so that only the two-character sequence CRLF is
- recognized as a newline, isolated CR and LF characters are treated as
+ are concerned with matching the starts and ends of lines. If the new-
+ line convention is set so that only the two-character sequence CRLF is
+ recognized as a newline, isolated CR and LF characters are treated as
ordinary data characters, and are not recognized as newlines.
Outside a character class, in the default matching mode, the circumflex
- character is an assertion that is true only if the current matching
- point is at the start of the subject string. If the startoffset argu-
- ment of pcre2_match() is non-zero, or if PCRE2_NOTBOL is set, circum-
- flex can never match if the PCRE2_MULTILINE option is unset. Inside a
- character class, circumflex has an entirely different meaning (see be-
+ character is an assertion that is true only if the current matching
+ point is at the start of the subject string. If the startoffset argu-
+ ment of pcre2_match() is non-zero, or if PCRE2_NOTBOL is set, circum-
+ flex can never match if the PCRE2_MULTILINE option is unset. Inside a
+ character class, circumflex has an entirely different meaning (see be-
low).
- Circumflex need not be the first character of the pattern if a number
- of alternatives are involved, but it should be the first thing in each
- alternative in which it appears if the pattern is ever to match that
- branch. If all possible alternatives start with a circumflex, that is,
- if the pattern is constrained to match only at the start of the sub-
- ject, it is said to be an "anchored" pattern. (There are also other
+ Circumflex need not be the first character of the pattern if a number
+ of alternatives are involved, but it should be the first thing in each
+ alternative in which it appears if the pattern is ever to match that
+ branch. If all possible alternatives start with a circumflex, that is,
+ if the pattern is constrained to match only at the start of the sub-
+ ject, it is said to be an "anchored" pattern. (There are also other
constructs that can cause a pattern to be anchored.)
- The dollar character is an assertion that is true only if the current
- matching point is at the end of the subject string, or immediately be-
- fore a newline at the end of the string (by default), unless PCRE2_NO-
- TEOL is set. Note, however, that it does not actually match the new-
- line. Dollar need not be the last character of the pattern if a number
- of alternatives are involved, but it should be the last item in any
- branch in which it appears. Dollar has no special meaning in a charac-
+ The dollar character is an assertion that is true only if the current
+ matching point is at the end of the subject string, or immediately be-
+ fore a newline at the end of the string (by default), unless PCRE2_NO-
+ TEOL is set. Note, however, that it does not actually match the new-
+ line. Dollar need not be the last character of the pattern if a number
+ of alternatives are involved, but it should be the last item in any
+ branch in which it appears. Dollar has no special meaning in a charac-
ter class.
- The meaning of dollar can be changed so that it matches only at the
- very end of the string, by setting the PCRE2_DOLLAR_ENDONLY option at
+ The meaning of dollar can be changed so that it matches only at the
+ very end of the string, by setting the PCRE2_DOLLAR_ENDONLY option at
compile time. This does not affect the \Z assertion.
The meanings of the circumflex and dollar metacharacters are changed if
- the PCRE2_MULTILINE option is set. When this is the case, a dollar
- character matches before any newlines in the string, as well as at the
- very end, and a circumflex matches immediately after internal newlines
- as well as at the start of the subject string. It does not match after
- a newline that ends the string, for compatibility with Perl. However,
+ the PCRE2_MULTILINE option is set. When this is the case, a dollar
+ character matches before any newlines in the string, as well as at the
+ very end, and a circumflex matches immediately after internal newlines
+ as well as at the start of the subject string. It does not match after
+ a newline that ends the string, for compatibility with Perl. However,
this can be changed by setting the PCRE2_ALT_CIRCUMFLEX option.
- For example, the pattern /^abc$/ matches the subject string "def\nabc"
- (where \n represents a newline) in multiline mode, but not otherwise.
- Consequently, patterns that are anchored in single line mode because
- all branches start with ^ are not anchored in multiline mode, and a
- match for circumflex is possible when the startoffset argument of
- pcre2_match() is non-zero. The PCRE2_DOLLAR_ENDONLY option is ignored
+ For example, the pattern /^abc$/ matches the subject string "def\nabc"
+ (where \n represents a newline) in multiline mode, but not otherwise.
