How to get cpu utilization through code with least overhead?

Hi, I need to write code to get and record the cpu utilization in certain interval with the least overhead. Could anybody please advise me on how to proceed ? I tried looking at the code for "top" command to see how it works but couldn't figure out much. I don't want to write script that uses commands and pulls out the results as I want the overhead to be as small as possible. Thanks Vaibhav Jain