select 함수 return value problem

간단히 source를 보여드리겠습니다

#define FIRST	"fifo_file"
#define SECOND     "/dev/xxxx"  

char	buff[BUFF_SZ];
int	state;
struct	timeval tv;
fd_set	readfds;


/* fifo 초기화 */
fd[0] = open(FIRST, O_RDONLY);
fd[1] = open(SECOND, O_RDONLY);

for (;;)
{
                FD_ZERO(&readfds);
                FD_SET(fd[0], &readfds);
                FD_SET(fd[1], &readfds);

                tv.tv_sec = 1;
                tv.tv_usec = 0;

                state = select(fd[1]+1, &readfds, (fd_set *)0, (fd_set *)0, &tv);
                switch (state)
                {
                 case -1:
	                perror("select error : ");
	                printf("errno %d\n", errno);
                                exit(0);
                  case 0:
                                break;
                 default :
                                if (FD_ISSET(fd[0], &readfds))
                                {
                                           if (read(fd[0], buff, BUFF_SZ) > 0)
                                            /* data 처리 */
                                 }

                  	if (FD_ISSET(fd[1], &readfds))
                	{
	                            if (ioctl(fd[2], 0, &data) == 0) 
		             /* data 처리 */
                                }
                                break;
                 }
}