Book Image

Mastering Bash

By : Giorgio Zarrelli
Book Image

Mastering Bash

By: Giorgio Zarrelli

Overview of this book

System administration is an everyday effort that involves a lot of tedious tasks, and devious pits. Knowing your environment is the key to unleashing the most powerful solution that will make your life easy as an administrator, and show you the path to new heights. Bash is your Swiss army knife to set up your working or home environment as you want, when you want. This book will enable you to customize your system step by step, making your own real, virtual, home out of it. The journey will take you swiftly through the basis of the shell programming in Bash to more interesting and challenging tasks. You will be introduced to one of the most famous open source monitoring systems—Nagios, and write complex programs with it in any languages. You’ll see how to perform checks on your sites and applications. Moving on, you’ll discover how to write your own daemons so you can create your services and take advantage of inter-process communication to let your scripts talk to each other. So, despite these being everyday tasks, you’ll have a lot of fun on the way. By the end of the book, you will have gained advanced knowledge of Bash that will help you automate routine tasks and manage your systems.
Table of Contents (15 chapters)

Assignment operators

We have seen how to manipulate the value assigned to a variable and an integer so far, and then reassign this value to another variable or the same one. But why use two operations when you can alter the value of a variable and reassign it at the same time using the assignment operators?

The += operator

This operator adds a quantity to the value of the variable and assigns the outcome to the variable itself, but to clarify its use, let's rewrite one of the examples we've seen before:

#!/bin/bash    
echo "Hello user, please give me a number: "
read user_input
echo "And now another one, please: "

Adding

echo "The user_input variable value is: ${user_input}"
echo...