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Date: Sun, 14 Dec 2025 10:26:24 +0100
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Subject: Re: group '545' does not exist ?
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From: Marco Atzeri via Cygwin <cygwin AT cygwin DOT com>
Reply-To: Marco Atzeri <marco DOT atzeri AT gmail DOT com>
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On 05/12/2025 19:48, Corinna Vinschen via Cygwin wrote:
> On Dec  5 19:30, Corinna Vinschen via Cygwin wrote:
>> On Dec  5 13:40, Corinna Vinschen via Cygwin wrote:
>>> 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).
>>
>> Uhm... there's a problem here.
>>
>> Right now, our newgrp is commandline compatible with Linux' newgrp from
>> shadow-utils:
>>
>> - A single '-' reinitializes the environment.
>> - The group must be given as name, not as GID.
>>
>> This is not commandline compatible with the POSIX definition:
>>
>> - A '-l' reinitializes the environment.
>> - The group may be given as name or GID.
>>
>> I can't just change it to POSIX compatible because this potentially
>> breaks Linux compatibility.
>>
>> What we could do is to check the POSIXLY_CORRECT environment variable
>> and switch the identity to POSIX if this variable is set.
>>
>> Make sense?
> 
> No, scratch that, it's much eaiser.  shadow-utils newgrp let's -l slip
> through, any other -X results in a usage message.  I can change Cygwin's
> newgrp accordingly.
> 
> The only non-compatibility is that Cygwin's newgrp allows to specify a
> command.   shadow-utils nad POSIX newgrp only create a new shell
> environment.
> 
> I guess we can ignore this...
> 
> 
> Corinna
> 


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