Hi,
Without user interaction - does that mean in background processing? If yes, forget the GUI download, because there is no frontend available during background processing. You'd have to create files using OPEN DATASET and WRITE DATASET statements and consequently all the download paths would need to be made available on application server.
Why would you even consider calling that external subroutine to do a very basic, fundamental task - create a file? In a program that clearly says in the description - "Test report...". Doubly so, if it restricts your choice of file names to CHAR 128...?
GUI_DOWNLOAD is "wrapped" in CL_GUI_FRONTEND_SERVICES as a static method if the functionality does need to work with user's local drives only and it takes string for file names.
cheers
Jānis