Regular Expressions Language Elements

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Most of the important regular expression language operators are unescaped single characters. The escape character \ ( a single backslash ) signals to the regular expression parser that the character following the backslash is not an operator. For example, the parser treats an asterisk ( * ) as a repeating quantifier and a backslash followed by an asterisk ( \* ) as the Unicode character 002A.

The character escapes listed in this table are recognized both in regular expressions and in replacement patterns.

Escaped character	Meaning
ordinary characters	Characters other than . $ ^ { [ ( | ) * + ? \ match themselves.
\a	Matches a bell ( alarm ) \u0007.
\b	Matches backspace \u0008 if in [ ] Character Classes; otherwise, see the note following this table.
\t	Matches a tab \u0009.
\r	Matches a carriage return \u000D.
\v	Matches a vertical tab \u000B.
\f	Matches a form feed \u000C.
\n	Matches a new line \u000A.
\e	Matches an escape \u001B.
\040	Matches an ASCII character as octal ( up to three digits ); numbers with no leading zero are backreferences if they have only one digit or if they correspond to a capturing group number. ( See Backreferences. )    \040 represents a space.
\x20	Matches an ASCII character using hexadecimal representation ( exactly two digits ).
\cC	Matches an ASCII control character; for example, \cC is control-C.
\u0020	Matches a Unicode character using hexadecimal representation ( exactly four digits ).
\	When followed by a character that is not recognized as an escaped character, matches that character. For example, \* is the same as \x2A.

NOTE: The escaped character \b is a special case. In a regular expression, \b denotes a word boundary ( between \w and \W characters ) except within a [ ] character class, where \b refers to the backspace character. In a replacement pattern, \b always means backspace.

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