Write continuously from parent process to child process in C

Question

I'm trying to play with processes and fork() to get a better idea about how they work. Right now, I'm trying to write a program that takes shell input and writes the integers from inputs k to q from the parent process to a child process. Here's my code so far, I don't understand why it's not working properly though, I closed all the pipes and the code is pretty small.

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h> /* pipe, fork */
#include <sys/wait.h> /* wait */
#include <sys/types.h> /* pid_t */

void testProc(int k, int q){
  pid_t new_proc;
  int fd[2];
  pipe(fd);
  new_proc = fork();
  int w;

  if (new_proc > 0) {

    close(fd[0]);
    for(w=k; w < q; w++) {
      write(fd[1], &w,sizeof(int));
      printf("Wrote %i out of %i\n", k, q);
    }
    close(fd[1]);
  }

  else if (new_proc == 0) {
    close(fd[1]);
    while(read(fd[0], &w, sizeof(int) ) > 0) {
      printf("Child received %i out of %i from Parent.\n", k, q);
    }
    close(fd[0]);
    exit(1);
  }

  else{
    printf("Fork failed\n");
    exit(1);
  }
}

int main(int argc, char *argv[]) {
  int n, m;

  if (argc != 3) {
    fprintf(stderr, "Need 3 arguments\n");
    return -1;
  }

  m = atoi(argv[2]);
  n = atoi(argv[1]);

  testProc(n, m);
  return 0;
}

I realize this code should check the other system calls like close() read and write, I also understand that using atoi is a bad idea. I'm skipping over these things in my question to make it as concise as possible.

The output I get when I run ./testProc 4 8

Wrote 4 out of 8
Wrote 4 out of 8
Wrote 4 out of 8
Wrote 4 out of 8
Child received 4 out of 8 from Parent.
Child received 4 out of 8 from Parent.
Child received 4 out of 8 from Parent.
Child received 4 out of 8 from Parent.

It's only getting the first value, I don't understand why? How would I pass a stream of integers from k to q between processes if not like this? Thank you!

Answer 1

Seems your

printf("Wrote %i out of %i\n", k, q);

should be

printf("Wrote %i out of %i\n", w, q);
                               ^^ 
                              w here

Same when you print it out in the child process.