c - 为什么 gets() 可以正常工作，而 fgets() 却不能？

Question

我做了一个程序，找到了gets()，并使用了它，它很棒，但是当我编译程序时它说gets是危险的，所以我搜索了一个替代方案，即使gets()函数使它具有正确的输出，为了将来我宁愿使用一个不危险的替代方法，那是我偶然发现 fgets() 的时候。我认为代码会编译相同并具有相同的输出，但是没有输出我的 if 语句。

代码如下:

#include <stdio.h>
#include <string.h>

int main()
{
        char qOne[10];
        char qTwo[10];
        char guess[40] = "My guess is that you are thinking of a\0";

        printf("TWO QUESTIONS\n");
        printf("Think of an object, and i'll try to guess it.\n\n");

        printf("Question 1) Is it an animal, vegetable, or mineral?\n");
        printf("\n> ");
        //gets(qOne);
        fgets(qOne, 10, stdin);

        printf("\nQuestion 2) Is it bigger than a breadbox? (yes/no)\n");
        printf("\n> ");
        //gets(qTwo);
        fgets(qTwo, 10, stdin);

        printf("\n");

        if(strcmp(qOne, "animal") == 0 && strcmp(qTwo, "no") == 0 ||strcmp(qOne, "animal") == 0 && strcmp(qTwo, "No") == 0)

                printf("%s squirrel.\n", guess);

        else if(strcmp(qOne, "animal") == 0 && strcmp(qTwo, "yes") == 0 ||strcmp(qOne, "animal") == 0 && strcmp(qTwo, "Yes") == 0)

                printf("%s moose.\n", guess);

        else if(strcmp(qOne, "vegetable") == 0 && strcmp(qTwo, "no") == 0 ||strcmp(qOne, "vegetable") == 0 && strcmp(qTwo, "No") == 0)

                printf("%s carrot.\n", guess);

        else if(strcmp(qOne, "vegetable") == 0 && strcmp(qTwo, "yes") == 0 ||strcmp(qOne, "vegetable") == 0 && strcmp(qTwo, "Yes") == 0)

                printf("%s watermelon.\n", guess);

        else if(strcmp(qOne, "mineral") == 0 && strcmp(qTwo, "no") == 0 ||strcmp(qOne, "mineral") == 0 && strcmp(qTwo, "No") == 0)

                printf("%s paper clip.\n", guess);

        else if(strcmp(qOne, "mineral") == 0 && strcmp(qTwo, "yes") == 0 ||strcmp(qOne, "mineral") == 0 && strcmp(qTwo, "Yes") == 0)

                printf("%s Camaro.\n", guess);


        printf("\nI would ask you if I'm right, but I don't actually care.\n");

        return 0;
}

此代码的输出是(输入字符串“animal”和“yes”):

TWO QUESTIONS
Think of an object, and i'll try to guess it.

Question 1) Is it an animal, vegetable, or mineral?

> animal

Question 2) Is it bigger than a breadbox? (yes/no)

> yes


I would ask you if I'm right, but I don't actually care.

然而，当我只使用 gets() 而不是 fgets() 时，我的代码给出了正确的输出，即:

TWO QUESTIONS
Think of an object, and i'll try to guess it.

Question 1) Is it an animal, vegetable, or mineral?

> animal

Question 2) Is it bigger than a breadbox? (yes/no)

> yes

My guess is that you are thinking of a moose.

I would ask you if I'm right, but I don't actually care.

如何使用 fgets() 获得相同的输出？

Answer 1

fgets() 保留结束行 '\n' 而 gets() 不保留。然后比较失败。 @user3121023添加代码以消除潜在的结束行。

if (fgets(qTwo, sizeof qTwo, stdin) == NULL) Handle_EOF();
qTwo[strcspn(qTwo, "\n")] = 0;

Removing trailing newline character from fgets() input

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[编辑]

备注@Keith Thompson上面关于输入行过长的评论。