Ruby Net::SSH get Exit Status in PTY

Question

I'm trying to write in some functionality into the Net::SSH::Telnet Library for a project of mine. Specifically I need to be able to read the exit-status of any command that I write.

Here's the Original source from the Net::SSH::Telnet Library that I'm modifying

@buf = ""
@eof = false
@channel = nil
@ssh.open_channel do |channel|
  channel.request_pty { |ch,success|
    if success == false
      raise "Failed to open ssh pty"
    end
  }
  channel.send_channel_request("shell") { |ch, success|
    if success
      @channel = ch
      waitfor(@options['Prompt'], &blk)
      return
    else
      raise "Failed to open ssh shell"
    end
  }
  channel.on_data { |ch,data| @buf << data }
  channel.on_extended_data { |ch,type,data| @buf << data if type == 1 }
  channel.on_close { @eof = true }
end
@ssh.loop

And now here are the changes I have made:

@stderr = ""
@exit_code = nil
@buf = ""
@eof = false
@channel = nil
@ssh.open_channel do |channel|
  channel.request_pty { |ch,success|
    if success == false
      raise "Failed to open ssh pty"
    end
  }
  channel.send_channel_request("shell") { |ch, success|
    if success
      @channel = ch
      waitfor(@options['Prompt'], &blk)
      return
    else
      raise "Failed to open ssh shell"
    end
  }
  channel.on_data { |ch,data| 
    @stdout << data
    @buf << data
  }
  channel.on_extended_data { |ch,type,data| 
    @stderr << data
    @buf << data if type == 1
  }
  channel.on_request("exit-status") do |ch,data|
    @exit_code = data.read_long
  end
  channel.on_close { 
    @eof = true
  }
end
@ssh.loop

The problem is that when I run this, the @exit_code variable never changes from nil.

The reason I am doing this is because I need three major pieces of functionality: 1. Stateful (interactive) communication (so that if I cd into a directory the next command will occur in that directory) 2. The ability to read the exit status of any command I execute 3. The ability to respond to prompts

I selected Net::SSH::Telnet to adjust because it already offered 1 & 3. I figured I could fix it to support number 2.
If anyone can see how to fix this I would greatly appreciate it. The source for the rest of Net::SSH::Telnet is here:

https://github.com/jasonkarns/net-ssh-telnet/

and I have a forked version of the repo here to which I would gladly accept pull requests.

https://github.com/0x783czar/net-ssh-remotescript

Also if anyone has a suggestion of any other ruby libraries that would offer those three functionalities I would greatly appreciate any suggestions.

Answer 1

You may want to take a look at the source for the Ruby "ssh" gem and "remote_task" gem.

• http://rubygems.org/gems/ssh

The relevant source code is here:

• https://github.com/seattlerb/ssh/blob/master/lib/ssh.rb

It has code for handling the "cd" command, i/o channels, and the exit status.