Adding local system Linux Users (useradd command)

users.sh

#!/bin/bash

# this script creates a new user on the local system
# you will be prompted to enter the username (login), the person name and password

if [[ "${UID}" -ne 0 ]]
then
  echo "Run it with sudo privileges or as root"
  exit 1
fi

# ask for the user name
read -p "Enter the username to create: " USER_NAME
# ask for real name
read -p "Enter the name of the person: " FULL_NAME
# ask password
read -p "What's your password: " PASSWORD
# create a user
useradd -c "${FULL_NAME}" -m ${USER_NAME}

# check if the useradd command succeded
if [[ "${?}" -ne 0 ]]
then
  echo "The account could not be created"
  exit 1
fi

# set password programatically
echo $PASSWORD | passwd --stdin ${USER_NAME}

if [[ "${?}" -ne 0 ]]
then
  echo "The assigned password for the account could not be set"
  exit 1
fi

# force changing
passwd -e ${USER_NAME}

# displaying data
echo "================"
echo "Username: ${USERNAME}"
echo "Password: ${PASSWORD}"
echo "Hostname: ${HOSTNAME}"

variation.sh

#!/bin/bash

# this script creates a new user on the local system
# you will be prompted to enter the username and fullname as argument (optional)

if [[ "${UID}" -ne 0 ]]
then
  echo "Run it with sudo privileges or as root"
  exit 1
fi

# evaluating argument existance
if [[ "${#}" -lt 1 ]]
then
  echo "create an account on the local system with the USER_NAME and FULL_NAME as parameters"
  exit 1
fi

# filling data
USER_NAME="${1}"
# moving positional parameters
shift
FULL_NAME="${@}" # anything else written (full name with spaces)

# generate password
PASSWORD=$(date +%s%N | sha256sum | head -c48)

# create a user
useradd -c "${FULL_NAME}" -m ${USER_NAME}

# check if the useradd command succeded
if [[ "${?}" -ne 0 ]]
then
  echo "The account could not be created"
  exit 1
fi

# filled password programatic
echo ${PASSWORD} passwd --stdin ${USER_NAME}

if [[ "${?}" -ne 0 ]]
then
  echo "The assigned password for the account could not be set"
  exit 1
fi

# force changing
passwd -e ${USER_NAME}

# displaying data
echo "================"
echo "Username: ${USER_NAME}"
echo "Password: ${PASSWORD}"
echo "Hostname: ${HOSTNAME}"

exit 0

variation_improved.sh

#!/bin/bash

# this script creates a new user on the local system
# you will be prompted to enter the username and fullname as argument (optional)

if [[ "${UID}" -ne 0 ]]
then
  echo "Run it with sudo privileges or as root" 1>&2
  exit 1
fi

# evaluating argument existance
if [[ "${#}" -lt 1 ]]
then
  echo "Create an account on the local system with the USER_NAME and FULL_NAME as parameters" 1>&2
  exit 1
fi

# filling data
USER_NAME="${1}"
# moving positional parameters
shift
FULL_NAME="${@}" # anything else written (full name with spaces)

# generate password
PASSWORD=$(date +%s%N | sha256sum | head -c48)

# create a user
useradd -c "${FULL_NAME}" -m ${USER_NAME} &> /dev/null

# check if the useradd command succeded
if [[ "${?}" -ne 0 ]]
then
  echo "The account could not be created" 1>&2
  exit 1
fi

# filled password programatic
echo ${PASSWORD} passwd --stdin ${USER_NAME} &> /dev/null

if [[ "${?}" -ne 0 ]]
then
  echo "The assigned password for the account could not be set" 1>&2
  exit 1
fi

# force changing
passwd -e ${USER_NAME} &> /dev/null

# displaying data
echo "================"
echo "Username: ${USER_NAME}"
echo "Password: ${PASSWORD}"
echo "Hostname: ${HOSTNAME}"

exit 0

For the second script, you will need to pass the $1 and the $2 arguments that will represent the "username" and the "comment" of the "useradd" user creation Linux command.