if=eth0;
grep $if /proc/net/dev>l;
i=`awk '{print substr($1,6)}' l`;
o=`awk '{print $9}' l`;
sleep 5;
grep $if /proc/net/dev>l;
echo "RX $(((`awk '{print substr($1,6)}' l`-$i)/1024)) KB/s"
echo "TX $(((`awk '{print $9}' l`-$o)/1024)) KB/s"
rm l