Literals

Any character not a meta-character of the regex syntax is matched literally. This is true for any character, even a space is significant unless you also specify the free form mode modifier. If you need to match literally a meta-character, you can precede it by the backslash (\) meta-character.

For regex stored in string, you should also be careful about the meta-characters specifics to literal string in the host language. To match a backslash in a regex, you need two backlashes (/\\/) [1].

Meta-character used to match special characters

For convenience, most implementation also define character shorthands for useful control characters:

Shorthand	Mnemonic	ASCII code	Matches
\a	Alert	0x07	Ctrl-G, the BEL control character
\b	Backspace	0x08	Ctrl-H, the BS control character. The meaning of this shorthand is usually restricted to character classes. Outside character classes, \b means word-boundaries
\e	Escape	0x1B	Ctrl-[, the ESC control character
\f	Form feed	0x0C	the FF control character
\n	Newline	0x0A	usualy the LF control character, except for MacOS systems that match ASCII 0x0C
\r	Carriage return	0x0C	usualy the CR control character, except for MacOS systems that match ASCII 0x0A
\t	Tabulation	0x09	the HT control character
\v	Vertical tabulation	0x0B	the HT control character
\nnn	Octal code		any character represented as an octal value, ie: \012 and \n are equivalent. The number of digit following \ is usually fixed to 3.
\x{nn} or \x{nnn}	Hexadecimal code		any character represented as an hexadecimal value, ie: \x0A and \n are equivalent. The number of digit following \x is usually fixed to 2 or 4.
\unnnn	Unicode character		any unicode character represented as an hexadecimal value, ie: \x000A and \n are equivalent. The number of digit following \u is usually fixed to 4 (or 8).
\cchar	Control character		any control character represented by its corresponding control letter, ie: \cJ and \n are equivalent.

Literals

Meta-character used to match special characters

See also...