+ Consequently, patterns that are anchored in single line mode because
+ all branches start with ^ are not anchored in multiline mode, and a
+ match for circumflex is possible when the startoffset argument of
+ pcre2_match() is non-zero. The PCRE2_DOLLAR_ENDONLY option is ignored
if PCRE2_MULTILINE is set.
- When the newline convention (see "Newline conventions" below) recog-
- nizes the two-character sequence CRLF as a newline, this is preferred,
- even if the single characters CR and LF are also recognized as new-
- lines. For example, if the newline convention is "any", a multiline
- mode circumflex matches before "xyz" in the string "abc\r\nxyz" rather
- than after CR, even though CR on its own is a valid newline. (It also
+ When the newline convention (see "Newline conventions" below) recog-
+ nizes the two-character sequence CRLF as a newline, this is preferred,
+ even if the single characters CR and LF are also recognized as new-
+ lines. For example, if the newline convention is "any", a multiline
+ mode circumflex matches before "xyz" in the string "abc\r\nxyz" rather
+ than after CR, even though CR on its own is a valid newline. (It also
matches at the very start of the string, of course.)
- Note that the sequences \A, \Z, and \z can be used to match the start
- and end of the subject in both modes, and if all branches of a pattern
- start with \A it is always anchored, whether or not PCRE2_MULTILINE is
+ Note that the sequences \A, \Z, and \z can be used to match the start
+ and end of the subject in both modes, and if all branches of a pattern
+ start with \A it is always anchored, whether or not PCRE2_MULTILINE is
set.
FULL STOP (PERIOD, DOT) AND \N
Outside a character class, a dot in the pattern matches any one charac-
- ter in the subject string except (by default) a character that signi-
+ ter in the subject string except (by default) a character that signi-
fies the end of a line.
- When a line ending is defined as a single character, dot never matches
- that character; when the two-character sequence CRLF is used, dot does
- not match CR if it is immediately followed by LF, but otherwise it
- matches all characters (including isolated CRs and LFs). When any Uni-
- code line endings are being recognized, dot does not match CR or LF or
+ When a line ending is defined as a single character, dot never matches
+ that character; when the two-character sequence CRLF is used, dot does
+ not match CR if it is immediately followed by LF, but otherwise it
+ matches all characters (including isolated CRs and LFs). When any Uni-
+ code line endings are being recognized, dot does not match CR or LF or
any of the other line ending characters.
- The behaviour of dot with regard to newlines can be changed. If the
- PCRE2_DOTALL option is set, a dot matches any one character, without
- exception. If the two-character sequence CRLF is present in the sub-
+ The behaviour of dot with regard to newlines can be changed. If the
+ PCRE2_DOTALL option is set, a dot matches any one character, without
+ exception. If the two-character sequence CRLF is present in the sub-
ject string, it takes two dots to match it.
- The handling of dot is entirely independent of the handling of circum-
- flex and dollar, the only relationship being that they both involve
+ The handling of dot is entirely independent of the handling of circum-
+ flex and dollar, the only relationship being that they both involve
newlines. Dot has no special meaning in a character class.
- The escape sequence \N when not followed by an opening brace behaves
- like a dot, except that it is not affected by the PCRE2_DOTALL option.
- In other words, it matches any character except one that signifies the
+ The escape sequence \N when not followed by an opening brace behaves
+ like a dot, except that it is not affected by the PCRE2_DOTALL option.
+ In other words, it matches any character except one that signifies the
end of a line.
When \N is followed by an opening brace it has a different meaning. See
- the section entitled "Non-printing characters" above for details. Perl
- also uses \N{name} to specify characters by Unicode name; PCRE2 does
+ the section entitled "Non-printing characters" above for details. Perl
+ also uses \N{name} to specify characters by Unicode name; PCRE2 does
not support this.
MATCHING A SINGLE CODE UNIT
- Outside a character class, the escape sequence \C matches any one code
- unit, whether or not a UTF mode is set. In the 8-bit library, one code
- unit is one byte; in the 16-bit library it is a 16-bit unit; in the
- 32-bit library it is a 32-bit unit. Unlike a dot, \C always matches
- line-ending characters. The feature is provided in Perl in order to
+ Outside a character class, the escape sequence \C matches any one code
+ unit, whether or not a UTF mode is set. In the 8-bit library, one code
+ unit is one byte; in the 16-bit library it is a 16-bit unit; in the
+ 32-bit library it is a 32-bit unit. Unlike a dot, \C always matches
+ line-ending characters. The feature is provided in Perl in order to
match individual bytes in UTF-8 mode, but it is unclear how it can use-
fully be used.
