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version 1.1.1.1, 2012/02/21 23:05:52	version 1.1.1.2, 2012/02/21 23:50:25
Line 19 man page, in case the conversion went wrong.	Line 19 man page, in case the conversion went wrong.
<li><a name="TOC4" href="#SEC4">BACKSLASH</a>	<li><a name="TOC4" href="#SEC4">BACKSLASH</a>
<li><a name="TOC5" href="#SEC5">CIRCUMFLEX AND DOLLAR</a>	<li><a name="TOC5" href="#SEC5">CIRCUMFLEX AND DOLLAR</a>
<li><a name="TOC6" href="#SEC6">FULL STOP (PERIOD, DOT) AND \N</a>	<li><a name="TOC6" href="#SEC6">FULL STOP (PERIOD, DOT) AND \N</a>
<li><a name="TOC7" href="#SEC7">MATCHING A SINGLE BYTE</a>	<li><a name="TOC7" href="#SEC7">MATCHING A SINGLE DATA UNIT</a>
<li><a name="TOC8" href="#SEC8">SQUARE BRACKETS AND CHARACTER CLASSES</a>	<li><a name="TOC8" href="#SEC8">SQUARE BRACKETS AND CHARACTER CLASSES</a>
<li><a name="TOC9" href="#SEC9">POSIX CHARACTER CLASSES</a>	<li><a name="TOC9" href="#SEC9">POSIX CHARACTER CLASSES</a>
<li><a name="TOC10" href="#SEC10">VERTICAL BAR</a>	<li><a name="TOC10" href="#SEC10">VERTICAL BAR</a>
Line 61 description of PCRE's regular expressions is intended	Line 61 description of PCRE's regular expressions is intended
</P>	</P>
<P>	<P>
The original operation of PCRE was on strings of one-byte characters. However,	The original operation of PCRE was on strings of one-byte characters. However,
there is now also support for UTF-8 character strings. To use this,	there is now also support for UTF-8 strings in the original library, and a
PCRE must be built to include UTF-8 support, and you must call	second library that supports 16-bit and UTF-16 character strings. To use these
<b>pcre_compile()</b> or <b>pcre_compile2()</b> with the PCRE_UTF8 option. There	features, PCRE must be built to include appropriate support. When using UTF
is also a special sequence that can be given at the start of a pattern:	strings you must either call the compiling function with the PCRE_UTF8 or
	PCRE_UTF16 option, or the pattern must start with one of these special
	sequences:
<pre>	<pre>
(*UTF8)	(*UTF8)
	(*UTF16)
</pre>	</pre>
Starting a pattern with this sequence is equivalent to setting the PCRE_UTF8	Starting a pattern with such a sequence is equivalent to setting the relevant
option. This feature is not Perl-compatible. How setting UTF-8 mode affects	option. This feature is not Perl-compatible. How setting a UTF mode affects
pattern matching is mentioned in several places below. There is also a summary	pattern matching is mentioned in several places below. There is also a summary
of UTF-8 features in the	of features in the
<a href="pcreunicode.html"><b>pcreunicode</b></a>	<a href="pcreunicode.html"><b>pcreunicode</b></a>
page.	page.
</P>	</P>
<P>	<P>
Another special sequence that may appear at the start of a pattern or in	Another special sequence that may appear at the start of a pattern or in
combination with (*UTF8) is:	combination with (UTF8) or (UTF16) is:
<pre>	<pre>
(*UCP)	(*UCP)
</pre>	</pre>
Line 94 of newlines; they are described below.	Line 97 of newlines; they are described below.
</P>	</P>
<P>	<P>
The remainder of this document discusses the patterns that are supported by	The remainder of this document discusses the patterns that are supported by
PCRE when its main matching function, <b>pcre_exec()</b>, is used.	PCRE when one its main matching functions, <b>pcre_exec()</b> (8-bit) or
From release 6.0, PCRE offers a second matching function,	<b>pcre16_exec()</b> (16-bit), is used. PCRE also has alternative matching
<b>pcre_dfa_exec()</b>, which matches using a different algorithm that is not	functions, <b>pcre_dfa_exec()</b> and <b>pcre16_dfa_exec()</b>, which match using
Perl-compatible. Some of the features discussed below are not available when	a different algorithm that is not Perl-compatible. Some of the features
<b>pcre_dfa_exec()</b> is used. The advantages and disadvantages of the	discussed below are not available when DFA matching is used. The advantages and
alternative function, and how it differs from the normal function, are	disadvantages of the alternative functions, and how they differ from the normal
discussed in the	functions, are discussed in the
<a href="pcrematching.html"><b>pcrematching</b></a>	<a href="pcrematching.html"><b>pcrematching</b></a>
page.	page.
