check_mirrors_headers_at_url

#!/bin/bash

# For the given URL, gather some response headers from a HEAD request against each mirror server
# Example use case: Determine when each mirrors' copy of a file at the given URL was last modified

URL=$1
if [ "x$URL" = "x" ];
then
  echo "Usage: $(basename $0) <URL>"
  echo ''
  echo 'URL should point to a file download.'
  echo ''
  echo 'Example:'
  echo "  $(basename $0) http://ftp.us.debian.org/debian/dists/Debian11.3/main/binary-all/Packages.xz"
  exit 1
fi

FQDN=$(echo "$URL" | sed -E 's;^https?://([^/:]*)[:/].*;\1;i')

# Get list of IP addresses (omitting CNAMEs) and add square brackets around IPV6 IP addresses
IPS=($(dig -t A $FQDN +short | grep -Ev '^[a-zA-Z]'; dig -t AAAA $FQDN +short | grep -Ev '^[a-zA-Z]' | xargs -I '{}' echo '[{}]'))

echo "Testing ${#IPS[@]} mirrors for URL: $URL"
echo

for IP in ${IPS[@]}
do
  echo "  IP: $IP"
  curl -sI --resolve $FQDN:80:$IP --resolve $FQDN:443:$IP $URL | grep -Ei --color=NEVER '^(HTTP|(Server|Last-Modified|Content-Type|Content-Length|Cache-Control|Expires|Etag|X-Cache-Status):)' | xargs -I '{}' echo '    {}'
  echo
done