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[216.40.44.113]) by mx.google.com with ESMTPS id v14si3542365qtv.201.2019.07.04.22.22.46 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 04 Jul 2019 22:22:46 -0700 (PDT) Received-SPF: neutral (google.com: 216.40.44.113 is neither permitted nor denied by best guess record for domain of joe@perches.com) client-ip=216.40.44.113; Authentication-Results: mx.google.com; spf=neutral (google.com: 216.40.44.113 is neither permitted nor denied by best guess record for domain of joe@perches.com) smtp.mailfrom=joe@perches.com Received: from filter.hostedemail.com (clb03-v110.bra.tucows.net [216.40.38.60]) by smtprelay07.hostedemail.com (Postfix) with ESMTP id 85F32181D3368; Fri, 5 Jul 2019 05:22:46 +0000 (UTC) X-Session-Marker: 6A6F6540706572636865732E636F6D X-HE-Tag: level75_17cfce2dff144 X-Filterd-Recvd-Size: 2521 Received: from XPS-9350 (cpe-23-242-196-136.socal.res.rr.com [23.242.196.136]) (Authenticated sender: joe@perches.com) by omf03.hostedemail.com (Postfix) with ESMTPA; Fri, 5 Jul 2019 05:22:43 +0000 (UTC) Message-ID: <5f4680cce78573ecfbbdc0dfca489710581b966f.camel@perches.com> Subject: Re: mmotm 2019-07-04-15-01 uploaded (gpu/drm/i915/oa/) From: Joe Perches To: Andrew Morton , Stephen Rothwell Cc: Masahiro Yamada , Randy Dunlap , Mark Brown , linux-fsdevel@vger.kernel.org, Linux Kernel Mailing List , linux-mm@kvack.org, Linux-Next Mailing List , mhocko@suse.cz, mm-commits@vger.kernel.org, Michal Wajdeczko , Daniel Vetter , Jani Nikula , Joonas Lahtinen , Rodrigo Vivi , Intel Graphics , DRI , Chris Wilson Date: Thu, 04 Jul 2019 22:22:41 -0700 In-Reply-To: <20190704220931.f1bd2462907901f9e7aca686@linux-foundation.org> References: <20190704220152.1bF4q6uyw%akpm@linux-foundation.org> <80bf2204-558a-6d3f-c493-bf17b891fc8a@infradead.org> <20190705131435.58c2be19@canb.auug.org.au> <20190704220931.f1bd2462907901f9e7aca686@linux-foundation.org> Content-Type: text/plain; charset="ISO-8859-1" User-Agent: Evolution 3.30.5-0ubuntu0.18.10.1 MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Thu, 2019-07-04 at 22:09 -0700, Andrew Morton wrote: > diff(1) doesn't seem to know how to handle a zero-length file. > > y:/home/akpm> mkdir foo > y:/home/akpm> cd foo > y:/home/akpm/foo> touch x > y:/home/akpm/foo> diff -uN x y > y:/home/akpm/foo> date > x > y:/home/akpm/foo> diff -uN x y > --- x 2019-07-04 21:58:37.815028211 -0700 > +++ y 1969-12-31 16:00:00.000000000 -0800 > @@ -1 +0,0 @@ > -Thu Jul 4 21:58:37 PDT 2019 > > So when comparing a zero-length file with a non-existent file, diff > produces no output. Why use the -N option ? $ diff --help [...] -N, --new-file treat absent files as empty otherwise $ cd $(mktemp -d -p .) $ touch x $ diff -u x y diff: y: No such file or directory