Unix-进程间通信

1、有名管道间通信

read进程代码：

#include<sys/types.h>
#include<sys/stat.h>
#include<errno.h>
#include<fcntl.h>
#include<stdio.h>
#include<stdlib.h>
#include<string.h>
#define FIFO "/tmp/myfifo"

int main(int argc , char** argv)
{
	char buf_r[100];
	int fd;
	int nread;
	if((mkfifo(FIFO,O_CREAT | O_EXCL)<0)&& (errno!=EEXIST))
		printf("cannot create fifo\n");
	printf("prapare for reading bytes \n");
	memset(buf_r,0,sizeof(buf_r));
	fd = open(FIFO,O_RDONLY | O_NONBLOCK,0);
	if(fd == -1)
	{
		perror("open");
		exit(1);
	}
	while(1)
	{
		memset(buf_r,0,sizeof(buf_r));
		if((nread = read(fd,buf_r,100)==-1))
		{
			if(errno== EAGAIN)
				printf("no data \n");
		}
		else
		printf("read from FIFO %s \n",buf_r);
		sleep(1);
	}
	pause();
}

write 代码：

#include<sys/types.h>
#include<sys/stat.h>
#include<errno.h>
#include<fcntl.h>
#include<stdio.h>
#include<stdlib.h>
#include<string.h>
#define FIFO_SERVER "/tmp/myfifo"

int main(int argc ,char** argv)
{
	int fd;
	char w_buf[100];
	int nwrite;
	fd = open(FIFO_SERVER,O_WRONLY | O_NONBLOCK,0);

	if(argc == 1)
	{
		exit(-1);
	}
	strcpy(w_buf,argv[1]);

	if((nwrite = write(fd,w_buf,100))==-1)
	{
		if(errno == EAGAIN)
			printf("the fifo is not read\n");
	}
	else
		printf("write %s to the fifo\n",w_buf);
	return 0;
}

2、信号量通信

#include<signal.h>
#include<stdio.h>
#include<stdlib.h>

void my_func(int sign_no)
{
	if(sign_no == SIGINT)
		printf("I have get SIGINT\n");
	else if(sign_no == SIGQUIT)
		printf("I have get SIGQUIT\n");

}

void main()
{
	printf("Waiting for signal SIGINT or SIGQUIT\n");
	signal(SIGINT,my_func);
	signal(SIGQUIT,my_func);
	pause();
	exit(0);
}

mysignal.c

运行该文件，在另一个终端中执行

kill -s SIGQUIT 'pid'

这里的pid为mysignal的进程号

通过kill向进程mysignal发送信号。mysignal得到信号后，打印相应的信息。

3、共享内存通信：

共享内存是被多个进程共享的一部分物理内存。共享内存是进程间共享数据的一种最快的方法，一个进程向共享内存区域写入了数据，共享这个区域的所有进程就可以立刻看到其中的内容

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

int main(int argc , char**argv)
{
	int shmid;
	char *p_addr,*c_addr;

	if(argc != 2)
	{
		fprintf(stderr,"Usage:%s \n \a",argv[0]);
		exit(1);

	}
	//创建共享内存对象
	if((shmid = shmget(IPC_PRIVATE,1024,IPC_CREAT)) == -1)
	{
		fprintf("create Share Memory Error: %s\n",strerror(errno));
		exit(1);

	}
	//create Process
	if(0 !=fork())	//father Process
	{       //把共享内存区对象映射到调用进程的地址空间
		p_addr = shmat(shmid,0,0);
		memset(p_addr,'\0',1024);
		strncpy(p_addr,argv[1],1024);
		wait(NULL);
		shmdt(p_addr);//断开共享内存连接
		shmctl(shmid,IPC_RMID,NULL);//IPC_RMID：删除这片共享内存
		exit(0);
	}
	else //child Process
	{
	<span style="white-space:pre">	</span>sleep(1);
		c_addr = shmat(shmid,0,0);
		printf("Client get %s\n",c_addr);
<span style="white-space:pre">		</span>shmdt(c_addr);//断开共享内存连接
		exit(0);
	}
}

4、消息队列

#include <sys/types.h>
#include <sys/msg.h>
#include <unistd.h>
#include <string.h>
#include <stdio.h>

struct msg_buf
{
        int mtype;
        char data[255];
};

int main()
{
        key_t key;
        int msgid;
        int ret;
        struct msg_buf msgbuf;

        key = ftok("/tmp/1",'a');//创建key
        printf("key= [%x]\n",key);
        msgid = msgget(key,IPC_CREAT|0666);//创建一个新队列或打开一个存在的队列

        if(msgid==-1)
        {
                printf("create error \n");
        }

        msgbuf.mtype = 10;
        strcpy(msgbuf.data,"test haha");
        ret=msgsnd(msgid,&msgbuf,sizeof(msgbuf.data),IPC_NOWAIT);//数据放到消息队列中
        if(ret==-1)
        {
                printf("send error\n");
                return -1;
        }

        memset(&msgbuf,0,sizeof(msgbuf));
        ret=msgrcv(msgid,&msgbuf,sizeof(msgbuf.data),10,IPC_NOWAIT);//从消息队列中接收数据

        if(ret==-1)
        {
                printf("receive error \n");
                return -1;
        }
        printf("receive : %s\n",msgbuf.data);

        return 0;
}

5、信号量