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Linux Command Line and Shell Scripting Techniques

Linux Command Line and Shell Scripting Techniques

By : Vedran Dakic, Jasmin Redzepagic
4.4 (5)
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Linux Command Line and Shell Scripting Techniques

Linux Command Line and Shell Scripting Techniques

4.4 (5)
By: Vedran Dakic, Jasmin Redzepagic

Overview of this book

Linux Command Line and Shell Scripting Techniques begins by taking you through the basics of the shell and command-line utilities. You’ll start by exploring shell commands for file, directory, service, package, and process management. Next, you’ll learn about networking - network, firewall and DNS client configuration, ssh, scp, rsync, and vsftpd, as well as some network troubleshooting tools. You’ll also focus on using the command line to find and manipulate text content, via commands such as cut, egrep, and sed. As you progress, you'll learn how to use shell scripting. You’ll understand the basics - input and output, along with various programming concepts such as loops, variables, arguments, functions, and arrays. Later, you’ll learn about shell script interaction and troubleshooting, before covering a wide range of examples of complete shell scripts, varying from network and firewall configuration, through to backup and concepts for creating live environments. This includes examples of performing scripted virtual machine installation and administration, LAMP (Linux, Apache, MySQL, PHP) stack provisioning and bulk user creation for testing environments. By the end of this Linux book, you’ll have gained the knowledge and confidence you need to use shell and command-line scripts.
Table of Contents (19 chapters)
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Checking if you're running as root

There are different ways of checking if we're running a script as root. We can use environment variables, just as we can use the whoami or id commands to check if it equals root/number 0 or not.

Getting ready

We'll continue using the cli1 machine for this recipe, so make sure that it's powered on.

How to do it…

Let's create a short snippet of Bash shell script code that's going to help us find out whether we're running a script as root or not. It's a rather simple thing to do in Linux, considering that we have easy access to an environment variable called EUID, and reading its value is enough to determine whether we're running as root (EUID=0) or not (EUID value > 1):

#!/bin/bash
# V1.0 / Jasmin Redzepagic / 01/11/2021 Initial script version 
# Distribution allowed under GNU Licence V2.0 
# First, we need to check if our environment variable UID is set to
# 0 or not and branch...

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