dtrace is really cool. Apple even put a few utility dtrace scripts into /usr/bin.

For those of us who are missing ktrace (I am), there's dtruss. There's dapptrace which traces user and library functions an application calls (but doesn't work for me), and dappprof for profiling user and library code. Also, there's diskhits, which outputs the times and locations a file was actually read and written on the disk (doesn't count cache misses).

I think that's pretty awesome - replacing 4-ish utilities with one that's sufficiently extensible. (-:

These utilities (dtruss, dapptrace, dappprofile, diskhits) come with man pages; check them out with "man utility-name" on the terminal.

...several, actually. There are a /lot/ more utilities packaged, I listed only the ones that I discovered in the last few days. To discover more, it helps to know that these utilities have man pages and these have "DTrace" in their summary line:

the command "man -k dtrace" on the Terminal will display these man pages together with their summary.