[TUHS] Posix ed weirdness

[Clem Cole via TUHS]

Doug,

Do you know what later AT&T Summit versions did?  And/or SVID

Clem

On Mon, Dec 15, 2025 at 4:56 PM Douglas McIlroy via TUHS <tuhs at tuhs.org>
wrote:

> The ed j command joins a sequence of lines into one line and sets dot
> to the result. Thus
>      2,4j
> combines three lines and sets dot to 2. Naturally one expects
>      2,2j
> to make no visible change to the file, but to set dot to 2.
>
> Indeed, that's what v7 did. But Posix decrees that j "does nothing" in
> this case and leaves dot at the value it had before the command.
>
> Does anyone know why the Posix committee chose to break both the
> original behavior and  Kernighan's law: " 'Do nothing' gracefully"?
>
> Doug
>