Pro Bash: Learn to Script and Program the GNU/Linux Shell

Table of Contents
About the Authors
About the Technical Reviewer
Acknowledgments
Chapter 1: Hello, World: Your First Shell Program
	What Is a Shell Script?
	The Hello World Code
	The Hello World Program File
	Naming the Script File
	Selecting a Directory for the Script
	Creating the File and Running the Script
	Choosing and Using a Text Editor
	Building a Better “Hello, World!”
	Summary
	Commands
	Concepts
	Variables
	Exercises
Chapter 2: Input, Output, and  Throughput
	Parameters and Variables
	Positional Parameters
	Special *@#0$?_!- Parameters
	Variables
	Arguments and Options
	Why You Should Avoid echo
	printf: Formatting and Printing Data
	Escape Sequences
	Format Specifiers
	Width Specification
	Printing to a Variable
	Line Continuation
	Standard Input/Output Streams and Redirection
	Redirection: >, >>, and <
	Reading Input
	Pipelines
	Command Substitution
	Summary
	Commands
	Concepts
	Exercises
Chapter 3: Looping and Branching
	Exit Status
	Testing an Expression
	test, a.k.a. [ … ]
	File Tests
	Integer Tests
	String Tests
	[[ … ]]: Evaluate an Expression
	Enhancements over Test
	(( …)): Evaluate an Arithmetic Expression
	Conditional Execution
	if
	Conditional Operators: && and ||
	case
	Looping
	while
	until
	for
	break
	continue
	Summary
	Commands
	Concepts
	Exercises
Chapter 4: Command-Line Parsing and Expansion
	Quoting
	Brace Expansion
	Tilde Expansion
	Parameter and Variable Expansion
	Arithmetic Expansion
	Command Substitution
	Word Splitting
	Pathname Expansion
	Process Substitution
	Parsing Options
	Summary
	Commands
	Exercises
Chapter 5: Parameters and Variables
	The Naming of Variables
	The Scope of a Variable: Can You See It from Here?
	Shell Variables
	Shell Variables
	Parameter Expansion
	Bourne Shell
	${var:-default} and ${var-default}: Use Default Values
	${var:+alternate} and ${var+alternate}: Use Alternate Values
	${var:=default} and ${var=default}: Assign Default Values
	${var:?message} and ${var?message}: Display Error Message If Empty or Unset
	POSIX Shell
	${#var}: Length of Variable’s Contents
	${var%PATTERN}: Remove the Shortest Match from the End
	${var%%PATTERN}: Remove the Longest Match from the End
	${var#PATTERN}: Remove the Shortest Match from the Beginning
	${var##PATTERN}: Remove the Longest Match from the Beginning
	bash
	${var//PATTERN/STRING}: Replace All Instances of PATTERN with STRING
	${var:OFFSET:LENGTH}: Return a Substring of $var
	${!var}: Indirect Reference
	bash-4.0
	${var^PATTERN}: Convert to Uppercase
	${var,PATTERN}: Convert to Lowercase
	Positional Parameters
	Arrays
	Integer-Indexed Arrays
	Displaying Arrays
	Assigning Array Elements
	Associative Arrays
	Summary
	Commands
	Concepts
	Exercises
Chapter 6: Shell Functions
	Definition Syntax
	Compound Commands
	Getting Results
	Set Different Exit Codes
	Print the Result
	Place Results in One or More Variables
	Function Libraries
	Using Functions from Libraries
	Sample Script
	Summary
	Commands
	Exercises
Chapter 7: String Manipulation
	Concatenation
	Repeat Character to a Given Length
	Processing Character by Character
	Reversal
	Case Conversion
	Comparing Contents Without Regard to Case
	Check for Valid Variable Name
	Insert One String into Another
	Examples
	Overlay
	Examples
	Trim Unwanted Characters
	Examples
	Index
	Summary
	Commands
	Functions
	Exercises
Chapter 8: File Operations and Commands
	Reading a File
	External Commands
	cat
	head
	touch
	ls
	cut
	wc
	Regular Expressions
	grep
	sed
	awk
	File Name Expansion Options
	nullglob
