Regular expressions can be used to craft complex matching and replacing rules. The Match String can be a Shell Regular Expression, which is a type of statement that matches or excludes based on the strings. An asterisk (*) in a Shell Regular Expression means “match all”.

A Shell Regular Expression is a sequence of characters. Any character, which is not a special character, matches itself. The following special characters are defined.

Character

Meaning
^

This can only be placed at the start of the string and means that the string must match at the start of the URL
$

This can only be placed at the end of the string and means that the string must match at the end of the URL
?

This matches any single character
*

This matches zero or more characters
[

This starts the set notation. This matches a single character which is contained within a set. If the set starts with ^, then this matches a single character which is not within the set

Shell Regular Expression Examples

Some examples of Shell Regular Expressions are below:

  • [0-9] matches any single digit
  • [^abf] matches any character, which is not “a”, “b” or “f”
  • ^/[^a-z] matches any first character in the URL which is not a small letter
  • home/*.gif matches any URL which points to a .gif file in the /home directory
  • [gG][iI][fF] matches any URL which contains the string “gif”, “GIF”, “gIF”, “giF”, “GiF”, and so on.
Note: Given an input URL such as /home/cgi-bin/XXX.cmd?value=hello, the end of the string used in matching is terminated by the ? character, therefore, a postfix string of cmd matches this URL, while a postfix of hello does not. To include the end of the string, enable the Include Query in URL option.