Howto: Drupal File Upload Form

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:

1. User uploads a .csv
2. Module reads the first line of the file to get fields
3. User matches csv fields with db fields
4. 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.