Set the commands - Open session commands

[aojha]

How can I pass the current user name or ID to Open session command. In below example every time reports runs first it calls GiveDataAccess procedure, passes current user name as parameter values so that users data access is setup before report output comes. Is there any system variable which can be used in this store procedure call which can pass current login user name? or any other way to do this? Thank you. My database is Sybase IQ.

<commandBlock>
  <commands>
   <sqlCommand>
    <sql>EXECUTE dbo.GiveDataAccess('CurrentUserName')</sql>
   </sqlCommand>
  </commands>
</commandBlock>