title: Measure disk space of certain file types in aggregate
body: <p>I have some files across several folders:</p>
  
  <pre><code>/home/d/folder1/a.txt
  /home/d/folder1/b.txt
  /home/d/folder1/c.mov
  /home/d/folder2/a.txt
  /home/d/folder2/d.mov
  /home/d/folder2/folder3/f.txt
  </code></pre>
  
  <p>How can I measure the grand total amount of disk space taken up by all the .txt files in /home/d/?</p>
  
  <p>I know <strong>du will give me the total space of a given folder</strong>, and <strong>ls -l will give me the total space of individual files</strong>, but what if I want to add up all the txt files and just look at the <strong>space taken by all .txt files in one giant total</strong> for all .txt in /home/d/ including both folder1 and folder2 and their subfolders like folder3?</p>