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)

Arithmetic operators

Arithmetic operators do what you think they do, that is, add, subtract, divide, and so on. It is something we are familiar with even without specific programming knowledge. Let's see each of them and how they can be used to manipulate the value of variables.

Before proceeding, keep in mind that for a shell script, a number is a decimal unless you prefix that with a 0 for the octal, a 0x for a hexadecimal number, or a base#number for a number that evaluates on the base.

The + operator

This is like what we see at primary school; this operator allows us to add an integer to the value of the variable, as we can see in the following example:

#!/bin/bash
echo "Hello user, please give me a number: &quot...