C 编程 - 循环直到用户输入数字 scanf [英] C programming - Loop until user inputs number scanf

问题描述

我需要有关程序错误检查的帮助.我要求用户输入一个整数，我想检查用户输入是否为整数.如果没有，请重复扫描.

I need help with error checking for my program. I'm asking the user to input a integer and I would like to check if the users input is a integer. If not, repeat the scanf.

我的代码:

int main(void){

  int number1, number2;
  int sum;

  //asks user for integers to add
  printf("Please enter the first integer to add.");
  scanf("%d",&number1);

  printf("Please enter the second integer to add.");
  scanf("%d",&number2);
  //adds integers
  sum = number1 + number2;

  //prints sum
  printf("Sum of %d and %d = %d 
",number1, number2, sum);

  //checks if sum is divisable by 3
  if(sum%3 == 0){
    printf("The sum of these two integers is a multiple of 3!
");
  }else {
    printf("The sum of these two integers is not a multiple of 3...
");
  }
  return 0;
}

推荐答案

scanf 根据您的格式返回已成功读取的项目数.您可以设置一个循环，仅当 scanf("%d", &number2); 返回 1 时才退出.然而，诀窍是当 scanf 返回零时忽略无效数据，因此代码如下所示:

scanf returns the count of items that it has successfully read according to your format. You can set up a loop that exits only when scanf("%d", &number2); returns 1. The trick, however, is to ignore invalid data when scanf returns zero, so the code would look like this:

while (scanf("%d",&number2) != 1) {
    // Tell the user that the entry was invalid
    printf("You did not enter a valid number
");
    // Asterisk * tells scanf to read and ignore the value
    scanf("%*s");
}

由于您在代码中多次读取一个数字，请考虑创建一个函数来隐藏此循环，并在您的 main 中调用此函数两次以避免重复.

Since you read a number more than once in your code, consider making a function to hide this loop, and call this function twice in your main to avoid duplication.

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