Golang : Test file read write permission example

Problem :

You need to test if a file has the correct write or read permission before performing write or read operation. How to do that?

Solution :

Use os.OpenFile() function and check the error with os.IsPermission() to see if a file has permission denied error.

For example :

To test if a file has write permission : (do not run this program as root or super user)

 package main

 import (
 "fmt"
 "os"
 )

 func main() {
 fileName := "file.txt"

 file, err := os.OpenFile(fileName, os.O_WRONLY, 0666)
 if err != nil {
 if os.IsPermission(err) {
 fmt.Println("Unable to write to ", fileName)
 fmt.Println(err)
 os.Exit(1)
 }

 }
 file.Close()

 }

To test if a file has read permission : (do not run this program as root or super user)

 package main

 import (
 "fmt"
 "os"
 )

 func main() {
 fileName := "file.txt"

 file, err = os.OpenFile(fileName, os.O_RDONLY, 0666)
 if err != nil {
 if os.IsPermission(err) {
 fmt.Println("Unable to read from ", fileName)
 fmt.Println(err)
 os.Exit(1)
 }
 }
 file.Close()
 }

References :

https://golang.org/pkg/os/#IsPermission

https://www.socketloop.com/tutorials/golang-check-if-a-file-exist-or-not