I’ve fairly frequently ran into the issue while scripting a mount action of determining if what I want to mount is already mounted. On Linux, you could parse /proc/mounts, but that’s neither cross-platform, nor is the format of /proc/mounts guaranteed not to change. The same problem exists with parsing the output of the mount command, the format of which not only is not guaranteed to remain the same, it in fact varies greatly between platforms.

To tackle this problem, I looked into how mount gets it’s information. On BSD and friends, it uses a function called getmntinfo(3). On Linux, it uses a function called getmntent(3).

Now that I knew how the different UNIXes that I cared to support got their mount information, I wrote up a program to retrieve and format this mount information.

Know that currently, I only support OS X, but I plan on supporting more operating systems in the future.

You can find the sources for my program on my GitHub page.

Usage: getmntinfo [options] [format]
  -q, --quiet                  Produce no output
  -h, --help                   This help message
  -B, --bsize=SIZE             Fundamental filesystem block size
  -I, --iosize=SIZE            Optimal transfer block size
  -b, --blocks=COUNT           Total data blocks in filesystem
  -F, --bfree=COUNT            Free blocks in filesystem
  -a, --bavail=COUNT           Free blocks avail to non-superuser
  -n, --files=COUNT            Total file nodes in filesystem
  -e, --ffree=COUNT            Free file nodes in filesystem
  -U, --fsid=ID                Filesystem identifier
  -S, --fsid0=ID               Top four bytes of filesystem identifier
  -T, --fsid1=ID               Bottom four bytes of filesystem identifier
  -O, --owner=USER             User that mounted the filesystem
  -g, --flags=FLAGS            Copy of mount exported flags
  -s, --fssubtype=TYPE         Filesystem sub-type (flavor)
  -t, --type=TYPE              Type of filesystem
  -o, --mntonname=DIR          Directory on which mounted
  -f, --mntfromname=NAME       Mounted filesystem

With this program, determining if something is mounted in a script is as simple as

if getmntinfo -t hfs -o / -f /dev/disk0s2 -q; then
	echo "Mounted"
	echo "Not Mounted"
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