4.10.8.5 Regular Expression Specification

MetaCharacter	Description
.	Matches any single character.
[ ]	Indicates a character class. Matches any character inside the brackets (for example, [abc] matches "a", "b", and "c").
^	If this metacharacter occurs at the start of a character class, it negates the character class. A negated character class matches any character except those inside the brackets (for example, [^abc] matches all characters except "a", "b", and "c"). If ^ is at the beginning of the regular expression, it matches the beginning of the input (for example, ^[abc] will only match input that begins with "a", "b", or "c").
-	In a character class, indicates a range of characters (for example, [0-9] matches any of the digits "0" through "9").
?	Indicates that the preceding expression is optional: it matches once or not at all (for example, [0-9][0-9]? matches "2" and "12").
+	Indicates that the preceding expression matches one or more times (for example, [0-9]+ matches "1", "13", "666", and so on).
*	Indicates that the preceding expression matches zero or more times.
??, +?, *?	Non-greedy versions of ?, +, and .These match as little as possible, unlike the greedy versions which match as much as possible. Example: given the input "<abc><def>", <.?> matches "<abc>" while <.*> matches "<abc><def>".
( )	Grouping operator. Example: ([0-9]+,)*[0-9]+ matches a list of numbers separated by commas (such as "1" or "1,23,456").
\	Escape character: interpret the next character literally (for example, [0-9]+ matches one or more digits, but [0-9]\+ matches a digit followed by a plus character). Also used for abbreviations (such as \a for any alphanumeric character; see table below). If \ is followed by a number n, it matches the nth match group (starting from 0). Example: <{.?}>.?</\0> matches "<head>Contents</head>". Note that in C++ string literals, two backslashes must be used: "\\+", "\\a", "<{.?}>.?</\\0>".
$	At the end of a regular expression, this character matches the end of the input. Example: [0-9]$ matches a digit at the end of the input.
\|	Alternation operator: separates two expressions, exactly one of which matches (for example, T\|the matches "The" or "the").
!	Negation operator: the expression following ! does not match the input. Example: a!b matches "a" not followed by "b".

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Last updated 2015-02-05 15:17
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