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)

Loops and Conditionals

In this chapter, we'll learn how to work with conditionals and then loops in Bash using the if, for, and while shell keywords. These allow us to execute commands conditionally and/or repeatedly, giving us control flow for our scripts.

We will cover:

  • How to use the if keyword
  • The use of and the difference between the [ builtin and the [[ keyword
  • When to use Bash's (( arithmetic compound command
  • How to match values with the case keyword
  • How shell script for loops work
  • Using Bash's alternative C-style for loops
  • Using while loops
  • The while read -r idiom for reading data line by line
  • Choosing between for and while

Shell script's syntax for these structures is somewhat unique, largely for historical reasons and to fit into its command-centered structure, and only partly resembles comparable features in other programming languages.