From owner-freebsd-questions  Sun Jan 28 13:23: 1 2001
Delivered-To: freebsd-questions@freebsd.org
Received: from post.mail.nl.demon.net (post-10.mail.nl.demon.net [194.159.73.20])
	by hub.freebsd.org (Postfix) with ESMTP
	id 42DCA37B400; Sun, 28 Jan 2001 13:22:36 -0800 (PST)
Received: from [212.238.77.116] (helo=gateway.raggedclown.intra)
	by post.mail.nl.demon.net with smtp (Exim 3.14 #2)
	id 14MzHO-0007Zb-00; Sun, 28 Jan 2001 21:22:34 +0000
Received: by buffy.raggedclown.net (Postfix on SuSE Linux 7.0 (i386), from userid 500)
	id F417312D3D; Sun, 28 Jan 2001 22:18:01 +0100 (CET)
Date: Sun, 28 Jan 2001 22:18:01 +0100
From: Cliff Sarginson <cliff@raggedclown.net>
To: "Justin W. Pauler" <jwpauler@jwpages.com>
Cc: freebsd-questions@FreeBSD.ORG, freebsd-stable@FreeBSD.ORG
Subject: Re: tail
Message-ID: <20010128221801.A2923@raggedclown.net>
References: <01012813255100.83352@gateway.drnet.fais.net>
Mime-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
User-Agent: Mutt/1.2.5i
In-Reply-To: <01012813255100.83352@gateway.drnet.fais.net>; from jwpauler@jwpages.com on Sun, Jan 28, 2001 at 01:25:51PM -0600
Sender: owner-freebsd-questions@FreeBSD.ORG
Precedence: bulk
X-Loop: FreeBSD.ORG

On Sun, Jan 28, 2001 at 01:25:51PM -0600, Justin W. Pauler wrote:
> I am not sure if this is a command, but if not, I think it would be useful. I 
> have often needed to watch output from different commands like df, but I have 
> to continously run the command to get the latest amount. I was thinking, why 
> couldn't tail do that? Since it can watch files for changes and display 
> those, why not for a command?
> 
> I tried tail -f |df -h and could not get it to update. I would appreciate 
> your thoughts.
> 
> I am also cc'ing this to stable in cause it is a bug/feature...

Mmm.. methinks you are confused !
The command as you tyoed it will have tail read it;s standard input,
the terminal, and pipe it's output into df. Since df is not a filter
it will ignore it. If it would work then you would need to change
it around to "df | tail -f".
However df will only execute once, so that won;t do what you want.
To repeatedly execute a command put it in a loop:

while :
do df
done

If you want it to wait a while put a sleep in it, to space it
out put an echo..e.g.

while :
do df
sleep 2
echo
done

However, on Linux there is a program called "watch" that repeatedly
executes a command an displays it on the screen updating the
display "in place" .. so it does not scroll away. I am sure there
must be a similar program on BSD (I would like to know as well!)
but the program named "watch" on FBSD is something
different.

Cliff




To Unsubscribe: send mail to majordomo@FreeBSD.org
with "unsubscribe freebsd-questions" in the body of the message