Minikube Code Analysis and go language-2

This is a creation in Article, where the information may have evolved or changed.

[TOC]

Go Language Introduction

2-Basic elements

printf Parameter Memo:

symbols	explain
%d	Decimal integer
%x,%o,%b	Integer in hexadecimal, octal, binary
%f,%g,%e	Floating-point number:3.141593, 3.141592653589793, 3.141593e+00
%t	Boolean:true or False
%c	Rune (Unicode code point)
%s	String
%q	Quoted string "abc" or rune ' C '
%v	Any value in a natural format
%T	Type of any value
%%	Literal percent sign (no operand)

Named

Naming rules are similar to C.

GoThere are 25 keywords that cannot be used as a name:

Break	Default	Func	Interface	Select
Case	Defer	Go	Map	struct
Chan	Else	Goto	Package	Switch
Const	Type	If	Range	Fallthrough
Continue	For	Import	Return	Var

GoThere are also 37 pre-declared names for built-in constants, types, and functions (can be overridden):

Constants:  true, false, iota, nilTypes:      int int8 int16 int32 int64            uint uint8 uint16 uint32 uint64 uintptr            float32 float64 complex64 complex128            bool byte rune string error        Functions:  make len cap new append copy close delete             complex real imag             panic recover

• The first character of a name determines its visibility. Uppercase characters indicate public. The package name is always lowercase characters.

• The name length is not limited, but tends to shorter names, named using Hump style.

• Variable declarations can be sorted by list, such asvar b, f, s = true, 2.3, "four"

• Support tuple assignment , such asi, j = j, i // swap values of i and j

• A simplified form of declaration must declare at least one new variablevar i, j int; i, j := 1, 2 // compile error: no new variables

• The pointer C is similar to the value that takes the * & address, such as*p++

++ec2.go++ (add command line arguments)

package mainimport ( // 导入多个包的常用形式    "fmt"    "flag"    "strings")var n = flag.Bool("n", false, "omit trailing newline")var sep = flag.String("sep", " ", "separator")func main() {    flag.Parse()    fmt.Print(strings.Join(flag.Args(), *sep))    if !*n { fmt.Println() }}

Points

• newand delete C++ similar, but they are functions

• The variable life cycle C is Java consistent with or as the dominant language, and new the allocated object may be in the stack

• An implicit assignment such asmedals := []string{"bronze", "silver", "gold"}

• typeDeclares a new type, does not change its value, supports operations of its underlying type

• Package mechanism similar Java to the path of the package corresponding file

• The package also embodies the namespace namespace , similar toPython

• The first character capitalization is the entity that is exported (such as variables, functions, types, and so on)

• Follow the package declaration as a document description of the package, similar to the Python

• The introduction of unused packages can lead to compilation errors

• func init() { /* ... */ }is the initialization function of the file/package

• Scope ranges are similar to other languages, but Go there are some strange uses for syntax reasons

if f, err := os.Open(fname); err != nil { // compile error: unused: f    return err}f.ReadByte() // compile error: undefined f

  var cwd stringfunc init () {CWD, err: = OS. GETWD ()//compile ERROR:UNUSED:CWD if err! = Nil {log. Fatalf ("OS. GETWD failed:%v ", Err)}}