http://ruby.about.com/od/advancedruby/a/optionparser.htm

OptionParseは以下のコードを見るのが一番はやいかな。

• optparse.parse!するとARGVからパラメータを読み込んでoption hashに設定するコード
• ARGVはコード上で渡さなくてもOptionParseの内分でdefaultでARGVを利用するのでparse!メソッドにわざわざ渡す必要はない

sample source

#!/usr/bin/env ruby
# # A script that will pretend to resize a number of images

require 'optparse'
# This hash will hold all of the options # parsed from the command-line by
# OptionParser.
options = {}
optparse = OptionParser.new do |opts|
# Set a banner, displayed at the top
# # of the help screen.
  opts.banner = "Usage: optparse1.rb [options] file1 file2 ..."

  # Define the options, and what they do
  options[:verbose] = false
  opts.on( '-v', '--verbose', 'Output more information' ) do
    options[:verbose] = true
  end

  options[:quick] = false
  opts.on( '-q', '--quick', 'Perform the task quickly' ) do
    options[:quick] = true
  end

  options[:logfile] = nil
  opts.on( '-l', '--logfile FILE', 'Write log to FILE' ) do |file|
    options[:logfile] = file
  end

  # This displays the help screen, all programs are
  # assumed to have this option.
  opts.on( '-h', '--help', 'Display this screen' ) do
    puts opts
    exit
  end
end

# Parse the command-line. Remember there are two forms # of the parse method.
# The 'parse' method simply parses
# ARGV, while the 'parse!' method parses ARGV and removes
# any options found there, as well as any parameters for
# the options. What's left is the list of files to resize.

optparse.parse!
puts "Being verbose" if options[:verbose]
puts "Being quick" if options[:quick]
puts "Logging to file #{options[:logfile]}" if options[:logfile]
ARGV.each do|f|
  puts "Resizing image #{f}..."
  sleep 0.5
end