Advanced Mac OS X Programming: The Big Nerd Ranch Guide

Functions

D provides a number of functions you can use in your action scripts. Here is a sampling.

printf	Standard C-style printf function
trace	Displays its argument, using a default format based on the type. Also appends a newline for you.
printa	Print aggregate values, described in more detail below.
ustack	Print the user level stack trace. If the process exits or is killed before the DTrace experiment has completed, DTrace might not be able to resolve the program counter, so you will get hex values rather than symbolic values.
exit	Terminate execution early. Otherwise, you have to type Control-C to quit.
copyin, copyinstr	DTrace scripts execute in kernel scope. Consider probing a system call like write(), which takes a pointer to a buffer with ...