You can send a message to an individual FreeBSD user logged into system using the write command. Typically writing a short message to an Individual user is main usage.

1) Use write command as follows
$ write user-name
Your message
Your message
…
When the message is complete, press Control-D

2) Here is an example of a message:
$ write joy
Do not use IRC in C Lab session.

3) Following message will be displayed on joy’s terminal:
Message from root@fbsd.test.com on ttyp0 at 13:24 …
Do not use IRC in C Lab session.