- Because \C breaks up characters into individual code units, matching
- one unit with \C in UTF-8 or UTF-16 mode means that the rest of the
+ Because \C breaks up characters into individual code units, matching
+ one unit with \C in UTF-8 or UTF-16 mode means that the rest of the
string may start with a malformed UTF character. This has undefined re-
sults, because PCRE2 assumes that it is matching character by character
in a valid UTF string (by default it checks the subject string's valid-
- ity at the start of processing unless the PCRE2_NO_UTF_CHECK or
+ ity at the start of processing unless the PCRE2_NO_UTF_CHECK or
PCRE2_MATCH_INVALID_UTF option is used).
- An application can lock out the use of \C by setting the
- PCRE2_NEVER_BACKSLASH_C option when compiling a pattern. It is also
+ An application can lock out the use of \C by setting the
+ PCRE2_NEVER_BACKSLASH_C option when compiling a pattern. It is also
possible to build PCRE2 with the use of \C permanently disabled.
- PCRE2 does not allow \C to appear in lookbehind assertions (described
- below) in UTF-8 or UTF-16 modes, because this would make it impossible
- to calculate the length of the lookbehind. Neither the alternative
+ PCRE2 does not allow \C to appear in lookbehind assertions (described
+ below) in UTF-8 or UTF-16 modes, because this would make it impossible
+ to calculate the length of the lookbehind. Neither the alternative
matching function pcre2_dfa_match() nor the JIT optimizer support \C in
these UTF modes. The former gives a match-time error; the latter fails
to optimize and so the match is always run using the interpreter.
- In the 32-bit library, however, \C is always supported (when not ex-
- plicitly locked out) because it always matches a single code unit,
+ In the 32-bit library, however, \C is always supported (when not ex-
+ plicitly locked out) because it always matches a single code unit,
whether or not UTF-32 is specified.
In general, the \C escape sequence is best avoided. However, one way of
- using it that avoids the problem of malformed UTF-8 or UTF-16 charac-
- ters is to use a lookahead to check the length of the next character,
- as in this pattern, which could be used with a UTF-8 string (ignore
+ using it that avoids the problem of malformed UTF-8 or UTF-16 charac-
+ ters is to use a lookahead to check the length of the next character,
+ as in this pattern, which could be used with a UTF-8 string (ignore
white space and line breaks):
(?| (?=[\x00-\x7f])(\C) |
@@ -7262,11 +7280,11 @@ MATCHING A SINGLE CODE UNIT
(?=[\x{800}-\x{ffff}])(\C)(\C)(\C) |
(?=[\x{10000}-\x{1fffff}])(\C)(\C)(\C)(\C))
- In this example, a group that starts with (?| resets the capturing
- parentheses numbers in each alternative (see "Duplicate Group Numbers"
+ In this example, a group that starts with (?| resets the capturing
+ parentheses numbers in each alternative (see "Duplicate Group Numbers"
below). The assertions at the start of each branch check the next UTF-8
- character for values whose encoding uses 1, 2, 3, or 4 bytes, respec-
- tively. The character's individual bytes are then captured by the ap-
+ character for values whose encoding uses 1, 2, 3, or 4 bytes, respec-
+ tively. The character's individual bytes are then captured by the ap-
propriate number of \C groups.
@@ -7274,34 +7292,37 @@ SQUARE BRACKETS AND CHARACTER CLASSES
An opening square bracket introduces a character class, terminated by a
closing square bracket. A closing square bracket on its own is not spe-
- cial by default. If a closing square bracket is required as a member
+ cial by default. If a closing square bracket is required as a member
of the class, it should be the first data character in the class (after
- an initial circumflex, if present) or escaped with a backslash. This
- means that, by default, an empty class cannot be defined. However, if
- the PCRE2_ALLOW_EMPTY_CLASS option is set, a closing square bracket at
+ an initial circumflex, if present) or escaped with a backslash. This
+ means that, by default, an empty class cannot be defined. However, if
+ the PCRE2_ALLOW_EMPTY_CLASS option is set, a closing square bracket at
the start does end the (empty) class.
