Thread: forks and child processes

Hi,

I have a requirement to write a C program, in which a parent process creates 3 child processes. Each of these three child processes are required to run individual programs and once complete, the parent will then exit.

I've managed to create the parent, and 1 child, which does execute a program called average.

I'm stuck at changing this so that I have 3 childs created and each having a different program run. Any help would be appreciated.

main.c

Code:

#include <sys/types.h>
#include <unistd.h>
#include <sys/wait.h>

int main(void) {
	pid_t child_pid;
	int status;
	pid_t wait_result;
	child_pid = fork();

	if (child_pid == 0)
	{
		printf("I am a child and my pid = %d\n", getpid());
		execlp("average", "./average", NULL);

		printf("Could not execl file average\n");
		exit(1);

	}

        else if (child_pid > 0)
	{
		printf("I am the parent and my pid = %d\n", getpid());
		printf("My child has pid = %d\n", child_pid);
	}

        else
	{
		printf("The fork system call failed to create a new process\n");
		exit(1);
	}


	printf("I am a happy, healthy process and my pid = %d\n", getpid());


	if (child_pid == 0)
	{
 	printf("This code will never be executed!\n");
	}
	else
	{
		printf("I am a parent and I am going to wait for my child.\n");
		do {

			wait_result = wait(&status);
		} while (wait_result != child_pid);
		printf("I am a parent and I am quitting.\n");
	}

	return 0;
}

and the average.c file - which works perfectly fine!

Code:

/* average.c */
/*
  Program to calculate the average of n numbers

*/

#include <stdio.h>
#include <stdlib.h>

#define NMAX 100

int main() 
{
  int n, count;
  double avg, d, sum = 0.;
  double list[NMAX];

  /* Read in value for n */
  printf("\nHow many numbers do you want to average? ");
  scanf("%d", &n);
  
  /* Check that n is not too large or too small */
  if ((n > NMAX) || (n <= 0)) 
   {
    printf("\nPlease enter an integer only... program will terminate\n");
    exit(1);
   }

  /* Read in the numbers and calculate their sum */
  for (count = 0; count < n; ++count) 
   {
    printf("Enter %d number: ", count + 1);
    scanf("%lf", &list[count]);
    sum += list[count];
   }

  /* Calculate and display the average */
  avg = sum / (double) n;
  printf("\nAverage is %5.2f\n\n", avg);

  
}

Appreciate any advice. I'm very new to the concept of programming and C, so I apologise in advance if this is a stupid question.

Cheers,
K