prime multi process

primes.c

#include <stdio.h>
#include <stdlib.h>
#define MAX 35

int
generate() {
  int p[2];
  pipe(p);
  for (int i = 2; i < MAX; i++) {
    write(p[1], &i, sizeof(i));
  }
  close(p[1]);
  return p[0];
}

int
filter(int in_fd, int prime) {
  int num;

  int p[2];

  pipe(p);

  int pid = fork();
  if (pid > 0) {
    close(2);
    close(1);
    while (read(in_fd, &num, sizeof(num))) {
      if (num % prime) {
        write(p[1], &num, sizeof(num));
      }
    }
    close(in_fd);
    close(p[1]);
    wait((int *)0);
    exit(0);
  }
  close(in_fd);
  close(p[1]);
  return p[0];
}

int
main(int argc, char *argv[])
{
  close(0);
  int prime;
  int in = generate();
  while (read(in, &prime, sizeof(prime))) {
    printf("prime %d\n", prime);
    in = filter(in, prime);
  }
  wait((int *)0);

  exit(0);
}