dns lookup

DNSLookup.cpp

// Author : Ouarrak Ayoub

#include <netinet/in.h>
#include <sys/socket.h>
#include <sys/types.h>
#include <arpa/inet.h>
#include <iostream>
#include <netdb.h>
#include <cstring>
#include <string>

struct in_addr IPv4addr;
struct hostent* host;

int main(int argc, char** argv) {
    char hostname[50] = "localhost";
    bool localhost = false;

    if (argc == 1) {
        host = gethostbyname(hostname);
        localhost = true;
    }

    if (argc > 2) {
        std::cout << std::endl << "Usage :" << std::endl;
        std::cout << "./DNSLookup [hostname/IP Address]" << std::endl
                  << std::endl;
        return (1);
    }

    if (!localhost) {
        std::strcpy(hostname, argv[1]);
        if (hostname[0] >= 48 && hostname[0] <= 57) {
            inet_pton(AF_INET, hostname, &IPv4addr);
            host = gethostbyaddr(&IPv4addr, sizeof(IPv4addr),
                                 AF_INET);  // get hostent by IP address
        } else
            host = gethostbyname(hostname);  // get hostent by  domain name

        if (host == NULL) {
            std::cout << "undefined hostname : " << hostname << std::endl;
            return (2);
        }
    }

    std::cout << "------- Hostname info -------" << std::endl << std::endl;
    std::cout << "Name : " << host->h_name << std::endl;

    for (int i = 0; host->h_aliases[i]; ++i)
        std::cout << "Aliases : " << host->h_aliases[i] << std::endl;

    std::cout << "Address type : " << host->h_addrtype << std::endl;
    std::cout << "Length : " << host->h_length << std::endl;
    std::cout << "Address : " << inet_ntoa(*(struct in_addr*)host->h_addr)
              << std::endl;

    return (0);
}