How can I listen for 'usb device inserted' events in Linux, in Python?

Question

I'd like to write a Python script for Amarok in Linux to automatically copy the stackoverflow podcast to my player. When I plug in the player, it would mount the drive, copy any pending podcasts, and eject the player. How can I listen for the "plugged in" event? I have looked through hald but couldn't find a good example.

Answer 1

I haven't tried writing such a program myself, however I've just looked at the following two links (thanks Google!), which I think will be of help:

• http://dbus.freedesktop.org/doc/dbus-python/doc/tutorial.html (which talks about how to use Python to access D-Bus)
• http://people.freedesktop.org/~david/hal-spec/hal-spec.html (which talks about how HAL publishes events to D-Bus)

In particular, read about the org.freedesktop.Hal.Manager interface, and its DeviceAdded and DeviceRemoved events. :-)

Hope this helps!

Answer 2

I think D-Bus would work as Chris mentioned, but if you're using KDE4, you might use the Solid framework in a manner similar to the KDE4 "New Device Notifier" applet.

The C++ source for that applet is here, which shows how to use Solid to detect new devices. Use PyKDE4 for Python bindings to these libraries, as shown here.

Answer 3

You can use D-Bus bindings and listen to DeviceAdded and DeviceRemoved signals. You will have to check the capabilities of the Added device in order to select the storage devices only.

Here is a small example, you can remove the comments and try it.

import dbus
import gobject

class DeviceAddedListener:
    def __init__(self):

You need to connect to Hal Manager using the System Bus.

        self.bus = dbus.SystemBus()
        self.hal_manager_obj = self.bus.get_object(
                                              "org.freedesktop.Hal", 
                                              "/org/freedesktop/Hal/Manager")
        self.hal_manager = dbus.Interface(self.hal_manager_obj,
                                          "org.freedesktop.Hal.Manager")

And you need to connect a listener to the signals you are interested on, in this case DeviceAdded.

        self.hal_manager.connect_to_signal("DeviceAdded", self._filter)

I'm using a filter based on capabilities. It will accept any volume and will call do_something with if, you can read Hal documentation to find the more suitable queries for your needs, or more information about the properties of the Hal devices.

    def _filter(self, udi):
        device_obj = self.bus.get_object ("org.freedesktop.Hal", udi)
        device = dbus.Interface(device_obj, "org.freedesktop.Hal.Device")

        if device.QueryCapability("volume"):
            return self.do_something(device)

Example function that shows some information about the volume:

     def do_something(self, volume):
        device_file = volume.GetProperty("block.device")
        label = volume.GetProperty("volume.label")
        fstype = volume.GetProperty("volume.fstype")
        mounted = volume.GetProperty("volume.is_mounted")
        mount_point = volume.GetProperty("volume.mount_point")
        try:
            size = volume.GetProperty("volume.size")
        except:
            size = 0

        print "New storage device detectec:"
        print "  device_file: %s" % device_file
        print "  label: %s" % label
        print "  fstype: %s" % fstype
        if mounted:
            print "  mount_point: %s" % mount_point
        else:
            print "  not mounted"
        print "  size: %s (%.2fGB)" % (size, float(size) / 1024**3)

if __name__ == '__main__':
    from dbus.mainloop.glib import DBusGMainLoop
    DBusGMainLoop(set_as_default=True)
    loop = gobject.MainLoop()
    DeviceAddedListener()
    loop.run()