Basic Bash Examples

Updated

October 31, 2026

Basic Bash Examples

This section contains fundamental Bash scripting examples to help you practice and understand core concepts.

Hello World Variations

Simple Hello World

#!/bin/bash
echo "Hello, World!"

Hello World with Variables

#!/bin/bash
name="World"
echo "Hello, $name!"

Interactive Hello World

#!/bin/bash
echo "What's your name?"
read name
echo "Hello, $name! Nice to meet you."

Hello World with Date

#!/bin/bash
echo "Hello, World!"
echo "Today is: $(date)"
echo "Current user: $(whoami)"

Variable Examples

Basic Variable Operations

#!/bin/bash
# Variable assignment
first_name="John"
last_name="Doe"
age=25

# Variable usage
echo "Name: $first_name $last_name"
echo "Age: $age"

# Variable concatenation
full_name="$first_name $last_name"
echo "Full name: $full_name"

Environment Variables

#!/bin/bash
echo "Your home directory: $HOME"
echo "Your username: $USER"
echo "Your shell: $SHELL"
echo "Current path: $PATH"

Variable Default Values

#!/bin/bash
# Set default values
database_host=${DB_HOST:-"localhost"}
database_port=${DB_PORT:-"5432"}
database_name=${DB_NAME:-"myapp"}

echo "Database configuration:"
echo "Host: $database_host"
echo "Port: $database_port"
echo "Database: $database_name"

Variable Length and Manipulation

#!/bin/bash
text="Hello World"

echo "Original text: $text"
echo "Length: ${#text}"
echo "Uppercase: ${text^^}"
echo "Lowercase: ${text,,}"
echo "First 5 characters: ${text:0:5}"
echo "Last 5 characters: ${text: -5}"

Command Line Arguments

Basic Argument Handling

#!/bin/bash
echo "Script name: $0"
echo "First argument: $1"
echo "Second argument: $2"
echo "All arguments: $@"
echo "Number of arguments: $#"

Argument Validation

#!/bin/bash
if [ $# -eq 0 ]; then
    echo "Usage: $0 <name> [age]"
    exit 1
fi

name="$1"
age="${2:-unknown}"

echo "Name: $name"
echo "Age: $age"

Processing Multiple Arguments

#!/bin/bash
echo "Processing all arguments:"
for arg in "$@"; do
    echo "Argument: $arg"
done

Simple Calculations

Basic Arithmetic

#!/bin/bash
a=10
b=5

echo "a = $a, b = $b"
echo "Addition: $((a + b))"
echo "Subtraction: $((a - b))"
echo "Multiplication: $((a * b))"
echo "Division: $((a / b))"
echo "Modulo: $((a % b))"

Calculator Script

#!/bin/bash
echo "Simple Calculator"
read -p "Enter first number: " num1
read -p "Enter operator (+, -, *, /): " op
read -p "Enter second number: " num2

case $op in
    +) result=$((num1 + num2)) ;;
    -) result=$((num1 - num2)) ;;
    \*) result=$((num1 * num2)) ;;
    /)
        if [ $num2 -eq 0 ]; then
            echo "Error: Division by zero"
            exit 1
        fi
        result=$((num1 / num2))
        ;;
    *) echo "Invalid operator"; exit 1 ;;
esac

echo "Result: $num1 $op $num2 = $result"

Temperature Converter

#!/bin/bash
echo "Temperature Converter"
echo "1. Celsius to Fahrenheit"
echo "2. Fahrenheit to Celsius"
read -p "Choose option (1 or 2): " choice

case $choice in
    1)
        read -p "Enter temperature in Celsius: " celsius
        fahrenheit=$(echo "scale=2; $celsius * 9/5 + 32" | bc)
        echo "$celsius°C = $fahrenheit°F"
        ;;
    2)
        read -p "Enter temperature in Fahrenheit: " fahrenheit
        celsius=$(echo "scale=2; ($fahrenheit - 32) * 5/9" | bc)
        echo "$fahrenheit°F = $celsius°C"
        ;;
    *)
        echo "Invalid choice"
        exit 1
        ;;
esac

