直到换行使用scanf函数发现如何从输入读​​取（）？ [英] How to read from input until newline is found using scanf()?

问题描述

我被要求做在C工作的时候，我应该从输入读取，直到有一个空格，然后直到用户presses进入。
如果我这样做：

I was asked to do a work in C when I'm supposed to read from input until there's a space and then until the user presses enter. If I do this:

scanf("%2000s %2000s", a, b);

它会按照第1章，但不是第二个。结果
如果我写：

It will follow the 1st rule but not the 2nd.
If I write:

I am smart

我得到的是相当于：结果
A =I;结果
B =AM;结果
但它应该是：搜索
A =I;结果
B =很聪明，结果

What I get is equivalent to:
a = "I";
b = "am";
But It should be:
a = "I";
b = "am smart";

我已经尝试过：

scanf("%2000s %2000[^\n]\n", a, b);

和

scanf("%2000s %2000[^\0]\0", a, b);

在第一的，它等待用户preSS <大骨节病>控制 + <大骨节病> D （发送EOF）这不是我想要的。
在第二之一，它不会编译。根据编译器：

In the 1st one, it waits for the user to press Ctrl+D (to send EOF) and that's not what I want. In the 2nd one, it won't compile. According to the compiler:

警告：'％['格式没有结束]

warning: no closing ‘]’ for ‘%[’ format

要解决这个什么好的办法？

Any good way to solve this?

推荐答案

scanf函数（和表兄弟）有一个稍显陌生的特点：任何空白格式字符串空间（外一扫描集的）匹配的输入空格的任意量。碰巧的是，至少在默认的C区域，一个新的行被划分为空白。

scanf (and cousins) have one slightly strange characteristic: any white space in the format string (outside of a scanset) matches an arbitrary amount of white space in the input. As it happens, at least in the default "C" locale, a new-line is classified as white space.

这意味着尾随的'\\ n'尝试匹配不​​仅的在的新线，但任何成功的空白，以及。它不会被认为是匹配的，直到信号输入的结束，否则进入一些非空白字符。

This means the trailing '\n' is trying to match not only a new-line, but any succeeding white-space as well. It won't be considered matched until you signal the end of the input, or else enter some non-white space character.

要解决这个问题，你通常希望做这样的事情：

To deal with this, you typically want to do something like this:

scanf("%2000s %2000[^\n]%c", a, b, c);

if (c=='\n')
    // we read the whole line
else
    // the rest of the line was more than 2000 characters long. `c` contains a 
    // character from the input, and there's potentially more after that as well.

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