使用os.Stat与os.MkdirAll进行检查

Question

I need to write to a file in a nested directory that may or may not exist.

At first, I checked if the folder existed via os.Stat, doing os.MkdirAll if it doesn't exist, and then opening and writing to a file.

I tried removing the os.Stat and just doing os.MkdirAll, and it appears to work - meaning os.MkdirAll is idempotent.

My question is, is there a benefit of doing the os.Stat check? Is it a much lighter operation than os.MkdirAll?

Answer 1

The first thing MkdirAll does is call os.Stat to check if the path exists and is a directory.

func MkdirAll(path string, perm FileMode) error {
    // Fast path: if we can tell whether path is a directory or file, stop with success or error.
    dir, err := Stat(path)
    if err == nil {
        if dir.IsDir() {
            return nil
        }
        return &PathError{"mkdir", path, syscall.ENOTDIR}
    }
    ...

From the docs:

If path is already a directory, MkdirAll does nothing and returns nil.

So no, you don't need to call os.Stat.