notify-send

Uses the current desktop environment's notification system to create a notification.

Show a notification with the title "Test" and the content "This is a test":

notify-send {{"Test"}} {{"This is a test"}}

Show a notification with a custom icon:

notify-send -i {{icon.png}} {{"Test"}} {{"This is a test"}}

Show a notification for 5 seconds:

notify-send -t 5000 {{"Test"}} {{"This is a test"}}