Sorry, you didn't understand me (my error). Of course i know that file handler is cloned between threads. But i need more: i need to open file handler in the thread and allow other threads to write to it.
Or shortly i need a solution to write to log file (from each thread). This is easy. But i'm also need to check for log size. So if it arrive some value i need to close old log file and open new one. And this event (maximum log file) occur in one of the thread (i have shared variable which increment after each write to log).