Libnotify

require 'libnotify'
Libnotify.show(:body => "hello", :summary => "world", :timeout => 2.5)

require 'libnotify'

n = Libnotify.new do |notify|
  notify.summary    = "hello"
  notify.body       = "world"
  notify.timeout    = 1.5         # 1.5 (s), 1000 (ms), "2", nil, false
  notify.urgency    = :critical   # :low, :normal, :critical
  notify.append     = false       # default true - append onto existing notification
  notify.transient  = true        # default false - keep the notifications around after display
  notify.icon_path  = "/usr/share/icons/gnome/scalable/emblems/emblem-default.svg"
end

n.show!

require 'libnotify'

# Mixed syntax
options = {:body => "world", :timeout => 20}
Libnotify.show(options) do |opts|
  opts.timeout = 1.5     # overrides :timeout in options
end

require 'libnotify'

# Icon path auto-detection
Libnotify.icon_dirs << "/usr/share/icons/gnome/*/"
Libnotify.show(:icon_path => "emblem-default.png")
Libnotify.show(:icon_path => :"emblem-default")

# Update pre-existing notification then close it
n = Libnotify.new(:summary => "hello", :body => "world")
n.update # identical to show! if not shown before

Kernel.sleep 1

n.update(:body => "my love") do |notify|
  notify.summary = "goodbye"
end

Kernel.sleep 1

n.close