Loops

Part of the Bash course

So far every script you have written runs each line exactly once, top to bottom. That is fine for short scripts, but real work is repetitive: rename fifty files, check ten servers, print a greeting for everyone on a list. Typing the same command fifty times is not a plan. A loop is a block of commands that Bash repeats, either once for every item in a list or for as long as a condition holds true.

Picture a stack of index cards on your desk, one name per card. Reading them out loud one at a time, in order, until the stack is empty, is exactly what a for loop does with a list of words. You already know how to test one value with if. A for loop is what you reach for when you want to run the same commands against many values instead of just one. ...