How to check whether a file or directory exists?

I want to check the existence of file ./conf/app.ini in my Go code, but I can't find a good way to do that.

I know there is a method of File in Java: public boolean exists(), which returns true if the file or directory exists.

But how can this be done in Go?

// exists returns whether the given file or directory exists
func exists(path string) (bool, error) {
    _, err := os.Stat(path)
    if err == nil { return true, nil }
    if os.IsNotExist(err) { return false, nil }
    return false, err
}

Edited to add error handling.

You can use this :

if _, err := os.Stat("./conf/app.ini"); err != nil {
    if os.IsNotExist(err) {
        // file does not exist
    } else {
        // other error
    }
}

See : http://golang.org/pkg/os/#IsNotExist

More of an FYI, since I looked around for a few minutes thinking my question be a quick search away.

> How to check if path represents an existing directory in Go?

This was the most popular answer in my search results, but here and elsewhere the solutions only provide existence check. To check if path represents an existing directory, I found I could easily:

path := GetSomePath();
if stat, err := os.Stat(path); err == nil && stat.IsDir() {
    // path is a directory
}

Part of my problem was that I expected path/filepath package to contain the isDir() function.

Simple way to check whether file exists or not:

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

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

Sources:

• mattes made this gist on Aug 6 '14
• Sridhar Ratnakumar made this answer on Sep 21 '12

I use the following function to check my directories for any errors. It's very similar to previous answers, but I think not nesting ifs makes the code more clear. It uses go-homedir to remove ~ from directory paths and pkg/errors to return nicer error messages, but it would be easy to take them out if you don't need their functionality.

// validateDirectory expands a directory and checks that it exists
// it returns the full path to the directory on success
// validateDirectory("~/foo") -> ("/home/bbkane/foo", nil)
func validateDirectory(dir string) (string, error) {
    dirPath, err := homedir.Expand(dir)
    if err != nil {
        return "", errors.WithStack(err)
    }
    info, err := os.Stat(dirPath)
    if os.IsNotExist(err) {
        return "", errors.Wrapf(err, "Directory does not exist: %v\n", dirPath)
    }
    if err != nil {
        return "", errors.Wrapf(err, "Directory error: %v\n", dirPath)

    }
    if !info.IsDir() {
        return "", errors.Errorf("Directory is a file, not a directory: %#v\n", dirPath)
    }
    return dirPath, nil
}

Also, to repeat @Dave C's comment, if the reason you're checking a directory's existence is to write a file into it, it's usually better to simply try to open it an deal with errors afterwards:

// O_EXCL - used with O_CREATE, file must not exist
file, err := os.OpenFile(fileName, os.O_RDWR|os.O_CREATE|os.O_EXCL, 0666)
if err != nil {
    return errors.WithStack(err)
}
defer file.Close()

There is simple way to check whether your file exists or not:

if _, err := os.Stat("./conf/app.ini"); err != nil {
    if os.IsNotExist(err) {
        ..... //Shows error if file not exists
    } else {
       ..... // Shows success message like file is there
    }
}