led-player里main的一段程序，这个for死循环是怎么跳出来的？或者要弄明白这个管道的东西看什么资料容易理解，是怎么工作的？
求google的关键词。
for (;;) {
fd_set rds;
struct timeval step;
int ret;
FD_ZERO(&rds);
FD_SET(led_control_pipe, &rds);
step.tv_sec = period;
step.tv_usec = (period - step.tv_sec) * 1000000L;
ret = select(led_control_pipe + 1, &rds, NULL, NULL, &step);
if (ret < 0) {
perror("select");
exit(1);
}
if (ret == 0) {
push_leds();
} else if (FD_ISSET(led_control_pipe, &rds)) {
static char buffer[200];
for (;;) {
char c;
int len = strlen(buffer);
if (len >= sizeof buffer - 1) {
memset(buffer, 0, sizeof buffer);
break;
}
if (read(led_control_pipe, &c, 1) != 1) {
break;
}
if (c == '\r') {
continue;
}
if (c == '\n') {
int tmp_type;
double tmp_period;
if (sscanf(buffer,"%d%lf", &tmp_type, &tmp_period) == 2) {
type = tmp_type;
period = tmp_period;
}
fprintf(stderr, "type is %d, period is %lf\n", type, period);
memset(buffer, 0, sizeof buffer);
break;
}
buffer[len] = c;
}
}
}
