Howto: Drupal File Upload Form - php

Question

I'm having difficulty figuring out how to write a module with a form that uploads files, in Drupal 6. Can anyone explain this, or point me to a good example/documentation discussing it?
EDIT:
Here is entirely what I am trying to do:
User uploads a .csv
Module reads the first line of the file to get fields
User matches csv fields with db fields
Each csv line is saved as a node (preview it first)
So far, I can do 1, 2, and 4 successfully. But it's unclear exactly how the steps should interact with each other ($form_state['redirect']? how should that be used?), and what the best practices are. And for 3, should I save that as session data?
How do I pass the file data between the various steps?
I know that node_import exists, but it's never worked for me, and my bug requests go ignored.
2nd EDIT: I used this at the start and end of every page that needed to deal with the file:
$file = unserialize($_SESSION['file']);
//alter $file object
$_SESSION['file'] = serialize(file);
I'm not sure it it's best practices, but it's been working.

Answer 1

This is not too difficult, you can see some info here. An example of a form with only a file upload.
function myform_form($form_state) {
$form = array('#attributes' => array('enctype' => 'multipart/form-data'));
$form['file'] = array(
'#type' => 'file',
'#title' => t('Upload video'),
'#size' => 48,
'#description' => t('Pick a video file to upload.'),
);
return $form;
}
EDIT:
Now to save the file use the file_save_upload function:
function myform_form_submit($form, $form_state) {
$validators = array();
$file = file_save_upload('file', $validators, 'path');
file_set_status($file, FILE_STATUS_PERMANENT);
}
2nd EDIT:
There's a lot of questions and ways to do the things you described. I wont go to much into the actual code of how to handle a csv file. What I would suggest is that you use the file id to keep track of the file. That would enable you to make urls that take a fid and use that to load the file you want to work on.
To get from your form to the next step, you can use the #redirect form property to get your users to the next step. From there is really depends how you do things, what you'll need to do.