interrupts to notify events in linux

Question

I want to write a program which notifies when the laptop battery level falls below a certain threshold level. I am using ubuntu 11.04 . Is there a way in which i can generate an interrupt without polling the battery. What system calls in linux are used to achieve this ?

Answer 1

There is no system call interface to ACPI in Linux... All of the I/O is done using /proc/acpi or /sys/class entries. Easiest implementation would be a polling software, and read the interface periodically (going to sleep if the threshold is not there yet) — this is because typically /proc and /sys files construct the desired information while handling the read(2).