[ 常見問題 ] Check If a File Exists Before Using It

 Source From Here

How-To
In this basic example, we check to see if a file exists before interacting with it (otherwise something’s not going to work as expected). We leverage the power of the os standard library and first use the Stat() function, which although it’s usually used to get information about a file, we’re only looking at the errors.

We can’t just check for err == nil because any number of errors could be returned so we pass it to IsNotExists() to confirm that it’s an error because the file does not exist:

view plaincopy to clipboardprint?

1. package main  
2.   
3. import (  
4.     "fmt"  
5.     "os"  
6. )  
7.   
8. func main() {  
9.     if fileExists("example.txt") {  
10.         fmt.Println("Example file exists")  
11.     } else {  
12.         fmt.Println("Example file does not exist (or is a directory)")  
13.     }  
14. }  
15.   
16. // fileExists checks if a file exists and is not a directory before we  
17. // try using it to prevent further errors.  
18. func fileExists(filename string) bool {  
19.     info, err := os.Stat(filename)  
20.     if os.IsNotExist(err) {  
21.         return false  
22.     }  
23.     return !info.IsDir()  
24. }