scanf函数获取跳过

问题描述

我试图做一个简单的C程序一类的要求之一就是我需要使用 scanf函数 / 的printf 所有输入和输出。我的问题是为什么是我 scanf函数

I am trying to make a simple C program for a class and one of the requirements is that I'm required to use scanf/printf for all input and output. My question is why is it that my scanf after the for loop in the main gets skipped and the program just terminates.

下面是我的code

#include <stdio.h>

void main() {
    int userValue;
    int x;
    char c;

    printf("Enter a number : ");
    scanf("%d", &userValue);
    printf("The odd prime values are:\n");
    for (x = 3; x <= userValue; x = x + 2) {
        int a;
        a = isPrime(x);
        if (a = 1) {
            printf("%d is an odd prime\n", x);
        }
    }
    printf("hit anything to terminate...");
    scanf("%c", &c);
}

int isPrime(int number) {
    int i;
    for (i = 2; i < number; i++) {
        if (number % i == 0 && i != number)
            return 0;
    }
    return 1;
}

我能够加入另一个相同的修理它 scanf函数后的第一个，但我会preFER只使用一个。

I was able to "fix" it by adding another identical scanf after the first one, but I would prefer to just use the one.

推荐答案

新的行字符present在标准输入的previous后 INT 被输入不会被最后调用消耗 scanf（）的。因此调用 scanf（）的的为循环消耗换行字符，并继续无需用户后，输入任何东西。

The new-line character present in stdin after the previous int was entered will not have been consumed by the last call to scanf(). So the call to scanf() after the for loop consumes the new-line character and continues without the user having to enter anything.

要纠正，而无需添加其他 scanf（）的调用，您可以使用格式说明％C中在 scanf（）的在为循环。这将使 scanf（）的跳过任何前导空白字符（包括新行）。注意这意味着用户必须输入大于新行以结束该程序以外的东西。

To correct without having to add another scanf() call you could use format specifier " %c" in the scanf() after the for loop. This will make scanf() skip any leading whitespace characters (including new-line). Note it means the user will have to enter something other than a new-line to end the program.

此外：

• 检查的结果 scanf（）的，以确保它实际上分配一个值传递的变量：

• check the result of scanf() to ensure it actually assigns a value to the variables passed in:

/* scanf() returns number of assigments made. */
if (scanf("%d", &userValue) == 1)




这是一个任务（而且将永远是真实的）：

this is an assignment (and will always be true):

if (a = 1){ /* Use == for equality check.
               Note 'a' could be removed entirely and
               replace with: if (isPrime(x)) */

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