用C++写一个获取本地IP

在 C 语言中，可以使用 socket 函数库获取本地 IP 地址。

以下是一个简单的代码示例：

#include <stdio.h>
#include <string.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netdb.h>
#include <arpa/inet.h>
#include <netinet/in.h>

int main() {
    int status;
    struct addrinfo hints;
    struct addrinfo *servinfo;  // will point to the results
    char ipstr[INET6_ADDRSTRLEN];

    memset(&hints, 0, sizeof hints); // make sure the struct is empty
    hints.ai_family = AF_UNSPEC;     // don't care IPv4 or IPv6
    hints.ai_socktype = SOCK_STREAM; // TCP stream sockets

    if ((status = getaddrinfo("www.google.com", NULL, &hints, &servinfo)) != 0) {
        fprintf(stderr, "getaddrinfo error: %s\n", gai_strerror(status));
        return 1;
    }

    struct addrinfo *p;
    for (p = servinfo; p != NULL; p = p->ai_next) {
        void *addr;
        char *ipver;

        // get the pointer to the address itself,
        // different fields in IPv4 and IPv6:
        if (p->ai_family == AF_INET) { // IPv4
            struct sockaddr_in *ipv4 = (struct sockaddr_in *)p->ai_addr;
            addr = &(ipv4->sin_addr);
            ipver = "IPv4";
        } else { // IPv6
            struct sockaddr_in6 *ipv6 = (struct sockaddr_in6 *)p->ai_addr;
            addr = &(ipv6->sin6_addr);
            ipver = "IPv6";
        }

        // convert the IP to a string and print it:
        inet_ntop(p->ai_family, addr, ipstr, sizeof ipstr);
        printf("%s: %s\n", ipver, ipstr);
    }

    freeaddrinfo(servinfo); // free the linked-list

    return 0;
}

该代码通过获取 `www.google.com` 的 IP 地址来展示如何使用 `getaddrinfo` 函数。如果要获取本地 IP 地址，请将主机名替换为 `localhost` 或 `127.0.0.1`。