Scraping Multiple Pages in Ruby with Nokogiri

Oct 15, 2023 · 3 min read

Web scraping is useful to programmatically extract data from websites. Often you need to scrape multiple pages from a site to gather complete information. In this article, we'll see how to scrape multiple pages in Ruby using the Nokogiri library.

Prerequisites

To follow along, you'll need:

  • Basic Ruby knowledge
  • Ruby installed
  • Nokogiri gem installed:
  • gem install nokogiri
    

    Import Gems

    We'll need the following gems:

    require 'nokogiri'
    require 'open-uri'
    

    Define Base URL

    We'll scrape a blog - https://copyblogger.com/blog/. The page URLs follow a pattern:

    <https://copyblogger.com/blog/>
    <https://copyblogger.com/blog/page/2/>
    <https://copyblogger.com/blog/page/3/>
    

    Let's define the base URL pattern:

    base_url = '<https://copyblogger.com/blog/page/%d/>'
    

    The %d allows us to insert the page number.

    Specify Number of Pages

    Next, we'll specify how many pages to scrape. Let's scrape the first 5 pages:

    num_pages = 5
    

    Loop Through Pages

    We can now loop from 1 to num_pages and construct the URL for each page:

    (1..num_pages).each do |page_num|
    
      # Construct page URL
      url = base_url % page_num
    
      # Code to scrape each page
    
    end
    

    Send Request and Parse HTML

    Inside the loop, we'll open the page URL and parse the HTML using Nokogiri:

    html = open(url)
    doc = Nokogiri::HTML(html)
    

    This gives us a parsed HTML document to extract data from.

    Extract Data

    Now within the loop we can use doc to find and extract data from each page.

    For example, to get all article elements:

    articles = doc.css('article')
    

    We can loop through articles and extract information like title, URL, author etc.

    Full Code

    Our full code to scrape 5 pages is:

    require 'nokogiri'
    require 'open-uri'
    
    base_url = '<https://copyblogger.com/blog/page/%d/>'
    num_pages = 5
    
    (1..num_pages).each do |page_num|
    
      url = base_url % page_num
    
      html = open(url)
      doc = Nokogiri::HTML(html)
    
      articles = doc.css('article')
    
      articles.each do |article|
    
        # Extract data from article
    
        title = article.at_css('h2.entry-title').text
        url = article.at_css('a.entry-title-link')['href']
        author = article.at_css('div.post-author a').text
    
        categories = article.css('div.entry-categories a').map(&:text)
    
        # Print extracted data
        puts "Title: #{title}"
        puts "URL: #{url}"
        puts "Author: #{author}"
        puts "Categories: #{categories.join(', ')}"
        puts
      end
    
    end
    

    This allows us to scrape and extract data from multiple pages sequentially. The code can be extended to scrape any number of pages.

    Summary

  • Use a base URL pattern with %d placeholder
  • Loop through pages with Range#each
  • Construct each page URL
  • Open page and parse HTML with Nokogiri
  • Find and extract data inside loop
  • Print or store scraped data
  • Web scraping enables collecting large datasets programmatically. With the techniques here, you can scrape and extract information from multiple pages of a website in Ruby.

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