From: Eric Blake <eblake@redhat.com>
To: chet.ramey@case.edu
Cc: linux-fsdevel@vger.kernel.org, sukadev@linux.vnet.ibm.com,
bug-bash@gnu.org, chet@po.cwru.edu
Subject: Re: bash: Correct usage of F_SETFD
Date: Mon, 22 Nov 2010 15:27:06 -0700 [thread overview]
Message-ID: <4CEAEE3A.4090004@redhat.com> (raw)
In-Reply-To: <101122221640.AA32947.SM@caleb.INS.CWRU.Edu>
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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.
--
Eric Blake eblake@redhat.com +1-801-349-2682
Libvirt virtualization library http://libvirt.org
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next prev parent reply other threads:[~2010-11-22 22:27 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 [this message]
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
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