2 Aug
2019
2 Aug
'19
8:35 a.m.
[Subject line changed]
Hi.
Doug McIlroy:
Yet clean as the idea of groups was, it has been used
only sporadically
(in my experience).
I suspect this was true mainly at Research, where the whole place was
not large. Other people, as pointed out, found groups to be very useful.
"John P. Linderman" <jpl.jpl(a)gmail.com> wrote:
This changed when you
could be in multiple groups at the same time (a BSD invention?),
Yes, at 4.2 BSD. The so-called group set.
and your
primary group automatically changed to the group owning your current
working directory (iff you belonged to that group).
No. Your process simply carried around a bunch of groups with it, and if
the group of the directory matched the primary group or a member of the
group set, you got group permission.
Arthur Krewat <krewat(a)kilonet.net>et>:
There's also the setgid bit on directories, that
when files are created,
they will be in the group that the parent directory has on it.
IIRC this was a Sun invention. It was in SunOS 4.x, and may even have
been in SunOS 3.x.
Also, I don't think it's been mentioned, but
there's the setuid bit on
directories - otherwise known as the sticky bit. When set, even if you
have rights to "write" the directory (meaning, delete files), you can't
delete those owned by other users. Useful for /tmp
Also a SunOS invention, IIRC.
I have no idea what the timeline is for either of
these features :)
Timeline is late 80s, SunOS 4.0, I believe. (Larry? :-)
These ideas later propogated into SVR4 / Solaris, Linux and most (if not all)
the other proprietary Unixes.
HTH,
Arnold