函数sem_open创建一个新的有名信号灯或打开一个已存在的有名信号灯。有名信号灯总是既可用于线程间的同步，又可以用于进程间的同步。-Function to create a new sem_open famous lights or open an existing well-known lights. Signal is always well-known both for inter-thread synchronization,

Use a semaphore to implement mutual exclusion.

使用sem_init对共享内存的操作，使得比sem_open更加方便-Use sem_init operations on shared memory, making it more convenient than sem_open