From owner-freebsd-hackers  Sun Jun  3 21:41:36 2001
Delivered-To: freebsd-hackers@freebsd.org
Received: from phaidor.thuvia.org (thuvia.demon.co.uk [193.237.34.248])
	by hub.freebsd.org (Postfix) with ESMTP id 4952737B401
	for <hackers@freebsd.org>; Sun,  3 Jun 2001 21:41:32 -0700 (PDT)
	(envelope-from mark@thuvia.demon.co.uk)
Received: from dotar-sojat.thuvia.org (dotar-sojat.thuvia.org [10.0.0.4])
	by phaidor.thuvia.org (8.11.3/8.11.3) with ESMTP id f544fRm00449;
	Mon, 4 Jun 2001 05:41:27 +0100 (BST)
	(envelope-from mark@dotar-sojat.thuvia.org)
Received: (from mark@localhost)
	by dotar-sojat.thuvia.org (8.11.3/8.11.3) id f544fOF58859;
	Mon, 4 Jun 2001 05:41:24 +0100 (BST)
	(envelope-from mark)
Date: Mon, 4 Jun 2001 05:41:24 +0100 (BST)
From: Mark Valentine <mark@thuvia.demon.co.uk>
Message-Id: <200106040441.f544fOF58859@dotar-sojat.thuvia.org>
In-Reply-To: "Andrew Reilly"'s message of Jun  4,  1:51pm
X-Mailer: Mail User's Shell (7.2.6 beta(5) 10/07/98)
To: "Andrew Reilly" <areilly@bigpond.net.au>
Subject: Re: Fixing documented bug in env(1)
Cc: Peter Seebach <seebs@plethora.net>, hackers@freebsd.org
Sender: owner-freebsd-hackers@FreeBSD.ORG
Precedence: bulk
List-ID: <freebsd-hackers.FreeBSD.ORG>
List-Archive: <http://docs.freebsd.org/mail/> (Web Archive)
List-Help: <mailto:majordomo?subject=help> (List Instructions)
List-Subscribe: <mailto:majordomo?subject=subscribe%20freebsd-hackers>
List-Unsubscribe: <mailto:majordomo?subject=unsubscribe%20freebsd-hackers>
X-Loop: FreeBSD.ORG

> From: "Andrew Reilly" <areilly@bigpond.net.au>
> Date: Mon 4 Jun, 2001
> Subject: Re: Fixing documented bug in env(1)

> > By the way, who uses env(1) anyway?  In the past twenty years, I've only
> > ever used it as shorthand for printenv(1).  What's this csh(1) thing?  :-)
> 
> How else do you throw away your environment, to make sure that
> daemons that you start with sudo don't do anything silly?
> 
> env - PATH=$PATH dhclient ed0

Using env(1) without any assumtion about command line assignment parsing
purely as an illustration:

    $ env - sh -c "PATH=$PATH dhclient ed0"

I'd probably wrap thus up in a script (or external program for ease of
use by various shells) - the semantics are subtly different from env(1):

    $ clearenv() { env - sh -c "$*"; }	# cheap and nasty to illustrate
    $ clearenv PATH=$PATH dhclient ed0

Making clearenv(1) an external program (which doesn't itself parse command
line variable assignments) may simplify quoting, and if ``dhclient'' were
instead a shell builtin such as echo(1), you'd need to avoid the shortcut
above, as in:

    $ clearenv "PATH=$PATH; export PATH; dhclient ed0"

		Cheers,

		Mark.

-- 
Mark Valentine, Thuvia Labs <mark@thuvia.co.uk>       <http://www.thuvia.co.uk>
"Tigers will do ANYTHING for a tuna fish sandwich."       Mark Valentine uses
"We're kind of stupid that way."   *munch* *munch*        and endorses FreeBSD
  -- <http://www.calvinandhobbes.com>                  <http://www.freebsd.org>

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