#include "apue.h"

int main(void)
{
    FILE *fp;

    fputs("enter any character\n",stdout);
    if(getchar()==EOF)
        err_sys("getchar error");
    fputs("one line to standard error\n",stderr);

    pr_stdio("stdin",stdin);
    pr_stdio("stdout",stdout);
    pr_stdio("stderr",stderr);

    if((fp==fopen("/etc/passswd","r"))==NULL)
        err_sys("fopen error");
    if(getc(fp)==EOF)
        err_sys("getc error");
    pr_stdio("/etc/passwd",fp);
    return 0;
}

void pr_stdio(const char *name, FILE *fp)
{
    printf("stream = %s,",name);
    if(is_unbuffered(fp))
        printf("unbuffered");
    else if(is_linebuffered(fp))
        printf("line buffered");
    else
        printf("fully buffered");
    printf(",buffer size= %d \n",buffer_size(fp));
}

#if defined(_IO_UNBUFFERED)

int is_unbuffered(FILE *fp)
{
    return (fp->_flags&_IO_UNBUFFERED);
}

int is_linebuffered(FILE *fp)
{
    return (fp->_flags&_IO_LINE_BUF);
}

int buffer_size(FILE *fp)
{
    return (fp->_IO_buf_end - fp->_IO_buf_base);
}

#elif defined(__SNBF)

int is_unbuffered(FILE* fp)
{
    return (fp->_flags &__SNBF);
}

int is_linebuffered(FILE *fp)
{
    return (fp->_flags &__SLBF);
}

int buffer_size(FILE *fp)
{
    return (fp->_bf._size);
}

#elif defined(_IONBF)

#ifdef _LP64

#define _flag __pad[4]
#define _ptr __pad[1]
#define _base __pad[2]
#endif

int is_unbuffered(FILE *fp)
{
    return (fp->_flag&_IONBF);
}

int is_linebuffered(FILE *fp)
{
    return (fp->_flag&_IOLBF);
}

int buffer_size(FILE *fp)
{
#ifdef _LP64
    return (fp->_base - fp->_ptr);
#else
    return (BUFSIZ);
#endif
}

#else

#error unknown stdio implementation!

#endif

各个标准I/O流打印缓冲状态信息