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

Simple decision paths using command-line lists

We have used command-line lists both in Chapter 1, What and Why of Scripting with Bash of this book and in some of the scripts found in Chapter 2, Creating Interactive Scripts. Lists are one of the simplest conditional statements that we can create and so we thought that it was appropriate to use them in the earlier examples before fully explaining them here.

Command-line lists are two or more statements that are joined using either the AND or OR notations:

  • &&: AND

  • ||: OR

Where the two statements are joined using the AND notation, the second command only runs if the first command succeeds. Whereas, with the OR notation the second command will run only if the first command fails.

The decision of the success or failure of a command is taken by reading the exit code from the application. A zero represents a successful application completion and anything other than a zero will represent a failure. We can test the success or failure of an...