//https://zhuanlan.zhihu.com/p/147826545
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/ipc.h>
#include <sys/shm.h>
 
#define BUFSZ 512
 
int main(int argc, char *argv[])
{
	int shmid;
	int ret;
	key_t key;
	char *shmadd;
	
	//创建key值
	key = ftok("../", 2015); 
	if(key == -1)
	{
		perror("ftok");
	}
	
	system("ipcs -m"); //查看共享内存
	
	//打开共享内存
	shmid = shmget(key, BUFSZ, IPC_CREAT|0666);
	if(shmid < 0) 
	{ 
		perror("shmget"); 
		exit(-1); 
	} 
	
	//映射
	shmadd = shmat(shmid, NULL, 0);
	if(shmadd < 0)
	{
		perror("shmat");
		exit(-1);
	}
	
	//读共享内存区数据
	printf("data = [%s]\n", shmadd);
	
	//分离共享内存和当前进程
	ret = shmdt(shmadd);
	if(ret < 0)
	{
		perror("shmdt");
		exit(1);
	}
	else
	{
		printf("deleted shared-memory\n");
	}
	
	//删除共享内存
	shmctl(shmid, IPC_RMID, NULL);
	
	system("ipcs -m"); //查看共享内存
	
	return 0;
}