C - 使用 sin_addr 获取 IP 地址字符串

Question

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Answer 1

稍微扩展你的代码以使其编译

#include <netinet/in.h>  
struct sockaddr_in clt;
int main() {
  char ip[30];
  strcpy(ip, (char*)inet_ntoa((struct in_addr)clt.sin_addr));
}

尝试在启用警告的情况下编译它(总是一个好主意)会给出一些警告，但肯定行不通

$ gcc -Wall -Wextra -O3 ntoa.c -o ntoa && ./ntoa
ntoa.c: In function 'main':
ntoa.c:5:3: warning: implicit declaration of function 'strcpy' [-Wimplicit-function-declaration]
ntoa.c:5:3: warning: incompatible implicit declaration of built-in function 'strcpy' [enabled by default]
ntoa.c:5:3: warning: implicit declaration of function 'inet_ntoa' [-Wimplicit-function-declaration]
ntoa.c:5:14: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast]
ntoa.c:6:1: warning: control reaches end of non-void function [-Wreturn-type]
Segmentation fault
$

在顶部包含缺少函数声明的 header (这也是一个好主意)

#include <arpa/inet.h>
#include <string.h>

显然修复了它:

$ gcc -Wall -Wextra -O3 ntoa.c -o ntoa && ./ntoa 
ntoa.c: In function 'main':
ntoa.c:8:1: warning: control reaches end of non-void function [-Wreturn-type]
$