I've thoroughly read through the gdisk man page and the author's walkthrough found here http://www.rodsbooks.com/gdisk/walkthrough.html
I'm wondering if there is a repository of error codes out there for gdisk. When I first started using gdisk I'd naturally make mistakes and see error codes:
GPT fdisk (gdisk) version 1.0.3 Type device filename, or press <Enter> to exit: I Problem opening I for reading! Error is 2. The specified file does not exist!
Simple mistake right, I typed in something that doesn't exist.
Then the second mistake:
GPT fdisk (gdisk) version 1.0.3 Type device filename, or press <Enter> to exit: /dev/sda Problem opening /dev/sda for reading! Error is 13. You must run this program as root or use sudo!
This might be a silly question, but I'm curious if this is the 13th error what would the other 11 errors be that I haven't made a mistake for yet?
I did find one additional error code in an apple forum https://discussions.apple.com/thread/7584206
Here error code 1 seems to relate to gdisk encountering bios/mbr installations.