How can figure out what os is a user using?

I was wondering how can I figure out os is the user using?

I tried using os but its just a table that contains time and difftime

for i,v in pairs (os) do
	print(v)
end

What do I use to find out the os of the user?

This question already has an answer here: https://scriptinghelpers.org/questions/10560/is-it-possible-to-detect-a-device