Question

I am trying to add a parallel processing component to a single thread single process program. I am just learning some of the multi-processing methods and as such am not totally sure of their capabilities.

The program logic I am looking to implement:

• main process calls a function.
  • called function fork()’s at start of a for loop.
    • child continues with function work either performing other sub-functions or exiting back based on time checks.
  • meanwhile, parent ends first for loop round and starts again thus re-forking a second child.
• function continues until for loop finishes after around 10 fork()’s have been executed.
• function gets called again once completed based on a higher level timer.

Will this implementation work? Example code:

check_timer() {
   for(i = 0; i < 10; i++) {
      pid_t pid = fork();
      if(pid == 0) {
         execute child 1 checks and possible executes..
         exit(); // when completed
      }
      else {
         parent maybe does something or just ends first round of for loop..
      }
   }
some implementation of wait(); to wait for all children to finish before leaving check_timer() function..
}

Will this create up to 10 child processes at once executing in the background of a parent that then waits for the children to finish? Also some tips on how to use wait() would be helpful.

Answer 1

Yes, you will end up with 11 processes in total.

You likely want the waitpid function, called until there are no more children (a return of ECHILD).

EDIT: just noticed you need pid_t pid = fork();, not pid = pid();