Use send_file to download ini file

Hello,

I need to create a Ruby method to be able to create an ini file and download it afterwards. I manage to create the file with File.open (path, “w”) and File.puts “xxxxx” but when I try to download it with send_file (path) I have an error (NoMethodError: undefined method ` send_data 'for main: Object).
I would like to have an example to download a file.
Regards.