Comment by nh2

I don't understand your point.

If you construct scenarios where the subprocess you call daemonizes and outlives your program, then there of course there isn't any convention your code should follow because your code isn't in charge -- it could follow whatever logic and it wouldn't matter. So then there's no possibly correct solution /anyway/.

The question of the original post is "What convention should programmers use for fsyncing files in standard scenarios?", for example, "Should cat fsync?". As the post says: "Who should be responsible?"

I'm suggesting an answer to that.

I don't understand the point of "but what if `cat` double-forks". It doesn't, and surely, if you're calling a program that daemonizes, you know that it does, and that the rules about who needs to fsync file descriptors will necessary change then.