[Python-Dev] Add os.path.resolve to simplify the use of os.readlink

[Antoine Pitrou]

On Thu, 21 Jun 2012 10:23:25 -0000
"Armin Ronacher" <armin.ronacher at active-4.com> wrote:
> Due to an user error on my part I was not using os.readlink correctly. 
> Since links can be relative to their location I think it would make sense
> to provide an os.path.resolve helper that automatically returns the
> absolute path:
> 
>     def resolve(filename):
>         try:
>             target = os.readlink(filename)
>         except OSError as e:
>             if e.errno == errno.EINVAL:
>                 return abspath(filename)
>             raise
>         return normpath(join(dirname(filename), target))

Note that abspath() is buggy in the face of symlinks, for example it
will happily collapse /etc/foo/../bar into /etc/bar, even
though /etc/foo might be a link to /usr/lib/foo

The only safe way to collapse ".." elements is to resolve symlinks.

Regards

Antoine.