In this article, I’ll provide a functional introduction to four important concepts and tools for sculpting text: regex, grep, sed and awk.

• regex is a language for describing patterns in strings; 
• grep filters its input against a pattern;
• sed applies transformation rules to each line; and
• awk manipulates an ad hoc database stored as text, e.g. CSV files.

Link: Sculpting text with regex, grep, sed and awk