[galaxy-user] Using user name in a tool's XML

Hello, Is it possible to access the user name inside a tool's XML configuration file ? I want to pass the user name (the user who executed the job) as an argument to the tool. Is there such a variable? Something like: <tool id="mytool" name="foobar"> <command>mytool.sh --file $input --title $input.name --user $galaxy_user</command> ... ... Thanks, Gordon