ruby ssh: interactive command "su": How further after successfull logged in?

Question

Hi I want work on a remote maschine within an ssh session:

1. login on the remote server
2. su
3. make my work

With my script a can do step 1 and 2 works. While executing the su command, I can send the password, and got the answer I'm expecting (

on_data: data = gis@v04ree:~> got gis@v04ree:~>

But then, what should I do? I'm sitting on my channel, nothing happens. How can I make the channel to understand, that the command has finished and that I want to make my wor on the remote machine?

Thanks for answers

Christian

require 'net/ssh'
require 'net/sftp'

class Connection
  def connect
host = 'host'
user = 'user'

#1. Login
Net::SSH.start(host, user) do |ssh|
  puts ssh.exec!("whoami")
  #2. su
  begin
    puts(su(ssh, "otherUser", "otherPwd"))
  rescue Exception => e
    puts e
  end
  #3. work
  puts "logged in as " << ssh.exec!("whoami")
  ssh.close
end
end

def su(ssh, user, pwd)
 channel = ssh.open_channel do |ch|
  channel.request_pty do |ch, success|
    raise "Could not obtain pty (i.e. an interactive ssh session)" if !success
  end

  command = "su - #{user}\n"
  puts "command = #{command}"
  channel.exec command do |ch, success|
    raise "could not execute command" unless success

    # "on_data" is called when the process writes something to stdout
    ch.on_data do |c, data|
      puts "on_data: data = "+data
      if data == "Password: "
        puts "Password request"
        channel.send_data "#{pwd}\n"
      end
      if data == "gis@v04ree:~> "
        #logged in as gis
        puts "got gis@v04ree:~>"
        #and now? What's next?
        #channel.eof! # <-doesn't work

        ch.exec "ls" do |ch, success| #<- doesn't work either: success is false
          unless success
            puts "alas! the command could not be invoked!"
          end
        end
      end
    end
    #wouldn't be called
    ch.on_extended_data do |c, type, data|
      puts "on_extended_data: data = #{data}"
    end
  end #end su - gis

  #which statement
  ssh.loop
  #channel.wait
end
end
end #class end


Connection.new.connect