Running a custom script on USB keyboard hotplug event

arobinson74 · 10-24-2006, 10:57 AM

I have a laptop for work that I use a USB keyboard with usually, but not always. When using the keyboard, I would like to have the NUM lock on, but when using the laptop keyboard, off. I was thinking it would be great to put a script in the hotplug configuration to automatically turn on/off the NUM lock when the keyboard is plugged in/removed.

Here is the script I would like to run (i.e. /etc/hotplug/usb/numlock):

Code:

#!/bin/sh

if [ "${ACTION}" = "add" ] ; then
  numlockx on
else
  numlockx off
fi

I have never setup a hotplug event such as this and was wondering for advice on how to detect if a USB keyboard has been added. Bascially, is there an easy way for a usermap to trap all keyboards. I could set it up for just my work keyboard, but that solution isn't as elegant as trapping all USB keyboards.

If someone could post such an example for a usermap file I would appreciate it.

arobinson74 · 10-24-2006, 11:21 AM

Also, if there is a better way than to use the hotplug capabilities also let me know. I am not having much luck on learning how to register a hotplug script.

arobinson74 · 10-24-2006, 02:42 PM

Okay, got a solution using udev (note that this applies to the debian configuration for file locations):

1) Create/edit a ~/.xsession file. Add the line (this will let the udev script running as root to modify the numlock in X):

Code:

xhost +local:

2) Create the udev rules script file (/etc/udev/usbkeyboard.rules):

Code:

SUBSYSTEM=="input", ENV{PHYSDEVDRIVER}=="usbhid", RUN+="/usr/local/bin/usbkeyboard-addremove"

3) Link the rules script so that it executes:

Code:

cd /etc/udev/rules.d; ln -snf ../usbkeyboard.rules 025_usbkeyboard.rules

4) Create the script that it calls, that does the work (/usr/local/bin/usbkeyboard-addremove):

Code:

#!/bin/sh

NL=/usr/bin/numlockx

if [ "${ID_CLASS}" == "kbd" ] ; then
  if [ "${DISPLAY}" == "" ] ; then
    export DISPLAY=":0.0"
  fi

  if [ "${ACTION}" = "add" ] ; then
    INITTY=/dev/tty[1-8]
    for tty in $INITTY; do
      setleds -D +num < $tty
    done

    ${NL} on
  else
    INITTY=/dev/tty[1-8]
    for tty in $INITTY; do
      setleds -D -num < $tty
    done

    ${NL} off
  fi
fi

Summary:

I had an issue for some reason to get the "add" event to match ENV{ID_CLASS}=="kbd", so that is why it is in the script and not in the rule. This script will not only change the numlock in X but also set the tty's numlock status.

Requirements:
Debian packages: kbd numlockx udev