#!/usr/bin/python

import time

iface='eth0'

def getdata():
	f = open("/proc/net/dev")
	for line in f.readlines():
		line = line.lstrip()
		if line.startswith(iface):
			r = line[len(iface)+1:].split()
			return long(r[0]),long(r[8])	

	raise ValueError("Could't find interface: %s" % iface)

lastin, lastout = getdata()
while 1:
	time.sleep(1)
	currin, currout = getdata()
	print "In: %d Out: %d" % (currin - lastin, currout - lastout)
	lastin, lastout = currin, currout