Upload of HTML or CSS code programatically

Dear W3C Validator supporters,

I am writing an HTML/CSS editor under Windows and I would like to
incorporate a feature to enable the user to upload the HTML or CSS code in
the editor window to the W3C Validator. I have seen that other editors do
this. Could you please tell me what the command line should look like in
order to upload a file containing HTML or CSS code for validation?

I have already looked at the documentation of the programmatic interface
under http://validator.w3.org/docs/api.html, but that doesn't help me enough
- I would need a specific example of what the command line would look like
for either the uploaded file example or the code fragment example.

My thanks in advance for any help.

Regards

Harry