std_io_buffer_type.c

#include "apue.h"

void pr_stdio(const char *, FILE *);

int main(void)
{
    FILE *fp;
    fputs("enter any character\n", stdout);
    if (getchar() == EOF)
        err_sys("getchar error");
    fputs("one line to stderror \n", stderr);

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

    if ((fp = fopen("/etc/motd", "r")) == NULL)
        err_sys("fopen error");
    pr_stdio("/etc/motd", fp);
    exit(0);
}

void pr_stdio(const char *name, FILE *fp)
{
    printf("stream = %s,  ", name);

    if (fp->_IO_file_flags & _IO_UNBUFFERED)
        printf("unbuffered");
    else if(fp->_IO_file_flags & _IO_LINE_BUF)
        printf("line buffered");
    else
        printf("fully buffered..");

    printf("  ,buffer size= %d\n",fp->_IO_buf_end - fp->_IO_buf_base);
}