Sean O'Dell
9/8/2003 6:24:00 PM
Hugh Sasse Staff Elec Eng wrote:
> Before I attempt to re-invent this wheel:
> Has anyone come up with a method for converting an absolute
> filesystem path into a relative path, given the path to relate to?
> Pruning off the front is relatively easy, but handling ''../''
> correctly is likely to be error prone. Given that I need to cope
> with Ruby 1.6 and 1.8 at the moment, and I will need to do something
> graceful if the paths are on different Windows drives, well, I
> suspect someone has run into this before me.
>
> I need relative paths so I can move between data sets for testing
> and between machines as well.
Strange you should ask. I just wrote one of these and was about to port
it, and some other string utilities, to a C extension object.
It''s brutal, but it works. Feel free to Rubify, anyone:
class String
public
def relative_path(topath)
frompath = self.clone
topath = topath.clone
fromdir = frompath.slice(/^.*?\//)
while(fromdir and frompath.slice(/^.*?\//) == topath.slice(/^.*?\//))
topath.slice!(/^.*?\//)
fromdir = frompath.slice!(/^.*?\//)
end
fromdir = frompath.slice!(/^.*?\//)
while(fromdir)
topath = "../" + topath
fromdir = frompath.slice!(/^.*?\//)
end
return topath
end
def relative_path!(topath)
self.replace(relative_path(topath))
end
end
Sean O''Dell