nums

#!/usr/bin/env ruby

require 'optparse'
require 'time'

DEFAULT_LIMIT = 1 << 32
DEFAULT_SLEEP = 1

def nums(limit, options={})
  sleep_time = options.fetch(:sleep, DEFAULT_SLEEP)

  err_stream = STDERR
  out_stream = STDOUT

  limit.times do |i|
    err_stream.puts("#{i} #{Time.now.strftime('@ %F %T %z')}")
    err_stream.flush

    out_stream.puts i
    out_stream.flush

    sleep sleep_time
  end
end

def main
  options={}
  optparse = OptionParser.new do |opts|
    opts.banner = <<-EOM
usage: #{File.basename($0)} [OPTIONS] [LIMIT]

Print integers up to LIMIT at regular intervals.

By default, sleep for #{DEFAULT_SLEEP} seconds between loop iterations, and
print integers up to 2**#{Math.log2(DEFAULT_LIMIT)}.

Options:
    EOM

    opts.on('-h', '--help', 'Display this message') do
      puts opts
      exit
    end

    opts.on('-s', '--sleep SEC', 'Sleep for SEC seconds between loops') do |v|
      options[:sleep] = Float(v)
    end

    opts.on('-q', '--quiet', 'Be less verbose with output') do
      options[:quiet] = true
    end
  end

  optparse.parse!

  limit = Integer(ARGV.fetch(0, DEFAULT_LIMIT))

  begin
    nums(limit, options)
  rescue Interrupt
  rescue Errno::EPIPE
    exit 141
  end
end

if $0 == __FILE__
  main
end