为什么我的 integer 在 C 中打印不正确

Question

我只是想写一些需要一个月和日期的东西，然后打印出来。 我写了以下代码：

int main(void){
    char month[] = {};
    int day;
    printf("Please enter the month and day of you date. i.e January 01\n\n");
    scanf("%s,%d", month, &day);
    printf("Month is %s and the day is %d\n", month, day);
    return 0;
} 

当我输入像 12 月 22 日这样的日期时，我得到以下打印输出：月份是 12 月，日期是 1。日期值打印为 1。为什么我的日期 integer 没有更新，而是停留在 1？

Answer 1

本声明

char month[] = {};

在 C 和 C++ 中无效。

至少你应该写例如

char month[10];

在提示中，输入日期的格式不带逗号

printf("Please enter the month and day of you date. i.e January 01\n\n");

但是在scanf的调用中

scanf("%s,%d", month, &day);

现在有一个逗号。

该程序可以通过以下方式查找示例

#include <stdio.h>

int main( void )
{
    char month[10];
    unsigned int day;

    printf( "Please enter the month and day of you date. i.e January 01\n\n" );

    if (scanf( "%9s %u", month, &day ) == 2)
    {
        printf( "Month is %s and the day is %02u\n", month, day );
    }
}

程序 output 可能看起来像

Please enter the month and day of you date. i.e January 01

December 22
Month is December and the day is 22

如果你想在输入字符串中包含一个逗号，那么程序可以像下面这样

#included <stdio.h>

int main( void )
{
    char month[10];
    unsigned int day;

    printf( "Please enter the month and day of you date. i.e January, 01\n\n" );

    if (scanf( "%9[^,], %u", month, &day ) == 2)
    {
        printf( "Month is %s and the day is %02u\n", month, day );
    }
}

程序 output 可能看起来像

Please enter the month and day of you date. i.e January, 01

January, 01
Month is January and the day is 01

另一种方法是使用 function fgets而不是scanf例如

#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <string.h>

int main( void )
{
    char date[14];

    printf( "Please enter the month and day of you date. i.e January, 01\n\n" );

    int success = fgets( date, sizeof( date ), stdin ) != NULL;

    if (success)
    {
        const char *p = strchr( date, ',' );

        if (success = p != NULL)
        {
            char *endptr;

            unsigned int day = strtoul( p + 1, &endptr, 10 );

            if ( success = endptr != p + 1 )
            {
                printf( "Month is %.*s and the day is %02u\n", 
                    ( int )( p - date ), date, day );
            }
        }
    }
}

程序 output 可能看起来像

Please enter the month and day of you date. i.e January, 01

January, 01
Month is January and the day is 01