How to print a message when my plugin is being activated?

I want to print a specific message when my plugin is being activated.
To do this, I need to get a name of my plugin after activation.

For example, this tells me a name of a plugin when an activation fails: $_GET['plugin'].
But when the activation is succesfull, it does not work.

Can you help me out?
Thanks!

 

I am not sure but I think you use register_activation_hook.

Write a function to print the message, then register it with <?php register_activation_hook($file, $function); ?>

Hope that works

 

Sadly, this does not work. I tried it as my first idea.

 

Yeah, there are lots of complains about that one. It should work if everything is in the main plugin file.

The only other function I know of is plugins_loaded, but I think that gets called a lot more often.

 

But how can I recognize that a specific plugin has been activated? If there would be 2 or more plugins installed using the same notification code, it might not work properly.

 

Any ideas?