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

Read, write, and execute


In the previous chapter, we discussed the Linux filesystem and the different types with which Linux implements the everything is a file philosophy. However, we did not look at permissions on those files. As you might have guessed, in a multi-user system such as a Linux server, it is not a particularly great idea that users can access files which are owned by other users. Where would the privacy be in that?

The Linux permissions scheme is actually at the heart of the Linux experience, as far as we are concerned. Just as (almost) everything is handled as a file in Linux, all of those files have a distinct set of permissions accompanying them. While exploring the file system in the previous chapter, we limited ourselves to files that were viewable by either everyone or by the currently logged in user. However, there are many files that are only viewable or writable by the root user: often, these are sensitive files such as /etc/shadow (which contains the hashed passwords...