count words

#include <ctype.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
typedef struct word word;
struct word {
  char *word;
  int count;
  word *next;
};
static word *word_alloc(char *w) {
  word *new = calloc(1, sizeof *new);
  new->word = strdup(w), new->count = 1, new->next = NULL;
  return new;
}
static void word_free(word *p) {
  if (!p) { return; }
  word_free(p->next), free(p->word), free(p);
}
static void add_word(word **head, char *w) {
  if (!*head) {
    *head = word_alloc(w);
    return;
  }
  for (word *p = *head; p; p = p->next) {
    if (!strcmp(w, p->word)) {
      ++p->count;
      return;
    }
  }
  word *new = word_alloc(w);
  new->next = *head, *head = new;
}
static void input(FILE *in, word **head) {
  char buf[BUFSIZ];
  while (fgets(buf, BUFSIZ, in)) {
    for (char *p = buf; *p; ++p) {
      if (!isalpha(*p)) { *p = ' '; }
      *p = tolower(*p);
    }
    char w[BUFSIZ];
    for (char *p = buf; *p; ++p) {
      if (isblank(*p)) { continue; }
      if (sscanf(p, "%s", w) == 1) { add_word(head, w), p += strlen(w); }
    }
  }
}
static void show_word(word *head) {
  for (word *p = head; p; p = p->next) { printf("%s %d\n", p->word, p->count); }
}
int main(int argc, char **argv) {
  FILE *in = stdin;
  if (argc == 2) { in = fopen(argv[1], "r"); }
  word *head = NULL;
  input(in, &head), show_word(head), word_free(head), fclose(in);
}