有什么scanf函数之间的差异（QUOT;％D＆QUOT;）和scanf（QUOT;％D＆QUOT;）？

问题描述：

#include <stdio.h>

int main(void)
{
    int i, j;

    printf("enter a value for j ");
    scanf("%d  ",&j);
    printf("j is %d \n", j);
    printf("enter a value for i ");
    scanf("%d",&i);
    printf("i is %d \n", i);
    return 0;
}

如何在 scanf（）的函数实际上，当我的格式说明像 scanf函数（％D之后添加空格，与放工作;Ĵ ）;

How does the scanf() function actually work when I add spaces after the format specifier like scanf("%d ",&j);?

答

在scanf格式空格字符，使其明确地阅读，而忽略尽可能多的空白字符，因为它可以。因此，与 scanf函数（％d个，... ，读了许多之后，它将继续读取字符，丢弃所有空白，直到它看到一个非空白字符输入，即非空白字符将被留作为下一个字符由一个的输入功能来读取。

A whitespace character in a scanf format causes it to explicitly read and ignore as many whitespace characters as it can. So with scanf("%d ", ..., after reading a number, it will continue to read characters, discarding all whitespace until it sees a non-whitespace character on the input. That non-whitespace character will be left as the next character to be read by an input function.

通过您的code：

printf("enter a value for j ");

scanf("%d  ",&j);

printf("j is %d \n", j);

将打印的第一行，然后等待你输入一个数字，然后的后继续的数量要等待的东西。所以，如果你只需要输入 5 骨节病> 输入骨节病>，它会出现挂 - 你需要输入一些非空白字符它继续另一条线。如果然后键入 6 骨节病> 输入骨节病>，这将成为 i的值，让你的屏幕看起来是这样的：

it will print the first line and then wait for you to enter a number, and then continue to wait for something after the number. So if you just type 5Enter, it will appear to hang — you need to type in another line with some non-whitespace character on it to continue. If you then type 6Enter, that will become the value for i, so your screen will look something like:

enter a value for j 5
6
j is 5
enter a value for i i is 6

此外，由于大多数scanf函数％-conversions也跳过前导空白（所有除了％C ，％[和％N ），空格的前的％-conversions是无关的（％D和％D将相同的行为）。因此，在大多数情况下，你应该避免在scanf中的转换空间，除非你知道你特别需要他们的奇特效果。

Also, since most scanf %-conversions also skip leading whitespace (all except for %c, %[ and %n), spaces before %-conversions are irrelevant ("%d" and " %d" will act identically). So for the most part, you should avoid spaces in scanf conversions unless you know you specifically need them for their peculiar effect.

有什么scanf函数之间的差异（QUOT;％D＆QUOT;）和scanf（QUOT;％D＆QUOT;）？

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