title: According to POSIX, when will my writes be visible to other processes?
body: <p>If I open a file with <code>O_CREAT | O_WRONLY</code> and <code>write</code> to it. Does POSIX say 1) other apps can see the file in the folder (without fsync) and 2) be able to see what I wrote?</p>
  <p>Same questions after I do <code>close</code> without an <code>fsync</code>.</p>
  <p>Now finally will it once my program ends? I understand fsync will confirm my write is on disk but I don't need my file to be on disk, I need it to be visible to other processes</p>