struct msgbuf {
    long mtype;       /* message type, must be > 0 */
    char mtext[1];    /* message data */
};
//我们必须按照这个形式设置msgbuff

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/ipc.h>
#include <sys/msg.h>
#include <string.h>
#include <sys/wait.h>
#define ERR_EXIT(m) \
    do { perror(m); exit(EXIT_FAILURE); } while (0);
#define TEXTSIZE 1024
//消息结构体
typedef struct msgbuff {
  long int type;
  char  text[TEXTSIZE];
} msgbuff;
int main(int argc, char* argv[]) {
  if (2 != argc) {
    fprintf(stderr, "usage: %s <filepath>", argv[0]);
    exit(EXIT_FAILURE);
  }
  key_t key = ftok(argv[1], 'q');
  pid_t pid = fork();
  int msgid;
  if (pid == -1) {
    ERR_EXIT("fork");
  }
  if (pid == 0) {
    //son process
    //获取消息队列
    msgid = msgget(key, 0666 | IPC_CREAT);
    msgbuff msg;
    //然后接收类型为1的消息并且打印
    int read_size = msgrcv(msgid, &msg, TEXTSIZE, 1, 0);
    if (-1 == read_size) {
      ERR_EXIT("msgrcv");
    }
    printf("type: %d, text: %s\n", msg.type, msg.text);
    memset(&msg, 0, sizeof(msg));
    //再接收一下类型为2的消息并且打印
    read_size = msgrcv(msgid, &msg, TEXTSIZE, 2, 0);
    if (-1 == read_size) {
      ERR_EXIT("msgrcv");
    }
    printf("type: %d, text: %s\n", msg.type, msg.text);
  } else {
    //fa process
    //创建消息队列
    msgid = msgget(key, 0666 | IPC_CREAT);
    //创建消息结构体
    msgbuff msg1, msg2;
    memset(&msg1, 0, sizeof(msg1));
    memset(&msg1, 0, sizeof(msg2));
    msg1.type = 1;
    memcpy(msg1.text, "hello msg queue I am type1", strlen("hello msg queue I am type1"));
    msgsnd(msgid, &msg1, TEXTSIZE, 0);
    msg2.type = 2;
    memcpy(msg2.text, "hello msg queue, I am type2", strlen("hello msg queue, I am type2"));
    msgsnd(msgid, &msg2, TEXTSIZE, 0);
    waitpid(pid, NULL, 0);
      if (-1 == msgctl(msgid, IPC_RMID, NULL)) {
          ERR_EXIT("msgctl");
          exit(1);
      }
  }
  return 0;
}

struct sembuf
{
  unsigned short int sem_num;/* semaphore number */
  short int sem_op; /* semaphore operation */
  short int sem_flg;/* operation flag */
};

 union semun {
     int              val;    /* Value for SETVAL */
     struct semid_ds *buf;    /* Buffer for IPC_STAT, IPC_SET */
     unsigned short  *array;  /* Array for GETALL, SETALL */
     struct seminfo  *__buf;  /* Buffer for IPC_INFO
                             (Linux-specific) */
 };

#include <sys/types.h>
#include <unistd.h>
#include <sys/ipc.h>
#include <sys/sem.h>
#include <stdlib.h>
#include <errno.h>
#include <stdio.h>
#include <sys/wait.h>
#define ERR_EXIT(m) \
    do { perror(m); exit(EXIT_FAILURE); } while (0);
//联合结构体
union semun {
    int              val;    /* Value for SETVAL */
    struct semid_ds *buf;    /* Buffer for IPC_STAT, IPC_SET */
    unsigned short  *array;  /* Array for GETALL, SETALL */
    struct seminfo  *__buf;  /* Buffer for IPC_INFO*/
};
int initsem(key_t key) {
    int semid = -1;
    //创建一个信号量集合IPC, 其中包含一个信号量
    if (-1 == (semid = semget(key, 1, 0666 | IPC_CREAT))) {
        ERR_EXIT("semget");
    }
    //设置信号量val
    union semun sem_un;
    sem_un.val = 1;
    if (-1 == semctl(semid, 0, SETVAL, sem_un)) {
        ERR_EXIT("semctl");
    }
    return semid;
}
//销毁
void destorysem(int semid) {
    if (-1 == semctl(semid, 0, IPC_RMID)) {
        ERR_EXIT("semctl destorysem");
    }
}
void P(int semid) {
    //因为信号量集合中就只是一个
    //所以sembuf无需设置为vector
    struct sembuf op;//操作
    op.sem_num = 0;
    op.sem_op = -1;// - 1
    op.sem_flg = SEM_UNDO;
    if (-1 == semop(semid, &op, 1)) {
        ERR_EXIT("semop P");
    }
}
void V(int semid) {
    struct sembuf op;//操作
    op.sem_num = 0;
    op.sem_op = 1;// + 1
    op.sem_flg = SEM_UNDO;
    if (-1 == semop(semid, &op, 1)) {
        ERR_EXIT("semop V");
    }
}
int main(int argc, char* argv[]) {
    if (2 != argc) {
        fprintf(stderr, "usage: %s <filepath>", argv[0]);
        exit(EXIT_FAILURE);
    }
    //1.获取唯一标识key
    key_t key = ftok(argv[1], 'a');
    //2. 创建信号量集合
    int semid = initsem(key);
    int cnt = 10;
    pid_t pid = fork();
    if (pid == -1) {
        ERR_EXIT("fork");
    }
    if (pid == 0) {
        //son process
      while (cnt > 0) {
         // P(semid);
          printf("I am son process\n");
          sleep(1);
          //V(semid);
          cnt -= 1; 
      }
    } else {
      //fa process
      while (cnt > 0) { 
        //P(semid);
        printf("I am fa process\n");
        sleep(1);
        //V(semid);
        cnt -= 1;
      }
      waitpid(pid, NULL, 0);
      destorysem(semid);
    }
    return 0;
}