c++ program list all files in the Directory

/*c++ program list all files in the Directory
  2020-8-31
*/
#include <iostream>
#include <string>
#include <vector>
#include <fstream>
#include <ros/ros.h>
#include <geometry_msgs/Pose.h>
#include <dirent.h>

//by reference : vector< >& 
void listFile(std::vector<std::string>& file_name){
    struct dirent *entry;
    std::string path("/home/robot/data/data.001");
    DIR *dir=opendir(path.c_str());
    if(!dir){
        std::cout<<"can't open "<<path;
        return;
    }
    while((entry=readdir(dir))!=NULL){
    //get all file name in a directory without getting "." and ".." .. and .. are actually hard links in filesystems. 
They are needed so that you can specify relative paths, based on some reference path (consider "../sibling/file.txt"). 
Since these hard links are actually existing in the filesystem, it makes sense for readdir to tell you about them. 
(actually the term hard link just means some name that is indistinguishable from the actual directory referred to: 
they both point to the same inode in the filesystem).

        if(std::string(entry->d_name)!="."&&std::string(entry->d_name)!=".."){
            //这里排查了很久的错误，若文件名不全会导致打不开文件！
            file_name.push_back(path+"/"+std::string(entry->d_name));
        }
    }
    closedir(dir);
}
void print(const std::vector<geometry_msgs::Pose>& g){
    //iterating over std::vector
      for (const auto& it:g){ 
    std::cout<<"pos.x:"<<it.position.x<<std::endl
         <<"pos.y:"<<it.position.y<<std::endl
         <<"pos.z:"<<it.position.z<<std::endl
         <<"orientation.x:"<<it.orientation.x<<std::endl
         <<"orientation.y:"<<it.orientation.y<<std::endl
         <<"orientation.z:"<<it.orientation.z<<std::endl
         <<"orientation.w:"<<it.orientation.w<<std::endl;
    }
}

int main(){
    std::vector<std::string> file_name;
    listFile(file_name);

    std::sort (file_name.begin(),file_name.end(),std::greater<std::string>());
    //use vector 为了后期扩容
    std::vector<geometry_msgs::Pose> gps_;
    for(const auto& file : file_name){
        std::ifstream ifs (file.c_str(), std::ios::binary | std::ios::in);
        std::cout<<file.c_str()<<std::endl;
        if (ifs.is_open()) {
            size_t size = 0;
            ifs.read(reinterpret_cast<char *>(&size), sizeof(int));
            gps_.resize(size);
            ifs.read(reinterpret_cast<char *>(&gps_[0]), sizeof(geometry_msgs::Pose) * size);
            ifs.close();
        print(gps_);
        }
        else
            std::cout<<"can't open"<<std::endl;
    }
    return 0;
}