Book Image

Mastering Linux Shell Scripting - Second Edition

By : Mokhtar Ebrahim, Andrew Mallett
5 (1)
Book Image

Mastering Linux Shell Scripting - Second Edition

5 (1)
By: Mokhtar Ebrahim, Andrew Mallett

Overview of this book

In this book, you’ll discover everything you need to know to master shell scripting and make informed choices about the elements you employ. Grab your favorite editor and start writing your best Bash scripts step by step. 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. You will also learn to write complex shell scripts. This book will also deep dive into file system administration, directories, and system administration like networking, process management, user authentications, and package installation and regular expressions. Towards the end of the book, you will learn how to use Python as a BASH Scripting alternative. By the end of this book, you will know shell scripts at the snap of your fingers and will be able to automate and communicate with your system with keyboard expressions.
Table of Contents (17 chapters)

Formatting output

We have remained faithful to the print command so far, as we have been limited in what we require from the output. If we want to print out, say, the username, UID, and default shell, we need to start formatting the output just a little. In this case, we can organize the output in well-shaped columns. Without formatting, the command we use will look similar to the following example, where we use commas to separate the field that we want to print:

$ awk ' BEGIN { FS=":" } { print $1,$3,$7 } ' /etc/passwd  

We use the BEGIN block here, as we can make use of it to print column headers later.

To understand the problem a little better, take a look at the following screenshot, which illustrates uneven column widths:

The issue that we have in the output is that the columns do not align, as the username is an inconsistent length. To improve on this...