Does it have to be by command line? Have you ruled out the
MultiMaker?
'jAlbum's Multi Maker allows you easily submit multiple projects to be made and optionally uploaded in the background while you continue using jAlbum as normal. You can alternatively drag and drop a folder containing project files or a text file with a list of paths to the project files to be made. Once you've submitted the desired projects for processing, the MultiMaker window can be closed.'