File Operations

File Information

#!/bin/bash
filename="$1"

if [ -z "$filename" ]; then
    echo "Usage: $0 <filename>"
    exit 1
fi

if [ -f "$filename" ]; then
    echo "File: $filename"
    echo "Size: $(stat -c%s "$filename") bytes"
    echo "Last modified: $(stat -c%y "$filename")"
    echo "Permissions: $(stat -c%A "$filename")"
    echo "Owner: $(stat -c%U "$filename")"
    echo "Group: $(stat -c%G "$filename")"
else
    echo "File '$filename' does not exist"
fi

File Backup

#!/bin/bash
source_file="$1"

if [ -z "$source_file" ]; then
    echo "Usage: $0 <source_file>"
    exit 1
fi

if [ ! -f "$source_file" ]; then
    echo "Error: File '$source_file' does not exist"
    exit 1
fi

backup_file="${source_file}.backup.$(date +%Y%m%d_%H%M%S)"

if cp "$source_file" "$backup_file"; then
    echo "Backup created: $backup_file"
else
    echo "Error: Failed to create backup"
    exit 1
fi

Directory Listing

#!/bin/bash
directory="${1:-.}"

echo "Contents of directory: $directory"
echo "=================================="

if [ -d "$directory" ]; then
    for item in "$directory"/*; do
        if [ -f "$item" ]; then
            echo "FILE: $(basename "$item")"
        elif [ -d "$item" ]; then
            echo "DIR:  $(basename "$item")"
        fi
    done
else
    echo "Error: '$directory' is not a directory"
fi

Text Processing

Word Count

#!/bin/bash
filename="$1"

if [ -z "$filename" ]; then
    echo "Usage: $0 <filename>"
    exit 1
fi

if [ -f "$filename" ]; then
    lines=$(wc -l < "$filename")
    words=$(wc -w < "$filename")
    chars=$(wc -c < "$filename")

    echo "File: $filename"
    echo "Lines: $lines"
    echo "Words: $words"
    echo "Characters: $chars"
else
    echo "File '$filename' does not exist"
fi

Text Search

#!/bin/bash
if [ $# -ne 2 ]; then
    echo "Usage: $0 <search_term> <filename>"
    exit 1
fi

search_term="$1"
filename="$2"

if [ ! -f "$filename" ]; then
    echo "File '$filename' does not exist"
    exit 1
fi

echo "Searching for '$search_term' in '$filename':"
grep -n "$search_term" "$filename"

count=$(grep -c "$search_term" "$filename")
echo "Found $count occurrences"

Line Numbering

#!/bin/bash
filename="$1"

if [ -z "$filename" ]; then
    echo "Usage: $0 <filename>"
    exit 1
fi

if [ -f "$filename" ]; then
    line_number=1
    while IFS= read -r line; do
        printf "%3d: %s\n" $line_number "$line"
        ((line_number++))
    done < "$filename"
else
    echo "File '$filename' does not exist"
fi

System Information

System Status

#!/bin/bash
echo "=== System Information ==="
echo "Hostname: $(hostname)"
echo "Uptime: $(uptime -p)"
echo "Current user: $(whoami)"
echo "Current directory: $(pwd)"
echo "Date: $(date)"
echo

echo "=== Memory Usage ==="
free -h

echo
echo "=== Disk Usage ==="
df -h

echo
echo "=== CPU Information ==="
lscpu | grep "Model name"

