GNU bug report logs - #19760
[bug] "tail -f" with inotify fails to follow a file after a rename()

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Message #19 received at 19760-done <at> debbugs.gnu.org (full text, mbox):

From: Pádraig Brady <P <at> draigBrady.com>
To: Bernhard Voelker <mail <at> bernhard-voelker.de>, 
 Stephane Chazelas <stephane.chazelas <at> gmail.com>, 19760-done <at> debbugs.gnu.org
Subject: Re: bug#19760: [bug] "tail -f" with inotify fails to follow a file
 after a rename()
Date: Tue, 31 Mar 2015 11:56:40 +0100

[Message part 1 (text/plain, inline)]

On 31/03/15 07:30, Bernhard Voelker wrote:
> On 03/31/2015 05:15 AM, Pádraig Brady wrote:
>> +  tail -f continues to follow changes to a file even after it's renamed.
>> +  [bug introduced in coreutils-7.5]
>> +
> 
> It is not 100% clear to me by this sentence what was the actual change;
> maybe a little "again" or "now" would help?
> 
>> --- /dev/null
>> +++ b/tests/tail-2/f-vs-rename.sh
>> @@ -0,0 +1,51 @@
>> +#!/bin/sh
>> +# demonstrate that tail -f works when renaming the tailed files
> 
> s/^d/D/; s/$/./
> 
>> +# Before coreutils-8.24, tail -f a would stop tracking additions to b
>> +# after "mv a b".
>> +
>> +# Copyright (C) 2015 Free Software Foundation, Inc.
>> +
>> +# This program is free software: you can redistribute it and/or modify
>> +# it under the terms of the GNU General Public License as published by
>> +# the Free Software Foundation, either version 3 of the License, or
>> +# (at your option) any later version.
>> +
>> +# This program is distributed in the hope that it will be useful,
>> +# but WITHOUT ANY WARRANTY; without even the implied warranty of
>> +# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
>> +# GNU General Public License for more details.
>> +
>> +# You should have received a copy of the GNU General Public License
>> +# along with this program.  If not, see <http://www.gnu.org/licenses/>.
>> +
>> +. "${srcdir=.}/tests/init.sh"; path_prepend_ ./src
>> +print_ver_ tail
>> +
>> +touch a || framework_failure_
>> +
>> +debug='---disable-inotify'
>> +debug=
>> +tail $debug -f -s.1 a > out 2>&1 & pid=$!
> 
> Shouldn't $debug be removed?  Otherwise maybe a loop over both the
> inotify and the non-inotify mode would make sense?
> 
>> +
>> +check_tail_output()
>> +{
>> +  local delay="$1"
>> +  grep "$tail_re" out > /dev/null ||
>> +    { sleep $delay; return 1; }
>> +}
> 
> Please don't discard grep's output: reading the test's log file is
> easier with this included.
> 
>> +
>> +# Wait up to 12.7s for tail to start
> 
> s/$/./
> 
>> +echo x > a
>> +tail_re='^x$' retry_delay_ check_tail_output .1 7 || fail=1
>> +
>> +mv a b || fail=1
>> +
>> +echo y >> b
>> +# Wait up to 12.7s for "y" to appear in the output:
>> +tail_re='^y$' retry_delay_ check_tail_output .1 7 || fail=1
>> +
>> +kill $pid
>> +
>> +wait
>> +
>> +Exit $fail
> 
> Otherwise +1 (including the changes in tail.c).

All good suggestions.
Latest attached.

thanks for the review!
Pádraig.

[tail-rename-desc.patch (text/x-patch, attachment)]

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