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

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

# rwbbypid.d

Tracing... Hit Ctrl-C to end.

^C

PID CMD DIR BYTES

20347 bash R 22

11053 dtrace W 32

1532 Xorg W 64

20317 sshd R 86

20347 bash W 87

20317 sshd W 137

1659 mozilla-bin R 213

20334 sshd R 1232

20334 sshd W 1282

11054 cp W 18652

11054 cp R 18652

1532 Xorg R 51112

1659 mozilla-bin W 51261

In the above output, we can see that mozilla-bin with PID 1659 has written

51261 bytes, while Xorg has read 51112 bytes.