Mastering Linux Shell Scripting - Second Edition

Iterating with Loops

Now we can perform arithmetic operations and tests and our scripts have more control. Sometimes, you will find that you need to perform some tasks repeatedly, such as going through log file entries and performing an action, or maybe running a piece of code continuously. We are busy people who have better things to do than repeat a task 100 times or more; loops are our friends.

Looping structures are the lifeblood of scripts. These loops are workhorse engines that can iterate many times, repeating the same task reliably and consistently. Imagine having 100,000 lines of text within a CSV file that has to be checked for incorrect entries. A script can do this easily and accurately once developed but, in the case of a human, ...