How to send a message to other logged in users

If you are root you can easily get into contact with all logged in users on a system. Some examples follow which explain how to send a message to all users, or just print information about all logged in users.

First become root if you are not already. Then print information about the other users with the w command. This will print their names along with their virtual terminal, login time and their current process.

If you want to find out your own virtual terminal just type

tty

Now, to broadcast a short message to all logged in users the wall command can be used:

echo "a message" | wall

For a longer text it might be better to just type wall and press enter, write the message and send it with ctrl-d:

wall
This is a message
with several lines
[ctrl-d]

Note, that a user can prevent the display of messages from other (non-root) users with

mesg n

or reactivate it with

mesg y