#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#define BUFFSIZE 3 /* >= 2 */
char *getline(void)
{
  static char inbuff[BUFFSIZE];
  char *outbuff_malloc, *tmpbuff;
  char *p;
  int fEOL;

  if ((outbuff_malloc = malloc(1)) == NULL)
    return NULL;
  *outbuff_malloc = '\0';
  fEOL = 0;
  do {
    if (fgets(inbuff, BUFFSIZE, stdin) == 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);
  return outbuff_malloc;
}

int main() {
  int f;
  char *s, *p, *q;
  printf("文字列を入力してください.: ");
  s = getline();
  f = 1;
  for (p = s, q = s + strlen(s) - 1; p < q; p++, q--) {
    printf("%c:%c\n", *p, *q);
    if (*p != *q) {
      f = 0;
      break;
    }
  }
  if (f == 1)
    printf("回文です.\n");
  else
    printf("回文ではありません.\n");
  free(s);
  return 0;
}
/* end */

文字列を入力してください.: 回文です.