# How to make Rails send a file that is being written

**URL:** <https://www.ruby-forum.com/t/how-to-make-rails-send-a-file-that-is-being-written/86643>\
**Category:** Rails\
**Created:** [February 24, 2007, 12:13am UTC](https://www.ruby-forum.com/t/how-to-make-rails-send-a-file-that-is-being-written/86643 "2007-02-24T00:13:42Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![remis](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/r/54ee81/32.png) [@remis](https://www.ruby-forum.com/u/remis)\
**Post date:** [February 24, 2007, 12:13am UTC](https://www.ruby-forum.com/t/how-to-make-rails-send-a-file-that-is-being-written/86643/1 "2007-02-24T00:13:42Z")

</div>

I’m trying to build a simple proxy to Amazon S3 that would allow a  
client to request a url that gets mapped to a S3 Object by Rails and  
streamed back to the client.  
For S3 integration, I use the highly recommended gem AWS::S3  
([http://amazon.rubyforge.org/](http://amazon.rubyforge.org/)), and to send a file, I simply use the  
send\_file function.

The concept works BUT the I can’t get the file to be sent as it’s been  
downloaded. Even better would be to download the file to memory instead  
of the disk, I’m really not familiar with Ruby’s IO Class though… If  
anyone has a suggestion…

I first tried this:

# download the file entirely then uploads it to the client

send\_data AWS::S3::S3Object.value ‘object\_name’, ‘bucket\_name’

Then I figured I needed to use the streaming feature of AWS::S3

# Start a thread that downloads the file in the background

Thread.start do  
open(‘/tmp/tempfile’, ‘w’) do |file|  
AWS::S3::S3Object.stream(‘object\_name’, ‘bucket\_name’) do |chunk|  
file.write chunk  
end  
end  
end

## Then send the file as it’s being written.

send\_file “/tmp/tempfile”, :stream =\> true

This doesn’t work, the sent file is often between 0 and 4 bytes… not  
cool.

I’m guessing I could put it all together, I dont know how.

Here’s the send\_file function that could be overwritten:

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)
send_file_headers! options

@performed_render = false

if options[:stream]
  render :text => Proc.new { |response, output|
    logger.info "Streaming file #{path}" unless logger.nil?
    len = options[:buffer_size] || 4096
    File.open(path, 'rb') do |file|
      if output.respond_to?(:syswrite)
        begin
          while true
            output.syswrite(file.sysread(len))
          end
        rescue EOFError
        end
      else
        while buf = file.read(len)
          output.write(buf)
        end
      end
    end
  }
else
  logger.info "Sending file #{path}" unless logger.nil?
  File.open(path, 'rb') { |file| render :text => file.read }
end

```

end

Please, any idea anyone?

---

<div class="post-metadata">

**Author:** ![remis](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/r/54ee81/32.png) [@remis](https://www.ruby-forum.com/u/remis)\
**Post date:** [February 25, 2007, 10:01am UTC](https://www.ruby-forum.com/t/how-to-make-rails-send-a-file-that-is-being-written/86643/2 "2007-02-25T10:01:20Z")

</div>

Remi Gabillet wrote:

> anyone has a suggestion…  
> end
> 
> ## Then send the file as it’s being written.
> 
> send\_file “/tmp/tempfile”, :stream =\> true
> 
> This doesn’t work, the sent file is often between 0 and 4 bytes… not  
> cool.

Try using a ruby IO.pipe object instead of the tempfile.

–  
We develop, watch us RoR, in numbers too big to ignore.