DIR和dirent 用来获取某文件夹目录内容的结构体

DIR结构体：

struct __dirstream
{
    void *__fd;
    char *__data;
    int __entry_data;
    char *__ptr;
    int __entry_ptr;
    size_t __allocation;
    size_t __size;
    __libc_lock_define (, __lock)
};
typedef struct __dirstream DIR;

函数 DIR *opendir(const char *pathname)，即打开文件目录，返回的就是指向DIR结构体的指针，而该指针由以下几个函数使用:

struct dirent *readdir(DIR *dp);//读取到的文件名存储在结构体dirent的d_name成员中

void rewinddir(DIR *dp);

int closedir(DIR *dp);

long telldir(DIR *dp);

void seekdir(DIR *dp,long loc);

dirent结构体：

#include <dirent.h>

struct dirent
{
    long d_ino;               /* inode number 索引节点号 */
    off_t d_off;              /* offset to this dirent 在目录文件中的偏移 */
    unsigned short d_reclen;  /* length of this d_name 文件名长 */
    unsigned char d_type;     /* the type of d_name 文件类型 */
    char d_name [NAME_MAX+1]; /* file name (null-terminated) 文件名，最长256字符 */
}

代码实例：

获取二级目录下所有与.png文件同名的.pb文件列表

void readInputFileList(std::string in_dir, std::vector<std::string> &file_list)
{
    DIR *dir = NULL;
    if ((dir = opendir(in_dir.c_str())) == NULL)
        std::cout << in_dir << ": Open dir failed." << std::endl;

    struct dirent *ptr;
    while (ptr = readdir(dir))
    {
        if (ptr->d_name[0] == ".")
			continue;
        else if (ptr->d_type == DT_DIR)
        {
            std::string path = in_dir + "/";
            path += ptr->d_name;
            DIR *d = NULL;
            if ((d = opendir(path.c_str())) == NULL)
                std::cout << path << ": Open dir failed." << std::endl;

            struct dirent *p;
            while (p = readdir(d))
            {
                if (p->d_name[0] == "." || p->d_type == DT_DIR)
                    continue;
                std::string image_name(p->d_name);
                if (image_name.substr(image_name.size() - 4) != ".png")
                    continue;
                std::string pb_name = image_name.substr(0, image_name.size() - 3) + "pb";
                std::string pb_path = path + "/" + pb_name;
                if (access(pb_path.c_str(), 0) != 0)
                    continue;
                file_list.push_back(pb_path);
            }
        }
        else
            std::cout << ptr->d_name << ": Can not contain file." << std::endl;
	}
	sort(file_list.begin(), file_list.end());
}