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Editorial Team
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Asked: 2026-06-15T16:12:58+00:00

I have the following Sinatra code: post ‘/bucket’ do # determine if this call

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I have the following Sinatra code:

post '/bucket' do
  # determine if this call is coming from filling out web form
  is_html = request.content_type.to_s.downcase.eql?('application/x-www-form-urlencoded')

  # If this is a curl call, then get the params differently
  unless is_html
      params = JSON.parse(request.env["rack.input"].read)
  end

  p params[:name]
end

If I call this using Curl, params has values, but when this is called via a web form, then params is nil and params[:name] has nothing. I spent several hours figuring out why it happens and asked help from other people, but no one could really find out what is going on.

One thing to note is, if I comment out this line:

params = JSON.parse(request.env["rack.input"].read)

then params has the correct value for “web-form” posting.

Actually, the goal is to get the params value if this code is being called by CURL call, so I used:

params = JSON.parse(request.env["rack.input"].read)

but it messed up the web-form posting. Can anyone solve this mystery?

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1 Answer

  1. Editorial Team

    Personally, I’d do it differently, by setting a hidden value in the form, something like:

    <input type="hidden" name="webform" value="true">

    then use it like:

    if (params['webform'])
  # this is a request from the form
else
  # this is a request from Curl
end

    If you see it you know the request came from your web-form. If params['webform'] doesn’t exist didn’t it came from Curl.

    I saved this to a file and ran it with Ruby:

    require 'sinatra'

get '/bucket' do
  params[:name]
end

    Calling the running script using http://localhost:4567/bucket?name=foo displays:

    foo

    in the browser.

    If I modify the source like:

    require 'sinatra'

post '/bucket' do
  params[:name]
end

    restart it and load a simple HTML file:

    <html>
  <body>
    <form name="form" method="post" action="http://localhost:4567/bucket">
      <input type="hidden" name="webform" value="true"></input>
      <input type="input" name="name"></input>
      <input type="submit"></input>
    </form>
  </body>
</html>

    and input foobar and submit it, I see:

    foobar

    in the browser window.

    If I change the script to:

    require 'sinatra'

post '/bucket' do
  if (params[:webform])
    'webform is set'
  else
    'webform is not set'
  end
end

    and restart Sinatra and resubmit the form, I see:

    webform is set

    If I call it using Curl:

    curl --data "name=foo" http://127.0.0.1:4567/bucket

    I see this on the command-line as Curl’s response:

    webform is not set

    If I change the script to:

    require 'sinatra'

post '/bucket' do
  if (params[:webform])
    'webform is set'
  else
    params[:name]
  end
end

    restart the script, and call it with the Curl command again, I see:

    foo

    on the command line.

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