Removing ".." and "." from a file path

[Lothar Scholz]

I only found the "File.expand_path" function to make a relative into
an absolute path, but what about the ".." and "." components.

I need a canonical version of a file path, so a function that would
also remove adjacent '/' or '\' and transform to the corresponding OS
path separator would be the best.

Is there anything like this available ?