Error: Expression must have integral or unscoped enum type while reading d_name

I need to check whether file name ends with .config present in a folder. So I'm using below code.

#include "stdafx.h"
#include <stdio.h>
#include <sys/types.h>
#include <dirent.h>
#include <fstream>
#include <iostream>
using namespace std;


void main(){
DIR *dirp;
struct dirent *dp;
char prnStr[254];

if ((dirp = opendir("D:/New folder/")) == NULL) {
        cout << "Could not open directory!!";
        return;
    }
    if ((dp = readdir(dirp)) != NULL) {
        prnStr << dp->d_name;
        size_t findprn = prnStr.str().find(".config");

        if ((int)findprn != -1) {
            cout << "Found .config File!!!!!";
        }
        else {
            cout << "No .config files detected at this time...";
        }
    }
   }

Getting error at this line prnStr << dp->d_name; as Error: Expression must have integral or unscoped enum type

It sounds like you want to use a std::ostringstream. Change prnStr to be such an object.

Change the line

char prnStr[254];

to

std::ostringstream prnStr;

On a separate note, you are looking for a .config file. Maybe you should change the line

        cout << "Found .prn File!!!!!";

to

        cout << "Found .config File!!!!!";

and change

        cout << "No .prn files detected at this time...";

to

        cout << "No .config files detected at this time...";