[TUHS] fork

[Ron Natalie via TUHS]

Processes stay zombines until someone waits for them.    If their parent 
is alive, it will have to execute a wait() to get the status.   If the 
parent is dead, prossess 1 (historically INIT) will becoe the parent for 
the purpose of wain().

Note that there are differing SIGCHLD / SIGCLD behaviors,    In addition 
to the sitnal being caught telling the process that there’s something to 
wait on, some systems take specifally setting SIGCHLD to SIG_IGN as an 
indiation
that you don’t ever want to wait and any children when they die will 
immediately go away without entering the zombine state.