#!/bin/sh
#
# Returns 0 (true) if on AC power; 1 (false) if on battery power or unknown.
# If false, prints the current battery level on stdout.
#
# Example shell script:
#
# if on_ac_power >/dev/null; then
#	echo On AC power...
# else
#	echo On battery power: battery level is $(on_ac_power)
# fi
#

# if no /proc/apm, assume we're on wall power.
[ ! -f /proc/apm ] && exit 0;

exec awk </proc/apm '
	/^[0-9.]* [0-9.]* 0x.. 0x../ {
		if ($4 == "0x01")
			exit 0;
		else {
			sub("%", "", $7);
			sub("-1", "100", $7);
			print $7;
			exit 1;
		}
	}
'
