Examples of regular expressions

The following examples walk you through creating regular expressions for a number of different formats.

MAC addresses

Media Access Control (MAC) is a unique identifier for network interface addresses with 6-byte fields normally written in hexadecimal.

Tools such as ipconfig show the value of a MAC address with each hexadecimal byte separated by a hyphen, for example, 1a-2b-3c-4d-5f-6d.

Linux or Unix-based systems tend to separate each hexadecimal byte with :. This includes the Linux and Unix variants, VMWare, JunOS (Juniper network device operating system, based on FreeBSD), and so on, for example, 1a:2b:3c:4d:5f:6d.

Cisco IOS shows a MAC address as three two-byte pairs separated by a period (.), for example, 1c2b.3c4d.5f6d.

A regular expression can be created to simultaneously match all of these formats.

To match a single hexadecimal character, the following character class may be used:

[0-9a-f]

To account for the first two formats, a pair of hexadecimal characters...