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)

Allowing scripts to run without user input

If your script requires user data during its run in order to make decisions on what to do, it can be tempting to prompt the user for each required bit of information when needed, perhaps using the -p option to the read builtin to request a prompt:

read -p 'Do you want to create the directory? [y/N]: ' createdir
case $createdir in
        mkdir -- "$HOME"/myscript || exit

This example will only create the directory named in the dir variable if a string such as y or YES (or yoyo!) is read from standard input, and assumes that it is likely to be the user's terminal.

This is convenient for interactive scripts, but it assumes that the user running the script is actually at a terminal, and it makes the script awkward to use in automation; someone trying to call this script automatically...