如何用命名管道(FIFO)实现非阻塞模式进程间通讯(IPC)？

进程AAA非阻塞模式创建一个管道，用来写数据。

char write_fifo_name[] = "write-fifo.txt";

int ret = mkfifo(write_fifo_name, S_IRUSR | S_IWUSR);

write_fd = open(write_fifo_name, O_NONBLOCK); /*非阻塞模式*/





进程BBB阻塞模式打开这个管道时，

死在open函数那里，不向下走了。。。

char read_fifo_name[] = "write-fifo.txt";

printf("111111!\n");

while ((read_fd = open(read_fifo_name, O_RDONLY)) == -1) 

{

  printf("2222!\n"); /*该行不输出*/

  sleep(1); 

}

printf("3333!\n");  /*该行不输出*/

下面代码用阻塞模式实现进程间通讯，Lucy和Kate用阻塞模式进行聊天通讯。



/*Lucy.c*/

#include <sys/types.h>

#include <sys/stat.h>

#include <string.h>

#include <stdio.h>

#include <errno.h>

#include <fcntl.h>



/*全局变量*/

char write_fifo_name[] = "read-fifo.txt";

char read_fifo_name[] = "write-fifo.txt";

int write_fd, read_fd;



/*初始化*/

int kateInitNamedPipe()

{

	/*创建管道文件*/ 

	int ret = mkfifo(write_fifo_name, S_IRUSR | S_IWUSR);

	if ( (ret == -1) &&(errno!=EEXIST)) {

		printf("Fail to create FIFO %s: %s", write_fifo_name, strerror(errno));

		return -1;

	}

	

	/*读管道文件的ID*/   

	while ((read_fd = open(read_fifo_name, O_RDONLY)) == -1) 

	//while ((read_fd = open(read_fifo_name, O_NONBLOCK)) == -1) 

	{

		sleep(1);

	}

	

	/*读管道文件的ID*/  

	write_fd = open(write_fifo_name, O_WRONLY);

	//write_fd = open(write_fifo_name, O_NONBLOCK); 

	if (write_fd == -1) {

        printf("Fail to open FIFO %s: %s", write_fifo_name, strerror(errno));

        return -1;

	}

    return 1;

}



/*写管道文件*/

int kateWriteNamedPipe(int w_fd, char *mscIDState)

{

	int wLen = write(w_fd, mscIDState, strlen(mscIDState)); 

	return wLen;

}



/*读管道文件*/

int kateReadNamedPipe(int r_fd,char *pCalledNo)

{

	int len = read(r_fd, pCalledNo, 256); 

	return len;

}



int main(void)

{ 

	kateInitNamedPipe(); 

	char buf[256]; /*每次读写的数据大小*/

	int len;       /*读到的数据大小*/	

	char pMsgToLucy[] ="Hi,Lucy !";

	

	while (1) {  

		printf("kate ready to read namedPipe\n");    

		memset(buf,0,sizeof(buf));  		                

		len = kateReadNamedPipe(read_fd,buf);  		

		

                /*业务处理*/

		if ( len > 0) {

			buf[len] = '\0';

			printf("Data From Lucy: %s **** Length:%d\n", buf,strlen(buf));

 		}

		else if (len == 0)  /*管道为空*/

		{   

			printf("Data From Lucy:NULL **** Length:0\n");

		}

		else if (len == -1) /*读管道出现异常*/

		{   

			printf("Data From Lucy: Error **** Length:-1\n");

		}       

        printf("kate read namedPipe over\n"); 

                  

		printf("kate ready to write namedPipe\n"); 

		printf("     Data To Lucy:%s **** Length:%d\n",pMsgToLucy,strlen(pMsgToLucy));          

		strcpy(buf,pMsgToLucy);                     		

		kateWriteNamedPipe(write_fd, buf);    

		printf("kate write namedPipe over\n");

	}	



	close(write_fd);

	unlink(write_fifo_name); 

	close(read_fd); 

}



/*Kate.c*/

#include <sys/types.h>

#include <sys/stat.h>

#include <string.h>

#include <stdio.h>

#include <errno.h>

#include <fcntl.h>

#include <unistd.h>



/*全局变量*/

char write_fifo_name[] = "write-fifo.txt";

char read_fifo_name[] = "read-fifo.txt";

int write_fd, read_fd;  /*管道文件的句柄*/

struct stat stat_buf;   /*结构体对象，暂时未用到*/ 



/*初始化*/

int lucyInitNamedPipe()

{

	/*创建命名管道*/   

	int ret = mkfifo(write_fifo_name, S_IRUSR | S_IWUSR);

	if ( (ret == -1) &&(errno!=EEXIST)) {

		printf("Fail to create FIFO!!! %s: %s", write_fifo_name, strerror(errno));

		return -1;

	}

	

	/*写管道的ID*/  

	write_fd = open(write_fifo_name, O_WRONLY);     /*阻塞模式*/

	//write_fd = open(write_fifo_name, O_NONBLOCK); /*非阻塞模式*/

	if (write_fd == -1) {

		printf("Fail to open FIFO %s: %s", write_fifo_name, strerror(errno));

		return 0;

	}

	

	/*读管道的ID*/

	while ((read_fd = open(read_fifo_name, O_RDONLY)) == -1)     /*阻塞模式*/

	//while ((read_fd = open(read_fifo_name, O_NONBLOCK)) == -1) /*非阻塞模式*/

	{

		sleep(1); /*sleep休眠1秒钟*/

	}

	return 1;

}



/*写管道文件*/

int lucyWriteNamedPipe(int w_fd, char *pCalledNo)

{

	int wLen = write(w_fd, pCalledNo, strlen(pCalledNo)); 

	return wLen;

}



/*读管道文件*/

int lucyReadNamedPipe(int r_fd,char *mscIDState)

{

	int len = read(r_fd, mscIDState, 256); 

	return len;

}



int main(void)

{    

	lucyInitNamedPipe();             /*管道文件初始化*/	

	char buf[256];                   /*每次读写的数据大小*/         

	int len;                         /*读取的数据长度*/

	char pSendMessage[] ="Hi,Kate";   

	

	/*循环读写管道文件*/

	while (1) {     

		printf("lucy Ready to write namedPipe\n");         

		printf("    Data To Kate ：%s Length:%d\n",pSendMessage,strlen(pSendMessage));

		memset(buf,0,sizeof(buf));  

		strcpy(buf,pSendMessage);             /*准备写入管道的数据*/                         

		lucyWriteNamedPipe(write_fd, buf);    /*向管道中写数据*/

		printf("lucy write namedPipe over\n");  

                

		printf("lucy Ready to read namedPipe\n"); 

		memset(buf,0,sizeof(buf));                                  

		len = lucyReadNamedPipe(read_fd,buf); /*从管道中读文件*/                   

		

		/*业务处理*/

		if (len > 0) 

		{

			buf[len] = '\0';

			printf("Data From Kate : %s **** Length:%d\n", buf,len);	

		}

		else if (0 == len) /*管道为空，没有数据可读*/ 

		{   

			printf("Data From Kate:NULL **** Length:0\n"); 

		}

		else if (len == -1) /*读管道出现异常*/

		{   

			printf("Data From Kate: Error **** Length:-1\n"); 

		}		

		printf("lucy read namedPipe over\n");

	}	



	close(write_fd);

	unlink(write_fifo_name); 

	close(read_fd);  

}