linux 下获取本地IP地址

from:http://blog.csdn.net/wj4064/article/details/2553158

#include
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#include

int main(int argc, char *argv[])
{

    char ipbuf[16];
    getlocaip(ipbuf);

    printf("loca ip = %s/n", ipbuf);
    exit(0);

}

int getlocaip(char *ip)
{
    int sockfd;

    if(-1 == (sockfd = socket(PF_INET, SOCK_STREAM, 0)))
    {
        perror( "socket" );
        return -1;
    }

   struct ifreq req;
    struct sockaddr_in *host;
    bzero(&req, sizeof(struct ifreq));
    strcpy(req.ifr_name, "eth0");
    ioctl(sockfd, SIOCGIFADDR, &req);    //设置IP
    host = (struct sockaddr_in*)&req.ifr_addr;
    strcpy(ip, inet_ntoa(host->sin_addr));
    close(sockfd);
    return 1;
}

SIOCGSIZIFCONF	获得获取 SIOCGIFCONF 返回的所有接口的配置信息所需的内存。 ioctl(fd, SIOCGSIZIFCONF, (caddr_t)&ifconfsize); int ifconfsize;
SIOCGIFADDR SIOCSIFADDR	SIOCGIFADDR 获取接口地址，而 SIOCSIFADDR 设置接口地址。ifr.ifr_addr 字段返回地址。 ioctl(fd, SIOCGIFADDR, (caddr_t)&ifr, sizeof(struct ifreq)); ioctl(fd, SIOCSIFADDR, (caddr_t)&ifr, sizeof(struct ifreq)); struct ifreq ifr;
SIOCGIFCONF	返回系统中配置的所有接口的配置信息。 ioctl(fd, SIOCGIFCONF, (caddr_t)&ifc); struct ifconf ifconf;