The vm_stat command in Mac OS X will show you the free, active, inactive, wired down, copy-on-write, zero filled, and reactivated pages for virtual memory utilization. You will also see the pageins as well as pageouts. If you wish to write these statistics routinely then you can use the vm_stat command followed by an integer. For example, to see the virtual memory statistics every 5 seconds: vm_stat 5