Munmap anonymous shared memory in a split child

I would like to know if it is necessary (or desirable) to disable shared memory (using munmap

) in the child created with fork

if the memory was fetched in the parent, before fork using mmap(..., MAP_ANONYMOUS | MAP_SHARED,...)

, and also will not be displayed in the parent which will be wait

for the child ... Also I would like to know if it is necessary (or desirable) to close the file in the child if the file was opened in the parent (before the fork using fopen

) and will be closed in the parent after the child completes.

I am thinking about using a custom signal and a signal handler where the parent will wait for the child processes and then the process - if it is the parent or not - will close the file and unpack the memory.This signal will be sent to all processes in the group from the process in which the error occurred ( i dont want to pass return values).

It's actually a little more complicated, but I just want to know if I need to do this:

void sig_handler() {
    if (getpid() == getpgrp()) // parent
        while (proc_count--)
            wait(NULL); // signal has already been sent to all child processes
    // every single process will do this:
    fclose(memory->file);
    munmap(memory, size);
    exit(123);
}

      

        
        
        
      

    

or is this completely normal:

void sig_handler() {
    if (getpid() == getpgrp()) {
        while (proc_count--)
            wait(NULL);
        fclose(memory->file);
        munmap(memory, size);
    }
    exit(123);
}

      

        
        
        
      

    

I tried to close the file in one child process; it didn't seem to affect other processes - I'm assuming the fd table is copied to fork. Is there a way to make this split between processes? (Probably not, I suspect)

Any answer is appreciated. Thank.

PS. Is there a reason why I can't start my question with a greeting (like Hello)?