函数名: fflush 
 功  能: 清除一个流 
 用  法: #include <stdio.h> 
         int fflush(FILE *stream); 
 程序例: 
#include <string.h> 
 #include <stdio.h> 
 #include <conio.h> 
 #include <io.h> 
void flush(FILE *stream);
int main(void) 
 { 
    FILE *stream; 
    char msg[] = "This is a test"; 
   /* create a file */ 
    stream = fopen("DUMMY.FIL", "w"); 
   /* write some data to the file */ 
    fwrite(msg, strlen(msg), 1, stream); 
   clrscr(); 
    printf("Press any key to flush\ 
    DUMMY.FIL:"); 
    getch(); 
   /* flush the data to DUMMY.FIL without\ 
       closing it */ 
    flush(stream); 
   printf("\nFile was flushed, Press any key\ 
    to quit:"); 
    getch(); 
    return 0; 
 }  
void flush(FILE *stream) 
 { 
      int duphandle; 
     /* flush the stream's internal buffer */ 
      fflush(stream); 
     /* make a duplicate file handle */ 
      duphandle = dup(fileno(stream)); 
     /* close the duplicate handle to flush\ 
         the DOS buffer */ 
      close(duphandle); 
 }