From: Rob Biedenharn <Rob@...>
Date: 2009-01-20T02:43:55+09:00
Subject: Re: parsing List results

On Jan 19, 2009, at 12:00 PM, Fernando Ramos wrote:

> Hi Folks,
>
> I need to parse a result that comes in this format :
>
> =========================
> ec2.describe_instances #=>
>   [{:aws_image_id       => "ami-e444444d",
>     :aws_reason         => "",
>     :aws_state_code     => "16",
>     :aws_owner          => "000000000888",
>     :aws_instance_id    => "i-123f1234",
>     :aws_reservation_id => "r-aabbccdd",
>     :aws_state          => "running",
>     :dns_name           =>
> "domU-12-34-67-89-01-C9.usma2.compute.amazonaws.com",
>     :ssh_key_name       => "staging",
>     :aws_groups         => ["default"],
>     :private_dns_name   =>
> "domU-12-34-67-89-01-C9.usma2.compute.amazonaws.com",
>     :aws_instance_type  => "m1.small",
>     :aws_launch_time    => "2008-1-1T00:00:00.000Z"},
>     :aws_availability_zone => "us-east-1b",
>     :aws_kernel_id      => "aki-ba3adfd3",
>     :aws_ramdisk_id     => "ari-badbad00",
>      ..., {...}]
> =========================
>
> When I invoke the method,
>
> puts @ec2.describe_instances
>
> the results comes like this :
> =========================
> aws_image_idami- 
> e444444daws_reasonaws_state_codeaws_owner000000000888aws_instance_id
> i-123f1234aws_reservation_idr-aabbccddaws_staterunningdns_name
> domU-12-34-67-89-01- 
> C9.usma2.compute.amazonaws.comssh_key_namestagingaws_groups
> ...
> =========================
> Question :
>
> Is there a way of accessing a specific key, for example : aws_status ?
> If so, how do I do that ?
>
> Thank you so much.
>
> Regards.
>

You can:
  require 'pp'
  pp @ec2.describe_instances

or just use #inspect: (which is what irb does with the last expression  
anyway)
  p @ec2.describe_instances
  puts @ec2.describe_instances.inspect

As for getting the specific key (did you mean 'aws_state'?), perhaps  
something like:
   @ec2.describe_instances.each do |instance_hash|
     puts "%20s:  
%s"%instance_hash.values_at(:aws_instance_id, :aws_state)
   end

           i-123f1234: running

You can look at: String#%, Kernel.sprintf, Hash#values_at, and Hash#[]  
(oh yeah, and Enumerable#each) for the details.

-Rob

Rob Biedenharn		http://agileconsultingllc.com
Rob@AgileConsultingLLC.com