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.

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 "jhondoe" on pseudo terminal "/dev/pts/5":

write {{jhondoe}} {{pts/5}}