D-Bus is an interprocess communication mechanism for Linux. Ruby D-Bus is a pure Ruby library for writing clients and services for D-Bus.

Check whether the system is on battery power via UPower

require "dbus"
sysbus = DBus.system_bus
upower_service   = sysbus["org.freedesktop.UPower"]
upower_object    = upower_service["/org/freedesktop/UPower"]
upower_interface = upower_object["org.freedesktop.UPower"]
on_battery       = upower_interface["OnBattery"]
if on_battery
  puts "The computer IS on battery power."
else
  puts "The computer IS NOT on battery power."
end

• Ruby 2.4 or newer.

• gem install ruby-dbus

Ruby D-Bus currently supports the following features:

• Connecting to local buses.
• Accessing remote services, objects and interfaces.
• Invoking methods on remote objects synchronously and asynchronously.
• Catch signals on remote objects and handle them via callbacks.
• Remote object introspection.
• Walking object trees.
• Creating services and registering them on the bus.
• Exporting objects with interfaces on a bus for remote use.
• Rubyish D-Bus object and interface syntax support that automatically allows for introspection.
• Emitting signals on exported objects.

See some of the examples in the examples/ subdirectory of the tarball. Also, check out the included tutorial (in Markdown format) in doc/Tutorial.md or view it online on https://github.com/mvidner/ruby-dbus/blob/master/doc/Tutorial.md .

Ruby D-Bus is free software; you can redistribute it and/or modify it under the terms of the GNU Lesser General Public License as published by the Free Software Foundation; either version 2.1 of the License, or (at your option) any later version.