#include <stdio.h>
#include <stdlib.h>
#include <string.h>

struct Lib_node {
  void *data;
  struct Lib_node *left, *right;
};
void lib_init_list(struct Lib_node **root)
{
  *root = NULL;
}
void *lib_add_list(struct Lib_node **root, void *data, int (*cmp)(void *, void *))
{
  int c;
  struct Lib_node *node;

  if (*root == NULL) {
    if((node = malloc(sizeof(struct Lib_node))) == NULL) {
      fprintf(stderr, "cannot allocate enoutgh memory.\n");
      exit(-1);
    }
    node->data = data;
    node->left = node->right = NULL;
    *root = node;
    return data;
  }
  if ((c = (*cmp)(data, (*root)->data)) < 0) {
    return lib_add_list(&((*root)->left), data, cmp);
  } else if (c > 0) {
    return lib_add_list(&((*root)->right), data, cmp);
  } else {
    return (*root)->data;
  }
}
void *lib_delmin_list(struct Lib_node **root)
{
  void *data;
  struct Lib_node *p;

  if (*root == NULL)
    return NULL;
  if ((*root)->left != NULL)
    return lib_delmin_list(&((*root)->left));
  data = (*root)->data;
  p = *root;
  *root = p->right;
  free(p);
  return data;
}
struct data {
  int num;
};
static int flagS;
int cmp(struct data *a, struct data *b)
{
  if (flagS == 1)
    return (b->num > a->num) ? 1 : -1;
  else
    return (a->num > b->num) ? 1 : -1;
}
#define BUFFSIZE 3 /* >= 2 */
char *getline(FILE *fp)
{
  static char inbuff[BUFFSIZE];
  char *outbuff_malloc, *tmpbuff;
  char *p, *q;
  int fEOL;
  if ((outbuff_malloc = malloc(1)) == NULL) {
    return NULL;
  }
  *outbuff_malloc = '\0';
  fEOL = 0;
  do {
    if ((q = fgets(inbuff, BUFFSIZE, fp)) == NULL)
      break;
    for (p = inbuff; *p != '\0'; p++)
      ;
    if (*(p - 1) == '\n') {
      *(p - 1) = '\0';
      fEOL = 1;
    }
    if ((tmpbuff = realloc(outbuff_malloc, strlen(outbuff_malloc) + strlen(inbuff) + 1)) ==NULL) {
      free(outbuff_malloc);
      return NULL;
    }
    strcat(tmpbuff, inbuff);
    outbuff_malloc = tmpbuff;
  } while (!fEOL);
  if (q == NULL) {
    free(outbuff_malloc);
    return NULL;
  }
  return outbuff_malloc;
}
void reg(struct Lib_node **root, int n)
{
  struct data *d;
  if ((d = malloc(sizeof(struct data))) == NULL) {
    fprintf(stderr, "cannot allocate enough memory.\n");
    exit(-1);
  }
  d->num = n;
  if (lib_add_list(root, d, (int (*)(void *, void *))cmp) == NULL) {
    fprintf(stderr, "cannot allocate enough memory.\n");
    exit(-1);
  }
}
void output(struct Lib_node **root, FILE *fp)
{
  struct data *p;
  while ((p = lib_delmin_list(root)) != NULL) {
    fprintf(fp, "%d\n", p->num);
    free(p);
  }
}
#define INPUTFILE "in.txt"
#define OUTPUTFILE "out.txt"
int main()
{
  FILE *fp;
  char *inputLine_malloc;
  struct Lib_node *root;
  int n;
  printf("並び替え方法を指定してください.(1:昇順, 2:降順)\n");
  scanf("%d", &n);
  if (n == 1)
    flagS = 1;
  else
    flagS = 0;
  if ((fp = fopen(INPUTFILE, "rt")) == NULL) {
    fprintf(stderr, "cannot open the input file, aborted.\n");
    exit(-1);
  }
  lib_init_list(&root);
  while ((inputLine_malloc = getline(fp)) != NULL) {
    if (sscanf(inputLine_malloc, "%d", &n) == 1)
      reg(&root, n);
    free(inputLine_malloc);
  }
  fclose(fp);
  if ((fp = fopen(OUTPUTFILE, "wt")) != NULL) {
    output(&root, fp);
    printf("並び替えた結果をファイルへ出力しました.\n");
    fclose(fp);
  }
  return 0;
}
/* end */

cannot open the input file, aborted.
並び替え方法を指定してください.(1:昇順, 2:降順)

Exited: ExitFailure 255