Undefined reference to ' fclose ' errors occurred while doing Nios II uart232 experiments.

The procedure is as follows

#include <stdio.h> #include <string.h> #include   "system.h"  int main  () {   char* msg =  "detected the character  ' t '. \ n";  file* fp;   char prompt = 0;  printf ("Please enter some characters:  \n ");  fp = fopen  ("/dev/uart_0 ", " r+ ");  //open file for read and write   if   (FP)   {     while  (prompt !=  ' V ')  //  Loop until receiving   ' V '      {        prompt =  GETC (FP); //  get character         if  from Jtag uart (prompt  ==  ' t ')         {  //  if the character is   ' t '   Print Info         fwrite  (msg, strlen  (msg), &NBSP;1,&NBSP;FP) ;         }        if  (Ferror (FP))//  Check if the error appears with the file pointer              clearerr (FP);//  If yes, clear it      }     fprintf (fp,  "Closing the UART  file handle.\n ");     fclose  (FP);  }  else   {    printf ("fail to open file...\n");   }return 0;}   error is as follows   wrong reason for detailed connection address http://www.altera.com.cn/support/kdb/solutions/rd10152012_873.html

Undefined reference to ' fclose ' errors occurred while doing Nios II uart232 experiments.