int readDir(string directory, vector<string> &fileList) 
//directory is the name of a direcotry 
//fileList is an empty vector
 
DIR *dir;
struct dirent *ent;
 
if((dir = opendir(director.c_str()) == NULL){
     cout<<"Invalid Directory"<<endl;
     exit(1);
}
while((ent = readdir(dir)) != NULL){
     fileList.push_back(string(ent->d_name));
}
closedir(dir);
return 0;
}

DirTraveler traveler;
vector<string>foo;
traveler.travelDirectoryRecursive("bar", &foo);
for (int i=0; i<foo.size(); ++i)
    cout << foo[i].c_str() << endl;

#ifndef DIRTRAVELER_H
#define DIRTRAVELER_H
 
#include <string>
#include <vector>
 
using namespace std;
 
/// Directory traveler (mostly used with zgui manager)
 
class DirTraveler
{
    public:
        DirTraveler();
        virtual ~DirTraveler();
 
        vector<string> travelDirectory(string directory);
        void travelDirectoryRecursive(string directory, vector<string> *fullList);
    protected:
    private:
};
 
#endif // DIRTRAVELER_H

#include "DirTraveler.h"
#include <stdio.h>
#include <string.h>
#include <sstream>
#include <sys/types.h>
#include <dirent.h>
#include <vector>
 
using namespace std;
 
DirTraveler::DirTraveler()
{
    //ctor
}
 
DirTraveler::~DirTraveler()
{
    //dtor
}
 
vector<string> DirTraveler::travelDirectory(string directory)
{
    // travel thru a directory gathering all the file and directory naems
    vector<string> fileList;
    DIR *dir;
    struct dirent *ent;
 
    // open a directory
    if ((dir=opendir(directory.c_str())) != NULL)
    {
        while((ent=readdir(dir)) != NULL) // loop until the directory is traveled thru
        {
            // push directory or filename to the list
            fileList.push_back(ent->d_name);
        }
        // close up
        closedir(dir);
    }
    //return the filelust
    return fileList;
}
 
void DirTraveler::travelDirectoryRecursive(string directory, vector<string> *fullList)
{
    // get the "root" directory's directories
    vector<string> fileList = travelDirectory(directory);
 
    // loop thru the list
    for (vector<string>::iterator i=fileList.begin(); i!=fileList.end(); ++i)
    {
        // test for . and .. directories (this and back)
        if (strcmp((*i).c_str(), ".") &&
            strcmp((*i).c_str(), ".."))
        {
            // i use stringstream here, not string = foo; string.append(bar);
            stringstream fullname;
            fullname << directory << "/" << (*i);
 
            fullList->push_back(fullname.str());
 
            travelDirectoryRecursive(fullname.str(), fullList);
        }
    }
}