Windows下EOF的值 [英] Value of EOF under windows

问题描述

我写了这段代码:

#include <stdio.h>

int main() {
    int c;

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

    return 0;
}

在Windows下，我发现必须输入ctrl + z才能停止程序，我还打印了EOF的值，它是-1.但是，当我输入-1而不是ctrl + z时，程序将继续执行，并且我想了解原因.谢谢！

Under windows, I figured out that I have to input ctrl+z so I can stop the program, I also printed the value of EOF and it's -1. However, when I enter -1 instead of ctrl+z the program continues to execute, and I want to understand why. Thank you!

推荐答案

以文本形式输入-1" 不会返回整数值 -1 ，而是两个字符，即'-'(对应于ASCII值 45 )和'1'(对应ASCII值 49 ).两者都不等于 EOF (十进制为 -1 ).

Entering "-1" as text does not return the integer value -1 but two characters, i.e. a '-' (which corresponds to ASCII value 45) and a '1' (which corresponds to ASCII value 49). Both do not compare equal to EOF (which is -1 in decimal).

根据定义，您不能输入 getchar()消耗为负值的内容，因为定义了负值来表示文件尾".

By definition, you cannot enter something that is consumed as negative value by getchar(), as negative values are defined to represent the "End-of-file".

如果要读取整数值(例如 -1 )，请使用 scanf :

If you want to read in an integral value (like -1), use scanf:

int num;
if (scanf("%d", &num)==1) { // successfully read one valid integral value?
    printf("you entered number %d:", num);
}

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