卖票系统

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#include <stdio.h>#include <sys/ipc.h>#include <sys/shm.h>#include <sys/types.h>#include <string.h>#include <time.h>typedef struct _shm{int flag;int ticket;}SHM;void sellTicket(SHM* pshm){while (1){int time = rand() % 10 + 1; usleep(time*100000);if (pshm->flag == 1){pshm->flag = 0;if (pshm->ticket == 0)  // 票卖完{pshm->flag = 1;break;}printf ("卖掉一张票，座位号是 : %d\n", pshm->ticket);pshm->ticket--;pshm->flag = 1;}}}int main(int argc, char **argv){srand ((unsigned int)time(NULL));// 1、创建或者获取一个共享内存int shmid = shmget((key_t)1234, sizeof(SHM), 0666 | IPC_CREAT);if (shmid == -1){perror ("shmget");return -1;}// 2、将共享内存映射到当前的进程空间SHM* pshm = (SHM*)shmat(shmid, NULL, 0);if(pshm == (SHM*)-1){perror ("shmat");return -1;}// 如果命令行参数等于2 负责对共享内存进行初始化if (argc == 2){pshm->flag   = 1;pshm->ticket = 100;}// 开始卖票sellTicket(pshm);// 如果命令行参数等于2 负责对共享内存进行删除if (argc == 2){shmctl(shmid, IPC_RMID, NULL);}return 0;}

同时运行几个程序，便是一个卖票系统。

还有一个运用到了信息量的函数：

semaphore.h

#ifndef __SEMAPHORE_H__#define __SEMAPHORE_H__#include <sys/types.h>#include <sys/ipc.h>#include <sys/sem.h>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) */};// 信号量的初始化函数int sem_init(int sem_id){union semun sem;sem.val = 1;int ret = semctl(sem_id, 0, SETVAL, sem);return ret;}// 信号量的 P 操作int sem_p(int sem_id){struct sembuf sem;sem.sem_num = 0;sem.sem_op  = -1;sem.sem_flg = SEM_UNDO;int ret = semop(sem_id, &sem,1);return ret;}// 信号量的 v 操作int sem_v(int sem_id){struct sembuf sem;sem.sem_num = 0;sem.sem_op  = 1;sem.sem_flg = SEM_UNDO;int ret = semop(sem_id, &sem,1);return ret;}// 销毁信号量int sem_del(int sem_id){int ret = semctl(sem_id, 0, IPC_RMID);return ret;}#endif // __SEMAPHORE_H__

main.c

#include <stdio.h>#include <sys/ipc.h>#include <sys/shm.h>#include <sys/types.h>#include <string.h>#include <time.h>#include "semaphore.h"typedef struct _shm{int flag;int ticket;}SHM;void sellTicket(SHM* pshm, int sem_id){while (1){int time = rand() % 10 + 1; usleep(time*100000);// 信号量的P操作sem_p (sem_id);if (pshm->ticket == 0)  // 票卖完{sem_v (sem_id);break;}printf ("卖掉一张票，座位号是 : %d\n", pshm->ticket);pshm->ticket--;sem_v (sem_id);}}int main(int argc, char **argv){srand ((unsigned int)time(NULL));// 1、创建或者获取一个共享内存int shmid = shmget((key_t)1234, sizeof(SHM), 0666 | IPC_CREAT);if (shmid == -1){perror ("shmget");return -1;}// 创建一个信号量int sem_id = semget((key_t)5678, 1, 0666 | IPC_CREAT);if (sem_id== -1){perror ("semget");return -1;}// 2、将共享内存映射到当前的进程空间SHM* pshm = (SHM*)shmat(shmid, NULL, 0);if(pshm == (SHM*)-1){perror ("shmat");return -1;}// 如果命令行参数等于2 负责对共享内存和信号量进行初始化if (argc == 2){pshm->ticket = 100;sem_init(sem_id);}// 开始卖票sellTicket(pshm, sem_id);// 如果命令行参数等于2 负责对共享内存和信号量进行删除if (argc == 2){shmctl(shmid, IPC_RMID, NULL);sem_del(sem_id);}return 0;}

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