ruby DSL example for command execution

gistfile1.rb

#! /usr/pkg/bin/ruby
# Copyright (c) 2015 Yuji Yamano
# The BSD 2-Clause License.

require 'open3'
require 'date'
require 'stringio'

module DSL
  class Command
    def initialize(cmds)
      @cmds = cmds
    end
    def append_to(file)
      execute(file, append: true)
    end
    def redirect_to(file)
      execute(file, append: false)
    end

    def execute(outfile, append: false)
      File.open(outfile, append ? "a" : "w") do |out|
        @cmds.each do |cmd|
          if cmd.is_a? String
            execute_cmd(cmd, out) 
          elsif cmd.is_a? Proc
            execute_proc(cmd, out)
          end
        end
      end
    end

    def execute_cmd(cmd, out)
      out.puts "#{DateTime.now.to_s}: Executing '#{cmd}'..."
      begin
        stdout, stderr, status = Open3.capture3(cmd)
        out.write stdout
        out.write stderr
        result = (status == 0) ? 
          "#{DateTime.now.to_s}: '#{cmd}' was executed successfully." : 
          "#{DateTime.now.to_s}: Failed to execute '#{cmd}'. status=#{status}."
        out.puts result
      rescue => e
        out.puts "#{DateTime.now.to_s}: Failed to execute '#{cmd}': #{e.message}"
      end
    end

    def execute_proc(proc, out)
      stdout_orig = STDOUT.clone
      stderr_orig = STDERR.clone
      begin
        out.puts "#{DateTime.now.to_s}: Executing #{proc.inspect}'..."
        STDOUT.reopen(out)
        STDERR.reopen(out)
        proc.call
        out.puts "#{DateTime.now.to_s}: #{proc.inspect} was executed successfully."
      rescue => e
        out.puts "#{DateTime.now.to_s}: Failed to execute #{proc.inspect}: #{e.inspect}"
        out.puts e.backtrace
      ensure
        STDOUT.reopen(stdout_orig)
        STDERR.reopen(stderr_orig)
      end
    end

  end

  def exec(*cmds)
    Command.new(cmds)
  end
end

include DSL

p1 = Proc.new do
  puts "STDOUT!"
  STDERR.puts "STDERR!"
  puts "Found /tmp" if File.exist?("/tmp")
  puts "Not found /path/to/file" if File.exist?("/path/to/file")
end
p2 = Proc.new do
  puts "Hi again!"
  raise "Raise an exception!"
end

exec('echo hey hey').redirect_to("/tmp/foo")
exec('ls', 'who').append_to("/tmp/foo")
exec('i_dont_expect_this_command_exists').append_to("/tmp/foo")
exec('cc -v').append_to("/tmp/foo")
exec('who', p1, p2, 'who').append_to("/tmp/foo")
exec('pwd; cd /; pwd; ls -l').append_to("/tmp/foo")