	failglob
	dotglob
	extglob
	?(pattern-list)
	*(pattern-list)
	@(pattern-list)
	+(pattern-list)
	!(pattern-list)
	nocaseglob
	globstar
	Summary
	Shell Options
	External Commands
	Exercises
Chapter 9: Reserved Words and Built-In Commands
	help, Display Information About Built-In Commands
	time, Print Time Taken for Execution of a Command
	read, Read a Line from an Input Stream
		-r, Read Backslashes Literally
		-e, Get Input with the readline Library
		-a, Read Words into an Array
		-d DELIM, Read Until DELIM Instead of a Newline
		-n NUM, Read a Maximum of NUM Characters
		-s, Do Not Echo Input Coming from a Terminal
		-p PROMPT:, Output PROMPT Without a Trailing Newline
		-t TIMEOUT, Only Wait TIMEOUT Seconds for Complete Input
		-u FD: Read from File Descriptor FD Instead of the Standard Input
		-i TEXT, Use TEXT As the Initial Text for Readline
		eval, Expand Arguments and Execute the Resulting Command
	Poor Man’s Arrays
		Setting Multiple Variables from One Command
		type, Display Information About Commands
		builtin, Execute a Built-In Command
		command, Execute a Command or Display Information About Commands
		pwd, Print the Current Working Directory
		unalias, Remove One or More Aliases
			Deprecated Built-Ins
			Dynamically Loadable Built-Ins
	Summary
		Commands and Reserved Words
		Deprecated Commands
	Exercise
Chapter 10: Writing Bug-Free Scripts and Debugging the Rest
	Prevention Is Better Than Cure
	Structure Your Programs
	Comments
	Initialization of Variables
	Function Definitions
	Runtime Configuration and Options
	Process Information
	Document Your Code
	Format Your Code Consistently
	The K.I.S.S. Principle
	Grouping Commands
	Test As You Go
	Debugging a Script
	Summary
	Exercises
Chapter 11: Programming for the Command Line
	Manipulating the Directory Stack
	cd
	pd
	cdm
	dirs Built-In Command
	menu
	Filesystem Functions
	l
	lsr
	cp, mv
	md
	Miscellaneous Functions
	pr1
	calc
	Managing Man Pages
	sman
	sus
	k
	Games
	The fifteen Puzzle
	Summary
	Exercises
Chapter 12: Runtime Configuration
	Defining Variables
	Command-Line Options and Arguments
	Menus
	Q&A Dialogue
	Configuration Files
	Scripts with Several Names
	Environment Variables
	All Together Now
	Script Information
	Default Configuration
	Screen Variables
	Function Definitions
	Function: die
	Function: menu
	The Upload Settings Menu
	Function: qa
	Function: print_config
	Function: readline
	Parse Command-Line Options
	Bits and Pieces
	Summary
	Exercises
Chapter 13: Data Processing
	Arrays
	Holes in an Indexed Array
	Using an Array for Sorting
	Insertion Sort Function
	Searching an Array
	Reading an Array into Memory
	Two-Dimensional Grids
	Working with Single-String Grids
	Function: initgrid
	Function: gridindex
	Function: putgrid
	Function: getgrid
	Function: showgrid
	Function: rshowgrid
	Two-Dimensional Grids Using Arrays
	Function: initagrid
	Function: putagrid
	Function: getagrid
	Function: showagrid
	Function: rshowagrid
	Data File Formats
	Line-Based Records
	Delimiter-Separated Values
	Fixed-Length Fields
	Block File Formats
	Summary
	Exercises
Chapter 14: Scripting the Screen
	Teletypewriter vs. Canvas
	Stretching the Canvas
	Control Sequence Introducer
	Priming the Canvas
	Moving the Cursor
	Changing Rendition Modes and Colors
	Placing a Block of Text on the Screen
	Scrolling Text
	Rolling Dice
	Summary
	Exercises
Chapter 15: Entry-Level Programming
	Single-Key Entry
	Function Library, key-funcs
	History in Scripts
	Sanity Checking
	Form Entry
	Reading the Mouse
	Summary
	Exercises
Appendix A: Shell Variables
Index