/*****************************************************************************
 * This Linux code came from a Usenet posting:
 *
 * http://groups.google.com/groups?selm=u0ndla.t9r.ln%40charon.heiming.de&oe=UTF-8&output=gplain
 * Michael Heiming
 * From: Michael Heiming (michael+USENET@heiming.de)
 * Subject: Re: Code to discover interfaces and IP address
 * Newsgroups: alt.os.linux
 * Date: 2002-09-07 13:25:04 PST
 *****************************************************************************/

#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <net/if.h>
#include <sys/ioctl.h>
#include <arpa/inet.h>
 
int main( int argc, char *argv[])
{
  FILE *f=fopen("/proc/net/dev","r");
  char buf[4096];
  char *p;
  struct ifreq ifr;
  int fd;
   if (!f) {
    perror("/proc/net/dev");
    exit(1);
  }
  fd = socket(AF_INET,SOCK_DGRAM, 0);
  if (fd==-1) {
    perror("socket");
    exit(1);
  }
while (fgets(buf,4096,f)) {
    if ((p=strchr(buf,':'))) {
      *p=0;
      for (p=buf;*p == ' ';++p);
      strcpy(ifr.ifr_name, p);
      if (ioctl(fd, SIOCGIFADDR, &ifr)) {
        perror(p);
      } else {
        printf( "%s: %s\n", p,inet_ntoa(*(struct 
in_addr*)(ifr.ifr_ifru.ifru_addr.sa_data+2)));
      }
    }
  } return 0;
}