Run Script During Gnome Logout – How to Guide

It depends which desktop environment you use. The answer that follows is pertaining to Gnome.

GConf is your friend. The actions that are stored for button shortcuts are defined in the gconf configuration database. Two ways for doing so:

1. gconf-editor and then search for 'bindings'. you can here unset the action-button binding;
2. Either search in $HOME/.gconf/ or /etc/gconf/schemas (if you are root) for the name of the button that you are looking for, and modify the assigned button.

It can remove existing actions with this.

Gnome-screensaver emits some signals on dbus when something happens.

Here the documentation (with some examples).

You could write a scripts that runs:

dbus-monitor --session "type='signal',interface='org.gnome.ScreenSaver'"

and that does what you need anytime dbus-monitor prints a line about the screen being locked/unlocked.

Here a bash command to do what you need:

dbus-monitor --session "type='signal',interface='org.gnome.ScreenSaver'" |
  while read x; do
    case "$x" in 
      *"boolean true"*) echo SCREEN_LOCKED;;
      *"boolean false"*) echo SCREEN_UNLOCKED;;  
    esac
  done

Just replace echo SCREEN_LOCKED and echo SCREEN_UNLOCKED with what you need.