理论的getchar（）和背后的putchar（）函数 [英] Theory Behind getchar() and putchar() Functions

问题描述

我通过C程序设计语言的K＆放工作; R和示例1.5难倒我：

I'm working through "The C Programming Language" by K&R and example 1.5 has stumped me:

#include <stdio.h>

/* copy input to output; 1st version */
int main(int argc, char *argv[])
{
    int c;

    while ((c = getchar()) != EOF)
        putchar(c);

    return 0;
}

据我所知，'的getchar（）'需要一个字符'的putchar（）'来显示。然而，当我在终端运行程序，那为什么我可以通过人物的整个行'的putchar（）显示？

I understand that 'getchar()' takes a character for 'putchar()' to display. However, when I run the program in terminal, why is it that I can pass an entire line of characters for 'putchar()' to display?

推荐答案

由于您的终端是行缓冲。 的getchar（）和的putchar（）仍然只对单个字符工作，但终端与提交字符的程序等待直到你输入一整行。然后的getchar（）会从该缓冲区一个接一个，字符的putchar（）显示它们一个接 - 酮

Because your terminal is line-buffered. getchar() and putchar() still only work on single characters but the terminal waits with submitting the characters to the program until you've entered a whole line. Then getchar() gets the character from that buffer one-by-one and putchar() displays them one-by-one.

加入：终端是行缓冲意味着它遇到一个换行符时提交输入程序。它通常是更有效的在一个时间提交数据，而不是一个字符的块。它还为用户提供了一个机会来编辑前行pressing进入。

Addition: that the terminal is line-buffered means that it submits input to the program when a newline character is encountered. It is usually more efficient to submit blocks of data instead of one character at a time. It also offers the user a chance to edit the line before pressing enter.

注意：行缓冲可以通过禁用规范模式被关闭终端并调用则setbuf 与 NULL 在标准输入。

Note: Line buffering can be turned off by disabling canonical mode for the terminal and calling setbuf with NULL on stdin.

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