Linux Shell Scripting Cookbook - Third Edition

How it works...

Regular expressions are easy to design part-by-part. In the e-mail regex, we all know that an e-mail address takes the [e-mail]_2-4_letter_suffix form. Writing this pattern in the regex language will look like this:

[A-Za-z0-9.]+@[A-Za-z0-9.]+\.[a-zA-Z]{2,4} 

[A-Za-z0-9.]+ means we need one or more characters in the [] block (+ means at least one, maybe more). This string is followed by an @ character. Next, we will see the domain name, a string of letters or numbers, a period, and then 2-4 more letters. The [A-Za-z0-9]+ pattern defines an alpha-numeric string. The \. pattern means that a literal period must appear. The [a-zA-Z]{2,4} pattern defines 2, 3, or 4 letters.

An HTTP URL is similar to an e-mail, but we don't ...