From: LDC - Jairo Eduardo Lopez <jairo@...>
Date: 2007-05-25T07:46:46+09:00
Subject: Re: Ruby, OptionParser and multiple flags

On Fri, 25 May 2007, ara.t.howard wrote:

>
> On May 24, 2007, at 10:13 AM, LDC - Jairo Eduardo Lopez wrote:
>
>> Hello all,
>> 
>> I'm currently writing a small script needed for my lab in which I need to 
>> parse a few command line arguments in a UNIX like way.
>> 
>> My code goes something like this:
>> 
>> #####
>> #!/usr/bin/ruby -w
>> 
>> require 'optparse'
>> require 'ostruct'
>> 
>> opciones = OpenStruct.new
>> opts = OptionParser.new do |opts|
>>    opts.on("-u USER", "--uid USER", "UID del usuario.") do |usr|
>>        opciones.user = usr
>>    end
>>
>>    opts.on("-h HOST", "--host HOST", String, "Especifica el servidor. Puede 
>> ser IP o DNS.") do |h|
>> 
>
>> opciones.host = h
>>    end
>>
>>    opts.on("-p PORT", "--port PORT", Integer, "Especifica el puerto del 
>> servidor. Debe ser entero.") do |p|
>>        opciones.port = p
>>    end
>> end
>> 
>> begin
>>    opts.parse!(ARGV)
>> rescue Exception => e
>>    puts e, opts
>>    exit!
>> end
>> 
>> #####
>> 
>> When I run the script I run into the problem that if I use various flags, 
>> and forget to put in the required arguments, some flags are taken as 
>> arguments. I've read that if I use the coding I've used all three flags, 
>> the argument should be obligatory.
>> 
>> To better explain, I'll give some examples:
>> 
>> -----
>> ./script.rb -h
>> missing argument: -h
>> -----
>> Works fine.
>> 
>> -----
>> ./script.rb -p
>> missing argument: -p
>> -----
>> Works fine.
>> 
>> -----
>> ./script.rb -h -p -----
>> The script accepts -p as the argument for -h, which shouldn't happen as -p 
>> is actually a flag.
>> 
>> I'm not sure what the problem is so I need help.
>
> you've told the option parser that -h accepts an argument and you've given it 
> one.  there is no restriction that arguments must not start with a '-' so, in 
> this case, your code is doing it exactly what you told it to do ;-)
>
>
> -a
> --
> we can deny everything, except that we have the possibility of being better. 
> simply reflect on that.
> h.h. the 14th dalai lama
>
>
>
>

Fair enough. I thought that OptionParser looked out for that sort of 
thing. Is there anyone who can point me in a direction so that I can try 
and avoid that sort of confusion between arguments?

-- 
Jairo E. Lopez
Laboratorio Docente de Computacion
Universidad Simon Bolivar