Friend yanked out his flash drive while running

Yesterday my friend gave me his flash drive so I could copy some files. I wasn't really sure how to do it but he just said to go command a, command c, and command v onto a folder. I did what he said, but when he saw that it was copying the entire contents of his flash drive rather than the one file he said stop, it's copying the whole thing!

So I clicked on the button that was supposed to stop the copying and it didn't stop right away so he panicked and yanked the flash drive out of my machine while it was still copying. There was an error message that said something like that that was a bad idea! I'm wondering if this did damage to my hard drive? Is there some kind of diagnostic test I can run to find out?

My friend and I are not really speaking now, he is obsessed with the fact that some of his files got copied to my computer. Even though he watched me delete them right in front of him he is upset. I'm more upset, it's a $2000 brand new computer.

It wouldn't do anything to your drive. At worst, it would cause the flash drive to potentially lose data, but if it hasn't then you're fine.

Your friend sounds like a great guy

Anyway, no, it won't do any damage to your computer and probably didn't do any damage to his stuff either.

That's not good practices on how to treat a machine or USB device. Especially ones with important content on them.

Unmounting or ejecting a USB thumb drive that way can lead to corruption.