Just a bash script that use wget, grep and awk to find 404 on a site.
./spider.sh --url https://www.tjenamors.se/x --output tjenamors.se.log
./spider.sh --url https://www.tjenamors.se/x --output tjenamors.se.log --response-code 500
./spider.sh --output tjenamors.se.log --response-code 500
404 is the default response code if no --response-code flag is provided.