Re: 4th set of permission bits?
On Sat, Nov 25, 2000 at 01:00:27PM +0800, Robert Marlow wrote:
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> On Fri, 24 Nov 2000, Marcus Brinkmann wrote:
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> > There are two reasons:
> >
> > 1. No tools support manipulation of the fourth set of permission bits.
> > 2. There is one more bit. If 0, for not-logged-in user the permission set
> > of "other" is used. If 1, the fourth set is used. It is undecided if the
> > this should probably be reversed (so the permissions for not logged in
> > users are empty by default).
>
> I'm not understanding the purpose of this extra bit determining whether the
> other or 4th set permissions are used. Would it not be simpler to have
> the 4th set of permissions default to being the same as the 3rd set and a user
> can alter this 4th set if they feel it necessary?
That's exactly the point of the fourth flag. You can only store so much
values in three bits, and there is no place for the ninth value "use the
third fields as a default". Remember that you need X--- to prevent access by
the non-logged in user (where X is the extra bit we are talking about,
S_IUSEUNK in <include/bits/stat.h>)
It's a bit like a light switch. It can be off or on (one bit). But you need
an extra switch to toggle to another light switch.
Thanks,
Marcus
--
`Rhubarb is no Egyptian god.' Debian http://www.debian.org brinkmd@debian.org
Marcus Brinkmann GNU http://www.gnu.org marcus@gnu.org
Marcus.Brinkmann@ruhr-uni-bochum.de
http://www.marcus-brinkmann.de
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