bug#78910: tail does not support -r added by POSIX.1-2024

On Fri, Jun 27, 2025 at 08:51:10AM -0700, Jim Meyering wrote:
> > >
> > > [1] https://pubs.opengroup.org/onlinepubs/9799919799/utilities/tail.html
> >
> > tail -r comes from the BSDs.
> > Also the BSDs don't have tac(1) which overlaps in functionality quite a bit.
> > I'm a bit surprised -r was added by POSIX, but fair enough.
> 
> "Surprised" is putting it lightly. I am disappointed and am tempted to
> push back and to delay encumbering GNU tail with -r.
> That is an option no GNU system needs, since they've all had tac since
> before 1992-era textutils.
> 
> I've Cc'd Eric Blake, in case someone wants to propose adding tac to
> POSIX in spite of the fact that the BSDs still lack it.

I'll bring up this topic at the next Austin Group meeting.

At any rate, it looks like tail -r was added due to this bug report in
2014 (sadly, it is no longer an option to ask Jorg Schilling why he
wanted it standardized)
https://www.austingroupbugs.net/view.php?id=877

But I did ask at the time (with no answer) why we went with 'tail -r'
instead of 'tac'.

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.
Virtualization:  qemu.org | libguestfs.org