Low Battery Custom Alert (notify-send)

Introduction

Having problems with low battery alerts? With this script you can create a custom low battery alert, with a few simple steps you can do it, so let’s get started.

Preview

To see a preview of this custom alert, run:

notify-send --urgency=critical \
            --icon=dialog-warning \
            "Low battery $(cat /sys/class/power_supply/BAT0/capacity)%."

Note that --icon uses a default icon, you can replace it by an image path

Create a custom alert

First we need to create a bash script

sudo touch /usr/local/bin/battery_monitor.sh &&
sudo chmod +x /usr/local/bin/battery_monitor.sh

Then copy and paste the following script into /usr/local/bin/battery_monitor.sh and edit it if necessary.

#!/bin/bash
#
# Author: Meyer Pidiache (github.com/meyer-pidiache)
#

# Get battery level
BATTERY_LEVEL=$(cat /sys/class/power_supply/BAT0/capacity)

# Get status (On AC / On Battery)
STATUS=$(cat /sys/class/power_supply/BAT0/status)

# Low battery percentage
BATTERY_THRESHOLD=20

# Check low battery
if [ "$STATUS" == "Discharging" ] && [ $(cat /sys/class/power_supply/BAT0/capacity) -le $BATTERY_THRESHOLD ]; then
  # Don't forget to change "username"
  DISPLAY=:0 XAUTHORITY=/home/{yourusername}/.Xauthority /usr/bin/notify-send --urgency=critical --icon=dialog-warning "Low battery ($BATTERY_LEVEL%)."
fi

Edit the script with the correct path to ~/.Xauthority.

Crontab

Finally, add the script we created to crontab.

crontab -e

Add this line at the end of the file:

# m h dom mon dow   command
*/1 * * * * /usr/local/bin/battery_monitor.sh

This will check the battery level every minute, and if it’s less than or equal to 20, the alert will be displayed.

In */1 * * * * * *, the symbols * represent the different time intervals, in the order minute - hour - day of the month - month - day of the week.