In recent linux kernels, the /proc/acpi/event interface has been deprecated. 
The same information (and more) is available via netlink (a way for the 
kernel to communicate with userspace that is usually used for networking) 
and the input layer (mouse, keyboard, power button, etc...). This version of 
acpid supports netlink and the input layer.

The ACPI Daemon v2
https://sourceforge.net/projects/acpid2/