Book Image

Bash Quick Start Guide

By : Tom Ryder
Book Image

Bash Quick Start Guide

By: Tom Ryder

Overview of this book

Bash and shell script programming is central to using Linux, but it has many peculiar properties that are hard to understand and unfamiliar to many programmers, with a lot of misleading and even risky information online. Bash Quick Start Guide tackles these problems head on, and shows you the best practices of shell script programming. This book teaches effective shell script programming with Bash, and is ideal for people who may have used its command line but never really learned it in depth. This book will show you how even simple programming constructs in the shell can speed up and automate any kind of daily command-line work. For people who need to use the command line regularly in their daily work, this book provides practical advice for using the command-line shell beyond merely typing or copy-pasting commands into the shell. Readers will learn techniques suitable for automating processes and controlling processes, on both servers and workstations, whether for single command lines or long and complex scripts. The book even includes information on configuring your own shell environment to suit your workflow, and provides a running start for interpreting Bash scripts written by others.
Table of Contents (10 chapters)

Identifying the Bash version number

Before we start writing commands and programming with Bash, it's a good idea to find out what version of Bash you have installed. This is because newer versions of Bash have useful new features that might be discussed in this book, but that might not be available in your version of Bash.

You can check the version of your current running shell by printing the value of the BASH_VERSION variable:

bash$ declare -p BASH_VERSION
declare -- BASH_VERSION="4.4.12(1)-release"

You can get the same information by invoking the bash program with its --version option, which provides some extra information about the program's version number and software license:

$ bash --version
GNU bash, version 4.4.12(1)-release (x86_64-pc-linux-gnu)
Copyright (C) 2016 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <>

This is free software; you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.

The most recent stable minor version of GNU Bash at the time of writing is version 4.4, with version 4.4.0 released in September 2016.

In this book, we will focus on the features of Bash that were available in GNU Bash version 4.0, which was released in 2011, and is very widely available as a minimum version.

If the version of Bash installed on your computer is older than 4.0, some of the scripts and features discussed in this book may not work correctly. You or your system administrator should use your operating system to upgrade your Bash shell to a newer version.