Character Meaning
\a Beep
\n Newline character
\r Carriage return
\t Tab
\f Formfeed
\e Escape
\d Digit (same as [0-9])
\D Nondigit character (same as [^0-9])
\w Word character (same as [a-zA-Z0-9_])
\W Nonword character
\s White-space character (same as [ \t\n\r\f])
\S Non White-space character
\xX Hexadecimal digit
\cX Matches the corresponding control character