title: bash: checks 3 commands if they are installed
body: <p>I wanted to check if 3 commands are installed and if not show a warning message.</p>
  
  <p>I tried that, but it didn't quite work out.
  does anyone have an idea?</p>
  
  <p>Code:</p>
  
  <pre><code>getCurl=`hash curl 2&gt;/dev/null`
  getWget=`hash wget 2&gt;/dev/null`
  getTar=`hash tar 2&gt;/dev/null`
  
  if ! [ "$getCurl" == "" ] ; [ "$getWget" == "" ] ; [ "$getTar" == "" ]; then
      echo "WARNING: curl, wget or tar not installed!"
  fi
  </code></pre>