Switching groups with newgrp - how to get the new group with |GetTokenInformation()| ?

[Glenn Strauss]

On Wed, Mar 06, 2024 at 02:01:06PM +0100, Corinna Vinschen via Cygwin wrote:
> On Mar  5 23:38, Dan Shelton via Cygwin wrote:
> > On Sat, 24 Feb 2024 at 14:11, Corinna Vinschen via Cygwin
> > <cygwin@cygwin.com> wrote:
> > >
> > > On Feb 23 22:15, Dan Shelton via Cygwin wrote:
> > > > HOWEVER, there is another Cygwin bug:
> > > > "getent group mywingrp1" does not list any group members, even after
> > > > "net localgroup mywingrp1 mywinuser44 /add", which is a POSIX
> > > > violation.
> > >
> > > Not a bug.  Two problems:
> > >
> > > - Getting members of a group can be an extremly costly operation
> > >   in a domain or, worse, a domain forest, or even worse, if the
> > >   domain or domain forest is remote.
> > >
> > > - Alonmg the same lines, getting members of a group can be extremly
> > >   costly in big orgs with thousands of users.  Nobody want's to clutter
> > >   up space with the list of members in the "Domain Users" group.
> > >
> > > - Permissions to enumerate members of a group are restricted.
> > >   By default only admins and group members are allow to enumerate
> > >   members and this can be restricted further by domain admins.
> > >
> > > Therefore we dropped even trying to populate gr_mem, considering
> > > that even in its original form on Unix systems, it's used only
> > > to add supplementary groups.  To do this right on Windows is even
> > > more costly than blindly enumerating.
> > >
> > > It's not a bug, it's a feature :)
> > 
> > Could you add an option to getent so that the full lookup can be
> > requested via command line, pls?
> 
> That's not possible.  getent just calls getpwent/getgrent.
> 
> > Always editing /etc/nsswitch.conf
> > forth and back is not a elegant solution, aside from race conditions
> > with other users on a system
> 
> So, here we go again.
> 
> - What exactly are you trying to accomplish by enumerating the accounts?
>   Maybe you won't actually need it for your task at hand.
> 
> - Why do you have to change nsswitch.conf "back and forth"?
>   Just change it once and you're done.
> 
> 
> Corinna

Hello
> > Dan Shelton - Cluster Specialist Win/Lin/Bsd

> > Always editing /etc/nsswitch.conf
> > forth and back is not a elegant solution, aside from race conditions
> > with other users on a system

Please check the man page for getent.

man getent
getent --help

You can use -s or --service to override the service used without
editing nsswitch.conf.  The man page on Linux provides an example
with a bit more details than the man page for getent under cygwin.
https://www.man7.org/linux/man-pages/man1/getent.1.html