Create a file descriptor in ruby - ruby

Question

I am writing a script will perform various tasks with DSV or positional files. These tasks varies and are like creating an DB table for the file, or creating a shell script for parsing it.
As I have idealized my script would receive a "descriptor" as input to perform its tasks. It then would parse this descriptor and perform its tasks accordingly.
I came up with some ideas on how to specify the descriptor file, but didn't really manage to get something robust - probably due my inexperience in ruby.
It seems though, the best way to parse the descriptor would be using ruby language itself and then somehow catch parsing exceptions to turn into something more relevant to the context.
Example:
The file I will be reading looks like (myfile.dsv):
jhon,12343535,27/04/1984
dave,53245265,30/03/1977
...
Descriptor file myfile.des contains:
FILE_TYPE = "DSV"
DSV_SEPARATOR = ","
FIELDS = [
name => [:pos => 0, :type => "string"],
phone => [:pos => 1, :type => "number"],
birthdate => [:pos => 2, :type => "date", :mask = "dd/mm/yyyy"]
]
And the usage should be:
ruby script.rb myfile.des --task GenerateTable
So the program script.rb should load and parse the descriptor myfile.des and perform whatever tasks accordingly.
Any ideas on how to perform this?

Answer 1

Use YAML
Instead of rolling your own, use YAML from the standard library.
Sample YAML File
Name your file something like descriptor.yml, and fill it with:
---
:file_type: DSV
:dsv_separator: ","
:fields:
:name:
:pos: 0
:type: string
:phone:
:pos: 1
:type: number
:birthdate:
:pos: 2
:type: date
:mask: dd/mm/yyyy
Loading YAML
You can read your configuration back in with:
require 'yaml'
settings = YAML.load_file 'descriptor.yml'
This will return a settings Hash like:
{:file_type=>"DSV",
:dsv_separator=>",",
:fields=>
{:name=>{:pos=>0, :type=>"string"},
:phone=>{:pos=>1, :type=>"number"},
:birthdate=>{:pos=>2, :type=>"date", :mask=>"dd/mm/yyyy"}}}
which you can then access as needed to configure your application.