From debbugs-submit-bounces@debbugs.gnu.org Fri Apr 20 10:56:40 2018 Received: (at submit) by debbugs.gnu.org; 20 Apr 2018 14:56:40 +0000 Received: from localhost ([127.0.0.1]:34237 helo=debbugs.gnu.org) by debbugs.gnu.org with esmtp (Exim 4.84_2) (envelope-from ) id 1f9XSq-0001IE-Fk for submit@debbugs.gnu.org; Fri, 20 Apr 2018 10:56:40 -0400 Received: from eggs.gnu.org ([208.118.235.92]:54050) by debbugs.gnu.org with esmtp (Exim 4.84_2) (envelope-from ) id 1f9XRv-0001Fo-De for submit@debbugs.gnu.org; Fri, 20 Apr 2018 10:55:43 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1f9XRp-0000uq-5v for submit@debbugs.gnu.org; Fri, 20 Apr 2018 10:55:38 -0400 X-Spam-Checker-Version: SpamAssassin 3.3.2 (2011-06-06) on eggs.gnu.org X-Spam-Level: X-Spam-Status: No, score=0.8 required=5.0 tests=BAYES_50,T_HK_NAME_DR autolearn=disabled version=3.3.2 Received: from lists.gnu.org ([2001:4830:134:3::11]:55846) by eggs.gnu.org with esmtps (TLS1.0:RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1f9XRp-0000uh-10 for submit@debbugs.gnu.org; Fri, 20 Apr 2018 10:55:37 -0400 Received: from eggs.gnu.org ([2001:4830:134:3::10]:44987) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1f9XRn-0000FI-NJ for bug-coreutils@gnu.org; Fri, 20 Apr 2018 10:55:36 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1f9XRj-0000pc-RK for bug-coreutils@gnu.org; Fri, 20 Apr 2018 10:55:35 -0400 Received: from mxchg03.rrz.uni-hamburg.de ([134.100.38.113]:36885) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1f9XRj-0000ix-Bj for bug-coreutils@gnu.org; Fri, 20 Apr 2018 10:55:31 -0400 Received: from localhost (localhost [127.0.0.1]) by mxchg03.rrz.uni-hamburg.de (Postfix) with ESMTP id 90E051E040B for ; Fri, 20 Apr 2018 16:55:26 +0200 (CEST) X-Virus-Scanned: by University of Hamburg ( RRZ / mgw05.rrz.uni-hamburg.de ) Received: from mxchg03.rrz.uni-hamburg.de ([127.0.0.1]) by localhost (mxchg03.rrz.uni-hamburg.de [127.0.0.1]) (amavisd-new, port 10324) with ESMTP id 8PvGuZaG1jex for ; Fri, 20 Apr 2018 16:55:26 +0200 (CEST) Received: from mailhost.uni-hamburg.de (mailhost.uni-hamburg.de [134.100.38.99]) by mxchg03.rrz.uni-hamburg.de (Postfix) with ESMTPS for ; Fri, 20 Apr 2018 16:55:26 +0200 (CEST) Received: from localhost (localhost [127.0.0.1]) by mailhost.uni-hamburg.de (Postfix) with ESMTP id 84CB012E4A for ; Fri, 20 Apr 2018 16:55:26 +0200 (CEST) X-Virus-Scanned: by University of Hamburg ( RRZ / mh06.rrz.uni-hamburg.de ) Received: from mailhost.uni-hamburg.de ([134.100.38.99]) by localhost (mailhost.uni-hamburg.de [127.0.0.1]) (amavisd-new, port 20124) with LMTP id S3vutObqMomx for ; Fri, 20 Apr 2018 16:55:26 +0200 (CEST) Received: from cortex.rrz.uni-hamburg.de (cortex.rrz.uni-hamburg.de [134.100.3.33]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) (Authenticated sender: rznv039@uni-hamburg.de) by mailhost.uni-hamburg.de (Postfix) with ESMTPSA id 7203F12E7E for ; Fri, 20 Apr 2018 16:55:26 +0200 (CEST) Date: Fri, 20 Apr 2018 16:56:23 +0200 From: "Dr. Thomas Orgis" To: bug-coreutils@gnu.org Subject: undocumented change in tail in 8.28 (pipe output monitoring) Message-ID: <20180420165623.012bb2fb@cortex.rrz.uni-hamburg.de> Organization: =?UTF-8?B?VW5pdmVyc2l0w6R0?= Hamburg X-Mailer: Claws Mail 3.15.0-dirty (GTK+ 2.24.31; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: multipart/signed; micalg=SHA256; boundary="Sig_/ocPgogsR8VlybqlNseceUO6"; protocol="application/pkcs7-signature" X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] [fuzzy] X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.6.x X-Received-From: 2001:4830:134:3::11 X-Spam-Score: -5.0 (-----) X-Debbugs-Envelope-To: submit X-Mailman-Approved-At: Fri, 20 Apr 2018 10:56:39 -0400 X-BeenThere: debbugs-submit@debbugs.gnu.org X-Mailman-Version: 2.1.18 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: debbugs-submit-bounces@debbugs.gnu.org Sender: "Debbugs-submit" X-Spam-Score: -6.0 (------) --Sig_/ocPgogsR8VlybqlNseceUO6 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable Hi all, during debugging of a background process issue where I have tail -f feeding into a pipe, I was surprised by a change in tail introduced in release 8.28 of GNU coreutils: The monitoring of the output pipe and silent exit of tail e.g. in the case of tail -f /dev/null | true . This differs from earlier versions and also from BSD, for example. I see some subtle portability bugs here. One one platform, killing the end of a pipe fed by tail will cleanly end the tail