<a name="newlines"></a></P>	<a name="newlines"></a></P>
Line 126 string with one of the following five sequences:	Line 129 string with one of the following five sequences:
(*ANYCRLF) any of the three above	(*ANYCRLF) any of the three above
(*ANY) all Unicode newline sequences	(*ANY) all Unicode newline sequences
</pre>	</pre>
These override the default and the options given to <b>pcre_compile()</b> or	These override the default and the options given to the compiling function. For
<b>pcre_compile2()</b>. For example, on a Unix system where LF is the default	example, on a Unix system where LF is the default newline sequence, the pattern
newline sequence, the pattern
<pre>	<pre>
(*CR)a.b	(*CR)a.b
</pre>	</pre>
Line 158 corresponding characters in the subject. As a trivial	Line 160 corresponding characters in the subject. As a trivial
</pre>	</pre>
matches a portion of a subject string that is identical to itself. When	matches a portion of a subject string that is identical to itself. When
caseless matching is specified (the PCRE_CASELESS option), letters are matched	caseless matching is specified (the PCRE_CASELESS option), letters are matched
independently of case. In UTF-8 mode, PCRE always understands the concept of	independently of case. In a UTF mode, PCRE always understands the concept of
case for characters whose values are less than 128, so caseless matching is	case for characters whose values are less than 128, so caseless matching is
always possible. For characters with higher values, the concept of case is	always possible. For characters with higher values, the concept of case is
supported if PCRE is compiled with Unicode property support, but not otherwise.	supported if PCRE is compiled with Unicode property support, but not otherwise.
If you want to use caseless matching for characters 128 and above, you must	If you want to use caseless matching for characters 128 and above, you must
ensure that PCRE is compiled with Unicode property support as well as with	ensure that PCRE is compiled with Unicode property support as well as with
UTF-8 support.	UTF support.
</P>	</P>
<P>	<P>
The power of regular expressions comes from the ability to include alternatives	The power of regular expressions comes from the ability to include alternatives
Line 220 non-alphanumeric with backslash to specify that it sta	Line 222 non-alphanumeric with backslash to specify that it sta
particular, if you want to match a backslash, you write \\.	particular, if you want to match a backslash, you write \\.
</P>	</P>
<P>	<P>
In UTF-8 mode, only ASCII numbers and letters have any special meaning after a	In a UTF mode, only ASCII numbers and letters have any special meaning after a
backslash. All other characters (in particular, those whose codepoints are	backslash. All other characters (in particular, those whose codepoints are
greater than 127) are treated as literals.	greater than 127) are treated as literals.
</P>	</P>
Line 276 is converted to upper case. Then bit 6 of the characte	Line 278 is converted to upper case. Then bit 6 of the characte
Thus \cz becomes hex 1A (z is 7A), but \c{ becomes hex 3B ({ is 7B), while	Thus \cz becomes hex 1A (z is 7A), but \c{ becomes hex 3B ({ is 7B), while
\c; becomes hex 7B (; is 3B). If the byte following \c has a value greater	\c; becomes hex 7B (; is 3B). If the byte following \c has a value greater
than 127, a compile-time error occurs. This locks out non-ASCII characters in	than 127, a compile-time error occurs. This locks out non-ASCII characters in
both byte mode and UTF-8 mode. (When PCRE is compiled in EBCDIC mode, all byte	all modes. (When PCRE is compiled in EBCDIC mode, all byte values are valid. A
values are valid. A lower case letter is converted to upper case, and then the	lower case letter is converted to upper case, and then the 0xc0 bits are
0xc0 bits are flipped.)	flipped.)
</P>	</P>
<P>	<P>
By default, after \x, from zero to two hexadecimal digits are read (letters	By default, after \x, from zero to two hexadecimal digits are read (letters
can be in upper or lower case). Any number of hexadecimal digits may appear	can be in upper or lower case). Any number of hexadecimal digits may appear
between \x{ and }, but the value of the character code must be less than 256	between \x{ and }, but the character code is constrained as follows:
in non-UTF-8 mode, and less than 2**31 in UTF-8 mode. That is, the maximum	<pre>
value in hexadecimal is 7FFFFFFF. Note that this is bigger than the largest	8-bit non-UTF mode less than 0x100
Unicode code point, which is 10FFFF.	8-bit UTF-8 mode less than 0x10ffff and a valid codepoint
	16-bit non-UTF mode less than 0x10000
	16-bit UTF-16 mode less than 0x10ffff and a valid codepoint
	</pre>
	Invalid Unicode codepoints are the range 0xd800 to 0xdfff (the so-called
	"surrogate" codepoints).
</P>	</P>
<P>	<P>
If characters other than hexadecimal digits appear between \x{ and }, or if	If characters other than hexadecimal digits appear between \x{ and }, or if
Line 328 following the discussion of	Line 335 following the discussion of
Inside a character class, or if the decimal number is greater than 9 and there	Inside a character class, or if the decimal number is greater than 9 and there
have not been that many capturing subpatterns, PCRE re-reads up to three octal	have not been that many capturing subpatterns, PCRE re-reads up to three octal
digits following the backslash, and uses them to generate a data character. Any	digits following the backslash, and uses them to generate a data character. Any
subsequent digits stand for themselves. In non-UTF-8 mode, the value of a	subsequent digits stand for themselves. The value of the character is
character specified in octal must be less than \400. In UTF-8 mode, values up	constrained in the same way as characters specified in hexadecimal.
