#### Using Predefined Character Sets

To match a predefined character set, select the Pattern match check box. You can then search the text by using these special predefined character sets:

Character set | Characters in set
[[:alnum:]] | ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789
[[:alpha:]] | ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz
[[:blank:]] | (The space character and the tab character)
[[:digit:]] | 0123456789
[[:graph:]] | ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789!"#$%&'()*+,-./:;<=>?@[\]^_`{|}~
[[:lower:]] | Abcdefghijklmnopqrstuvwxyz
[[:print:]] | ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz 0123456789!"#$%&'()*+,-./:;<=>?@[\]^_`{|}~
[[:punct:]] | !"#$%&'()*+,-./:;<=>?@[\]^_`{|}~
[[:upper:]] | ABCDEFGHIJKLMNOPQRSTUVWXYZ
[[:xdigit:]] | 0123456789ABCDEFabcdef

Example: To search for a string which consists of a letter, followed by some letters or numbers, followed by that same first letter, you would use a back reference, as shown here: ([[:alpha:]])[[:alnum:]]\{1,\}\1.