Check the SSL expiration for a given site using openssl..

check_ssl_expiry.sh

check_ssl_expiry() {
  local SERVER="$1"
  if [[ -z "$SERVER" ]]; then
    echo "Usage: check_ssl_expiry <server>"
    return 1
  fi

  local EXPIRY_DATE
  EXPIRY_DATE=$(echo | openssl s_client -servername "$SERVER" -connect "$SERVER:443" 2>/dev/null \
    | openssl x509 -noout -enddate \
    | cut -d= -f2)

  if [[ -n "$EXPIRY_DATE" ]]; then
    echo "SSL certificate for $SERVER expires on: $EXPIRY_DATE"
  else
    echo "Failed to retrieve certificate for $SERVER"
    return 2
  fi
}