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version 1.1.1.4, 2013/07/22 08:25:57	version 1.1.1.5, 2014/06/15 19:46:05
Line 1	Line 1
.TH PCREPATTERN 3 "26 April 2013" "PCRE 8.33"	.TH PCREPATTERN 3 "03 December 2013" "PCRE 8.34"
.SH NAME	.SH NAME
PCRE - Perl-compatible regular expressions	PCRE - Perl-compatible regular expressions
.SH "PCRE REGULAR EXPRESSION DETAILS"	.SH "PCRE REGULAR EXPRESSION DETAILS"
Line 80 appearance causes an error.	Line 80 appearance causes an error.
.SS "Unicode property support"	.SS "Unicode property support"
.rs	.rs
.sp	.sp
Another special sequence that may appear at the start of a pattern is	Another special sequence that may appear at the start of a pattern is (*UCP).
.sp
(*UCP)
.sp
This has the same effect as setting the PCRE_UCP option: it causes sequences	This has the same effect as setting the PCRE_UCP option: it causes sequences
such as \ed and \ew to use Unicode properties to determine character types,	such as \ed and \ew to use Unicode properties to determine character types,
instead of recognizing only characters with codes less than 128 via a lookup	instead of recognizing only characters with codes less than 128 via a lookup
table.	table.
.	.
.	.
	.SS "Disabling auto-possessification"
	.rs
	.sp
	If a pattern starts with (*NO_AUTO_POSSESS), it has the same effect as setting
	the PCRE_NO_AUTO_POSSESS option at compile time. This stops PCRE from making
	quantifiers possessive when what follows cannot match the repeated item. For
	example, by default a+b is treated as a++b. For more details, see the
	.\" HREF
	\fBpcreapi\fP
	.\"
	documentation.
	.
	.
.SS "Disabling start-up optimizations"	.SS "Disabling start-up optimizations"
.rs	.rs
.sp	.sp
If a pattern starts with (*NO_START_OPT), it has the same effect as setting the	If a pattern starts with (*NO_START_OPT), it has the same effect as setting the
PCRE_NO_START_OPTIMIZE option either at compile or matching time.	PCRE_NO_START_OPTIMIZE option either at compile or matching time. This disables
	several optimizations for quickly reaching "no match" results. For more
	details, see the
	.\" HREF
	\fBpcreapi\fP
	.\"
	documentation.
.	.
.	.
.\" HTML <a name="newlines"></a>	.\" HTML <a name="newlines"></a>
Line 164 pattern of the form	Line 180 pattern of the form
(*LIMIT_RECURSION=d)	(*LIMIT_RECURSION=d)
.sp	.sp
where d is any number of decimal digits. However, the value of the setting must	where d is any number of decimal digits. However, the value of the setting must
be less than the value set by the caller of \fBpcre_exec()\fP for it to have	be less than the value set (or defaulted) by the caller of \fBpcre_exec()\fP
any effect. In other words, the pattern writer can lower the limit set by the	for it to have any effect. In other words, the pattern writer can lower the
programmer, but not raise it. If there is more than one setting of one of these	limits set by the programmer, but not raise them. If there is more than one
limits, the lower value is used.	setting of one of these limits, the lower value is used.
.	.
.	.
.SH "EBCDIC CHARACTER CODES"	.SH "EBCDIC CHARACTER CODES"
Line 257 In a UTF mode, only ASCII numbers and letters have any	Line 273 In a UTF mode, only ASCII numbers and letters have any
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
If a pattern is compiled with the PCRE_EXTENDED option, white space in the	If a pattern is compiled with the PCRE_EXTENDED option, most white space in the
pattern (other than in a character class) and characters between a # outside	pattern (other than in a character class), and characters between a # outside a
a character class and the next newline are ignored. An escaping backslash can	character class and the next newline, inclusive, are ignored. An escaping
be used to include a white space or # character as part of the pattern.	backslash can be used to include a white space or # character as part of the
	pattern.
