title: How can I remove lines in one file that exist in another?
body: <p>I have a file I get every day that has 10,000 records in it, 99% of which were in the last day's file. How can I use the macOS command line to remove the lines in the newer file that exist in the previous day's file?</p>
  
  <pre><code>remove_duplicates newfile oldfile
  </code></pre>
  
  <p>These files look like this:</p>
  
  <pre><code>"First Last"\t"email"\t"phone"\t"9 more columns..."
  </code></pre>
  
  <p>Note, I tried <a href="https://stackoverflow.com/questions/42623707/subtracting-lines-in-one-file-from-another-file">this <code>awk</code> solution</a>, but it didn't output anything, even though I confirmed duplicate lines.</p>