Hi

I'm trying to write a function to read the local IP eth0/eth1... using glibc library...
I found only examples that found the 127.0.0.1 IP but not the real IP :

http://community.freepascal.org:10000/bboards/message?message_id=233776&forum_id=24083 http://lists.freepascal.org/lists/fpc-pascal/2002-March/002932.html

Is someone could help me to find the solution...
Currently i use regex on ifconfig that is a hack!

best regards

I'm trying to write a function to read the local IP eth0/eth1 using glibc library...

program ip_addr;
{$MODE OBJFPC}
uses libc;
const
  IP_NAMESIZE = 16;
type
  ipstr = array[0..IP_NAMESIZE-1] of char;
function GetIPAddressOfInterface( if_name:ansistring):ansistring;
var
  ifr : ifreq;
  tmp:ipstr;
  sock : longint;
  p:pChar;
begin
  Result:='0.0.0.0';
  strncpy( ifr.ifr_ifrn.ifrn_name, pChar(if_name), IF_NAMESIZE-1 );
  ifr.ifr_ifru.ifru_addr.sa_family := AF_INET;
  FillChar(tmp[0], IP_NAMESIZE, #0);
  sock := socket(AF_INET, SOCK_DGRAM, IPPROTO_IP);
  if ( sock >= 0 ) then begin
    if ( ioctl( sock, SIOCGIFADDR, @ifr ) >= 0 ) then begin
      p:=inet_ntoa( ifr.ifr_ifru.ifru_addr.sin_addr );
      if ( p  nil ) then strncpy(tmp, p, IP_NAMESIZE-1);
      if ( tmp[0]  #0 ) then Result :=  tmp;
    end;
    libc.__close(sock);
  end;
end;

begin
if (ParamCount=1)
then WriteLn(GetIPAddressOfInterface(ParamStr(1))) else WriteLn('Usage:', ParamStr(0), '<interface-name>') end.

- Jeff

Please ignore my last post -
This one is a little cleaner...

program ip_addr;
{$MODE OBJFPC}
uses libc;
function GetIPAddressOfInterface( if_name:ansistring):ansistring;
var
  ifr : ifreq;
  sock : longint;
  p:pChar;
begin
  Result:='0.0.0.0';
  strncpy( ifr.ifr_ifrn.ifrn_name, pChar(if_name), IF_NAMESIZE-1 );
  ifr.ifr_ifru.ifru_addr.sa_family := AF_INET;
  sock := socket(AF_INET, SOCK_DGRAM, IPPROTO_IP);
  if ( sock >= 0 ) then begin
    if ( ioctl( sock, SIOCGIFADDR, @ifr ) >= 0 ) then begin
      p:=inet_ntoa( ifr.ifr_ifru.ifru_addr.sin_addr );
      if ( p  nil ) then Result :=  p;
    end;
    libc.__close(sock);
  end;
end;
var
  i:LongInt;
begin
  if (ParamCount>0)
  then for i:=1 to ParamCount
       do WriteLn(GetIPAddressOfInterface(ParamStr(i)))
  else WriteLn('Usage:', ParamStr(0), '<interface-name>')
end.

It doesn't seem like you're using libc specific functions ? You can also write a fpc 'native' one using fpsocket and fpioctl in baseunix/unix, I think.

Micha

Many Thanks Jeff and Micha.

This function works perfectly without need to regex ifconfig... And i use glibc
I develop only on linux system.

Great respects...
Just another question... (this because i came from Windows OS) how can i list wich interface loaded without need to parse /etc/networks/...? (wlan0,wlan1,eth0,eth1...)

Best regards...

This function works perfectly without need to regex ifconfig... And i use glibc I develop only on linux system.

Note that it is linux/x86 only. No 64-bit, or other platforms.

OK i understand that i using i386 no 64 bits

how can i list wich interface loaded without need to parse /etc/networks/...?

I would parse /proc/net/dev instead....

program ifnames;
var
  s:shortstring;
  f:text;
  p:LongInt;
begin
  assign(f,'/proc/net/dev');
  reset(f);
  while not eof(f) do begin
    readln(f,s);
    p:=pos(':',s);
    if ( p > 0 ) then begin
      delete(s, p, 255);
      while ( s  '' ) and (s[1]=#32) do delete(s,1,1);
      writeln(s);
    end;
  end;
  close(f);
end.

I would parse /proc/net/dev instead....

Better, but still Linux only. For a good solution, a resolver unit that accesses libc should be written that is portable (unlike the libc unit)

Many Thanks for this way jeff...
/proc/net/dev is more compatible
Impressed it
for your information.
My program will run only on linux system...

Better, but still Linux only. For a good solution, a resolver unit that accesses libc should be written that is portable (unlike the libc unit)

If I understood correctly, the OP had two questions:

1. Retrieve a list of interface names on a *linux* system.
2. Return the IP address for a given *linux* interface name.

And the only "good" solution is a portable resolver unit?

How will you resolve "eth0" on Win32 or BSD ?

-Jeff

I have these two functions in my .bashrc file. You only need to run "ii" for the cool output. Now back to the question - If it is for linux only, why not just use the /sbin/ifconfig output. After all, it is accurate and seem much easier than all those libc/library methods. I pull the IPs and Interfaces available from the /sbin/ifconfig output and works just fine. If it was needed on windows, I am sure you could to the same thing with the 'ipconfig' output.

My 2c worth! :-)

Regards,
- Graeme -

------------ .bashrc ---------------------
function my_ip() # get IP adresses
{
MY_IP=$(/sbin/ifconfig eth0 | awk '/inet/ { print $2 } ' | sed -e s/addr://) MY_ISP=$(/sbin/ifconfig ppp0 | awk '/P-t-P/ { print $3 } ' | sed -e s/P-t-P://)
}

function ii() # get current host related info
{
echo -e "\nYou are logged on ${RED}$HOST"
echo -e "\nAdditionnal information:$NC " ; uname -a echo -e "\n${RED}Users logged on:$NC " ; w -h
echo -e "\n${RED}Current date :$NC " ; date
echo -e "\n${RED}Machine stats :$NC " ; uptime
echo -e "\n${RED}Memory stats :$NC " ; free

    my_ip 2>&- ;
    echo -e "\n${RED}Local IP Address :$NC" ; echo ${MY_IP:-"Not connected"}
    echo -e "\n${RED}ISP Address :$NC" ; echo ${MY_ISP:-"Not connected"}
    echo

}
---------------------------------

I don't understand that last one. _WHY_ would you want to enumerate and then still use hardcoded "eth0" What if eth0 is my internal and eth1 my external interface? The only meaning of the name is order of detection.

And the only "good" solution is a portable resolver unit? How will you resolve "eth0" on Win32 or BSD ?

Usually you enumerate the interfaces list, till you find the interface with the "default" (ANY) route, so you have the default gateway, regardless of name. That is usually the interface you interested in.

IOW names say nothing, routes and masks do.

Many thanks to the community

To reply to Graeme :
why not just use the /sbin/ifconfig output ?
Simply to be more dev compliance... using an external program is slower and sometime ifconfig doesn't exist or is deleted on target computers.

To reply to Marco :
And the only "good" solution is a portable resolver unit? How will you resolve "eth0" on Win32 or BSD ?

For WIN32, i d'ont care because the program is only for Linux systems. Your are true, in BSD the network interface is not the same and i must detect wich interface is used...

Best regards