How to implement Callouts in Unix

I am trying to implement my own thread library 开发者_高级运维like pthread. I want to use callouts to call a function that updates priorities of threads after certain interval.

int to_id= timeout(fn,arg,time);

Can any one please provide some information regarding to how to use this and in which header file this function is available.

Is there any guide that help me to do this pthread implementation. Thanks in advance..

I think you mean "function callbacks". Start with this tutorial or this link.