#!/bin/bash

dflag=
iflag=
oflag=
while getopts 'dio:' OPTION
do
  case $OPTION in
    d)  dflag=1
        ;;
    i)  iflag=1
        ;;
    o)  oflag=1
        oval="$OPTARG"
        if [ ! -d "$oval" ]; then
          printf 'Option -o "%s" is not a directory\n' "$oval"
          exit 2
        fi
        ;;
    ?)  printf "Usage: %s [-d] [-i] [-o /path/to/output]\n" $0 >&2
        exit 2
        ;;
  esac
done

if [ "$dflag" ]; then
  printf "Option -d specified\n"
fi
if [ "$iflag" ]; then
  printf "Option -i specified\n"
fi
if [ "$oflag" ]; then
  printf 'Option -o "%s" specified\n' "$oval"
fi