get_ip_address.c

/*
 * main.c
 *
 *  Created on: May 22, 2015
 *      Author: khanh
 */
#include <stdio.h>
#include <string.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netdb.h>
#include <arpa/inet.h>
#include <netinet/in.h>

int main(int argc, char *argv[]) {
    // check arguments count
    if (argc != 2) {
	fprintf(stderr, "No IP host provided\n");
	return 1;
    }

    struct addrinfo hints, *receivedAddrInfo, *p;

    // set address hints
    memset(&hints, 0, sizeof hints);
    hints.ai_family = AF_UNSPEC;
    hints.ai_socktype = SOCK_STREAM;


    int status;
    if ((status = getaddrinfo(argv[1], NULL, &hints, &receivedAddrInfo))!=0)
    {
	fprintf(stderr, "getaddrinfo: %s\n", gai_strerror(status));
	return 2;
    }

    char ipAddress[INET6_ADDRSTRLEN];

    for (p = receivedAddrInfo; p!=NULL; p = p->ai_next) {
	char *ipVersion;
	void *addr;
	if (p->ai_family == AF_INET) {
	    struct sockaddr_in *addr4 = (struct sockaddr_in *)p->ai_addr;
	    addr = &(addr4->sin_addr);
	    ipVersion = "IPv4";
	} else {
	    struct sockaddr_in6 *addr6 = (struct sockaddr_in6 *)p->ai_addr;
	    addr = &(addr6->sin6_addr);
	    ipVersion = "IPv6";
	}
	inet_ntop(p->ai_family, addr, ipAddress, sizeof ipAddress);
	printf("%s: %s\n", ipVersion, ipAddress);
    }

    return 0;
}