Detecting the operating system?

[Frank Küster <frank@...>]

Hi,

I'd like to detect in a lua script on which (kind of) operating system
I'm running, in order to provide sensible defaults for calls to external
programs (viewers, actually).  Thinking about OS X, I considered

 > if os.execute('nothere 2>/dev/null') / 256 == 127 then
 >    print("does not exist")
 > end

and got the answer

> /dev/null works on UNIX, on Windows it's nul (and does not appear in
> the filesystem).  However, another nice solution would be to walk
> through the path (os.getenv("PATH")).  With other words, write a
> function which does the same as the UNIX which command.
> 
> Note that paths are separated by ";" on Windows instead of ":".

Which brings me to the question, is there some code snippet which I
could use?

Regards, Frank

-- 
Frank Küster
Single Molecule Spectroscopy, Protein Folding @ Inst. f. Biochemie, Univ. Zürich
Debian Developer (teTeX/TeXLive)