Help modify this script

#!/bin/sh 
#---------------------------------------------------------------------begin--#
#  create_users <inputfile>
#  Purpose: add users using an input file
#  Layout inputfile: fullname:loginname:usergroup:shelltouse
#-----------------------------------------------------------

# Variables
DEFAULTSHELL="/bin/bash"                           # Change default shell here 
LEGALSHELLS="/etc/shells"                          # File with valid shells
LEGALGROUPS="/etc/group"                           # File with valid groups 

PWDIR="`pwd`"
EFILE="${PWDIR}/unable2create.`date '+%y%m%d'`"

# Functions
Check_All()
{
  # is FULLNAME provided
  [[ -z ${FULLNAME} ]] && ALL_OK="Full name"
  # is LOGINNAME provided
  [[ -z ${LOGINNAME} ]] && ALL_OK="Login name"
  # is LOGINNAME valid
  grep "^${LOGINNAME}:" /etc/passwd > /dev/null 2>&1
  [ "$?" -eq 0 ] && ALL_OK="Loginname"
  # is USERGROUP provided
  [[ -z ${USERGROUP} ]] && ALL_OK="Usergroup"
  # is USERGROUP valid
  grep "^${USERGROUP}:" ${LEGALGROUPS} > /dev/null 2>&1
  [ "$?" -eq 1 ] && ALL_OK="Usergroup"
}

# Main
clear

echo ""
echo "Running........"
echo ""

rm ${EFILE} > /dev/null 2>&1

# Is inputfile provided:
[[ -z $1 ]] && echo "Error: No input file given. Quiting." && exit 1

INFILE=$1

# Script run with root privilage:
if [ "$UID" != "0" ]
then 
  echo "Error: You must be root." 
  exit 1 
fi 

# Need the following to answer questions in a pipe
exec 3>&0

# Process inputfile:

cat ${INFILE} | \
while read ONELINE
do
  FULLNAME="`echo ${ONELINE} | awk -F: '{ print $1 }'`"
  LOGINNAME="`echo ${ONELINE} | awk -F: '{ print $2 }'`"
  USERGROUP="`echo ${ONELINE} | awk -F: '{ print $3 }'`"
  SHELLTOUSE="`echo ${ONELINE} | awk -F: '{ print $4 }'`"

  # Check input fields
  ALL_OK="0"
  Check_All
  if [[ ${ALL_OK} = "0" ]]
  then
    # All is well: Let's continue......

    # is SHELLTOUSE provided
    if [[ -z ${SHELLTOUSE} ]]
    then
      # Use default shell
      SHELLTOUSE="${DEFAULTSHELL}"
    else
      # Is choosen shell valid
      grep "^${SHELLTOUSE}$" ${LEGALSHELLS} > /dev/null 2>&1
       if [ "$?" -eq 1 ]
       then
         # shell not valid, use default instead.
         SHELLTOUSE="${DEFAULTSHELL}"
         echo "Shell-> ${ONELINE}" >> ${EFILE}
       fi
    fi

    # Show and ask
    echo "Name  : $FULLNAME"
    echo "Login : $LOGINNAME" 
    echo "Group : $USERGROUP"
    echo "Shell : $SHELLTOUSE"
    echo ""
    printf "%s\n" "Is all this correct?"
    <&3 read ANSWER

    case "$ANSWER" in
      y | Y | Yes | YES )
        $(adduser "$LOGINNAME" -c "$FULLNAME" -s "$SHELLTOUSE" -g "$USERGROUP")
        <&3 /usr/bin/passwd "$LOGINNAME"
        echo ""
      ;;
      n | N | No | NO )
        echo ""
        echo "Ignoring this line of input, will continue with next line."
      ;;
    esac
  else
    # Something went wrong: Write to errorfile, set token and continue
    echo "${ALL_OK}-> ${ONELINE}" >> ${EFILE}
  fi

done

# Did something go wrong
if [[ -a ${EFILE} ]]
then
  # Yep
  echo ""
  echo "-----------------------------------------------------------------------"
  echo "Something went wrong during processing, please check:"
  echo ""
  echo "${EFILE}"
fi

# Done
echo ""
  echo "----------------------------------------------------------------------------"
echo "Done."
echo ""

exit 0
#-----------------------------------------------------------------------end--#