to \777 are permitted. For example:	For example:
<pre>	<pre>
\040 is another way of writing a space	\040 is another way of writing a space
\40 is the same, provided there are fewer than 40 previous capturing subpatterns	\40 is the same, provided there are fewer than 40 previous capturing subpatterns
Line 339 to \777 are permitted. For example:	Line 346 to \777 are permitted. For example:
\011 is always a tab	\011 is always a tab
\0113 is a tab followed by the character "3"	\0113 is a tab followed by the character "3"
\113 might be a back reference, otherwise the character with octal code 113	\113 might be a back reference, otherwise the character with octal code 113
\377 might be a back reference, otherwise the byte consisting entirely of 1 bits	\377 might be a back reference, otherwise the value 255 (decimal)
\81 is either a back reference, or a binary zero followed by the two characters "8" and "1"	\81 is either a back reference, or a binary zero followed by the two characters "8" and "1"
</pre>	</pre>
Note that octal values of 100 or greater must not be introduced by a leading	Note that octal values of 100 or greater must not be introduced by a leading
Line 443 accented letters, and these are then matched by \w. Th	Line 450 accented letters, and these are then matched by \w. Th
Unicode is discouraged.	Unicode is discouraged.
</P>	</P>
<P>	<P>
By default, in UTF-8 mode, characters with values greater than 128 never match	By default, in a UTF mode, characters with values greater than 128 never match
\d, \s, or \w, and always match \D, \S, and \W. These sequences retain	\d, \s, or \w, and always match \D, \S, and \W. These sequences retain
their original meanings from before UTF-8 support was available, mainly for	their original meanings from before UTF support was available, mainly for
efficiency reasons. However, if PCRE is compiled with Unicode property support,	efficiency reasons. However, if PCRE is compiled with Unicode property support,
and the PCRE_UCP option is set, the behaviour is changed so that Unicode	and the PCRE_UCP option is set, the behaviour is changed so that Unicode
properties are used to determine character types, as follows:	properties are used to determine character types, as follows:
Line 463 is noticeably slower when PCRE_UCP is set.	Line 470 is noticeably slower when PCRE_UCP is set.
<P>	<P>
The sequences \h, \H, \v, and \V are features that were added to Perl at	The sequences \h, \H, \v, and \V are features that were added to Perl at
release 5.10. In contrast to the other sequences, which match only ASCII	release 5.10. In contrast to the other sequences, which match only ASCII
characters by default, these always match certain high-valued codepoints in	characters by default, these always match certain high-valued codepoints,
UTF-8 mode, whether or not PCRE_UCP is set. The horizontal space characters	whether or not PCRE_UCP is set. The horizontal space characters are:
are:
<pre>	<pre>
U+0009 Horizontal tab	U+0009 Horizontal tab
U+0020 Space	U+0020 Space
Line 496 The vertical space characters are:	Line 502 The vertical space characters are:
U+0085 Next line	U+0085 Next line
U+2028 Line separator	U+2028 Line separator
U+2029 Paragraph separator	U+2029 Paragraph separator
<a name="newlineseq"></a></PRE>	</pre>
</P>	In 8-bit, non-UTF-8 mode, only the characters with codepoints less than 256 are
	relevant.
	<a name="newlineseq"></a></P>
<br><b>	<br><b>
Newline sequences	Newline sequences
</b><br>	</b><br>
<P>	<P>
Outside a character class, by default, the escape sequence \R matches any	Outside a character class, by default, the escape sequence \R matches any
Unicode newline sequence. In non-UTF-8 mode \R is equivalent to the following:	Unicode newline sequence. In 8-bit non-UTF-8 mode \R is equivalent to the
	following:
<pre>	<pre>
(?>\r\n\|\n\|\x0b\|\f\|\r\|\x85)	(?>\r\n\|\n\|\x0b\|\f\|\r\|\x85)
</pre>	</pre>
Line 516 line, U+0085). The two-character sequence is treated a	Line 525 line, U+0085). The two-character sequence is treated a
cannot be split.	cannot be split.
</P>	</P>
<P>	<P>
In UTF-8 mode, two additional characters whose codepoints are greater than 255	In other modes, two additional characters whose codepoints are greater than 255
are added: LS (line separator, U+2028) and PS (paragraph separator, U+2029).	are added: LS (line separator, U+2028) and PS (paragraph separator, U+2029).
Unicode character property support is not needed for these characters to be	Unicode character property support is not needed for these characters to be
recognized.	recognized.
