如何在C中通过命令行接受md5sum？

typedef union
{
    uint ui[4];
} md5hash;

void main(void)
{
    int opt;

    while ((opt = getopt(argc, argv, "c:t:s:h:")) != -1) {
        switch (opt) {
        case 'h':
            hash = optarg;
            break;
        default: /* '?' */
            exit(EXIT_FAILURE);
        }
    }

    md5hash hash;

    sscanf(hash, "%x%x%x%x", &hash.ui);
}

./program -h ffffffffffffffffffffffffffffffff

./program -h fffffffffffffffffffffffffffffffff

I want to do the above, but sscanf does not accept the md5sum properly...

我想做上面的事情,但是sscanf不能正确地接受md5sum ......

2 个解决方案

#1

You seem to have two variables called hash, except one is implicit in your code.

您似乎有两个名为hash的变量,除了一个隐含在您的代码中。

The sscanf statement attempts to read hash back into itself, but obviously it will not find any hexadecimal digits.

sscanf语句尝试将哈希读回自身,但显然它不会找到任何十六进制数字。

%x may load a different sized integer in hexadecimal on different platforms because you have not specified any specific length to read for each field.

%x可能会在不同平台上以十六进制加载不同大小的整数,因为您没有为每个字段指定任何特定长度。

You are not taking into account machine endianness.

您没有考虑机器字节序。

If you do have a hexadecimal string, let's say in hashString then you can probably try

如果你有一个十六进制字符串,让我们说在hashString然后你可以尝试

int fieldsScanned = sscanf (hashString, "%8x%8x%8x%8x", &hash.ui[0], &hash.ui[1], &hash.ui[2], &hash.ui[3]);

if (fieldsScanned == 4)
{
    // MD5 sum is in hash variable.
}

#2

int
parse_hex(char *s, unsigned char *hex, int len)
{
  int i, r = 0;

  len *= 2;
  for (i = 0; ; i++, s++)
    {
      if (*s == 0 && !(i & 1))
        return i / 2;
      if (i == len)
        {
          fprintf(stderr, "parsehex: string too long\n");
          //exit(1);
        }
      if (*s >= '0' && *s <= '9')
        r = (r << 4) | (*s - '0');
      else if (*s >= 'a' && *s <= 'f')
        r = (r << 4) | (*s - ('a' - 10));
      else if (*s >= 'A' && *s <= 'F')
        r = (r << 4) | (*s - ('a' - 10));
      else
        {
          fprintf(stderr, "parsehex: bad string\n");
          //exit(1);
        }
      if ((i & 1) != 0)
        {
          hex[i / 2] = r;
          r = 0;
        }
    }
}

void
parse_md5(char *s, unsigned char *md5)
{
  if (!*s)
    {
      memset(md5, 0, 16);
      return;
    }
  if (parse_hex(s, md5, 16) != 16)
    {
      fprintf(stderr, "parsemd5: bad md5\n");
      //exit(1);
    }
}

actually, the sscanf() method above does not work, it reads the bytes in reverse order within the doublewords.

实际上,上面的sscanf()方法不起作用,它在双字内以相反的顺序读取字节。

#1

You seem to have two variables called hash, except one is implicit in your code.