A comprehensive and deeply detailed Bash scripting cheatsheet covering all essential topics, categories, and examples.

Awesome-bash-scripting-cheatsheet.md

🐧 Ultimate Bash Scripting Cheatsheet

🚀 A comprehensive and deeply detailed Bash scripting cheatsheet covering all essential topics, categories, and examples.

Category	Command/Concept	Description	Syntax/Example
Basic Syntax	#!/bin/bash	Shebang to specify the interpreter to use for the script	#!/bin/bash
	Comments	Add comments to code	# This is a comment
	Variables	Declare variables (no spaces around =)	name="John"
	Printing	Print text to the console	echo "Hello, World!"
Data Types	Strings	Variables to store text	text="Hello"
	Integers	Variables to store numbers	num=42
	Arrays	Variables to store multiple values	arr=(apple banana cherry)
	Associative Arrays	Arrays with key-value pairs	declare -A arr; arr[fruit]="apple"
Operations	Arithmetic Operations	Perform basic math operations	echo $((3 + 5))
	String Operations	Concatenate or find string length	str="Hello"; echo "$str World"
	Array Operations	Access, add, or remove elements in arrays	arr[1]="banana"; unset arr[0]
Control Structures	If Statements	Conditional execution based on criteria	if [ "$a" -gt "$b" ]; then echo "a is greater"; fi
	Case Statements	Multi-way branching, similar to switch in other languages	case $var in 1) echo "One";; 2) echo "Two";; esac
	Loops	Repeat code execution	for i in {1..5}; do echo $i; done
	While Loops	Execute while a condition is true	while [ "$a" -lt 5 ]; do echo $a; ((a++)); done
File Operations	Reading Files	Read content of a file	cat filename.txt
	Writing to Files	Write output to a file	echo "Hello" > file.txt
	Appending to Files	Append content to a file	echo "Append" >> file.txt
	Check if File Exists	Check if a file or directory exists	if [ -f "file.txt" ]; then echo "Exists"; fi
	File Permissions	Change file permissions	chmod 755 file.txt
Input and Output	Input from User	Get user input	read -p "Enter name: " name
	Output Redirection	Redirect output to a file	ls > output.txt
	Append Output	Append output to a file	echo "Line" >> output.txt
	Error Redirection	Redirect errors	command 2> error.txt
Functions	Define Function	Define reusable function	function greet() { echo "Hello"; }
	Call Function	Execute a function	greet
	Parameters in Functions	Pass arguments to a function	function greet() { echo "Hello $1"; }; greet "John"
	Return Values	Return a value from a function	function add() { return $(( $1 + $2 )); }; add 3 4; echo $?
Special Variables	$?	Last command’s exit status	echo $?
	$#	Number of arguments passed	echo $#
	$@	All arguments as separate words	echo $@
	$*	All arguments as a single string	echo $*
	$0	Script name	echo $0
	$1, $2, ...	Positional parameters	echo $1
String Operations	String Length	Get length of a string	echo ${#string}
	Substring Extraction	Extract part of a string	echo ${string:2:5}
	String Replacement	Replace text within a string	echo ${string/foo/bar}
Array Operations	Array Length	Get the number of elements	echo ${#array[@]}
	Array Elements	Access all elements in an array	echo ${array[@]}
	Adding to Array	Append to an array	array+=(new_value)
Environment Variables	Define Variable	Set a variable for the current session	export MY_VAR="value"
	Access Environment Variable	Retrieve the value of a variable	echo $MY_VAR
	List Environment Variables	Display all environment variables	printenv
Process Management	Run in Background	Run a command in the background	command &
	Bring to Foreground	Bring background job to foreground	fg %1
	List Running Jobs	Show background jobs	jobs
	Kill Process	Terminate a running process	kill -9 PID
Error Handling	Exit Code	Set exit code in scripts	exit 1
	Trap Errors	Execute commands on script error	trap "echo Error occurred" ERR
	set -e	Exit script on any error	set -e
Debugging	set -x	Print commands as they are executed	set -x
	set +x	Disable debugging output	set +x
	Debug Specific Section	Enable debugging for specific code blocks	set -x; command; set +x
Command Substitution	Substitution	Use output of a command as part of another command	today=$(date)
	Backticks	Alternative way for substitution	`date`
Regular Expressions	Grep with Regex	Search text with patterns	grep -E "pattern" file.txt
	Sed for Text Replacement	Replace text in a file	sed 's/old/new/g' file.txt
Conditional Expressions	String Comparison	Compare strings	[ "$a" = "$b" ]
	Number Comparison	Compare numbers	[ "$a" -gt "$b" ]
	File Conditions	Check if a file exists, is readable, writable, or executable	[ -f "file.txt" ]
Advanced Scripting	Sourcing Files	Run another script in the current shell	source file.sh or . file.sh
	Here Document	Input block to a command	`cat <<EOF
Hello
EOF`
	Here Strings	Pass string to a command	cat <<< "Hello"
Job Control	Background and Foreground	Manage background jobs	command &
	Job Control Commands	jobs, fg, bg for job management	jobs, fg %1, bg %2
	disown	Remove job from job table	disown %1
Shell Options	set Command	Configure shell behavior	set -e, set -u, set -x
	shopt Command	Additional shell options	shopt -s nocaseglob
Networking Commands	ping	Check network connection	ping google.com
	curl	Retrieve data from URLs	curl http://example.com
	wget	Download files from the web	wget http://example.com/file
	netstat	Network connections and ports	netstat -tuln
Date and Time	date	Display or set date and time	date "+%Y-%m-%d"
	sleep	Pause for a specified time	sleep 5
	timeout	Run a command with a time limit	timeout 10 command
Archive and Compression	tar	Archive files	tar -czvf archive.tar.gz dir/
	gzip	Compress files	gzip file
	unzip	Decompress files	unzip file.zip

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