How to delete file using drupal_form_submit? I'm using rest services with a custom resource on node update, i want to build the correct variable node structure to delete one of the files on a file image multiple fields.
I removed the file element from the form_state['values'] but isn't working.
I know i can do it manually but is it possible altering form_state['values]  ?
You can use this code in your form submit function 

$file ='public://not_imported_longanswer.csv';
$path = $base_url . '/sites/default/files/not_imported_longanswer.csv';
if (file_exists($file)) {
    file_delete($path);
}