From: Stefano Crocco <stefano.crocco@...>
Date: 2007-11-16T17:23:04+09:00
Subject: Re: Can someone show me how to use ARGV with my class?

Alle venerdì 16 novembre 2007, Feng Tien ha scritto:
> I'm trying to write an command line program.
>
> For instance
>
>
> if I have a class like this with 1 method
>
>
> class Coolest Program
>   coolest_method (a,b)
>     puts a + b
>   end
> end
> ======
>
> How do I program it so it runs in command line?
>
> so:
> ====
> ruby coolest.rb "cool" "est"
> ====
> it'll output:
>
> coolest
>
> ===
>
> aka insert the 2 arguments into the Coolest Program object? Can't seem
> to figure this out, been searching the last hour. I get how to use the
> OptionParser library to take options, but not arguments.

If you don't need to pass options but only arguments, you don't need 
OptionParser at all. Command line arguments and options are stored in the 
ARGV array. For example, if you do:

ruby my_program.rb -a --b-with-long-name=3 arg1 arg2

ARGV will be:

["-a", "--b-with-long-name=3", "arg1", "arg2"]

In your example case, you can do (note that Coolest Program is not a valid 
name for a class):

class CoolestProgram
  coolest_method (a,b)
    puts a + b
  end
end

CoolestProgram.coolest_method(ARGV[0], ARGV[1])

If you need to use OptionParser because you also need options, there are two 
situations, depending on whether you use OptionParser#parse! or 
OptionParser#parse. Both methods return the command line arguments, but the 
first also changes ARGV	removing all the options, so that it will contain 
only the arguments.
For example, take the following script:

#!/usr/bin/env ruby

require 'optparse'

opts={}

o = OptionParser.new do |o|
  o.on("-v", "--verbose", "turn on the verbose flag"){opts[:verbose]=true}
end

args  = o.parse(ARGV)

puts "opts= #{opts.inspect}"

puts "ARGV= #{ARGV.inspect}"

puts "args= #{args.inspect}"

called with the command:

ruby program.rb -v 1 2 3

outputs:

opts= {:verbose=>true}
ARGV= ["-v", "1", "2", "3"]
args= ["1", "2", "3"]

If I replace the line o.parse(ARGV) with o.parse!(ARGV), I get

opts= {:verbose=>true}
ARGV= ["1", "2", "3"]
args= ["1", "2", "3"]

I hope this helps

Stefano