函数名: setbuf 
 功  能: 把缓冲区与流相联 
 用  法: #include <stdio.h>
         void setbuf(FILE *steam, char *buf); 
 程序例: 
#include <stdio.h>
/* BUFSIZ is defined in stdio.h */ 
 char outbuf[BUFSIZ]; 
int main(void) 
 { 
    /* attach a buffer to the standard output stream */ 
    setbuf(stdout, outbuf); 
   /* put some characters into the buffer */ 
    puts("This is a test of buffered output.\n\n"); 
    puts("This output will go into outbuf\n"); 
    puts("and won't appear until the buffer\n"); 
    puts("fills up or we flush the stream.\n"); 
   /* flush the output buffer */ 
    fflush(stdout); 
   return 0; 
 }