/etc/acpi/events/ac is in acpi-support 0.142-8.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 | # /etc/acpi/events/ac
# Called when the user connects ac power to us
#
event=ac_adapter.*
action=/etc/acpi/power.sh
|