Learn BASH with Real Code Examples

count=0
isDark=0

updateUI() {
    echo "Counter: $count"
    echo "Theme: $( [ $isDark -eq 1 ] && echo 'Dark' || echo 'Light' )"
}

increment() { count=$((count + 1)); updateUI; }
decrement() { count=$((count - 1)); updateUI; }
reset() { count=0; updateUI; }
toggleTheme() { isDark=$((1 - isDark)); updateUI; }

# Simulate actions
updateUI
increment
increment
toggleTheme
decrement
reset

Demonstrates a simple counter with theme toggling using Bash variables and console output.

add() { echo $(( $1 + $2 )); }
subtract() { echo $(( $1 - $2 )); }
multiply() { echo $(( $1 * $2 )); }
divide() { echo $(( $1 / $2 )); }

echo "Add 5 + 3: $(add 5 3)"
echo "Subtract 5 - 3: $(subtract 5 3)"
echo "Multiply 5 * 3: $(multiply 5 3)"
echo "Divide 6 / 2: $(divide 6 2)"

Performs basic arithmetic operations using functions.

factorial() {
    if [ $1 -le 1 ]; then
        echo 1
    else
        echo $(( $1 * $(factorial $(( $1 - 1 ))) ))
    fi
}

echo "Factorial of 5: $(factorial 5)"

Recursive factorial calculation.

fibonacci() {
    if [ $1 -eq 0 ]; then
        echo 0
    elif [ $1 -eq 1 ]; then
        echo 1
    else
        echo $(( $(fibonacci $(( $1 - 1 ))) + $(fibonacci $(( $1 - 2 ))) ))
    fi
}

for i in {0..9}; do
    echo $(fibonacci $i)
done

Generate Fibonacci numbers using recursion.

numbers=(1 2 3 4 5 6 7 8 9 10)
squares=()
for n in "${numbers[@]}"; do
    if [ $((n % 2)) -eq 0 ]; then
        squares+=( $((n * n)) )
    fi
done
    echo "${squares[@]}"

Create array of squares for even numbers.

str="HelloWorld"
sub=${str:0:5}
len=${#str}
echo "Substring: $sub, Length: $len"

Demonstrates substring extraction and length.

for i in {1..10}; do
    if [ $((i % 2)) -eq 0 ]; then
        echo "$i is even"
    fi
done

Loop through numbers and print even ones.

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

greet Alice
greet Bob

Pass arguments to functions and print results.

numbers=(1 2 3 4 5)
sum=0
for n in "${numbers[@]}"; do
    sum=$((sum + n))
done
    echo $sum

Sum elements of an array using a loop.

arr1=(1 2 3)
arr2=(4 5 6)
for i in ${!arr1[@]}; do
    echo "$((arr1[i] + arr2[i]))"
done

Combine two arrays element-wise using a loop.