Rails3: linking to offsite mp3 files and have them save to user's hard-drive rather than stream in the browser

Question

I have some very large mp3's stored at a remote location and I presently link to them like so:

= link_to "mp3", "http://website-where-file-is-stored.com/file-123456.mp3"

When a user clicks the link, the file starts to play in the browser. I would like the file to download to the users hard-drive after they click the link.

I've read a number of articles like this one and this one which promote methods that work in different situations to my own.

I have multiple files. Each file is stored on a remote server which does not have a rails app running.

I don't require users to be authorized prior to downloading anything so I don't want my rails app to be called into action in any way as I need to be conservative with my rails processes.

Is this something I need to do in config.ru? Is there a guide or tutorial detailing the best way to do this?

I know that I need to set the Content-Disposition header but as I said, I can't figure out how to do that I do not have a rails app running on the remote server, it's just a bunch of server space.

Answer 1

You can make a controller action somewhere that is dedicated to file downloads.

So, the link_to goes to that action, which somehow knows which file the user wants (either by dropping the entire url into a query variable or some other method appropriate to your application).

That action does a redirect_to http://website-where-file-is-stored.com/file-123456.mp3

When most modern browsers encounter such a situation, they won't render a blank page and start a download -- they will start the download, but then keep the user on the original page with the link_to. Perfect!

To have the file download as an attachment and not render in the browser (if it's a movie or pdf for example), website-where-file-is-stored.com has to serve the file with the header Content-disposition: attachment. See more info here: http://www.boutell.com/newfaq/creating/forcedownload.html

Answer 2

OK, I fixed this by adding the following cgi script to the cgi-bin on my remote server. the script sets the Content-Disposition header. In my case, the script is named "download.cgi".

#!/usr/local/bin/perl -wT

use CGI ':standard';
use CGI::Carp qw(fatalsToBrowser);

my $files_location;
my $ID;
my @fileholder;

$files_location = "../";

$ID = param('ID');

open(DLFILE, "<$files_location/$ID") || Error('open', 'file');
@fileholder = <DLFILE>;
close (DLFILE) || Error ('close', 'file');

print "Content-Type:application/x-download\n";
print "Content-Disposition:attachment;filename=$ID\n\n";
print @fileholder

And instead of doing link_to 'Download', "http://path/to/filename.mp3" I do this:

link_to 'Download' "http://path/to/cgi-bin/download.cgi?ID=filename.mp3"

If you want to use the same script, just bear in mind that the line: $files_location = "../" is a relative path.