Обработка файлов

#include <iostream>
#include <fstream>
#include <numeric>
#include <vector>
 
struct Human
{
    static const int MAN = 1;
    std::string name;
    int sex;
    double length;
};
 
std::istream &operator >> (std::istream &is, Human &human)
{
    is >> human.name
       >> human.sex
       >> human.length;
    return is;
}
 
std::ostream &operator << (std::ostream &os, const Human &human) {
    os << human.name    << ' '
       << human.sex     << ' '
       << human.length  << "\n";
    return os;
}
 
int main(int argc, char* argv[])
{
    setlocale(LC_ALL, "");
 
    const std::string srcDataFile = R"(/home/.../srcData.txt)";
    const std::string dstDataFile = R"(/home/.../dstData.txt)";
 
    std::ifstream fileIn{srcDataFile, std::ios_base::in};
    if (!fileIn) {
        std::cerr << "Error read file: " << srcDataFile << "\n"; return 1;
    }
 
    std::ofstream fileOut{dstDataFile, std::ios_base::out};
    if (!fileOut) {
        std::cerr << "Error create or write file: " << dstDataFile << "\n"; return 1;
    }
 
    std::vector<double> lengths;
    for(Human hm; fileIn >> hm; ) {
        if (hm.sex == Human::MAN) {
            fileOut << hm;
            lengths.push_back(hm.length);
        }
    }
 
    auto averageLen = std::accumulate(
            lengths.begin(),
            lengths.end(),
            0.0
    ) / lengths.size();
 
    fileOut << "Average length: " << averageLen;
 
    return 0;
}