Battery Widget using powersave

I've written a simple Lua function for printing the battery state - [ 44%/77m▾ ] - to a widget. It uses the (quite common) "powersave" command - which is called directly from Lua via popen(). You do not have to run some other script at session startup, and you do not have to compile additional C bindings. Just install powersave and add the following lines to your rc.lua:

-- the widget
mybattmon = widget({ type = "textbox", name = "mybattmon", align = "right" })

-- returns a string with battery info
function battery_status ()
    local battery = 0
    local time = 0
    local state = 0  -- discharging = -1, charging = 1, nothing = 0
    local icon = ""
    local fd = io.popen("powersave -b", "r")
    if not fd then
        do return "no info" end

    end
    local text = fd:read("*a")
    io.close(fd)
    if string.match(text, "discharging") then
        state = -1
        icon =  "▾"
    else
        state = 1
        icon = "▴"
    end

    battery = string.match(text, "Remaining percent: (%d+)")
    time = string.match(text, "Remaining minutes: (%d+)")
    -- above string does not always match
    if not time then
        time = string.match(text, "(%d+) minutes until fully charged")
    end

    return battery .. "%/" .. time .. "m" .. "<b>" .. icon .."</b>"
end

-- Hook called every second
function hook_timer ()
    --mytextbox.text = " " .. os.date() .. " "
    mybattmon.text = " " .. battery_status() .. " "
end