.P	.P
If you want to remove the special meaning from a sequence of characters, you	If you want to remove the special meaning from a sequence of characters, you
can do so by putting them between \eQ and \eE. This is different from Perl in	can do so by putting them between \eQ and \eE. This is different from Perl in
Line 300 one of the following escape sequences than the binary	Line 317 one of the following escape sequences than the binary
\en linefeed (hex 0A)	\en linefeed (hex 0A)
\er carriage return (hex 0D)	\er carriage return (hex 0D)
\et tab (hex 09)	\et tab (hex 09)
	\e0dd character with octal code 0dd
\eddd character with octal code ddd, or back reference	\eddd character with octal code ddd, or back reference
	\eo{ddd..} character with octal code ddd..
\exhh character with hex code hh	\exhh character with hex code hh
\ex{hhh..} character with hex code hhh.. (non-JavaScript mode)	\ex{hhh..} character with hex code hhh.. (non-JavaScript mode)
\euhhhh character with hex code hhhh (JavaScript mode only)	\euhhhh character with hex code hhhh (JavaScript mode only)
Line 321 byte are inverted. Thus \ecA becomes hex 01, as in ASC	Line 340 byte are inverted. Thus \ecA becomes hex 01, as in ASC
the EBCDIC letters are disjoint, \ecZ becomes hex 29 (Z is E9), and other	the EBCDIC letters are disjoint, \ecZ becomes hex 29 (Z is E9), and other
characters also generate different values.	characters also generate different values.
.P	.P
By default, after \ex, from zero to two hexadecimal digits are read (letters
can be in upper or lower case). Any number of hexadecimal digits may appear
between \ex{ and }, but the character code is constrained as follows:
.sp
8-bit non-UTF mode less than 0x100
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
32-bit non-UTF mode less than 0x80000000
32-bit UTF-32 mode less than 0x10ffff and a valid codepoint
.sp
Invalid Unicode codepoints are the range 0xd800 to 0xdfff (the so-called
"surrogate" codepoints), and 0xffef.
.P
If characters other than hexadecimal digits appear between \ex{ and }, or if
there is no terminating }, this form of escape is not recognized. Instead, the
initial \ex will be interpreted as a basic hexadecimal escape, with no
following digits, giving a character whose value is zero.
.P
If the PCRE_JAVASCRIPT_COMPAT option is set, the interpretation of \ex is
as just described only when it is followed by two hexadecimal digits.
Otherwise, it matches a literal "x" character. In JavaScript mode, support for
code points greater than 256 is provided by \eu, which must be followed by
four hexadecimal digits; otherwise it matches a literal "u" character.
Character codes specified by \eu in JavaScript mode are constrained in the same
was as those specified by \ex in non-JavaScript mode.
.P
Characters whose value is less than 256 can be defined by either of the two
syntaxes for \ex (or by \eu in JavaScript mode). There is no difference in the
way they are handled. For example, \exdc is exactly the same as \ex{dc} (or
\eu00dc in JavaScript mode).
.P
After \e0 up to two further octal digits are read. If there are fewer than two	After \e0 up to two further octal digits are read. If there are fewer than two
digits, just those that are present are used. Thus the sequence \e0\ex\e07	digits, just those that are present are used. Thus the sequence \e0\ex\e07
specifies two binary zeros followed by a BEL character (code value 7). Make	specifies two binary zeros followed by a BEL character (code value 7). Make
sure you supply two digits after the initial zero if the pattern character that	sure you supply two digits after the initial zero if the pattern character that
follows is itself an octal digit.	follows is itself an octal digit.
.P	.P
The handling of a backslash followed by a digit other than 0 is complicated.	The escape \eo must be followed by a sequence of octal digits, enclosed in
Outside a character class, PCRE reads it and any following digits as a decimal	braces. An error occurs if this is not the case. This escape is a recent
number. If the number is less than 10, or if there have been at least that many	addition to Perl; it provides way of specifying character code points as octal
	numbers greater than 0777, and it also allows octal numbers and back references
	to be unambiguously specified.
