函数名: clearerr 
 功  能: 复位错误标志 
 用  法: #include <stdio.h>
         void clearerr(FILE *stream); 
 程序例: 
#include <stdio.h>
int main(void) 
 { 
    FILE *fp; 
    char ch; 
   /* open a file for writing */ 
    fp = fopen("DUMMY.FIL", "w"); 
   /* force an error condition by attempting to read */ 
    ch = fgetc(fp); 
    printf("%c\n",ch); 
   if (ferror(fp)) 
    { 
       /* display an error message */ 
       printf("Error reading from DUMMY.FIL\n"); 
      /* reset the error and EOF indicators */ 
       clearerr(fp); 
    } 
   fclose(fp); 
    return 0; 
 }