$config['upload_path'] = './파일경로'; 
     $config['allowed_types'] = '*';
     
     if (!is_dir($config['upload_path'])) {
      mkdir($config['upload_path']);
     }
    $this->load->library('upload', $config);
    
    if ( $this->upload->do_upload('fileToUpload') ) {
     $file_data = $this->upload->data();
     $file_data  = $file_data['file_name'];
    }