What determines the encoding of File#path?

In ruby 1.8.7, what determines what the encoding of File#path will be? The filesystem? A configuration somewhere? The encoding of each individual file?

I've seen two different encodings in otherwise identical environments on different OS's.

Related question: Reading filename in multiple OS without encodin开发者_如何学JAVAg problem with Ruby

update

I guess I need to set/know the encoding of the filesystem... this does not help though (unless I'm putting it in the wrong place)...

export LC_ALL=en_US.UTF-8
export LC_CTYPE=en_US.UTF-8

Theoratically you can read the system's encoding from

ENV['LC_LANG']

and you can set it the same way for the ruby script:

ENV['LC_LANG']=en_US.UTF-8

Same goes for the other encoding specific environment variables.