These were great articles written by Peteris Krumins. I would have never thought that sed would be a turning complete language but it kinda makes sense now. Also check out his post on the busy beaver problem. His scripts are pretty fun to run.
A proof that Unix utility “sed” is Turing complete
The Busy Beaver Problem
Found this gem when trolling /r/Programming, it’s an IBM’s DeveloperWorks article on text manipulation in Unix. Always fun stuff.
It’s written by Brad Yoes and here is the link.
Also where is why I love DeveloperWorks articles, links to other content. Here is what you can find you fall down the rabbit hole.