title: Get lines of file1 which are not in file2
body: <p>I have two long, but sorted files. How to get all lines of first file which are not in second file ?</p>
  
  <p><em>file1</em></p>
  
  <pre><code>0000_aaa_b
  0001_bccc_b
  0002_bcc &lt;------ file2 have not that line
  0003_aaa_d
  0006_xxx
  ...
  </code></pre>
  
  <p><em>file2</em></p>
  
  <pre><code>0000_aaa_b
  0001_bccc_b
  0003_aaa_d
  0006_xxx
  ...
  </code></pre>