#!/bin/bash
dev="eth0"
rx_bytes=$(</sys/class/net/$dev/statistics/rx_bytes)
tx_bytes=$(</sys/class/net/$dev/statistics/tx_bytes)
while [ true ]
do
sleep 1
rx_bytes_n=$(</sys/class/net/$dev/statistics/rx_bytes)
tx_bytes_n=$(</sys/class/net/$dev/statistics/tx_bytes)
rx_rate=$((($rx_bytes_n - $rx_bytes)*8/1000))
tx_rate=$((($tx_bytes_n - $tx_bytes)*8/1000))
rx_bytes=$rx_bytes_n
tx_bytes=$tx_bytes_n
echo "RX: $rx_rate Kbps TX: $tx_rate Kbps"
done