Glynn Clements
The point is that the Unix documentation does not consider the short pause as data is read off your hard drive to be blocking. So that's why select will always report that data is available when you use it with a file handle.
Isn't this also for historic reasons?
Partly.
But I think that it's also because this functionality wasn't intended for the purpose which is being discussed, i.e. enabling a process to obtain maximal CPU utilisation.
I think it's also because if we considered reading from a slow file to be blocking, we should also consider blocking many other calls which access a disk. In particular anything which takes or returns a filename; resolving a filename may involve reading a slow disk. But in these cases the system doesn't know whether the programmer really intended to do something else while mkdir() is completing, because mkdir() is not performed on a file descriptor on which non-blocking mode could have been set or reset. It would need quite a different API. -- __("< Marcin Kowalczyk \__/ qrczak@knm.org.pl ^^ http://qrnik.knm.org.pl/~qrczak/