class StaticPagesController < ApplicationController
  require 'open3'
  def mylog
    mycommand = "python app/assets/python/checkUpload.py "

    #file that should be tested
    file_loc = "..."

    #extend command with parameters
    mycommand << "[some parameter] "
    mycommand << ""#{trackfile_loc}""

    #run command to check the file and stream its output
    Open3.popen3(mycommand) do |stdin, stdout, stderr, wait_thr|
      while line=stdout.gets do
        puts line
      end
    end
  end
end

<% provide(:title, "Log") %>
<p>
  <h3><b>Log:</b></h3>
  <%= #here the messages should be inserted %>
</p>

#header missing
message1
message2
message3
#footer missing

class StaticPagesController < ApplicationController
  include ActionController::Streaming
  require 'open3'
  def mylog
    mycommand = "python app/assets/python/checkUpload.py "

    #file location that should be tested
    trackfile_loc = "..."

    #extend command with parameters
    mycommand << "[some parameter] "
    mycommand << ""#{trackfile_loc}""

    #filling it with one message to see if display in view works
    @messages = ["Test"]

    #run command to check the trackfile and stream its output
    Open3.popen3(mycommand) do |stdin, stdout, stderr, wait_thr|
      while line=stdout.gets do
        @messages.push(line)
        #add handle of stderr to file
      end
    end
    render stream: true
  end
end

<% provide(:title, "Log") %>
<p>
  <h3><b>Log:</b></h3>
  <% for line in @messages %>
    <%= puts line %>
  <% end %>
</p>