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From: Joe Perches <joe@perches.com>
To: Andrew Morton <akpm@linux-foundation.org>,
	Stephen Rothwell <sfr@canb.auug.org.au>
Cc: Masahiro Yamada <yamada.masahiro@socionext.com>,
	Randy Dunlap <rdunlap@infradead.org>,
	Mark Brown <broonie@kernel.org>,
	 linux-fsdevel@vger.kernel.org,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	linux-mm@kvack.org,
	Linux-Next Mailing List <linux-next@vger.kernel.org>,
	mhocko@suse.cz, mm-commits@vger.kernel.org,
	 Michal Wajdeczko <michal.wajdeczko@intel.com>,
	Daniel Vetter <daniel.vetter@ffwll.ch>,
	Jani Nikula <jani.nikula@linux.intel.com>,
	Joonas Lahtinen <joonas.lahtinen@linux.intel.com>,
	 Rodrigo Vivi <rodrigo.vivi@intel.com>,
	Intel Graphics <intel-gfx@lists.freedesktop.org>,
	DRI <dri-devel@lists.freedesktop.org>,
	Chris Wilson <chris@chris-wilson.co.uk>
Subject: Re: mmotm 2019-07-04-15-01 uploaded (gpu/drm/i915/oa/)
Date: Thu, 04 Jul 2019 22:22:41 -0700	[thread overview]
Message-ID: <5f4680cce78573ecfbbdc0dfca489710581b966f.camel@perches.com> (raw)
In-Reply-To: <20190704220931.f1bd2462907901f9e7aca686@linux-foundation.org>

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



  reply	other threads:[~2019-07-05  5:22 UTC|newest]

Thread overview: 14+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-07-04 22:01 mmotm 2019-07-04-15-01 uploaded akpm
2019-07-05  1:09 ` mmotm 2019-07-04-15-01 uploaded (gpu/drm/i915/oa/) Randy Dunlap
2019-07-05  1:19   ` Randy Dunlap
2019-07-05  3:05   ` Masahiro Yamada
2019-07-05  3:09     ` Masahiro Yamada
2019-07-05  3:23       ` Randy Dunlap
2019-07-05  3:44         ` Masahiro Yamada
2019-07-05  4:09           ` Randy Dunlap
2019-07-31 13:21           ` Jani Nikula
2019-07-05  3:14     ` Stephen Rothwell
2019-07-05  5:09       ` Andrew Morton
2019-07-05  5:22         ` Joe Perches [this message]
2019-07-05  5:29           ` Andrew Morton
2019-07-05  3:01 ` mmotm 2019-07-04-15-01 uploaded (mm/vmscan.c) Randy Dunlap

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