c语言域名函数

#include <stdio.h>
#include <stdlib.h>
#include <netdb.h>
#include <arpa/inet.h>

int main(int argc, char *argv[]) {
    if (argc != 2) {
        fprintf(stderr, "Usage: %s hostname\n", argv[0]);
        exit(EXIT_FAILURE);
    }

    struct hostent *host = gethostbyname(argv[1]);
    if (host == NULL) {
        perror("gethostbyname");
        exit(EXIT_FAILURE);
    }

    struct in_addr **addr_list = (struct in_addr **)host->h_addr_list;
    for (int i = 0; addr_list[i] != NULL; i++) {
        printf("IP address: %s\n", inet_ntoa(*addr_list[i]));
    }

    return 0;
}

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

void print_addrinfo(struct addrinfo *ai) {
    struct sockaddr_in *ipv4;
    char ipstr[INET_ADDRSTRLEN];

    while (ai != NULL) {
        switch (ai->ai_family) {
            case AF_INET:
                ipv4 = (struct sockaddr_in *)ai->ai_addr;
                inet_ntop(AF_INET, &(ipv4->sin_addr), ipstr, sizeof(ipstr));
                printf("IPv4 address: %s\n", ipstr);
                break;
            // 可以添加对IPv6的支持
            default:
                fprintf(stderr, "Unsupported address family\n");
                break;
        }
        ai = ai->ai_next;
    }
}

int main(int argc, char *argv[]) {
    if (argc != 2) {
        fprintf(stderr, "Usage: %s hostname\n", argv[0]);
        exit(EXIT_FAILURE);
    }

    struct addrinfo hints, *res, *p;
    int status;
    char ipstr[INET6_ADDRSTRLEN];

    memset(&hints, 0, sizeof hints);
    hints.ai_family = AF_UNSPEC; // AF_INET or AF_INET6 to force version
    hints.ai_socktype = SOCK_STREAM;

    if ((status = getaddrinfo(argv[1], NULL, &hints, &res)) != 0) {
        fprintf(stderr, "getaddrinfo: %s\n", gai_strerror(status));
        exit(EXIT_FAILURE);
    }

    print_addrinfo(res);

    freeaddrinfo(res); // free the linked list

    return 0;
}