General :: Shell Script To Find Enabled System Accounts?

I wrote a small script that gets me the list of enabled system accounts in my system.

I figure '*' & '!' (in field #2 of /etc/shadow) mean that the account is disabled or they cannot login, hence 'safe-to-ignore'

Code:
IFS=$'
'
for i in `cat /etc/passwd` #get each line in the passwd file
do
var1=`echo $i | cut -d':' -f3` #get user ID field
if [ $var1 -lt 500 ] && [ $var1 -gt 0 ] #compare to extract relevant IDs

[Code].....

BTW i figure the following command gives me the list of system users, but i am not able to find a way to process it further... :-(

Code:
awk -F":" '$3 >= 1 && $3 < 500 { print $1 }' /etc/passwd