#!/bin/bash
# polling interval in sec
interval=5
interface="eth0"
rxByte=$(grep $interface /proc/net/dev| cut -d':' -f 2 | awk '{print $1}')
txByte=$(grep $interface /proc/net/dev| cut -d':' -f 2 | awk '{print $9}')
while true
do
    sleep $interval
    rxOld=$rxByte
    txOld=$txByte
#   echo old rx = $rxOld, tx = $txOld
    rxByte=$(grep $interface /proc/net/dev| cut -d':' -f 2 | awk '{print $1}')
    txByte=$(grep $interface /proc/net/dev| cut -d':' -f 2 | awk '{print $9}')
#   echo new rx = $rxByte, tx = $txByte
    rxbps=$(( $(( $((rxByte-rxOld))*8 ))/$interval))
    txbps=$(( $(( $((txByte-txOld))*8 ))/$interval))
    echo rx = $rxbps bps, tx = $txbps bps
done
exit