memfd_create.cpp

#include <sys/mman.h>
#include <unistd.h>
#include <iostream>

int main()
{
    auto fd = memfd_create("mytmpfile", 0);
    if (fd < 0) throw std::runtime_error("memfd_create");

    std::string tmp_filename = "/proc/" + std::to_string(getpid()) + "/fd/" + std::to_string(fd);

    std::string msg = "Hello, World!\n";
    write(fd, msg.c_str(), msg.length());

    std::string cmd1 = "ls -l " + tmp_filename;
    system(cmd1.c_str());
    std::string cmd2 = "cat " + tmp_filename;
    system(cmd2.c_str());
    std::string cmd3 = "curl -s http://checkip.amazonaws.com/ >> " + tmp_filename;
    //std::string cmd3 = "curl -s -o " + tmp_filename + " http://checkip.amazonaws.com/";
    system(cmd3.c_str());

    lseek(fd, 0, SEEK_SET);
    char c;
    while (read(fd, &c, 1) > 0) {
        write(STDOUT_FILENO, &c, 1);
    }

    close(fd);
    return 0;
}