Sway battery low notifier

batman.sh

#!/bin/bash

bat_low_threshold=$1
poll_interval=60 # seconds

function bat_high {
    local cap=$(cat /sys/class/power_supply/BAT0/capacity)
    if [[ $cap -lt $bat_low_threshold ]]; then
        return 1
    else
        return 0
    fi
}

function nap {
    sleep $poll_interval
}

for pid in $(pidof -x "batman.sh"); do
    if [ $pid != $$ ]; then
        echo "Batman #$pid is already on patrol!"
        exit 1
    fi
done

while true; do
    while bat_high; do nap; done
    swaynag --message "Battery is low"
    until bat_high; do nap; done
done