UNIX IPC之共享内存(shared memory)实例

服务器端:

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

#define SHM_SIZE 26

int main(int argc,char* argv[])
{
	key_t key = ftok("/home/kingoal/",2);
	
	int shmid = shmget(key,SHM_SIZE,IPC_CREAT|0600);
	if(shmid == -1)
	{
		perror("shmget");
		exit(-1);
	}

	char* pMem = (char*)shmat(shmid,NULL,0);
	if(pMem == (char*) -1)
	{
		perror("shmat");
		exit(-1);
	}

	printf("Shared Memory: %p\n", pMem);

	for(int i = 0;i<SHM_SIZE;i++)
	{
		pMem[i]='a'+i;
	}

	while(pMem[0]!='*')
		sleep(1);

	int retcode = shmdt(pMem);
	if(retcode == -1)
	{
		perror("shmdt");
		exit(-1);
	}

	retcode = shmctl(shmid,IPC_RMID,NULL);
	if(retcode == -1)
	{
		perror("shmctl");
		exit(-1);
	}

	return 0;
}

 客户端：

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

#define SHM_SIZE 26

int main(int argc,char* argv[])
{
	key_t key = ftok("/home/kingoal/",2);

	int shmid = shmget(key,SHM_SIZE,0600);
	if(shmid == -1)
	{
		perror("shmget");
		exit(-1);
	}

	char* pMem = (char* )shmat(shmid,NULL,0);
	if(pMem == (char*) -1)
	{
		perror("shmat");
		exit(-1);
	}
	printf("Client: Shared Memory at %p\n", pMem);

	for(int i=0;i<SHM_SIZE;i++)
	{
		putchar(pMem[i]);
	}

	putchar('\n');

	pMem[0]='*';

	shmdt(pMem);

	return 0;
}

 执行结果：

 

首先是服务器端的执行结果

[[email protected] ~/dev/cxx]$ ./shmserv 
Shared Memory: 0x28294000
[[email protected] ~/dev/cxx]$ 

 下面是客户端的执行结果

[[email protected] ~/dev/cxx]$ ipcs
Message Queues:
T           ID          KEY MODE        OWNER    GROUP   

Shared Memory:
T           ID          KEY MODE        OWNER    GROUP   
m       327680     39531450 --rw------- kingoal  kingoal 

Semaphores:
T           ID          KEY MODE        OWNER    GROUP   

[[email protected] ~/dev/cxx]$ shmclient 
Client: Shared Memory at 0x28294000
abcdefghijklmnopqrstuvwxyz
[[email protected] ~/dev/cxx]$ ipcs
Message Queues:
T           ID          KEY MODE        OWNER    GROUP   

Shared Memory:
T           ID          KEY MODE        OWNER    GROUP   

Semaphores:
T           ID          KEY MODE        OWNER    GROUP   

[[email protected] ~/dev/cxx]$