리눅스상에서 쉘프로그레밍 질문입니다.

#!/bin/bash
#_id
#_pass
#_url

clear
time=$(date+%Y%m%d)
echo
echo =======================================
echo
echo " "
echo
echo user id, passwd, domain_address insert
echo
echo =======================================
echo
echo -n "user id insert:"
read _id
echo -n :passwd insert: "
read _pass
echo -n "domain_address insert :"
read _url

echo -n "
user id : $_id
user pw : $_pass
user domain : $_url
------------------------
if all correct enter , incorrect insert no :"
read _chk

if ("$_chk" != "")
then
exit
f1

echo "user add."
echo
useradd -c$_id$time -d /home/hosting/$_id -g hosting $_id

echo $_pass | passwd --stdin $_id

echo
echo " user add finish"

리눅스 초보인데 이게 어떤 부분에서 어떤식으로 동작되는지를 모르겠어서 이자료를 올립니다.