$ man crontab

...
  crontab Access Control
     Users: Access to crontab is allowed:

        o  if the user's name appears in /etc/cron.d/cron.allow.

        o  if  /etc/cron.d/cron.allow  does  not  exist  and  the
           user's name is not in /etc/cron.d/cron.deny.

     Users: Access to crontab is denied:

        o  if /etc/cron.d/cron.allow exists and the  user's  name
           is not in it.

        o  if /etc/cron.d/cron.allow does not  exist  and  user's
           name is in /etc/cron.d/cron.deny.

        o  if  neither  file  exists,  only  a  user   with   the
           solaris.jobs.user authorization is allowed to submit a
           job.

        o  If BSM audit is  enabled,  the  user's  shell  is  not
           audited  and  the  user is not the crontab owner. This
           can occur if the user logs in via a program,  such  as
           some versions of SSH, which does not set audit parame-
           ters.

     Notice that the rules for allow and deny apply to root  only
     if the allow/deny files exist.

     The allow/deny files consist of one user name per line.
...

$ ls -la /dev/console
lrwxrwxrwx   1 root     other         30 Apr  6  2005 /dev/console -> ../devices/pseudo/cn@0:console
$ ls -la /devices/pseudo/cn@0:console
 crw--w----    1 root     tty        0,  0 Dec 11 11:15 /devices/pseudo/cn@0:console

$ exp / file=file.exp

Export: Release 9.2.0.8.0 - Production on Tue Dec 11 12:33:15 2007

Copyright (c) 1982, 2002, Oracle Corporation.  All rights reserved.


EXP-00056: ORACLE error 1017 encountered
ORA-01017: invalid username/password; logon denied
Username: ^D
EXP-00030: Unexpected End-Of-File encountered while reading input
EXP-00000: Export terminated unsuccessfully

$ echo $?
 1 
$ echo $?
 0 
$ echo $?
0
...