webcmp.sh

#!/usr/bin/env bash

STORAGE_FILE="webpage.sum"

init() {
	while [[ "$1" == -* ]]; do
		case "$1" in
			-s|--storage)
				STORAGE_FILE="$2"
				shift 2
				;;
		esac
	done

	URL="$1"
	echo -n > "$STORAGE_FILE"
	echo "$URL" >> "$STORAGE_FILE"
	curl -s "$URL" | cksum -a sha256 >> "$STORAGE_FILE"
	printf 'Initialized webcmp storage file "%s"\n' "$STORAGE_FILE"
}

refresh() {
	OVERWRITE=0

	while [[ "$1" == -* ]]; do
		case "$1" in
			-o|--overwrite)
				OVERWRITE="1"
				shift 1
				;;
			-s|--storage)
				STORAGE_FILE="$2"
				shift 2
				;;
		esac
	done

	URL="$(head -n 1 "$STORAGE_FILE")"
	
	echo -n > "$STORAGE_FILE.new"
	echo "$URL" >> "$STORAGE_FILE.new"
	curl -s "$URL" | cksum -a sha256 >> "$STORAGE_FILE.new"
	if cmp -s "$STORAGE_FILE" "$STORAGE_FILE.new"; then 
		echo "No news"; 
	else 
		echo "Webpage changed!";
	fi

	if [[ "$OVERWRITE" = "1" ]]; then
		mv "$STORAGE_FILE.new" "$STORAGE_FILE";
	else
		rm "$STORAGE_FILE.new";
	fi
}

case "$1" in
	init)
		shift 1
		init $*
		;;
	refresh)
		shift 1
		refresh $*
		;;
	*)
		printf 'Invalid subcommand "%s"\n' "$1"
		exit 1
		;;
esac