How to pass current logged in users userid to .aspx page

I want to pass current logged in users userid to http://test.com/testing.aspx page so it will be for user having userid 743

http://test.com/testing.aspx?EMP=743

But here useid 743 is not constant it shold be dynamic and pic at runtime on basis of which user click on link.

I am using SAP EP 7.4 version can anybody please help in this.