title: ggsave error "cannot open file"
body: <p>I am running <code>ggsave('plot.pdf')</code> and get this error:</p>
  
  <pre><code>Error in grDevices::pdf(..., version = version) :
    cannot open file 'plot.pdf'
  </code></pre>
  
  <p>Even when I don't have plot.pdf open.  I am working on a NFS. If I ggsave to a new file, and then run ggsave again to the same path, it will overwrite the file successfully.  However, if I open and close the file before running ggsave to the same path, I get the above error.  Any thoughts on why this would be happening?  </p>