Get last post from a static page

last_post.sh

#!/usr/bin/env sh

set -e

set -o errexit

Url=$1

Sleep_Arg=$2

usage() {
    echo "Usage: ./last-post.sh [url] [check interval: default is 1 min]"
    echo "Dependencies: curl, mail, Last-Modified http header"
}





get_http_header_last_modified () {
	curl "$1" --output /dev/null --silent --dump-header - \
		| grep Last-Modified 
}

notify_mail() {
	[ "$1" != "$2" ] \
		&& printf 'Page on address %s updated' "$3" \
		| mail -s 'Page updated' "$USER" 
}

main () {
	Last_Modified_First="$(get_http_header_last_modified "$Url")";

	sleep "$Sleep_Arg"

	Last_Modified_Second="$(get_http_header_last_modified "$Url")";
	
	notify_mail "$Last_Modified_First" "$Last_Modified_Second" "$Url"
}

[ -z "$Sleep_Arg" ] && Sleep_Arg=60

while true;
do
    if [ -z "$Url" ]; then
       usage; exit 0;
    else main;
    fi
done