用scanf_s读取字符 [英] Reading a character with scanf_s

问题描述

我只是在弄乱C语言，遇到了这个小问题.如您从我的输出中看到的，我得到这个字符╠".

I was just messing around with C and ran into this small problem. As you can see from my output I getting '╠' this character.

#include <stdio.h>

int main(void)
{
    char c;

    printf("Do you want to be X's or O's?\n");
    scanf_s("%c", &c);
    printf("You chose %c\n", c);

}

请参见程序输出

推荐答案

您正在滥用scanf_s(). Microsoft编译器可能会警告您使用其安全扩展(也称为c11附件k).但是，请谨慎操作. scanf_s()不能直接替代scanf().

You are misusing scanf_s(). Microsoft compilers may warn you to use their secure extensions (aka c11 annex k). But, be careful if you do so. scanf_s() is not a direct replacement for scanf().

在这种情况下，您必须将输出缓冲区的大小作为附加参数传递.

In this case you have to pass the size of the output buffer as an extra argument.

char c;

scanf_s("%c", &c, 1);

必须将1设置为单个字符的大小，似乎有些花哨.这是因为%c可以读取任意数量的字符. %c只是%1c的别名(单个字符).

Having to put a 1 as the size of a single character may seem a bit pedantic. That's because %c can read any number of character. %c is just an alias for %1c (a single character).

通过了解缓冲区大小scanf_s()是为防止缓冲区溢出(存在安全风险)而设计的.

By knowing the buffer size scanf_s() is designed prevent buffer overflow (a security risk).

尽管这些功能到底能起到多大作用，仍有待商..请参阅:附件K的现场经验.

Although, how much these functions really help is debatable. See: Field Experience With Annex K.

根据msdn :

与scanf和wscanf不同，scanf_s和wscanf_s需要缓冲区大小 为c，C，s，S或字符串类型的所有输入参数指定 []中包含的控件集.缓冲区大小(以字符为单位)为 紧跟在指针之后作为附加参数传递 缓冲区或变量.

Unlike scanf and wscanf, scanf_s and wscanf_s require the buffer size to be specified for all input parameters of type c, C, s, S, or string control sets that are enclosed in []. The buffer size in characters is passed as an additional parameter immediately following the pointer to the buffer or variable.

...

对于字符，单个字符可以如下读取:

In the case of characters, a single character may be read as follows:

字符c;

scanf_s(％c"，& c，1);

scanf_s("%c", &c, 1);

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