- A character class matches a single character in the subject. A matched
+ A character class matches a single character in the subject. A matched
character must be in the set of characters defined by the class, unless
- the first character in the class definition is a circumflex, in which
+ the first character in the class definition is a circumflex, in which
case the subject character must not be in the set defined by the class.
- If a circumflex is actually required as a member of the class, ensure
+ If a circumflex is actually required as a member of the class, ensure
it is not the first character, or escape it with a backslash.
- For example, the character class [aeiou] matches any lower case vowel,
- while [^aeiou] matches any character that is not a lower case vowel.
+ For example, the character class [aeiou] matches any lower case vowel,
+ while [^aeiou] matches any character that is not a lower case vowel.
Note that a circumflex is just a convenient notation for specifying the
- characters that are in the class by enumerating those that are not. A
- class that starts with a circumflex is not an assertion; it still con-
- sumes a character from the subject string, and therefore it fails if
+ characters that are in the class by enumerating those that are not. A
+ class that starts with a circumflex is not an assertion; it still con-
+ sumes a character from the subject string, and therefore it fails if
the current pointer is at the end of the string.
- Characters in a class may be specified by their code points using \o,
- \x, or \N{U+hh..} in the usual way. When caseless matching is set, any
- letters in a class represent both their upper case and lower case ver-
- sions, so for example, a caseless [aeiou] matches "A" as well as "a",
- and a caseless [^aeiou] does not match "A", whereas a caseful version
- would.
+ Characters in a class may be specified by their code points using \o,
+ \x, or \N{U+hh..} in the usual way. When caseless matching is set, any
+ letters in a class represent both their upper case and lower case ver-
+ sions, so for example, a caseless [aeiou] matches "A" as well as "a",
+ and a caseless [^aeiou] does not match "A", whereas a caseful version
+ would. Note that there are two ASCII characters, K and S, that, in ad-
+ dition to their lower case ASCII equivalents, are case-equivalent with
+ Unicode U+212A (Kelvin sign) and U+017F (long S) respectively when ei-
+ ther PCRE2_UTF or PCRE2_UCP is set.
Characters that might indicate line breaks are never treated in any
special way when matching character classes, whatever line-ending se-
@@ -9559,7 +9580,7 @@ AUTHOR
REVISION
- Last updated: 24 February 2020
+ Last updated: 06 October 2020
Copyright (c) 1997-2020 University of Cambridge.
------------------------------------------------------------------------------
diff --git a/doc/pcre2compat.3 b/doc/pcre2compat.3
index b4209db..862d28d 100644
--- a/doc/pcre2compat.3
+++ b/doc/pcre2compat.3
@@ -1,13 +1,13 @@
-.TH PCRE2COMPAT 3 "13 July 2019" "PCRE2 10.34"
+.TH PCRE2COMPAT 3 "06 October 2020" "PCRE2 10.36"
.SH NAME
PCRE2 - Perl-compatible regular expressions (revised API)
.SH "DIFFERENCES BETWEEN PCRE2 AND PERL"
.rs
.sp
-This document describes the differences in the ways that PCRE2 and Perl handle
-regular expressions. The differences described here are with respect to Perl
-versions 5.26, but as both Perl and PCRE2 are continually changing, the
-information may sometimes be out of date.
+This document describes some of the differences in the ways that PCRE2 and Perl
+handle regular expressions. The differences described here are with respect to
+Perl version 5.32.0, but as both Perl and PCRE2 are continually changing, the
+information may at times be out of date.
.P
1. PCRE2 has only a subset of Perl's Unicode support. Details of what it does
have are given in the
@@ -21,11 +21,14 @@ they do not mean what you might think. For example, (?!a){3} does not assert
that the next three characters are not "a". It just asserts that the next
character is not "a" three times (in principle; PCRE2 optimizes this to run the
assertion just once). Perl allows some repeat quantifiers on other assertions,
-for example, \eb* (but not \eb{3}), but these do not seem to have any use.
+for example, \eb* (but not \eb{3}, though oddly it does allow ^{3}), but these
+do not seem to have any use. PCRE2 does not allow any kind of quantifier on
+non-lookaround assertions.
.P
3. Capture groups that occur inside negative lookaround assertions are counted,
but their entries in the offsets vector are set only when a negative assertion
-is a condition that has a matching branch (that is, the condition is false).
