To find out which app/program grabbed your key use the debug keysym XF86LogGrabInfo. Use xdotool to press keys + XF86LogGrabInfo at the same time e.g. in a terminal run
KEY=XF86AudioPlay xdotool keydown ${KEY}; xdotool key XF86LogGrabInfo; xdotool keyup ${KEY} Then check for output with tail /var/log/Xorg.0.log
Note that with gnome 3/gdm and systemd this is no longer logged to Xorg.0.log (it's instead logged to the journal). In that case you could run
journalctl -f and then in another terminal run the xdotool commands. Switch to the first terminal and you'll see something like
/usr/lib/gdm/gdm-x-session[629]: Active grab 0x40c0a58e (xi2) on device 'Virtual core keyboard' (3): /usr/lib/gdm/gdm-x-session[629]: client pid 708 /usr/bin/gnome-shell /usr/lib/gdm/gdm-x-session[629]: at 32595124 (from passive grab) (device frozen, state 6) /usr/lib/gdm/gdm-x-session[629]: xi2 event mask for device 3: 0xc000 /usr/lib/gdm/gdm-x-session[629]: passive grab type 2, detail 0xac, activating key 172 In the above example the program (the client) that grabbed the key is gnome-shell.
How do I figure out what the keys are called?
Check out the manpage of xdotool using man xdotool or an online version, as it lists a number of the special keys. For instance, "alt+r", "Control_L+J", "ctrl+alt+n", "BackSpace". The LinuxQuestions wiki also has a list of X Keysyms one could use. To make things a bit easier, xdotool also has aliases for some of these, such that pressing Shift-Alt-Tab would for instance just be shift+alt+Tab. To verify that this does indeed click that key combination, you could send the input to xev, which is a program that will print whatever key or mouse events it gets to the console. Just do sleep 2; xdotool keydown ${KEY} and switch to the xev window before two seconds has passed to see the keys being clicked on that window. It should then output a series of events, such as these:
PropertyNotify event, serial 168, synthetic NO, window 0x1e00001, atom 0x13e (_GTK_EDGE_CONSTRAINTS), time 4390512, state PropertyNewValue MappingNotify event, serial 168, synthetic NO, window 0x0, request MappingKeyboard, first_keycode 8, count 248 KeyPress event, serial 168, synthetic NO, window 0x1e00001, root 0x163, subw 0x0, time 4390719, (882,657), root:(1000,771), state 0x0, keycode 64 (keysym 0xffe9, Alt_L), same_screen YES, XLookupString gives 0 bytes: XmbLookupString gives 0 bytes: XFilterEvent returns: False KeyPress event, serial 169, synthetic NO, window 0x1e00001, root 0x163, subw 0x0, time 4390738, (882,657), root:(1000,771), state 0x8, keycode 23 (keysym 0xff09, Tab), same_screen YES, XLookupString gives 1 bytes: (09) " " XmbLookupString gives 1 bytes: (09) " " XFilterEvent returns: False 