Question

find IP address of local machine

Asked by: fahadkhowaja

hi!

I'm trying to figure out a way to get the IP addresses associated with all network interfaces in my laptop. I have two interfaces :

1) eth0 - ethernet
2) eth1 - cisco wireless card

I read around and wrote this small program:

#include <stdio.h>
#include <unistd.h>
#include <netdb.h>
                                                                               
int main() {
        char hostname[100];
                                                                               
        int ret = gethostname(hostname, sizeof(hostname));
        printf("Hostname: %s\n", hostname);
                                                                               
        struct hostent *ht = gethostbyname(hostname);
                                                                               
        int i=0;
        while(ht->h_addr_list[i] != NULL) {
                printf("Address[%d]: %s\n", i, inet_ntoa(*((struct in_addr *)ht->h_addr_list[i])));
                i++;
        }
                                                                               
        return 0;
}

But the problem is that this only returns me the IP of the loopback interface 127.0.0.1 and nothing on eth0 and eth1 when both have IPs assigned to them.

I will be grateful for any help in this regard.

Fahad.

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Asked On
2005-08-19 at 04:07:46ID21532777
Tags

ip

,

address

,

find

,

machine

,

get

Topic

Linux Programming

Participating Experts
3
Points
50
Comments
4

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Answers

 

by: ozoPosted on 2005-08-19 at 04:13:39ID: 14707874

netstat -nr
ifconfig eth0
or
ipconfig

 

by: ravenplPosted on 2005-08-19 at 07:12:59ID: 14709300

 

by: sunnycoderPosted on 2005-08-19 at 07:52:49ID: 14709726

 fd = socket (AF_INET, SOCK_DGRAM,IPPROTO_IP);
  memset (&ifr, 0, sizeof (struct ifreq));
  strcpy (ifr.ifr_name, IFNAME);
  ifr.ifr_addr.sa_family = AF_INET;
  ioctl(fd, SIOCGIFADDR, &ifr);
  addr=(u_char*)&(((struct sockaddr_in * )&ifr.ifr_addr)->sin_addr);
  printf("eth %s, addr %d.%d.%d.%d\n", ifr.ifr_name,addr[0],addr[1],addr[2],addr[3]);
  close(fd);

You can find all the interfaces on your system as well as IP adresses assigned to each interface. Check this link
 http://www.daimi.au.dk/~kasperd/comp.os.linux.development.faq.html#IP

 

by: fahadkhowajaPosted on 2005-08-24 at 06:24:41ID: 14742203

thanks a lot ravenpl and sunnycoder! both of your suggestions were very helpful so I've split the points!

20120131-EE-VQP-002

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