From: Daniel Berger <djberg96@...>
Date: 2007-03-10T06:00:12+09:00
Subject: Re: Getting to the last file in a chain of symlinks

On Mar 9, 12:44 pm, "AdSR" <artur_spr...@yahoo.com> wrote:
> On 9 Mar, 20:10, "Daniel Berger" <djber...@gmail.com> wrote:
>
>
>
> > Hi all,
>
> > Here's a little code snippet I thought I'd share. It follows a chain
> > of symlinks until you get down to the "real" file. Anyone got a better
> > approach?
>
> > # On Solaris 10, Sunblade 150
> > #
> > # /dev/fd0      -> fd0c
> > # /dev/fd0c     -> diskette0
> > # /dev/diskett0 -> ../devices/pci@1f,0/isa@7/dma@0,0/floppy@0,3f0:c
> > #
>
> > file = '/dev/fd0'
>
> > while true
> >    Dir.chdir(File.dirname(file))
> >    file = File.expand_path(File.readlink(file))
> >    break unless File.symlink?(file)
> > end
>
> > puts file # /devices/pci@1f,0/isa@7/dma@0,0/floppy@0,3f0:c
>
> > Regards,
>
> > Dan
>
> require 'pathname'
>
> puts Pathname.new('/dev/fd0').realpath

Oh, dang, forgot about that.

> I didn't check what would happen for cyclic dependencies.

>ls -l
lrwxrwxrwx   1 djberge  other          5 Mar  9 12:25 link1 -> link2
lrwxrwxrwx   1 djberge  other          5 Mar  9 12:23 link2 -> link1
-rw-r--r--   1 djberge  other         57 Mar  9 12:45 test.rb

/usr/local/lib/ruby/1.8/pathname.rb:415:in `realpath_rec': Number of
symbolic links encountered during path name traversal exceeds
MAXSYMLINKS - /export/home/djberge/workspace/ruby_test/lib/test/link2
(Errno::ELOOP)
        from /usr/local/lib/ruby/1.8/pathname.rb:425:in `realpath_rec'
        from /usr/local/lib/ruby/1.8/pathname.rb:453:in `realpath'
        from test.rb:2

Dunno what happens on other platforms.

Regards,

Dan