ruby ssh: interactive command “su”: How further af

I want work on a remote machine within a SSH session:

login on the remote server
su
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 understand that the command has finished and that I want to make my wor on the remote machine?

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

The problem is that su is creating a subshell, and net-ssh is controlling the outermost shell. Its just like running... emacs or something from net-ssh, you can't expect net-ssh to be able to know how to control that inner shell.

So what you have to do is when you detect su was successful, you have to send the data as if you were just typing it in, and then you can read the stdout. Unfortunately, you can't separate the stdout from the stderr since its in a subshell, but you can still get the output.

Instead of using ch.exec after suing successfully, use ch.send_data "command\n" and read the output. Don't forgot to end everything with a ch.send_data "exit\n". (Note that \n has to follow every command to simulate an enter keypress in the console)