Book Image

Linux Command Line and Shell Scripting Techniques

By : Vedran Dakic, Jasmin Redzepagic
Book Image

Linux Command Line and Shell Scripting Techniques

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)

Logical looping with and, or, and not

There is no way to escape logic when it comes to computers. We already dealt with some things you can do with evaluating conditions, but there is a lot more that can be done in bash.

In this recipe, we are going to deal with different logical operators that help us with scripting in general. First, we are going to deal with what can be done on the command line, and then we are going to use that in scripts.

Getting ready

First, let's quickly talk about logic operators. So far, we mentioned expressions that have a value of true and false. We also mentioned a lot of different expressions that are built into bash, since they provide functionality crucial for everyday work on the command line. Now is the time to talk about logical operators that help us combine expressions and create complex solutions. We are going to start with the usual operators:

  • && (the logical AND)
  • || (the logical OR)

The interesting...