linux c语言 获取网关

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

void get_gateway(char *gateway_ip, size_t size) {
    FILE *fp;
    char line[256];
    char *token;

    fp = popen("ip route show default", "r");
    if (fp == NULL) {
        perror("popen");
        return;
    }

    while (fgets(line, sizeof(line), fp)) {
        token = strtok(line, " ");
        while (token != NULL) {
            if (strcmp(token, "via") == 0) {
                token = strtok(NULL, " ");
                if (token != NULL) {
                    strncpy(gateway_ip, token, size - 1);
                    gateway_ip[size - 1] = '\0';
                    break;
                }
            }
            token = strtok(NULL, " ");
        }
        if (gateway_ip[0] != '\0') {
            break;
        }
    }

    pclose(fp);
}

int main() {
    char gateway_ip[16]; // IPv4 address is up to 15 characters + null terminator
    get_gateway(gateway_ip, sizeof(gateway_ip));
    printf("Default Gateway: %s\n", gateway_ip);
    return 0;
}