[support] How to disable caching of a block

[Arne 'Timwi' Heizmann]

Hi,

On my Drupal site I tried to create a block to show the username you are 
currently logged in as. Unfortunately, it always shows "Timwi" (my own 
username) even if I'm logged in under another account. I believe this is 
because the block is rendered and then cached when it is created or its 
settings changed, and not when the page is viewed.

This effect occurs even if "Caching" under "Performance" 
(admin/settings/performance) is disabled.

(In order to display the logged-in user in the block, I created a simple 
Input Format that lets me use a "[user]" tag to insert the username. In 
the code, it uses "global $user; return $user->name;".)

How can I achieve what I want? All I want is for it to display who I'm 
logged in as.

Thanks in advance!
Timwi