How does the go language os.FileMode function convert permissions from integers/octal/??? before setting the flags?

Question

Update: based on the comment and response so far, I guess I should make it explicit that I understand 0700 is the octal representation of the decimal number

Answer 1

So your file mode was changed from the requested 0274 to the actual on-disk 0254. I'll bet that your umask is 0022. Sounds to me like everything is working fine.

Answer 2

os.FileMode only knows about integers, it doesn't care whether the literal representation is octal or not.

The fact that 0700 is interpreted in base 8 comes from the language spec itself:

An integer literal is a sequence of digits representing an integer constant. An optional prefix sets a non-decimal base: 0 for octal, 0x or 0X for hexadecimal. In hexadecimal literals, letters a-f and A-F represent values 10 through 15.

This is a fairly standard way of representing literal octal numbers in programming languages.