a.c

#include <stdio.h>
#include <stdbool.h>

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

int main() {
  // pid_t parent = getpid();
  while(true) {
    pid_t child = fork();
    if(child < 0) {
      fprintf(stderr, "fork() failed\n");
      return 1;
    }
    if(child == 0) {
      execlp("date", "date", NULL);
    } else {
      int status;
      waitpid(child, &status, 0);
    }
  }
  return 0;
}

b.c

#include <stdio.h>
#include <stdbool.h>

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

int main() {
  // pid_t parent = getpid();
  while(true) {
    pid_t child;
    char spawn_argv0[] = "date";
    char * const spawn_argv[2] = {spawn_argv0, NULL};
    int result = posix_spawnp(
        &child,
        "date",
        NULL,
        NULL,
        spawn_argv,
        environ);
    if(result < 0) {
      fprintf(stderr, "posix_spawnp() failed\n");
      return 1;
    }
    int status;
    waitpid(child, &status, 0);
  }
  return 0;
}

Makefile

#!/usr/bin/make -f

EXECS = a b

CC = gcc
CFLAGS = -std=c99 -O2 -Wall -Wextra -ggdb

all: $(EXECS)

clean:
	$(RM) $(EXECS)