GNU bug report logs - #78910
tail does not support -r added by POSIX.1-2024

Previous Next

Full log

Message #44 received at 78910 <at> debbugs.gnu.org (full text, mbox):

From: Collin Funk <collin.funk1 <at> gmail.com>
To: Eric Blake <eblake <at> redhat.com>
Cc: Bernhard Voelker <mail <at> bernhard-voelker.de>,
 Pádraig Brady <P <at> draigbrady.com>,
 Jim Meyering <jim <at> meyering.net>, 78910 <at> debbugs.gnu.org
Subject: Re: bug#78910: tail does not support -r added by POSIX.1-2024
Date: Tue, 01 Jul 2025 12:44:55 -0700

Hi Eric,

Eric Blake <eblake <at> redhat.com> writes:

> Remember, the POSIX synopsis lines lists two distinct invocation
> styles:
>
> tail [-f] [-c number|-n number] [file]
> tail -r [-n number] [file]

Yep, I was going to mention this too. But I was not sure if it should
have a mention in the description to make it more clear.

> which means undefined behavior from the POSIX point of view if -f and
> -r are ever attempted at the same time.  Therefore, whatever GNU
> decides to do on that combo (preferably, diagnose it early with an
> error and exit, since I can't figure out anything else useful it could
> do) will not violate POSIX.

I think it should be standardized to fail when -f and -r are used
together. That seems like the only reasonable behavior to me.

Thanks,
Collin

Previous Next

GNU bug tracking system
Copyright (C) 1999 Darren O. Benham, 1997,2003 nCipher Corporation Ltd, 1994-97 Ian Jackson.