Get Bundle name from its executable

Given the path for a bund开发者_如何学Cle, how can I get the name of its executable?

Example:

blahblah.app

should give me

blahblah.app/Contents/MacOS/blahblah

Vice versa will also be okay

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NSString *exe = [[NSBundle bundleWithPath:thePath] executablePath];

You can also use the URL variants if you're on Snow Leopard and want URLs instead.