While it's a common error description, "it doesn't work" does not help us with diagnosing what exactly does not work, and how it doesn't work. If you need to collect all results from the work of the children in the parent process, you will either have to use threads or you will have to create a communication channel between the children and the parent process, for example by writing the information to a file and by then reading that information in the parent process as the children exit.