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

Using regular expressions

So far, we have maintained our use of regular expressions (RE) to simple text but there is, of course, a lot more to learn from them. Although people may often think that the RE seems like comic book profanity that you may see in a Batman fight, they do have a powerful meaning.

Working with alternate spellings

To start with, let's look at some anomalies in spelling. The word color may be spelled colour or color depending upon if we were working with UK English or US English. This can give rise to issues when searching for the word color, as it may be spelled in two ways. Implementing the following command will return only the first line containing the word color and not the second line:

$ echo -e "color\ncolour" | grep color

If we need to return both spellings, then we can use an RE operator. We will make use of the ? operator. You should be aware that in an RE the ? operator is not the same as in the shell. In an RE the ? operator means that the previous character...