How to Send a Message to Logged Users in Linux Terminal?

If you are using a Linux system, there might be a possibility that you need to communicate with multiple logged-in users for various reasons, such as sending critical messages or notifications. Fortunately, there is a way to send messages to the users' terminals from the Linux command-line interface.

In this article, we will guide you through the steps on how to send messages to logged-in users in the Linux terminal and also cover the process of checking who is currently logged in, selecting the recipients of the message, and finally sending the message. By following these simple steps, you can communicate with other users on your system without requiring external messaging applications.

Step 1 Check Who's Logged In

To do this, we use the who command in the terminal. When you run this command, it will display a list of all the users who are currently logged in to the system.

who

The output will include the following information

• Login name The username of the logged-in user

• Terminal The device or terminal used by the user to log in

• Date and time The time when the user logged in

• IP address or hostname The IP address or hostname of the user's system

robert   pts/0        2024-01-15 10:30 (192.168.1.100)
smith    pts/1        2024-01-15 11:45 (192.168.1.101)
admin    tty1         2024-01-15 09:00

The who command provides a list of currently logged-in users, which is necessary information to choose who you want to send the message to.

Step 2 Choose Who to Send the Message to

Send to All Users (wall command)

If you wish to send a message to everyone who is currently using the Linux system, use the wall command. It sends your message to all logged-in users in your system.

wall Hello everyone!

This will send the message "Hello everyone!" to all users who are currently logged in to your system.

Send to a Specific User (write command)

To send a message directly to a specific user who is currently logged into your system, use the write command. Simply type the write command followed by the username of the intended recipient.

write robert Please come to my office

write: robert is logged in more than once; writing to pts/0
Please come to my office

This will send the message "Please come to my office" to the user with the username "robert" who is currently logged in to the system.

Send to Multiple Specific Users

You can also send messages to a group of users by combining commands. For example, to send a message to all users whose username starts with "j"

who | grep '^j' | cut -d' ' -f1 | xargs -I{} write {} Please come to my office

This command lists all logged-in users (who), filters usernames starting with "j" (grep), extracts the usernames (cut), and sends a message to each one (write).

Commands Overview

Important Considerations

• Message reception control Users can control whether they receive messages using mesg y (allow) or mesg n (block messages).

• Terminal requirement The recipient must be logged in and have an open terminal window to receive the message.

• Multiple sessions If a user is logged in multiple times, write will choose the terminal with the shortest idle time.

• Permissions Regular users can send messages to other users, but some systems may restrict this capability.

Conclusion

Sending messages to logged-in users in a Linux terminal is a quick and useful feature that allows system administrators and users to communicate efficiently. The who command helps identify logged-in users, while wall broadcasts to everyone and write targets specific users. This built-in messaging system is particularly valuable for system notifications and quick communication without external applications.