[R] How to detect if R is running on Mac OS X?

[Philippe Grosjean]

This question is probably trivial, but I don't find the answer. I have 
code that is different for Windows, Unix/Linux and Mac OSX. The man page 
of .Platform tells that .Platform$OS.type is the right way to test for 
it... but it also tels that it returns either "windows" or "unix". Is 
Mac OS X reported as "unix"? If yes, how do I make the difference?
Thanks,

Philippe Grosjean