@JdeBP @joel My first test of "is it real vi" is to try open mode¹ :open It's like normal-mode, usually for use on a hardcopy output device but with more interactivity than ex(1). Pretty much none of the modern vi clones implement this functionality (or they overload :open to mean something else). ⸻ ¹ https://pubs.opengroup.org/onlinepubs/9699919799/utilities/ex.html#tag_20_40_13_29