Bash adduser script to generate Linux useradd syntax strings

#!/bin/bash
# adduser - build a useradd string and a password for passwd
# by typedeaF
# grep -v '^#' thisfile.sh | less to strip the comments

# Make a semi-random password using an array of user-friendly characters
function mkpass() {
  PASS=""
  PASSLEN=8
  array1=( q w e r t y u i o p a s d f g h j k l z x c v b n m
    Q W E R T Y U I O P A S D F G H J K L Z X C V B N M
    1 2 3 4 5 6 7 8 9 0 \! \@ \# \$ \% \^ \& \* \( \)
  )
  MODNUM=${#array1[*]}

  count=0
  while [ ${count:=0} -lt $PASSLEN ]
  do
    number=$(($RANDOM%$MODNUM))
    PASS="$PASS""${array1[$number]}"
    ((count++))
  done

  echo $PASS
}

# center the text on the screen by finding the horizontal center with max_lines
# max_lines divided by two becomes the center line(aka. line_num)
# use the max lenght of the line divided in half to find the center column
# subtract half the output string from the center to create the offset to indent
function center_txt() {
  PROMPT="$1"
  str_len=${#PROMPT}
  indent=$(( ((max_cols / 2)) - ((str_len / 2)) ))
  line_num=$(( max_lines / 2 ))
  tput cup ${line_num} ${indent}
  echo "$PROMPT"
}

# indent_txt is intended to be used AFTER center_txt
# indent_txt just prints on the current line and centers the text horizontally
# line_num is global, so main keeps track of incrementing it
function indent_txt() {
  PROMPT="$1"
  str_len=${#PROMPT}
  indent=$(( ((max_cols / 2)) - ((str_len / 2)) ))
  tput cup ${line_num} ${indent}
  echo "$PROMPT"
}

# mk_prompt creates an input prompt for the the read function
# 'read -p "==> " variable' would work, but I like this better
function mk_prompt() {
  ((line_num+=2))
  tput cup $line_num 15
  PROMPT="==> "
  echo -n "${blink}${PROMPT}"
  echo -n ${offblink}
}

# This function gathers all the information needed to generate the useradd string
function mkuser() {
  USERNAME=""
  FULLNAME=""
  EXPIRE=""
  GROUP=""
  HOME=""

  echo ${term_clr}
  PROMPT="Enter the new Login account name"
  center_txt "$PROMPT"
  ((line_num++))
  PROMPT="(ex. typedeaf)"
  indent_txt "$PROMPT"
  mk_prompt
  read USERNAME

  echo ${term_clr}
  PROMPT="Enter the users Full Name"
  center_txt "$PROMPT"
  ((line_num++))
  PROMPT="(ex. Mister typedeaF)"
  indent_txt "$PROMPT"
  mk_prompt
  read FULLNAME

  echo ${term_clr}
  PROMPT="Select the users Primary Group"
  center_txt "$PROMPT"
  ((line_num++))
  PROMPT="(ex. type \"1\" for Primary Group staff)"
  indent_txt "$PROMPT"
  ((line_num+=2))
  indent=$(( ((max_cols / 2)) - 6 ))
  tput cup $line_num $indent; ((line_num++)); echo "1) staff"
  tput cup $line_num $indent; ((line_num++)); echo "2) faculty"
  tput cup $line_num $indent; ((line_num++)); echo "3) parttime"
  tput cup $line_num $indent; ((line_num++)); echo "4) adjunct"
  mk_prompt
  read REPLY

  case "$REPLY" in
  1)
    GROUP="staff"
    HOME="/home/$GROUP/$USERNAME"
    # add some staff specific stuff here
    ;;
  2)
    GROUP="faculty"
    HOME="/home/$GROUP/$USERNAME"
    # add some faculty specific stuff here
    ;;
  4)
    GROUP="adjunct"
    HOME="/home/$GROUP/$USERNAME"
    # add some adjunct specific stuff here
    ;;
  3)
    GROUP="parttime"
    HOME="/home/$GROUP/$USERNAME"
    echo ${term_clr}
    PROMPT="Enter the Expiration Date"
    center_txt "$PROMPT"
    ((line_num++))
    PROMPT="(ex. 2004-06-30 for June 30th 2004)"
    indent_txt "$PROMPT"
    mk_prompt
    read EXPIRE
    ;;
  * )
    echo "Invalid choice"
    ;;
  esac
}

# Just reset the terminal to normal
function _quit() {
  reset -Q
  echo "Exiting addfas.sh. Bye"
  exit 0
}


# =================================================#
# Begin Main #
# =================================================#

# These are the tput commands used to terminal output formatting
term_clr=$(tput clear)
max_lines=$(tput lines)
max_cols=$(tput cols)
blink=$(tput blink)
offblink=$(tput sgr0)

let CONTINUE=0

# Set up a trap to handle control signals. If you start using temp files then
# this is where you would want to clean up.
trap _quit INT TERM QUIT

# This could just as easily been while [ TRUE ], but the CONTINUE sentinal
# is included for flexability.
while [ $CONTINUE -eq 0 ]
do
  mkuser
  echo ${term_clr}
  PROMPT="User added with the following criteria"
  center_txt "$PROMPT"
  ((line_num+=2))

# There are more complex ways to handle this, like with the tertiary expr?expr:expr
# syntax, but it only makes things more complex looking at the sake of saving a
# few key strokes. Notice that using something like ${EXPIRE+-e$EXPIRE}
# doesnt work quite like expected. Instead of trying to cut corners and make 'leet'
# code, just keep it simple.
  if [ -z "$EXPIRE" ]; then
    PROMPT="useradd -c\"$FULLNAME\" -d$HOME -g$GROUP $USERNAME"
    indent_txt "$PROMPT"
    ((line_num+=2))
  else
    PROMPT="useradd -c\"$FULLNAME\" -d$HOME -e$EXPIRE -g$GROUP $USERNAME"
    indent_txt "$PROMPT"
    ((line_num+=2))
  fi
  uline=$(tput smul)
  offuline=$(tput rmul)
  PROMPT="Recommended Password:"
# I confess, I couldn't find a way to get $PASSLEN to parse correctly so I gave up
# and used the variable constant '8'.
  str_len=$(( ${#PROMPT} + 8 ))
  indent=$(( ((max_cols / 2)) - ((str_len / 2)) ))
  tput cup ${line_num} ${indent}
  echo -n "${uline}$PROMPT${offuline} "
  mkpass
  tput cup $max_lines
# Here is where you might want to include your CONTINUE sentinal.
# Like: if [ "$REPLY" = "x" ]; then CONTINUE=1; fi
  PROMPT="Press Return to continue. Press ^C to EXIT."
  echo -n "${blink}${PROMPT}"
  echo -n ${offblink}
  read -s
done

# reset your signal traps
trap - INT TERM QUIT
exit 0