Bash Quick Start Guide by Ryder, Tom -- Read -- Imperial Library of Trantor

Index

Title Page Copyright and Credits

Bash Quick Start Guide

Dedication Packt Upsell

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Contributors

About the author About the reviewers Packt is searching for authors like you

Preface

Who this book is for What this book covers To get the most out of this book

Download the example code files Download the color images Conventions used

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Reviews

What is Bash?

What Bash is and is not Getting Bash Checking Bash is running

Switching the login shell to Bash

Identifying the Bash version number Upgrading Bash on macOS X Understanding Bash features

POSIX shell script features Bash-specific features Do I need Bash?

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

Escaping Single quotes Double quotes Quote concatenation

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

The type command The echo command The printf command The pwd command

Tilde paths

The cd command

Changing the directory in scripts

The set command The declare command The test, [, and [[ commands

Essential system commands

The ls command

Getting filename lists without ls

The mv command The cp command The rm and rmdir commands The grep command The cut command The wc command

Getting file sizes with wc or du

The find command

Executing commands for each result A note about find and xargs

The sort and uniq commands

Summary

Input, Output, and Redirection

Redirecting output

Redirection paths Avoiding overwrites Appending to files Understanding created file permissions Choosing permissions for created files

Redirecting errors

Combining errors with output Blocking errors completely Sending output to more than one place

Redirecting input

Using a long string as input with here-documents

Using pipes

Adding file contents to a stream Piping output from multiple programs Filtering programs

The sed stream editor The AWK programming language

Summary

Variables and Patterns

Using variables

Listing variables Naming variables

Variable name case

Clearing variables Environment variables

Calling programs with environment variables

Expanding variables Reading a value into a variable Getting command output in variables Parameter expansion forms

Specifying default values String chopping Extracting substrings Getting string length Substituting strings Changing case Combining parameter expansion forms

Doing math in Bash

Fixed or floating-point arithmetic

Using globs

Configuring globbing behavior

Including dot files, but excluding dot and dot-dot Expanding to nothing Case-insensitive globbing Extended globbing

Using arrays

Glob expansion in arrays Associative arrays

Summary

Loops and Conditionals

Using the if keyword

Using the test command Using the [ command Using the [[ keyword Arithmetic conditions

Switching with the case keyword Looping over shell words with for

Skipping an iteration Ending the loop Misuse of for loops

Using Bash's C-style for loops Using while loops

Infinite loops Reading data line by line Field splitting Saving fields into arrays Choosing the splitting character Disabling whitespace trimming Reading process output

Avoiding subshell problems

Avoiding input problems with ssh

Summary

Scripts, Functions, and Aliases

Aliases

Defining new aliases Understanding shortcomings with aliases

Functions

Defining functions Passing arguments to functions

Using -- to separate options from filenames Getting all the arguments

Returning values from functions Understanding function input and output Function scope Reloading functions at shell startup

Scripts

Scripting methods Writing a shebang script Finding scripts with $PATH System bindir User bindir Arguments to scripts Understanding sh vs bash Using env

Choosing between functions and scripts Using functions in scripts Summary

Best Practices

Quoting correctly

When you don't want quotes

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

Writing comments Providing help output Writing manual pages

Using temporary files cleanly Cleaning up after a script Tools to check shell scripts for problems Summary

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