Create a Linux user through script

create_user.sh

#!/bin/bash
# ------------------------------------------------------------------
# Am i Root user?
if [ $(id -u) -eq 0 ]; then
        read -p "Enter username : " username
        egrep "^$username" /etc/passwd >/dev/null
        if [ $? -eq 0 ]; then
                echo "$username exists!"
                exit 1
        else
                password=$(date +%s%N | sha256sum | head -c48)
                useradd -s /bin/bash -g backup -m -p "$password" "$username"
                if [ $? -eq 0 ]; then
                        echo "User has been added to system!"
                        chmod 700 /home/$username
                        read -p "Public Key : " pubkey
                        mkdir -p /home/$username/.ssh
                        echo "$pubkey" > /home/$username/.ssh/authorized_keys
                        chown -R $username:backup /home/$username/.ssh
                        chmod 700 /home/$username/.ssh
                        chmod 600 /home/$username/.ssh/authorized_keys
                else
                        echo "Failed to add a user!"
                        exit 2
                fi
        fi
else
        echo "Only root may add a user to the system."
        exit 2
fi