Awk

Notice, not all versions of awk are the same. GNU awk has some extra functionalities, mawk is faster.

http://www.theunixschool.com/2012/05/awk-match-pattern-in-file-in-linux.html

https://www.funtoo.org/Awk_by_Example,_Part_1

http://blog.jpalardy.com/posts/my-best-awk-tricks/

http://www.pement.org/awk/awk1line.txt