I/O流与缓冲

  1 /*
  2  * FILE: p659_stdio.c
  3  * DATE: 20180124
  4  * ==================
  5  * DESCRIPTION: stdin stdout stderr
  6  */
  7 
  8 #include <stdio.h>
  9 
 10 int main(void)
 11 {
 12         /* 标准输入stdin */
 13         printf("=== stdin ===\n");
 14         // 宏 _IO_UNBUFFERED 无缓冲
 15         if(stdin->_flags & _IO_UNBUFFERED)
 16                 printf("unbuffered 无缓冲\n");
 17         // 宏 _IO_LINE_BUF 行缓冲
 18         else if(stdin->_flags & _IO_LINE_BUF)
 19                 printf("line-buffered 行缓冲\n");
 20         // 宏 _IO_FULL_BUF 全缓冲
 21         else // if(stdin->_flags & _IO_FULL_BUF)        
 22                 printf("fully-buffered 全缓冲\n");
 23         printf("buff size is %d 缓冲区大小\n", stdin->_IO_buf_end-stdin->_IO_buf_base);
 24         printf("discriptior is %d 文件描述符\n\n", fileno(stdin));
 25 
 26 
 27         /* 标准输出 stdout */
 28         printf("=== stdout ===\n");
 29         if(stdout->_flags & _IO_UNBUFFERED)
 30                 printf("unbuffered\n");
 31         else if(stdout->_flags & _IO_LINE_BUF)
 32                 printf("line-buffered 行缓冲\n");
 33         else
 34                 printf("fully-buffered\n");
 35         printf("buffer size is %d\n", stdout->_IO_buf_end-stdout->_IO_buf_base);
 36         printf("descriptior si %d\n\n", fileno(stdout));
 37 
 38 
 39         /* 标准出错 stderr */
 40         printf("=== stderr ===\n");
 41         if(stderr->_flags & _IO_UNBUFFERED)
 42                 printf("unbuffered 无缓冲\n");
 43         else if(stderr->_flags & _IO_LINE_BUF)
 44                 printf("line buffered\n");
 45         else
 46                 printf("fully-buffered\n");
 47         printf("buffer size is %d\n", stderr->_IO_buf_end-stderr->_IO_buf_base);
 48         printf("descriptior si %d\n\n", fileno(stderr));
 49         return 0;
 50 }