[MacOSX] Troubleshooting with dtruss

In a previous post, I looked at how things could go wrong in the file ~/pymel.log wasn’t accessible. On Windows, this was fairly easy to track down using Process Monitor:

On Mac OS X, I had to use dtruss. For example, I ran this command to trace the syscalls of the Maya Render command:

sudo dtruss -f -t open_nocancel -n Render 2> /var/tmp/mtoarender.log

When the render job failed, I checked the log file, and found this line:

11668/0x35deb: open_nocancel("/Users/stephenblair/pymel.log\0", 0x601, 0x1B6) = -1 Err#13

One important gotcha: if you repeat the render, you won’t find any mention of pymel error in the dtruss output. My guess is that at that point, the Render command ends up going through the file system cache, so dtruss doesn’t see the attempt to find pymel.log.

Here’s a quick summary of the dtruss command I showed above:

  • Use sudo to run dtruss, because it needs additional privileges.
  • -f tells dtruss to follow any child processes (like mayabatch) launched by Render
  • -t filters the trace for open_nocancel system calls
  • -n tells dtruss to trace the process named “Render”
  • 2> /var/tmp/mtoarender.log redirects the dtruss output to a file

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