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comp.lang.ruby

parsing List results

Fernando Ramos

1/19/2009 5:00:00 PM

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.
--
Posted via http://www.ruby-....
3 Answers

Rob Biedenharn

1/19/2009 5:44:00 PM

0

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://agileconsult...
Rob@AgileConsultingLLC.com

Fernando Ramos

1/19/2009 5:55:00 PM

0

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://agileconsult...
> 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.
--
Posted via http://www.ruby-....

Phlip

1/19/2009 6:57:00 PM

0

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!