\c matches following (hexadecimal value shown in parenthesis):

   \a == bell (alert)    ( \x07 )
   \b == backspace       ( \x08 )
   \f == formfeed        ( \x0c )
   \n == newline         ( \x0a )
   \r == carriage return ( \x0d )
   \s == space           ( \x20 )
   \t == horizontal tab  ( \x09 )
   \v == vertical   tab  ( \x0b )
   \c == c [ \\ == \ ]
   \ooo == character represented by octal value ooo
           1 to 3 octal digits acceptable
   \xhh == character represented by hexadecimal value hh
           1 or 2 hexadecimal digits acceptable