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)

Exiting the loop with break and continue

This gives us some nice opportunities, such as infinite loops:

while true ; do echo "Hello" ; done

Since true always evaluates as true, the condition is always verified so we have an infinite execution of the do/done clause; press Ctrl+ C to exit from the loop. An infinite loop looks like something nasty, but it opens a new scenario for our scripts, since we can make them run or wait for something for as long as we want. Actually, if we do not use a couple of loop control commands: break will exit the loop and continue will restart it, jumping over the remaining commands. Let's see an example of creating a hypothetical backup program menu:

#!/bin/bash
while true
do
clear
cat <<MENU
BACKUP UTIL v 1.0
------------------
1. Backup a file/directory
2. Restore a file/directory
0. Quit
------------------
MENU
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