Python script to implement network card traffic monitoring

#/usr/bin/env/python
#coding=utf-8

import sys,re,time,os
maxdata = 50000 # unit KB
memfilename = '/tmp/newnetcardtransdata.txt'
netcard = '/proc/net/dev'

def checkfile(filename):
  if os.path.isfile(filename):
    pass
  else:
    f = open(filename, 'w')
    f.write('0')
    f.close()

def get_net_data():
  nc = netcard or '/proc/net/dev'
  fd = open(nc, "r")
  netcardstatus = False
  for line in fd.readlines():
    if line.find("eth0") > 0:
      netcardstatus = True
      field = line.split()
      recv = field[0].split(":")[1]
      recv = recv or field[1]
      send = field[8]
  if not netcardstatus:
    fd.close()
    print 'Please setup your netcard'
    sys.exit()
  fd.close()
  return (float(recv), float(send))

def monfirst(filename):
  nowtime = time.strftime('%m-%d %H:%M',time.localtime(time.time()))
  sec = time.localtime().tm_sec
  if nowtime == '01-01 00:00':
    if sec < 10:
      f = open(filename, 'w')
      f.write('0')
      f.close()      

def net_loop():
  (recv, send) = get_net_data()
  checkfile(memfilename)
  monfirst(memfilename)
  lasttransdaraopen = open(memfilename,'r')
  lasttransdata = lasttransdaraopen.readline()
  lasttransdaraopen.close()
  totaltrans = int(lasttransdata) or 0
  while True:
    time.sleep(3)
    (new_recv, new_send) = get_net_data()
    recvdata = (new_recv - recv) / 1024
    senddata = (new_send - send) / 1024
    totaltrans += int(recvdata)
    totaltrans += int(senddata)
    memw = open(memfilename,'w')
    memw.write(str(totaltrans))
    memw.close()
    if totaltrans >= maxdata:
      os.system('init 0')

if __name__ == "__main__":
  net_loop()

Running as ROOT, maxdata is the maximum traffic limit and if you exceed this limit, the system will automatically shut down. Of course, you can change os.system('init 0') to the command you want