newuser.sh

#!/bin/bash

CONTINUE=false
USERNAME=null
GROUPNAME=null

check_username () {
   if [ id -u "$USERNAME" >/dev/null 2>&1 ]; then
      echo 'This user already exists.'
      CONTINUE=false
   else
      echo 'This username is available. The user will be created.'
      sudo useradd -m $USERNAME
      CONTINUE=true
   fi
}

check_groupname () {
   if [ $(getent group $GROUPNAME) ]; then
      echo 'This group already exists. The user will be added to it.'
   else
      echo 'This group does not exist. The group will created and the user will be added to it.'
      sudo groupadd $GROUPNAME
   fi

   sudo usermod -a -G $GROUPNAME $USERNAME
   echo "User $USERNAME was created and added to group $GROUPNAME."
}

echo 'Enter the username for a new user:'
read USERNAME

check_username

if [ $CONTINUE = true ]; then
   echo 'Enter the groupname to assign the new user to:'
   read GROUPNAME
   check_groupname
fi