Cron with notify-send

In Ubuntu 14.04 exporting the display did not work for me. Below is a cron script I'm using to shutdown a virtual machine when a laptop's battery state becomes too low. The line setting DBUS_SESSION_BUS_ADDRESS is the modification that finally got the warnings working correctly.

#!/bin/bash

# if virtual machine is running, monitor power consumption
if pgrep -x vmware-vmx; then

  bat_path="/sys/class/power_supply/BAT0/"

  if [ -e "$bat_path" ]; then

    bat_status=$(cat $bat_path/status)

    if [ "$bat_status" == "Discharging" ]; then

      bat_current=$(cat $bat_path/capacity)

      # halt vm if critical; notify if low
      if [ "$bat_current" -lt 10 ]; then

        /path/to/vm/shutdown/script
        echo "$( date +%Y.%m.%d_%T )" >> "/home/user/Desktop/VM Halt Low Battery"

        elif [ "$bat_current" -lt 15 ]; then
        eval "export $(egrep -z DBUS_SESSION_BUS_ADDRESS /proc/$(pgrep -u $LOGNAME gnome-session)/environ)";
        notify-send -i "/usr/share/icons/ubuntu-mono-light/status/24/battery-caution.svg"  "Virtual machine will halt when battery falls below 10% charge."

      fi

    fi

  fi

fi

exit 0

The relevant line is here:

eval "export $(egrep -z DBUS_SESSION_BUS_ADDRESS /proc/$(pgrep -u $LOGNAME gnome-session)/environ)";

I found the solution here: https://askubuntu.com/a/346580/255814

Only this works for me (Xubuntu)

eval "export $(egrep -z DBUS_SESSION_BUS_ADDRESS /proc/$(pgrep -u $LOGNAME xfce4-session)/environ)"; notify-send  "hello world" 

If you are in gnome enviroment, you need change xfce4-session to gnome-session

refer: https://askubuntu.com/questions/298608/notify-send-doesnt-work-from-crontab

I found the answer:

$ crontab -l
# m h  dom mon dow   command
  * *   *   *   *    export DISPLAY=:0.0 && export XAUTHORITY=/home/ravi/.Xauthority && sudo -u ravi /usr/bin/notify-send Hey "How are you"

I use i3 on Ubuntu 18.04. My way to solve this is:

* * * * * XDG_RUNTIME_DIR=/run/user/$(id -u) notify-send Hey "this is dog!"

Edit 2020: I still use it on Ubuntu 20.04.