UNIX环境高级编程1-3用标准I/O将标准输入复制到标准输出

// program 1-3 file/getcputc.c
#include "apue.h"
/*
The standard I/O functions provide a buffered interface to the unbuffered I/O
functions. Using standard I/O relieves us from having to choose optimal buffer sizes,
such as the BUFFSIZE constant in Figure 1.4. The standard I/O functions also simplify
dealing with lines of input (a common occurrence in UNIX applications). The fgets
function, for example, reads an entire line. The read function, in contrast, reads a
specified number of bytes. As we shall see in Section 5.4, the standard I/O library
provides functions that let us control the style of buffering used by the library.
The most common standard I/O function is printf. In programs that call
printf, we will always include <stdio.h> normally by including apue.h as this
header contains the function prototypes for all the standard I/O functions.

The function getc reads one character at a time, and this character is written by putc.
After the last byte of input has been read, getc returns the constant EOF (defined in
<stdio.h>). The standard I/O constants stdin and stdout are also defined in the
<stdio.h> header and refer to the standard input and standard output.
*/
int main()
{
    int c;

    while ((c = getc(stdin)) != EOF)
    {
        if (putc(c, stdout) == EOF)
        {
            err_sys("output error");
        }
    }

    if (ferror(stdin))
    {
        err_sys("input error");
    }

    return 0;
}