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 yiibai.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);
}