pb.lua

#!/usr/bin/lua

--[[	This file needs to be an executable, so type in your terminal:
	$ chmod +x <filename>
	And move it to your system's bin folder, like:
	$ mv pb.lua /usr/bin/pb
	Then, you can use it like this:
	$ pb 12345
]]

UNITS = {"B", "KB", "MB", "GB", "TB", "PB", "EB", "ZB", "YB"}

function trunc(num, digits)
    local mult = 10 ^ digits

    return math.modf(num * mult) / mult
end

function prettyBytes(num, precision)
    if (math.abs(num) < 1) then
        return num .. " B"
    end

    precision = precision or 3

    exponent = math.min(math.floor(math.log(num < 0 and -num or num, 10) / 3), 9 --[[#(UNITS)]] )

    n = trunc((num < 0 and -num or num) / 1000 ^ exponent, precision)

    return (num < 0 and "-" or "") .. n .. " " .. UNITS[exponent + 1]
end

num = tonumber(arg[1])
result = prettyBytes(num)

print(result)