How to search a directory for all text files - c++

Question

this is my first official post here, so let's begin:
I need to make a method in my class Searcher to find all the text files in a directory and add them to a vector.
I figured, when I find another directory, to call the function recursively so that I could do my search for the .txt files in that directory aswell..and so on.
So here is how I did it:
void IndexIt(string direktorij) {
string pom(direktorij);
DIR* dir = opendir(direktorij.c_str());
if(dir==NULL) {
cout<<"Ne mogu otvoriti direktorij!";
return;
}
struct dirent *file;
while ((file = readdir(dir))!=NULL) {
string filename(file->d_name);
if (filename.substr(filename.length()-4)== ".txt") {
AddTheFilenameInVector(filename); //made a simple method to add the filename in a vector
} //so I could save it for later use
string filepath = pom + "\\" + filename;
try {
struct stat filedata;
stat (filepath.c_str(), &filedata);
if (S_ISDIR(filedata.st_mode)) {
IndexIt(filepath);
}
}
catch(...) {
int b(2);
cout<<" "<<b*2;
}
}
}
When I try to build it, I just get the caught exceptions in the try-catch block. I must be doing something wrong and I suspect on my recursive calling of IndexIt(filepath).
I've tried with other alternatives such as
string directory;
const size_t last_slash_idx = filename.rfind('\\');
if (std::string::npos != last_slash_idx) {
directory = filename.substr(0, last_slash_idx);
}
to get the filepath, also didn't resolve my issue.
I hope I explained it well enough.
I forgot to say that any libraries except those bellow are not allowed.
#include <iostream>
#include <vector>
#include <string>
#include <stdio.h>
#include <string.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <dirent.h>
#include <fstream>