commandline and graphic extended file manipulation using linux filesystem extended attributes

wrote some tools manipulating two extended attributes on regular files, designed whith the idea of helping me to categorize and retrieve images in big images folders, without folding these in subfolder : as an image could be responding to multiple categories, it would requier hardlinks... So I defined that I'll now be using two xattr : user.author storing the image author if relevant, and, user.tags storing image keyword categories separated by spaces.