How to use wait() and waitpid() for handling the child processes using SIGCHLD.

waitforchild.c

#include<stdio.h>
#include<stdlib.h>
#include<signal.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <string.h>

#define DELAY 5
int counter = 0;

int main(){

        void child_handler();
        void child_handler2();
        //signal(SIGCHLD, child_handler);
        signal(SIGCHLD, child_handler2);

        int numChilds;
        printf("Enter Number of Childs: ");
        scanf("%d", &numChilds);
        printf("\nParent %d creating %d childs..\n\n", getpid(), numChilds);

        void child_code();
        int fork_rv, i;

        for(i=0; i<numChilds; i++){

                fork_rv = fork();               //create new process

                if ( fork_rv == -1 )            //check for errors
                        perror("fork");

                else if ( fork_rv == 0 ){       //Handle child processes
                        child_code(DELAY);
                }
        }

        while(counter < numChilds){             //Parent process wait for child processes to complete
                printf("Parent waiting for children..\n");
                sleep(1);
        }

        return 0;

}

/* New process takes a nap and then exits */
void child_code(int delay)
{
        printf("Child %d created.\n", getpid());
        sleep(delay);
        exit(17);
}

/* Wait for children to exit. */
void child_handler(int signum){

        int status;
        pid_t pid;

        pid = wait(&status);
        printf("Child %ld exited.\n", (long)pid);
        counter++;

}

/* Handle the missing child problem with waitpid() function*/
void child_handler2(int signum){
        pid_t p;
        int status;

        while((p=waitpid(-1, &status, WNOHANG)) > 0){
                printf("Child %ld exited.\n", (long)p);
                counter++;
        }
}