C：多scanf函数的，当我在一个scanf函数的值输入跳过第二scanf函数 [英] C: Multiple scanf's, when I enter in a value for one scanf it skips the second scanf

问题描述

我有code（省略的逻辑功能是家庭作业的一部分）的此块：

I have this block of code (functions omitted as the logic is part of a homework assignment):

#include <stdio.h>

int main()
{
    char c = 'q';
    int size; 

    printf("\nShape (l/s/t):");
    scanf("%c",&c);

    printf("Length:"); 
    scanf("%d",&size);

    while(c!='q')
    {
        switch(c)
        {
            case 'l': line(size); break; 
            case 's': square(size); break;
            case 't': triangle(size); break; 
        }


        printf("\nShape (l/s/t):");
        scanf("%c",&c);

        printf("\nLength:"); 
        scanf("%d",&size);
    }

    return 0; 
}

前两个scanf函数的工作很好，没有任何问题，一旦我们进入while循环，我在哪里，你都应该被提示输入一个新的形状字符时出了问题，而是跳下来的的printf ，并等待接受输入从那里为一个字符，后来小数环路的下一次迭代。

The first two Scanf's work great, no problem once we get into the while loop, I have a problem where, when you are supposed to be prompted to enter a new shape char, it instead jumps down to the printf of Length and waits to take input from there for a char, then later a decimal on the next iteration of the loop.

preloop迭代：

Preloop iteration:

scanf函数：形状。伟大的工程结果
scanf函数：长度。没有问题

Scanf: Shape. Works Great
Scanf: Length. No Problem

1，循环

scanf函数：形状。跳过这一结果
scanf函数：长度。问题，这scanf函数映射到形状字符。

Scanf: Shape. Skips over this
Scanf: length. Problem, this scanf maps to the shape char.

回路2结果
scanf函数：形状。跳过这一结果
scanf函数：长度。的问题，这个现在scanf函数映射到大小INT。

Loop 2
Scanf: Shape. Skips over this
Scanf: length. Problem, this scanf maps to the size int now.

为什么这样做呢？

推荐答案

scanf函数（％C）读取来自换行符<大骨节病> ENTER 键。

当你键入假设 15 ，您键入 1 ，一个 5 然后preSS的<大骨节病> ENTER 键。所以现在有在输入缓冲区中三个字符。 scanf函数（％D）读 1 和 5 ，除preting他们作为数 15 ，但换行符仍然在输入缓冲区。在 scanf函数（％C）将立即读这换行符，然后程序将进入下一个 scanf函数（％d个 ），并等待你输入一个号码。

When you type let's say 15, you type a 1, a 5 and then press the ENTER key. So there are now three characters in the input buffer. scanf("%d") reads the 1 and the 5, interpreting them as the number 15, but the newline character is still in the input buffer. The scanf("%c") will immediately read this newline character, and the program will then go on to the next scanf("%d"), and wait for you to enter a number.

通常的建议是读取输入的整行以与fgets ，和跨preT每行的一个单独的步骤中的内容。一个简单的办法，以你的眼前的问题是添加的getchar（）之后每个 scanf函数（％D）。

The usual advice is to read entire lines of input with fgets, and interpret the content of each line in a separate step. A simpler solution to your immediate problem is to add a getchar() after each scanf("%d").

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