当用户在保持 float 变量的 scanf 中输入字符串时出错

Question

我现在正在练习c编程，我做了一些BMI计算器。它工作得很好，但是当用户在第一个 scanf 上输入字符串或字符时，将数据发送到浮点变量 'weight' 。之后它通过了所有 scanf 并向我显示错误 Your BMI is 1.#J 。如何解决这个错误？这是我的代码。

#include <stdio.h>

int main()
{
  float weight;
  float height;
  float result;
  float c_height;

  printf("Enter your weight as kilogram...\n\n> ");
  scanf("%f",&weight);
  //If user input char or string , it passed all thing and showed error.

  printf("\nEnter your height as centimetres...\n\n> ");
  scanf("%f",&height);

  c_height=(height/100)*(height/100);
  result=weight/c_height;

  if(result<18.50)
  {
    printf("\nYour BMI is %.2f\n\n",result);
    printf("You are underweight! Try to eat more frequently\n\n");
    printf("Thank you for using my program!\n\n");

}else if(result>=18.50 && result<22.90)
{
    printf("\nYour BMI is %.2f\n\n",result);
    printf("You are healthy! Keep eating healthy\n\n");
    printf("Thank you for using my program!\n\n");

}else if(result>=22.90 && result<24.90)
{
    printf("\nYour BMI is %.2f\n\n",result);
    printf("You are a little overweight! Avoid eating some fat and an oil\n\n");
    printf("Thank you for using my program!\n\n");

}else if(result>=24.90 && result<29.90)
{
    printf("\nYour BMI is %.2f\n\n",result);
    printf("You are overweight! Avoid eating fat and do exercise often\n\n");
    printf("Thank you for using my program!\n\n");

}else if(result>=29.90)
{
    printf("\nYour BMI is %.2f\n\n",result);
    printf("You are obese! Do exercise everyday and eat carefully!\n\n");
    printf("Thank you for using my program!\n\n");

}else
{
    printf("Error occured!!");
}
return 0;

}

Answer 1

scanf 将 return 读入的值的数量，因此在您的示例中应该是一个，因为您正在读取单个浮点值。

您可以检查 scanf returns 那个值，如果它没有进行某种恢复，例如读取到行尾：

while(scanf("%f",&height) != 1)
{
  int c;
  while((c = getchar()) != '\n' && c != EOF)
    ;
  printf("Enter your weight as kilogram...\n\n> ");
}

Answer 2

要传递给下一个参数，请在 scanf 之后添加一个 fflush(stdin) :

scanf("%f",&weight);

  fflush(stdin);

并且您需要像这样控制输入：

if (scanf("%lf", &weight) == 1)
    printf("It's float: %f\n", weight);
else
    printf("It's NOT float ... \n");

当用户在保持 float 变量的 scanf 中输入字符串时出错

Get error when user has input a string in a scanf that keep float variable

c

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