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

When in doubt – Quote!

Having established that variables are a type of parameter, we should always keep this in mind, especially, when reading manuals and HOWTOs. Often the documentation refers to parameters and in doing so they include variables, as well as, the bash special parameters, such as $1 and so on. In keeping with this, we will look at why it is advisable to quote the parameters when we use them on the command line or within scripts. Learning this now can save us a lot of pain and heartache later, especially, when we start looking at loops.

First, the correct term that we should use for reading the value of variables is parameter expansion. To you and me this is reading a variable, but to bash this would be too simple. The assignment of a correct name, such as parameter expansion reduces any ambiguity to its meaning but adds complexity at the same time. In the following example, the first line of code assigns the value of fred to the name parameter. The second line of code uses...