go的基础包 flag log time

• 命令行参数-flag

  package main
  
  import (
  	"flag"
  	"fmt"
  	"os"
  )
  
  
  func main() {
  	var (
  		host string
  		port int
  		h bool
  		help bool
  	)
  	//flag param
  	flag.StringVar(&host, "H", "127.0.0.1", "hostIPAddress")
  	flag.IntVar(&port, "P", 22, "port")
  	flag.BoolVar(&h,"h", false, "帮助信息")
  	flag.BoolVar(&help, "help", false, "帮助信息")
  
  	//usage信息
  	flag.Usage = func() {
  		fmt.Println("usage: testflag [-H 127.0.0.1] [-P 22]")
  		flag.PrintDefaults()
  	}
  
  
  	//解析
  	flag.Parse()
  
  	if h || help {
  		flag.Usage()
  		//return
  		//建议在main中使用
  		os.Exit(0)
  	}
  
  	//NFlag returns the number of command-line flags that have been set.
  	fmt.Println(flag.NFlag())
  	fmt.Printf("%#v\n",flag.Args())  //slice
  
  	fmt.Println(host, port)
  
  
  }
  

• 日志-log

  package main
  
  import (
  	"log"
  	"os"
  )
  
  
  func main() {
  
  	//flag0s 设置一个格式
  	log.SetFlags(log.Flags() | log.Lshortfile)
  
  	//prefix
  	log.SetPrefix("main:")
  
  	log.Println("我是第一条println日志")
  
  	//log.Fatalln("我是日志")
  	//log.Panicln("我是panic日志")
  	log.Println("我是第2条println日志")
  
  	logger1 := log.New(os.Stdout, "logger1:", log.Flags() | log.Lshortfile)
  	logger2 := log.New(os.Stdout, "logger2:", log.Flags())
  
  	logger1.Println("我是logger1")
  	logger2.Println("我是logger2")
  }
  
  

• 时间格式化-time

  package main
  
  import (
  	"fmt"
  	"time"
  )
  
  func main() {
  
  	//1.时间
  	 now := time.Now()
  	//年
  	 fmt.Println(now.Year())
  	 fmt.Println(now.Month())
  	 fmt.Println(now.Day())
  	 fmt.Println(now.Hour())
  	 fmt.Println(now.Minute())
  	 fmt.Println(now.Second())
  	 //UNix时间戳
  	 fmt.Println(now.Unix())
  	 //纳秒时间戳
  	 fmt.Println(now.UnixNano())
  
  	 // 2006 4位数字的年
  	 // 01 2位数字的月
  	 // 02 2位数字的天
  	 // 03 12进制的小时
  	 // 15 24进制的小时
  	 // 04 2位数字的分钟
  	 // 05 2位数字的秒
  	 fmt.Println(now.Format("2006-01-02 03:04:05"))
  	 fmt.Println(now.Format("2006-01-02 15:04:05"))
  
  	//生成时间
  	year, month, day := 1990, time.February, 12
  	timeFom := time.Date(year, month, day, 0, 0,0, 0, time.UTC)
  	fmt.Println(timeFom.Format("2006-01-02 15:04:05"))
  
  	//UNixtime
  	startTime := time.Unix(0, 0)
  	fmt.Println(startTime.Format("2006-01-02 15:04:05"))
  
  	//字符串
  	cTime, err := time.Parse("2006-01-02 15:04:05", "2022-01-25 13:54:03")
  	fmt.Println(cTime.Format("2006-01-02"), err)
  
  	cTime, err = time.Parse("2006/01/02", "2022/01/24")
  	fmt.Println(cTime.Format("2006/01/02"), err)
  
  	//时间差, now -time
  	durat := time.Since(cTime)
  	fmt.Printf("%#v, %T\n", durat, durat)
  
  	// time - now
  	durat02 := time.Until(cTime)
  	fmt.Printf("%#v, %T\n", durat02, durat02)
  
  	//parse字符串的时间区间
  	durat03, err := time.ParseDuration("1h1m1s")
  	fmt.Println(durat, err)
  	//将相差时间区间转换成hours, min, seconds
  	fmt.Println(durat.Hours(), durat03.Minutes(), durat03.Seconds())
  
  	//当前时间距离过去xx时间多少小时
  	dayInterval, err := time.ParseDuration("24h")
  	//2022-01-25 14:27:00.2045069 +0800 CST m=+0.007000101 2022-01-26 14:27:00.2045069 +0800 CST m=+86400.007000101
  	fmt.Println(now, now.Add(dayInterval))
  
  	//判断一个时间在之前还是之后
  	yesterday := now.Add(dayInterval) //过去的时间
  	fmt.Println(yesterday.Before(now))
  	fmt.Println(yesterday.After(now))
  
  	fmt.Println(yesterday.Sub(now)) //时间差
  
  	fmt.Println(time.Now())
  	time.Sleep(time.Second * 3) //延迟3s
  
  	fmt.Println(time.Now())
  }