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)

Switching with the case keyword

Bash's extension to string equality tests for pattern matching is useful, but it can sometimes be more convenient to use the older POSIX-specified case construct, which is shell script's analogue of the C switch statement.

The case statement allows us to run commands based on the outcome of matching a string against glob patterns. For example, to check whether the command variable matches help, we might do this:

case $command in
    help) printf 'Command help:\n...' ;;

Note the following details of this syntax:

  • You don't have to double-quote $command just after the case statement.
  • The pattern to match has a closing ), but does not require an opening one.
  • The closing keyword is esac, which is case spelled backwards, just as the closing keyword for if is fi.
  • Each option is terminated with two semicolons.

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