This is done with eZUser::currentUser(); that will return an eZUser object with the current logged in user.
Note that the user is a datatype, which is a part of a content object. To get access to the attributes you need to fetch the contentobject from the user object.
Thanks that's exactly what I was wondering. So I must get the content object that corresponds to the user. What datameber of ezUser corresponds to the contentId