List all normal user and system accounts in the system

listusers.bash

#!/bin/bash
# Name: listusers.bash
# Purpose: List all normal user and system accounts in the system. Tested on RHEL / Debian Linux
# Author: Vivek Gite <www.cyberciti.biz>, under GPL v2.0+
# -----------------------------------------------------------------------------------
_l="/etc/login.defs"
_p="/etc/passwd"

## get mini UID limit ##
l=$(grep "^UID_MIN" $_l)

## get max UID limit ##
l1=$(grep "^UID_MAX" $_l)


normal_users() {
## use awk to print if UID >= $MIN and UID <= $MAX and shell is not /sbin/nologin   ##
echo "----------[ Normal User Accounts ]---------------"
awk -F':' -v "min=${l##UID_MIN}" -v "max=${l1##UID_MAX}" '{ if ( $3 >= min && $3 <= max  && $7 != "/sbin/nologin" ) print $0 }' "$_p"

}
system_users() {
echo "----------[ System User Accounts ]---------------"
awk -F':' -v "min=${l##UID_MIN}" -v "max=${l1##UID_MAX}" '{ if ( !($3 >= min && $3 <= max  && $7 != "/sbin/nologin")) print $0 }' "$_p"
}

case "$1" in
  "--all")
        system_users
        echo ""
        normal_users
	;;
  "--normal")
        normal_users
	;;
  "--system")
        system_users
        ;;
  *)
        echo $"Usage: $0 [--all|--system|--normal]"
 	exit 1
esac