#!/bin/bash
# validate_ipv4.sh - Check if a string is a valid IPv4 address
# Usage: validate_ipv4.sh <IP_ADDRESS>
# Returns: 0 if valid, 1 if invalid
# Output: "valid" or "invalid"

validate_ipv4() {
    local ip="$1"
    local regex='^([0-9]{1,3})\.([0-9]{1,3})\.([0-9]{1,3})\.([0-9]{1,3})$'
    
    if [[ ! $ip =~ $regex ]]; then
        echo "invalid"
        return 1
    fi
    
    for i in "${BASH_REMATCH[1]}" "${BASH_REMATCH[2]}" "${BASH_REMATCH[3]}" "${BASH_REMATCH[4]}"; do
        if (( i > 255 )); then
            echo "invalid"
            return 1
        fi
    done
    
    echo "valid"
    return 0
}

# Main execution
if [[ $# -ne 1 ]]; then
    echo "Usage: $0 <IP_ADDRESS>" >&2
    exit 2
fi

validate_ipv4 "$1"