process, too, without tail attempting to write new data and failing _then_. On the other platform, the pipe stays there until new data arrives to cause tail to get the error trying to write to the pipe. Regardless of what behaviour is sensible, it causes scripts that take GNU tail's behaviour for granted to have different behaviour with other versions of this very traditional UNIX tool. So at the very least, this change should be documented as a possible implementation difference in the manual, and for sure with the version that changed behaviour, shouldn't it? Regards, Thomas Orgis --=20 Dr. Thomas Orgis Universit=C3=A4t Hamburg RRZ / Basis-Infrastruktur / HPC Schl=C3=BCterstr. 70 20146 Hamburg Tel.: 040/42838 8826 Fax: 040/428 38 6270 --Sig_/ocPgogsR8VlybqlNseceUO6 Content-Type: application/pkcs7-signature; name=smime.p7s Content-Transfer-Encoding: base64 Content-Disposition: attachment; filename=smime.p7s MIAGCSqGSIb3DQEHAqCAMIACAQExDzANBglghkgBZQMEAgEFADCABgkqhkiG9w0B BwEAAKCCEKIwggTVMIIDvaADAgECAghQTsb1PRG0ZDANBgkqhkiG9w0BAQsFADBx MQswCQYDVQQGEwJERTEcMBoGA1UEChMTRGV1dHNjaGUgVGVsZWtvbSBBRzEfMB0G A1UECxMWVC1UZWxlU2VjIFRydXN0IENlbnRlcjEjMCEGA1UEAxMaRGV1dHNjaGUg VGVsZWtvbSBSb290IENBIDIwHhcNMTQwNzIyMTIwODI2WhcNMTkwNzA5MjM1OTAw WjBaMQswCQYDVQQGEwJERTETMBEGA1UEChMKREZOLVZlcmVpbjEQMA4GA1UECxMH REZOLVBLSTEkMCIGA1UEAxMbREZOLVZlcmVpbiBQQ0EgR2xvYmFsIC0gRzAxMIIB IjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEA6ZvDZ4X5Da71jVTDllA1PWLp bkztlNcAW5UidNQg6zSP1uzAMQQLmYHiphTSUqAoI4SLdIkEXlvg4njBeMsWyyg1 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(128/128 bits)) (No client certificate requested) by mail.magicbluesmoke.com (Postfix) with ESMTPSA id A30209E9A; Sat, 21 Apr 2018 01:56:14 +0100 (IST) Subject: Re: bug#31225: undocumented change in tail in 8.28 (pipe output monitoring) To: "Dr. Thomas Orgis" , 31225-done@debbugs.gnu.org References: <20180420165623.012bb2fb@cortex.rrz.uni-hamburg.de> From: =?UTF-8?Q?P=c3=a1draig_Brady?= Message-ID: Date: Fri, 20 Apr 2018 17:56:10 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.8.0 MIME-Version: 1.0 In-Reply-To: <20180420165623.012bb2fb@cortex.rrz.uni-hamburg.de> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit X-Spam-Score: 0.0 (/) X-Debbugs-Envelope-To: 31225-done X-BeenThere: debbugs-submit@debbugs.gnu.org X-Mailman-Version: 2.1.18 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: debbugs-submit-bounces@debbugs.gnu.org Sender: "Debbugs-submit" X-Spam-Score: -1.0 (-) On 20/04/18 07:56, Dr. Thomas Orgis wrote: > Hi all, > > during debugging of a background process issue where I have tail -f > feeding into a pipe, I was surprised by a change in tail introduced in > release 8.28 of GNU coreutils: The monitoring of the output pipe and > silent exit of tail e.g. in the case of > > tail -f /dev/null | true > > . This differs from earlier versions and also from BSD, for example. I > see some subtle portability bugs here. One one platform, killing the > end of a pipe fed by tail will cleanly end the tail process, too, > without tail attempting to write new data and failing _then_. On the > other platform, the pipe stays there until new data arrives to cause > tail to get the error trying to write to the pipe. > > Regardless of what behaviour is sensible, it causes scripts that > take GNU tail's behaviour for granted to have different behaviour with > other versions of this very traditional UNIX tool. > > So at the very least, this change should be documented as a possible > implementation difference in the manual, and for sure with the version > that changed behaviour, shouldn't it? > > > Regards, > > Thomas Orgis > Well we did document it in NEWS as seen in: https://git.sv.gnu.org/cgit/coreutils.git/commit/?id=v8.27-42-gce0415f I still regard tail being more responsive to closed output being an improvement, and the more general solution, however it was a bit terse and broached as only an improvement. I pushed the following change to expand on the info: https://git.sv.gnu.org/cgit/coreutils.git/commit/?id=22424dd Marking this as done. thanks, Pádraig From unknown Mon Jun 23 18:31:57 2025 Received: (at fakecontrol) by fakecontrolmessage; To: internal_control@debbugs.gnu.org From: Debbugs Internal Request Subject: Internal Control Message-Id: bug archived. Date: Sat, 19 May 2018 11:24:06 +0000 User-Agent: Fakemail v42.6.9 # This is a fake control message. # # The action: # bug archived. thanks # This fakemail brought to you by your local debbugs # administrator