Edit: /usr/sbin/on_ac_power (2228B)
#!/bin/sh
#
# Returns 0 (true) if on AC power
# 1 (false) if not on AC power
# 255 (false) if can't tell
#
# Example shell script:
# if on_ac_power; then
# echo We're on AC power
# else
# echo Can't say we're on AC power
# fi
set -e
# sysfs
#
# This algorithm is complicated by the possibility of multiple AC
# adapters. We scan the ac_adapter/power_supply directory looking for adapters
# that have known states. If any adapter is on-line, we return 0. If
# no adapters are on-line but one or more are off-line, we return 1.
#
OFF_LINE_P=no
if [ -d /sys/class/power_supply/ ]; then
for FN in /sys/class/power_supply/*; do
if test -d "${FN}" && test -r "${FN}/type"; then
type="$(cat "${FN}/type")"
case "${type}" in
Mains|USB*|BrickID|Wireless)
if [ -r "${FN}/online" ]; then
online="$(cat "${FN}/online")"
[ "$online" = 1 ] && exit 0
[ "$online" = 0 ] && OFF_LINE_P=yes
fi;;
esac
fi
done
[ "${OFF_LINE_P}" = "yes" ] && exit 1
fi
# ACPI
# same algorithm as above, a fallback only when the generic sysfs interface
# is not available (old kernels only)
if [ -d /proc/acpi/ac_adapter ]; then
for FN in /proc/acpi/ac_adapter/*; do
if [ -d "${FN}" ]; then
if [ -r "${FN}/state" ]; then
grep --quiet on-line "${FN}/state" && exit 0
grep --quiet off-line "${FN}/state" && OFF_LINE_P=yes
elif [ -r "${FN}/status" ]; then
grep --quiet on-line "${FN}/status" && exit 0
grep --quiet off-line "${FN}/status" && OFF_LINE_P=yes
fi
fi
done
[ "${OFF_LINE_P}" = "yes" ] && exit 1
fi
# PMU
if [ -r /proc/pmu/info ]; then
exec awk