To see if particular users are logged into a Linux or Unix server, you can use the who command.
The who command displays a list of users who are currently logged into the system. You can use the who command with the -u option to show the user name, terminal name, and the time the user logged in for each user.
Here is an example of how to use the who command to see if particular users are logged into the server:
who -uSource.www:lautturi.com
This will display a list of all users who are currently logged into the system.
To see if a particular user is logged into the server, you can use the grep command to search the output of the who command for the user name. For example, to see if the user john is logged into the server, you can use the following command:
who -u | grep john
This will search the output of the who command for the user name john and display any matching lines. If the user john is logged into the server, the command will display the user name, terminal name, and login time for that user. If the user is not logged into the server, the command will not display any output.
You can use this technique to check if any particular user is logged into the server. Simply replace john with the user name you want to check.
Keep in mind that the who command only displays users who are logged into the system through a terminal or console. It may not show users who are logged into the system through a network connection or other remote access methods. To see a complete list of users who are logged into the system, you may need to use other tools, such as the last command or the w command.