code: func (p *Process) LogTo(filename string) error {
  	if p.cmd != nil {
  		panic("logfd cannot be set with an existing cmd")
  	}
  
  	if p.logfd != nil {
  		p.logfd.Close()
  	}
  
  	fd, err := os.Create(filename)
  	if err != nil {
  		return err
  	}
  	p.logfd = fd
  	return nil
  }
docs: // LogTo creates the specified log file and ensures that stdout and stderr
  // from the Start()ed process is redirected there. Must be called before
  // Start().