To be able to invoke commands like suspend and hibernate from the command line not so long ago required having root privileges or using the desktop environment built-in tools. Now to invoke suspend, hibernate, shutdown, or restart, D-Bus can be invoked as Regular user. I created a script called
pwrman to ease the task (requires UPower to be installed).
(I got this idea from a person from the Arch Linux forums. I forgot who you are, so sorry, but thank you.)