Line 533 one of the following sequences:	Line 542 one of the following sequences:
(*BSR_ANYCRLF) CR, LF, or CRLF only	(*BSR_ANYCRLF) CR, LF, or CRLF only
(*BSR_UNICODE) any Unicode newline sequence	(*BSR_UNICODE) any Unicode newline sequence
</pre>	</pre>
These override the default and the options given to <b>pcre_compile()</b> or	These override the default and the options given to the compiling function, but
<b>pcre_compile2()</b>, but they can be overridden by options given to	they can themselves be overridden by options given to a matching function. Note
<b>pcre_exec()</b> or <b>pcre_dfa_exec()</b>. Note that these special settings,	that these special settings, which are not Perl-compatible, are recognized only
which are not Perl-compatible, are recognized only at the very start of a	at the very start of a pattern, and that they must be in upper case. If more
pattern, and that they must be in upper case. If more than one of them is	than one of them is present, the last one is used. They can be combined with a
present, the last one is used. They can be combined with a change of newline	change of newline convention; for example, a pattern can start with:
convention; for example, a pattern can start with:
<pre>	<pre>
(ANY)(BSR_ANYCRLF)	(ANY)(BSR_ANYCRLF)
</pre>	</pre>
They can also be combined with the (UTF8) or (UCP) special sequences. Inside	They can also be combined with the (UTF8), (UTF16), or (*UCP) special
a character class, \R is treated as an unrecognized escape sequence, and so	sequences. Inside a character class, \R is treated as an unrecognized escape
matches the letter "R" by default, but causes an error if PCRE_EXTRA is set.	sequence, and so matches the letter "R" by default, but causes an error if
	PCRE_EXTRA is set.
<a name="uniextseq"></a></P>	<a name="uniextseq"></a></P>
<br><b>	<br><b>
Unicode character properties	Unicode character properties
Line 553 Unicode character properties	Line 562 Unicode character properties
<P>	<P>
When PCRE is built with Unicode character property support, three additional	When PCRE is built with Unicode character property support, three additional
escape sequences that match characters with specific properties are available.	escape sequences that match characters with specific properties are available.
When not in UTF-8 mode, these sequences are of course limited to testing	When in 8-bit non-UTF-8 mode, these sequences are of course limited to testing
characters whose codepoints are less than 256, but they do work in this mode.	characters whose codepoints are less than 256, but they do work in this mode.
The extra escape sequences are:	The extra escape sequences are:
<pre>	<pre>
Line 742 a modifier or "other".	Line 751 a modifier or "other".
</P>	</P>
<P>	<P>
The Cs (Surrogate) property applies only to characters in the range U+D800 to	The Cs (Surrogate) property applies only to characters in the range U+D800 to
U+DFFF. Such characters are not valid in UTF-8 strings (see RFC 3629) and so	U+DFFF. Such characters are not valid in Unicode strings and so
cannot be tested by PCRE, unless UTF-8 validity checking has been turned off	cannot be tested by PCRE, unless UTF validity checking has been turned off
(see the discussion of PCRE_NO_UTF8_CHECK in the	(see the discussion of PCRE_NO_UTF8_CHECK and PCRE_NO_UTF16_CHECK in the
<a href="pcreapi.html"><b>pcreapi</b></a>	<a href="pcreapi.html"><b>pcreapi</b></a>
page). Perl does not support the Cs property.	page). Perl does not support the Cs property.
</P>	</P>
Line 774 atomic group	Line 783 atomic group
<a href="#atomicgroup">(see below).</a>	<a href="#atomicgroup">(see below).</a>
Characters with the "mark" property are typically accents that affect the	Characters with the "mark" property are typically accents that affect the
preceding character. None of them have codepoints less than 256, so in	preceding character. None of them have codepoints less than 256, so in
non-UTF-8 mode \X matches any one character.	8-bit non-UTF-8 mode \X matches any one character.
</P>	</P>
<P>	<P>
Note that recent versions of Perl have changed \X to match what Unicode calls	Note that recent versions of Perl have changed \X to match what Unicode calls
Line 785 Matching characters by Unicode property is not fast, b	Line 794 Matching characters by Unicode property is not fast, b
a structure that contains data for over fifteen thousand characters. That is	a structure that contains data for over fifteen thousand characters. That is
why the traditional escape sequences such as \d and \w do not use Unicode	why the traditional escape sequences such as \d and \w do not use Unicode
properties in PCRE by default, though you can make them do so by setting the	properties in PCRE by default, though you can make them do so by setting the
PCRE_UCP option for <b>pcre_compile()</b> or by starting the pattern with	PCRE_UCP option or by starting the pattern with (*UCP).
(*UCP).
<a name="extraprops"></a></P>	<a name="extraprops"></a></P>
<br><b>	<br><b>
PCRE's additional properties	PCRE's additional properties
Line 865 escape sequence" error is generated instead.	Line 873 escape sequence" error is generated instead.
A word boundary is a position in the subject string where the current character	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	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	\w and the other matches \W), or the start or end of the string if the
first or last character matches \w, respectively. In UTF-8 mode, the meanings	first or last character matches \w, respectively. In a UTF mode, the meanings
of \w and \W can be changed by setting the PCRE_UCP option. When this is	of \w and \W can be changed by setting the PCRE_UCP option. When this is
done, it also affects \b and \B. Neither PCRE nor Perl has a separate "start	done, it also affects \b and \B. Neither PCRE nor Perl has a separate "start
of word" or "end of word" metasequence. However, whatever follows \b normally	of word" or "end of word" metasequence. However, whatever follows \b normally
Line 962 end of the subject in both modes, and if all branches	Line 970 end of the subject in both modes, and if all branches
<P>	<P>
Outside a character class, a dot in the pattern matches any one character in	Outside a character class, a dot in the pattern matches any one character in
the subject string except (by default) a character that signifies the end of a	the subject string except (by default) a character that signifies the end of a
line. In UTF-8 mode, the matched character may be more than one byte long.	line.
