how to disable touch pad

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$ xinput list
 You will see results similar to

⎡ Virtual core pointer                          id=2    [master pointer  (3)]
⎜   ↳ Virtual core XTEST pointer                id=4    [slave  pointer  (2)]
⎜   ↳ SynPS/2 Synaptics TouchPad                id=15   [slave  pointer  (2)]
⎜   ↳ Logitech USB Receiver                     id=11   [slave  pointer  (2)]
⎜   ↳ Logitech USB Receiver                     id=12   [slave  pointer  (2)]
⎣ Virtual core keyboard                         id=3    [master keyboard (2)]
    ↳ Virtual core XTEST keyboard               id=5    [slave  keyboard (3)]
    ↳ Power Button                              id=6    [slave  keyboard (3)]
    ↳ Video Bus                                 id=7    [slave  keyboard (3)]
    ↳ Video Bus                                 id=8    [slave  keyboard (3)]
    ↳ Sleep Button                              id=9    [slave  keyboard (3)]
    ↳ USB 2.0 UVC VGA WebCam                    id=10   [slave  keyboard (3)]
    ↳ Asus WMI hotkeys                          id=13   [slave  keyboard (3)]
    ↳ AT Translated Set 2 keyboard              id=14   [slave  keyboard (3)]

The touchpad id is 15. To disable it:

$ xinput set-prop 15 "Device Enabled" 0

to re-enable it

$ xinput set-prop 15 "Device Enabled" 1