c - 如何阻止我的代码使用 scanf 生成无限循环？

Question

这是一个从 main 调用的函数。如何让这段代码检查字母输入，并在检测到输入不是整数时进入 while 循环？谢谢

int time1(void)
{
    int hour;

        printf("Enter the hour: ");
        scanf("%d", &hour);

            while (hour > MAX_HOUR || hour < MIN_HOUR) 
            {
                printf("Invalid hour input. Please enter an hour between 1 and 12: ");
                scanf("%d", &hour);
            }

            return hour;
}

Answer 1

测试是否成功:

hour = -1;   // So you can detect afterwards if they never succeeded at all

while ( 1 == scanf("%d", &hour) )
{
    if ( hour >= MIN_HOUR && hour <= MAX_HOUR )
         break;

    printf("Invalid hour input, try again...");
}

例如，如果他们输入 "hello"，该版本就会中断。如果你想在他们输入垃圾后继续询问他们，那么你必须从流中清除所有垃圾，例如:

for (;;)
{
    int result = scanf("%d", &hour);

    if ( result == EOF )
    {
        hour = -1;
        break;
    }

    if ( result != 1 )
    {
    // consume garbage which will end in a newline
        for (int ch; (ch = getchar()) != EOF && ch != '\n'; ) {}
        continue;
    }

    if ( hour >= MIN_HOUR && hour <= MAX_HOUR )
         break;

    printf("Invalid hour input, try again...");
}

在 C 中做健壮的流输入并不简单!