问C++删除所有文件和子文件夹，但保留目录本身

EN

void deleteDirectoryContents(const std::string& dir_path)
{
    for (const auto& entry : std::filesystem::directory_iterator(dir_path)) 
        std::filesystem::remove_all(entry.path());
}

#include <filesystem>

namespace fs = std::filesystem;

void delete_dir_content(const fs::path& dir_path) {
    for (auto& path: fs::directory_iterator(dir_path)) {
        fs::remove_all(path);
    }
}

#include <dirent.h>

bool cleanDirectory(const std::string &path){
    struct dirent *ent;
    DIR *dir = opendir(path.c_str());
    if (dir != NULL) {
        /* remove all the files and directories within directory */
        while ((ent = readdir(dir)) != NULL) {
            std::remove((path + ent->d_name).c_str());
        }
        closedir (dir);
    } else {
        /* could not open directory */
        return false;
    }
    return true;
}