Received: (at 36148) by debbugs.gnu.org; 2 Jan 2020 09:37:28 +0000 From debbugs-submit-bounces <at> debbugs.gnu.org Thu Jan 02 04:37:28 2020 Received: from localhost ([127.0.0.1]:38189 helo=debbugs.gnu.org) by debbugs.gnu.org with esmtp (Exim 4.84_2) (envelope-from <debbugs-submit-bounces <at> debbugs.gnu.org>) id 1imwv2-0001gB-Ih for submit <at> debbugs.gnu.org; Thu, 02 Jan 2020 04:37:28 -0500 Received: from zimbra.cs.ucla.edu ([131.179.128.68]:48218) by debbugs.gnu.org with esmtp (Exim 4.84_2) (envelope-from <eggert@HIDDEN>) id 1imwv1-0001fx-HD for 36148 <at> debbugs.gnu.org; Thu, 02 Jan 2020 04:37:27 -0500 Received: from localhost (localhost [127.0.0.1]) by zimbra.cs.ucla.edu (Postfix) with ESMTP id F3B85160017; Thu, 2 Jan 2020 01:37:21 -0800 (PST) Received: from zimbra.cs.ucla.edu ([127.0.0.1]) by localhost (zimbra.cs.ucla.edu [127.0.0.1]) (amavisd-new, port 10032) with ESMTP id 2hQvgPSBW9BX; Thu, 2 Jan 2020 01:37:21 -0800 (PST) Received: from localhost (localhost [127.0.0.1]) by zimbra.cs.ucla.edu (Postfix) with ESMTP id 28C5C160054; Thu, 2 Jan 2020 01:37:21 -0800 (PST) X-Virus-Scanned: amavisd-new at zimbra.cs.ucla.edu Received: from zimbra.cs.ucla.edu ([127.0.0.1]) by localhost (zimbra.cs.ucla.edu [127.0.0.1]) (amavisd-new, port 10026) with ESMTP id 0R1K6kuUYD7Y; Thu, 2 Jan 2020 01:37:21 -0800 (PST) Received: from [192.168.1.9] (cpe-23-242-74-103.socal.res.rr.com [23.242.74.103]) by zimbra.cs.ucla.edu (Postfix) with ESMTPSA id F256C160017; Thu, 2 Jan 2020 01:37:20 -0800 (PST) To: g1pi@HIDDEN From: Paul Eggert <eggert@HIDDEN> Subject: Re: inconsistent behaviour with anchored regex containing back-references Organization: UCLA Computer Science Department Message-ID: <1ded0af3-1c7d-9386-0ccb-dc75527c83de@HIDDEN> Date: Thu, 2 Jan 2020 01:37:20 -0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.2.2 MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-Spam-Score: -2.3 (--) X-Debbugs-Envelope-To: 36148 Cc: 36148 <at> debbugs.gnu.org X-BeenThere: debbugs-submit <at> debbugs.gnu.org X-Mailman-Version: 2.1.18 Precedence: list List-Id: <debbugs-submit.debbugs.gnu.org> List-Unsubscribe: <https://debbugs.gnu.org/cgi-bin/mailman/options/debbugs-submit>, <mailto:debbugs-submit-request <at> debbugs.gnu.org?subject=unsubscribe> List-Archive: <https://debbugs.gnu.org/cgi-bin/mailman/private/debbugs-submit/> List-Post: <mailto:debbugs-submit <at> debbugs.gnu.org> List-Help: <mailto:debbugs-submit-request <at> debbugs.gnu.org?subject=help> List-Subscribe: <https://debbugs.gnu.org/cgi-bin/mailman/listinfo/debbugs-submit>, <mailto:debbugs-submit-request <at> debbugs.gnu.org?subject=subscribe> Errors-To: debbugs-submit-bounces <at> debbugs.gnu.org Sender: "Debbugs-submit" <debbugs-submit-bounces <at> debbugs.gnu.org> X-Spam-Score: -3.3 (---) Yes, back-references don't work very well. This looks to be the same bug as Bug#26864 <https://bugs.gnu.org/26864> so I have merged the two bug reports.
bug-grep@HIDDEN:bug#36148; Package grep.
Full text available.Paul Eggert <eggert@HIDDEN>
to control <at> debbugs.gnu.org.
