OptionParser.rb

#!/usr/bin/env ruby

require 'optparse'
require 'pp'

# This hash will hold all of the options
# parsed from the command-line by
# OptionParser.
options = {}

optparse = OptionParser.new do|opts|
  
  opts.banner = "Usage: executable [OPTIONS]"
  
  # 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
  
  options[:simple] = false
  opts.on( '-s', '--simple', "Simple argument" ) do
    options[:simple] = true
  end

  options[:mand] = ""
  opts.on( '-m', '--mandatory FILE', "Mandatory argument" ) do|f|
    options[:mand] = f
  end
  
  options[:opt] = false
  opts.on( '-o', '--optional [OPT]', "Optional argument" ) do|f|
    options[:opt] = f || "nothing"
  end  
  
  options[:float] = 0.0
  opts.on( '-f', '--float NUM', Float, "Convert to float" ) do|f|
    options[:float] = f
  end
  
  options[:list] = []
  opts.on( '-l', '--list a,b,c', Array, "List of parameters" ) do |l|
    options[:list] = l
  end
  
  options[:set] = :yes
  opts.on( '-a', '--set OPT', [:yes, :no, :maybe], "Parameters from a set" ) do|s|
    options[:set] = s
  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!

pp "Options:", options
pp "ARGV:", ARGV