OS X: strange -psn command line parameter when launched from Finder

Question

Our OS X Java application which is launched by a shell script inside the MyApp.app bundle gets a strange command line parameter -psn_0_989382 when

Answer 1

Mac OS X assigns a unique process serial number ("PSN") to all apps launched via GUI. It's used for identifying various processes and instances of executables.

There's nothing I can really add to the documentation, so the best thing is to read the ProcessSerialNumber section of the Carbon Process Manager Reference (original Apple link is dead; this is a mirror).

Answer 2

It seems that older applications that used the Carbon API get started with this argument. If the application was already updated to a version not using Carbon any more, you can unregister the application from the LaunchServices database by:

/System/Library/Frameworks/CoreServices.framework/Versions/A/Frameworks/LaunchServices.framework/Versions/A/Support/lsregister -u /Applications/AppName.app/

After this it can be re-launched from Finder to register the new version. Then it should not get this argument any more.