IriX64@FthrNtr ~
$ shutdown --help
Usage: shutdown [OPTION]... time
Bring the system down.

  -f, --force      Forces the execution.
  -s, --shutdown   The system will shutdown and power off (if supported)
  -r, --reboot     The system will reboot.
  -h, --hibernate  The system will suspend to disk (if supported)
  -p, --suspend    The system will suspend to RAM (if supported)
  -a, --abort      Aborts execution of formerly started shutdown.
  -x, --exitex     Use ExitWindowsEx rather than InitateSystemShutdown.
      --help       Display this help and exit.
      --version    Output version information and exit.

`time' is either the time in seconds or `+' and the time in minutes or a
timestamp in the format `hh:mm' or the word "now" for an immediate action.

To reboot is the default if started as `reboot', to hibernate if started
as `hibernate', to suspend if started as `suspend', to shutdown otherwise.

IriX64@FthrNtr ~
$