title: Saving return value of "execute" function into variable vimscript
body: <p>In vimscript, I cannot find the way of saving the return value of the <code>execute</code> function into a variable.</p>
  
  <p>I would like to do the following:</p>
  
  <pre><code>let s = execute(":!echo dani")
  echo s
  </code></pre>
  
  <p>This should return: <code>dani</code></p>
  
  <p>Vim doesn't accept this. In my setup (using vim-airline and other UI plugins) the screen blanks all content and upon a key press it goes back to normal.</p>
  
  <p>Is it possible in vimscript to save into a variable the return of either a function call, or conversely the return of the <code>execute</code> function?</p>
  
  <p>Thanks SO</p>