Essential System Administration, 3rd Edition

Communicating with Users

The commands discussed in this section are simple and familiar to most Unix users. For this reason, they’re often overlooked in system administration discussions. However, I believe you’ll find them to be an indispensable part of your repertoire. One other important communications mechanism is electronic mail (see Chapter 9).

Sending a Message

A system administrator frequently needs to send a message to a user’s screen (or window). write is one way to do so:

$ write 
               username[tty]

where username indicates the user to whom you wish to send the message. If you want to write to a user who is logged in more than once, the tty argument may be used to select the appropriate terminal or window. You can find out where a user is logged in using the who command.

Once the write command is executed, communication is established between your terminal and the user’s terminal: lines that you type on your terminal will be transmitted to him. End your message with a CTRL-D. Thus, to send a message to user harvey for which no reply is needed, execute a command like this:

$ write harvey 
               The file you needed has been restored. 
               Additional lines of message text 
               ^D 

In some implementations (e.g., AIX, HP-UX and Tru64), write may also be used over a network by appending a hostname to the username. For example, the command below initiates a message to user chavez on the host named hamlet:

$ write chavez@hamlet

When available, the rwho command may be used to list all users on the local ...