go语言使用官方的 log package 来记录日志
原文:https://www.goinggo.net/2013/11/using-log-package-in-go.html
----------------------------------------------------------------------------------------------------------------
Linux is unique to Windows in many ways, and writing programs in Linux is no exception. The use of standard out, standard err and null devices is not only a good idea but it’s the law. If your programs are going to be logging information, it is best to follow the destination conventions. This way your programs will work with all of the Mac/Linux tooling and hosted environments.
Go has a package in the standard library called log and a type called logger. Using the log package will give you everything you need to be a good citizen. You will be able to write to all the standard devices, custom files or any destination that support the io.Writer interface.
I have provided a really simple sample that will get you started with using logger:
import (
"io"
"io/ioutil"
"log"
"os"
)
var (
Trace *log.Logger
Info *log.Logger
Warning *log.Logger
Error *log.Logger
)
func Init(
traceHandle io.Writer,
infoHandle io.Writer,
warningHandle io.Writer,
errorHandle io.Writer) {
Trace = log.New(traceHandle,
"TRACE: ",
log.Ldate|log.Ltime|log.Lshortfile)
Info = log.New(infoHandle,
"INFO: ",
log.Ldate|log.Ltime|log.Lshortfile)
Warning = log.New(warningHandle,
"WARNING: ",
log.Ldate|log.Ltime|log.Lshortfile)
Error = log.New(errorHandle,
"ERROR: ",
log.Ldate|log.Ltime|log.Lshortfile)
}
func main() {
Init(ioutil.Discard, os.Stdout, os.Stdout, os.Stderr)
Trace.Println("I have something standard to say")
Info.Println("Special Information")
Warning.Println("There is something you need to know about")
Error.Println("Something has failed")
}
When you run this program you will get the follow output:
WARNING: 2013/11/05 18:11:01 main.go:45: There is something you need to know about
ERROR: 2013/11/05 18:11:01 main.go:46: Something has failed
You will notice that Trace logging is not being displayed. Let’s look at the code to find out why.
Look at the Trace logger pieces:
Trace = log.New(traceHandle,
"TRACE: ",
log.Ldate|log.Ltime|log.Lshortfile)
Init(ioutil.Discard, os.Stdout, os.Stdout, os.Stderr)
Trace.Println("I have something standard to say")
The code creates a package level variable called Trace which is a pointer to a log.Logger object. Then inside the Init function, a new log.Logger object is created. The parameters to the log.New function are as follows:
out: The out variable sets the destination to which log data will be written.
prefix: The prefix appears at the beginning of each generated log line.
flags: The flag argument defines the logging properties.
Flags:
const (
// Bits or’ed together to control what’s printed. There is no control over the
// order they appear (the order listed here) or the format they present (as
// described in the comments). A colon appears after these items:
// 2009/01/23 01:23:23.123123 /a/b/c/d.go:23: message
Ldate = 1 << iota // the date: 2009/01/23
Ltime // the time: 01:23:23
Lmicroseconds // microsecond resolution: 01:23:23.123123. assumes Ltime.
Llongfile // full file name and line number: /a/b/c/d.go:23
Lshortfile // final file name element and line number: d.go:23. overrides Llongfile
LstdFlags = Ldate | Ltime // initial values for the standard logger
)
In this sample program the destination for Trace is ioutil.Discard. This is a null device where all write calls succeed without doing anything. Therefore when you write using Trace, nothing appears in the terminal window.
Look at Info:
Info = log.New(infoHandle,
"INFO: ",
log.Ldate|log.Ltime|log.Lshortfile)
Init(ioutil.Discard, os.Stdout, os.Stdout, os.Stderr)
Info.Println("Special Information")
For Info os.Stdout is passed into Init for the infoHandle. This means when you write using Info, the message will appear on the terminal window, via standard out.
Last, look at Error:
Error = log.New(errorHandle,
"INFO: ",
log.Ldate|log.Ltime|log.Lshortfile)
Init(ioutil.Discard, os.Stdout, os.Stdout, os.Stderr)
Error.Println("Special Information")
This time os.Stderr is passed into Init for the errorHandle. This means when you write using Error, the message will appear on the terminal window, via standard error. However, passing these messages to os.Stderr allows other applications running your program to know an error has occurred.
Since any destination that support the io.Writer interface is accepted, you can create and use files:
if err != nil {
log.Fatalln("Failed to open log file", output, ":", err)
}
MyFile = log.New(file,
"PREFIX: ",
log.Ldate|log.Ltime|log.Lshortfile)
In the sample code, a file is opened and then passed into the log.New call. Now when you use MyFile to write, the writes go to file.txt.
You can also have the logger write to multiple destinations at the same time.
if err != nil {
log.Fatalln("Failed to open log file", output, ":", err)
}
multi := io.MultiWriter(file, os.Stdout)
MyFile := log.New(multi,
"PREFIX: ",
log.Ldate|log.Ltime|log.Lshortfile)
Here writes are going to the file and to standard out.
Notice the use of log.Fatalln in the handling of any error with OpenFile. The log package provides an initial logger that can be configured as well. Here is a sample program using log with the standard configuration:
import (
"log"
)
func main() {
log.Println("Hello World")
}
Here is the output:
If you want to remove the formatting or change it, you can use the log.SetFlags function:
import (
"log"
)
func main() {
log.SetFlags(0)
log.Println("Hello World")
}
Here is the output:
Now all the formatting has been removed. If you want to send the output to a different destination use the log.SetOutput:
import (
"io/ioutil"
"log"
)
func main() {
log.SetOutput(ioutil.Discard)
log.Println("Hello World")
}
Now nothing will display on the terminal window. You can use any destination that support the io.Writer interface.
