What are Regular Expressions?

Regular Expressions are search patterns for "Regular Text". They are used by many different tools and languages, including the Linux grep command, the Windows findstr command, less, vi/vim, sed, awk, perl, python, and many others.

Why should we use Regular Expressions?

Regular Expressions (regexp or regex) can be a little daunting to learn: they often look like someone was just bashing their head against the keyboard (or, like a cat was walking across the keyboard). But they are very powerful: a well-written regular expression can replace many pages of code in a programming language such as C or C++, and so it is worth investing some time to understand them.