bug#13447: ln "" foo gives misleading error message

[Pádraig Brady]

On 01/15/2013 08:23 AM, Ken Irving wrote:
> (Previously sent in error to the bug-gnu-utils list.)
>
> I've been using symbolic links in a non-file-related way, e.g., to store
> arbitrary string values, but find that if I try to create a symlink with
> an empty 'target' name, e.g., as 'ln -s "" foo', the error message emitted
> is not really correct.
>
>      $ ln -s "" foo
>      ln: creating symbolic link `foo' -> `': No such file or directory
>      $ ln -sf "" foo
>      ln: creating symbolic link `foo' -> `': No such file or directory
>
> A link can be created when no file or directory exists, e.g.,
>
>      $  stat x || ln -s x foo && echo ok
>      stat: cannot stat `x': No such file or directory
>      ok
>
> so it seems that 'No such file or directory' must not be the actual
> reason for the failure.  Perhaps something like 'null target name'
> would be more accurate?
>
> I only happened upon this in working on a test script, and have no
> expectation for the operation to succeed.

We're just reporting what the operating system returns here:

$ python -c 'import os; os.symlink("","tl")'
Traceback (most recent call last):
  File "<string>", line 1, in <module>
OSError: [Errno 2] No such file or directory

Interestingly I notice that solaris for example allows a NULL old_path.
I suppose we could handle this case specially like:

  if (errno == ENOENT && !*old_path)
    error(...,"An empty target is not supported on this system");

Though I'm not sure there's much benefit in a specific
error message in this case?

thanks,
Pádraig.