experiences with awk and uniq - john meister © 2017


In trying to determine which users have logged into a system I tried variations of "uniq" to 
break down the list from "last".  However, it's not as easy as I thought.  It seems that uniq doesn't 
always work as expected.  Variations in distributions and a failure to RTM may be the issue.

The goal is to reduce the output from last to a single line of user information.  So far the following is true:

if I do a "last | wc -l", I get 119 occurrences on a particular system.
if I do a "last | grep -v root | wc -l", I get 88 occurrences.
if I do a "last | uniq -d | wc -l", I get 0.   (???)
if I do a "last | awk '{print $1}' | grep -v root | wc -l", I get 88.

and then, if I do:

    last | awk '{print $1}' | grep -v root | uniq -d | wc -l  
  I get 12... with 10 of those being duplicates, and another 2, one of those being a duplicate.

THEN, if I do:
 last | awk '{print $1}' | grep -v root | grep -v reboot | uniq -d | wc -l 
and didn't get the same answer!!!

so much for a "uniq" afternoon.... :)    It's close enough for what I'm looking
for though...  wait...  I'll try using it with sort...
 
last | awk '{print $1}' | grep -v root | grep -v reboot | sort | uniq -d

AHA!, it works, while the other "uniq" without "sort" doesn't, see:

>--> last | awk '{print $1}' | grep -v root | grep -v reboot | uniq -d 
jxxxxxx
jxxxxxx

 -----------------------------------------------------
root@wxxxxxxx [/root]

>--> last | awk '{print $1}' | grep -v root | grep -v reboot | sort | uniq -d
cxxxxxxx
jxxxxxxx


so, now I can take this string and run it through my for loop and remotely 
check each workstation for user id so I can update my password file with only
those users that have accessed my systems. :)


#!/bin/sh
#
#  99dec17 - get user names from last
#
echo " executing script to determine users on all HP engineering workstations "

for x in `cat /raid/02d/sa/rem/hostseng`
        do
        echo $x >> /raid/02d/sa/rem/log.`/usr/bin/date +%y%b%d`.users
        echo " ================== " >>  /raid/02d/sa/rem/log.`/usr/bin/date +%y%b%d`.users
        echo $x
        remsh $x last | awk '{print $1}' | grep -v root | grep -v reboot | sort | uniq -d \
                | tee -a  /raid/02d/sa/rem/log.`/usr/bin/date +%y%b%d`.users
        echo " ================== "
        echo " ================== " >>  /raid/02d/sa/rem/log.`/usr/bin/date +%y%b%d`.users
        done

echo " completed list, results found in /raid/02d/sa/rem/log.`/usr/bin/date +%y%b%d`.users "