The powerd(8) daemon acts upon power management events posted by the kernel's power management facility, translating the events into a script name and arguments. These scripts are found in /etc/powerd/scripts/.

The lid_switch script is called on lid-open and -close events. An event of pressed means the lid has been closed, and released that the lid has been opened.

The following lid_switch uses xset(1) to forcibly blank the screen on lid-close, and refresh the screen on lid-open:

    # arguments passed by powerd(8): device event
    # debugging: exec 1>>/tmp/lid_switch.log 2>&1
    if [ -z "$DISPLAY" ]; then export DISPLAY=:0; fi
    case "${2}" in
     pressed)    # lid closed
       /usr/X11R6/bin/xset dpms force off
       exit 0
     released)   # lid opened
       # need to both force dpms and reset screensaver
       /usr/X11R6/bin/xset dpms force on
       /usr/X11R6/bin/xset s reset
       exit 0
       logger -p warning "${0}: unsupported event ${2} on device ${1}" >&1
       exit 1