title: Unix Terminal error - "cp: the -R and -r options may not be specified together."
body: <p>I have bash script running on os-x unix with above command:</p>
  
  <p><code>cp -avr source destination</code></p>
  
  <p>The result is following error:</p>
  
  <p><code>cp: the -R and -r options may not be specified together.</code></p>
  
  <p>When I remove the <code>a</code> flag it works OK without errors.</p>
  
  <p>Why and what is the meaning of this error?</p>
  
  <p>Thanks,</p>