The Platform library offers a simple, reliable, means of determining
what platform Ruby is running on.  Underlying Platform is the
RUBY_PLATFORM constant.  This library is parsing this constant for
information.  You could easily do this yourself.  We've just taken the
hassle out of it for you and hopefully covered a few of the more
unusual cases you mightn't have thought of yourself.

WWW:	http://platform.rubyforge.org/