see if a directory or file is a mountpoint
mountpoint [-d|-q] directory | filemountpoint -x device
mountpoint checks whether the given directory or file is mentioned in the /proc/self/mountinfo file.
-d,--fs -devno Show the major/minor numbers of the device that is mounted on the given directory.
-q,--quiet Be quiet - don't print anything.
-x,--devno Show the major/minor numbers of the given blockdevice on standard output.
-V,--version Display version information and exit.
-h,--help Display help text and exit.
Zero if the directory or file is a mountpoint, non-zero if not.
LIBMOUNT_DEBUG=all enables libmount debug output.
The util-linux mountpoint implementation was written from scratch for libmount. The original version for sysvinit suite was written by Miquel van Smoorenburg.
The mountpoint command is part of the util-linux package and is available from https://www.kernel.org/pub/linux/utils/util-linux/.
Karel Zak <email@example.com>