if err == nil {
		fi, err := f.Stat()
		if err == nil {
			mode = fi.Mode() & 0777
		}
		name := f.Name()
		f.Close()
		os.Remove(name)
	}

	if err := os.Chmod(src, mode); err == nil {
		if err := os.Rename(src, dst); err == nil {
			if cfg.BuildX {
				sh.ShowCmd("", "mv %s %s", src, dst)
			}
			return nil
		}
	}

	return sh.CopyFile(dst, src, perm, force)

			if err == nil && info.Mode()&0222 != 0 {
				dirs = append(dirs, pathMode{path, info.Mode()})
			}
		}
		return nil
	})

	// Run over list backward to chmod children before parents.
	for i := len(dirs) - 1; i >= 0; i-- {
		os.Chmod(dirs[i].path, dirs[i].mode&^0222)
	}
}

// RemoveAll removes a directory written by Download or Unzip, first applying
// any permission changes needed to do so.

	// make them writable in order to remove content.
	filepath.WalkDir(dir, func(path string, info fs.DirEntry, err error) error {
		// chmod not only directories, but also things that we couldn't even stat
		// due to permission errors: they may also be unreadable directories.
		if err != nil || info.IsDir() {
			os.Chmod(path, 0777)
		}
		return nil
	})
	return robustio.RemoveAll(dir)
}

//
// Run the 'help' command within a script engine to view a list of the available
// commands.
func DefaultCmds() map[string]Cmd {
	return map[string]Cmd{
		"cat":     Cat(),
		"cd":      Cd(),
		"chmod":   Chmod(),
		"cmp":     Cmp(),
		"cmpenv":  Cmpenv(),
		"cp":      Cp(),
		"echo":    Echo(),
		"env":     Env(),

	// best-effort basis (ignoring failures).
	dir := filepath.Dir(old)
	info, err := os.Stat(dir)
	if err != nil {
		return err
	}
	if err := os.Chmod(dir, info.Mode()|writeBits); err != nil {
		return err
	}
	defer os.Chmod(dir, info.Mode())
	// Note: create the file writable, so that a racing go command
	// doesn't get an error before we store the actual data.

		if mode&0222 != 0 && (mode.IsDir() || mode.IsRegular()) {
			dirs = append(dirs, pathMode{path, mode})
		}
		return nil
	})

	// Run over list backward to chmod children before parents.
	for i := len(dirs) - 1; i >= 0; i-- {
		err := os.Chmod(dirs[i].path, dirs[i].mode&^0222)
		if err != nil {
			dirs = dirs[i:] // Only undo what we did so far.
			undo()
			fatalf("failed to make GOROOT read-only: %v", err)