[aldto]

"write" was used to DM a person. And "mesg" was used to enable/disable messages from being displayed if you didn't want to be disturbed. I used this a lot earlier in my career. Later came "talk" which gave a fancy split screen chat session.

[ajross]

> "write" was used to DM a person.

Notably, it did so by literally opening up the tty associated with the user's session and spitting bytes directly at it. It was a different world back then.

[kps]

`stty 0 </dev/ttyxx` was briefly popular when I was in school (although setting an incorrect but nonzero baud rate would probably have been more annoying).