In Through The Out Door

The first stop is a little utility called opensnoop. Leopard ships with something called DTrace that gives developers and administrators the ability to take a peek at what all running code is doing in a flexible and dynamic way. Giving DTrace the coverage it deserves is beyond a simple blog post, but there are some smaller utilities - like opensnoop - that take advantage of the power of DTrace, but on a more targeted scale which are worthy of a minor exposition.The main purpose of the opensnoop utility is to provide a report of file opens as they occur. Curious as to what really happens when Safari opens a web page? Want to see what files are accessed from that latest program you downloaded? You can find the answers with opensnoop.

[From Hidden Gems In Leopard: OpenSnoop]