Description
Like the PHP tempnam() function this method creates a file with a
unique name in the given directory.
Syntax
use Symfony\Component\Filesystem\Filesystem;
$fs = new Filesystem();
$fs->tempnam('/tmp', 'report_'); // '/tmp/report_Um3nlH'
$fs->tempnam('/tmp', 'report_', '.pdf'); // '/tmp/report_Um3nlH.pdf'