Re: POSIX ruling on up-to-date vs. identical timestamps

[Paul Eggert]

Paul Smith wrote:
> It's trivial to determine the filesystem in POSIX via the
> device ID available from stat()

Yes, that's what the Gnulib utimecmp module does: the idea is that after 
every stat-like operation you look at the file's time stamps to infer 
more information about the containing file system's resolution.

As far as Windows goes, NTFS file systems have 100 ns resolution, and 
FAT file systems are the joker as they have a 2-second resolution for 
last-modified time.

While we're on the topic, perhaps I should warn you that in old buggy 
Linux kernels file time stamps could spontaneously be truncated to file 
system resolution.  According to 
<https://gcc.gnu.org/ml/gcc/2004-04/msg00152.html> this bug was 
introduced into the Linux kernel in 2002; I don't recall when it was 
fixed in Linux, but a few years later POSIX prohibited the buggy behavior.