title: How to change file permission from within vi
body: <p>I sometimes open a read-only file in vi, forgetting to do <code>chmod +w</code> before opening it. Is there way to change the file from within vi?</p>
  
  <p>Something like <code>!r chmod +w [filename]</code>?</p>
  
  <p>Is there a shortcut to refer to the currently open file without spelling it's long name?</p>