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How to use wall command in linux

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Introduction

wall (an abbreviation of write to all) is a Unix command-line utility that displays the contents of a computer file or standard input to all logged-in users. It is typically used by root to send out shutting down message to all users just before poweroff.

wall command

You can use wall command to Broadcasting a Message with the syntax below:

wall [OPTIONS] [File]
OR
wall [OPTIONS] [Message]

NOTE: If no file is specified wall reads the message from the standard input.

  • You can do that with invoke the wall command with the message as the argument as shown below:
wall "Attention please, The system will be restarted in 1 hour."

The message will be broadcasted to the users currently logged in.

  • To show only the text you types and disappear the banner, invoke the command with the -n  or (–nobanner) option
wall --nobanner "Attention please, The system will be restarted in 1 hour."
  • If you want to write multi-line messages, invoke the wall command, it will wait for you to finish your lines then you should press Ctr+D to end it then it will broadcast the message
wall
  • Here is an example showing how to use the echo command with wall on pipe to broadcast a message
echo "Attention please, The system will be restarted in 1 hour." | wall
  • Also you can broadcast a Message From a File
wall Attention_message.txt

It will display all the content of the file in addition to the broadcast banner message of wall command

  • Finally you can Broadcast a Message to a Group

So to send a message only to members of a given group, run the command with the -g or –group option, followed by the group name.

wall -g Devlopers "The system will be restarted in 1 hour."

Conclusion

That’s it

We illustrated how to use wall command to display a file content or standard input to all logged-in users on the system.

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