What is wall command in linux

wall Command in Linux | Explained

Linux provides one of the best network interfaces with fantastic features, mainly through its terminal. One of their most valuable is the wall command, which sends a direct message or text from a file to all the users currently logged in. Only the superuser or admin can do this, and it is an excellent command to send the warning messages like “the server will restart in 10 minutes” or something like that.

This article will help users understand everything about the wall command of Linux, and we’ll use a few examples to elaborate on it more clearly. The content of the post is as follows:

That’s all from this guide!

What is the wall Command in Linux?

wall command, as discussed earlier, is used by the admin to send a text to all the logged-in users, and it only works with the terminal open, so you will not receive anything if the terminal is closed. There are a few variations, as below.

The syntax of the wall command is pretty much straightforward, like all other commands, as seen below.

wall [options] [message | file]

The Options supported by it are as follows:

Options	Function
-g or –group	To send the messages/file contents to a group of users.
-n or –nobanner	Used to remove the banner (unwanted or irrelevant text)
-t or –timeout	Sets the timeout in seconds.

For more details on the usage of the wall command, use the following command:

let’s practice this command in the upcoming command!

How to Use the wall Command in Linux?

This section lists examples of the wall command to send “wall” messages to other logged-in users. Before that, check the version of the wall command on your system via the below command:

Let’s start with the examples!

Example 1: Send a Simple Message (Without Options)

Here is how the admin or superuser can send a message to other users. An admin or a user who run this command won’t be able to see the displayed message, but other users who are on the same network can see it.

$ wall the message to be delivered

The message sent from itsL[email protected](admin) and all other users would see on their terminals are as follows.

Example 2: Send a Message From a File Using the wall Command

In some scenarios, any operation must be performed on the system frequently. To tackle this, a message text can be stored in a file, and the need to write the message again and again, is nullified. For instance, if a restart message is stored in a file, then the following syntax can be used to fetch and send the message:

The “path/of/the/file” represents the file from where the message is to be fetched. Let’s practice this!

In our case, we used the “cat” command first to print the content of the file, and then the file command was utilized to send the message:

We used the “cat command” to show the file contents as in the above image.

Other logged-in users would see the output like this on their terminal screen.

Example 3: Send a Message to a Specific Group Using the wall Command in Linux

Suppose there are two servers in your working environment, and one of them needs to restart. Each server has a group of users, and you need to send those users a warning message before rebooting the system. It can be done using the wall command in the following syntax.

The “editorial” is the group whose members will receive the message, as seen above.

Example 4: Suppress Banner in wall Command on Linux

As in the image below, you can see a lot of unwanted text known as a banner; it can be removed by adding “-n” to the wall Command.

The syntax of the wall command with “-n” is as follows.

And all the users would receive the messages from the admin or superuser just as intended.

That’s all from this guide!

Conclusion

The wall command, as the name directs, sends a message to all the currently logged-in users. This utility is mostly used by the network/system administrator to convey any warning or the action being performed on the server. This post has briefly demonstrated the working and usage of the wall command in Linux with the help of suitable examples.

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Linux wall command

On Unix-like operating systems, the wall command writes a message simultaneously to all other logged-in users.

This page covers the Linux version of wall.

Description

wall displays the contents of file or, by default, its standard input, on the terminals of all currently logged-in users. The command will cut any lines that are over 79 characters to new lines. Short lines are white space padded to have 79 characters. The command always puts carriage return and new line at the end of each line.

Only the super-user can write on the terminals of users who have chosen to deny messages or are using a program which automatically denies messages.

Reading from a file is refused when the invoker is not superuser and the program is suid or sgid.

Syntax

wall [-n] [-t TIMEOUT] [file]

Options

-n, —nobanner	Suppress banner
-t, —timeout TIMEOUT	Write timeout to terminals in seconds. TIMEOUT must be positive integer. Default value is 300 seconds, a legacy from time when people ran terminals over modem lines.
-V, —version	Display version information and exit.
-h, —help	Display a help message and exit.

Examples

Using the sudo command to run wall as the superuser, sends the contents of message.txt to all users.

Related commands

mesg — Control if (non-root) users can send messages to your terminal.
talk — Talk with other logged in users.
write — Send a message to another user.
shutdown — Schedule a time for the system to be powered down.

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Understanding the Linux wall Command

For users and administrators of Linux, mastering the built-in commands is vital to unlocking the full power of this operating system. In our focus today is the wall command. Known as the broadcast message command, wall is a crucial tool allowing communication to all users logged into a Linux system at once.

