Programming

Not what I mean. I mean, what problem are you trying to solve with this? Not how you want to do it -- what it's for.

I have a main parent code that collects data from every process it forks and then prints all of the data to a file.a child starts collecting data only when receiving a message.Otherwise waits.
The parent through a loop sends a certain number of messages to the children.
For example the parent sends 4 messages,and each one has to be received of one child that is waiting at the moment.When receiving the message it starts

You're just rephrasing what you want to do, over and over. I'm not looking for that.

I want to know what actual function you want to use this program for. Because I can think of lots of solutions for you, but nothing which obeys what you want to the letter, so knowing what you actually need would be better than knowing how you're hellbent on doing it.

Without any actual problem you're trying to solve beyond programming itself, it sounds contrived, like homework. And you've avoided answering, so I think it is. And therefore against the rules.