c - 通过从 char * 转换为 int 进行整数验证

Question

假设我有一个无效的整数输入到 char * 其中，

char *ch = "23 45"

使用atoi(ch)给出23作为转换后的输出，忽略空格和45。

我正在尝试对此输入进行测试。我该怎么做才能将其标记为无效输入？

Answer 1

要么在将字符串传递给 atoi() 之前检查字符串，要么使用 strtol()，尽管后者将返回 long int。

使用strtol()，您可以检查错误:

RETURN VALUE
       The strtol() function returns the result of the conversion, unless the value would underflow or overflow.  If an underflow occurs, strtol() returns LONG_MIN.  If an overflow
       occurs,  strtol()  returns  LONG_MAX.   In  both cases, errno is set to ERANGE.  Precisely the same holds for strtoll() (with LLONG_MIN and LLONG_MAX instead of LONG_MIN and
       LONG_MAX).

ERRORS
       EINVAL (not in C99) The given base contains an unsupported value.

       ERANGE The resulting value was out of range.

       The implementation may also set errno to EINVAL in case no conversion was performed (no digits seen, and 0 returned).