If compiled without libacl support, this function always returns None When opam is built with libacl support, get_acl_executable_info file owner takes a filename and the uid of the owner of that file (this is passed since the caller will have already called Unix.stat). The function returns Some [] if the process can execute file or Some gids if the process can execute file if one of its groups matches gids. If the process cannot under any circumstances execute file (or if an unexpected error occurred), then None is returned.