#include <signal.h>
#include <unistd.h>
#include <errno.h>
#include <fcntl.h>
#include <stdio.h>
#include <stdlib.h>
#include <algorithm>
#include <net/if.h>
#include <malloc.h>
#include <string.h>
#include <sys/socket.h>
#include <sys/types.h>
#include <sys/ioctl.h>
#include <netinet/in.h>
#include <arpa/inet.h>
const char* getIPByIfName(const char*ifName)
{
    int s;
    struct ifreq ifr;
    static const char* none_ip="0.0.0.0";
    if(NULL==ifName)
        return none_ip;
    s=::socket(AF_INET,SOCK_DGRAM,0);
    if(-1==s)
        return none_ip;
    bzero(ifr.ifr_name,sizeof(ifr.ifr_name));
    strncpy(ifr.ifr_name,ifName,sizeof(ifr.ifr_name)-1);
    if(-1==ioctl(s,SIOCGIFADDR,&ifr))
    {
        TEMP_FAILURE_RETRY(::close(s));
        return none_ip;
    }
    TEMP_FAILURE_RETRY(::close(s));
    return inet_ntoa(((struct sockaddr_in*)&ifr.ifr_addr)->sin_addr);
}

int main()
{
    printf("%s\n", getIPByIfName("eth0"));
    return 0;
}