Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Fri, 2 Nov 2001 14:53:30 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Fri, 2 Nov 2001 14:53:20 -0500 Received: from twilight.cs.hut.fi ([130.233.40.5]:16392 "EHLO twilight.cs.hut.fi") by vger.kernel.org with ESMTP id ; Fri, 2 Nov 2001 14:53:17 -0500 Date: Fri, 2 Nov 2001 21:53:13 +0200 From: Ville Herva To: Riley Williams Cc: Doug McNaught , Linux Kernel Subject: Re: Need blocking /dev/null Message-ID: <20011102215312.Q1504@niksula.cs.hut.fi> In-Reply-To:

Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.2.5i In-Reply-To: ; from rhw@MemAlpha.cx on Thu, Nov 01, 2001 at 11:51:39PM +0000 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Nov 01, 2001 at 11:51:39PM +0000, you [Riley Williams] claimed: (Piping only stderr to a program) > Also, even if it's true, is that also true with all other possible > shells? I think the point is it can be made to work in userland, not that a particular shell isn't able to do that. In fact, I'm a bit dissapointed that shells such as zsh and bash seem to lack an easy way to do that. But really, this is theoretical, I think nobody is really advocating getting rid of /dev/null and /dev/zero. > Redirecting to /dev/null is independant of the shells, but piping hacks > like that aren't. The way I see it piping is independent from shells just because it can be accomplished in userland using the present linux system calls. > So it should be deliberately written to write them out in an infinite > loop? Makes a bizarre sort of sense, but not something I would ever do. Why is that? I see nothing bizarre in that. > Also, as I've had pointed out to me, one sometimes needs to tell a > program to take input other than stdin from /dev/zero and that often > can't be done using pipes. The friend who pointed this out to me > recently had reason to do precicely this. The following isn't exactly > what he needed, but is similar... > > Q> ebcdic2ascii < /dev/ttyS1 | tr A-Z a-z | bindiff /dev/zero /dev/stdin Again, I think it can be done in userland. Some shells even give you convenient syntax for that. This works in zsh: head -2 <(yes) <(uname) ==> /proc/self/fd/11 <== y y ==> /proc/self/fd/12 <== Linux So you can pipe arbitrary program output as a filename argument. I guess you example could be written as ebcdic2ascii < /dev/ttyS1 | tr A-Z a-z | bindiff <(zerofill) /dev/stdin but I'm not sure since I have no idea your example does ;) ;). > > I'm still happy to keep /dev/null and /dev/zero. ;) > > So am I. -- v -- v@iki.fi - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/