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)

Arrays

Think of an array as a structure that can hold more than a single object, something like a variable with one or many values. Imagine you have a few friends and you want to write down their names:

friend_1=Anthony
friend_2=Mike
friend_3=Noel
friend_4=Tarek
friend_5=Dionysios

Once you have the variables instanced, you can then deference them, deferencing being the act of retrieving a value. This is OK, but it somehow cages you into some limitations, such as you must call the exact variable name to access its value, you cannot easily cycle between them, you cannot tell the number of values so quickly, and more. For such operations, there is an appropriate structure, which comes at hand and allows us to work on the values as a single entity--this is the array:

friends=(Anthony Mike Noel Tarek Dionysios)

The elements inside an array are indexed, and its position is assigned during...