Gnome 3: How shutdown the computer from console with option to cancel?

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http://askubuntu.com – I want close the gnome session and shutdown the computer when the downloads finish but I want to show the shutdown window to can cancel it in some cases. I use: gnome-session-quit --power-off --force but this doesn't work when the screen is in suspend mode. Is this a bug or the normal behavior? In Gnome 2 this worked well even the screen is off. Any idea? (HowTos)