	.P
	For greater clarity and unambiguity, it is best to avoid following \e by a
	digit greater than zero. Instead, use \eo{} or \ex{} to specify character
	numbers, and \eg{} to specify back references. The following paragraphs
	describe the old, ambiguous syntax.
	.P
	The handling of a backslash followed by a digit other than 0 is complicated,
	and Perl has changed in recent releases, causing PCRE also to change. Outside a
	character class, PCRE reads the digit and any following digits as a decimal
	number. If the number is less than 8, or if there have been at least that many
previous capturing left parentheses in the expression, the entire sequence is	previous capturing left parentheses in the expression, the entire sequence is
taken as a \fIback reference\fP. A description of how this works is given	taken as a \fIback reference\fP. A description of how this works is given
.\" HTML <a href="#backreferences">	.\" HTML <a href="#backreferences">
Line 374 following the discussion of	Line 373 following the discussion of
parenthesized subpatterns.	parenthesized subpatterns.
.\"	.\"
.P	.P
Inside a character class, or if the decimal number is greater than 9 and there	Inside a character class, or if the decimal number following \e is greater than
have not been that many capturing subpatterns, PCRE re-reads up to three octal	7 and there have not been that many capturing subpatterns, PCRE handles \e8 and
digits following the backslash, and uses them to generate a data character. Any	\e9 as the literal characters "8" and "9", and otherwise re-reads up to three
subsequent digits stand for themselves. The value of the character is	octal digits following the backslash, using them to generate a data character.
constrained in the same way as characters specified in hexadecimal.	Any subsequent digits stand for themselves. For example:
For example:
.sp	.sp
\e040 is another way of writing an ASCII space	\e040 is another way of writing an ASCII space
.\" JOIN	.\" JOIN
Line 398 For example:	Line 396 For example:
\e377 might be a back reference, otherwise	\e377 might be a back reference, otherwise
the value 255 (decimal)	the value 255 (decimal)
.\" JOIN	.\" JOIN
\e81 is either a back reference, or a binary zero	\e81 is either a back reference, or the two
followed by the two characters "8" and "1"	characters "8" and "1"
.sp	.sp
Note that octal values of 100 or greater must not be introduced by a leading	Note that octal values of 100 or greater that are specified using this syntax
zero, because no more than three octal digits are ever read.	must not be introduced by a leading zero, because no more than three octal
	digits are ever read.
.P	.P
	By default, after \ex that is not followed by {, from zero to two hexadecimal
	digits are read (letters can be in upper or lower case). Any number of
	hexadecimal digits may appear between \ex{ and }. If a character other than
	a hexadecimal digit appears between \ex{ and }, or if there is no terminating
	}, an error occurs.
	.P
	If the PCRE_JAVASCRIPT_COMPAT option is set, the interpretation of \ex is
	as just described only when it is followed by two hexadecimal digits.
	Otherwise, it matches a literal "x" character. In JavaScript mode, support for
	code points greater than 256 is provided by \eu, which must be followed by
	four hexadecimal digits; otherwise it matches a literal "u" character.
	.P
	Characters whose value is less than 256 can be defined by either of the two
	syntaxes for \ex (or by \eu in JavaScript mode). There is no difference in the
	way they are handled. For example, \exdc is exactly the same as \ex{dc} (or
	\eu00dc in JavaScript mode).
	.
	.
	.SS "Constraints on character values"
	.rs
	.sp
	Characters that are specified using octal or hexadecimal numbers are
	limited to certain values, as follows:
	.sp
	8-bit non-UTF mode less than 0x100
	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
	32-bit non-UTF mode less than 0x100000000
	32-bit UTF-32 mode less than 0x10ffff and a valid codepoint
	.sp
	Invalid Unicode codepoints are the range 0xd800 to 0xdfff (the so-called
	"surrogate" codepoints), and 0xffef.
	.
	.