Full text available.Received: (at submit) by debbugs.gnu.org; 9 Jun 2019 15:29:23 +0000 From debbugs-submit-bounces <at> debbugs.gnu.org Sun Jun 09 11:29:23 2019 Received: from localhost ([127.0.0.1]:55213 helo=debbugs.gnu.org) by debbugs.gnu.org with esmtp (Exim 4.84_2) (envelope-from <debbugs-submit-bounces <at> debbugs.gnu.org>) id 1hZzl4-0001d7-51 for submit <at> debbugs.gnu.org; Sun, 09 Jun 2019 11:29:22 -0400 Received: from lists.gnu.org ([209.51.188.17]:46497) by debbugs.gnu.org with esmtp (Exim 4.84_2) (envelope-from <g1pi@HIDDEN>) id 1hZskq-0005MQ-82 for submit <at> debbugs.gnu.org; Sun, 09 Jun 2019 04:00:40 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:50605) by lists.gnu.org with esmtp (Exim 4.86_2) (envelope-from <g1pi@HIDDEN>) id 1hZskp-0006r5-0r for bug-grep@HIDDEN; Sun, 09 Jun 2019 04:00:40 -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,FREEMAIL_FROM, RCVD_IN_DNSWL_NONE,URIBL_BLOCKED autolearn=disabled version=3.3.2 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from <g1pi@HIDDEN>) id 1hZsko-0001Y5-45 for bug-grep@HIDDEN; Sun, 09 Jun 2019 04:00:38 -0400 Received: from smtp-36.italiaonline.it ([213.209.10.36]:57428 helo=libero.it) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from <g1pi@HIDDEN>) id 1hZskn-0001XG-QF for bug-grep@HIDDEN; Sun, 09 Jun 2019 04:00:38 -0400 Received: from localhost ([151.15.190.244]) by smtp-36.iol.local with ESMTPA id Zskihv3g5GqCXZskihWEr1; Sun, 09 Jun 2019 10:00:33 +0200 x-libjamoibt: 1601 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=libero.it; s=s2014; t=1560067235; bh=EvO9LLiSiuysn1kOtgGCjdtZoOm+/O2/4ZuJB9wQwLQ=; h=Date:From:To:Subject; b=PEz19Moxv242HiAoMWxVVCas52bIY9fxtlFGy4VwBHJgKTGXsJU33vZ2rxza0kS48 VdIprLIftV7CC2E7mrLrlxHOU9M1K6t2RsQmXnQatpUEOJzN7PG2de2atsQU0Z5v6C Mv9c+qQAanSa2fk3/aT2ZCpzT4a270ab/wAKlE3a0V8wV7ddCX3ZQTfTzzEer4EuIi LP92AXyQQZF2rf6hcHiiC7cTHnmzLwARTjCDCwrUA4vQJlRyzHkSKENUAgYGSR7qhX LHszPSXK06RLsb86GbWrxux9zk1NSga8LSo5wXDrUYghoYa2X7a3/COLk2f1Ax5QeC WYcmg5ZXP3R1A== X-CNFS-Analysis: v=2.3 cv=IofPj43g c=1 sm=1 tr=0 a=XzvzAlnx5skC+0spddO+ig==:117 a=XzvzAlnx5skC+0spddO+ig==:17 a=kj9zAlcOel0A:10 a=4TDtqyubXOBDjDHEGnMA:9 a=CjuIK1q_8ugA:10 Date: Sun, 9 Jun 2019 10:00:24 +0200 From: g1pi@HIDDEN To: bug-grep@HIDDEN Subject: inconsistent behaviour with anchored regex containing back-references Message-ID: <20190609080024.sywtiytvlajpd4ko@moon> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: NeoMutt/20170113 (1.7.2) X-CMAE-Envelope: MS4wfIHarwt+9ZFwfqtR4uprOd4gs68SFi4Ny9QRG1tUgtM+DfFS5SPcAuntZGdSlEKDTosd1pNvbsPOzUKwnv7h3m9lsHYFCRMNX1qt9RZoiZeLPtJ/wZpX W82IHsDO0bu5UJrK//L9WcTwBA7qUQVOvpCz3lln5hSP1goO50KBIVB9FHBH+16hrzdTbsKTmswu6w== X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] X-Received-From: 213.209.10.36 X-Spam-Score: -1.4 (-) X-Debbugs-Envelope-To: submit X-Mailman-Approved-At: Sun, 09 Jun 2019 11:29:20 -0400 X-BeenThere: debbugs-submit <at> debbugs.gnu.org X-Mailman-Version: 2.1.18 Precedence: list List-Id: <debbugs-submit.debbugs.gnu.org> List-Unsubscribe: <https://debbugs.gnu.org/cgi-bin/mailman/options/debbugs-submit>, <mailto:debbugs-submit-request <at> debbugs.gnu.org?subject=unsubscribe> List-Archive: <https://debbugs.gnu.org/cgi-bin/mailman/private/debbugs-submit/> List-Post: <mailto:debbugs-submit <at> debbugs.gnu.org> List-Help: <mailto:debbugs-submit-request <at> debbugs.gnu.org?subject=help> List-Subscribe: <https://debbugs.gnu.org/cgi-bin/mailman/listinfo/debbugs-submit>, <mailto:debbugs-submit-request <at> debbugs.gnu.org?subject=subscribe> Errors-To: debbugs-submit-bounces <at> debbugs.gnu.org Sender: "Debbugs-submit" <debbugs-submit-bounces <at> debbugs.gnu.org> X-Spam-Score: -2.4 (--) There seems to be a problem with beginning/end-of-line anchors in regex containing back-references: $ grep -V | head -1 grep (GNU grep) 3.1 $ cat words ana deed ill stats Using -x to match whole line works: $ egrep -x '(.?)(.?).?\2\1' words ana deed stats Using explicit anchors emits false positives: $ egrep '^(.?)(.?).?\2\1$' words ana deed ill <<< stats On the other hand, colouring the output shows that grep somewhat knows its mistake: $ egrep --color '^(.?)(.?).?\2\1$' words ana (coloured) deed (coloured) ill stats (coloured)
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Full text available.bug-grep@HIDDEN:bug#36148; Package grep.
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