Characters

REGULAR EXPRESSION	DESCRIPTION
. (dot)	Any character (byte) except newline
x	The character 'x'
\\	The character '\'
\a	The alert (bell) character (ASCII 0x07)
\b	If this meta-symbol is within square brackets [] or by itself, it will be treated as the backspace character (ASCII 0x08). For example, [\b] or \b If this meta-symbol is at the beginning (or end) of a regular expression, it means any matched string of the regular expression must check whether the left (or right) side of the matched string is a boundary. For example: \bluck > left side must be the boundary luck\b > right side must be the boundary \bluck\b > both sides must be the boundary If this meta-symbol appears in the middle of a regular expression, it will cause a syntax error.
\f	The form-feed character (ASCII 0x0C)
\n	The newline (line feed) character (ASCII 0x0A)
\r	The carriage-return character (ASCII 0x0D)
\t	The normal (horizontal) tab character (ASCII 0x09)
\v	The vertical tab character (ASCII 0x0B)
\n	The character with octal value 0n (0 <= n <= 7)
\nn	The character with octal value 0nn (0 <= n <= 7)
\mnn	The character with octal value 0mnn (0 <= m <= 3, 0 <= n <= 7)
\xhh	The character with a hexadecimal value 0xhh, for example, \x20 means the space character

Tip:

If your expression includes the characters \ | ( ) { } [ ] . ^ $ * + or ?, you must escape them by using a \ immediately before the character. Otherwise, they will be assumed to be regular expression operators rather than literal characters.