From: Jamie Lokier <jamie@shareable.org>
To: Eric Blake <eblake@redhat.com>
Cc: chet.ramey@case.edu, sukadev@linux.vnet.ibm.com,
linux-fsdevel@vger.kernel.org, bug-bash@gnu.org,
chet@po.cwru.edu
Subject: Re: bash: Correct usage of F_SETFD
Date: Wed, 24 Nov 2010 01:17:16 +0000 [thread overview]
Message-ID: <20101124011716.GX22787@shareable.org> (raw)
In-Reply-To: <4CEAEE3A.4090004@redhat.com>
Eric Blake wrote:
> On 11/22/2010 03:16 PM, Chet Ramey wrote:
> >> include/filecntl.h in bash-4.1 has following:
> >>
> >> #define SET_CLOSE_ON_EXEC(fd) (fcntl ((fd), F_SETFD, FD_CLOEXEC))
> >>
> >> Is that really the correct/intended usage of F_SETFD ?
> >
> > F_SETFD Set the close-on-exec flag associated with fildes to
> > the low order bit of arg (0 or 1 as above).
> >
> >> If kernel ever adds a new flag to the fd, this would end up clearing the
> >> other new flag right ?
> >>
> >> Shouldn't bash use F_GETFD to get the current flags and set/clear just
> >> the FD_CLOEXEC bit ?
> >
> > I suppose it would matter if there are systems that have more than one
> > flag value.
>
> In practice, there aren't any such systems; but POSIX warns that current
> practice is no indicator of future systems, and that read-modify-write
> is the only way to use F_SETFD.
There are so many programs using F_SETFD the way Bash does, that it
would be quite brave (or stupid) to add another flag.
-- Jamie
prev parent reply other threads:[~2010-11-24 1:17 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-11-22 20:16 bash: Correct usage of F_SETFD Sukadev Bhattiprolu
2010-11-22 22:16 ` Chet Ramey
2010-11-22 22:27 ` Eric Blake
2010-11-23 0:04 ` Sukadev Bhattiprolu
2010-11-23 14:42 ` Matthew Wilcox
2010-11-23 14:51 ` Eric Blake
2010-11-23 17:51 ` Sukadev Bhattiprolu
2010-11-24 1:17 ` Jamie Lokier [this message]
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