The following is a demonstration of the rwbypid.d script,


Here we run it for a few seconds then hit Ctrl-C,

   # rwbypid.d
   Tracing... Hit Ctrl-C to end.
   ^C
      PID CMD                       DIR    COUNT
    11131 dtrace                      W        2
    20334 sshd                        W       17
    20334 sshd                        R       24
     1532 Xorg                        W       69
     1659 mozilla-bin                 R      852
     1659 mozilla-bin                 W     1128
     1532 Xorg                        R     1702

In the above output, we can see that Xorg with PID 1532 has made 1702 reads.