What is the OS X equivalent to the free command to show buffer and cache memory? The free command displays the buffer and cache memory on Linux. What is the command to show the equivalent information for an OS X machine?
vm_stat may just show you what you need. As per the man page:


  vm_stat -- show Mach virtual memory statistics


It can show you the following: 


Pages free
Pages active
Pages inactive
Pages speculative
Pages throttled
Pages wired down
Pages purgeable
"Translation faults"
Pages copy-on-write
Pages zero filled
Pages reactivated
Pages purged
File-backed pages
Anonymous pages
Pages stored in compressor
Pages occupied by compressor
Decompressions
Compressions
Pageins
Pageouts
Swapins
Swapouts