Linux: Triggering desktop notification pop-up when service is executed with systemd

Question

I want to trigger a desktop notification pop-up when a service is executed with systemd on my Linux desktop. The main reason why I am doing this is that I want to learn how to work with systemd timers and services by creating my own scheduled jobs and I would like to pop-up a desktop notification, when a service/job is executed, just to know that something is happening.

I have created a basic example to do that:

notifysystemd.sh:

#!/bin/bash

# Variable to hold path to systemd job logs
SYSTEMD_LOG_DIR='/home/jay/scheduledJobLogs/systemDJobLogs'
SYSTEMD_JOB_NAME='NotifySystemD'
CURRENT_MONTH=$(date '+%b')

# Send notification to desktop
notify-send 'You can automate and schedule anything with systemd today!'

# Write down in the log
CURRENT_TIME=$(date '+%Y-%m-%d-%H:%M')
LOG_RECORD="${CURRENT_TIME} SystemD notification job executed."

# Create a directory for systemd jobs logging, if it doesn't already exist. And don't error if it does exist
mkdir -p $SYSTEMD_LOG_DIR/$SYSTEMD_JOB_NAME

# Write the log record!
echo $LOG_RECORD >> $SYSTEMD_LOG_DIR/$SYSTEMD_JOB_NAME/$CURRENT_MONTH.txt

with this service file:

notifysystemd.service:

[Unit]
Description=A basic service to send a desktop notification using the systemd scheduler
Wants=notifysystemd.timer

[Service]
Type=forking
ExecStart=/home/jay/systemDJobs/notifysystemd.sh
Environment="DISPLAY=:0" "DBUS_SESSION_BUS_ADDRESS=unix:path=/run/user/$(id -u)/bus" "XAUTHORITY=/home/jay/.Xauthority"

[Install]
WantedBy=default.target

and this timer file:

notifysystemd.timer:

[Unit]
Description=Send a notification three minutes after PC start
RefuseManualStart=false # Allow manual starts
RefuseManualStop=false # Allow manual stops

[Timer]
#Execute job if it missed a run due to machine being off
Persistent=true
OnBootSec=180
#File describing job to execute
Unit=notifysystemd.service

[Install]
WantedBy=timers.target

The service is executed correctly with the correct delay (I can see that in the log created), but I am getting no desktop notification.

I have looked into several questions already asked on this forum:

systemd service not executing notify-send

notify-send command doesn't launch the notification through systemd service

Which suggest specifying environment variables in either the .service file or in the shell script.

I have tried all of them and none led to a notification appearing.

I have done the same with cronie, where was sufficient to specify the DISPLAY and DBUS_SESSION_BUS_ADDRESS environement variables the same way as I did in the notifysystemd.service file.

Lastly, if there is a better way how to achieve the same result, but which revolves around usage of systemd, I am opened to optimal, or more ergonomic solutions.

Answer 1

In systemd instead of notify-send put the output in a file.
Write a bash script and start it on desktop login (so this script can notify-send).

In the script write an endless loop.
Use inotifywait in the loop to monitor the output file for modification.
(This will suspend your script and won't eat cpu)
After inotify, read the content of the file and use notify-send.