#include<assert.h>
#include<stdio.h>

int main (int argc, char *argv[])
{
   FILE *fp;
   int res;
   long len;

   fp = fopen("testappend", "wb+");
   res = fwrite("1234567890", 10, 1, fp);
   fclose(fp);

   fp = fopen("testappend", "ab+");
   res = fwrite("1234567890", 10, 1, fp);

   fseek(fp, -7, SEEK_END);
   len = ftell(fp);
   assert(len == 13);
   fclose(fp);

   puts("success");
   return 0;
}