1.5 File descriptors
Handles that libpeios opens — tokens, registry keys, event streams — are raw int file descriptors, the same kind open() gives you. You close them with close(), poll them, and pass them across exec (or not) with the usual fd machinery.
They are created O_CLOEXEC by default: a handle does not leak across an exec unless you deliberately clear the flag with fcntl. This is the safe default for security-sensitive handles — a token or key fd will not silently end up in a child process you launch.