title: how to Extract tar Files?
body: <p>i want to extract tar file.
  but, terminal is error output.</p>
  
  <p>i want to solve the error.
  could you help me?</p>
  
  <p>this is terminal cmd</p>
  
  <pre><code>$ tar xvzf test.tar  -C /dir/    
  </code></pre>
  
  <p>this is error output</p>
  
  <pre><code># gzip: invalid magic
  # tar: Child returned status 1
  # tar: Error exit delayed from previous errors
  </code></pre>