module SpawnProcess
  class NonSuccessStatus < StandardError
    attr_accessor :status
    def initialize(str, status)
      @status = status
      super(str)
    end
  end

  def self.do(*args, &block)
    args = args.map(&:to_s)
    in_r, in_w = IO.pipe()
    out_r, out_w = IO.pipe()
    err_r, err_w = IO.pipe()
    pid = spawn(*args, :in => in_r, :out => out_w, :err => err_w)
    in_r.close
    out_w.close
    err_w.close
    if block
      in_w.write(block.call())
    end
    in_w.close
    out_reader = Thread.new { out_r.read }
    err_reader = Thread.new { err_r.read }
    Process.waitpid(pid)
    out_str = out_reader.value
    err_str = err_reader.value
    out_r.close
    err_r.close
    if !$?.success?
      raise NonSuccessStatus.new(err_str, $?)
    end
    out_str
  end
end