c - scanf 和输入字符

Question

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已关闭 10 年前。

我想知道如果在我的程序中我要求使用 scanf("%d",&num) 进行整数输入，会发生什么情况？用户输入一串字符和整数，例如 at3stf0rfun 。num 的值是多少在这种情况下？是否只需要整数 30或者它是否也将字符转换为其 ASCII 十进制值？

Answer 1

扫描在遇到无效输入时停止。因此，在您的代码中，num 的值将保持不变。

要检测是否发生了这种情况，您需要检查 scanf 的返回值。引用 man scanf:

RETURN VALUES

These functions return the number of input items assigned. This can be fewer than provided for, or even zero, in the event of a matching failure. Zero indicates that, although there was input available, no conversions were assigned; typically this is due to an invalid input character, such as an alphabetic character for a `%d' conversion. The value EOF is returned if an input failure occurs before any conversion such as an end-of-file occurs. If an error or end-of-file occurs after conversion has begun, the number of conversions which were successfully completed is returned.