wall - is used to display a message on the terminals of all logged-in users.

syntax $ wall [OPTIONS] [<FILE>|<MESSAGE>]

To display a message on the terminals of all logged-in users $ wall "The system will be rebooted in 20 minutes."

To suppress the banner and show only the text to the logged-in users $ wall -n "The system will be rebooted in 20 minutes."

To write multi-line messages $ wall

To pipe the output of another command to wall $ echo "The system will be rebooted in 20 minutes. \nPlease save your work." | wall

To broadcast a message from a file $ wall message_from_file.txt

To broadcast a message to a group $ wall -g devops "The system will be rebooted in 20 minutes."

regards, T.Dhanasekar