I have not had any trouble running macruby through dtrace here, can you send the contents of your dtrace script so that I can compare to my working files?
Thanks to everyone for their suggestions. I was doing the prior work on my office computer (a Mac Pro). I tried the same thing on this computer (a laptop) and it seems to work fine. The dscript I was running wasn't very complicated, it was something like this: -- macruby-dtrace.d -- macruby$target:::method-entry { printf("%s.%s", copyinstr(arg0), copyinstr(arg1)); } macruby$target:::method-return { printf("%s.%s", copyinstr(arg0), copyinstr(arg1)); } The ruby script is: -- macruby-dtrace.rb -- class World def say(message) puts message end end world = World.new world.say('hello') I was able to run this with the command: sudo dtrace -F -s "macruby-dtrace.d" -c "/usr/local/bin/macruby ./macruby-dtrace.rb" On the laptop it works fine. I'll look at the problem again when I get to the office to see if it was some kind of keyboard-chair error. Scott