</P>	</P>
<P>	<P>
When a line ending is defined as a single character, dot never matches that	When a line ending is defined as a single character, dot never matches that
Line 989 the PCRE_DOTALL option. In other words, it matches any	Line 997 the PCRE_DOTALL option. In other words, it matches any
that signifies the end of a line. Perl also uses \N to match characters by	that signifies the end of a line. Perl also uses \N to match characters by
name; PCRE does not support this.	name; PCRE does not support this.
</P>	</P>
<br><a name="SEC7" href="#TOC1">MATCHING A SINGLE BYTE</a><br>	<br><a name="SEC7" href="#TOC1">MATCHING A SINGLE DATA UNIT</a><br>
<P>	<P>
Outside a character class, the escape sequence \C matches any one byte, both	Outside a character class, the escape sequence \C matches any one data unit,
in and out of UTF-8 mode. Unlike a dot, it always matches line-ending	whether or not a UTF mode is set. In the 8-bit library, one data unit is one
characters. The feature is provided in Perl in order to match individual bytes	byte; in the 16-bit library it is a 16-bit unit. Unlike a dot, \C always
in UTF-8 mode, but it is unclear how it can usefully be used. Because \C	matches line-ending characters. The feature is provided in Perl in order to
breaks up characters into individual bytes, matching one byte with \C in UTF-8	match individual bytes in UTF-8 mode, but it is unclear how it can usefully be
mode means that the rest of the string may start with a malformed UTF-8	used. Because \C breaks up characters into individual data units, matching one
character. This has undefined results, because PCRE assumes that it is dealing	unit with \C in a UTF mode means that the rest of the string may start with a
with valid UTF-8 strings (and by default it checks this at the start of	malformed UTF character. This has undefined results, because PCRE assumes that
processing unless the PCRE_NO_UTF8_CHECK option is used).	it is dealing with valid UTF strings (and by default it checks this at the
	start of processing unless the PCRE_NO_UTF8_CHECK option is used).
</P>	</P>
<P>	<P>
PCRE does not allow \C to appear in lookbehind assertions	PCRE does not allow \C to appear in lookbehind assertions
<a href="#lookbehind">(described below)</a>	<a href="#lookbehind">(described below)</a>
in UTF-8 mode, because this would make it impossible to calculate the length of	in a UTF mode, because this would make it impossible to calculate the length of
the lookbehind.	the lookbehind.
</P>	</P>
<P>	<P>
In general, the \C escape sequence is best avoided in UTF-8 mode. However, one	In general, the \C escape sequence is best avoided. However, one
way of using it that avoids the problem of malformed UTF-8 characters is to	way of using it that avoids the problem of malformed UTF characters is to use a
use a lookahead to check the length of the next character, as in this pattern	lookahead to check the length of the next character, as in this pattern, which
(ignore white space and line breaks):	could be used with a UTF-8 string (ignore white space and line breaks):
<pre>	<pre>
(?\| (?=[\x00-\x7f])(\C) \|	(?\| (?=[\x00-\x7f])(\C) \|
(?=[\x80-\x{7ff}])(\C)(\C) \|	(?=[\x80-\x{7ff}])(\C)(\C) \|
Line 1036 a member of the class, it should be the first data cha	Line 1045 a member of the class, it should be the first data cha
(after an initial circumflex, if present) or escaped with a backslash.	(after an initial circumflex, if present) or escaped with a backslash.
</P>	</P>
<P>	<P>
A character class matches a single character in the subject. In UTF-8 mode, the	A character class matches a single character in the subject. In a UTF mode, the
character may be more than one byte long. A matched character must be in the	character may be more than one data unit long. A matched character must be in
set of characters defined by the class, unless the first character in the class	the set of characters defined by the class, unless the first character in the
definition is a circumflex, in which case the subject character must not be in	class definition is a circumflex, in which case the subject character must not
the set defined by the class. If a circumflex is actually required as a member	be in the set defined by the class. If a circumflex is actually required as a
of the class, ensure it is not the first character, or escape it with a	member of the class, ensure it is not the first character, or escape it with a
backslash.	backslash.
</P>	</P>
<P>	<P>
Line 1054 string, and therefore it fails if the current pointer	Line 1063 string, and therefore it fails if the current pointer
string.	string.
</P>	</P>
<P>	<P>
In UTF-8 mode, characters with values greater than 255 can be included in a	In UTF-8 (UTF-16) mode, characters with values greater than 255 (0xffff) can be
class as a literal string of bytes, or by using the \x{ escaping mechanism.	included in a class as a literal string of data units, or by using the \x{
	escaping mechanism.
</P>	</P>
<P>	<P>
When caseless matching is set, any letters in a class represent both their	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	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	"A" as well as "a", and a caseless [^aeiou] does not match "A", whereas a
caseful version would. In UTF-8 mode, PCRE always understands the concept of	caseful version would. In a UTF mode, PCRE always understands the concept of
case for characters whose values are less than 128, so caseless matching is	case for characters whose values are less than 128, so caseless matching is
always possible. For characters with higher values, the concept of case is	always possible. For characters with higher values, the concept of case is
supported if PCRE is compiled with Unicode property support, but not otherwise.	supported if PCRE is compiled with Unicode property support, but not otherwise.
