Show who is accessing a disk drive in real time

[Ray Lauff]

I would like to be able to see who is accessing a device (read: a disk) on
my sun systems.  What I would like is a to write a little C hack to
just display on a screen or to a file the date, time, and user name of
the person using the device.

My question is--this being my first attempt at "system" programming on the
sun, where should I start?  Is there a manual which tells me where to look
in memory (i have root priv) to see who is accessing it?

Thanks for any help.