We're sure you're sick of hearing about repairing permissions -- its merits and shortcomings and whether or not it should be part of your regular maintenance routine (as recommended by Apple).
Ted's conclusions from yesterday, and findings from our earlier coverage of the problem reveal a salient point: Repair permissions is a valid troubleshooting routine in a variety of situations, evidenced by a multitude of real-world examples.
That said, a bit of clarification is due.
We did some additional investigation of what exactly repair permissions does, and I used the fs_usage command to see what files were touched by the Disk Utility and DiskManagementTool processes, via the following Terminal command (the numbers 1407 and 1408 correspond to the process ID numbers of DiskManagementTool [which performs the permissions checking/repairing] and Disk Utility):
- sudo fs_usage 1407, 1408 > fileusage
What we found was the that literally thousands of files are touched (scanned, read or written to) -- but, it doesn't look like any third-party application receipts (outside of those listed in the Essentials.pkg, AdditonalEssentials.pkg, etc.) are scanned. In other words, the Repair permissions process doesn't scan, say, Library/Receipts/OnyX.pkg, which is the shareware utility OnyX's receipt file.
That's not to say, however, that third-party application problems can't be dependent on one or more of the thousands of files -- which include key system components like files in /Library/Frameworks and other locations -- touched by Disk Utility. So saying that Disk Utility "doesn't touch" third-party applications, nor enact any effect on their operation is naive at best, misinformation at worst.
Further, as noted in a previous MacFixIt article, there are other operations that Disk Utility performs --- like re-creating the /tmp directory -- that can resolve troubleshooting issues.
Again, regardless of the exact tasks performed by Repair Permissions, it has been proven in a number of field demonstrations to solve issues with application (Apple and third-party) launching, improper operation and more. As such, you will continue to see the process mentioned in future MacFixIt troubleshooting procedure recommendations when it is applicable.