How can I send a desktop notification via Emacs?

Question

In bash syntax, one can use notify-send to make a message appear in the desktop. How can we accomplish the same with elisp?

Answer 1

On GNU/Linux systems, there is the notifications.el package in core Emacs. Example from the info manual:

      (require 'notifications)

      (defun my-on-action-function (id key)
        (message "Message %d, key \"%s\" pressed" id key))
           ⇒ my-on-action-function

      (defun my-on-close-function (id reason)
        (message "Message %d, closed due to \"%s\"" id reason))
           ⇒ my-on-close-function

      (notifications-notify
       :title "Title"
       :body "This is <b>important</b>."
       :actions '("Confirm" "I agree" "Refuse" "I disagree")
       :on-action 'my-on-action-function
       :on-close 'my-on-close-function)
           ⇒ 22

      A message window opens on the desktop.  Press ``I agree''.
           ⇒ Message 22, key "Confirm" pressed
              Message 22, closed due to "dismissed"

The whole description is in the Elisp manual, see (info "(elisp) Desktop Notifications")

Answer 2

you can use notifications.el as described in Michael Albinus' answer or the alert package from melpa which can be simpler in many cases and works cross-platform.

e.g. (alert "This is an alert" :title "My Alert" :category 'debug)