title: Check if a program exists from a Fish script
body: <p>How can I check if a program exists within a fish script?</p>
  
  <p>I know that there is no absolute solution with Bash, but using <code>if type PROGRAM &gt;/dev/null 2&gt;&amp;1; then...</code> gave good results.</p>
  
  <p>Is there something similar with fish?</p>