GNU bug report logs - #9266
tail -F does not follow through symlinks

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Message #5 received at submit <at> debbugs.gnu.org (full text, mbox):

From: Bart Vanhaute <bart.vanhaute <at> gmail.com>
To: bug-coreutils <at> gnu.org
Subject: tail -F does not follow through symlinks
Date: Tue, 9 Aug 2011 10:14:40 +0200

When I use tail -F to follow a file that is a symlink to another file,
and that second file gets replaced, tail no longer follows the new
file. I am not sure if this scenario is actually supported, but the
current behaviour is unexpected to me.

Detailed scenario to reproduce:

in one terminal:
$ ln -s f a
$ touch f
$ tail -F a

in another terminal:
$ mv f f.0
$ echo 'hello' > f

The output in terminal one will show
tail: `a' has become inaccessible: No such file or directory
but it will not show the 'hello' message.

I am using coreutils version 8.5 on debian sid (linux kernel version
3.0.0), but I noticed the same behaviour in coreutils version 8.9 on
opensuse (linux kernel version 2.6.37).

greetings,
Bart.

Message #8 received at 9266 <at> debbugs.gnu.org (full text, mbox):

From: Jim Meyering <jim <at> meyering.net>
To: Bart Vanhaute <bart.vanhaute <at> gmail.com>
Cc: 9266 <at> debbugs.gnu.org
Subject: Re: bug#9266: tail -F does not follow through symlinks
Date: Tue, 09 Aug 2011 18:28:30 +0200

Bart Vanhaute wrote:

> When I use tail -F to follow a file that is a symlink to another file,
> and that second file gets replaced, tail no longer follows the new
> file. I am not sure if this scenario is actually supported, but the
> current behaviour is unexpected to me.
>
> Detailed scenario to reproduce:
>
> in one terminal:
> $ ln -s f a
> $ touch f
> $ tail -F a
>
> in another terminal:
> $ mv f f.0
> $ echo 'hello' > f
>
> The output in terminal one will show
> tail: `a' has become inaccessible: No such file or directory
> but it will not show the 'hello' message.
>
> I am using coreutils version 8.5 on debian sid (linux kernel version
> 3.0.0), but I noticed the same behaviour in coreutils version 8.9 on
> opensuse (linux kernel version 2.6.37).

Thank you for the report.
That is indeed a difference in behavior from
the way tail works without inotify support.

If you want the old behavior (though there is no guarantee this
option will be around forever -- it's deliberately not documented),
use tail's ---disable-inotify option.  Note the three leading '-'s.

Another work-around is to use readlink to give tail
an absolute name for the file:

    tail -F "$(readlink -e a)"

Regarding tail's behavior change, we'll have to investigate
if/how to address it.

Message #11 received at 9266 <at> debbugs.gnu.org (full text, mbox):

From: Assaf Gordon <assafgordon <at> gmail.com>
To: 9266 <at> debbugs.gnu.org
Subject: Re: bug#9266: tail -F does not follow through symlinks
Date: Tue, 30 Oct 2018 02:50:52 -0600

tags 9266 notabug
close 9266
stop

(triaging old bugs)

On 2011-08-09 10:28 a.m., Jim Meyering wrote:
> Bart Vanhaute wrote:
> 
>> When I use tail -F to follow a file that is a symlink to another file,
>> and that second file gets replaced, tail no longer follows the new
>> file. I am not sure if this scenario is actually supported, but the
>> current behaviour is unexpected to me.

> Thank you for the report.
> That is indeed a difference in behavior from
> the way tail works without inotify support.
> 
> If you want the old behavior (though there is no guarantee this
> option will be around forever -- it's deliberately not documented),
> use tail's ---disable-inotify option.  Note the three leading '-'s.

with no further comments in 7 years, I'm closing this bug.

-assaf

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