The best example of Optparse available on Internet Taken from official ruby docs.

optparse_example.rb

require 'optparse'
require 'optparse/time'
require 'ostruct'
require 'pp'

class OptparseExample

  CODES = %w[iso-2022-jp shift_jis euc-jp utf8 binary]
  CODE_ALIASES = { "jis" => "iso-2022-jp", "sjis" => "shift_jis" }

  #
  # Return a structure describing the options.
  #
  def self.parse(args)
    # The options specified on the command line will be collected in *options*.
    # We set default values here.
    options = OpenStruct.new
    options.library = []
    options.inplace = false
    options.encoding = "utf8"
    options.transfer_type = :auto
    options.verbose = false

    opt_parser = OptionParser.new do |opts|
      opts.banner = "Usage: example.rb [options]"

      opts.separator ""
      opts.separator "Specific options:"

      # Mandatory argument.
      opts.on("-r", "--require LIBRARY",
              "Require the LIBRARY before executing your script") do |lib|
        options.library << lib
      end

      # Optional argument; multi-line description.
      opts.on("-i", "--inplace [EXTENSION]",
              "Edit ARGV files in place",
              "  (make backup if EXTENSION supplied)") do |ext|
        options.inplace = true
        options.extension = ext || ''
        options.extension.sub!(/\A\.?(?=.)/, ".")  # Ensure extension begins with dot.
      end

      # Cast 'delay' argument to a Float.
      opts.on("--delay N", Float, "Delay N seconds before executing") do |n|
        options.delay = n
      end

      # Cast 'time' argument to a Time object.
      opts.on("-t", "--time [TIME]", Time, "Begin execution at given time") do |time|
        options.time = time
      end

      # Cast to octal integer.
      opts.on("-F", "--irs [OCTAL]", OptionParser::OctalInteger,
              "Specify record separator (default \\0)") do |rs|
        options.record_separator = rs
      end

      # List of arguments.
      opts.on("--list x,y,z", Array, "Example 'list' of arguments") do |list|
        options.list = list
      end

      # Keyword completion.  We are specifying a specific set of arguments (CODES
      # and CODE_ALIASES - notice the latter is a Hash), and the user may provide
      # the shortest unambiguous text.
      code_list = (CODE_ALIASES.keys + CODES).join(',')
      opts.on("--code CODE", CODES, CODE_ALIASES, "Select encoding",
              "  (#{code_list})") do |encoding|
        options.encoding = encoding
      end

      # Optional argument with keyword completion.
      opts.on("--type [TYPE]", [:text, :binary, :auto],
              "Select transfer type (text, binary, auto)") do |t|
        options.transfer_type = t
      end

      # Boolean switch.
      opts.on("-v", "--[no-]verbose", "Run verbosely") do |v|
        options.verbose = v
      end

      opts.separator ""
      opts.separator "Common options:"

      # No argument, shows at tail.  This will print an options summary.
      # Try it and see!
      opts.on_tail("-h", "--help", "Show this message") do
        puts opts
        exit
      end

      # Another typical switch to print the version.
      opts.on_tail("--version", "Show version") do
        puts OptionParser::Version.join('.')
        exit
      end
    end

    opt_parser.parse!(args)
    options
  end  # parse()

end  # class OptparseExample

options = OptparseExample.parse(ARGV)
pp options
pp ARGV