C语言库fflush()函数

#include <stdio.h>
#include <string.h>
#include <unistd.h>

int main () {
   char buff[1024];
   memset( buff, '\0', sizeof( buff ));

   fprintf(stdout, Going to set full buffering on\n);
   setvbuf(stdout, buff, _IOFBF, 1024);

   fprintf(stdout, This is jb51.cc.com\n);
   fprintf(stdout, This output will go into buff\n);
   fflush( stdout );

   fprintf(stdout, and this will appear when programm\n);
   fprintf(stdout, will come after sleeping 5 seconds\n);

   sleep(5);
   return(0);
}