问从C++暂停和恢复外壳进程

EN

int system2(const char * command)
{
    int p_stdin[2];
    int p_stdout[2];
    int pid;

    if (pipe(p_stdin) == -1)
        return -1;

    if (pipe(p_stdout) == -1) {
        close(p_stdin[0]);
        close(p_stdin[1]);
        return -1;
    }

    pid = fork();

    if (pid < 0) {
        close(p_stdin[0]);
        close(p_stdin[1]);
        close(p_stdout[0]);
        close(p_stdout[1]);
        return pid;
    } else if (pid == 0) {
        close(p_stdin[1]);
        dup2(p_stdin[0], 0);
        close(p_stdout[0]);
        dup2(p_stdout[1], 1);
        dup2(::open("/dev/null", O_RDONLY), 2);
        /// Close all other descriptors for the safety sake.
        for (int i = 3; i < 4096; ++i)
            ::close(i);

        setsid();
        execl("/bin/sh", "sh", "-c", command, NULL);
        _exit(1);
    }

    close(p_stdin[0]);
    close(p_stdout[1]);

    
    return pid;
}

int main()
{
    // The process prints on file allowing me to figure out whether the process is paused / stopped, or is running
    const char * command = "for i in {1..1000}; do echo $i >> /Users/remi/test/data.txt; sleep 1s;done";

    // Run the command and record pid
    auto pid = system2(command);
    std::cout << "pid = " << pid << "\n";  
    // with this pid, I could ensure that `ps -p <pid>` returns the correct command

    std::cout << "process should be running!\n"; // It is!

    // wait
    std::this_thread::sleep_for(std::chrono::seconds(10));

    // pause
    kill(pid, SIGTSTP);
    std::cout << "process should be paused!\n"; // But it is not!

    // wait
    std::this_thread::sleep_for(std::chrono::seconds(10));

    // resume process
    kill(pid, SIGCONT);
    std::cout << "process should be running!\n"; // Sure, it is as it has never been stopped

    // wait 
    std::this_thread::sleep_for(std::chrono::seconds(10));

    // Kill process
    kill(pid, SIGSTOP);
    std::cout << "process should be stopped!\n"; // That worked!

    // wait 
    std::this_thread::sleep_for(std::chrono::seconds(10));
}