Linux Shell Scripting Cookbook - Third Edition

Sending a message to all users

The wall (WriteALL) command broadcasts a message to all the users and terminal sessions:

    $ cat message | wall

Or:

    $ wall < message
    Broadcast Message from slynux@slynux-laptop
            (/dev/pts/1) at 12:54 ...

    This is a message

The message header shows who sent the message: which user and which host.

The write, talk, and wall commands only deliver messages between users when the write message option is enabled. Messages from the root are displayed regardless of the write message option.

The message option is usually enabled. The mesg command will enable or disable the receiving of messages:

    # enable receiving messages
    $ mesg y
    # disable receiving messages
    $ mesg n