	.SS "Escape sequences in character classes"
	.rs
	.sp
All the sequences that define a single character value can be used both inside	All the sequences that define a single character value can be used both inside
and outside character classes. In addition, inside a character class, \eb is	and outside character classes. In addition, inside a character class, \eb is
interpreted as the backspace character (hex 08).	interpreted as the backspace character (hex 08).
Line 494 classes. They each match one character of the appropri	Line 531 classes. They each match one character of the appropri
matching point is at the end of the subject string, all of them fail, because	matching point is at the end of the subject string, all of them fail, because
there is no character to match.	there is no character to match.
.P	.P
For compatibility with Perl, \es does not match the VT character (code 11).	For compatibility with Perl, \es did not used to match the VT character (code
This makes it different from the the POSIX "space" class. The \es characters	11), which made it different from the the POSIX "space" class. However, Perl
are HT (9), LF (10), FF (12), CR (13), and space (32). If "use locale;" is	added VT at release 5.18, and PCRE followed suit at release 8.34. The default
included in a Perl script, \es may match the VT character. In PCRE, it never	\es characters are now HT (9), LF (10), VT (11), FF (12), CR (13), and space
does.	(32), which are defined as white space in the "C" locale. This list may vary if
	locale-specific matching is taking place. For example, in some locales the
	"non-breaking space" character (\exA0) is recognized as white space, and in
	others the VT character is not.
.P	.P
A "word" character is an underscore or any character that is a letter or digit.	A "word" character is an underscore or any character that is a letter or digit.
By default, the definition of letters and digits is controlled by PCRE's	By default, the definition of letters and digits is controlled by PCRE's
Line 513 in the	Line 553 in the
\fBpcreapi\fP	\fBpcreapi\fP
.\"	.\"
page). For example, in a French locale such as "fr_FR" in Unix-like systems,	page). For example, in a French locale such as "fr_FR" in Unix-like systems,
or "french" in Windows, some character codes greater than 128 are used for	or "french" in Windows, some character codes greater than 127 are used for
accented letters, and these are then matched by \ew. The use of locales with	accented letters, and these are then matched by \ew. The use of locales with
Unicode is discouraged.	Unicode is discouraged.
.P	.P
By default, in a UTF mode, characters with values greater than 128 never match	By default, characters whose code points are greater than 127 never match \ed,
\ed, \es, or \ew, and always match \eD, \eS, and \eW. These sequences retain	\es, or \ew, and always match \eD, \eS, and \eW, although this may vary for
their original meanings from before UTF support was available, mainly for	characters in the range 128-255 when locale-specific matching is happening.
efficiency reasons. However, if PCRE is compiled with Unicode property support,	These escape sequences retain their original meanings from before Unicode
and the PCRE_UCP option is set, the behaviour is changed so that Unicode	support was available, mainly for efficiency reasons. If PCRE is compiled with
properties are used to determine character types, as follows:	Unicode property support, and the PCRE_UCP option is set, the behaviour is
	changed so that Unicode properties are used to determine character types, as
	follows:
.sp	.sp
\ed any character that \ep{Nd} matches (decimal digit)	\ed any character that matches \ep{Nd} (decimal digit)
\es any character that \ep{Z} matches, plus HT, LF, FF, CR	\es any character that matches \ep{Z} or \eh or \ev
\ew any character that \ep{L} or \ep{N} matches, plus underscore	\ew any character that matches \ep{L} or \ep{N}, plus underscore
.sp	.sp
The upper case escapes match the inverse sets of characters. Note that \ed	The upper case escapes match the inverse sets of characters. Note that \ed
matches only decimal digits, whereas \ew matches any Unicode digit, as well as	matches only decimal digits, whereas \ew matches any Unicode digit, as well as
Line 536 is noticeably slower when PCRE_UCP is set.	Line 578 is noticeably slower when PCRE_UCP is set.
