简单的 C 程序不返回任何输出

Question

我编写了一个简单的 C 程序，它接受用户输入并将其存储在 dataofUser 变量中，然后它允许用户通过说是或否来选择是否要显示他们输入的数据，这是通过 fgets 和 a if 语句检查 userChoice 变量中是否存储了是或否，具体取决于它是或否，它将显示数据或显示“无输出！”，当我运行程序时，我没有得到我在下面输入的数据的输出您可以看到控制台上显示的内容：

Please enter your input: this is a random input
Your data has been entered please enter Yes or No to display it: yes

Process returned 0 (0x0)    execution time : 4.829 s
Press ENTER to continue.

这是构建消息日志和各种错误消息

||=== Build: Debug in randopoint2 (compiler: GNU GCC Compiler) ===|
/home/Documents/randopoint2/randopoint2/main.c||In function ‘main’:|
/home/Documents/randopoint2/randopoint2/main.c|17|warning: comparison between pointer and integer|
/home/Documents/randopoint2/randopoint2/main.c|17|warning: comparison with string literal results in unspecified behavior [-Waddress]|
/home/Documents/randopoint2/randopoint2/main.c|21|warning: comparison between pointer and integer|
/home/Documents/randopoint2/randopoint2/main.c|21|warning: comparison with string literal results in unspecified behavior [-Waddress]|
||=== Build finished: 0 error(s), 4 warning(s) (0 minute(s), 0 second(s)) ===|
||=== Run: Debug in randopoint2 (compiler: GNU GCC Compiler) ===|

#include <stdio.h>
#include <stdlib.h>

int main()
{
    char dataOfUser[50];
   char userChoice[50];

  printf("Please enter your input: ");
  fgets(dataOfUser, 50, stdin);

  printf("Your data has been entered please enter Yes or No to dipslay it: ");
  fgets(userChoice, 50, stdin);


  if(userChoice[50] == "yes")
  {
  printf("Your notes are: %s", dataOfUser);
  }
  else if(userChoice[50] == "no")
  {
  printf("no output!");
  }

    return 0;
}

Answer 1

问题：

if(userChoice[50] == "yes")

这不是 C 中比较字符串的方式。

此外，访问userChoice[50] 是未定义的行为，因为您正试图访问超出其边界的数组。

else if(userChoice[50] == "no") 也是如此

另请注意，当您按 Enter 键结束输入时，换行符 \n 存储在 userChoice 中。

解决方案：

1. 添加#include <string.h>得到strcmp函数。

2. 将if(userChoice[50] == "yes") 更改为if (strcmp(userChoice, "yes\n") == 0)

3. 将else if(userChoice[50] == "no")更改为else if (strcmp(userChoice, "no\n") == 0)

旁白：

printf("Your data has been entered please enter Yes or No to dipslay it: ");

您要求用户输入“是”或“否”，但要与代码中的“是”和“否”进行比较。