I have a PS/2, two button mouse with a scroll wheel. If I open up any window, I can get the scroll wheel to move the sidebar slider up and down. So the system is definitely detecting the z wheel but I can't figure out how to read the z wheel from within a program.

I get the following when I type
# cat /dev/input/mouse0 | xxd -c1
0000000: 08 .
0000001: 00 .
0000002: 00 .
0000003: 08 .
0000004: 00 .
0000005: 00 .
0000006: 08 .
0000007: 00 .
0000008: 00 .

Each click forward on the mouse gives me a 3 byte packet. How can I switch this to a 4 byte packet so that I get the z wheel information?