run_and_notifier.rb

#!/usr/bin/env ruby
require 'open3'
require 'optparse'

module RunAndNotify
  def self.parse!(argv)
    notifiers = []

    opt     = OptionParser.new
    opt.on('--notifier NOTIFIER') {|v|
      notifiers << RunAndNotify.const_get("#{v}Notifier")
    }
    opt.parse!
    opt.permute! argv

    command = ARGV.join(' ')
    self.new(command, notifiers: notifiers.map {|c| c.new})
  end

  def self.new(*argv)
    Runner.new(*argv)
  end

  class Result
    attr_reader :command, :out, :err, :status

    def initialize(command, out, err, status)
      @command = command
      @out     = out
      @err     = err
      @status  = status
    end

    def render
      <<-EOM.gsub(/^ {8}/, '')
        ****** COMMAND ******
        #{self.command}

        ****** STATUS ******
        #{self.status.inspect}

        ****** STDOUT ******
        #{self.out}

        ****** STDERR ******
        #{self.err}
      EOM
    end
  end

  class Runner
    attr_accessor :notifiers

    def initialize(command, options={})
      @command   = command
      @notifiers = options[:notifiers] || []
    end

    def run_and_notify
      result = self.run

      self.notifiers.each do |notifier|
        notifier.notify(result)
      end

      result.status
    end

    def run
      _ = Open3.capture3(@command)

      Result.new(@command, *_)
    end
  end

  module Notifier
    class Base
      def notify(_)
        raise NotImplementedError
      end
    end
  end

  class StdoutNotifier
    def notify(result)
      puts result.render
    end
  end
end

if __FILE__ == $0
  runner  = RunAndNotify.parse!(ARGV)
  status = runner.run_and_notify

  exit status.exitstatus
end

__END__

=head1 NAME

run_and_notify - run a cron job and notify result to what you want.

=head1 USAGE

0 9 * * * /path/to/run_and_notify --notifier Stdout -- "echo 'Good morning!'"