module Closure::Popen

def self.popen(cmd)
  pid = nil
  if WINDOWS
    error, pid = nil, nil
    Open4.popen4(cmd) do |stdin, stdout, stderr, win_pid|
      yield(stdin, stdout, stderr) if block_given?
      stdout.read unless stdout.closed? or stdout.eof?
      unless stderr.closed?
        stderr.rewind
        error = stderr.read
      end
      pid = win_pid
    end
  else
    # pipe[0] for read, pipe[1] for write
    pw, pr, pe = IO.pipe, IO.pipe, IO.pipe
    pid = fork {
      pw[1].close
      STDIN.reopen(pw[0])
      pw[0].close
      pr[0].close
      STDOUT.reopen(pr[1])
      pr[1].close
      pe[0].close
      STDERR.reopen(pe[1])
      pe[1].close
      exec(cmd)
    }
    pw[0].close
    pr[1].close
    pe[1].close
    pi = [pw[1], pr[0], pe[0]]
    pw[1].sync = true
    begin
      yield(*pi) if block_given?
    ensure
      pi.each{|p| p.close unless p.closed?}
    end
    Process.waitpid pid
  end
  pid
end