.P	.P
The sequences \eh, \eH, \ev, and \eV are features that were added to Perl at	The sequences \eh, \eH, \ev, and \eV 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,	characters by default, these always match certain high-valued code points,
whether or not PCRE_UCP is set. The horizontal space characters are:	whether or not PCRE_UCP is set. The horizontal space characters are:
.sp	.sp
U+0009 Horizontal tab (HT)	U+0009 Horizontal tab (HT)
Line 906 the "mark" property always have the "extend" grapheme	Line 948 the "mark" property always have the "extend" grapheme
.sp	.sp
As well as the standard Unicode properties described above, PCRE supports four	As well as the standard Unicode properties described above, PCRE supports four
more that make it possible to convert traditional escape sequences such as \ew	more that make it possible to convert traditional escape sequences such as \ew
and \es and POSIX character classes to use Unicode properties. PCRE uses these	and \es to use Unicode properties. PCRE uses these non-standard, non-Perl
non-standard, non-Perl properties internally when PCRE_UCP is set. However,	properties internally when PCRE_UCP is set. However, they may also be used
they may also be used explicitly. These properties are:	explicitly. These properties are:
.sp	.sp
Xan Any alphanumeric character	Xan Any alphanumeric character
Xps Any POSIX space character	Xps Any POSIX space character
Line 918 they may also be used explicitly. These properties are	Line 960 they may also be used explicitly. These properties are
Xan matches characters that have either the L (letter) or the N (number)	Xan matches characters that have either the L (letter) or the N (number)
property. Xps matches the characters tab, linefeed, vertical tab, form feed, or	property. Xps matches the characters tab, linefeed, vertical tab, form feed, or
carriage return, and any other character that has the Z (separator) property.	carriage return, and any other character that has the Z (separator) property.
Xsp is the same as Xps, except that vertical tab is excluded. Xwd matches the	Xsp is the same as Xps; it used to exclude vertical tab, for Perl
same characters as Xan, plus underscore.	compatibility, but Perl changed, and so PCRE followed at release 8.34. Xwd
	matches the same characters as Xan, plus underscore.
.P	.P
There is another non-standard property, Xuc, which matches any character that	There is another non-standard property, Xuc, which matches any character that
can be represented by a Universal Character Name in C++ and other programming	can be represented by a Universal Character Name in C++ and other programming
Line 1215 The minus (hyphen) character can be used to specify a	Line 1258 The minus (hyphen) character can be used to specify a
character class. For example, [d-m] matches any letter between d and m,	character class. For example, [d-m] matches any letter between d and m,
inclusive. If a minus character is required in a class, it must be escaped with	inclusive. If a minus character is required in a class, it must be escaped with
a backslash or appear in a position where it cannot be interpreted as	a backslash or appear in a position where it cannot be interpreted as
indicating a range, typically as the first or last character in the class.	indicating a range, typically as the first or last character in the class, or
	immediately after a range. For example, [b-d-z] matches letters in the range b
	to d, a hyphen character, or z.
.P	.P
It is not possible to have the literal character "]" as the end character of a	It is not possible to have the literal character "]" as the end character of a
range. A pattern such as [W-]46] is interpreted as a class of two characters	range. A pattern such as [W-]46] is interpreted as a class of two characters
Line 1225 the end of range, so [W-\e]46] is interpreted as a cla	Line 1270 the end of range, so [W-\e]46] is interpreted as a cla
followed by two other characters. The octal or hexadecimal representation of	followed by two other characters. The octal or hexadecimal representation of
"]" can also be used to end a range.	"]" can also be used to end a range.
.P	.P
	An error is generated if a POSIX character class (see below) or an escape
	sequence other than one that defines a single character appears at a point
	where a range ending character is expected. For example, [z-\exff] is valid,
	but [A-\ed] and [A-[:digit:]] are not.
	.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 [\e000-\e037]. Ranges	used for characters specified numerically, for example [\e000-\e037]. Ranges
can include any characters that are valid for the current mode.	can include any characters that are valid for the current mode.
