acpi-support script and dbus

[Nicolò Chieffo]

Hello! I'm writing an acpi-support script and I would like to use
notifies. so I installed libnotify-bin.

If I execute
su yelo3 -c "notify-send Hello World
from an acpi-support script I get this message:

libnotify-Message: Unable to get session bus: Failed to execute
dbus-launch to autolaunch D-Bus session

I've also tried to do it without the su command. what else should I try to do?
Thank you.