Learn Linux Shell Scripting - Fundamentals of Bash 4.4

What is a regular expression?

In essence, a regular expression is a piece of text that functions as a search pattern for other text. Regular expressions make it possible to easily say, for example, that I want to select all lines that contain a word that is five characters in length, or look for all files that end in .log.

An example might help with your understanding. First, we need a command that we can use to explore regular expressions. The most famous command used in Linux with regular expressions is grep.

grep is an acronym meaning global regular expression print. As you can see, this seems like a good candidate for explaining the concept!