In this chapter, we covered regular expressions and the regex engines BRE and ERE. We learned how to define patterns for them.

We learned how to write these patterns for sed, AWK, and grep.

Also, we saw how the special character classes make it easy to match sets of characters.

We saw how to use the powerful ERE patterns and how to group expressions.

Finally, we saw how to use the grep tool and how to define BRE and ERE patterns.

In the next two chapters, we will see some practical examples for AWK.