shell-base/modules/utility/filesystem.mod

#!/bin/bash
# must be json as a string, depends on jq
mounted () {
 mountpoint "$1" &> /dev/null && echo yes || return 1
}

# peals back sub-directories until if finds a mountpoint
find_mountpoint () {
  local dir=$1
  if [[ ! $dir = "/" ]]; then
    # echo trying $dir for mountpoint
    [[ $(mounted $dir) ]] && echo $dir || find_mountpoint "$(dirname $1)"
  else
    return 1
  fi
}