Process Monitor

#!/bin/bash
echo "Top 10 processes by CPU usage:"
ps aux --sort=-%cpu | head -11

echo
echo "Top 10 processes by memory usage:"
ps aux --sort=-%mem | head -11

Network Information

#!/bin/bash
echo "=== Network Information ==="
echo "Hostname: $(hostname)"
echo "Domain: $(hostname -d 2>/dev/null || echo "Not set")"

echo
echo "=== Network Interfaces ==="
ip addr show | grep -E "^[0-9]+:|inet "

echo
echo "=== Routing Table ==="
ip route show

User Input Examples

Menu System

#!/bin/bash
while true; do
    echo
    echo "=== Main Menu ==="
    echo "1. Show date and time"
    echo "2. Show current directory"
    echo "3. List files"
    echo "4. Show disk usage"
    echo "5. Exit"
    echo
    read -p "Choose an option (1-5): " choice

    case $choice in
        1) date ;;
        2) pwd ;;
        3) ls -la ;;
        4) df -h ;;
        5) echo "Goodbye!"; exit 0 ;;
        *) echo "Invalid choice. Please try again." ;;
    esac

    read -p "Press Enter to continue..."
done

User Registration

#!/bin/bash
echo "User Registration Form"
echo "====================="

read -p "First Name: " first_name
read -p "Last Name: " last_name
read -p "Email: " email
read -p "Age: " age
read -s -p "Password: " password
echo

echo
echo "Registration Summary:"
echo "Name: $first_name $last_name"
echo "Email: $email"
echo "Age: $age"
echo "Password: [hidden]"

read -p "Is this information correct? (y/n): " confirm
if [ "$confirm" = "y" ] || [ "$confirm" = "Y" ]; then
    echo "Registration completed!"
else
    echo "Registration cancelled."
fi

Quiz Game

#!/bin/bash
score=0
total_questions=3

echo "Welcome to the Bash Quiz!"
echo "========================"

# Question 1
echo "Question 1: What command shows the current directory?"
echo "a) pwd"
echo "b) cd"
echo "c) ls"
read -p "Your answer: " answer1

if [ "$answer1" = "a" ] || [ "$answer1" = "A" ]; then
    echo "Correct!"
    ((score++))
else
    echo "Wrong! The correct answer is 'a) pwd'"
fi

# Question 2
echo
echo "Question 2: What symbol is used for comments in bash?"
echo "a) //"
echo "b) #"
echo "c) /*"
read -p "Your answer: " answer2

if [ "$answer2" = "b" ] || [ "$answer2" = "B" ]; then
    echo "Correct!"
    ((score++))
else
    echo "Wrong! The correct answer is 'b) #'"
fi

# Question 3
echo
echo "Question 3: What command lists files and directories?"
echo "a) list"
echo "b) dir"
echo "c) ls"
read -p "Your answer: " answer3

if [ "$answer3" = "c" ] || [ "$answer3" = "C" ]; then
    echo "Correct!"
    ((score++))
else
    echo "Wrong! The correct answer is 'c) ls'"
fi

echo
echo "Quiz completed!"
echo "Your score: $score out of $total_questions"

percentage=$((score * 100 / total_questions))
if [ $percentage -ge 80 ]; then
    echo "Excellent work!"
elif [ $percentage -ge 60 ]; then
    echo "Good job!"
else
    echo "Keep practicing!"
fi

String Manipulation

String Operations

#!/bin/bash
text="Hello World Programming"

echo "Original: $text"
echo "Length: ${#text}"
echo "Uppercase: ${text^^}"
echo "Lowercase: ${text,,}"
echo "First word: ${text%% *}"
echo "Last word: ${text##* }"
echo "Remove 'Hello': ${text/Hello/}"
echo "Replace 'World' with 'Bash': ${text/World/Bash}"
echo "First 10 chars: ${text:0:10}"
echo "From position 6: ${text:6}"

Palindrome Checker

#!/bin/bash
read -p "Enter a word to check if it's a palindrome: " word

# Convert to lowercase and remove spaces
clean_word=$(echo "$word" | tr '[:upper:]' '[:lower:]' | tr -d ' ')

# Reverse the string
reversed=$(echo "$clean_word" | rev)

if [ "$clean_word" = "$reversed" ]; then
    echo "'$word' is a palindrome!"
else
    echo "'$word' is not a palindrome."
fi

Password Generator

#!/bin/bash
read -p "Enter password length (default 12): " length
length=${length:-12}

