Question

I have the following code that attempts to connect to various hosts and move data. The problem is if one connection attempt fails then the code dies. How can I get it to move to the next host in the array.

h=%w"host1 host2 host3 host4"

h.each do |hostname|

  tn = Net::Telnet::new("Host" => "#{hostname}",
                               "Timeout" => false,
                               "Prompt" => /[$%#>] \z/n)

  tn.cmd('String' =>'user' , 'Match'=>/Password:/) { |c| puts c }
  tn.cmd('String' =>'password', 'Match'=>/#/) { |c| puts c }


      tn.cmd('String' =>"show run | redirect tftp://192.1.1.1/#{hostname}-#{tdate}.cfg", 'Match'=>/#/) { |c| puts c }
      sleep(3)


end

Answer 1

You can continue beyond the first failed connection attempt by handling the exception raised by Net::Telnet::initialize. You’ll find you aren’t getting the error you think you’re getting:

begin
  tn = Net::Telnet::new("Host" => "#{hostname}",
                        "Timeout" => false,
                        "Prompt" => /[$%#>] \z/n)
rescue => e
  puts "Unable to connect to #{hostname}: #{e.message}"
  next
end

Produces

Unable to connect to host1: getaddrinfo: nodename nor servname provided, or not known

That is, you’re not actually providing a host name. The argument isn’t called "Host", it’s called "host", and case matters. Ruby options are also typically passed as symbols, not strings. Try this:

  tn = Net::Telnet::new(:host    => "#{hostname}",
                        :timeout => false,
                        :prompt  => /[$%#>] \z/n)

Now you’ll get the error you were expecting:

Unable to connect to host1: Connection refused – connect(2)