If you want to use caseless matching in UTF8-mode for characters 128 and above,	If you want to use caseless matching in a UTF mode for characters 128 and
you must ensure that PCRE is compiled with Unicode property support as well as	above, you must ensure that PCRE is compiled with Unicode property support as
with UTF-8 support.	well as with UTF support.
</P>	</P>
<P>	<P>
Characters that might indicate line breaks are never treated in any special way	Characters that might indicate line breaks are never treated in any special way
Line 1093 followed by two other characters. The octal or hexadec	Line 1103 followed by two other characters. The octal or hexadec
</P>	</P>
<P>	<P>
Ranges operate in the collating sequence of character values. They can also be	Ranges operate in the collating sequence of character values. They can also be
used for characters specified numerically, for example [\000-\037]. In UTF-8	used for characters specified numerically, for example [\000-\037]. Ranges
mode, ranges can include characters whose values are greater than 255, for	can include any characters that are valid for the current mode.
example [\x{100}-\x{2ff}].
</P>	</P>
<P>	<P>
If a range that includes letters is used when caseless matching is set, it	If a range that includes letters is used when caseless matching is set, it
matches the letters in either case. For example, [W-c] is equivalent to	matches the letters in either case. For example, [W-c] is equivalent to
[][\\^_`wxyzabc], matched caselessly, and in non-UTF-8 mode, if character	[][\\^_`wxyzabc], matched caselessly, and in a non-UTF mode, if character
tables for a French locale are in use, [\xc8-\xcb] matches accented E	tables for a French locale are in use, [\xc8-\xcb] matches accented E
characters in both cases. In UTF-8 mode, PCRE supports the concept of case for	characters in both cases. In UTF modes, PCRE supports the concept of case for
characters with values greater than 128 only when it is compiled with Unicode	characters with values greater than 128 only when it is compiled with Unicode
property support.	property support.
</P>	</P>
Line 1110 property support.	Line 1119 property support.
The character escape sequences \d, \D, \h, \H, \p, \P, \s, \S, \v,	The character escape sequences \d, \D, \h, \H, \p, \P, \s, \S, \v,
\V, \w, and \W may appear in a character class, and add the characters that	\V, \w, and \W may appear in a character class, and add the characters that
they match to the class. For example, [\dABCDEF] matches any hexadecimal	they match to the class. For example, [\dABCDEF] matches any hexadecimal
digit. In UTF-8 mode, the PCRE_UCP option affects the meanings of \d, \s, \w	digit. In UTF modes, the PCRE_UCP option affects the meanings of \d, \s, \w
and their upper case partners, just as it does when they appear outside a	and their upper case partners, just as it does when they appear outside a
character class, as described in the section entitled	character class, as described in the section entitled
<a href="#genericchartypes">"Generic character types"</a>	<a href="#genericchartypes">"Generic character types"</a>
Line 1179 syntax [.ch.] and [=ch=] where "ch" is a "collating el	Line 1188 syntax [.ch.] and [=ch=] where "ch" is a "collating el
supported, and an error is given if they are encountered.	supported, and an error is given if they are encountered.
</P>	</P>
<P>	<P>
By default, in UTF-8 mode, characters with values greater than 128 do not match	By default, in UTF modes, characters with values greater than 128 do not match
any of the POSIX character classes. However, if the PCRE_UCP option is passed	any of the POSIX character classes. However, if the PCRE_UCP option is passed
to <b>pcre_compile()</b>, some of the classes are changed so that Unicode	to <b>pcre_compile()</b>, some of the classes are changed so that Unicode
character properties are used. This is achieved by replacing the POSIX classes	character properties are used. This is achieved by replacing the POSIX classes
Line 1264 behaviour otherwise.	Line 1273 behaviour otherwise.
</P>	</P>
<P>	<P>
<b>Note:</b> There are other PCRE-specific options that can be set by the	<b>Note:</b> There are other PCRE-specific options that can be set by the
application when the compile or match functions are called. In some cases the	application when the compiling or matching functions are called. In some cases
pattern can contain special leading sequences such as (*CRLF) to override what	the pattern can contain special leading sequences such as (*CRLF) to override
the application has set or what has been defaulted. Details are given in the	what the application has set or what has been defaulted. Details are given in
section entitled	the section entitled
<a href="#newlineseq">"Newline sequences"</a>	<a href="#newlineseq">"Newline sequences"</a>
above. There are also the (UTF8) and (UCP) leading sequences that can be used	above. There are also the (UTF8), (UTF16), and (*UCP) leading sequences that
to set UTF-8 and Unicode property modes; they are equivalent to setting the	can be used to set UTF and Unicode property modes; they are equivalent to
PCRE_UTF8 and the PCRE_UCP options, respectively.	setting the PCRE_UTF8, PCRE_UTF16, and the PCRE_UCP options, respectively.
