local currentProg = 0
local maxsize = 8
local time_to_full = 10
local step = 0.01
local move_per_step = maxsize / (time_to_full / step)

local function updateBar(name)
    currentProg = currentProg + ((move_per_step / maxsize) * 100)
    local formspec = "size[8,2]" ..
                 "button[0,0;" .. ((maxsize / 100) * currentProg) .. ",1;name;".. math.floor(currentProg) .."%]" ..
                 "label[0,1;We are noticing incredible progress.]"
    minetest.show_formspec("testmod:test", formspec)
    if(currentProg < 100) then
        minetest.after(step, updateBar, name)
    end
end

minetest.register_chatcommand("progbar", {
    params = "",
    description = "Shows a progress bar.",
    func = function(name)
        currentProg = 0
        minetest.after(step, updateBar, name)
    end,
})