How to trace Objective-C messages with dtrace in OSX

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First, find the process id:

$ ps -ef|grep Grab
  501 50335   319   0   0:02.11 ??         0:04.40 /Applications/Utilities/Grab.app/Contents/MacOS/Grab -psn_0_7309048

The pid is 50335 so create a D program that captures the Objective-C calls for that process:

objc50335:::entry
{
   printf("%s %s\n", probemod, probefunc);
}

Save the code in a file called grab.trace.d and start tracing by executing this command:

sudo dtrace -s grab.trace.d > trace.log

Output is sent to the trace.log file.

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