Expression	Description
[ ]	may also be used on a range of characters separated by a – character.
[0-9]	matches any digit.
[a-z]	matches any alpha character
[a-z0-9]	matches any alphanumeric character
^	is the "not" character, so [^0-9] matches against any character that is not a digit.

Expression	Description
.	matches against any character
\d	matches against a digit [0-9]
\D	matches against a non-digit [^0-9]
\s	matches against a whitespace character (such as a tab, space, or line feed character)
\S	matches against a non-whitespace character
\w	matches against an alphanumeric character [a-zA-Z_0-9]
\W	matches against a non-alphanumeric character
\xhh	matches against a control character (for the hexadecimal character hh)
\uhhhh	matches against a Unicode character (for the hexadecimal character hhhh)

Note  As the backslash character is used to denote a specific search expression, if you want to match against this character, you must enter a double backslash (\\).

Expression	Description
*	matches against zero or more occurrences of the previous character or expression
+	matches against one or more occurrences of the previous character or expression
?	matches zero or one occurrences of the previous character or expression
{n}	matches n occurrences of the previous character or expression
{n,m}	matches from n to m occurrences of the previous character or expression
{n,}	matches at least n occurrences of the previous character or expression