shm_c.cpp

在Linux测试共享共享内存消息

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <time.h>
#include <sys/shm.h>
#include <sys/sem.h>
#include <sys/ipc.h>

#define SEGSIZE 1024
#define READTIME 1

union semun {
	int val;
	struct semid_ds *buf;
	unsigned short *array;
} arg;

// 打印程序执行时间
void out_time(void)
{
	static long start = 0;
	time_t tm;
	if (0 == start){
		tm = time(NULL);
		start = (long)tm;
		printf(" now start ...\n");
	}
	printf(" second: %ld \n",(long)(time(NULL)) - start);
}

//创建信号量
int new_sem(key_t key)
{
	union semun sem;
	int semid;
	sem.val = 0;
	semid = semget(key,0,0);
	if (-1 ==  semid){
		printf("create semaphore error\n");
		exit(-1);
	}
	return semid;
}

//等待信号量变成0
void wait_v(int semid)
{
	int ret;

	struct sembuf sops={0,0,0};
	printf("shm_c-wait_v():before semop(),time=%ld ...\n",time(NULL));
	ret=semop(semid,&sops,1);
	printf("shm_c-wait_v():after semop(),ret=%d,time=%ld ...\n",ret,time(NULL));
}

int main(void)
{
	key_t key;
	int shmid,semid;
	char *shm;
	char msg[100];
	char i;

	printf("======= Run Client Program ===========\n");
	key = ftok("./",0);
	shmid = shmget(key,SEGSIZE,0);
 
	if(-1 == shmid){
		printf(" create shared memory error\n");
		return -1;
	}

	shm = (char *)shmat(shmid,0,0);
	if (-1 == (int)shm){
		printf(" attach shared memory error\n");
		return -1;
	}

	semid = new_sem(key);
	for (i = 0;i < 3;i ++){
		sleep(2);
		wait_v(semid);
		printf("Message geted is: %s \n",shm + 1);
		out_time();
	}
	shmdt(shm);
	return 0;
}
//编译服务端程序：
	//gcc -o shm_c shm_c.c -g