[Linux流操作]查看三种标准流的缓冲方式

#include <stdio.h>
#include <stdlib.h>
#if defined(MACOS)
#define _IO_UNBUFFERED  __SNBF
#define _IO_LINE_BUF    __SLBF
#define _IO_file_flags  _flags
#define BUFFERSZ(fp)    (fp)->_bf._size
#else
#define BUFFERSZ(fp)    ((fp)->_IO_buf_end - (fp)->_IO_buf_base)
#endif
void    pr_stdio(const char *, FILE *);
int main(void)
{
FILE    *fp;
printf("pls enter some str\n");  //提示输入部分字符
if (getchar() == EOF)   //如果EOF错误
{
perror("getchar error");
}
fputs("one line to standard error\n", stderr);

pr_stdio("stdin",  stdin);
pr_stdio("stdout", stdout);
pr_stdio("stderr", stderr);   //输出相应的缓冲类型
perror("fopen error");
if (getc(fp) == EOF)
perror("getc error");
pr_stdio("/etc/motd", fp);
exit(0);
}
//缓冲输出函数
void  pr_stdio(const char *name, FILE *fp)
{
printf("stream = %s, ", name);   //打印缓冲名称
if (fp->_IO_file_flags & _IO_UNBUFFERED)
printf("unbuffered");
else if (fp->_IO_file_flags & _IO_LINE_BUF)
printf("line buffered");
else /* if neither of above */
printf("fully buffered");
printf(", buffer size = %ld\n", BUFFERSZ(fp));
}

//这是一个分别打印三个标准流和一个文件流
//的缓冲方式的应用实例
#include <stdio.h>
#include <stdlib.h>

#if defined(MACOS)
#define _IO_UNBUFFERED  __SNBF
#define _IO_LINE_BUF    __SLBF
#define _IO_file_flags  _flags
#define BUFFERSZ(fp)    (fp)->_bf._size
#else
#define BUFFERSZ(fp)    ((fp)->_IO_buf_end - (fp)->_IO_buf_base)
#endif
//以上是关于缓冲方式和缓冲区大小的预定义
void pr_stdio(const char *, FILE *);
//子函数声明
int main(int argc,char *argv[])
{
FILE  *fp;   //流文件结构指针
pr_stdio("stdin",  stdin);    //标准输入
pr_stdio("stdout", stdout);   //标准输出
pr_stdio("stderr", stderr);   //标准出错处理
printf("fopen error");
if (getc(fp) == EOF)
{
printf("getc error\n");
}
return 0;
}
//测试缓冲输出函数
void  pr_stdio(const char *name, FILE *fp)
{
printf("当前流是%s, ", name);   //打印流的名称
if (fp->_IO_file_flags & _IO_UNBUFFERED)
{
printf("无缓冲\n");
}
else if (fp->_IO_file_flags & _IO_LINE_BUF)
{
printf("行缓冲\n");
}
else
{
printf("全缓冲\n");
}
printf(", 缓冲区大小 = %ld\n", BUFFERSZ(fp));
return;
}