How do I programmatically apply a Drupal input filter?

I am currently exporting Drupal data to an external source (XML) programmatically. However, I want the data to run through the site's default Input Format (the filter that runs before user content is displayed on the website) before being written to f开发者_如何学JAVAile.

How do I programmatically apply a Drupal input filter? Is there a specific function call or hook for this purpose? If so, links/advice would be most appreciated.

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You are looking for check_markup (D6), check_markup (D7)