guestfish returns 0 if the commands completed without error, or 1 if there was an error. But the rule break when we use '-' prefix subcommands: ------------------------------------ $ guestfish <<\EOF > blabla > EOF blabla: unknown command $ echo $? 1 $ guestfish <<\EOF -blabla EOF blabla: unknown command $ echo $? 0 ------------------------------------ I think it should be more reasonable to make the behaviours keeping identical with the rule.