file upload w/ sinatra

app.rb

require 'rubygems'
require 'sinatra'

get '/' do
  @files = Dir['public/*'].map {|f| File.basename(f) }
  erb :index
end

post '/upload' do
  filename = params[:file][:filename]
  file = params[:file][:tempfile]

  File.open("public/#{filename}", 'w') {|f| f.write file.read }

  redirect '/'
end

__END__

@@ index
<h1>File upload!</h1>
<form action='/upload' method='post' enctype='multipart/form-data'>
  <input type='file' name='file' /><br />
  <input type='submit'/><br />
</form>
<hr />
<% @files.each do |file| %>
  <a href='<%= file %>'><%= file %></a>
<% end %>