if ((instream=fopen(currentfilein,"r+"))==NULL)
 {
  printf("Problem with rr %s...",currentfilein);
  getch();
  exit(1);
 }

  fpos_t pos=-1;
  char chh;
  fseek(instream,pos,SEEK_END);
  chh=fgetc(instream);
  while((((chh=='\r')||(chh=='\n'))&&(!feof(instream))))
  {
   --pos;
   fseek(instream,pos,SEEK_END);
   chh=fgetc(instream);
   printf("%ld %c\n",pos, chh);
  }
   fputc(chh,instream);
  fclose(instream);
 }
}

#include <fcntl.h>
#include <io.h>

...

   FILE *instream = fopen(currentfilein, "rb");

   if(!instream)
   {
      fprintf(stderr, "Problem with rr %s...", currentfilein);
      exit(1);
   }

   fseek(instream, 0, SEEK_END);
   long file_size = ftell(instream);

   if(file_size)
   {
      long pos = -1;
      fseek(instream, pos, SEEK_END);

      char chh = fgetc(instream);
      while(chh == '\r' || chh == '\n')
      {
         fseek(instream, --pos, SEEK_END);
         chh = fgetc(instream);
      }
      fclose(instream);

      int fd = _open("1.txt", _O_RDWR);
      _chsize(fd, file_size + pos + 1);
      _close(fd);
   }