i3-battery-warning/i3batwarn.sh

#!/bin/bash -x

#############################################
# This is a simple battery warning script.  #
# It uses i3's nagbar to display warnings.  #
#                                           #
# @author agribu                            #
#############################################

# set Battery
BATTERY=$(ls /sys/class/power_supply/ | grep '^BAT')

# set full path
ACPI_PATH="/sys/class/power_supply/$BATTERY"

# get battery status
STAT=$(cat $ACPI_PATH/status)

# get remaining energy value
REM=`grep "POWER_SUPPLY_CHARGE_NOW" $ACPI_PATH/uevent | cut -d= -f2`

# get full energy value
FULL=`grep "POWER_SUPPLY_CHARGE_FULL_DESIGN" $ACPI_PATH/uevent | cut -d= -f2`

# get current energy value in percent
PERCENT=`echo $(( $REM * 100 / $FULL ))`

# set error message
MESSAGE="AWW SNAP! I am running out of juice ...  Please, charge me or I'll have to power down."

# set energy limit in percent, where warning should be displayed
LIMIT="10"

# show warning if energy limit in percent is less then user set limit and
# if battery is discharging
if [ $PERCENT -le "$(echo $LIMIT)" ] && [ "$STAT" == "Discharging" ]; then
    DISPLAY=:0.0 /usr/bin/i3-nagbar -m "$(echo $MESSAGE)"
fi