Re: Fwd: Re: error.c: "Unknown system error" should report errno value

[Martin Koeppe]

On Wed, 3 Oct 2007, Jim Meyering wrote:
> Martin Koeppe <address@hidden> wrote:
> > A question arises: How should one portably test for "root"? Neither
> > "root" nor uid 0 seem to be a POSIX requirement. I found one solution
> > so far, but I'm not sure how good it really is:
> >
> > For shell scripts run:
> > $ /usr/sbin/chroot / /bin/true
> > If successful, you have root rights.
>
> I'm leery of this.
> What if chroot works for non-privileged users on some type of system?
>
> Since Interix is the problem here, how about adding
> a test that'd be run solely on that system?

Yes, no problem with that.  I only thought there might be a 
possibility to check the root-ness without an explicit comparison of 
uid or username.  This need not necessarily be the chroot() 
function.  But I don't know the POSIX standard in that detail.

If you want an explicit check, then for Interix 3 different users/uids 
must be checked:  System (uid ???), Domain Administrator (uid 1049076) 
and local Administrator (uid 197108). All of these have "root" rights.
See: http://www.interopcommunity.com/faqs.aspx#307

Martin