local wibox = require("wibox")
local awful = require("awful")

volume_widget = wibox.widget.textbox()
volume_widget:set_align("right")
volume_widget:set_font("DejaVu Sans Mono 9")

function update_volume(widget)
    -- The following approach uses io.popen() to launch external application
    -- It is not good, because it causes application lock
    -- We will use awful.util.pread() instead
    --local fd = io.popen("amixer sget Master")
    --local status = fd:read("*all")
    --fd:close()
    local status = awful.util.pread("amixer sget Master")

    -- Parse it
    local volume = string.match(status, "(%d?%d?%d)%%")
    volume = string.format("% 3d", volume)
    status = string.match(status, "%[(o[^%]]*)%]")

    if string.find(status, "on", 1, true) then
        -- For the volume numbers
        volume = volume .. "%"
    else
        -- For the mute button
        volume = volume .. "M"
    end

    widget:set_markup(volume)
    widget:buttons(awful.util.table.join(
            -- Left-click to toggle
            awful.button({ }, 1, function () awful.util.spawn_with_shell('amixer set Master toggle && echo "update_volume(volume_widget)" | awesome-client') end),
            -- Right-click to launch pavucontrol
            awful.button({ }, 3, function () awful.util.spawn("pavucontrol") end),
            -- Scroll to change volume
            awful.button({ }, 4, function () awful.util.spawn_with_shell('amixer set Master on 4%+ && echo "update_volume(volume_widget)" | awesome-client') end),
            awful.button({ }, 5, function () awful.util.spawn_with_shell('amixer set Master on 4%- && echo "update_volume(volume_widget)" | awesome-client') end)))
end

update_volume(volume_widget)

-- Update every 5 seconds (widget data is updated automatically, when you change volume using keybinds defined in rc.lua. See Multimedia section in rc.lua)
mytimer = timer({ timeout = 5 })
mytimer:connect_signal("timeout", function () update_volume(volume_widget) end)
mytimer:start()