Regular Expressions

Although not a complete description, the following table summarises the supported regular expression features:

Element	Description
*	Match zero or more occurrences of the preceeding element
+	Match one or more occurrences of the preceeding element
?	Match zero or one occurrence of the preceeding element
{m}	Match exactly m elements
{m,}	Match at least m elements
{m,n}	Match at least m but no more than n elements
.	Match any character
[]	Match any one of the characters within the brackets. Use a caret (^) to specify a non-matching character
()	Match a group of characters
[:class:]	Match to a defined class of characters (use within brackets).

The character class element [:class:] adds all of the characters in a named class to the character set in a bracketed expression. The following table defines the supported class types:

Class	Description
alnum	Lower case letters, upper case letters, and digits.
alpha	Lower case letters, and upper case letters.
blank	Space or tab.
digit	Digits.
graph	Lower case letters, upper case letters, digits, and punctuation.
lower	Lower case letters.
print	Lower case letters, upper case letters, digits, punctuation and space.
punct	Punctuation.
space	Space.
upper	Upper case letters.
xdigit	Hexadecimal digits.