-If a pattern is compiled with the PCRE_EXTENDED option, whitespace in the +If a pattern is compiled with the PCRE_EXTENDED option, white space in the pattern (other than in a character class) and characters between a # outside a character class and the next newline are ignored. An escaping backslash can -be used to include a whitespace or # character as part of the pattern. +be used to include a white space or # character as part of the pattern.
If you want to remove the special meaning from a sequence of characters, you @@ -264,7 +264,7 @@ one of the following escape sequences than the binary \a alarm, that is, the BEL character (hex 07) \cx "control-x", where x is any ASCII character \e escape (hex 1B) - \f formfeed (hex 0C) + \f form feed (hex 0C) \n linefeed (hex 0A) \r carriage return (hex 0D) \t tab (hex 09) @@ -307,6 +307,8 @@ as just described only when it is followed by two hexa Otherwise, it matches a literal "x" character. In JavaScript mode, support for code points greater than 256 is provided by \u, which must be followed by four hexadecimal digits; otherwise it matches a literal "u" character. +Character codes specified by \u in JavaScript mode are constrained in the same +was as those specified by \x in non-JavaScript mode.
Characters whose value is less than 256 can be defined by either of the two @@ -406,12 +408,12 @@ Another use of backslash is for specifying generic cha
\d any decimal digit \D any character that is not a decimal digit - \h any horizontal whitespace character - \H any character that is not a horizontal whitespace character - \s any whitespace character - \S any character that is not a whitespace character - \v any vertical whitespace character - \V any character that is not a vertical whitespace character + \h any horizontal white space character + \H any character that is not a horizontal white space character + \s any white space character + \S any character that is not a white space character + \v any vertical white space character + \V any character that is not a vertical white space character \w any "word" character \W any "non-word" character@@ -497,7 +499,7 @@ The vertical space characters are:
U+000A Linefeed U+000B Vertical tab - U+000C Formfeed + U+000C Form feed U+000D Carriage return U+0085 Next line U+2028 Line separator @@ -520,7 +522,7 @@ This is an example of an "atomic group", details of wh below. This particular group matches either the two-character sequence CR followed by LF, or one of the single characters LF (linefeed, U+000A), VT (vertical tab, -U+000B), FF (formfeed, U+000C), CR (carriage return, U+000D), or NEL (next +U+000B), FF (form feed, U+000C), CR (carriage return, U+000D), or NEL (next line, U+0085). The two-character sequence is treated as a single unit that cannot be split. @@ -596,13 +598,16 @@ Armenian, Avestan, Balinese, Bamum, +Batak, Bengali, Bopomofo, +Brahmi, Braille, Buginese, Buhid, Canadian_Aboriginal, Carian, +Chakma, Cham, Cherokee, Common, @@ -645,7 +650,11 @@ Lisu, Lycian, Lydian, Malayalam, +Mandaic, Meetei_Mayek, +Meroitic_Cursive, +Meroitic_Hieroglyphs, +Miao, Mongolian, Myanmar, New_Tai_Lue, @@ -664,8 +673,10 @@ Rejang, Runic, Samaritan, Saurashtra, +Sharada, Shavian, Sinhala, +Sora_Sompeng, Sundanese, Syloti_Nagri, Syriac, @@ -674,6 +685,7 @@ Tagbanwa, Tai_Le, Tai_Tham, Tai_Viet, +Takri, Tamil, Telugu, Thaana, @@ -812,7 +824,7 @@ PCRE_UCP is set. They are: Xwd Any Perl "word" characterXan matches characters that have either the L (letter) or the N (number) -property. Xps matches the characters tab, linefeed, vertical tab, formfeed, 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. Xsp is the same as Xps, except that vertical tab is excluded. Xwd matches the same characters as Xan, plus underscore. @@ -1008,7 +1020,8 @@ used. Because \C breaks up characters into individual unit with \C in a UTF mode means that the rest of the string may start with a malformed UTF character. This has undefined results, because PCRE assumes that 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). +start of processing unless the PCRE_NO_UTF8_CHECK or PCRE_NO_UTF16_CHECK option +is used).
PCRE does not allow \C to appear in lookbehind assertions @@ -1818,7 +1831,7 @@ Because there may be many capturing parentheses in a p following a backslash are taken as part of a potential back reference number. If the pattern continues with a digit character, some delimiter must be used to terminate the back reference. If the PCRE_EXTENDED option is set, this can be -whitespace. Otherwise, the \g{ syntax or an empty comment (see +white space. Otherwise, the \g{ syntax or an empty comment (see "Comments" below) can be used.
@@ -2160,7 +2173,7 @@ point in the pattern; the idea of DEFINE is that it ca subroutines that can be referenced from elsewhere. (The use of subroutines is described below.) For example, a pattern to match an IPv4 address such as -"192.168.23.245" could be written like this (ignore whitespace and line +"192.168.23.245" could be written like this (ignore white space and line breaks):(?(DEFINE) (?<byte> 2[0-4]\d | 25[0-5] | 1\d\d | [1-9]?\d) ) @@ -2554,18 +2567,22 @@ exception: the name from a *(MARK), (*PRUNE), or (*THE a successful positive assertion is passed back when a match succeeds (compare capturing parentheses in assertions). Note that such subpatterns are processed as anchored at the point where they are tested. Note also that Perl's -treatment of subroutines is different in some cases. +treatment of subroutines and assertions is different in some cases.Note that in this unanchored example the mark is retained from the match -attempt that started at the letter "X". Subsequent match attempts starting at -"P" and then with an empty string do not get as far as the (*MARK) item, but -nevertheless do not reset it. +attempt that started at the letter "X" in the subject. Subsequent match +attempts starting at "P" and then with an empty string do not get as far as the +(*MARK) item, but nevertheless do not reset it. +The new verbs make use of what was previously invalid syntax: an opening parenthesis followed by an asterisk. They are generally of the form (*VERB) or (*VERB:NAME). Some may take either form, with differing behaviour, depending on whether or not an argument is present. A name is any sequence of -characters that does not include a closing parenthesis. If the name is empty, -that is, if the closing parenthesis immediately follows the colon, the effect -is as if the colon were not there. Any number of these verbs may occur in a -pattern. -
+characters that does not include a closing parenthesis. The maximum length of +name is 255 in the 8-bit library and 65535 in the 16-bit library. If the name +is empty, that is, if the closing parenthesis immediately follows the colon, +the effect is as if the colon were not there. Any number of these verbs may +occur in a pattern. + +
+Optimizations that affect backtracking verbs +
PCRE contains some optimizations that are used to speed up matching by running some checks at the start of each match attempt. For example, it may know the @@ -2574,7 +2591,12 @@ present. When one of these optimizations suppresses th included backtracking verbs will not, of course, be processed. You can suppress the start-of-match optimizations by setting the PCRE_NO_START_OPTIMIZE option when calling pcre_compile() or pcre_exec(), or by starting the -pattern with (*NO_START_OPT). +pattern with (*NO_START_OPT). There is more discussion of this option in the +section entitled +"Option bits for pcre_exec()" +in the +pcreapi +documentation.
Experiments with Perl suggest that it too has similar optimizations, sometimes @@ -2662,10 +2684,16 @@ After a partial match or a failed match, the name of t No match, mark = B
+If you are interested in (*MARK) values after failed matches, you should +probably set the PCRE_NO_START_OPTIMIZE option +(see above) +to ensure that the match is always attempted. +
-Last updated: 09 January 2012
+Last updated: 17 June 2012
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