为什么sscanf在这段代码中效果不好？

#include <stdio.h>

int main()
{
    char string[80]="abcdef";
    char buffer[80];
    int num;
    sscanf(string,"%*[^0-9a-fA-F]%n%s",&num,buffer);
    printf("%d\n",num);
    puts(buffer);
    return 0;
}

Output:

输出：

-149278720

And what I expect is

而我的期望是

0
abcdef

I believe that the regex %*[^0-9a-fA-F] discards all characters other than "xdigits", however, when the first character in the string is a "xdigit", sscanf seems to return instantly.

我相信正则表达式％* [^ 0-9a-fA-F]丢弃除“xdigits”之外的所有字符，但是，当字符串中的第一个字符是“xdigit”时，sscanf似乎立即返回。

How can I fix this?

我怎样才能解决这个问题？

1 个解决方案

#1

%*[^0-9a-fA-F] matches a non-empty sequence of characters that aren't in the character set. Since you don't have any non-hexdigits at the beginning of the string, this conversion fails and sscanf returns immediately.

％* [^ 0-9a-fA-F]匹配不在字符集中的非空字符序列。由于您在字符串的开头没有任何非hexdigits，因此此转换失败并且sscanf立即返回。

As far as I can tell, there's no way to make this optional in sscanf. If you just want to skip over the non-hexdigits, use strcspn().

据我所知，没有办法在sscanf中使这个可选。如果您只想跳过非hexdigits，请使用strcspn（）。

num = strcspn(string, "0123456789abcdefABCDEF");
strcpy(buf, string+num);