https://stackoverflow.com/questions/6482377/check-existence-of-input-argument-in-a-bash-shell-script

bash-argument-exists.sh

# variable $# is the number of input arguments
if [ $# -eq 0 ]
  then
    echo "No arguments supplied"
fi

# check if an argument is an empty string or not
if [ -z "$1" ]
  then
    echo "No argument supplied"
fi