cron

the ultimate solution:

copy all current user environment variables to crontab.

to run notify-send you have to set DBUS_SESSION_BUS_ADDRESS

to run other gui programs you set DISPLAY and XAUTHORITY

wall works for tmux and ssh sessions but not gnome-terminal.

in kde everything works fine. install konsole instead.

script for monitoring disk usage:

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#!/bin/bash
used_percentage=$(df / | awk 'NR==2 {sub(/%/, "", $5); print $5}')
alarm_message="Root filesystem has less than 10% free space."
# Compare the percentage with the number 90
if [ "$used_percentage" -lt 90 ]; then
echo "Disk is ok."
else
wall $alarm_message
notify-send $alarm_message
fi