[erlang-questions] Using select in a Port

Michael Schreckenbauer <>
Fri Oct 19 15:45:17 CEST 2007

Hi Per,

Am Freitag, 19. Oktober 2007 schrieb Per Hedeland:
> Michael Schreckenbauer <> wrote:
> >This proceeds, if at least one(!) of the fds you gave won't block, when
> > you do a read on it. That could be stdin or any other.
> >
> >>      if FD_ISSET(0, &readfds) {
> >>        memset(buf, 0, BUFFER_SIZE);
> >>        read_cmd(buf, &size);
> >
> >Here you check the right fd, but read_cmd always uses stdin.
> >The nonblocking fd is 3, your file, as you can see in the debug output. So
> >read_cmd must fail. It needs an additional parameter holding the fd you
> > want to use.
> No, this is code is correct per se - if fd 0 is ready, he calls a
> function that reads only from fd 0, which is clearly OK. The other fd's
> are handled in note_read(), which isn't included in the mail but is
> where the debug output is produced. Regardless of that, select says that
> fd 0 *is* "ready" - the error is in assuming that this means that there
> is (some specific amount of) data to read.

yes, of course you're right. Must have been to early for me ;)

> --Per Hedeland


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