Line 1263 something AND NOT ...".	Line 1313 something AND NOT ...".
The only metacharacters that are recognized in character classes are backslash,	The only metacharacters that are recognized in character classes are backslash,
hyphen (only where it can be interpreted as specifying a range), circumflex	hyphen (only where it can be interpreted as specifying a range), circumflex
(only at the start), opening square bracket (only when it can be interpreted as	(only at the start), opening square bracket (only when it can be interpreted as
introducing a POSIX class name - see the next section), and the terminating	introducing a POSIX class name, or for a special compatibility feature - see
closing square bracket. However, escaping other non-alphanumeric characters	the next two sections), and the terminating closing square bracket. However,
does no harm.	escaping other non-alphanumeric characters does no harm.
.	.
.	.
.SH "POSIX CHARACTER CLASSES"	.SH "POSIX CHARACTER CLASSES"
Line 1290 are:	Line 1340 are:
lower lower case letters	lower lower case letters
print printing characters, including space	print printing characters, including space
punct printing characters, excluding letters and digits and space	punct printing characters, excluding letters and digits and space
space white space (not quite the same as \es)	space white space (the same as \es from PCRE 8.34)
upper upper case letters	upper upper case letters
word "word" characters (same as \ew)	word "word" characters (same as \ew)
xdigit hexadecimal digits	xdigit hexadecimal digits
.sp	.sp
The "space" characters are HT (9), LF (10), VT (11), FF (12), CR (13), and	The default "space" characters are HT (9), LF (10), VT (11), FF (12), CR (13),
space (32). Notice that this list includes the VT character (code 11). This	and space (32). If locale-specific matching is taking place, the list of space
makes "space" different to \es, which does not include VT (for Perl	characters may be different; there may be fewer or more of them. "Space" used
compatibility).	to be different to \es, which did not include VT, for Perl compatibility.
	However, Perl changed at release 5.18, and PCRE followed at release 8.34.
	"Space" and \es now match the same set of characters.
.P	.P
The name "word" is a Perl extension, and "blank" is a GNU extension from Perl	The name "word" is a Perl extension, and "blank" is a GNU extension from Perl
5.8. Another Perl extension is negation, which is indicated by a ^ character	5.8. Another Perl extension is negation, which is indicated by a ^ character
Line 1310 matches "1", "2", or any non-digit. PCRE (and Perl) al	Line 1362 matches "1", "2", or any non-digit. PCRE (and Perl) al
syntax [.ch.] and [=ch=] where "ch" is a "collating element", but these are not	syntax [.ch.] and [=ch=] where "ch" is a "collating element", but these are not
supported, and an error is given if they are encountered.	supported, and an error is given if they are encountered.
.P	.P
By default, in UTF modes, characters with values greater than 128 do not match	By default, characters with values greater than 128 do not match any of the
any of the POSIX character classes. However, if the PCRE_UCP option is passed	POSIX character classes. However, if the PCRE_UCP option is passed to
to \fBpcre_compile()\fP, some of the classes are changed so that Unicode	\fBpcre_compile()\fP, some of the classes are changed so that Unicode character
character properties are used. This is achieved by replacing the POSIX classes	properties are used. This is achieved by replacing certain POSIX classes by
by other sequences, as follows:	other sequences, as follows:
.sp	.sp
[:alnum:] becomes \ep{Xan}	[:alnum:] becomes \ep{Xan}
[:alpha:] becomes \ep{L}	[:alpha:] becomes \ep{L}
Line 1325 by other sequences, as follows:	Line 1377 by other sequences, as follows:
[:upper:] becomes \ep{Lu}	[:upper:] becomes \ep{Lu}
[:word:] becomes \ep{Xwd}	[:word:] becomes \ep{Xwd}
.sp	.sp
Negated versions, such as [:^alpha:] use \eP instead of \ep. The other POSIX	Negated versions, such as [:^alpha:] use \eP instead of \ep. Three other POSIX
classes are unchanged, and match only characters with code points less than	classes are handled specially in UCP mode:
128.	.TP 10
	[:graph:]
	This matches characters that have glyphs that mark the page when printed. In
	Unicode property terms, it matches all characters with the L, M, N, P, S, or Cf
	properties, except for:
	.sp
	U+061C Arabic Letter Mark
	U+180E Mongolian Vowel Separator
	U+2066 - U+2069 Various "isolate"s
	.sp
	.TP 10
	[:print:]
	This matches the same characters as [:graph:] plus space characters that are
	not controls, that is, characters with the Zs property.
