title: How to find difference in csv record
body: <p>Is there an algorithm or diff-like utilities to find difference between two csv files?
  Example:</p>
  
  <pre><code>file1
  -------
  key1,value1
  key2,value2
  key3,value3
  key5,value5
  key7,value7
  
  file2
  -------
  key1,value1
  key3,value3
  key4,value4
  key5,value5
  key6,value6
  </code></pre>
  
  <p>With this diff-like utilities it will output 3 types of records:</p>
  
  <ol>
  <li>Records that only exists in file1
  (file1 minus file2 set operation)</li>
  <li>Records that only exists in file2 (file2 minus file1 set operation)</li>
  <li>Records that exists both in file1 and file2 (intersect set operation)</li>
  </ol>