c - 如何使用 scanf 获取包含空格的输入

Question

我是 C 新手，这是我一直感到困惑的事情假设我有这样的代码我只想使用 char

    char a, b, c;
    printf("input first character: ");
    scanf(" %c", &a);
    printf("input second character: ");
    scanf(" %c", &b);
    printf("input thrid character: ");
    scanf(" %c", &c);

我多么希望也能在太空中阅读；我注意到这只能读取非空格字符，如果我想读取空格以及像这样的 c=' '; 该怎么办？我如何扫描这个空间；

现在通过听取使用 getchar() 的建议，我写了这个:

#include<stdio.h>

int main(void)
{
  char a,b,c;
printf("input the first char:");
a=getchar();
printf("input the second char:");
b=getchar();
printf("input the third char:");
c=getchar();
 return 0;


}

当我编译和运行程序时，怎么会发生奇怪的事情

程序输出是这样的

input the first char:
input the second char:input the third char:

现在它不再让我输入第二个字符，它最后直接跳到第三个请求，我只被要求输入 2 个输入，这很奇怪，因为程序在代码中明确要求输入 3 个。

现在这是我这样编写的程序，我将建议的内容添加到代码块中

int main(void)
{
    int totalHeight=0, floorWidth=0, amountOfStories, amountWindowForTop, amountWindowForMiddle, amountWindowForBottom, windowHeight, middleWindowWidth, topWindowWidth, bottomWindowWidth, minimumHeight, minimumWidth;
    int betweenDistanceTop, betweenDistanceMiddle, betweenDistanceBottom, edgeDistanceTop, edgeDistanceBottom, edgeDistanceMiddle;
    char topFloorWindowContent, middleFloorWindowContent, bottomFloorWindowContent, windowBorder, floorBorder;
    int tempMax, tempValue, tempSideDistance, tempBetweenDistance;
    printf("please enter how many stories your building would like to have: ");
    scanf("%d",&amountOfStories);
    minimumHeight=amountOfStories*6+1;
    while((totalHeight<minimumHeight)||((totalHeight%amountOfStories)!=1))
    {
        printf("please enter the totalHeight (minimum %d): ",minimumHeight);
        scanf("%d",&totalHeight);
    }
    printf("please enter how many window building would have for top floor: ");
    scanf("%d",&amountWindowForTop);
    printf("please enter how many window building would have for middle floors: ");
    scanf("%d",&amountWindowForMiddle);
    printf("please enter how many window building would have for bottom floor: ");
    scanf("%d",&amountWindowForBottom);
    tempMax=amountWindowForTop;
    if (tempMax<amountWindowForMiddle)
    {
        tempMax=amountWindowForMiddle;
    }
    if (tempMax<amountWindowForBottom)
    {
        tempMax=amountWindowForBottom;
    }
    while(floorWidth<tempMax)
    {
        printf("please enter the width of the building (Minimum %d): ",tempMax*4+1);
        scanf("%d",&floorWidth);
    }

    char a, b, c;


    printf("a:");
    a=getchar();getchar();
    printf("b:");
    b=getchar();getchar();
    printf("c:");
    c=getchar();
    printf("a=%c, b=%c, c=%c", a, b, c);
return 0;
}

现在有趣的部分是，如果我将这段代码放入大程序中，它不起作用，输出是这样的

please enter how many stories your building would like to have: 2
please enter the totalHeight (minimum 13): 2
please enter the totalHeight (minimum 13): 2
please enter the totalHeight (minimum 13): 13
please enter how many window building would have for top floor: 2
please enter how many window building would have for middle floors: 2
please enter how many window building would have for bottom floor: 2
please enter the width of the building (Minimum 9): 9
a:
b:*
c:a=
, b=
, c=

因为我们可以看到 a b c 全部读入\n 而不是空格 * 而 c 根本没有读到任何内容，这是为什么？

Answer 1

您的代码的问题是这样的:当您读取第一个字符(a)时，您按回车键(\n)插入下一个字符，所以现在在 stdin 上有一个您尚未阅读的 \n。当您尝试读取下一个字符 (b) 时，程序会从 stdin 读取前一个 \n，并且不允许您读取下一个字符。因此，当您使用 getchar() 读取字符，然后按键盘上的 Enter 键时，您需要第二个 getchar() 来删除 \n.这是可以解决您的问题的示例代码:

#include<stdio.h>

int main(void) {
  char a, b, c;

  printf("a:");
  a=getchar();getchar();
  printf("b:");
  b=getchar();getchar();
  printf("c:");
  c=getchar();
  printf("a=%c, b=%c, c=%c", a, b, c);
  return 0;
}

对于您发布的编辑内容，您需要在获取 a、b、c 的值之前放置所谓的“标准输入清洁器”:

while(getchar()!='\n');

它只是删除所有字符直到\n。请注意，当您发布的程序有大量来自键盘的输入时，有时您会遇到此问题，因为 stdin 中存在额外的字符。因此，这个问题的一般答案是尝试找出这些额外的字符(大多数情况下在某处有一个额外的 \n )可能在哪里，并使用像我提到的那样删除的函数，以便您可以继续从 stdin 读取。