The following is a demonstration of the readbytes.d script, Here the readbytes.d script is run for a few seconds, then Ctrl-C is hit, # readbytes.d dtrace: description 'sysinfo:::readch ' matched 4 probes ^C mozilla-bin 16 gnome-smproxy 64 metacity 64 dsdm 64 wnck-applet 64 xscreensaver 96 gnome-terminal 900 ttymon 5952 Xorg 17544 In this interval the Xorg command has successfully read 17.5 Kb, while ttymon has read 5952 bytes.