Linux下使用信号量来进行进程间通信

贴一篇代码，我们操作系统老师布置的作业，由单信号量，改为一个信号集中多信号量。水平有限，写的不好。

#include <stdio.h>#include <stdlib.h>#include <unistd.h>#include <sys/types.h>#include <sys/ipc.h>#include <sys/sem.h>#include<sys/mman.h>   //提供了共享内存的相关操作 #include<fcntl.h>#include<sys/stat.h>union semun { int val; struct semid_ds *buf; unsigned short *array;} arg;//生成信号量//信号量创建//第一个:同步信号量,表示先后顺序,必须有空间才能生产//第二个:同步信号量,表示先后顺序,必须有产品才能消费//第三个:互斥信号量,生产者和每个消费者不能同时进入缓冲区int sem_creat(key_t key){  union semun sem[3];  int semid;  sem[0].val = 5;//最多5个产品  sem[1].val=0;  sem[2].val=1;  semid = semget(key, 3, IPC_CREAT|0666);//三个信号量，空、满、进入缓冲区。  if (-1 == semid)  {    printf("create semaphore error\n");    exit(-1);  }  semctl(semid, 0, SETVAL, sem[0]);//初始信号量集中的第一个信号量  semctl(semid,1,SETVAL,sem[1]);//第二个  semctl(semid,2,SETVAL,sem[2]);//第三个  return semid;}//删除信号量void del_sem(int semid){ union semun sem; sem.val = 0; semctl(semid, 0, IPC_RMID, sem); semctl(semid, 1, IPC_RMID, sem); semctl(semid, 2, IPC_RMID, sem);}//p操作int p(int semid,int semIndex){ struct sembuf sops={semIndex, -1, SEM_UNDO};//这里的“semIndex”是信号量集里的信号量序号 return (semop(semid, &sops, 1));}//v操作int v(int semid,int semIndex){ struct sembuf sops={semIndex, +1, SEM_UNDO};//这里的“semIndex”是信号量集里的信号量序号 return (semop(semid, &sops, 1));}int buffer;int Num=5;int *pData;int value_read = 0, value_write = 0;int full, empty,all;int start=0,end=0;void producer(key_t);void consumer(int);int main(void){key_t keyFull, keyEmpty,key;int fd;pid_t pid;  void *ptr;   //指向共享内存的指针    /* shm_open是一个POSIX函数，用来打开或创建一个与“/shm”关联的共享内存区 */if((fd = shm_open("/shm", O_RDWR | O_CREAT, S_IRUSR | S_IWUSR)) == -1)//shmget(...){printf("shm_open error\n"); /* 出错提示 */}if(ftruncate(fd, sizeof(int)*5) == -1) /* 截短共享内存的长度到我们所需要的长度 */{printf("ftruncate error\n");}if((ptr = mmap(0, sizeof(int)*5, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0)) == MAP_FAILED) /* 将共享内存映射到进程地址空间 */{printf("mmap error");}     pData = (int *)ptr;//keyFull = ftok("/", 0);  //keyEmpty = ftok("/", 1);  key=ftok("/", 0);  //full = sem_creat(keyFull, 0);  //empty = sem_creat(keyEmpty, 1);  all=sem_creat(key);switch(pid = fork()){case -1: /* 生成子进程失败 */break;case 0: /* 子进程 *///producer(keyFull, keyEmpty); /* 子进程是生产者 */producer(key);      sleep(2);break;default://consumer(full, empty); /* 父进程是消费者 */consumer(all);break;  }    wait(0);  shm_unlink("/shm"); /* 删除共享内存区，程序中基本上保证了子进程先退出，因此父进程中无wait操作且这部操作放在父进程这里 *///shmctl(shmid,IPC_RMID,&buf); //del_sem(semid);return 0;}/* 生产者写5次后退出 *///void producer(key_t keyFull, key_t keyEmpty)void producer(key_t key){  //full = semget(keyFull, 3, 0);  //empty = semget(keyEmpty, 3, 0);  all=semget(key,3,0);while(value_write < 10) /* 退出条件判定 */{    //printf("Prepare Write\n");printf("准备写\n");    //printf("empty Write P1 : %d\n", semctl(empty, 0, GETVAL, 0));p(all,0); //判断是否有空p(all,2);//操作缓冲区    //printf("empty Write P2 : %d\n", semctl(empty, 0, GETVAL, 0));value_write++; *(pData+start%Num) = value_write;//printf("Write : %5d\n", *(pData+start%Num));printf("写 : %5d\n", *(pData+start%Num)); start++;     //printf("full Write V1 : %d\n", semctl(full, 0, GETVAL, 0));  v(all,2);//释放缓冲区v(all,1); //通知消费者    //printf("full Write V2 : %d\n", semctl(full, 0, GETVAL, 0));    //printf("Write Finish\n");printf("写结束\n");    //sleep(3);}}/* 消费者读5次后退出 *///void consumer(int full, int empty)void consumer(int all){  while(value_read < 10) /* 退出条件判定 */{     //printf("Prepare Read\n");printf("准备读\n");    //printf("full Read P1 : %d\n", semctl(full, 0, GETVAL, 0));p(all,1);//判断是否有产品p(all,2); //操作缓冲区    //printf("full Read P1 : %d\n", semctl(full, 0, GETVAL, 0));//printf("Read : %5d\n", *(pData+end%Num));printf("读 : %5d\n", *(pData+end%Num));    //printf("empty Read V1 : %d\n", semctl(empty, 0, GETVAL, 0));    //printf("empty Read V1 : %d\n", semctl(empty, 0, GETVAL, 0));    //value_read ++;    //printf("Read Finish\n");printf("读结束\n");if(*(pData+end%Num) == 10)exit(0);end++;v(all,2);//释放缓冲区v(all,0);//通知生产者//sleep(1);}}//gcc -lrt p.c (-o 目标文件名)//./a.out