Book Image

Mastering Linux Shell Scripting

By : Andrew Mallett
Book Image

Mastering Linux Shell Scripting

By: Andrew Mallett

Overview of this book

Shell scripting is a quick method to prototype a complex application or a problem by automating tasks when working on Linux-based systems. Using both simple one-line commands and command sequences complex problems can be solved with ease, from text processing to backing up sysadmin tools. In this book, you’ll discover everything you need to know to master shell scripting and make informed choices about the elements you employ. Get to grips with the fundamentals of creating and running a script in normal mode, and in debug mode. Learn about various conditional statements' code snippets, and realize the power of repetition and loops in your shell script. Implement functions and edit files using the Stream Editor, script in Perl, program in Python – as well as complete coverage of other scripting languages to ensure you can choose the best tool for your project.
Table of Contents (21 chapters)
Mastering Linux Shell Scripting
About the Author
About the Reviewer

Chapter 6. Iterating with Loops

Remember, scripts are for lazy people. We are the folk of the world who have better things to do than repeat a task 100 times or more; loops are our friends.

Looping structures are the life-blood of scripts. These loops are the workhorse engine 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, the reliability factor and accuracy will fail very quickly.

So let's see how we can save our time and sanity by covering the following topics in this chapter:

  • For loops

  • Loop control

  • While and until

  • Read from file

  • Operator menu