C example to getting IP address from a network interface, run on Raspberry Pi/Raspbian Jessie

C example to getting IP address from a network interface, run on Raspberry Pi/Raspbian Jessie.


Reference: http://www.geekpage.jp/en/programming/linux-network/get-ipaddr.php

cIP.c

#include <stdio.h>

#include <string.h> /* for strncpy */

#include <sys/types.h>
#include <sys/socket.h>
#include <sys/ioctl.h>
#include <netinet/in.h>
#include <net/if.h>

/*
 *  Getting IP address from a network interface
 *  reference: http://www.geekpage.jp/en/programming/linux-network/get-ipaddr.php 
 * 
 */
 
int main()
{
    int fd;
    struct ifreq ifr;

    fd = socket(AF_INET, SOCK_DGRAM, 0);
    
    /* I want to get an IPv4 IP address */
    ifr.ifr_addr.sa_family = AF_INET;
    
    /* I want IP address attached to "eth0" */
    strncpy(ifr.ifr_name, "eth0", IFNAMSIZ-1);
    
    ioctl(fd, SIOCGIFADDR, &ifr);
    
    close(fd);
    
    /* display result */
    printf("%s\n", inet_ntoa(((struct sockaddr_in *)&ifr.ifr_addr)->sin_addr));
    
    return 0;
}

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