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🐚 Bash Basics & Shell Scripting Cheat Sheet

This document summarizes essential Linux shell commands and Bash scripting syntax for beginners and intermediate users.

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🔧 Basic Linux Commands

Command	Description
ls	List files and directories
ls -a	Include hidden files (shows hidden . files)
ls -l	Long listing with permissions, owner, size, and date
ll	Lists files in long format (alias to ls -l)
pwd	Print working directory
cd [dir]	Change directory
mkdir [dir]	Create new directory
rmdir [dir]	Remove an empty directory
rm [file]	Remove file
rm -r [dir]	Remove directory recursively
cp source dest	Copy file
mv old new	Move or rename file
touch [file]	Create empty file or update timestamp
cat [file]	View file contents
head [file]	Show first 10 lines
tail [file]	Show last 10 lines
less [file]	View file with scroll
echo "text"	Print text to terminal
echo $VAR	Print value of a variable
clear	Clear terminal screen
history	Show command history
man [command]	Manual page for command
env	List all environment variables
export VAR=value	Set environment variable
whoami	Display current user
uname -a	Show system information
df -h	Show disk usage (human-readable)
du -sh [dir]	Show size of a directory
ps aux	List running processes
kill [pid]	Terminate process
grep "text" [file]	Search for text pattern
find /path -name "file"	Find files by name
chmod 755 file	Change permissions
chown user:group file	Change owner and group
sudo [command]	Run command as superuser
top	Show running processes interactively
ping [host]	Test network connectivity
curl [url]	Fetch data from URL
wget [url]	Download file from URL
tar -xvf file.tar	Extract .tar file
tar -czvf file.tar.gz folder	Compress folder into .tar.gz
zip -r file.zip folder	Compress folder into .zip
unzip file.zip	Extract .zip file
date	Display system date and time
cal	Show calendar
uptime	Show system uptime
exit	Close terminal session

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💡 Bash Scripting Basics

Variables

name="John"
echo "Hello $name"

Input & Output

echo "Enter your name:"
read name
echo "Welcome, $name!"

Arithmetic Operations

a=5
b=3
echo $((a + b))
echo $((a - b))
echo $((a * b))
echo $((a / b))

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Loops

For Loop

for var in ${array[@]}
do
    echo "Processing $var"
done

Example:

for i in {1..5}
do
    echo "Number: $i"
done

While Loop

count=1
while [ $count -le 5 ]
do
    echo "Count: $count"
    ((count++))
done

Until Loop

count=1
until [ $count -gt 5 ]
do
    echo "Count: $count"
    ((count++))
done

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Conditional Statements

Simple if

if [ $a -eq $b ]
then
    echo "Equal"
fi

if-else

if [ $a -eq $b ]
then
    echo "Equal"
else
    echo "Not equal"
fi

if-elif-else

if [ $a -eq $b ]
then
    echo "Equal"
elif [ $a -gt $b ]
then
    echo "a is greater"
else
    echo "b is greater"
fi

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Functions

greet() {
    echo "Hello, $1!"
}

greet "World"

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Example Script

#!/bin/bash
echo "Enter your name:"
read name

if [ -z "$name" ]; then
    echo "No name entered!"
else
    echo "Hello, $name!"
fi

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Useful Tips

• Add #!/bin/bash at the top of scripts.
• Make script executable: chmod +x script.sh
• Run script: ./script.sh

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Author: Shimanto Purpose: Quick Bash Reference Sheet Last Updated: 2025

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