Bash Script: Check if user is on system

#!/bin/bash
function usersys {
if grep $USERN /etc/passwd
then
        echo "$USERN is in system."
        exit 0
#
else
        echo "$USERN is not in system."
        exit 0

fi

}
#

function usr {
read -p "Enter username:" USERN

if test $USERN
then
        echo "Username: $USERN"
        usersys
#
else
        echo "You did not enter a username. Enter Username"
        usr
fi
}

usr