In golang os.OpenFile doesn't return os.ErrNotExist if file does not exist

Question

I'm trying to open a file and I'd like to know if it doesn't exist to react. But the error

os.OpenFile(fName, os.O_WRONLY, 0600)

returns when the file does not exist is different than os.ErrNotExists

os.ErrNotExists -> "file does not exist"
err.(*os.PathError).Err -> "no such file or directory"

os.Stat also return the same error if the file is not there. Is there a predefined error I can compare to instead of having to do it by hand?

peterSO · Accepted Answer · 2015-10-28 18:47:36Z

Package os

func IsExist
func IsExist(err error) bool
IsExist returns a boolean indicating whether the error is known to report that a file or directory already exists. It is satisfied by ErrExist as well as some syscall errors.

func IsNotExist
func IsNotExist(err error) bool
IsNotExist returns a boolean indicating whether the error is known to report that a file or directory does not exist. It is satisfied by ErrNotExist as well as some syscall errors.

Use the os.IsNotExist function. For example,

package main

import (
    "fmt"
    "os"
)

func main() {
    fname := "No File"
    _, err := os.OpenFile(fname, os.O_WRONLY, 0600)
    if err != nil {
        if os.IsNotExist(err) {
            fmt.Print("File Does Not Exist: ")
        }
        fmt.Println(err)
    }
}

Output:

File Does Not Exist: open No File: No such file or directory

Perry · Accepted Answer · 2022-08-02 18:15:22Z

5

Originally posted as an anonymous suggested edit to the other answer:

As of Go 1.17, the preferred way to check for this error is:

errors.Is(err, fs.ErrNotExist)

Source

answered Aug 2, 2022 at 18:15

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