sharing files but with some prevent of overwriting by my own and others?

Question

I don't want to share one of my files with anyone and I also want to prevent overwriting/modifying the file by my own mistakes (read-only). How should I do that change in the file persmission mode using the chmod utility in octal mode? (Red Hat Linux)

Answer 1

"I don't want to share one of my files with anyone", that's what user accounts are for. Never let anyone login as you.

"I also want to prevent overwriting/modifying the file by my own mistakes (read-only)." Simple, always modify a COPY of the previous original document. This has nothing to do with permissions.