int main(int argc, char *argv[]) {
  // read file
  char *content = NULL;
  if (argc != 2 || !(content = get_file_contents(argv[1])))
    exit(EXIT_FAILURE);

  // find the number of words
  unsigned long words_count = 0;
  bool inword = false;
  for (char *s = content; *s; ++s) {
    if (isalpha(*s)) { // C locale: upper, lower letter
      if (!inword) { // new word
        inword = !inword;
        ++words_count;
      }
    }
    else if (inword) {
      inword = !inword; // end of word
    }
  }

  // put words into array
  char* *words;
  if (words_count > (SIZE_MAX / sizeof *words)
      || !(words = (char**)malloc(words_count * sizeof *words)))
    exit(EXIT_FAILURE); // let OS cleanup memory

  char *s = content; // rewind
  for (unsigned long i = 0; i < words_count; ++i) {
    for ( ; !isalpha(*s); ++s);  // find start of the word
    words[i] = s;
    for ( ; isalpha(*s); ++s);   // find end of the word
    *s = '';
  }
  // print words
  for (unsigned long i = 0; i < words_count; ++i) puts(words[i]);
}

/// read file into null-terminated C-string
char* get_file_contents(const char* filename) {
  FILE *fp = NULL;
  unsigned long size;
  char *buf = NULL;

  if((fp = fopen(filename, "rb"))
     && !fseek(fp, 0, SEEK_END)
     && (size = ftell(fp)) != (unsigned long)EOF   // find file size
     && size < LONG_MAX && size < SIZE_MAX
     && (buf = (char*)malloc(size + 1)) // allocate memory for the content
     && (rewind(fp), 1)
     && fread(buf, sizeof *buf, size, fp) == size  // read the content
     && !fclose(fp)) {
    buf[size] = '';
    return buf;
  }

  // error
  if (fp) fclose(fp);
  free(buf);
  return NULL;
}