title: How would I check if user exists in a bash script and re-ask for new user if user provided is present?
body: <p>I'm a newbie to bash scripting, and I'm trying to make a script to setup some basic security on a ubuntu server. I have the following so far:</p>
  
  <pre><code>group="sudo"
  read -p "Set new sudo user's name (Please try to avoid admin or administrator, some hosts have these reserved): " new_sudo_user_name
  if [ -z "$(getent passwd $new_sudo_user_name)" ]; then
    echo "user does NOT exist."
  else
    echo "user DOES exist."
  fi
  
  echo "Please enter the new password:"
  read -s password1
  echo "Please repeat the new password:"
  read -s password2
  
  if [ $password1 != $password2 ]; then
    echo "Passwords do not match"
    exit    
  fi
  
  sudo su -c "useradd $new_sudo_user_name -s /bin/bash -m -aG $group"
  </code></pre>
  
  <p>Essentially, what I'd like for it to do is to, upon checking if the username exists already to automatically re-ask for a new username if it is found to already exist. Is this possible? If so, what is best practice to accomplish this task? </p>
  
  <p>Appreciate the help in advance :)</p>