Convert file encoding

convert_encoding.rb

#!/usr/bin/env ruby

require 'optparse'
require 'pry'

def main

  options = {to_encoding: 'utf-8'}
  option_parser = OptionParser.new do |opts|
    executable_name = File.basename($PROGRAM_NAME)
    opts.banner = "Convert file from one encoding to another

Usage: #{executable_name} [options] input_filename output_filename"

    opts.on("-f from-encoding") do |from_encoding|
      options[:from_encoding] = from_encoding
    end

    opts.on("-t to-encoding") do |to_encoding|
      options[:to_encoding] = to_encoding
    end

  end

  option_parser.parse!

  input_filename = ARGV.shift
  output_filename = ARGV.shift
  output_file = File.open(output_filename, 'a')
  File.open(input_filename) do |file|
    file.each_line do |line|
      output_file << line.encode(options[:to_encoding],
                                 options[:from_encoding])
    end
  end

end

if __FILE__ == $0
  main
end