Unix-進程間通信

1、有名管道間通信

read進程代碼：

#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 代碼：

#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、信號量通信

#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

運行該文件，在另一個終端中執行

kill -s SIGQUIT 'pid'

這裏的pid爲mysignal的進程號

通過kill向進程mysignal發送信號。mysignal得到信號後，打印相應的信息。

3、共享內存通信：

共享內存是被多個進程共享的一部分物理內存。共享內存是進程間共享數據的一種最快的方法，一個進程向共享內存區域寫入了數據，共享這個區域的所有進程就可以立刻看到其中的內容

#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);

	}
	//創建共享內存對象
	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
	{       //把共享內存區對象映射到調用進程的地址空間
		p_addr = shmat(shmid,0,0);
		memset(p_addr,'\0',1024);
		strncpy(p_addr,argv[1],1024);
		wait(NULL);
		shmdt(p_addr);//斷開共享內存連接
		shmctl(shmid,IPC_RMID,NULL);//IPC_RMID：刪除這片共享內存
		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);//斷開共享內存連接
		exit(0);
	}
}

4、消息隊列

#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');//創建key
        printf("key= [%x]\n",key);
        msgid = msgget(key,IPC_CREAT|0666);//創建一個新隊列或打開一個存在的隊列

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

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

        memset(&msgbuf,0,sizeof(msgbuf));
        ret=msgrcv(msgid,&msgbuf,sizeof(msgbuf.data),10,IPC_NOWAIT);//從消息隊列中接收數據

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

        return 0;
}

5、信號量