Date: Tue, 03 Feb 2004 16:54:18 +0000 From: Peter Edwards <peter.edwards@openet-telecom.com> To: =?ISO-8859-1?Q?Dag-Erling_Sm=F8rgrav?= <des@des.no> Cc: current@FreeBSD.org Subject: Re: Coalescing pipe allocation Message-ID: <401FD23A.9070407@openet-telecom.com> In-Reply-To: <xzpektc6rwo.fsf@dwp.des.no> References: <Pine.NEB.3.96L.1040131234955.17012E-100000@fledge.watson.org> <401FCCBE.2010008@openet-telecom.com> <xzpektc6rwo.fsf@dwp.des.no>
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Dag-Erling Smørgrav wrote:
>Peter Edwards <peter.edwards@openet-telecom.com> writes:
>
>
>>How would one "shut down" one direction of the pipe and still maintain
>>the other? I don't know how I can signal my intention not to read or
>>write to the end I leave open...
>>
>>
>
>man 2 shutdown
>
>
Shutdown requires a socket, and won't play with pipes:
$ cat t.c
#include <sys/types.h>
#include <sys/socket.h>
#include <err.h>
#include <unistd.h>
int
main()
{
int p[2];
if (pipe(p) == -1)
err(-1, "pipe");
if (shutdown(p[0], SHUT_RD) == -1)
err(-1, "shutdown");
return 0;
}
$ cc -o t ./t.c
$ ./t
./t: shutdown: Socket operation on non-socket
$
>
>
>>Is this portability issue so ridiculously out of date that the comment
>>in the pipe(2) manpage should be removed, or at least toned down?
>>
>>
>
>No, POSIX only guarantees the traditional behaviour. Bi-directional
>pipes are a non-portable BSDism.
>
>
>
>> It
>>seems silly to incur the costs of implementation you've mentioned and
>>then recommend that the feature not be used.
>>
>>
>
>It can still be useful for programs in the base system, which do not
>need to be unconditionally portable to non-BSD systems.
>
>
Fair 'nuff.
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