I did the following for #1:

$ ln -s filea fileb
$ ln -s fileb filea
$ cat filea  # symlink to a symlink
cat: files: Too many levels of symbolic links

Then I did the following for #2:

$ mkdir test
$ cd test
$ ln -s ../test dirsym
$ cd dirsym

This allows me to enter dirsym indefinitely -- i could see something 
getting hung up over this if it followed the sym links..

I would imagine this would be true for the final scenario as well.



Trent Shipley wrote:
> Is a *nix file system guranteed to be acyclic?
> 
> That is no:
> 
> File-a  links to file-b and file-b links to file-a
> 
> And more important
> 
> No directory-a contains link-b where link-b points to directory-a.
> 
> Also
> 
> Directory-a contains no link-b to directory-c where directory-c contains 
> link-d to directory-a.