function kill_prev() {
    # $$ contains current pid (grep ignore so it doesn't suicide)
    local processes
    readarray -t processes < <(pgrep -f "$0" | grep -v "$$")
    kill "${processes[@]}" >/dev/null 2>&1
}

# Usage:
# Add this function to your background running script
# It will make sure that only one instance of your script is running at a time
kill_prev

system_resources () {
      echo "CPU Load: $(top -bn1 | grep "Cpu(s)" | awk '{print $2}')%"
      echo "Memory Used: $(free -m | awk 'NR==2{printf "%.2f%%", $3*100/$2}')"
      echo "Disk Used: $(df -h / | awk 'NR==2{print $5}')"
      echo "Active Users: $(who | wc -l)"
}

system_resources "$@"

# Usage:
chmod a+x system-resource-monitor.sh # First make it executable for all the users

./system-resource-monitor.sh  # It will print the following system resources (CPU, RAM, disk, and active users)