	.TP 10
	[:punct:]
	This matches all characters that have the Unicode P (punctuation) property,
	plus those characters whose code points are less than 128 that have the S
	(Symbol) property.
	.P
	The other POSIX classes are unchanged, and match only characters with code
	points less than 128.
.	.
.	.
	.SH "COMPATIBILITY FEATURE FOR WORD BOUNDARIES"
	.rs
	.sp
	In the POSIX.2 compliant library that was included in 4.4BSD Unix, the ugly
	syntax [[:<:]] and [[:>:]] is used for matching "start of word" and "end of
	word". PCRE treats these items as follows:
	.sp
	[[:<:]] is converted to \eb(?=\ew)
	[[:>:]] is converted to \eb(?<=\ew)
	.sp
	Only these exact character sequences are recognized. A sequence such as
	[a[:<:]b] provokes error for an unrecognized POSIX class name. This support is
	not compatible with Perl. It is provided to help migrations from other
	environments, and is best not used in any new patterns. Note that \eb matches
	at the start and the end of a word (see
	.\" HTML <a href="#smallassertions">
	.\" </a>
	"Simple assertions"
	.\"
	above), and in a Perl-style pattern the preceding or following character
	normally shows which is wanted, without the need for the assertions that are
	used above in order to give exactly the POSIX behaviour.
	.
	.
.SH "VERTICAL BAR"	.SH "VERTICAL BAR"
.rs	.rs
.sp	.sp
Line 1547 conditions,	Line 1644 conditions,
.\"	.\"
can be made by name as well as by number.	can be made by name as well as by number.
.P	.P
Names consist of up to 32 alphanumeric characters and underscores. Named	Names consist of up to 32 alphanumeric characters and underscores, but must
capturing parentheses are still allocated numbers as well as names, exactly as	start with a non-digit. Named capturing parentheses are still allocated numbers
if the names were not present. The PCRE API provides function calls for	as well as names, exactly as if the names were not present. The PCRE API
extracting the name-to-number translation table from a compiled pattern. There	provides function calls for extracting the name-to-number translation table
is also a convenience function for extracting a captured substring by name.	from a compiled pattern. There is also a convenience function for extracting a
	captured substring by name.
.P	.P
By default, a name must be unique within a pattern, but it is possible to relax	By default, a name must be unique within a pattern, but it is possible to relax
this constraint by setting the PCRE_DUPNAMES option at compile time. (Duplicate	this constraint by setting the PCRE_DUPNAMES option at compile time. (Duplicate
Line 1577 for the first (and in this example, the only) subpatte	Line 1675 for the first (and in this example, the only) subpatte
matched. This saves searching to find which numbered subpattern it was.	matched. This saves searching to find which numbered subpattern it was.
.P	.P
If you make a back reference to a non-unique named subpattern from elsewhere in	If you make a back reference to a non-unique named subpattern from elsewhere in
the pattern, the one that corresponds to the first occurrence of the name is	the pattern, the subpatterns to which the name refers are checked in the order
used. In the absence of duplicate numbers (see the previous section) this is	in which they appear in the overall pattern. The first one that is set is used
the one with the lowest number. If you use a named reference in a condition	for the reference. For example, this pattern matches both "foofoo" and
	"barbar" but not "foobar" or "barfoo":
	.sp
	(?:(?<n>foo)\|(?<n>bar))\ek<n>
	.sp
	.P
	If you make a subroutine call to a non-unique named subpattern, the one that
	corresponds to the first occurrence of the name is used. In the absence of
	duplicate numbers (see the previous section) this is the one with the lowest
	number.
