[blockchain-026] go的log 极简例子

1.stdout输出log信息

package main

import (
	"bytes"
	"fmt"
	"log"
)

func main() {
	fmt.Println("demo of log")
	var (
		buf    bytes.Buffer
		logger = log.New(&buf, "Info:",
			//log参数配置组合，列出参考。有些参数只能一个生效，比如log.Llongfile|log.Lshortfile。
			log.Ldate|log.Ltime|log.Lmicroseconds|log.Llongfile|log.Lshortfile|log.LUTC|log.LstdFlags)
		infof = func(info string) {
			logger.Output(2, info)
		}
	)

	infof("hello world")
	fmt.Println(&buf)
	fmt.Println("demo of log over")
}

2.在log文件输出log信息，注意：需要先创建log目录，否则会报错

package main

import (
	"fmt"
	"io"
	"log"
	"os"
)

func main() {
	file, err := os.OpenFile("log/g1.log", os.O_CREATE|os.O_WRONLY|os.O_APPEND, 0666)
	if err != nil {
		log.Fatalln("Failed to open log file", os.Stdout, ":", err)
	}

	multi := io.MultiWriter(file, os.Stdout)

	myLogger := log.New(multi, "Info:", log.Ldate|log.Ltime|log.Llongfile)
	infof := func(info string) {
		myLogger.Output(2, info)
	}

	infof("hi")

	fmt.Println("log file")
}