Sends the file by streaming it 4096 bytes at a time. This way the whole file doesn’t need to be read into memory at once. This makes it feasible to send even large files.

Be careful to sanitize the path parameter if it coming from a web page. send_file(params[:path]) allows a malicious user to download any file on your server.

Options:

• :filename - suggests a filename for the browser to use. Defaults to File.basename(path).
• :type - specifies an HTTP content type. Defaults to ‘application/octet-stream’.
• :disposition - specifies whether the file will be shown inline or downloaded. Valid values are ‘inline’ and ‘attachment’ (default).
• :stream - whether to send the file to the user agent as it is read (true) or to read the entire file before sending (false). Defaults to true.
• :buffer_size - specifies size (in bytes) of the buffer used to stream the file. Defaults to 4096.
• :status - specifies the status code to send with the response. Defaults to ‘200 OK’.
• :url_based_filename - set to true if you want the browser guess the filename from the URL, which is necessary for i18n filenames on certain browsers (setting :filename overrides this option).

The default Content-Type and Content-Disposition headers are set to download arbitrary binary files in as many browsers as possible. IE versions 4, 5, 5.5, and 6 are all known to have a variety of quirks (especially when downloading over SSL).

Simple download:

send_file '/path/to.zip'

Show a JPEG in the browser:

send_file '/path/to.jpeg', :type => 'image/jpeg', :disposition => 'inline'

Show a 404 page in the browser:

send_file '/path/to/404.html', :type => 'text/html; charset=utf-8', :status => 404

Read about the other Content-* HTTP headers if you’d like to provide the user with more information (such as Content-Description). www.w3.org/Protocols/rfc2616/rfc2616-sec14.html#se...

Also be aware that the document may be cached by proxies and browsers. The Pragma and Cache-Control headers declare how the file may be cached by intermediaries. They default to require clients to validate with the server before releasing cached responses. See www.mnot.net/cache_docs/ for an overview of web caching and www.w3.org/Protocols/rfc2616/rfc2616-sec14.html#se... for the Cache-Control header spec.

Source Code

# File action_controller/streaming.rb, line 64
def send_file(path, options = {}) #:doc:
  raise MissingFile, "Cannot read file #{path}" unless File.file?(path) and File.readable?(path)

  options[:length]   ||= File.size(path)
  options[:filename] ||= File.basename(path) unless options[:url_based_filename]
  send_file_headers! options

  @performed_render = false

  if options[:x_sendfile]
    logger.info "Sending #{X_SENDFILE_HEADER} header #{path}" if logger
    head options[:status], X_SENDFILE_HEADER => path
  else
    if options[:stream]
      render :status => options[:status], :text => Proc.new { |response, output|
        logger.info "Streaming file #{path}" unless logger.nil?
        len = options[:buffer_size] || 4096
        File.open(path, 'rb') do |file|
          while buf = file.read(len)
            output.write(buf)
          end
        end
      }
    else
      logger.info "Sending file #{path}" unless logger.nil?
      File.open(path, 'rb') { |file| render :status => options[:status], :text => file.read }
    end
  end
end