A Process' Lifetime

A process is only created as a copy of an existing process
fork(2) takes no arguments and returns integer
It returns 0 in the child and the child's pid in the father
Thus, the processes share files, signals and all the rest
The child, still running the parent's code, can change itself
Any process can change itself, the new child is not special
A typical child closes files, changes directory, etc
A process can execute a different file, through execve(2)
The call never returns: the process is replaced completely
All attributes (beside the memory image) remain unchanged
A process can wait for children to die, or get notified about it
The system sends SIGCHLD to the parent, that can use it
The parent can actively wait(2), in blocking or non-blocking mode

        if (fork() == 0)
                execlp("sleep", "sleep", "1", NULL);
        else
                wait(NULL);
        exit(0);