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)

Using functions in menus

In Chapter 6, Iterating with Loops, we created the menu.sh file. Menus are great targets to use functions, as the case statement is maintained very simply with single-line entries, while the complexity can still be stored in each function. We should consider creating a function for each menu item. If we copy the previous $HOME/bin/menu.sh to $HOME/bin/menu2.sh, we can improve the functionality. The new menu should look like the following code:

#!/bin/bash 
# Author: @likegeeks 
# Web: likegeeks.com 
# Sample menu with functions 
# Last Edited: April 2018 
 
to_lower() { 
    input="$1" 
    output=$( echo $input | tr [A-Z] [a-z]) 
return $output 
} 
 
do_backup() { 
    tar -czvf $HOME/backup.tgz ${HOME}/bin 
} 
 
show_cal() { 
    if [ -x /usr/bin/ncal ] ; then 
      command="/usr/bin/ncal -w" 
    else 
      command="/usr/bin...