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 arrays

It's sometimes the case that we'd like to store a set of multiple values in one variable, where we don't know how many there might be at the time we start the program, especially sets of filenames. Unfortunately, it's not safe to store a set of filenames in a simple string variable, even when separated by newlines, because a newline is itself a valid character for filenames there's no safe choice of delimiter for the data, because we can't use null bytes in shell words.

Fortunately, Bash provides arrays to allow us to do this:

bash$ fruits=('apple' 'banana' 'cherry')
Arrays are not specified at all as part of POSIX shell. They are a feature specific to Bash.

Note that we separate the parts of the array only with spaces, not commas, and we do not quote the parentheses; they are part of the syntax...