write
Write a message on the terminal of a specified logged in user (ctrl-C to stop writing messages).
Use the who command to find out all terminal_ids of all active users active on the system. See also mesg.
More information: https://manned.org/write.
- Send a message to a given user on a given terminal ID:
write username terminal_id
- Send message to "testuser" on terminal
/dev/tty/5:
write testuser tty/5
- Send message to "johndoe" on pseudo terminal
/dev/pts/5:
write johndoe pts/5