From: Jos Backus <jos@...>
Date: 2005-03-15T10:48:36+09:00
Subject: OptionParser question

OptionParser is still a mystery to me. In the example below, how do I
distinguish between a -c flag without an argument (which is a fatal syntax
error) and no -c flag at all? In both cases client equals nil. There doesn't
seem to be a way to intercept the `missing argument' message, or if there is,
I can't seem to find it in the documentation :-/

    require 'optparse'

    client = nil
    ARGV.options do |opt|
      opt.on("-c CLIENT", String) do |s|
	puts "client: #{s}"
	client = s
      end
      opt.parse!
    end

    puts "client is #{client}" if client

    puts "done"

Running the example yields:

    lizzy:~% ruby op -c foo
    client: foo
    client is foo
    done
    lizzy:~% ruby op -c    
    op: missing argument: -c
    done
    lizzy:~% ruby op   
    done
    lizzy:~% 

-- 
Jos Backus
jos at catnook.com