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| title | published | description | tags | cover_image | canonical_url | id |
|---|---|---|---|---|---|---|
| #90DaysOfDevOps - Let's explain the Hello World code - Day 9 | false | 90DaysOfDevOps - Let's explain the Hello World code | devops, 90daysofdevops, learning | null | null | 1048732 |
Hello World代码讲解
Let's explain the Hello World code
Go是如何工作的
How Go works
在第八天，我们完成了Go在工作站上的安装，同时创建了第一个Go程序。 On Day 8 we walked through getting Go installed on your workstation and we then created our first Go application.
在这节，我们将更深入学习这些代码，了解更多Go语言的内容。 In this section, we are going to take a deeper look into the code and understand a few more things about the Go language.
什么是编译？
What is Compiling?
在开始Hello World的6行代码之前，我们需要对编译有一些了解。 Before we get into the 6 lines of the Hello World code we need to have a bit of an understanding about compiling.
像Python、Java、Go和C++这类我们常用的编程语言都是高级语言(high-level languages)。这意味着它们是可以被人们直接阅读的。但当机器想去执行一个程序时，它需要将这些语言转换成机器能读懂的形式。而这个将人类能读懂的代码翻译成机器码的过程被成为编译(compiling)。 Programming languages that we commonly use such as Python, Java, Go and C++ are high-level languages. Meaning they are human-readable but when a machine is trying to execute a program it needs to be in a form that a machine can understand. We have to translate our human-readable code to machine code which is called compiling.
从上图可以看到，我们在第八天做的事情。我们创建了一个简单的Hello World程序main.go，然后使用go build main.go命令去将它编译成可执行文件。
From the above you can see what we did on Day 8 here, we created a simple Hello World main.go and we then used the command go build main.go to compile our executable.
什么是包(packages)？
What are packages?
包(package)，是在同一目录下编译到一起的源文件的集合。我们可以简单理解为，一个包是同一目录下的一堆*.go文件。还记得第八天的Hello文件夹吗？当你去学习更复杂的Go程序时，你可能会发现你有多个包含.go文件的文件夹(folder1, folder2和folder3...)，所以你的程序是由多个包构成的。 A package is a collection of source files in the same directory that are compiled together. We can simplify this further, a package is a bunch of .go files in the same directory. Remember our Hello folder from Day 8? If and when you get into more complex Go programs you might find that you have folder1 folder2 and folder3 containing different .go files that make up your program with multiple packages.
因此，我们可以通过使用包来复用别人的代码，并且不必将所有东西从头开始写。或许我们希望程序中有一个计算功能，你可能找到一个现成的、可以被导入的、包含了数学函数的Go包。长远来看，这种做法可以为你节省大量时间和精力。 We use packages so we can reuse other peoples code, we don't have to write everything from scratch. Maybe we are wanting a calculator as part of our program, you could probably find an existing Go Package that contains the mathematical functions that you could import into your code saving you a lot of time and effort in the long run.
Go鼓励你将代码组织成不同的包，从而方便后续复用和维护。 Go encourages you to organise your code in packages so that it is easy to reuse and maintain source code.
逐行来看Hello
Hello #90DaysOfDevOps Line by Line
让我们去到Hello文件夹里的main.go文件并看看每行在做什么。 Now let's take a look at our Hello #90DaysOfDevOps main.go file and walk through the lines.
在第一行，package main声明了这个文件属于一个叫main的包。所有的.go文件都需要被归属到一个包里，它们的开头会有package something的字样。
In the first line, you have package main which means that this file belongs to a package called main. All .go files need to belong to a package, they should also have package something in the opening line.
一个包可以任意命名。我们称main为这个包中的程序的起点，这是一个规则。(我需要更多地了解这条规则吗？)
A package can be named whatever you wish. We have to call this main as this is the starting point of the program that is going to be in this package, this is a rule. (I need to understand more about this rule?)
每当我们想要编译并运行代码时，我们都要告诉机器从那里开始执行。于是我们会编写一个叫main的函数。机器将会寻找名叫main的函数作为程序的入口。 Whenever we want to compile and execute our code we have to tell the machine where the execution needs to start. We do this by writing a function called main. The machine will look for a function called main to find the entry point of the program.
函数是一个可以在整个程序中使用的、执行特定任务的代码块。 A function is a block of code that can do some specific task for and can be used across the program.
你可以使用func声明任意名称的函数，只是在我们的例子中，我们需要命名main作为代码的起始点。
You can declare a function with any name using func but in this case we need to name it main as this is where the code starts.
接下来到第3行，import意味着你要在main程序里引入另一个包。fmt是Go提供的一个标准包，里边包含了将在第六行使用的Println()函数。也有很多标准库可以被应用在你的程序中，利用或重用它们可以省去你从头写起的麻烦。Go的标准包
Next we are going to look at line 3 of our code, the import, this basically means you want to bring in another package to your main program. fmt is a standard package being used here provided by Go, this package contains the Println()function and because we have imported this we can use this in line 6. There are a number of standard packages you can include in your program and leverage or reuse them in your code saving you the hassle of having to write from scratch. Go Standard Library
这里的Println()是一个将标准输出写入终端的一个方法，当程序被成功执行，信息将会被打印出来。你可以随意更改括号里的内容。
the Println() that we have here is a way in which to write to a standard output to the terminal where ever the executuable has been executed succesfully. Feel free to change the message in between the ().
总结
TLDR
- 第1行 = 这个文件位于名为
main的包中，因为其中包含程序的入口main，所以被称为main。 - 第3行 = 我们要导入fmt包后再在第六行使用
Println()。 - 第5行 = 实际的入口，
main函数。 - 第6行 = 这将在我们的系统上打印"Hello #90DaysOfDevOps"。
- Line 1 = This file will be in the package called
mainand this needs to be calledmainbecause includes the entry point of the program. - Line 3 = For us to use the
Println()we have to import the fmt package to use this on line 6. - Line 5 = The actual starting point, its the
mainfunction. - Line 6 = This will let us print "Hello #90DaysOfDevOps" on our system.
Resources
- StackOverflow 2021 Developer Survey
- Why we are choosing Golang to learn
- Jake Wright - Learn Go in 12 minutes
- Techworld with Nana - Golang full course - 3 hours 24 mins
- NOT FREE Nigel Poulton Pluralsight - Go Fundamentals - 3 hours 26 mins
- FreeCodeCamp - Learn Go Programming - Golang Tutorial for Beginners
- Hitesh Choudhary - Complete playlist
See you on Day 10.