strchrtok

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <stdbool.h>
#define NMAX 100
#define SEP ','

int main(void) {
  static char s[NMAX];
  if (fgets(s, NMAX, stdin) == NULL) {
    perror("");
    exit(EXIT_FAILURE);
  }
  s[strlen(s) - 1] = 0;

  char *p1 = s, *p2 = NULL;
  bool found = true;
  while (found) {
    char *s = NULL;
    p2 = strchr(p1, SEP);
    if (p2) {
      int len = p2 - p1 + 1;
      s = malloc(sizeof(char) * len);
      strncpy(s, p1, len - 1);
      s[len - 1] = 0;
      p1 = p2 + 1;
    } else {
      int len = strlen(p1) + 1;
      s = malloc(sizeof(char) * len);
      strcpy(s, p1);
      found = false;
    }

    if (!*s) {
      free(s);
      continue;
    }

    puts(s);
    free(s);
  }
  return 0;
}