shm1.c

国嵌所有的实验代码

#include <unistd.h>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <sys/types.h>
#include <sys/ipc.h>
#include <sys/shm.h>
#include "shm_com.h"

int main(void)
{
    int running=1;
	void *shared_memory=(void *)0;
	struct shared_use_st *shared_stuff;
	int shmid;


	/*创建共享内存*/
	shmid=shmget((key_t)1234,sizeof(struct shared_use_st),0666|IPC_CREAT);
	if(shmid==-1)
	{
	    fprintf(stderr,"shmget failed\n");
		exit(EXIT_FAILURE);
	}

	/*映射共享内存*/
	shared_memory=shmat(shmid,(void *)0,0);
	if(shared_memory==(void *)-1)
	{
	    fprintf(stderr,"shmat failed\n");
		exit(EXIT_FAILURE);
	}
	printf("Memory attached at %X\n",(int)shared_memory);

	/*让结构体指针指向这块共享内存*/
	shared_stuff=(struct shared_use_st *)shared_memory;

	/*控制读写顺序*/
	shared_stuff->written_by_you=0;

	/*循环的从共享内存中读数据，直到读到“end”为止*/
	while(running)
	{
	   if(shared_stuff->written_by_you)
	   {
	       printf("You wrote:%s",shared_stuff->some_text);
		   sleep(1);  //读进程睡一秒，同时会导致写进程睡一秒，这样做到读了之后再写
		   shared_stuff->written_by_you=0;
		   if(strncmp(shared_stuff->some_text,"end",3)==0)
		   {
		       running=0; //结束循环
		   }
	   }
	}

	/*删除共享内存*/
	if(shmdt(shared_memory)==-1)
	{
	    fprintf(stderr,"shmdt failed\n");
	    exit(EXIT_FAILURE);
	}
       exit(EXIT_SUCCESS);
}