比较C中用户输入的字符 [英] Comparing user-inputted characters in C

问题描述

以下代码段来自C程序。

The following code snippets are from a C program.

用户输入Y或N。

char *answer = '\0';

scanf (" %c", answer);

if (*answer == ('Y' || 'y'))
    // do work

我不知道为什么 if 语句的计算结果不正确。

I can't figure out why this if statement doesn't evaluate to true.

我用 printf 检查了y或n输入，它在那里，所以我知道我正在得到用户输入。另外，当我将if语句的条件替换为1（使它成为真）时，它的计算结果正确。

I checked for the y or n input with a printf and it is there, so I know I'm getting the user input. Also when I replace the the condition of the if statement with 1 (making it true), it evaluates properly.

推荐答案

两个问题：

指针 answer 是 null 指针，并且您试图在 scanf 中取消引用它，这会导致未定义行为。

The pointer answer is a null pointer and you are trying to dereference it in scanf, this leads to undefined behavior.

此处不需要 char 指针。您可以将 char 变量用作：

You don't need a char pointer here. You can just use a char variable as:

char answer;
scanf(" %c",&answer);

接下来看读取的字符是否为'y'或'Y'，您应该这样做：

Next to see if the read character is 'y' or 'Y' you should do:

if( answer == 'y' || answer == 'Y') {
  // user entered y or Y.
}

如果您真的需要使用char指针，则可以执行以下操作：

If you really need to use a char pointer you can do something like:

char var;
char *answer = &var; // make answer point to char variable var.
scanf (" %c", answer);
if( *answer == 'y' || *answer == 'Y') {

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