lua 如何实现获取当前网速?

local network = {}

network.speed = wibox.widget.textbox()
network.icon = wibox.widget.imagebox()

if river or serenity then

network.icon:set_image("/usr/share/icons/oxygen/22x22/devices/network-wired.png")
vicious.register(network.speed, vicious.widgets.net, '${eth0 down_kb}↓ ${eth0 up_kb}↑', 5)

elseif ice9 then

network.wifi = wibox.widget.textbox()
network.iface = ''

vicious.register(network.wifi, vicious.widgets.wifi,

function (widget, args)
  local p = args["{linp}"]
  local n

  if p > 75 then
    n = '100'
  elseif p > 50 then
    n = '75'
  elseif p > 25 then
    n = '50'
  elseif p > 0 then
    n = '25'
  else
    n = '00'
  end

  network.icon:set_image("/usr/share/icons/oxygen/22x22/devices/network-wireless-connected-"..n..".png")

  return '<span color ="'..gradient(0, 100, 100-p)..'">'..p..'</span> : '
end, 23, 'wlan0')

function network.update()

local iface
local ethup = false
local operstate = io.open('/sys/class/net/eth0/operstate', 'r')

if operstate then
  if operstate:read() == 'up' then
    ethup = true
  end
  io.close(operstate)
end

if ethup then 
  iface = 'eth0'
  if iface ~= network.iface then
    vicious.unregister(network.wifi, true)
    network.wifi:set_text('')
    network.icon:set_image("/usr/share/icons/oxygen/22x22/devices/network-wired.png")
    vicious.unregister(network.speed, false)
    vicious.register(network.speed, vicious.widgets.net, '${'..iface..' down_kb}↓ ${'..iface..' up_kb}↑', 5)
  end
else
  iface = 'wlan0'
  if iface ~= network.iface then
    vicious.unregister(network.speed, false)
    vicious.register(network.speed, vicious.widgets.net, '${'..iface..' down_kb}↓ ${'..iface..' up_kb}↑', 5)
    vicious.activate(network.wifi)
  end
end

network.iface = iface

end

end

return network