title: Can't use clear command on terminal (Mac OS X)
body: <p>Every time I try to use the command <code>clear</code> in a terminal window, I can't because:</p>
  
  <p><code>'dtterm': unknown terminal type.</code></p>
  
  <p>or</p>
  
  <p><code>'xterm': unknown terminal type.</code></p>
  
  <p>or</p>
  
  <p><code>'ansi': unknown terminal type.</code></p>
  
  <p>I tried changing the terminal types on the preference menu, but without success. What should I do?</p>