cpp class constructor initialize list and override cout

//book.h
#pragma once
#include <iostream>

class book
{
public:
    int idx;
    std::uint64_t id;
    std::string author;
    std::string content;
    std::string comment;
    std::string isbn;
    std::string summary;
    std::string topic;
    book(int idx_vlaue, std::uint64_t id_value, std::string author_value, std::string content_value, std::string isbn_value,
         std::string summary_value, std::string topic_value) : idx(idx_vlaue), id(id_value), author(author_value), content(content_value),
                                                               isbn(isbn_value), summary(summary_value), topic(topic_value)
    {
    }

    friend std::ostream &operator<<(std::ostream &os, const book &bk); 
};

std::ostream &operator<<(std::ostream &os, const book &bk)
{
    os<<"Idx:"<<bk.idx<<",id:"<<bk.id<<",author:"<<bk.author<<","<<bk.content<<",comment:"<<bk.comment<<",isbn:"
    <<bk.isbn<<",summary:"<<bk.summary<<",topic:"<<bk.topic<<std::endl; 
    return os;
}

The critical part of override cout is 

//declare override method cout as ostream friend method in class
friend std::ostream &operator<<(std::ostream &os, const book &bk);

//implement the overriden friendly method
std::ostream &operator<<(std::ostream &os, const book &bk)
{
    os<<"Idx:"<<bk.idx<<",id:"<<bk.id<<",author:"<<bk.author<<","<<bk.content<<",comment:"<<bk.comment<<",isbn:"
    <<bk.isbn<<",summary:"<<bk.summary<<",topic:"<<bk.topic<<std::endl; 
    return os;
}

The whole code as below

//book.h
#pragma once
#include <iostream>

class book
{
public:
    int idx;
    std::uint64_t id;
    std::string author;
    std::string content;
    std::string comment;
    std::string isbn;
    std::string summary;
    std::string topic;
    book(int idx_vlaue, std::uint64_t id_value, std::string author_value, std::string content_value, std::string isbn_value,
         std::string summary_value, std::string topic_value) : idx(idx_vlaue), id(id_value), author(author_value), content(content_value),
                                                               isbn(isbn_value), summary(summary_value), topic(topic_value)
    {
    }

    friend std::ostream &operator<<(std::ostream &os, const book &bk); 
};

std::ostream &operator<<(std::ostream &os, const book &bk)
{
    os<<"Idx:"<<bk.idx<<",id:"<<bk.id<<",author:"<<bk.author<<","<<bk.content<<",comment:"<<bk.comment<<",isbn:"
    <<bk.isbn<<",summary:"<<bk.summary<<",topic:"<<bk.topic<<std::endl; 
    return os;
}


// main.cpp
#include <algorithm>
#include <chrono>
#include <ctime>
#include <fstream>
#include <iomanip>
#include <iostream>
#include <map>
#include <mutex>
#include <queue>
#include <sstream>
#include <thread>
#include <uuid/uuid.h>
#include <vector>
#include "book.h"

std::string get_time_now()
{
    std::chrono::time_point<std::chrono::high_resolution_clock> now = std::chrono::high_resolution_clock::now();
    time_t raw_time = std::chrono::high_resolution_clock::to_time_t(now);
    struct tm tm_info = *localtime(&raw_time);
    auto seconds = std::chrono::duration_cast<std::chrono::seconds>(now.time_since_epoch());
    auto mills = std::chrono::duration_cast<std::chrono::milliseconds>(now.time_since_epoch());
    auto micros = std::chrono::duration_cast<std::chrono::microseconds>(now.time_since_epoch());
    auto nanos = std::chrono::duration_cast<std::chrono::nanoseconds>(now.time_since_epoch());
    std::stringstream ss;
    ss << std::put_time(&tm_info, "%Y%m%d%H%M%S")
       << "_"
       << std::setw(3) << std::setfill('0') << (mills.count() - seconds.count() * 1000)
       << std::setw(3) << std::setfill('0') << (micros.count() - mills.count() * 1000)
       << std::setw(3) << std::setfill('0') << (nanos.count() - micros.count() * 1000);
    return ss.str();
}

char *uuid_value = (char *)malloc(40);
char *get_uuid_value()
{
    uuid_t new_uuid;
    uuid_generate(new_uuid);
    uuid_unparse(new_uuid, uuid_value);
    return uuid_value;
}

void queue_demo(const int &len)
{
    std::queue<book> que;
    for (int i = 0; i < len; i++)
    {
        que.emplace(i, static_cast<std::uint64_t>(i * i * i * i * i), get_uuid_value(), get_uuid_value(), get_uuid_value(), get_uuid_value(),
                    get_uuid_value());
    }
    std::cout << "queue size:" << que.size() << std::endl;

    while (!que.empty())
    {
        book bk = que.front();
        std::cout << bk;
        que.pop();
    }
    std::cout << get_time_now() << ",finish in " << __FUNCTION__ << std::endl;
}

int main(int args, char **argv)
{
    queue_demo(atoi(argv[1]));
    std::cout << get_time_now() << ",thread id:" << std::this_thread::get_id() << ",in " << __FUNCTION__ << std::endl;
}

Compile

g++-12 -std=c++2a -I. *.cpp -o h1 -luuid -lpthread

Run

./h1 10