glog_file.go
func logName(logger, tag string, t time.Time) (name, link string) {
	name = fmt.Sprintf("%s.%s.%s.log.%s.%s.%04d%02d%02d-%02d%02d%02d.%d",
		program,
		host,
		userName,
		logger,
		tag,
		t.Year(),
		t.Month(),
		t.Day(),
		t.Hour(),
		t.Minute(),
		t.Second(),
		pid)
	return name, program + "." + tag
}
func logName(logger, tag string, t time.Time) (name, link string) {
	name = fmt.Sprintf("%s.%s.%s.log.%s.%s.%04d%02d%02d-%02d%02d%02d.%d",
		program,
		host,
		userName,
		logger,
		tag,
		t.Year(),
		t.Month(),
		t.Day(),
		t.Hour(),
		t.Minute(),
		t.Second(),
		pid)
	return name, program + "." + tag
}
// logName returns a new log file name containing tag, with start time t, and
// the name for the symlink for tag.