Print a number in its hexadecimal format. Based on http://snipplr.com/view/13086/number-to-hex/

num2hex.lua

-- convert a number to its hex representation
function num2hex(num, hexdigits)
	local hexstr = '0123456789abcdef'
	local s = ''
	while num > 0 do
		local mod = math.fmod(num, 16)
		s = string.sub(hexstr, mod+1, mod+1) .. s
		num = math.floor(num / 16)
	end
	if s == '' then s = '0' end

	while s:len() < hexdigits do
		s = "0" .. s
	end

	return s
end