User`s guide

Appendix A About Regular Expressions ■ 71
Appendix A About Regular Expressions
The Barracuda Spam Firewall lets you use regular expressions in many of its features. Regular
Expressions allow you to flexibly describe text so that a wide range of possibilities can be matched.
Note the following when using regular expressions:
■ Be careful when using special characters such as |, *, '.' in your text. For more information, refer to
Using Special Characters in Expressions on page 72.
■ All matches are case-insensitive.
The following table describes the most common regular expressions supported by the Barracuda Spam
Firewall.
Expression Matches...
Operators
* Zero or more occurrences of the character immediately preceding.
+ One or more occurrences of the character immediately preceding.
? Zero or one occurrence of the character immediately preceding.
| Either of the characters on each side of the pipe.
( ) Characters between the parenthesis as a group.
Character Classes
. Any character except newline
[ac] Letter 'a' or letter 'c'
[^ac] Anything but letter 'a' or letter 'c'
[a-z] Letters 'a' through 'z'
[a-zA-Z.] Letters 'a' through 'z' or 'A' through 'Z' or a dot
[a-z\-] Letters 'a' through 'z' or a dash
\d Digit, shortcut for [0-9]
\D Non-digit, shortcut for [^0-9]
\a Digit, shortcut for [0-9]
\w Part of word: shortcut for [A-Za-z0-9_]
\W Non-word character: shortcut for [^\w]
\s Space character: shortcut for [ \n\r\t]
\S Non-space character: shortcut for [^\s]
Miscellaneous
^ Beginning of line
$ End of line
\b Word boundary
\t Tab character