I need to use
sed in the terminal (no other option, I'm afraid) and I need to find and replace all sequences of four or more digits (no white spaces) with a specific word "brad". I have tried and tried to understand the manual but it is just so bad.
How do I do this? And while I am looking for the exact command, I would appreciate an explanation of why it works the way it does (the exact command used here that is).