Unmounting installation disks on macOS

mount-cleaner.sh

#!/bin/bash

# IMPORTANT ASSUMPTION:
#    YOU DO NOT HAVE ANY OTHER DISKS MOUNTED WITH AN `s1` PARTITION!
# A better way would be to use `diskutil list --plist` and parse the
# plist using ruby/python/javascript/your-language-of-choice

for disk in $(mount | egrep 'disk.+s1' | awk '{print $1}' | sed -e 's_^/dev/__' -e 's_s1$__')
do
  diskutil eject ${disk}
done