c++ - select(NULL, NULL, NULL, &timeout) 只是等待给定的时间吗？

Question

我在给定的代码中看到了以下行:

select(0, (fd_set *) NULL, (fd_set *) NULL, (fd_set *) NULL, &timeout);

http://linux.die.net/man/2/select

Each of the three file descriptor sets may be specified as NULL if no file descriptors are to be watched for the corresponding class of events.

所以我可以看到将NULL传递给它是有效的。那样的话只能导致做主动等待。

这是正确的吗？我有点不确定..

Answer 1

Some code calls select() with all three sets empty, nfds zero, and a non-NULL timeout as a fairly portable way to sleep with subsecond precision.

取自here .