<a name="subpattern"></a></P>	<a name="subpattern"></a></P>
<br><a name="SEC12" href="#TOC1">SUBPATTERNS</a><br>	<br><a name="SEC12" href="#TOC1">SUBPATTERNS</a><br>
<P>	<P>
Line 1289 match "cataract", "erpillar" or an empty string.	Line 1298 match "cataract", "erpillar" or an empty string.
<br>	<br>
2. It sets up the subpattern as a capturing subpattern. This means that, when	2. It sets up the subpattern as a capturing subpattern. This means that, when
the whole pattern matches, that portion of the subject string that matched the	the whole pattern matches, that portion of the subject string that matched the
subpattern is passed back to the caller via the <i>ovector</i> argument of	subpattern is passed back to the caller via the <i>ovector</i> argument of the
<b>pcre_exec()</b>. Opening parentheses are counted from left to right (starting	matching function. (This applies only to the traditional matching functions;
from 1) to obtain numbers for the capturing subpatterns. For example, if the	the DFA matching functions do not support capturing.)
string "the red king" is matched against the pattern	</P>
	<P>
	Opening parentheses are counted from left to right (starting from 1) to obtain
	numbers for the capturing subpatterns. For example, if the string "the red
	king" is matched against the pattern
<pre>	<pre>
the ((red\|white) (king\|queen))	the ((red\|white) (king\|queen))
</pre>	</pre>
Line 1452 items:	Line 1465 items:
a literal data character	a literal data character
the dot metacharacter	the dot metacharacter
the \C escape sequence	the \C escape sequence
the \X escape sequence (in UTF-8 mode with Unicode properties)	the \X escape sequence
the \R escape sequence	the \R escape sequence
an escape such as \d or \pL that matches a single character	an escape such as \d or \pL that matches a single character
a character class	a character class
Line 1484 quantifier, is taken as a literal character. For examp	Line 1497 quantifier, is taken as a literal character. For examp
quantifier, but a literal string of four characters.	quantifier, but a literal string of four characters.
</P>	</P>
<P>	<P>
In UTF-8 mode, quantifiers apply to UTF-8 characters rather than to individual	In UTF modes, quantifiers apply to characters rather than to individual data
bytes. Thus, for example, \x{100}{2} matches two UTF-8 characters, each of	units. Thus, for example, \x{100}{2} matches two characters, each of
which is represented by a two-byte sequence. Similarly, when Unicode property	which is represented by a two-byte sequence in a UTF-8 string. Similarly,
support is available, \X{3} matches three Unicode extended sequences, each of	\X{3} matches three Unicode extended sequences, each of which may be several
which may be several bytes long (and they may be of different lengths).	data units long (and they may be of different lengths).
</P>	</P>
<P>	<P>
The quantifier {0} is permitted, causing the expression to behave as if the	The quantifier {0} is permitted, causing the expression to behave as if the
Line 1950 match. If there are insufficient characters before the	Line 1963 match. If there are insufficient characters before the
assertion fails.	assertion fails.
</P>	</P>
<P>	<P>
In UTF-8 mode, PCRE does not allow the \C escape (which matches a single byte,	In a UTF mode, PCRE does not allow the \C escape (which matches a single data
even in UTF-8 mode) to appear in lookbehind assertions, because it makes it	unit even in a UTF mode) to appear in lookbehind assertions, because it makes
impossible to calculate the length of the lookbehind. The \X and \R escapes,	it impossible to calculate the length of the lookbehind. The \X and \R
which can match different numbers of bytes, are also not permitted.	escapes, which can match different numbers of data units, are also not
	permitted.
</P>	</P>
<P>	<P>
<a href="#subpatternsassubroutines">"Subroutine"</a>	<a href="#subpatternsassubroutines">"Subroutine"</a>
Line 2192 closing parenthesis. Nested parentheses are not permit	Line 2206 closing parenthesis. Nested parentheses are not permit
option is set, an unescaped # character also introduces a comment, which in	option is set, an unescaped # character also introduces a comment, which in
this case continues to immediately after the next newline character or	this case continues to immediately after the next newline character or
character sequence in the pattern. Which characters are interpreted as newlines	character sequence in the pattern. Which characters are interpreted as newlines
is controlled by the options passed to <b>pcre_compile()</b> or by a special	is controlled by the options passed to a compiling function or by a special
sequence at the start of the pattern, as described in the section entitled	sequence at the start of the pattern, as described in the section entitled
<a href="#newlines">"Newline conventions"</a>	<a href="#newlines">"Newline conventions"</a>
above. Note that the end of this type of comment is a literal newline sequence	above. Note that the end of this type of comment is a literal newline sequence
Line 2491 same pair of parentheses when there is a repetition.	Line 2505 same pair of parentheses when there is a repetition.
<P>	<P>
PCRE provides a similar feature, but of course it cannot obey arbitrary Perl	PCRE provides a similar feature, but of course it cannot obey arbitrary Perl
code. The feature is called "callout". The caller of PCRE provides an external	code. The feature is called "callout". The caller of PCRE provides an external
function by putting its entry point in the global variable <i>pcre_callout</i>.	function by putting its entry point in the global variable <i>pcre_callout</i>
By default, this variable contains NULL, which disables all calling out.	(8-bit library) or <i>pcre16_callout</i> (16-bit library). By default, this
	variable contains NULL, which disables all calling out.
