Linux: xmodmap: Set F13 F14 F15 Keys

I have a keyboard that has {F13, F14, F15, F16, F17} Keys. By default, they are mapped to some X11 function keys. (In Ubuntu Linux running xfce.)

F13

keycode 191 = XF86Tools NoSymbol XF86Tools

F14

keycode 192 = XF86Launch5 NoSymbol XF86Launch5

F15

keycode 193 = XF86Launch6 NoSymbol XF86Launch6

F16

keycode 194 = XF86Launch7 NoSymbol XF86Launch7

F17

keycode 195 = XF86Launch8 NoSymbol XF86Launch8

In xfce, the F13 (XF86Tools) key doesn't work for some reason. xev shows the key working fine, but X11 apps doesn't seem to receive any signal when F13 is pressed. F14 and others work fine.

I want {F13, F14, …} to be themselves.

So, i created a file at ~/.Xmodmap with this content:

! 2014-02-19

! set F13 and others to F keys as is

! keycode 191 = XF86Tools NoSymbol XF86Tools
! keycode 192 = XF86Launch5 NoSymbol XF86Launch5
! keycode 193 = XF86Launch6 NoSymbol XF86Launch6
! keycode 194 = XF86Launch7 NoSymbol XF86Launch7
! keycode 195 = XF86Launch8 NoSymbol XF86Launch8

keycode 191 = F13 F13 F13
keycode 192 = F14 F14 F14
keycode 193 = F15 F15 F15
keycode 194 = F16 F16 F16
keycode 195 = F17 F17 F17

With this, all F keys work. I can now proceed to do normal keybinding in emacs or other apps with standard F keys. 〔see Emacs: How to Define Keys〕