Bash — Functions

Basic function

#!/bin/bash

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

greet "Alice"  # Hello, Alice!

Return values

#!/bin/bash

add() {
    echo $(($1 + $2))
}

result=$(add 3 4)
echo "Sum: $result"  # 7

Return status

#!/bin/bash

is_even() {
    [ $(($1 % 2)) -eq 0 ]
}

if is_even 4; then
    echo "Even"
else
    echo "Odd"
fi

Local variables

#!/bin/bash

my_func() {
    local x=10
    echo "Inside: $x"
}

my_func
# echo $x  # Error: x is not defined

Function with return code

#!/bin/bash

check_file() {
    if [ -f "$1" ]; then
        return 0  # Success
    else
        return 1  # Failure
    fi
}

if check_file "test.txt"; then
    echo "File exists"
else
    echo "File not found"
fi

Mini Practice

Write Bash code that:

1. Creates a function that takes arguments
2. Returns a value via echo
3. Uses local variables
4. Returns success/failure status

Up Next

In the next lesson, you'll learn about Arguments — handling script arguments.