</P>	</P>
<P>	<P>
Within a regular expression, (?C) indicates the points at which the external	Within a regular expression, (?C) indicates the points at which the external
Line 2502 For example, this pattern has two callout points:	Line 2517 For example, this pattern has two callout points:
<pre>	<pre>
(?C1)abc(?C2)def	(?C1)abc(?C2)def
</pre>	</pre>
If the PCRE_AUTO_CALLOUT flag is passed to <b>pcre_compile()</b>, callouts are	If the PCRE_AUTO_CALLOUT flag is passed to a compiling function, callouts are
automatically installed before each item in the pattern. They are all numbered	automatically installed before each item in the pattern. They are all numbered
255.	255.
</P>	</P>
<P>	<P>
During matching, when PCRE reaches a callout point (and <i>pcre_callout</i> is	During matching, when PCRE reaches a callout point, the external function is
set), the external function is called. It is provided with the number of the	called. It is provided with the number of the callout, the position in the
callout, the position in the pattern, and, optionally, one item of data	pattern, and, optionally, one item of data originally supplied by the caller of
originally supplied by the caller of <b>pcre_exec()</b>. The callout function	the matching function. The callout function may cause matching to proceed, to
may cause matching to proceed, to backtrack, or to fail altogether. A complete	backtrack, or to fail altogether. A complete description of the interface to
description of the interface to the callout function is given in the	the callout function is given in the
<a href="pcrecallout.html"><b>pcrecallout</b></a>	<a href="pcrecallout.html"><b>pcrecallout</b></a>
documentation.	documentation.
<a name="backtrackcontrol"></a></P>	<a name="backtrackcontrol"></a></P>
Line 2526 remarks apply to the PCRE features described in this s	Line 2541 remarks apply to the PCRE features described in this s
</P>	</P>
<P>	<P>
Since these verbs are specifically related to backtracking, most of them can be	Since these verbs are specifically related to backtracking, most of them can be
used only when the pattern is to be matched using <b>pcre_exec()</b>, which uses	used only when the pattern is to be matched using one of the traditional
a backtracking algorithm. With the exception of (*FAIL), which behaves like a	matching functions, which use a backtracking algorithm. With the exception of
failing negative assertion, they cause an error if encountered by	(*FAIL), which behaves like a failing negative assertion, they cause an error
<b>pcre_dfa_exec()</b>.	if encountered by a DFA matching function.
</P>	</P>
<P>	<P>
If any of these verbs are used in an assertion or in a subpattern that is	If any of these verbs are used in an assertion or in a subpattern that is
Line 2613 A name is always required with this verb. There may be	Line 2628 A name is always required with this verb. There may be
</P>	</P>
<P>	<P>
When a match succeeds, the name of the last-encountered (*MARK) on the matching	When a match succeeds, the name of the last-encountered (*MARK) on the matching
path is passed back to the caller via the <i>pcre_extra</i> data structure, as	path is passed back to the caller as described in the section entitled
described in the	<a href="pcreapi.html#extradata">"Extra data for <b>pcre_exec()</b>"</a>
<a href="pcreapi.html#extradata">section on <i>pcre_extra</i></a>
in the	in the
<a href="pcreapi.html"><b>pcreapi</b></a>	<a href="pcreapi.html"><b>pcreapi</b></a>
documentation. Here is an example of <b>pcretest</b> output, where the /K	documentation. Here is an example of <b>pcretest</b> output, where the /K
Line 2816 overrides.	Line 2830 overrides.
<br><a name="SEC26" href="#TOC1">SEE ALSO</a><br>	<br><a name="SEC26" href="#TOC1">SEE ALSO</a><br>
<P>	<P>
<b>pcreapi</b>(3), <b>pcrecallout</b>(3), <b>pcrematching</b>(3),	<b>pcreapi</b>(3), <b>pcrecallout</b>(3), <b>pcrematching</b>(3),
<b>pcresyntax</b>(3), <b>pcre</b>(3).	<b>pcresyntax</b>(3), <b>pcre</b>(3), <b>pcre16(3)</b>.
</P>	</P>
<br><a name="SEC27" href="#TOC1">AUTHOR</a><br>	<br><a name="SEC27" href="#TOC1">AUTHOR</a><br>
<P>	<P>
Line 2829 Cambridge CB2 3QH, England.	Line 2843 Cambridge CB2 3QH, England.
</P>	</P>
<br><a name="SEC28" href="#TOC1">REVISION</a><br>	<br><a name="SEC28" href="#TOC1">REVISION</a><br>
<P>	<P>
Last updated: 29 November 2011	Last updated: 09 January 2012
<br>	<br>
Copyright © 1997-2011 University of Cambridge.	Copyright © 1997-2012 University of Cambridge.
<br>	<br>
<p>	<p>
Return to the <a href="index.html">PCRE index page</a>.	Return to the <a href="index.html">PCRE index page</a>.

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