protected static function readUpdateToken( $tokenFile )
    {
        $sys = eZSys::instance();
        $updateViewLogPath = $sys->varDirectory() . "/" . eZPerfLoggerINI::variable( 'FileSettings', 'LogDir', 'site.ini' ) . "/" . $tokenFile;
        if ( is_file( $updateViewLogPath ) )
        {
            // nb: we need the newline at the end of the saved line for a proper comparison
            $lines = file( $updateViewLogPath, FILE_SKIP_EMPTY_LINES );
            return isset( $lines[2] ) ? $lines[2] : false;
        }
        return false;
    }