	.P
	If you use a named reference in a condition
test (see the	test (see the
.\"	.\"
.\" HTML <a href="#conditions">	.\" HTML <a href="#conditions">
Line 1599 documentation.	Line 1708 documentation.
\fBWarning:\fP You cannot use different names to distinguish between two	\fBWarning:\fP You cannot use different names to distinguish between two
subpatterns with the same number because PCRE uses only the numbers when	subpatterns with the same number because PCRE uses only the numbers when
matching. For this reason, an error is given at compile time if different names	matching. For this reason, an error is given at compile time if different names
are given to subpatterns with the same number. However, you can give the same	are given to subpatterns with the same number. However, you can always give the
name to subpatterns with the same number, even when PCRE_DUPNAMES is not set.	same name to subpatterns with the same number, even when PCRE_DUPNAMES is not
	set.
.	.
.	.
.SH REPETITION	.SH REPETITION
Line 2271 This makes the fragment independent of the parentheses	Line 2381 This makes the fragment independent of the parentheses
.sp	.sp
Perl uses the syntax (?(<name>)...) or (?('name')...) to test for a used	Perl uses the syntax (?(<name>)...) or (?('name')...) to test for a used
subpattern by name. For compatibility with earlier versions of PCRE, which had	subpattern by name. For compatibility with earlier versions of PCRE, which had
this facility before Perl, the syntax (?(name)...) is also recognized. However,	this facility before Perl, the syntax (?(name)...) is also recognized.
there is a possible ambiguity with this syntax, because subpattern names may
consist entirely of digits. PCRE looks first for a named subpattern; if it
cannot find one and the name consists entirely of digits, PCRE looks for a
subpattern of that number, which must be greater than zero. Using subpattern
names that consist entirely of digits is not recommended.
.P	.P
Rewriting the above example to use a named subpattern gives this:	Rewriting the above example to use a named subpattern gives this:
.sp	.sp
Line 2698 During matching, when PCRE reaches a callout point, th	Line 2803 During matching, when PCRE reaches a callout point, th
called. It is provided with the number of the callout, the position in the	called. It is provided with the number of the callout, the position in the
pattern, and, optionally, one item of data originally supplied by the caller of	pattern, and, optionally, one item of data originally supplied by the caller of
the matching function. The callout function may cause matching to proceed, to	the matching function. The callout function may cause matching to proceed, to
backtrack, or to fail altogether. A complete description of the interface to	backtrack, or to fail altogether.
the callout function is given in the	.P
	By default, PCRE implements a number of optimizations at compile time and
	matching time, and one side-effect is that sometimes callouts are skipped. If
	you need all possible callouts to happen, you need to set options that disable
	the relevant optimizations. More details, and a complete description of the
	interface to the callout function, are given in the
.\" HREF	.\" HREF
\fBpcrecallout\fP	\fBpcrecallout\fP
.\"	.\"
Line 3060 example:	Line 3170 example:
.sp	.sp
...(COMMIT)(PRUNE)...	...(COMMIT)(PRUNE)...
.sp	.sp
If there is a matching failure to the right, backtracking onto (*PRUNE) cases	If there is a matching failure to the right, backtracking onto (*PRUNE) causes
it to be triggered, and its action is taken. There can never be a backtrack	it to be triggered, and its action is taken. There can never be a backtrack
onto (*COMMIT).	onto (*COMMIT).
.	.
Line 3145 Cambridge CB2 3QH, England.	Line 3255 Cambridge CB2 3QH, England.
.rs	.rs
.sp	.sp
.nf	.nf
Last updated: 26 April 2013	Last updated: 03 December 2013
Copyright (c) 1997-2013 University of Cambridge.	Copyright (c) 1997-2013 University of Cambridge.
.fi	.fi

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