Parsing List results

ruby-talk
1

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.
--
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2

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

···

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.

3

Fernando Ramos wrote:

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

puts outputs strings, so it calls .to_s on its argument.

.to_s on a hash calls .to_s on all its keys and values, and mashes them together.

Use p @ec2.describe_instances, or require 'pp' and use pp.

Is there a way of accessing a specific key, for example : aws_status ?
If so, how do I do that ?

p @ec2.describe_instances[2][:aws_status]

Now play around with (and read the docs on) Array and Hash!

4

Rob Biedenharn wrote:

···

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

    :aws_instance_id => "i-123f1234",
    :aws_availability_zone => "us-east-1b",

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

Hi Rob,

You've got it !!! Thank you so much. It is working the way I want now !
Appreciate it !

Regards,

Fernando.
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