In order to successfully work with the Linux sed editor and the awk command in your shell scripts, you have to understand regular expressions or in short regex. Since there are many engines for regex, we will use the shell regex and see the bash power in working with regex.

First, we need to understand what regex is, then we will see how to use it.

Table of contents include:

What is regex, Types of regex, Define BRE Patterns, Special Characters, Anchor Characters, The dot Character, Character Classes, Negating Character Classes, Using Ranges, Special Character Classes, The Asterisk, Extended Regular Expressions, The question mark, The Plus Sign, Curly Braces, Pipe Symbol, Grouping Expressions, Practical examples, Counting Directory Files, Validating E-mail Address.