How exactly is cp not portable? Whatever behaviour you’re describing is not how POSIX mandates cp to work. In fact you can do this with busybox too. cp will o

How exactly is cp not portable? Whatever behaviour you’re describing is not how POSIX mandates cp to work. In fact you can do this with busybox too. cp will open("/dev/sda", O_WRONLY | O_TRUNC) and simply start writing to that file descriptor.