Writes a message to all users that are logged in.
wall [ -a ] [ -g Group ][ Message ]
The wall command writes a message to all users that are logged in. If the Message parameter is not specified, the wall command reads the message from standard input until it reaches an end-of-file character. The message is then sent to all logged in users. The following heading precedes the message:
Broadcast message from user@node (tty) at hh:mm:ss ...
hh:mm:ss represents the hours, minutes, and seconds when the message was sent.
To override any protections set up by other users, you must operate with root user authority. Typically, the root user uses the wall command to warn all other users of an impending system shutdown.
Notes:
| -a | Performs the default operation. This flag is provided for System V compatibility. It broadcast messages to the console and pseudo-terminals. |
| -g Group | Broadcasts to a specified group only. |
| /dev/tty | Specifies a device. |
The mesg command, su command, write command.