wget in rails application- can not allocate memory

I am using wget in my rails application to fetch pages from website and storing some extracted data from them. It starts smoothly but after a while breaks saying can not allocate memory.

Please let me know how to take on this issue??

UPDATE (Code added)

  def self.crawl_my_links
    puts "------------------- looping -------------------------------"
    valid_domains = get_valid_domains
    crawl_links = CrawlLink.all(:conditions => ["server_id = #{Monitoring::SERVER_ID} and crawl_status = 'Assigned'"], :开发者_C百科order => "url").shuffle
    crawl_links.each do |crawl_link|
        url_host = URI.parse(URI.encode(crawl_link.url)).host
        next if crawl_link.url.blank? or !crawl_link.url.starts_with?("http")
        site_domain = Domainatrix.parse(URI.encode(crawl_link.url)).domain
        unless valid_domains.has_key?(site_domain)
          logger.info "Domain - '#{site_domain}' not registered in the system "
          next
        end

        url_protocol = crawl_link.url.split('://').first
        #if not crawl_link.recently_updated?
          html_content = `wget -qO- #{crawl_link.url}`
          update_result(crawl_link, html_content)
          site_url = "#{url_protocol}://#{url_host}"
        #end
        crawl_for_new_links(site_url, html_content)
        crawl_link.update_attribute(:crawl_status, "Available")
    end
    sleep(10)
    Monitoring.delay.assign_links
    puts "++++++++++++++++ DONE ++++++++++++++++++"
  end