如何在循环内的变量中获取文件名？

import os

directory = '/path/to/directory'
for filename in os.listdir(directory):
    if os.path.isfile(os.path.join(directory, filename)):
        print(filename)

import java.io.File;

String directory = "/path/to/directory";
File folder = new File(directory);
File[] files = folder.listFiles();
for (File file : files) {
    if (file.isFile()) {
        System.out.println(file.getName());
    }
}

#include <iostream>
#include <dirent.h>

std::string directory = "/path/to/directory";
DIR* dir;
struct dirent* entry;

if ((dir = opendir(directory.c_str())) != NULL) {
    while ((entry = readdir(dir)) != NULL) {
        if (entry->d_type == DT_REG) {
            std::cout << entry->d_name << std::endl;
        }
    }
    closedir(dir);
}