# Generate password using /dev/urandom
password=$(tr -dc 'A-Za-z0-9!@#$%^&*' < /dev/urandom | head -c "$length")

echo "Generated password: $password"
echo "Password strength:"
echo "Length: $length characters"

# Check password strength
if [[ $password =~ [A-Z] ]]; then
    echo "✓ Contains uppercase letters"
fi

if [[ $password =~ [a-z] ]]; then
    echo "✓ Contains lowercase letters"
fi

if [[ $password =~ [0-9] ]]; then
    echo "✓ Contains numbers"
fi

if [[ $password =~ [!@#\$%\^&\*] ]]; then
    echo "✓ Contains special characters"
fi

Array Examples

Basic Array Operations

#!/bin/bash
# Create array
fruits=("apple" "banana" "orange" "grape")

echo "All fruits: ${fruits[@]}"
echo "Number of fruits: ${#fruits[@]}"
echo "First fruit: ${fruits[0]}"
echo "Last fruit: ${fruits[-1]}"

# Add element
fruits+=("mango")
echo "After adding mango: ${fruits[@]}"

# Loop through array
echo "Fruits list:"
for i in "${!fruits[@]}"; do
    echo "$((i+1)). ${fruits[i]}"
done

Shopping List

#!/bin/bash
declare -a shopping_list

echo "Shopping List Manager"
echo "===================="

while true; do
    echo
    echo "1. Add item"
    echo "2. Remove item"
    echo "3. Show list"
    echo "4. Clear list"
    echo "5. Exit"
    read -p "Choose option: " choice

    case $choice in
        1)
            read -p "Enter item to add: " item
            shopping_list+=("$item")
            echo "Added '$item' to the list"
            ;;
        2)
            if [ ${#shopping_list[@]} -eq 0 ]; then
                echo "List is empty"
            else
                echo "Current items:"
                for i in "${!shopping_list[@]}"; do
                    echo "$((i+1)). ${shopping_list[i]}"
                done
                read -p "Enter item number to remove: " num
                if [ "$num" -ge 1 ] && [ "$num" -le ${#shopping_list[@]} ]; then
                    removed_item="${shopping_list[$((num-1))]}"
                    unset shopping_list[$((num-1))]
                    shopping_list=("${shopping_list[@]}")  # Re-index array
                    echo "Removed '$removed_item'"
                else
                    echo "Invalid item number"
                fi
            fi
            ;;
        3)
            if [ ${#shopping_list[@]} -eq 0 ]; then
                echo "Shopping list is empty"
            else
                echo "Shopping List:"
                for i in "${!shopping_list[@]}"; do
                    echo "$((i+1)). ${shopping_list[i]}"
                done
            fi
            ;;
        4)
            shopping_list=()
            echo "List cleared"
            ;;
        5)
            echo "Goodbye!"
            exit 0
            ;;
        *)
            echo "Invalid choice"
            ;;
    esac
done

Grade Calculator

#!/bin/bash
declare -a grades
declare -a subjects

echo "Grade Calculator"
echo "==============="

read -p "How many subjects? " num_subjects

for ((i=1; i<=num_subjects; i++)); do
    read -p "Enter subject $i name: " subject
    read -p "Enter grade for $subject: " grade

    subjects+=("$subject")
    grades+=("$grade")
done

# Calculate average
total=0
for grade in "${grades[@]}"; do
    total=$((total + grade))
done

average=$((total / num_subjects))

echo
echo "Grade Report:"
echo "============"
for i in "${!subjects[@]}"; do
    echo "${subjects[i]}: ${grades[i]}"
done

echo
echo "Average: $average"

if [ $average -ge 90 ]; then
    echo "Grade: A (Excellent)"
elif [ $average -ge 80 ]; then
    echo "Grade: B (Good)"
elif [ $average -ge 70 ]; then
    echo "Grade: C (Average)"
elif [ $average -ge 60 ]; then
    echo "Grade: D (Below Average)"
else
    echo "Grade: F (Fail)"
fi