Set Raspberry Pi overscan on the fly.
Although I do most of my Raspberry Pi messing around on a headless Raspberry Pi via ssh my "gaming" Raspberry Pi is not always conected to the same monitor it was yesterday or will be tomorrow and because all my monitors are different makes and models I often found myself squinting at the monitor to count pixels so I could change the overscan values in /boot/config.txt and then rebooting to find that i'd miscounted and needed to make more changes to the overscan settings and repeating that until I got it just right.
As this was beginning to get annoying I asked the Raspberry Pi kernel guru Dom Cobley if he had an example of how to twiddle the overscan settings after booting and he sent me the code to do that. I've taken his program mailbox.c & made a few little changes to create overscan.c and have wrapped that in a simple bash shell script to make changes to the Raspberry Pi's overscan setting on the fly easy.
Because I need to use mknod to create a special file the script must be run by root or using sudo.
Use the included Makefile to build overscan and then run the set_overscan.sh script. You currently use the arrow/cursor keys to change each setting in turn & the q key to move to the next overscan value to change. The script writes the final values to /boot/config.txt
Russell "ukscone" Davis 2013-03-10