Isso deve funcionar para você.
xinput list|grep AT|grep id=|cut -f 2|cut -f 2 -d =
cut
tem uma opção para especificar o delimitador.
xinput list|grep AT|grep id=|cut -f 2
Isso lhe dá id=13
, então passe para outro comando de corte especificando o delimitador como =
Amostra
~$ xinput
⎡ Virtual core pointer id=2 [master pointer (3)]
⎜ ↳ Virtual core XTEST pointer id=4 [slave pointer (2)]
⎜ ↳ Dell Premium USB Optical Mouse id=10 [slave pointer (2)]
⎜ ↳ DualPoint Stick id=15 [slave pointer (2)]
⎜ ↳ AlpsPS/2 ALPS DualPoint TouchPad id=16 [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)]
↳ Power Button id=8 [slave keyboard (3)]
↳ Sleep Button id=9 [slave keyboard (3)]
↳ Dell Dell USB Keyboard Hub id=11 [slave keyboard (3)]
↳ Dell Dell USB Keyboard Hub id=12 [slave keyboard (3)]
↳ Laptop_Integrated_Webcam_FHD id=13 [slave keyboard (3)]
↳ AT Translated Set 2 keyboard id=14 [slave keyboard (3)]
↳ Dell WMI hotkeys id=17 [slave keyboard (3)]
~$ xinput list|grep AT|grep id=|cut -f 2|cut -f 2 -d =
14