From: Josh Cheek <josh.cheek@...>
Date: 2012-01-24T20:45:31+09:00
Subject: Re: Dynamically creating variables

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On Tue, Jan 24, 2012 at 5:13 AM, Tris Hoar <trishoar@bgfl.org> wrote:

> Hi all,
>
> I'm fairly new to Ruby, and programming in general (though I'm reasonably
> proficient at shell scripting) so sorry if this is a dumb question.
>
> I'm trying to write a script for an SNMP poller but I'm getting stuck
> trying to work out how to create my variables. The script will be
> processing a CSV of unknown length. It might be just 2 servers or it could
> be up to 20. I cant work out how I can find the list of servers from the
> CSV and then create variables for each one that I can keep track off
> through out the programs life to out put what I want.
> this is what I've created so far
> http://pastebin.com/bLPbnRv4
> I envision it parsing a CSV like this
>
> --
> host,port,community,cluster,**shortName,type,rpsTotal,**
> clientTotal,serverTotal
> 172.16.0.1,161,Public,Library,**mwg1,mwg7,0,0,0
> 172.16.0.1,161,Public,Library,**mwg2,mwg7,0,0,0
> --
> after each run, it will need to update the CSV with the results of the
> last poll as those are used to calculate the average throughput between
> each time the script is called.
>
> The whole process will be called as a cron job, and will be outputting an
> HTML file.
>
> Reading around has not really helped me as I've not found any examples of
> others doing this, though I cant imagine others are not.
>
> If any one can give me some pointers, that would be really helpful.
>
> Thanks,
>
> Tris
>
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>

So you can use CSV.parse and give it a string or a stream, or you can use
CSV.foreach and give it a path to a file. Docs are here
http://rubydoc.info/stdlib/csv/frames

In Ruby, you can iterate over collections (e.g. 2..20 servers). A CSV file
is a collection of rows. If we tell it the CSV has headers, it will present
each row with a hash interface so that we can access the elements by name.

csv = <<CSV
host,port,community,cluster,shortName,type,rpsTotal,clientTotal,serverTotal
172.16.0.1,161,Public,Library,mwg1,mwg7,0,0,0
172.16.0.1,161,Public,Library,mwg2,mwg7,0,0,0
CSV

require 'csv'

# this block of code will be invoked once for each row in the CSV
CSV.parse csv, :headers => true do |row|
  host = row['host']
  port = row['port']
  # etc
  proxy = Proxy.new host, port # etc
  proxy.write_stats # or something
end

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