Low battery warning with i3-nagbar

batnag.py

#!/usr/bin/env python

import signal
import subprocess
import time
import sys

test = False


def close_fullscreen():
    x, y = subprocess.check_output(
        ['xdotool', 'getdisplaygeometry']).decode().split()
    window_id = subprocess.check_output(
        ['xdotool', 'getactivewindow']).decode().strip()
    geometry = subprocess.check_output(
        ['xdotool', 'getwindowgeometry', window_id]).decode().split()
    if geometry[3] == '0,0' and geometry[7] == '{}x{}'.format(x, y):
        # toggle full screen mode
        subprocess.call(['xdotool', 'key', 'alt+f'])


def handler(signum, frame):
    global test
    # exit full screen mode if needed
    try:
        close_fullscreen()
    except:
        pass
    # Broadcast message
    subprocess.call("echo 'Battery level is critical.'|wall", shell=True)
    # fork process
    p = subprocess.Popen(
        ['i3-nagbar', '-t', 'error', '-m',
         'Battery level is critical.'])

    if test:
        time.sleep(4)
        p.terminate()
        return

    while True:
        try:
            with open('/sys/class/power_supply/BAT0/status') as f:
                status = f.read().strip()
        except:
            p.terminate()
            return
        if status and status != 'Discharging':
            p.terminate()
            return
        time.sleep(1)


def main(argv=[]):
    timeout = 60
    signal.signal(signal.SIGALRM, handler)

    if argv and argv[0] == 'test':
        global test
        test = True
        signal.alarm(1)
        time.sleep(1)
        sys.exit(0)

    while True:
        try:
            with open('/sys/class/power_supply/BAT0/status') as f:
                status = f.read().strip()
        except:
            pass
        else:
            if status == 'Discharging':
                try:
                    with open('/sys/class/power_supply/BAT0/capacity') as f:
                        level = int(f.read())
                except:
                    pass
                else:
                    if level < 2:
                        signal.alarm(1)
                    elif level < 5:
                        timeout = 15
                    elif level < 10:
                        timeout = 30
            else:
                timeout = 60
        finally:
            time.sleep(timeout)

if __name__ == '__main__':
    main(sys.argv[1:])