[TYPO3] How to determine logged in users?

[Claus Faber]

I am writing a script which should show the usernames of all currently 
logged in users.

How can I do that? Is there any global variable I can call, or any 
table I can look in?

I have browsed the tables fe_users and fe_sessions for all sorts of 
timestamps, but none of them seem to show if users are still active.

thanks,

Claus

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