That's the way it's supposed to be, in the theory. But because this API requires extra effort to use, and by default FDs are inherited, in practice most of the

That's the way it's supposed to be, in the theory. But because this API requires extra effort to use, and by default FDs are inherited, in practice most of the time it is not intentional. The correct design would be to explicitly whitelist the FDs that the child process will inherit. This is exactly what Python does - its standard API to spawn subprocesses not only has close_fds=True set by default, it also has pass_fds where you list the ones that should not be closed. FWIW I also don't see why the parent should care if the child closes its inherited descriptors, since it retains its own copy which remains open.