> Guido van Rossum added the comment:
>
>> Apparently, the stdout pipe was closed by the parent process
>
> Could it be that selecting for *read* on the *write* end of a pipe is
> always ready?

That's exactly what I was thinking when I read the code below: that's
definitely a possibility on AIX.

> In _UnixWritePipeTransport there's a read handler that
> immediately closes the pipe as soon as it called. I vaguely remember a
> discussion on python-tulip that this might be Linux-specific behavior. (The
> reason is that otherwise you can't find out whether the other end was
> closed unless you attempt to write to the pipe.)

Normally, if the pipe is closed, it should be reported by a POLLHUP/write ready.
Then you only consider it closed when write fails with EPIPE.