ZJ.Mike.2009 has asked for the wisdom of the Perl Monks concerning the following question:

I want my Perl script to know when a USB device is inserted and which new volume letter appear on my Windows XP. I've done a little of googling and I've found something that looks relevant to my question: 
1. The system broadcasts a set of default device change events to all 
+application.
2. Any application with a top-level window can receive basic notificat
+ions by processing the WM_DEVICECHANGE message.
3. The DBT_DEVICEARRIVAL and DBT_DEVICEREMOVECOMPLETE events are autom
+atically broadcast to all top-level windows. Volume notifications are
+ also broadcast to top-level windows.

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My question is: 
1. If I create a simple GUI application using Win32::GUI, will this ap
+plication also receive DBT_DEVICEARRIVAL message sent by Windows syst
+em?
2. If so, how do I look at the message. I checked the Event method of 
+Win32::GUI and there're GetMessage() and PeekMessage() methods. Are t
+hey going to see the DBT_DEVICEARRIVAL message?
3. Or are there some other approaches, for example, using Win::API to 
+import the WM_ONDEVICECHANGE function and then do some stuff?

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Thanks for your attention :)

Replies are listed 'Best First'.
Re: How do I know when a USB device is inserted?
by Corion (Patriarch) on Mar 06, 2010 at 05:55 UTC

    I use (and wrote) DBD::WMI to monitor the addition/removal of devices, but using it in a GUI program means that you'll have to use a second thread that listens to the WMI.

    If you're using Win32::GUI, then yes, those messages will get sent to your top level window as well.

    Looking through Win32::GUI, resp. the Win32::GUI examples, I see listview_drag_drop.pl, which hooks a message (WM_CONTEXTMENU) to a callback. I didn't find it documented anywhere, but it seems that it is a/the way to specify callbacks to window messages in Win32::GUI. I guess that the following code should issue the callback whenever a device changes:

    use constant WM_ONDEVICECHANGE => 0x219; # as per http://msdn.microsof
+t.com/en-us/library/aa363480%28VS.85%29.aspx
$window->Hook(\&device_changed);

sub device_changed {
    ...
};

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[d/l]

      Corion, thanks a lot for the information:)

      I think I'll try the DBD::WMI module first and I'll see what I can do with a GUI interface.

      Thanks again :)

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        Here's a working example:

        #!perl -w
use strict;
use Win32::GUI ();

use constant WM_DEVICECHANGE => 0x219;
# as per http://msdn.microsoft.com/en-us/library/aa363480%28VS.85%29.a
+spx

sub device_changed {
    my ($win, @args) = @_;
    Win32::GUI::MessageBox(0,"Device changed: @args\n");
};

my $mw = Win32::GUI::Window->new();

$mw->Hook(WM_DEVICECHANGE, \&device_changed);

$mw->Show();

Win32::GUI::Dialog();
print "Done\n";

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        A problem with this approach is that WM_DEVICECHANGE does not seem to fire if AutoPlay is disabled for devices, at least I don't get the message when I insert a CF card in my CF card reader, while I get the message when I plug/unplug some other device.

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Re: How do I know when a USB device is inserted?
by grantm (Parson) on Mar 07, 2010 at 21:38 UTC

    This is not directly relevant to your situation since you're running Windows, but I thought I'd answer anyway in case a Linux user comes across this question.

    On Linux you can use the Net::DBus module to to subscribe to notifications from HAL (the Hardware Abstraction Layer). The Net::DBus::GLib module allows easy integration with a Gtk app without needing to use threads. An example of an app that does this is my usb-key-copy-con a Perl GUI tool for automated copying of USB storage devices.

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