[TYPO3-mvc] How do I execute an external program from extbase?

[mario chiari]

Hello

I would like to implement something like the following lines of code:

        // Opening the pdflatex process
	// changing directory to make pdflatex write the aux, log and pdf file
in the workfile directory
	$command = "cd " . t3lib_extMgm::siteRelPath("pdf_export") .
"workfiles; " . $cObj['pdflatexPath'] . "pdflatex&> texerror";
	$f=popen($command, "w"); 

(from pdf_export
http://typo3.org/extensions/repository/view/pdf_export/current/info/class.tx_pdf_export.php/)

How do you do something like that in extbase? 
Is there something I may look at and hack?

Thanks a lot
mario