linux c语言进程间通信-共享内存

以下为两个进程，write进程向共享内存写数据，reader进程向共享内存读取数据，代码如下：

#include <>
#include <>
#include <>
#include <>
#include <>
#include <>
#include <sys/>
#include <sys/>
#include <sys/>

#define N 64

typedef struct 
{
	pid_t pid;
	char buf[N];
}SHM;

void handler(int signo)
{
	//printf("get signal\n");
	return;
}

void keycontrol(int signo)
{
	printf("keycontrol is : %d\n",signo);
	if(signo == SIGINT)
	{
		return;
	}
}

int main()
{
	key_t key;
	int shmid;
	SHM *p;
	pid_t pid;

	//建立IPC通讯,获取key值
	if((key = ftok(".",'m')) < 0)
	{
		perror("fail to ftok");
		exit(-1);
	}



	signal(SIGUSR1,handler);
	signal(SIGINT,keycontrol); 
	// 获取共享内存
	if((shmid = shmget(key,sizeof(SHM),0666|IPC_CREAT|IPC_EXCL)) < 0)
	{
		if(EEXIST == errno)
		{
			shmid = shmget(key,sizeof(SHM),0666);
			p = (SHM *)shmat(shmid,NULL,0);
			pid = p->pid;
			p->pid = getpid();
			kill(pid,SIGUSR1);
		}
		else
		{
			perror("fail to shmget");
			exit(-1);
		}
	}
	else
	{
		// 连接共享内存
		p = (SHM*)shmat(shmid,NULL,0);
		p->pid = getpid();
		pause();
		pid=p->pid;
	}

	printf("shmid = %d\n",shmid);
	while(1)
	{
		printf("write to shm:");
		fgets(p->buf,N,stdin);
		kill(pid,SIGUSR1);
		if(strcmp(p->buf,"quit\n")==0)
			break;
		pause();
	}
	// 断开连接
	shmdt(p);
	shmctl(shmid,IPC_RMID,NULL);

	return 0;
}

#include <>
#include <>
#include <>
#include <>
#include <>
#include <>
#include <sys/>
#include <sys/>
#include <sys/>


#define N 64

typedef struct 
{
	pid_t pid;
	char buf[N];
}SHM;

void handler(int signo)
{
	//printf("get signal\n");
	return;
}

int main()
{
	key_t key;
	int shmid;
	SHM *p;
	pid_t pid;

	// 获取key值
	if((key = ftok(".",'m')) < 0)
	{
		perror("fail to ftok");
		exit(-1);
	}

	signal(SIGUSR1,handler);
	// 获取共享内存
	if((shmid = shmget(key,sizeof(SHM),0666|IPC_CREAT|IPC_EXCL))<0)
	{
		if(EEXIST == errno)
		{
			shmid = shmget(key,sizeof(SHM),0666);
			p = (SHM *)shmat(shmid,NULL,0);
			pid = p->pid;
			p->pid = getpid();
			kill(pid,SIGUSR1);
		}
		else
		{
			perror("fail to shmget");
			exit(-1);
		}
	}		
	else
	{
		// 连接共享内存
		p = (SHM *)shmat(shmid,NULL,0);
		p->pid = getpid();
		pause();
		pid = p->pid;
	}

	while(1)
	{
		pause();
		if (strcmp(p->buf,"quit\n") == 0)
			exit(0);
		printf("read from shm:%s",p->buf);
		kill(pid,SIGUSR1);
	}

	return 0;
}