pub fn fchmod<Fd: AsFd>(fd: &Fd, mode: Mode) -> io::Result<()>
The portability is definied by: #[cfg(not(target_os = "wasi"))]
Documentation
fchmod(fd)—Sets open file or directory permissions.
Note that this implementation does not support O_PATH file descriptors,
even on platforms where the host libc emulates it.
References