From: Francis Cianfrocca <garbagecat10@...>
Date: 2007-07-19T00:35:01+09:00
Subject: Re: Listing all IP addresses on an multihomed system

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On 7/18/07, Daniel Berger <djberg96@gmail.com> wrote:
>
> Hi all,
>
> I'm wondering if there's a way to list all IP addresses on a
> multihomed system using Ruby's Socket API. I actually want this for
> the sys-host library (at http://www.rubyforge.org/projects/sysutils).
> It's C, but I figure I can reverse engineer the Ruby code back to C.
>
> Here's the equivalent of what I'm currently doing (in C):
>
> #include <unistd.h>
> #include <netdb.h>
> #include <stdio.h>
> #include <arpa/inet.h>
>
> #define BUF 256
>
> int main(){
>    struct hostent* h;
>    char hostname[BUF];
>    char ip[BUF];
>
>    if(gethostname(hostname, BUF) != 0){
>       printf("gethostbyname failed\n");
>       return -1;
>    }
>
>    printf("Hostname: %s\n", hostname);
>
>    h = gethostbyname(hostname);
>
>    if(!h){
>       printf("gethostbyname failed\n");
>       return -1;
>    }
>
>    while(*h->h_addr_list){
>       printf("Addr: %s\n", inet_ntop(h->h_addrtype, *h->h_addr_list,
> ip, BUF));
>       *h->h_addr_list++;
>    }
>
>    return 0;
> }
>
> But, at least one user has reported that he has eth0 configured with a
> LAN IP and eth1 that has 5 attached IP addresses. The above code
> doesn't pick them up.
>
> Is there a pure Ruby solution? Is it just a matter of
> Socket.getaddrinfo(Socket.gethostname, 80)? Or, does anyone happen to
> know the C solution?
>
> Thanks,
>
> Dan
>
>
>

Since you're obviously using Linux, how about just parsing the output of
ethtool?

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