用消息队列实现AB进程随时通信，在共享内存中循环逆置打印字符串

一、要求实现AB进程随时对话

1. A进程发送一句话给B进程，B进程接收后打印
2. B进程回复一句话给A进程，A进程接收后打印

随机重复1，2步骤，当收到quit后，要结束AB进程

A进程：

#include <stdio.h>
#include <sys/types.h>
#include <sys/ipc.h>
#include <sys/msg.h>
#include <unistd.h>
#include <string.h>
#include <signal.h>
struct msgbuf
{
	long mtype;
	char mtext[128];
};
int main(int argc, const char *argv[])
{

	key_t key = ftok("./",1);
	if(ftok < 0)
	{
		perror("ftok");
		return -1;
	}
	int msqid = msgget(key,IPC_CREAT|0664);
	if(msqid < 0)
	{
		perror("msgget");
		return -1;
	}
	struct msgbuf sndbuf;
	pid_t cpid = fork();
	if(cpid > 0)
	{
		while(1)
		{
			sndbuf.mtype = 1;
			scanf("%s",sndbuf.mtext);
			msgsnd(msqid,&sndbuf,sizeof(sndbuf.mtype),0);
			if(strcmp(sndbuf.mtext,"quit") == 0)
				break;
		}
	}
	else if(0 == cpid)
	{
		while(1)
		{
			msgrcv(msqid,&sndbuf,sizeof(sndbuf.mtext),2,0);
			if(strcmp(sndbuf.mtext,"quit") == 0)
				break;
			printf("%s\n",sndbuf.mtext);
		}
		kill(getppid(),2);
	}
	else
	{
		perror("fork");
		return -1;
	}
	
	return 0;
}

B进程 

#include <stdio.h>
#include <sys/types.h>
#include <sys/ipc.h>
#include <sys/msg.h>
#include <unistd.h>
#include <string.h>
#include <signal.h>
struct msgbuf
{
	long mtype;
	char mtext[128];
};
int main(int argc, const char *argv[])
{
	key_t key = ftok("./",1);
	if(ftok < 0)
	{
		perror("ftok");
		return -1;
	}
	int msqid = msgget(key,IPC_CREAT|0664);
	if(msqid < 0)
	{
		perror("msgget");
		return -1;
	}
	struct msgbuf sndbuf;
	pid_t cpid = fork();
	if(cpid > 0)
	{
		while(1)
		{
			sndbuf.mtype = 2;
			scanf("%s",sndbuf.mtext);
			msgsnd(msqid,&sndbuf,sizeof(sndbuf.mtype),0);
			if(strcmp(sndbuf.mtext,"quit") == 0)
				break;
		}
	}
	else if(0 == cpid)
	{
		while(1)
		{
			msgrcv(msqid,&sndbuf,sizeof(sndbuf.mtext),1,0);
			if(strcmp(sndbuf.mtext,"quit") == 0)
				break;
			printf("%s\n",sndbuf.mtext);
		}
		kill(getppid(),2);
	}
	else
	{
		perror("fork");
		return -1;
	}
	
	return 0;
}

 二、要求在共享内存中存入字符串"1234567"，A进程循环打印，B进程循环逆置，要求不出现乱序

#include <stdio.h>
#include <sys/ipc.h>
#include <sys/shm.h>
#include <string.h>
#include <unistd.h>
#include <sys/types.h>
int main(int argc, const char *argv[])
{
	key_t key = ftok("./",10);
	if(key < 0)
	{
		perror("ftok");
		return -1;
	}
	int shmid = shmget(key,16,IPC_CREAT|0664);
	if(shmid < 0)
	{
		perror("shmget");
		return -1;
	}
	void *addr = shmat(shmid,NULL,0);
	if((void *)-1 == addr)
	{
		perror("shmat");
		return -1;
	}
	*(int *)addr = 0;
	char *ptr = (char *)addr+4;
	strcpy(ptr,"1234567");
	pid_t cpid = fork();
	if(cpid > 0)
	{
		while(1)
		{
			if(*(int *)addr == 0)
			{
				printf("%s\n",(char *)addr+4);
				*(int *)addr = 1;
			}
		}
	}
	else if(0 == cpid)
	{
		while(1)
		{
			if(*(int *)addr == 1)
			{
				char *star = (char *)addr+4;
				char *end  = (char*)addr+4+strlen(ptr)-1;
				while(star<end)
				{
					char temp = *star;
					*star = *end;
					*end  = temp;
					star++;
					end--;
				}
				*(int *)addr = 0;
			}
		}
	}
	else
	{
		perror("fork");
		return -1;
	}
	return 0;
}