[galaxy-dev] Display galaxy variable

Hello, In a Galaxy tool, I would like to display a pre-completed path in the xml inputbox, inside the tool.xml file. Consequently, I would like to add a variable in an <param value="" /> tag , like this : <tool id="test" name="test" version=""> <command interpreter="sh">test.sh $in $out</command> <inputs> <param name="filepath" type="text" size="100" value="/work/$out" /> </inputs> ... and in test.sh : $out is defined to be ${trans.user.username} Do you have any idea to display ${trans.user.username} variable in order to be shown in galaxy interface (gui) thanks to xml file ? I achieve to display ${trans.user.username} in /templates/root/tool_menu.mako but not in the xml file. Thanks in advance, Sarah