Finding package script files

On my PC I know where to find R scripts that are distributed with many 
packages such as nlme.

I tried to find them on my Mac recently and realised that I don't know 
where to look.

Can anyone let me know?

Something like

  system.file("scripts/ch01.R", package="nlme")

should work on any system.  You can use that for any file installed with 
a package if you know the path relative to the top of the package directory.

Duncan Murdoch