Update from older Piwik (no replies)

When I do I get Piwik update always the following error message:

There is an error. Please report the message (Piwik 2.4.0) and full backtrace in the Piwik forums (please do a Search first as it might have been reported already!).

Warning: shell_exec(): Unable to execute 'whoami' in x:\Folder\statistic\data\core\Filechecks.php on line 232

Backtrace -->

#0 Piwik\Error::errorHandler(...) called at [:]
#1 shell_exec(...) called at [x:\Folder\statistic\data\core\Filechecks.php:232]
#2 Piwik\Filechecks::getUser(...) called at [x:\Folder\statistic\data\core\Filechecks.php:214]
#3 Piwik\Filechecks::getUserAndGroup(...) called at [x:\Folder\statistic\data\core\Filechecks.php:181]
#4 Piwik\Filechecks::getAutoUpdateMakeWritableMessage(...) called at [x:\Folder\statistic\data\plugins\CoreUpdater\Controller.php:83]
#5 Piwik\Plugins\CoreUpdater\Controller->newVersionAvailable(...) called at [:]
#6 call_user_func_array(...) called at [x:\Folder\statistic\data\core\FrontController.php:507]
#7 Piwik\FrontController->doDispatch(...) called at [x:\Folder\statistic\data\core\FrontController.php:84]
#8 Piwik\FrontController->dispatch(...) called at [x:\Folder\statistic\data\core\dispatch.php:34]
#9 require_once(...) called at [x:\Folder\statistic\data\index.php:47]

There is an error. Please report the message (Piwik 2.4.0) and full backtrace in the Piwik forums (please do a Search first as it might have been reported already!).

Warning: shell_exec(): Unable to execute 'groups | cut -f3 -d" "' in x:\Folder\statistic\data\core\Filechecks.php on line 219

Backtrace -->

#0 Piwik\Error::errorHandler(...) called at [:]
#1 shell_exec(...) called at [x:\Folder\statistic\data\core\Filechecks.php:219]
#2 Piwik\Filechecks::getUserAndGroup(...) called at [x:\Folder\statistic\data\core\Filechecks.php:181]
#3 Piwik\Filechecks::getAutoUpdateMakeWritableMessage(...) called at [x:\Folder\statistic\data\plugins\CoreUpdater\Controller.php:83]
#4 Piwik\Plugins\CoreUpdater\Controller->newVersionAvailable(...) called at [:]
#5 call_user_func_array(...) called at [x:\Folder\statistic\data\core\FrontController.php:507]
#6 Piwik\FrontController->doDispatch(...) called at [x:\Folder\statistic\data\core\FrontController.php:84]
#7 Piwik\FrontController->dispatch(...) called at [x:\Folder\statistic\data\core\dispatch.php:34]
#8 require_once(...) called at [x:\Folder\statistic\data\index.php:47]

Since my web server with Windows runs he does not know these Linux commands whoami and groups. You'd have to install a switch on which the OS is running Piwik. The update runs after successfully

Dany