get hostname addresses

ipshow.c

//
//  ipshow.c
//  IPSHOW
//
//  Created by Jackey Chen on 8/18/15.
//  Copyright (c) 2015 Jackey Chen. All rights reserved.
//

#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, const char * argv[]) {
    struct addrinfo hints, *p, *res;
    
    char ipstr[INET6_ADDRSTRLEN];
    
    if (argc != 2) {
        fprintf(stderr, "usage: SimpleC hostname \n");
        return 1;
    }
    
    memset(&hints, 0, sizeof (hints));
    
    hints.ai_family = AF_INET;
    hints.ai_socktype = SOCK_STREAM;
    int status;
    if (( status = getaddrinfo(argv[1], NULL, &hints, &res) ) != 0 ) {
        fprintf(stderr, "error: get %s ip address failed \n", argv[1]);
        return 1;
    }
    
    char *ipver;
    void *addr;
    for (p = res; p != NULL; p = p->ai_next) {
        if (p->ai_family == AF_INET) {
            ipver = "ipv4";
            struct sockaddr_in *addrv4 = (struct sockaddr_in *) p->ai_addr;
            addr = &(addrv4->sin_addr);
        }
        else if (p->ai_family == AF_INET6) {
            ipver = "ipv6";
            struct sockaddr_in6 *addrv6 = (struct sockaddr_in6 *) p->ai_addr;
            addr = &(addrv6->sin6_addr);
        }
        
        inet_ntop(p->ai_family, addr, ipstr, sizeof ipstr);
        
        printf("%s: %s \n", argv[1], ipstr);
    }
    
    freeaddrinfo(res);
    
    return 0;
}