From owner-freebsd-questions@freebsd.org  Wed Sep 27 20:45:28 2017
Return-Path: <owner-freebsd-questions@freebsd.org>
Delivered-To: freebsd-questions@mailman.ysv.freebsd.org
Received: from mx1.freebsd.org (mx1.freebsd.org
 [IPv6:2001:1900:2254:206a::19:1])
 by mailman.ysv.freebsd.org (Postfix) with ESMTP id 77C6CE0ECE9
 for <freebsd-questions@mailman.ysv.freebsd.org>;
 Wed, 27 Sep 2017 20:45:28 +0000 (UTC)
 (envelope-from list@museum.rain.com)
Received: from g5.umpquanet.com (g5.umpquanet.com [98.158.10.79])
 (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits))
 (Client CN "g5.umpquanet.com",
 Issuer "Let's Encrypt Authority X3" (not verified))
 by mx1.freebsd.org (Postfix) with ESMTPS id 36A1512BF
 for <freebsd-questions@freebsd.org>; Wed, 27 Sep 2017 20:45:27 +0000 (UTC)
 (envelope-from list@museum.rain.com)
Received: from g5.umpquanet.com (localhost [127.0.0.1])
 by g5.umpquanet.com (8.15.2/8.15.2) with ESMTPS id v8RKjQSe078700
 (version=TLSv1.2 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=NO)
 for <freebsd-questions@freebsd.org>; Wed, 27 Sep 2017 13:45:27 -0700 (PDT)
 (envelope-from list@museum.rain.com)
Received: (from james@localhost)
 by g5.umpquanet.com (8.15.2/8.15.2/Submit) id v8RKjQiP078699
 for freebsd-questions@freebsd.org; Wed, 27 Sep 2017 13:45:26 -0700 (PDT)
 (envelope-from list@museum.rain.com)
X-Authentication-Warning: g5.umpquanet.com: james set sender to
 list@museum.rain.com using -f
Date: Wed, 27 Sep 2017 13:45:26 -0700
From: list@museum.rain.com
To: freebsd-questions@freebsd.org
Subject: Re: Possible bug in tail(1)
Message-ID: <20170927204526.GA78573@g5.umpquanet.com>
References: <20170927195828.GA77592@g5.umpquanet.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <20170927195828.GA77592@g5.umpquanet.com>
User-Agent: Mutt/1.8.3 (2017-05-23)
X-BeenThere: freebsd-questions@freebsd.org
X-Mailman-Version: 2.1.23
Precedence: list
List-Id: User questions <freebsd-questions.freebsd.org>
List-Unsubscribe: <https://lists.freebsd.org/mailman/options/freebsd-questions>, 
 <mailto:freebsd-questions-request@freebsd.org?subject=unsubscribe>
List-Archive: <http://lists.freebsd.org/pipermail/freebsd-questions/>
List-Post: <mailto:freebsd-questions@freebsd.org>
List-Help: <mailto:freebsd-questions-request@freebsd.org?subject=help>
List-Subscribe: <https://lists.freebsd.org/mailman/listinfo/freebsd-questions>, 
 <mailto:freebsd-questions-request@freebsd.org?subject=subscribe>
X-List-Received-Date: Wed, 27 Sep 2017 20:45:28 -0000

On Wed, Sep 27, 2017 at 12:58:28PM -0700, list@museum.rain.com wrote:
> #!/usr/bin/env bash
> 
> cat << EOF > foo
> 1
> 2
> 3
> 
> EOF
> 
> echo "--"
> cat foo
> echo "--"
> tail -r foo
> echo "--"
> tail -r foo | tail -r
> echo "--"


Here is a simpler test case:

$ printf '\n1\n' | tail -r