C - %x 格式说明符 [英] C - The %x format specifier

问题描述

我有一个小问题.我知道 %x 格式说明符可用于在格式字符串攻击中从堆栈中读取值.

I have a small question. I know that the %x format specifier can be used to read values from the stack in a format string attack.

我找到了以下代码:

%08x%08x%08x%08x

08 是什么意思?它到底在做什么?谢谢:)

What does the 08 mean? What is it doing exactly? Thanks :)

推荐答案

故障:

• 8 表示要显示8位数字
• 0 你想用 0 的前缀而不是空格
• x 要以小写十六进制打印.

• 8 says that you want to show 8 digits
• 0 that you want to prefix with 0's instead of just blank spaces
• x that you want to print in lower-case hexadecimal.

快速示例(感谢 Grijesh Chauhan):

Quick example (thanks to Grijesh Chauhan):

#include <stdio.h>
int main() {
    int data = 29;
    printf("%x
", data);    // just print data
    printf("%0x
", data);   // just print data ('0' on its own has no effect)
    printf("%8x
", data);   // print in 8 width and pad with blank spaces
    printf("%08x
", data);  // print in 8 width and pad with 0's

    return 0;
}

输出:

1d
1d
      1d
0000001d

另请参阅 http://www.cplusplus.com/reference/cstdio/printf/ 以供参考.

Also see http://www.cplusplus.com/reference/cstdio/printf/ for reference.

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