+is a condition that has a matching branch (that is, the condition is false).
+Perl may set such capture groups in other circumstances.
.P
4. The following Perl escape sequences are not supported: \eF, \el, \eL, \eu,
\eU, and \eN when followed by a character name. \eN on its own, matching a
@@ -41,10 +44,14 @@ interprets them.
built with Unicode support (the default). The properties that can be tested
with \ep and \eP are limited to the general category properties such as Lu and
Nd, script names such as Greek or Han, and the derived properties Any and L&.
-PCRE2 does support the Cs (surrogate) property, which Perl does not; the Perl
-documentation says "Because Perl hides the need for the user to understand the
-internal representation of Unicode characters, there is no need to implement
-the somewhat messy concept of surrogates."
+Both PCRE2 and Perl support the Cs (surrogate) property, but in PCRE2 its use
+is limited. See the
+.\" HREF
+\fBpcre2pattern\fP
+.\"
+documentation for details. The long synonyms for property names that Perl
+supports (such as \ep{Letter}) are not supported by PCRE2, nor is it permitted
+to prefix any of these properties with "Is".
.P
6. PCRE2 supports the \eQ...\eE escape for quoting substrings. Characters
in between are treated as literals. However, this is slightly different from
@@ -65,7 +72,8 @@ other character. Note the following examples:
\eQA\eB\eE A\eB A\eB
\eQ\e\eE \e \e\eE
.sp
-The \eQ...\eE sequence is recognized both inside and outside character classes.
+The \eQ...\eE sequence is recognized both inside and outside character classes
+by both PCRE2 and Perl.
.P
7. Fairly obviously, PCRE2 does not support the (?{code}) and (??{code})
constructions. However, PCRE2 does have a "callout" feature, which allows an
@@ -79,13 +87,13 @@ documentation for details.
to PCRE2 release 10.23, but from release 10.30 this changed, and backtracking
into subroutine calls is now supported, as in Perl.
.P
-9. If any of the backtracking control verbs are used in a group that is called
-as a subroutine (whether or not recursively), their effect is confined to that
-group; it does not extend to the surrounding pattern. This is not always the
-case in Perl. In particular, if (*THEN) is present in a group that is called as
-a subroutine, its action is limited to that group, even if the group does not
-contain any | characters. Note that such groups are processed as anchored
-at the point where they are tested.
+9. In PCRE2, if any of the backtracking control verbs are used in a group that
+is called as a subroutine (whether or not recursively), their effect is
+confined to that group; it does not extend to the surrounding pattern. This is
+not always the case in Perl. In particular, if (*THEN) is present in a group
+that is called as a subroutine, its action is limited to that group, even if
+the group does not contain any | characters. Note that such groups are
+processed as anchored at the point where they are tested.
.P
10. If a pattern contains more than one backtracking control verb, the first
one that is backtracked onto acts. For example, in the pattern
@@ -93,48 +101,49 @@ A(*COMMIT)B(*PRUNE)C a failure in B triggers (*COMMIT), but a failure in C
triggers (*PRUNE). Perl's behaviour is more complex; in many cases it is the
same as PCRE2, but there are cases where it differs.
.P
-11. Most backtracking verbs in assertions have their normal actions. They are
-not confined to the assertion.
-.P
-12. There are some differences that are concerned with the settings of captured
+11. There are some differences that are concerned with the settings of captured
strings when part of a pattern is repeated. For example, matching "aba" against
the pattern /^(a(b)?)+$/ in Perl leaves $2 unset, but in PCRE2 it is set to
"b".
.P
-13. PCRE2's handling of duplicate capture group numbers and names is not as
+12. PCRE2's handling of duplicate capture group numbers and names is not as
general as Perl's. This is a consequence of the fact the PCRE2 works internally
just with numbers, using an external table to translate between numbers and
-names. In particular, a pattern such as (?|(?<a>A)|(?<b>B), where the two
+names. In particular, a pattern such as (?|(?<a>A)|(?<b>B)), where the two
capture groups have the same number but different names, is not supported, and
causes an error at compile time. If it were allowed, it would not be possible
to distinguish which group matched, because both names map to capture group
number 1. To avoid this confusing situation, an error is given at compile time.
