# Findout who is logged on $ who su pts/0 2019-05-14 08:15 (172.16.11.44) jack pts/1 2019-05-14 09:47 (172.16.11.44) # Broadcast a message $ wall "System will go down in a minute!" Broadcast message from su@hweb (pts/0) (Tue May 14 09:48:18 2019): System will go down in a minute! # Broadcast a message, but do not display the banner (available only to root) wall -n "System will go down in a minute!" System will go down in a minute! # Send message to a specific user $ write jack pts/1