Re: Re: Fetching ARP table with NetPacket

In this case, GNU/Linux, I could use the arp command. Indeed I don't need this script to know "who's online", or anything like it, but I do need it because I wanted an example of how I could fetch the mac address of the network interfaces I have installed on my machine using code (it's a research work, by the way), and not internalizing another program such as system("arp -a"). I also ocurred me that it could be useful to fetch the entire arp table, so I asked the question as above :) I imagine I could fetch it from /proc. But I'm not sure how portable this solution is. I know it stands almost for the same as fetching from the "arp -a" results, but it's more tolerable from the point of view of this research (not my idea). Again, any help is appreciated.

Comment on Re: Re: Fetching ARP table with NetPacket

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Re: Re: Re: Fetching ARP table with NetPacket by hsinclai (Deacon) on Jun 01, 2004 at 16:58 UTC
I'm sure there are shorter, much more elegant ways of doing this (hire a monk:), plus in a multi-interface system, you'd want more info about which "device" from the arp table.. but, here's a basic approach.. `#!/usr/bin/perl -w # kernels 2.4.x /proc/net/arp use strict; my $ipad; my $macad; my @arp; if ( -r "/proc/net/arp" ) { open(ARP,"</proc/net/arp"); @arp = <ARP>; close(ARP); } else { die("Cannot access arp in proc $!"); } foreach my $linein ( @arp ) { chomp($linein); next if $linein =~ /IP/i; $ipad = (split(/\s+/,$linein))[0]; $macad = (split(/\s+/,$linein))[3]; print "IP address $ipad has MAC Address $macad\n"; }` [download] to start with.. definitely not portable to Windows or BSD, just linux You could also split up each record getting a value for each field with something like `($ipad,$macad,$hwtype,$flags,$mask,$device) = split(/\s+/,$linein);` [download] -hsinclai	[reply] [d/l] [select]

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Re: Re: Re: Fetching ARP table with NetPacket
by hsinclai (Deacon) on Jun 01, 2004 at 16:58 UTC


#!/usr/bin/perl -w

# kernels 2.4.x /proc/net/arp

use strict;

 my $ipad;
my $macad;
  my @arp;

if ( -r "/proc/net/arp" ) {
   open(ARP,"</proc/net/arp");
   @arp = <ARP>;
   close(ARP);
} else {
     die("Cannot access arp in proc $!");
}

foreach my $linein ( @arp ) {
  chomp($linein);
  next if $linein =~ /IP/i;
  $ipad  = (split(/\s+/,$linein))[0];
  $macad = (split(/\s+/,$linein))[3];
  print "IP address $ipad has MAC Address $macad\n";
}
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($ipad,$macad,$hwtype,$flags,$mask,$device) = split(/\s+/,$linein);
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