A.P. Lawrence

nwho for 5.0.x

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Message-ID: <36B97730.DE0F385F@ilion.nl>
References: <79av34$nhv$1@news.mel.aone.net.au>

How do I find out what IP address a user logged in from?

Some utilities show this by default: Linux "w" displays the hostname that users logged in from, as does "who". Other systems may divulge this with a special flag: SCO uses "w -x" on more modern versions of its OS.

John Dubois has an "oanwho" script for OSR5 described more fully at <36B97730.DE0F385F@ilion.nl>.

If the address can't be resolved with DNS, these utilities will give you the ip address. There are times when you want the IP address and not the FQDN. That can sometimes be difficult: you can pass the name to "dig" and parse the output, or perhaps fish it out of "netstat -an" in some limited cases where it is easy to programatically find it. I could use a simple Perl script on my web server (where I am the only logged in user):

#!/usr/bin/perl
open(N,"/usr/bin/netstat -an |");
while (<N>) {
 next if not /ESTABLISHED/;
 next if not /64.226.42.29.22/;
# webserrver address
 s/  */ /g;
 @a=split / /;
 $_=$a[4];
 s/\.[0-9][0-9]*$//;
 print;
 exit 0;
 }

I could have also fished it out of "w" and used gethostbyname . But on this BSD box, "w" truncates the host name if it is long:

10:21AM  up 25 days,  6:32, 1 user, load averages: 0.59, 0.67, 0.70
USER             TTY      FROM              LOGIN@  IDLE WHAT
pcunix           p0       h00c0f05badf1.ne  9:26AM     - w

Fortunately, "who am i" is just what I want:

pcunix           ttyp0   Jun  3 09:26   (65.96.9.237)

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