How to test if a given path is a mount point

Question

Suppose do you want test if /mnt/disk is a mount point in a shell script. How do you do this?

Answer 1

Using GNU find

find  -maxdepth 0 -printf "%D" 

will give the device number of the directory. If it differs between the directory and its parent then you have a mount point.

Add /. onto the directory name if you want symlinks to different filesystems to count as mountpoints (you'll always want it for the parent).

Disadvantages: uses GNU find so less portable

Advantages: Reports mount points not recorded in /etc/mtab.