if test $# -eq 0
  then
    echo "You must supply at least one argument."
    exit 1
fi

echo "$1"  #first argument, 1=one

if test -f "$1"  #-f option for test: exists and is an ordinary file (not a directory), $1 means first command line argument
  then
    echo "$l is an ordinary file in the working directory" 	
  else
    echo "$l is NOT an ordinary file in the working directory"
fi