On Fri, Oct 4, 2013 at 3:08 PM, Kunszt Árpád <
arpad.kun...@syrius-software.hu> wrote:
> On 2013. October 4. 14:51:00 Pierre Gaston wrote:
> > On Fri, Oct 4, 2013 at 2:20 PM, Kunszt Árpád
> ...
> >
> >
> > There is a race condition, you cannot know if echo will run before read.
>
> I see, and it's logical. But this stills confuses me.
>
> arpad@terminus ~ $ for(( i=0; i<10; i++ )); do echo -n "" | { sleep 1s;
> read -t 0; echo $?; } ; done | sort | uniq -c
> 10 0
>
> I expected that the read will return non-zero in this case. I think it
> returned with zero because the STDIN was still open. The docs said "read
> returns success if input is available on the specified file descriptor,
> failure otherwise". There wasn't any data on the file descriptor, it was
> just open.
>
> Am I still doing something wrong? Or I just misunderstanding the meaning
> of "input is available" term? I'm not a native English speaker (as you can
> se from my mails clearly).
>
> Thanks,
>
> Arpad Kunszt
>
>
Most probably read uses and does what the select() call does.
In my man select(2) I have:
"more precisely, to see if a read will not block; in particular, a
file descriptor is also ready on end-of-file"
and that's what your exemple does, echo opens stdin and then closes it and
read sees and end of file.
no worry about your english..
