Date: Tue, 6 Aug 2002 13:52:40 -0500 From: Chris Costello <chris@FreeBSD.org> To: Christian Weisgerber <naddy@mips.inka.de> Cc: freebsd-current@freebsd.org Subject: Re: devfs, fdescfs: /dev/fd problems Message-ID: <20020806185240.GA3138@holly.calldei.com> In-Reply-To: <aim5ad$1tpa$1@kemoauc.mips.inka.de> References: <aim5ad$1tpa$1@kemoauc.mips.inka.de>
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On Monday, August 05, 2002, Christian Weisgerber wrote:
> Now let's try a program that lists the directory entries under
> [devfs] /dev/fd:
>
> $ ./t <( : )
> 0
> 1
> 2
> Listing the entries under [fdescfs] /dev/fd gives something of a surprise:
>
> $ ./t <( : )
> 0
> 1
> 2
> 3
>
> The descriptor used by readdir() is there, but the pipe on 63 is
> still missing, although open()ing it obviously works.
I can't explain why there's even a pipe open on fd #63, but
the reason you're only going to see 0, 1 and 2 is because that's
just how devfs's implementation of /dev/fd works. The last time
we (phk and I) looked at duplicating the fdescfs code in devfs it
was obvious it would require ugly hacks to get it to work, so it
was decided that devfs would only provide support for
/dev/fd/[0-2] so we can have /dev/std{in,out,err} as symlinks to
them. fdescfs (should) just export the calling process's file
table as a set of vnodes.
--
Chris Costello <chris@FreeBSD.org>
FreeBSD Project http://www.FreeBSD.org/
TrustedBSD Project http://www.TrustedBSD.org/
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