Concise Sinatra Amazon S3 Upload Example

app.rb

require "rubygems"
require 'sinatra'
require "aws/s3"

get '/' do
  return %Q{
    <form action="upload" method="post" accept-charset="utf-8" enctype="multipart/form-data">
      <div>
        <input type="file" name="file" value="" id="file">
      </div>
      <div>
        <input type="submit" value="Upload &uarr;">
      </div>
    </form>
  }
end

post '/upload' do
  awskey     = 'mykey'
  awssecret  = 'mysecret'
  bucket     = 'mybucket'
  file       = params[:file][:tempfile]
  filename   = params[:file][:filename]
  AWS::S3::Base.establish_connection!(
    :access_key_id     => awskey,
    :secret_access_key => awssecret
  )
  AWS::S3::S3Object.store(
    filename,
    open(file.path),
    bucket,
    :access => :public_read
  )
  url = "https://#{bucket}.s3.amazonaws.com/#{filename}"
  return url
end

NB: Don't leave your aws key and secret in the committed ruby file, use an external config file (or heroku's config system) to keep sensitive stuff like this out of your repo.

Thanks, exactly what I needed!
For some reason this code does not work with EU based S3 buckets. Had to create an US Standard to get it to work!

works like a charm!