code: func (t *FileTarget) Process(e *Entry) {
  	if e == nil {
  		t.fd.Close()
  		t.close <- true
  		return
  	}
  	if t.fd != nil && t.Allow(e) {
  		if t.Rotate {
  			t.rotate(int64(len(e.String()) + 1))
  		}
  		n, err := t.fd.Write([]byte(e.String() + "\n"))
  		t.currentBytes += int64(n)
  		if err != nil {
  			fmt.Fprintf(t.errWriter, "FileTarge write error: %v\n", err)
  		}
  	}
  }
docs: // Process saves an allowed log message into the log file.