getauth en action neal@desdemona:~/getauth (0)$ ids effective uids: 1000(neal) effective gids: 1000(neal) available uids: 1000(neal) 1000(neal) available gids: 1000(neal) 1000(neal) neal@desdemona:~/password (0)$ ./getauth 0 bar ./getauth: Invalid password: Permission denied neal@desdemona:~/getauth (0)$ ./getauth 1001 bar neal@desdemona:~/getauth (0)$ ids effective uids: 1000(neal) effective gids: 1000(neal) available uids: 1000(neal) 1000(neal) 1001(foo) available gids: 1000(neal) 1000(neal) 1001(foo) neal@desdemona:~/getauth (0)$