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Date: Fri, 5 Dec 2025 13:40:16 +0100
To: cygwin AT cygwin DOT com
Subject: Re: group '545' does not exist ?
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From: Corinna Vinschen via Cygwin <cygwin AT cygwin DOT com>
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On Dec  5 09:28, Marco Atzeri via Cygwin wrote:
> On 04/12/2025 21:50, Brian Inglis via Cygwin wrote:
> > On 2025-12-04 08:00, Jon Turney via Cygwin wrote:
> > > Actually, I think this is a shortcoming of the cygwin version of newgrp.
> > > The SUS description [1] of newgrp allows a numeric group id to be
> > > specified.
> > > (In fact, it includes the clarifying remark "If group is a non-
> > > negative numeric string and exists in the group database as a group
> > > name, the numeric group ID associated with that group name will be
> > > used as the group ID", which suggests a, um, straightforward
> > > implementation)
> > > But it seems that our implementation only currently handles a group
> > > name (See [2]).
> > > [1] https://pubs.opengroup.org/onlinepubs/7908799/xcu/newgrp.html
> > 
> > That's OG SUSV2 1997 - current is at:
> > 
> >      https://pubs.opengroup.org/onlinepubs/9799919799/utilities/newgrp.html
> > 
> > > [2] https://cygwin.com/cgit/newlib-cygwin/tree/winsup/utils/newgrp.c#n166

Shouldn't be too hard to add to our newgrp(1).

> Thanks Jon, Brian,
> 
> do you know also why the group in /etc/passwd is ignored and
> "Nobody/Nessuno" is used ?
> 
> $ cat passwd
> Marco:*:197608:545:U-DESKTOP-L2T1NQ9\Utente,S-1-5-21-1151457081-841113255-780074606-1000:/home/Marco:/bin/bash
> 
> $ id
> uid=197608(Marco) gid=197121(NESSUNO)
> groups=197121(NESSUNO),545(Users),4(INTERACTIVE),66049(ACCESSO

This seems to be a bug introduced... let me check... when adding
the newgrp(1) tool in fact.  Looks like this patch disabled the
behaviour.

https://cygwin.com/cgit/newlib-cygwin/commit/?id=dc7b67316d01

I'll debug this later today.  I have to setup a non-domain debugging
environment first...


Corinna

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