Rack::Request – how do I get all headers?

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The HTTP headers are available in the Rack environment passed to your app:

HTTP_ Variables: Variables corresponding to the client-supplied HTTP request headers (i.e., variables whose names begin with HTTP_). The presence or absence of these variables should correspond with the presence or absence of the appropriate HTTP header in the request.

So the HTTP headers are prefixed with “HTTP_” and added to the hash.

Here’s a little program that extracts and displays them:

require 'rack'

app = Proc.new do |env|
  headers = env.select {|k,v| k.start_with? 'HTTP_'}
    .collect {|key, val| [key.sub(/^HTTP_/, ''), val]}
    .collect {|key, val| "#{key}: #{val}<br>"}
    .sort
  [200, {'Content-Type' => 'text/html'}, headers]
end

Rack::Server.start :app => app, :Port => 8080

When I run this, in addition to the HTTP headers as shown by Chrome or Firefox, there is a “VERSION: HTPP/1.1” (i.e. an entry with key “HTTP_VERSION” and value “HTTP/1.1” is being added to the env hash).

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