[bug#74962] [PATCH v3 4/5] etc/guix-install.sh: Remove 'which' commands from requirements.

[Simon Josefsson via Guix-patches via <guix-patches@gnu.org>]

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Maxim Cournoyer <maxim.cournoyer@gmail.com> writes:

> Hi,
>
> Ludovic Courtès <ludo@gnu.org> writes:
>
>> Simon Josefsson <simon@josefsson.org> skribis:
>>
>>> Ludovic Courtès <ludo@gnu.org> writes:
>>>
>>>> Maxim Cournoyer <maxim.cournoyer@gmail.com> skribis:
>>>>
>>>>> * etc/guix-install.sh (REQUIRE): Remove "which".  Add "nologin".
>>>>> (sys_create_build_user): Use 'type' instead of 'which'.
>>>>>
>>>>> Fixes: <https://issues.guix.gnu.org/74952>
>>>>> Reported-by: Simon Josefsson <simon@josefsson.org>
>>>>> Change-Id: I0675716bab3fc22d3289ee7af2cb0ab33a1cee71
>>>>
>>>> LGTM.
>>>
>>> Using 'type -P' is not POSIX and neither /bin/dash nor /bin/gash
>>> supports it.  It seems like a GNU bash extension.  Is that okay?
>>
>> Oh, not great.  From what you write, I’m not sure what to conclude;
>> just skip this patch and be done with it?
>
> We currently use other Bash-specific features, so I think it's fine to
> embrace the Bash requirement instead of shying away from it.
>
> If we decide that we don't want Bash as a requirement at some point,
> we'll have to change a bunch of things; one of them would be to no
> longer make use of arrays since POSIX shells don't have them, for
> example.

There is a difference to use bashisms in code in Guix intended to be run
on bash, and code we have in the manual that is suggested to be used on
other operating system as part of the Guix installation process.

There appears to be no perfect solution here.  I think 'command -v
nologin' is the closest.  Or just keep the code as-is and use 'which',
but that caused my initial problem (lack of 'which').

I'd like to second-guess why we even bother with using "nologin" instead
of simply hard-coding "/bin/false" or why not "/" which I suppose is not
a executable shell on any system.

/Simon

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