Re: IP address without hostname

[Nicos Gollan <gtdev@spearhead.de>]

On Friday 16 August 2002 20:41, Peter Bartosch wrote:
> hello
>
>
> i've got a little problem with a c program:
>
> i'm searching for a function to gather the IP adresses from the
> interfaces of a computer - without having the hostname nor any other
> information ...

I found this somewhere on another maillist. It uses ioctl() to poll some 
information.

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/ioctl.h>
#include <sys/socket.h>
#include <net/if.h>
#include <arpa/inet.h>
#include <netinet/in.h>
#define MAX_NUM_IFREQ (512)

main() {

  struct ifconf       Ifc;
  struct ifreq        IfcBuf[MAX_NUM_IFREQ];
  struct ifreq        *pIfr;
  struct ifreq single;
  int num_ifreq;
  int i;
  int fd;

  Ifc.ifc_len = sizeof(IfcBuf);
  Ifc.ifc_buf = (char *) IfcBuf;
  if ((fd = socket(AF_INET, SOCK_DGRAM, 0)) < 0) {
    perror("socket()");
    exit(1);
  }
  if ( ioctl(fd, SIOCGIFCONF, &Ifc) < 0) {
    perror("ioctl SIOCGIFCONF");
    exit(1);
  }
  num_ifreq = Ifc.ifc_len / sizeof(struct ifreq);
  for ( pIfr = Ifc.ifc_req, i = 0 ; i < num_ifreq; pIfr++, i++ ) {
    memcpy(single.ifr_name,pIfr->ifr_name,IF_NAMESIZE);
    if( ioctl(fd, SIOCGIFADDR, &single) < 0 ) {
      perror("ioctl SIOCGIFADDR");
      exit(1);
    }
    
    printf("%d: %s<= is: %s\n", i, pIfr->ifr_name, inet_ntoa(((struct 
sockaddr_in*)&single.ifr_addr)->sin_addr));
  }
}


-- 
Embedded Linux -- True multitasking!
TWO TOASTS AT THE SAME TIME!