Re: [OT] Interrupting select

From: Peter T. Breuer (ptb@it.uc3m.es)
Date: Wed May 02 2001 - 18:44:35 EST


"Mark Hahn wrote:"
> > while (1) {
> > int res = select(n,rfds,wfds,efds,&timeout);
> > if (res > 0)
> > return res; // data or error is expected
> > if (res == 0) {
> > return -ETIME; // timeo in select
> > }
> > }
> >
> > A resounding "no". kill -9 hurts it but it's invulnerable to everything
> > else.
>
> um, shouldn't you be testing for res==-1, as well?
> specifically that condition and errno==EINTR is how I'd expect
> signals to effect the loop...

Possibly .. if so that's the answer. But the man page doesn't say so:

          tained in the descriptor sets, which may be zero if the
          timeout expires before anything interesting happens. On
          error, -1 is returned, and errno is set appropriately;

I assumed that "error" is something like trying to watch for a
negative number or zero descriptors, or having a fd_set that doesn't
contain open fd's. The reason I assumed that is because EINTR is not
listed as a possible:

    
ERRORS
       EBADF An invalid file descriptor was given in one of the
               sets.
       EINTR A non blocked signal was caught.
       EINVAL n is negative.
       ENOMEM select was unable to allocate memory for internal
               tables.

But I'm willing to give it a try! Thanks!

Now back to your regularly scheduled programs ...

Peter

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