golang 输出重定向:fmt Log,子进程Log,第三方库logrus的详解

//代码摘自：golang封装包 -> /lib/golang/src/os
var (
 Stdin = NewFile(uintptr(syscall.Stdin), "/dev/stdin")
 Stdout = NewFile(uintptr(syscall.Stdout), "/dev/stdout")
 Stderr = NewFile(uintptr(syscall.Stderr), "/dev/stderr")
)

 f, _ := os.OpenFile("/home/fmt.log", os.O_WRONLY|os.O_CREATE|os.O_SYNC|os.O_APPEND,0755)
 os.Stdout = f
 os.Stderr = f

 func New() *Logger {
 return &Logger{
 Out: os.Stderr,
 Formatter: new(TextFormatter),
 Hooks: make(LevelHooks),
 Level: InfoLevel,
 }
}

import (
 "github.com/Sirupsen/logrus"
)
 f, _ := os.OpenFile("/home/fmt.log", os.O_WRONLY|os.O_CREATE|os.O_SYNC|os.O_APPEND,0755)
 logrus.SetOutput(f)

 cmd := exec.Command(binary_name, args...)
 f, _ := os.OpenFile("/home/exec.log", os.O_WRONLY|os.O_CREATE|os.O_SYNC,0755)
 cmd.Stdout = f
 cmd.Stderr = f

package main 
import (
 log "github.com/sirupsen/logrus"
) 
func main() {
 log.WithFields(log.Fields{
  "animal": "dog",
 }).Info("一条舔狗出现了。")
}

package main 
import (
 "os"
 "github.com/sirupsen/logrus"
) 
// 创建一个新的logger实例。可以创建任意多个。
var log = logrus.New() 
func main() {
 // 设置日志输出为os.Stdout
 log.Out = os.Stdout
 
 // 可以设置像文件等任意`io.Writer`类型作为日志输出
 // file, err := os.OpenFile("logrus.log", os.O_CREATE|os.O_WRONLY|os.O_APPEND, 0666)
 // if err == nil {
 // log.Out = file
 // } else {
 // log.Info("Failed to log to file, using default stderr")
 // }
 
 log.WithFields(logrus.Fields{
  "animal": "dog",
  "size":  10,
 }).Info("一群舔狗出现了。")
}

log.Trace("Something very low level.")
log.Debug("Useful debugging information.")
log.Info("Something noteworthy happened!")
log.Warn("You should probably take a look at this.")
log.Error("Something failed but I'm not quitting.")
// 记完日志后会调用os.Exit(1)
log.Fatal("Bye.")
// 记完日志后会调用 panic()
log.Panic("I'm bailing.")

log.WithFields(log.Fields{
 "event": event,
 "topic": topic,
 "key": key,
}).Fatal("Failed to send event")

requestLogger := log.WithFields(log.Fields{"request_id": request_id, "user_ip": user_ip})
requestLogger.Info("something happened on that request") # will log request_id and user_ip
requestLogger.Warn("something not great happened")

import (
 log "github.com/sirupsen/logrus"
 "gopkg.in/gemnasium/logrus-airbrake-hook.v2" // the package is named "airbrake"
 logrus_syslog "github.com/sirupsen/logrus/hooks/syslog"
 "log/syslog"
) 
func init() {
 
 // Use the Airbrake hook to report errors that have Error severity or above to
 // an exception tracker. You can create custom hooks, see the Hooks section.
 log.AddHook(airbrake.NewHook(123, "xyz", "production"))
 
 hook, err := logrus_syslog.NewSyslogHook("udp", "localhost:514", syslog.LOG_INFO, "")
 if err != nil {
  log.Error("Unable to connect to local syslog daemon")
 } else {
  log.AddHook(hook)
 }
}
　　

// a gin with logrus demo 
var log = logrus.New() 
func init() {
  // Log as JSON instead of the default ASCII formatter.
  log.Formatter = &logrus.JSONFormatter{}
  // Output to stdout instead of the default stderr
  // Can be any io.Writer, see below for File example
  f, _ := os.Create("./gin.log")
  log.Out = f
  gin.SetMode(gin.ReleaseMode) // 设置gin框架模式 线上模式 不会在终端打印多余的日志信息
  gin.DefaultWriter = log.Out
  // Only log the warning severity or above.
  log.Level = logrus.InfoLevel
} 
func main() {
  // 创建一个默认的路由引擎
  r := gin.Default()
  // GET：请求方式；/hello：请求的路径
  // 当客户端以GET方法请求/hello路径时，会执行后面的匿名函数
  r.GET("/hello", func(c *gin.Context) {
    log.WithFields(logrus.Fields{
      "animal": "walrus",
      "size":  10,
    }).Warn("A group of walrus emerges from the ocean")
    // c.JSON：返回JSON格式的数据
    c.JSON(200, gin.H{
      "message": "Hello world!",
    })
  })
  // 启动HTTP服务，默认在0.0.0.0:8080启动服务
  r.Run()
}