C++ FILE readInt函数？

#include<iostream>
#include <fstream>

int readInt(std::ifstream &input_file) {
    int number;
    input_file >> number;
    return number;
}

int main() {
    std::ifstream input_file("input.txt");
    if (!input_file) {
        std::cerr << "Error opening file"<< std::endl;
        return 1;
    }

    int number = readInt(input_file);
    std::cout << "Read integer: "<< number<< std::endl;

    input_file.close();
    return 0;
}