linux 获取网卡的IP地址

下面这段代码的作用是根据传入的网卡名称获取相对应的本地IP地址，之前获取的本地网络地址老是127.0.0.1下面的获取的是正确的局域网地址

char* hostname_to_ip(char * ifaName ){
        struct ifaddrs *ifaddr, *ifa;
       int family, s;
       char host[NI_MAXHOST];
        std::string str;
       if (getifaddrs(&ifaddr) == -1)
       {
       //    perror("getifaddrs");
           //exit(EXIT_FAILURE);
       }

       for (ifa = ifaddr; ifa != NULL; ifa = ifa->ifa_next)
       {
           if (ifa->ifa_addr == NULL)
               continue;
           s=getnameinfo(ifa->ifa_addr,sizeof(struct sockaddr_in),host, NI_MAXHOST, NULL, 0, NI_NUMERICHOST);

           if((strcmp(ifa->ifa_name,ifaName)==0)&&(ifa->ifa_addr->sa_family==AF_INET))
           {
               if (s != 0)
               {
                 //  printf("getnameinfo() failed: %s\n", gai_strerror(s));
                   //exit(EXIT_FAILURE);
               }
               freeifaddrs(ifaddr);
                return host;
               //printf("\tInterface : <%s>\n",ifa->ifa_name );
               //printf("\t  Address : <%s>\n", host);
           }
       }
}