c语言 关于一个函数

看你括号里面的意思，我觉得应该是使用这个函数，是需要stdio.h这个头文件的；
但是fflush这个函数，需要的参数是一个结构体的指针；
fflush <stdio.h>
int fflush( FILE *stream );
Parameters
stream
Pointer to FILE structure
Libraries
All versions of the C run-time libraries.

Return Values
fflush returns 0 if the buffer was successfully flushed. The value 0 is also returned in cases in which the specified stream has no buffer or is open for reading only. A return value of EOF indicates an error.

Note If fflush returns EOF, data may have been lost due to a write failure. When setting up a critical error handler, it is safest to turn buffering off with the setvbuf function.
Remarks
The fflush function flushes a stream. If the file associated with stream is open for output, fflush writes to that file the contents of the buffer associated with the stream. If the stream is open for input, fflush clears the contents of the buffer. fflush negates the effect of any pri