I would like to use a gesture to shutdown/restart my computer and I need to know the command that launches the shutdown dialog:

I would like to use a gesture to shutdown/restart my computer and I need to know the command that launches the shutdown dialog:

/usr/lib/indicator-session/gtk-logout-helper can be used to open the following dialogs:
Log Out (/usr/lib/indicator-session/gtk-logout-helper --logout)

Restart (/usr/lib/indicator-session/gtk-logout-helper --restart)

Shutdown (/usr/lib/indicator-session/gtk-logout-helper --shutdown)

In Gnome Shell if I try /usr/lib/indicator-session/gtk-logout-helper --shutdown I obtain the dialog in the screenshot you provided, but when I click on Shut Down I receive another dialog (similar to the first). Only after a second confirm my system shuts down.
This method reaches the second dialog directly via command line?
gnome-session-quit --power-off