#!/bin/bash

sleep_sec=0

usage() {
    echo "Usage: $0 [-s sleep_sec] <num>"
}

while getopts :s:h OPT; do
    case $OPT in
        s)  sleep_sec=$OPTARG
            ;;
        h)  usage
            exit
            ;;
        \?) usage 1>&2
            exit 1
            ;;
    esac
done

shift $((OPTIND - 1))

if [ -z "$1" ]; then
    usage 1>&2
    exit 1
fi

set -eu

for i in $(seq $1); do
    sleep $sleep_sec
    echo $(($1 - $i))
done