Ctrl-D is maybe the hardest part of TTYs to emulate if you want to bypass the accumulated legacy of the kernel-level TTY device API. It's very easy to make read

Ctrl-D is maybe the hardest part of TTYs to emulate if you want to bypass the accumulated legacy of the kernel-level TTY device API. It's very easy to make read() return 0 forever, but it's next-to-impossible to make read() return 0 exactly once, except for TTY slaves.