Syntax and Application of Linux’s Wall Command

Before we delve into its usage, let’s understand the syntax of the wall command:

Here, -n is an optional argument for suppressing the banner, and message signifies the content you want to broadcast.

If no message is supplied, the wall command will listen for input from the standard input (stdin).

Practical Usage of Linux’s Wall Command

Let’s illustrate the use of the wall command through several hands-on examples.

Broadcasting a Direct Message with Wall Command

The following command broadcasts a message to all logged-in users about a scheduled maintenance:

wall "Scheduled maintenance at 10:00 PM. Please save your work."

Sending a File Content as a Message with Wall Command

For longer messages stored in a file, the wall command shines with its versatility. If you have a file named notification.txt , you can use the command as follows:

This command will broadcast the content of notification.txt to all active users.

Using the Wall Command Without a Banner

The -n option comes handy when you want to suppress the banner and display only the message:

wall -n "Urgent update: Immediate system reboot required."

Broadcasting Command Output with Wall Command

You can also redirect the output of another command to the wall command. For instance, the following command sends the current system uptime to all users:

Scheduling Messages with Wall Command and Cron Jobs

To add another layer of utility, you can pair the wall command with cron jobs for scheduling regular notifications or reminders. If you need to send a daily reminder at 9 AM for data backup, add this line to your crontab file:

0 9 * * * wall "Daily reminder: Ensure your data is backed up."

The users will receive this reminder every morning at 9 AM, promoting a culture of regular data backups.

Wall Command Permissions and Restrictions in Linux

While the wall command proves valuable in sending system-wide messages, understanding its permissions and restrictions is essential for correct usage and effective communication.

Default Permissions of the Wall Command

By default, the wall command can be executed by all users. This means any user logged into the system can broadcast a message to all other users. While this could be useful in some scenarios, it may lead to unnecessary or irrelevant messages being sent system-wide.

Restricting Access to the Wall Command

To manage this, system administrators can restrict the execution of the wall command to only certain users. This can be achieved by modifying the permissions of the wall command’s binary file, typically located at /usr/bin/wall . For instance, to allow only the root user to execute the wall command, the following command can be used:

sudo chmod 700 /usr/bin/wall

This restricts the execution of the wall command to the root user, preventing other users from broadcasting messages system-wide.

The Wall Command and System Shutdowns in Linux

One common use case of the wall command is to notify users about impending system shutdowns or reboots. The shutdown command in Linux automatically uses the wall command to send a notification to all logged-in users before a shutdown or a reboot occurs.

For instance, to schedule a system shutdown one hour from now, you can use the following command:

Once this command is executed, all users receive a message informing them of the impending shutdown.

The Wall Command and User Sessions in Linux

An interesting aspect of the wall command is its interaction with various user sessions. When a message is broadcast using the wall command, it is sent to all terminal sessions where users are currently logged in.

This means if a user has multiple terminal sessions active, they will receive the message in all of their active sessions. This is especially useful for system administrators who need to ensure important notifications are received regardless of the terminal session a user may be focused on.

Customize Messages with the Wall Command in Linux

While the wall command does not offer direct formatting options for the messages, you can still craft informative and attention-grabbing messages. Given that the wall command can broadcast the contents of a text file, you can use a text editor to format your message with blank lines for spacing or capital letters for emphasis.

For instance, if you want to highlight an urgent system update, you could create a notification.txt file with the following content:

************** URGENT UPDATE ************** Immediate system reboot required for updates. Please save your work and log out.

And then use the wall command as follows:

Doing so will broadcast the message to all logged-in users, ensuring they are well-informed about critical system events.

Wrapping Up and Final Thoughts on Linux’s Wall Command

In our in-depth exploration of Linux’s wall command, we’ve delved into its syntax, practical usage, permissions, restrictions, and its role in system shutdowns. The wall command’s ability to broadcast messages to all logged-in users, whether direct, from a file, or command output, makes it an indispensable tool for system administrators. Additionally, its application in tailoring notifications and fostering user communication cannot be overstated.

Moving forward, we recommend Linux users, especially system administrators, to incorporate the wall command into their daily routines. Whether it’s scheduling reminders with cron jobs or alerting users about impending system shutdowns, the wall command will undeniably boost your efficiency and effectiveness in managing Linux systems. Mastering this command not only elevates your Linux proficiency but also adds another layer of communication within your Linux environment.

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