Question

I’m trying to connect, using Net::SSH, to a server that immediately after
login executes a script that requires input from user. The user has to enter “1” or “2” and will receive some data via in the terminal afterwards.

My problem is that, although I am able to connect, I can not figure out a way to send “1\n” to the server and to receive the output.

The following code stops at “INFO — net.ssh.connection.session[80906b74]: channel_open_confirmation: 0 0 0 32768”.

Using channel.exec( “1\n” ) instead of channel.send_data unsurprisingly does not work either.

Net::SSH.start('host', 'user', :password => "pass", :auth_methods => ["password"], :verbose => :debug) do |session|

  session.open_channel do |channel|

    channel.on_data do |ch, data|
      STDOUT.print data
    end 

    channel.send_data( "1\n")

  end

  session.loop
end    

Any ideas, anyone?

Thanks in advance

Answer 1

Can you verify that your send_data call is happening after you get the prompt from the remote server? Try constructing a channel.on_data block around your send_data call so that you can verify that you get the expected prompt from the server before you send a response.

You might not want to be using exec here. From the docs for Net::SSH::Connection::Channel:

Sends a channel request asking that
the given command be invoked.

You are wanting to send a text string to reply to a prompt, not invoke a command. The docs show exec being used to send full CLI commands like “ls -l /home”.

Instead, send_data is probably what you want. The docs show it used to send arbitrary text such as channel.send_data("the password\n"). Note, however, this sentence in the docs:

Note that it does not immediately send
the data across the channel, but
instead merely appends the given data
to the channel‘s output buffer,
preparatory to being packaged up and
sent out the next time the connection
is accepting data.

You might want to take a look at channel.request_pty. It appears to be designed for interaction with a console-based application.

If you are trying to (in essence) script an SSH session that you would normally do manually, you may find it easier to use an expect-like interface (for example, a gem like sshExpect might be worth a try).