Book Image

Bash Cookbook

By : Ron Brash, Ganesh Sanjiv Naik
Book Image

Bash Cookbook

By: Ron Brash, Ganesh Sanjiv Naik

Overview of this book

In Linux, one of the most commonly used and most powerful tools is the Bash shell. With its collection of engaging recipes, Bash Cookbook takes you through a series of exercises designed to teach you how to effectively use the Bash shell in order to create and execute your own scripts. The book starts by introducing you to the basics of using the Bash shell, also teaching you the fundamentals of generating any input from a command. With the help of a number of exercises, you will get to grips with the automation of daily tasks for sysadmins and power users. Once you have a hands-on understanding of the subject, you will move on to exploring more advanced projects that can solve real-world problems comprehensively on a Linux system. In addition to this, you will discover projects such as creating an application with a menu, beginning scripts on startup, parsing and displaying human-readable information, and executing remote commands with authentication using self-generated Secure Shell (SSH) keys. By the end of this book, you will have gained significant experience of solving real-world problems, from automating routine tasks to managing your systems and creating your own scripts.
Table of Contents (15 chapters)
Title Page
Copyright and Credits
Packt Upsell
Contributors
Preface
Index

Sanitizing user input and for repeatable results


One of the best practices for scripts (or programs, for that matter) is controlling user input, not only for security, but for controlling functionality in a way that input provides predictable results. For example, imagine a user who enters a number instead of a string. Did you check it? Will it cause your script to exit prematurely? Or will an unforeseen event occur such as the user entering rm -rf /* instead of a valid user name?

In any case, limiting program user input is also useful to you as the author because it can limit paths users take and reduce undefined behavior or bugs. Therefore, if quality assurance is important, test cases and input/output validation can be reduced.

Getting ready

This recipe might be introducing some readers to a concept they would like to avoid: software engineering. It's true, you are probably writing scripts to quickly get a task completed, but if your script is to be used by other people (or for a long time...