Date: Mon, 6 Sep 1999 10:57:50 -0400 (EDT) From: Zhihui Zhang <zzhang@cs.binghamton.edu> To: Alex Povolotsky <tarkhil@asteroid.svib.ru> Cc: stable@FreeBSD.ORG, hackers@FreeBSD.ORG Subject: Re: Problems with FIFO open in non-blocking mode? Message-ID: <Pine.GSO.3.96.990906105500.13356A-100000@sol.cs.binghamton.edu> In-Reply-To: <199909060547.JAA29146@shuttle.svib.ru>
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On Mon, 6 Sep 1999, Alex Povolotsky wrote:
> Hello!
>
> The following program
>
> #include <stdio.h>
> #include <fcntl.h>
>
> main() {
> int control;
> if ((control = open("STATUS",O_WRONLY|O_NONBLOCK))<0) {
> perror("Could not open STATUS ");
> exit(1);
> }
> printf("STATUS ready\n");
> close(control);
> return(0);
> }
>
> fails to run (STATUS is pre-created FIFO file) with error "Device not
> configured", which seems kinda odd for me.
>
> However, when FIFO is opened with O_RDWR and O_NONBLOCK, every attempt
> to select(2) its handler for writing doesn't wait until someone opens
> FIFO for reading, but instead FIFO is ready to write at every select.
>
> Is it a bug or a feature?
>
I answered a similar question some time ago. You can search the mailing
list archive for this. Basically, you need to read the "Advanced Unix
Programming Environment" by Stevens. I can not remember every details
right now. The "device not configured" error is expected.
-Zhihui
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