local cur, old = {}, {}

function stat(rx_tx)
    local stat = io.open('/sys/devices/pci0000:00/0000:00:1c.4/0000:03:00.0/net/enp3s0/statistics/'..rx_tx..'_bytes')
    stat:setvbuf('no')
    local result = stat:read()
    stat:close()
    return result
end

function net_speed()

    old.rx, old.tx, old.time = stat('rx'), stat('tx'), os.time()
    os.execute("sleep 1")
    cur.rx, cur.tx, cur.time = stat('rx'), stat('tx'), os.time()

    local time_diff = (cur.time - old.time)
    
-- local rx_diff, tx_diff, rx_rate, tx_rate = 0, 0, 0, 0


    if time_diff > 0 then
        local rx_diff = (cur.rx - old.rx)
        local tx_diff = (cur.tx - old.tx)
        local rx_rate = (rx_diff / time_diff)
        local tx_rate = (tx_diff / time_diff)

        if rx_rate > (1024^2) then
            rx_kib = (rx_rate / (1024^2))
            rx_rate = string.format('%3.2f %s', rx_kib, 'M')
        else
            rx_rate = string.format('%3.2f %s', rx_kib, 'K')
        end
            
--        tx_kib = (tx_rate >> 10)
        if tx_rate > (1024^2) then
            local tx_kib = (tx_rate / (1024^2))
            tx_rate = string.format('%3.2f %s', tx_kib, 'M')
        else
            tx_rate = string.format('%3.2f %s', tx_kib, 'K')
        end
    else
        rx_rate = string.format('%s', '???')
        tx_rate = string.format('%s', '???')
    end
    local result = rx_rate..'  '..tx_rate
    return result
end
net_speed()

--[[
widget = {
    plugin = 'timer',
    opts = {period = 2},
    cb = function()
        return {full_text=net_speed(), color='#00e0ff'}
    end,
}]]