.P
-14. Perl used to recognize comments in some places that PCRE2 does not, for
+13. Perl used to recognize comments in some places that PCRE2 does not, for
example, between the ( and ? at the start of a group. If the /x modifier is
set, Perl allowed white space between ( and ? though the latest Perls give an
error (for a while it was just deprecated). There may still be some cases where
Perl behaves differently.
.P
-15. Perl, when in warning mode, gives warnings for character classes such as
+14. Perl, when in warning mode, gives warnings for character classes such as
[A-\ed] or [a-[:digit:]]. It then treats the hyphens as literals. PCRE2 has no
warning features, so it gives an error in these cases because they are almost
certainly user mistakes.
.P
-16. In PCRE2, the upper/lower case character properties Lu and Ll are not
+15. In PCRE2, the upper/lower case character properties Lu and Ll are not
affected when case-independent matching is specified. For example, \ep{Lu}
always matches an upper case letter. I think Perl has changed in this respect;
-in the release at the time of writing (5.24), \ep{Lu} and \ep{Ll} match all
+in the release at the time of writing (5.32), \ep{Lu} and \ep{Ll} match all
letters, regardless of case, when case independence is specified.
.P
+16. From release 5.32.0, Perl locks out the use of \eK in lookaround
+assertions. In PCRE2, \eK is acted on when it occurs in positive assertions,
+but is ignored in negative assertions.
+.P
17. PCRE2 provides some extensions to the Perl regular expression facilities.
-Perl 5.10 includes new features that are not in earlier versions of Perl, some
+Perl 5.10 included new features that were not in earlier versions of Perl, some
of which (such as named parentheses) were in PCRE2 for some time before. This
-list is with respect to Perl 5.26:
+list is with respect to Perl 5.32:
.sp
(a) Although lookbehind assertions in PCRE2 must match fixed length strings,
-each alternative branch of a lookbehind assertion can match a different length
-of string. Perl requires them all to have the same length.
+each alternative toplevel branch of a lookbehind assertion can match a
+different length of string. Perl requires them all to have the same length.
.sp
(b) From PCRE2 10.23, backreferences to groups of fixed length are supported
in lookbehinds, provided that there is no possibility of referencing a
@@ -168,7 +177,7 @@ variable interpolation, but not general hooks on every match.
different way and is not Perl-compatible.
.sp
(l) PCRE2 recognizes some special sequences such as (*CR) or (*NO_JIT) at
-the start of a pattern that set overall options that cannot be changed within
+the start of a pattern. These set overall options that cannot be changed within
the pattern.
.sp
(m) PCRE2 supports non-atomic positive lookaround assertions. This is an
@@ -203,6 +212,6 @@ Cambridge, England.
.rs
.sp
.nf
-Last updated: 13 July 2019
+Last updated: 06 October 2020
Copyright (c) 1997-2019 University of Cambridge.
.fi
diff --git a/doc/pcre2pattern.3 b/doc/pcre2pattern.3
index 47c0f31..93bacb6 100644
--- a/doc/pcre2pattern.3
+++ b/doc/pcre2pattern.3
@@ -1,4 +1,4 @@
-.TH PCRE2PATTERN 3 "05 October 2020" "PCRE2 10.35"
+.TH PCRE2PATTERN 3 "06 October 2020" "PCRE2 10.35"
.SH NAME
PCRE2 - Perl-compatible regular expressions (revised API)
.SH "PCRE2 REGULAR EXPRESSION DETAILS"
@@ -1168,8 +1168,9 @@ For example, when the pattern
.sp
matches "foobar", the first substring is still set to "foo".
.P
-Perl documents that the use of \eK within assertions is "not well defined". In
-PCRE2, \eK is acted upon when it occurs inside positive assertions, but is
+Perl used to document that the use of \eK within lookaround assertions is "not
+well defined", but from version 5.32.0 Perl does not support this usage at all.
+In PCRE2, \eK is acted upon when it occurs inside positive assertions, but is
ignored in negative assertions. Note that when a pattern such as (?=ab\eK)
matches, the reported start of the match can be greater than the end of the
match. Using \eK in a lookbehind assertion at the start of a pattern can also
@@ -3897,6 +3898,6 @@ Cambridge, England.
.rs
.sp
.nf
-Last updated: 05 October 2020
+Last updated: 06 October 2020
Copyright (c) 1997-2020 University of Cambridge.
.fi
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