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Message-ID: <de6f8c31-2e4d-48e3-af61-6e6a2b640f79@dronecode.org.uk>
Date: Thu, 4 Dec 2025 15:00:14 +0000
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Subject: Re: group '545' does not exist ?
To: Marco Atzeri <marco.atzeri@gmail.com>
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 <48e6fb4c-2341-4f43-b158-d70a9b391f91@gmail.com>
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From: Jon Turney via Cygwin <cygwin@cygwin.com>
Reply-To: Jon Turney <jon.turney@dronecode.org.uk>
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On 03/12/2025 15:20, Marco Atzeri via Cygwin wrote:
> On 03/12/2025 13:50, Roland Mainz via Cygwin wrote:
>> On Wed, Dec 3, 2025 at 12:57 PM Marco Atzeri via Cygwin
>> <cygwin@cygwin.com> wrote:
>>>
>>> I am probably missing something, but this seems bizarre (to me)
>>>
>>> $ id
>>> uid=197608(Marco) gid=197121(NESSUNO) groups=197121(NESSUNO),114(Account
>>> locale e membro del gruppo Administrators),544(Administrators),547(Power
>>> Users),545(Users),4(INTERACTIVE),66049(ACCESSO CONSOLE),11(Authenticated
>>> Users),15(Questa organizzazione),113(Account
>>> locale),4095(CurrentSession),66048(LOCALE),262154(Autenticazione
>>> NTLM),405504(Livello obbligatorio alto)
>>>
>>>
>>> $ newgrp 545 touch prova2
>>> newgrp: group '545' does not exist
>>>
>>> $ uname -svr
>>> CYGWIN_NT-10.0-26200 3.6.5-1.x86_64 2025-10-09 17:21 UTC
>>
>> Please use the group name ("Users" in your case) and not the numeric GID.
>>
>> If you really need to use the numeric gid, then you can use $ getent
>> group 545 | awk -F ':' '{ print $1 } ' # to convert it to a group name
>> (see comment below about localised Windows builtin group names), and
>> then plug that into newgrp:
>> $ newgrp "$(getent group 545 | awk -F ':' '{ print $1 } ')" touch 
>> prova2 #
>>
>> BTW: There is one issue with this: Windows builtin account names
>> (users+groups) can be localised, e.g. English gid=545 is "Users",
>> while in German it's "Benutzer".
>>
>> 
> as usual PEBCAK

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
[2] https://cygwin.com/cgit/newlib-cygwin/tree/winsup/utils/newgrp.c#n166


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