C中scanf函数的格式说明符中％c规范之前的空格 [英] Whitespace before %c specification in the format specifier of scanf function in C

问题描述

当我在％d 和％c 规范之间不包括空格时， scanf（）函数在以下程序中运行，并在运行时输入 4 h，则输出为 Integer = 4 and Character =。

When I don't include white space between %d and %c specification in the format string of scanf() function in the following program, and give input during run-time as "4 h", then the output is "Integer = 4 and Character= .

在这种情况下，变量 c 到底有多精确？如果我在％d 和％c 规范？

How exactly variable "c" takes the input in this case and what difference does it make if i include a white space between %d and %c specification ?

代码

Code

#include <stdio.h>

int main()
{
    char c;
    int i;
    printf("Enter an Integer and a character:\n");
    scanf("%d %c",&i,&c);
    printf("Integer = %d and Character = %c\n",i,c);
    getch();
} 

推荐答案

如果阅读了规范对于 scanf（） 会很小心，大多数格式说明符会跳过前导空格。在标准C中，有三个没有：

If you read the specification for scanf() carefully, most format specifiers skip leading white space. In Standard C, there are three that do not:

• ％n 到目前为止，已经处理了许多字符


• ％[…] —扫描集


• ％c —读一个字符。

• %n — how many characters have been processed up to this point
• %[…] — scan sets
• %c — read a character.

（POSIX添加了第四个， ％C ，相当于％lc 。）

(POSIX adds a fourth, %C, which is equivalent to %lc.)

输入的空白​​字符（由 isspace 指定）将被跳过，除非转换规范中包含 [ ， c ， C 或 n 转换说明符。

Input white-space characters (as specified by isspace) shall be skipped, unless the conversion specification includes a [, c, C, or n conversion specifier.

在％d 和％c 表示在读取整数之后且在读取（不是空白）字符之前跳过了可选的空白。

Adding the space between %d and %c means that optional white space is skipped after the integer is read and before the (not white space) character is read.

请注意，格式字符串中的文字字符（空格除外），例如 X 和 Y 在 X％dY 中）不要跳过空白。匹配这些字符也不算是成功的转换。它们不会影响 scanf（）等的返回值。

Note that literal characters in a format string (other than white space — for example, the X and Y in "X%dY") do not skip white space. Matching such characters does not count as a successful conversion either; they do not affect the return value from scanf() et al.

这篇关于C中scanf函数的格式说明符中％c规范之前的空格的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！