Get random arg

local function rand(...)
    local n = select('#', ...)
    if n < 1 then
        return
    end
    return (select(math.random(1, n), ...))
end

math.randomseed(os.time())
print(rand())
print(rand(1))
print(rand(1, 2, 3))
print(rand(1, nil, 3))