Book Image

Learn Linux Shell Scripting – Fundamentals of Bash 4.4

By : Sebastiaan Tammer
Book Image

Learn Linux Shell Scripting – Fundamentals of Bash 4.4

By: Sebastiaan Tammer

Overview of this book

Shell scripts allow us to program commands in chains and have the system execute them as a scripted event, just like batch files. This book will start with an overview of Linux and Bash shell scripting, and then quickly deep dive into helping you set up your local environment, before introducing you to tools that are used to write shell scripts. The next set of chapters will focus on helping you understand Linux under the hood and what Bash provides the user. Soon, you will have embarked on your journey along the command line. You will now begin writing actual scripts instead of commands, and will be introduced to practical applications for scripts. The final set of chapters will deep dive into the more advanced topics in shell scripting. These advanced topics will take you from simple scripts to reusable, valuable programs that exist in the real world. The final chapter will leave you with some handy tips and tricks and, as regards the most frequently used commands, a cheat sheet containing the most interesting flags and options will also be provided. After completing this book, you should feel confident about starting your own shell scripting projects, no matter how simple or complex the task previously seemed. We aim to teach you how to script and what to consider, to complement the clear-cut patterns that you can use in your daily scripting challenges.
Table of Contents (24 chapters)
Title Page
About Packt
Contributors
Preface
Free Chapter
1
Introduction
Index

Interactive versus non-interactive scripts


The script we have created so far uses user input, but it can't really be called interactive. As soon as the script is fired off, with or without arguments to the parameters, the script runs and completes.

But what if we do not want to use a long list of arguments, instead prompting the user for the information that is needed?

Enter the read command. The basic usage of read looks at input from the command line, and stores it in the REPLY variable. Try it out yourself:

reader@ubuntu:~$ read
This is a random sentence!
reader@ubuntu:~$ echo $REPLY
This is a random sentence!
reader@ubuntu:~$

After you start the read command, your terminal will go down a line and allow you to type anything you want. As soon as you hit Enter (or, actually, until Bash encounters the newline key), the input will be saved into the REPLY variable. You can then echo this variable to verify it has actually stored your text.

read has a few interesting flags which make it more usable...