How to use wall command.
wall is a command-line utility that displays a message on the terminals of all logged-in users. The messages can be either typed on the terminal or the contents of a file. wall stands for write all, to send a message only to a specific user use the write command.
Broadcasting a Message
The syntax for the wall command is as follows:
wall [OPTIONS] [<FILE>|<MESSAGE>]
If no file is specified wall reads the message from the standard input.
The most straightforward way to broadcast a message is to invoke the wall command with the message as the argument:
wall "The system will be restarted in 10 minutes."
Broadcast message from [email protected] (pts/0) (Sun Oct 4 19:22:07 2020): The system will be restarted in 10 minutes.
The message will be broadcasted to all users that are currently logged in.
To see all the logged-in users, run the w or who command.
To suppress the banner and show only the text you types to the logged-in users, invoke the command with the -n (--nobanner) option:
wall -n “The system will be restarted in 10 minutes.”
The system will be restarted in 10 minutes.
If you want to write multi-line messages, invoke the command without an argument:
wall
The wall command will wait for you to enter text. When you’re done typing the message, press Ctrl+D to end the program and broadcast the message.
You can also use the here-string redirection or pipe the output of another command to wall. Here is an example showing how to use the echo command to broadcast multi-line messages:
echo "The system will be restarted in 10 minutes. \nPlease save your work." | wall
Broadcasting a Message From a File
If you are regularly sending the same messages, you can write each one of them to a file, so that you don’t need to re-type the same text. wall reads from the file only when invoked as root.
To broadcast the contents of a file, invoke the wall command followed by the file name:
The system will be restarted in 10 minutes.
wall message1_file.txt
Broadcast message from [email protected] (pts/0) (Sun Oct 4 19:25:06 2020): The system will be restarted in 10 minutes.
Broadcasting a Message to a Group
To send a message only to members of a given group, run the command with the -g (--group) option, followed by the group name. For example, to write only on the terminals of the members of the “devs” group, you would run:
wall -g devs "The system will be restarted in 10 minutes."
The group can also be specified by its GID (group ID).
Conclusion
The wall command writes a message on the terminals of all currently logged-in users.
