linux c获取网关地址

ip route show default | awk '/default/ {print $3}'

route -n | grep 'UG[ \t]' | awk '{print $2}'

netstat -rn | grep '^default' | awk '{print $2}'

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

void get_gateway(char *gateway) {
    struct ifaddrs *ifaddr, *ifa;
    int family, s;
    char host[NI_MAXHOST];

    if (getifaddrs(&ifaddr) == -1) {
        perror("getifaddrs");
        return;
    }

    for (ifa = ifaddr; ifa != NULL; ifa = ifa->ifa_next) {
        if (ifa->ifa_addr == NULL)
            continue;

        family = ifa->ifa_addr->sa_family;

        if (family == AF_INET) {
            s = getnameinfo(ifa->ifa_addr, sizeof(struct sockaddr_in), host, NI_MAXHOST, NULL, 0, NI_NUMERICHOST);
            if (s != 0) {
                printf("getnameinfo() failed: %s\n", gai_strerror(s));
                continue;
            }

            if (strcmp(host, "0.0.0.0") == 0) {
                strcpy(gateway, inet_ntoa(((struct sockaddr_in *)ifa->ifa_dstaddr)->sin_addr));
                break;
            }
        }
    }

    freeifaddrs(ifaddr);
}

int main() {
    char gateway[16];
    get_gateway(gateway);
    printf("Gateway: %s\n", gateway);
    return 0;
}