The essence of this tiny "interactive command line utility" is to capture user key strokes and redirect to a sub-process. So there gotta be a way to interrupt and exit the sub-process. "EOF" is just a convention. You can also get out of the sub-process with "Ctrl-D" like in Python shell.
Interactive editors like vi/emacs also need to flush the buffer and save the content to the file, but you have to type something, such as ":w" and "C-x C-s" (or use GUI).
If you want full automation without human input, I/O redirection is the way.
