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Bash Quick Start Guide

By : Tom Ryder

5 (2)

Buy this Book

Bash Quick Start Guide

5 (2)

By: Tom Ryder

Buy this Book

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.

Preface

Who this book is for

What this book covers

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Free Chapter

What is Bash?

What Bash is and is not

Getting Bash

Checking Bash is running

Identifying the Bash version number

Upgrading Bash on macOS X

Understanding Bash features

Choosing when to apply Bash

Choosing when to avoid Bash

Getting help with Bash

Summary

Bash Command Structure

Using Bash interactively

Interactive key bindings

Simple commands

Shell metacharacters

Quoting

Running commands in sequence

Exit values

Stopping a command list on error

Running a command in the background

Summary

Essential Commands

Distinguishing command types

Essential Bash builtin commands

Essential system commands

Summary

Input, Output, and Redirection

Redirecting output

Redirecting errors

Redirecting input

Using pipes

Summary

Variables and Patterns

Using variables

Using globs

Using arrays

Summary

Loops and Conditionals

Using the if keyword

Switching with the case keyword

Looping over shell words with for

Using Bash's C-style for loops

Using while loops

Summary

Scripts, Functions, and Aliases

Aliases

Functions

Scripts

Choosing between functions and scripts

Using functions in scripts

Summary

Best Practices

Quoting correctly

Handling filenames starting with dashes

Separating output and diagnostics

Keeping scripts brief and simple

Keeping scripts flexible

Respecting and applying the user's configuration

Allowing scripts to run without user input

Limiting the scope of shell state changes

Avoiding path anti-patterns

Avoiding Bash for untrusted user input

Documenting scripts

Using temporary files cleanly

Cleaning up after a script

Tools to check shell scripts for problems

Summary

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Quoting

The way you can reliably include characters that are special to Bash literally in a command line is to quote them. Quoting special characters makes Bash ignore any special meaning they may otherwise have to the shell, and instead use them as plain characters, like a-z or 0-9. This works for almost any special character.

We say "almost", because there's one exception: there's no way to escape the null character (ASCII NUL, 0x00) in a shell word.

Quoting is the most important thing that even experienced people who write shell script sometimes get wrong. Even a lot of very popular documentation online fails to quote correctly in example scripts! If you learn to quote correctly, you will save yourself a lot of trouble down the line. The way quoting in shell script works very often surprises people coming from other programming languages.

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