2xxx 4xxx a.out abcabc bstj cacm cba childproof chmod chown ciphertext Cleartext cleartext compcon cp creat cryptologist's ct cu dev df doggie e.g foo garlinski grampp groupid i.e id ids inode inodes kmem LANs ls mem nowitz ok oring passwd ps ritchie rm rwx rwxr setuid sh stty su SUID sulog sys thompson tl truscott tty umask uniforum usr uucp uucppublic uux v7man vs weinberger xr