Recipe: Sending messages to user terminals

wall
====
$ cat message | wall
OR
$ wall < message                                                                      
Broadcast Message from slynux@slynux-laptop                                    
        (/dev/pts/1) at 12:54 ...                                              
                                                                               
This is a message  



Enable messages
===============
$ mesg y

Disable messages
================
$ mesg n

Script
======
message_user.sh