config.xml

<crontab>
    <jobs>
        <your_module_getfile>
            <schedule><cron_expr>30 2 * * *</cron_expr></schedule>
            <run><model>your_module/observer::getLocalFileForCronJob</model></run>
        </gem_crawler_generate>
    </jobs>
</crontab>

Data.php

// Helper Data

class Your_Module_Helper_Data extends Mage_Core_Helper_Abstract
{
  protected function handleFile($file) {
    // Open file and do whatever you want
  }
}

Observer

class Your_Module_Model_Observer
{
  protected function getLocalFileForCronjob() {
    // Get the file
    $file = ...
    
    // Send it to the helper
    Mage::helper('yourModule')->handleFile($file);
  }
}

TestController.php

class TestCrontroller extends Controller
{
  public function uploadFile() {
    // Get the file
    $file = ...
    
    // Send it to the helper
    Mage::helper('yourModule')->handleFile($file);
    
    return $whatever;
  }
}