how to configure, upload path to current logged user directo

Hi,
My application creates folders for every user and a support directory under the same to store user file uploads.

ex.
/user1/uploads
/user2/uploads
/user3/uploads

How will i be able to setup the upload path to the current user who logged in?
Ex. If user1 is logged in then the path should be /user1/uploads and so on...

Appreciate your help / support in this regard.
M