while getopts :a:b:c: options; do
case $options in
a) fival=$OPTARG ;;
b) secval=$OPTARG ;;
c) thival=$OPTARG ;;
?) echo "i dont know what $OPTARG is" ;;
esac
done
echo "A = $firval"
echo "B = $secval"
echo "C = $thival"