/******************* * fifo_open_test.c* *******************/#include <sys/types.h>#include <sys/stat.h>#include <errno.h>#include <fcntl.h>#define FIFO_SERVER "/tmp/fifoserver"int handle_client(char*);main(int argc,char** argv){	int r_rd;	int w_fd;	pid_t pid;	if((mkfifo(FIFO_SERVER,O_CREAT|O_EXCL)<0)&&(errno!=EEXIST))		printf("cannot create fifoserver\n");	handle_client(FIFO_SERVER);	}int handle_client(char* arg){int ret;ret=w_open(arg);switch(ret){	case 0:	{		printf("open %s error\n",arg);	printf("no process has the fifo open for reading\n");	return -1;	}	case -1:	{		printf("something wrong with open the fifo except for ENXIO");		return -1;	}	case 1:	{		printf("open server ok\n");		return 1;	}	default:	{		printf("w_no_r return ????\n");		return 0;	}}		unlink(FIFO_SERVER);}int w_open(char*arg)//0  open error for no reading//-1 open error for other reasons//1  open ok{	if(open(arg,O_WRONLY|O_NONBLOCK,0)==-1)	{	if(errno==ENXIO)		{			return 0;		}		else		return -1;	}	return 1;	}