Based on this example I wrote a new logging package for all my programs:
go get github.com/goinggo/tracelog
I wish I knew about log and loggers when I started writing Go programs. Expect to see a lot more of the log package from me in the future.
go语言使用官方的 log package 来记录日志的更多相关文章
- Visual Studio 2013 RTM 中文语言包官方下载地址发布
如果你下载的是英文版,你想安装一个中文的visual studio 2013,那么你大可不必重新下载安装visual studio 2013,因为微软提供了Visual Studio 2013 RTM ...
- 【原创】go语言学习(十一)package简介
目录 Go源码组织方式 main函数和main包 编译命令 自定义包 init函数以及执行行顺序 _标识符 Go源码组织方式 1. Go通过package的方式来组织源码 package 包名 注意: ...
- centos 6.4 /var/log/secure 不记录日志的問題
先确保日志服务开启:不妨重启下日志服务:由于目前RHEL 6/centos 6已经使用rsyslog替换了syslog.,所以不要在找/etc/syslog.conf了:重启命令:/etc/init. ...
- go语言碎片整理之标准库log
log Go语言内置的log包实现了简单的日志服务.本文介绍了标准库log的基本使用. 使用Logger log包定义了Logger类型,该类型提供了一些格式化输出的方法.本包也提供了一个预定义的“标 ...
- Go语言系列之标准库log
Go语言内置的log包实现了简单的日志服务.本文介绍了标准库log的基本使用. 使用Logger log包定义了Logger类型,该类型提供了一些格式化输出的方法.本包也提供了一个预定义的" ...
- Python 官方中文教程(简)
Python 官方教程 前言 这是一次系统学习Python官方教程的学习笔记 整个教程一共16章, 在学习过程中记录自己不知道的和一些重要的知识, 水平有限, 请指正. Python3.7 官方教程. ...
- Android与Swift iOS开发:语言与框架对比
Swift是现在Apple主推的语言,2014年新推出的语言,比Scala等“新”语言还要年轻10岁.2015年秋已经开源.目前在linux上可用,最近已经支持Android NDK:在树莓派上有Sw ...
- 【Go语言】集合与文件操作
本文目录 1.数据集合的主要操作 1_1.字典的声明 1_2.字典的初始化和创建 1_3.字典的访问和操作 1_4.其他类型的数据集 2.文件操作 2_1.文件操作概述os包和path包 2_2.文件 ...
- Go语言学习笔记(一) : 搭建Windows下的Go开发环境
最近突然对Go语言产生了兴趣,主要是因为在使用python的时候遇到了一些不爽的问题,然后发现了Go.Go是Google出的一个动态语言,语法和C++接近,性能也非常的好,而且还支持编译成exe发布, ...
随机推荐
- 2016天池-O2O优惠券使用预测竞赛总结
第一次参加数据预测竞赛,发现还是挺有意思的.本文中的部分内容参考第一名“诗人都藏在水底”的解决方案. 从数据划分.特征提取.模型设计.模型融合/优化,整个业务流程得到了训练.作为新手在数据划分和模型训 ...
- PS技巧汇总
一.gif图流程 1:素材图片a 图片b 2:窗口--->时间轴/动画 3:复制所选帧--->设置帧延迟 4:文件--->存储为WEB格式--->gif格式 二.批处理--- ...
- 常用的几个Dos命令-持续更新中
1.服务相关 (1).查看服务 C:\Windows\system32>net start 已经启动以下 Windows 服务: (2).启动服务 C:\Windows\system32> ...
- form表单清空、重置
form_live为formID <input type="button" value="重置" onclick="$('#form_live' ...
- DVWA--登录页面错误问题 469 | | PHP Fatal error: Uncaught exception 'PDOException' with message 'could not find driver' in C:\web\DVWA\dvwa\includes\dvwaPage.inc.php:469
// MySQL PDO Prepared Statements (for impossible levels) $db = new PDO('mysql:host=' . $_DVWA[ 'db_s ...
- HDU_1421_搬寝室_dp
题目链接:http://acm.hdu.edu.cn/showproblem.php?pid=1421 搬寝室 Time Limit: 2000/1000 MS (Java/Others) Me ...
- context switch
In computing, a context switch is the process of storing and restoring the state (more specifically, ...
- JAVA程序员面试笔试宝典1
1.为什么Java中有些接口没有任何方法? 这些没有任何方法声明的接口又被称为标识接口,标识接口对于实现它的类没有任何语义上的要求,它仅仅充当一个标识的作用,用来表明它的类属于一个特定的类型. 2.j ...
- TP中U方法详解
U方法常用于ThinkPHP里的页面跳转 官方称为url组装, 就是根据某种规则组成一个url地址,这个功能就叫组装. 在ThinkPHP里,系统提供了一个封装的函数来处理url的组装,俗称U方法. ...
- java8 foreach不能使用break、countinue
在学习1.8新特性的过程中,发现foreach中不可以使用break和countinue,然后我使用了return,结果如下图,对循环并没有影响. 百度一下,发现了一个不一样的回答 然后我就看了下源码 ...