lizzy مثلية الله ☭ 
does fsync(2) do anything or is it placebo? my use case is making sure a file is properly written when i expect the system to crash within (potentially less than) a second or so
إمي ❄️🏳️⚧️🇵🇸@[email protected] For that you need the O_PONIES flag.
More seriously, it's complicated and very filesystem dependent. See: https://lwn.net/Articles/351422/