gistfile1.txt

#include <thread>
#include <iomanip>
#include <iostream>
#include <sys/types.h>
#include <sys/shm.h>
#include <sys/ipc.h>
int main()
{
    static auto now = +[](std::ostream &os)->std::ostream& {
        auto now   = std::chrono::high_resolution_clock::now();
        auto now_c = std::chrono::system_clock::to_time_t(now);
        auto us    = std::chrono::duration_cast<std::chrono::microseconds>(
                      now.time_since_epoch())
                      .count()
                  % 1000000;
        return os << std::put_time(std::localtime(&now_c), "%F %T") << '.'
                  << std::setw(6) << std::setfill('0') << us;
    };
    std::thread t1{[] {
        while (shmat(0, 0, SHM_RDONLY) == (char*)-1)
            ;
        std::cout << now << " shmat(0) succeeded at " << std::endl;
    }};
    std::thread t2{[] {
        while (true)
        {
            auto id = shmget(IPC_PRIVATE, 1000, 0600 | IPC_CREAT | IPC_EXCL);
            if (id < 0)
            {
                std::cout << "shmget failed" << std::endl;
                break;
            }
            auto ptr = shmat(id, nullptr, 0);
            if (ptr == (char*)-1)
            {
                std::cout << "shmat(" << id << " failed" << std::endl;
                break;
            }
            shmid_ds info;
            if (shmctl(id, IPC_STAT, &info) < 0)
            {
                std::cout << "shmctl IPC_STAT failed" << std::endl;
                break;
            }
            if (info.shm_nattch != 1)
            {
                std::cout << now << " shmget(IPC_PRIVATE) created seg with id " << id << ", size " << info.shm_segsz << " and nattach = " << info.shm_nattch << " at " << std::endl;
                break;
            }
            if (shmdt(ptr) == -1)
            {
                std::cout << "shmdt(" << ptr << " failed" << std::endl;
                break;
            }
            if (shmctl(id, IPC_RMID, nullptr) < 0)
            {
                std::cout << "shmctl IPC_RMID failed" << std::endl;
                break;
            }
        }
    }};
    t1.join();
    t2.join();
}