dd if=/dev/urandom of=$ref1 bs=1M count=$((RANDOM % 50 + 20))
dd if=/dev/urandom of=$ref2 bs=1M count=$((RANDOM % 50 + 20))
echo "ref file size: ref1($(stat -c %s $ref1))," \
dd if=/dev/urandom of=$ref1 bs=1M count=$((RANDOM % 50 + 20))
dd if=/dev/urandom of=$ref2 bs=1M count=$((RANDOM % 50 + 20))
echo "ref file size: ref1($(stat -c %s $ref1))," \