linux c/c++ 检测程序是否在运行

bool checkOnly()
{
    const char filename[]  = "./lockfile";
    int fd = open (filename, O_WRONLY | O_CREAT , 0644);
    int flock = lockf(fd, F_TLOCK, 0 );
    if (fd == -1) {
        return false;
    }
    //给文件加锁
    if (flock == -1) {
        return false;
    }
    //程序退出后，文件自动解锁
    return true;
}