First contact Go Development of , Roll up ！！！

1. Get current go File directory

Just started recently GORM （go Of ORM frame ）, It is found that... Is not automatically generated according to database fields Object（ stay Go The corresponding in is struct ） Tool class of , So I rolled one of my own hands , It can be used , In the process of writing, I happen to encounter the problem of obtaining the current go The path of the file , So I checked the documents , I was surprised when I found it , little does one think GO It's such a grammar , although Java This function is also available in , But it doesn't feel coquettish enough ！！ Ha ha ha ！

//  Source location ： os/getwd.go

//  Get current  go  The directory of the file 
path, err := os.Getwd()
if err != nil {
    
    log.Println(err)
} else {
    
	fmt.Println(path)
}

2. Get the file path separator of the system

Because the system is different , Some people are Windows（ The separator is //）, Some people are Linux（ The separator is \）, Others are Mac（ The separator is \）. If you want to write cross platform code generation tools that are compatible , You need compatible path separators instead of hard coding them in . If this is true , Go It has also been taken into account , And the calling methods of different systems are the same .

// Windwos  Separator source code location ： os/path_windows.go
// Linux  and  Mac  Separator source code location ： os/path_unix.go

//  Usage mode (Go  Will judge according to the actual system )
separator := string(os.PathSeparator)

Here's the problem , When you look in the code, you will find PathSeparator It's not a string , It's a character . stay Go in , The character type is rune type ,rune yes int32 The nickname , So we need to use string() Function to a string , And then you can use it .

package os

const (
	PathSeparator     = '/' // OS-specific path separator
	PathListSeparator = ':' // OS-specific path list separator
)

package os

const (
	PathSeparator     = '\\' // OS-specific path separator
	PathListSeparator = ';'  // OS-specific path list separator
)

3. Go Determine if a file or directory exists

It's a pit here , The main nausea is Go Of os There is one in the bag IsNotExist function , One more IsExist function ; But actually IsExist And IsNotExist It's not an opposite relationship , That is to use IsNotExist by false The place of , Use IsExist for true, It feels like a pit . If you want to correctly judge whether a file or directory exists , Remember not to use IsExist, But use IsNotExist .

The right way to use ：

// UNIX  Design principles ： Everything is a document , In other words, directories and files are files . Can be judged in the following way 

// file, err := os.Stat("/Users/roc/Downloads/")
file, err := os.Stat("/Users/roc/Downloads/download.jpg")
if err != nil {
    
	if os.IsNotExist(err) {
      //  It cannot be replaced by  os.IsExist(err)
		log.Fatalln(" The file does not exist ")
	}
} else {
    
	log.Println(" The file exists ",file.Name())
}

Counter example （ The wrong way to use ）：

file, err := os.Stat("/Users/roc/Downloads/download.jpg")
if os.IsExist(err) {
      //  It cannot be replaced by  os.IsExist(err)
	log.Fatalln(" The file does not exist ")
}

//  When  err == nil  It means that the file already exists , Whether the above file exists or not will not be judged 

A separate article will be written later to distinguish IsExist And IsNotExist .

Continuous updating ing ！！！

Personal blog ： Roc’s Blog