进程通信之共享内存

#include <sys/ipc.h>
#include <sys/shm.h>
#include <stdio.h>
#include <string.h>

#define MAX_SZIE 1024


struct share_block
{
int flag;
char buffer[MAX_SZIE];
};

int main()
{
int shmid;
struct share_block *pshare;
char buffer[MAX_SZIE] = {0};
int running = 1;
int ret;


// 创建共享内存或者获取共享内存 返回共享内存标识符
shmid = shmget((key_t)1234, sizeof(struct share_block), 0666 | IPC_CREAT);
if (-1 == shmid)
{
perror("shmget");
return -1;
}


// 将共享内存映射到本地空间
pshare = shmat(shmid, NULL, 0);
if ((void *) -1 == pshare)
{
perror("shmat");
return -1;
}


// 从共享内存里读入数据
while (running)
{
//printf ("pshare->flag = %d\n", pshare->flag);
if (1 == pshare->flag)
{
// 从共享内存里读入数据
strncpy(buffer, pshare->buffer, MAX_SZIE);
if (strncmp("end", buffer, 3) == 0)
{
running = 0;
}
printf("Read from shared memory: %s\n", buffer);

// 往共享内存里写入数据
printf("please say something:\n");
fgets(buffer, MAX_SZIE, stdin);
strncpy(pshare->buffer, buffer, MAX_SZIE);
pshare->flag = 0;
}
}


// 解除映射
ret = shmdt(pshare);
if (-1 == ret)
{
perror("shmdt");
return -1;
}


return 0;
}