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)

Using variables

The basic form of a variable assignment in shell script looks like this:

myshell='GNU Bourne-Again shell'

This declares a variable named myshell, and gives it the string contents GNU Bourne-Again shell.

Note that there is no space either before or after the equals sign, as there might be in a C-like language. Note also that the value in this example assignment is surrounded by single quotes, so the contents are interpreted literally, without expanding any special characters, in this case spaces. As with other single-quoted strings in shell script, the quotes themselves do not become part of the value.

You will need to quote any value that contains special characters in variable assignments. For new shell programmers, it is safest to quote all the values in their assignments; it might be unnecessary in some cases, but it doesn't do any harm, and...