How can I make this script run in the background?
#!/bin/bash
# Get the battery percentage for battery 0
battery0_percent=$(cat /sys/class/power_supply/BAT0/capacity)
# Get the battery percentage for battery 1
battery1_percent=$(cat /sys/class/power_supply/BAT1/capacity)
# Threshold level
threshold=10
# Check if either battery is less than 10%
if [ "$battery0_percent" -lt "$threshold" ] || [ "$battery1_percent" -lt "$threshold" ]; then
# Display a Zenity warning
zenity --warning --text "Battery level is below 10% on one or both batteries!"
fi
This script sends a warning when one of my batteries is below 10%.
How can I run this script in the background, on a Linux system, so it will notify me when it has to?
You have 2 ways to do this:
Add an ampersand after the command
./battery-script.sh &
This will keep the command running even after you close the terminal, by spawning a subprocess within your shell
If you want something that persists even after you log out the shell, you can add nohup before the command
nohup ./battery-script.sh
This will also redirect the output of the command into a file called "nohup.out"
If you want to go even further and run this script at startup, you also have a few different options:
If you want this script to start up every time you start your display server:
With x11:
Add the line ./battery-script.sh & to the end of your ~/.xinitrc for the script to be run every time you start up x11(probably what you want in this scenario, given how you have a line for a zenity warning)
If you run wayland, it depends on your wm, with sway it’s .config/sway/config.d/autostart_applications
If you want to run the script before your display server even starts, you can put the script in /etc/profile.d
As already said, you can simply use & to run in background.
If you need to detach/attach, the way to go is to use tmux or screen, that way, you can attach/detach a session as you need.
To run a command in background with screen:
screen -d -m -S NameOfTheSession ./script.sh
to list sessions available:
screen -ls
to re-attach:
screen -r NameOfTheSession
Create a systemd timer unit to have it run at regular intervals in the background.
/etc/systemd/system/my-batterywatcher.service
[Unit]
Description=my battery watcher
[Service]
Type=oneshot
ExecStart=/bin/bash /path/to/battery-watcher.sh
/etc/systemd/system/my-batterywatcher.timer
[Unit]
Description=my battery watcher
[Timer]
# run every minute
OnCalendar=*-*-* *:*:00
Unit=my-batterywatcher.service
[Install]
WantedBy=timers.target
systemctl daemon-reload
systemctl enable my-batterywatcher.timer
Several suggestions to run it in the background or as a conventional daemon, but this needs to run inside the session of the active user (since it wants to access the DISPLAY of the authenticated user).
Different X11 environments (not to mention Wayland) have different ways of starting up per-session services, but I believe the most portable one should be the XDG autorun mechanism. i.e. add (or link) the script in /etc/xdg/autostart/