Linux C获取本机IP

方法1

#include 
#include 
#include 
#include 
#include 
#include 
#include 

int
main(int argc, char *argv[])
{
    struct ifaddrs *ifaddr, *ifa;
    int family, s;
    char host[NI_MAXHOST];

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

    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)
        {
            printf("interfac: %s, ip: %s\n", ifa->ifa_name, inet_ntoa(((struct sockaddr_in*)ifa->ifa_addr)->sin_addr));
        }
   }

   freeifaddrs(ifaddr);
   exit(EXIT_SUCCESS);
}
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如果时使用pppoe拨号上网的方式, 是获取到不到IP的, 可以获取到相应名字的ifaddrs结构体,但是结构体中的ifa_addr是NULL

#include 
#include 
#include 
#include 
#include 
#include  
#include  
#include   
#include   
#include  
#include   
#include   
#include  
// 获取本机ip  eth_inf网卡名称 调用方法get_local_ip("apcli0", ip);
int get_local_ip(const char *eth_inf)
{
    int sd;
    struct sockaddr_in sin;
    struct ifreq ifr;
 
    sd = socket(AF_INET, SOCK_DGRAM, 0);
    if (-1 == sd)
    {
        printf("socket error: %s\n", strerror(errno));
        return -1;
    }
 
    strncpy(ifr.ifr_name, eth_inf, IFNAMSIZ);
    ifr.ifr_name[IFNAMSIZ - 1] = 0;
 
    // if error: No such device  
    if (ioctl(sd, SIOCGIFADDR, &ifr) < 0)
    {
        printf("ioctl error: %s\n", strerror(errno));
        close(sd);
        return -1;
    }
    
    printf("interfac: %s, ip: %s\n", eth_inf, inet_ntoa(((struct sockaddr_in*)&ifr.ifr_addr)->sin_addr)); 

    close(sd);
    return 0;
}

int main(int argc, const char *argv[])
{
    get_local_ip(argv[1]);
    return 0;
}
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该种方式不存在上一个的问题