How Can I Check for File Existence in Go?

Checking File Existence in Go

When working with files in Go, it's often necessary to determine if a file exists before proceeding with further operations. Unlike Python's os.path.exists, the Go standard library doesn't provide a direct function for this purpose.

Idiomatic Way to Check File Existence

To check if a file doesn't exist:

if _, err := os.Stat("/path/to/whatever"); errors.Is(err, os.ErrNotExist) {
  // path/to/whatever does not exist
}

To check if a file exists:

if _, err := os.Stat("/path/to/whatever"); err == nil {
  // path/to/whatever exists

} else if errors.Is(err, os.ErrNotExist) {
  // path/to/whatever does *not* exist

} else {
  // Schrodinger: file may or may not exist. See err for details.

  // Therefore, do *NOT* use !os.IsNotExist(err) to test for file existence
}

Explanation

The os.Stat function returns a FileInfo object representing the file's attributes or an error if the file doesn't exist. By using the errors.Is function to compare the error to os.ErrNotExist, you can distinguish between the file not existing and other errors.

Caution

Avoid using the negation of os.IsNotExist (e.g., !os.IsNotExist(err)) to test for file existence, as it can lead to unexpected behavior in some cases.

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