#!/bin/bash

usage() {
    printf "%s\n" \
        "generate YYYY-MM-DD dates for a range" \
        "usage: $(basename ${0}) -s <start YYYY-MM-DD> -e <end YYYY-MM-DD>"
    exit 1
}

while getopts "s:e:h" opts; do
    case "${opts}" in
        s) start="${OPTARG}";;
        e) end="${OPTARG}";;
        h) usage;;
        *) usage;;
    esac
done

if test "${start}" && test "${end}"; then
    current="${start}"

    while [[ "$current" < "$end" || "$current" == "$end" ]]; do
      printf "%s\n" "${current}"
      current=$(date -I -d "${current} + 1 day")
    done
else
    usage
fi