유저 트래킹(로그인-아웃 시간재는) 하는 Shell script 인데 잘 안되네요 ...

#!/bin/bash
# Script name: spy.sh
 
while true
do
	for arg in "$@"
		do
		#This grab command will returns matched use name
		grab=`cat /etc/passwd | grep $arg |wc -l`
		if [ $grab != 0 ]; then
			#matched user found case 
			userid=`cat /etc/passwd | grep $arg | cut -d ':' -f1`
			exist=`who | grep $userid | wc -l`  #making existing tag
			logged_stat=0
			echo $exist 
			if [ $exist != 0 ]; then
				#record user logged in time
				echo "here again"
 
 
				logged_in=`who | grep $userid` # | rev | cut -d " " -f1`  #"여기도 그냥 컷으로 놔두어 버렸습니다"
				$logged_stat=1
 
 
			elif [ $logged_stat != 0 ]; then
				echo "여기를 구현 해야하는데 .... "
				logged_out=date
			fi
 
		else
			echo "not found even in /etc/passwd"
		fi
		sleep 60 # Running in every minutes 
	done
done