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}}