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)

Getting help with Bash

Sometimes in technical books, people skip the Getting help heading. Don't skip this one! It's very important, and will save you a lot of time and confusion.

You can get help on using most of the commands in this book with a two-step process. When you're using Bash, to get help on a command named printf, use help first:

bash$ help printf

You'll get some help output, so you now know that printf is a Bash keyword or builtin. That's the version of the command you want help with, because that's the one that you'll be using when you call it from within Bash.

To see why this is confusing, try the man manual reader command, instead:

bash$ man printf

You'll get a completely different document, a full manual page! The features aren't even the same! What's going on?

In a shell script, the same command can have more than one implementation. In Bash, you can see a list of all of them using the type command with its -a (all) switch:

bash$ type -a printf
printf is a shell builtin
printf is /usr/bin/printf

Notice how there are two results for printf: the first is a shell builtin a part of Bash itself and the second is a program on your filesystem. They will behave differently and have different documentation. We'll see more of the type command in later chapters.

So remember: always try help first! Some people use Bash for many years before learning it exists, and wonder why the man pages are always wrong. You can see a full list of available help topics by typing it on its own, with no arguments:

bash$ help