I took a closer look at your sample code and incorporated an idea from it into mine. And it finally compiled with no errors! Doesn't quite work the way I want it to yet, but I think I'm on the right track now. Thanks again.

Aha! I finally figured it out! My mistake was in adding the executable to the Assets rather than just making it another file. I'm making an app from a shell script because I thought it would be an easy first effort as a teaching tool. My mistake.

Thanks! I had already figured out it was a sandbox problem and got it working on Big Sur Xcode, but it doesn't work on the Beta, and I don't like that solution anyway. I've tried adding the executable into the app, but even after several hours of web searching and Xcode document searching, I can't find a way to get the path of the executable in the app. Everything I've tried just generates more errors. Can you point me to sample code to get the path?