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

mount | awk '$3 == "/pa/th" {print $1}'

Empty if is not a mountpoint ^^

Answer 2

Not relying on mount, /etc/mtab, /proc/mounts, etc.:

if [ `stat -c%d "$dir"` != `stat -c%d "$dir/.."` ]; then
    echo "$dir is mounted"
else
    echo "$dir is not mounted"
fi

When $dir is a mount point, it has a different device number than its parent directory.

The benefit over the alternatives listed so far is that you don't have to parse anything, and it does the right thing if dir=/some//path/../with///extra/components.

The downside is that it doesn't mark / as a mountpoint. Well, that's easy enough to special-case, but still.

Answer 3

Using GNU find

find <directory> -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.

Answer 4

if mount | cut -d ' ' -f 3 | grep '^/mnt/disk$' > /dev/null ; then
   ...
fi

EDIT: Used Bombe's idea to use cut.