How do I read the UUID of the filesystem covering a specific

	directory from an unprivileged (non-root) process in GNU/Linux?

	Currently, I have the two algorithms at hand:

	??? Find the device holding the filesystem corresponding to the

	  directory specified, by scanning /proc/mounts (or mtab(5)),

	  from the last entry to the first match.  Read blkid(8)'s

	  output (or /etc/blkid.tab), in the hope that the device's UUID

	  has been cached.

	??? Use stat(2) to find the device number corresponding to the

	  directory specified.  Read /etc/blkid.tab (for blkid(8), as of

	  1.0.0, seemingly cannot search by DEVNO), in the hope that the

	  device's UUID has been cached.

	I guess that the latter is better, but wouldn't I be hit with

	any underspecified details?

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FSF associate member #7257