/* getaddrbyifname -- local inet addr (ip address) lookup by interfacename

   compile with 
   $ CFLAGS="-Wall -pedantic -O2 -s" make getaddrbyifname

   example
   $ ./getaddrbyifname lo
   127.0.0.1

   don't ask me about it, sven-at-remote-dot-org
*/

#include <string.h> /* strcpy */
#include <strings.h> /* bzero */
#include <arpa/inet.h>	
#include <net/if.h> /* struct ifreq */
#include <sys/ioctl.h>
#include <stdio.h> /* puts */
#include <unistd.h> /* close */


int main(int argc, char *argv[])
{
  struct ifreq ifr;
  int sock;
  int t=1;

  if(!(argc>1) || argv[1][0]=='-')
  {
    puts( __FILE__" / "__DATE__" "__TIME__);
    puts( "parameter: [interface1] [interface2] ... ");
    puts( "example: lo eth0 ppp0");
    return(-1);
  }

  sock = socket(AF_INET, SOCK_DGRAM, 0);
  if(sock < 0)
  {
    puts("socket");
    return(-1);
  }

  while(t<argc)
  {
    bzero(&ifr,sizeof(struct ifreq));
    strcpy( ifr.ifr_name, argv[t] );
    ifr.ifr_addr.sa_family = AF_INET;
    if (ioctl( sock, SIOCGIFADDR, &ifr ) >= 0)
    {
      puts(inet_ntoa( ((struct sockaddr_in *)&ifr.ifr_addr)->sin_addr ));
    }
    t++;
  }
  close(sock);
  return(0);
}