Beautify multiple digits

#!/bin/bash
# nicenumber -- Display the given number in comma separated form 
#  Two options are acceptable ：DD(decimal point delimiter, Decimal separator ) and TD(thousands deliniter, Thousand separator )
#  Beautify digital units , If a second parameter is specified , Then the output is echoed in stdout

nicenumber(){
    
# Note that we assume ‘.’ Is the decimal separator of the script input value 
# Unless the user specifies options -d Other delimiters are specified , Otherwise, the decimal separator in the output value is also .
# If there is no corresponding field in the character, all columns return the corresponding original value 
integer=$(echo $1 | cut -d. -f1)
decimal=$(echo $1 | cut -d. -f2)

if [ "$integer" != "$1" ]; then
 # ${DD:= '.'} If the variable is undefined , Set to .  If there is value, keep the original value 
 result="${DD:= '.'}$decimal"
fi


thousands=$integer

while [ $thousands -gt 999  ]; do
# $(())  yes shell Used for calculation 
 remainder=$(($thousands % 1000))
 
 while [ ${
    #remainder} -lt 3 ]; do
    remainder="0$remainder"
 done
 result="${TD:= ','}${remainder}${result}"
 thousands=$(($thousands / 1000))
done

nicenum="${thousands}${result}"
echo " The second parameter "$2
if [ ! -z $2 ]; then
 echo $nicenum
fi
}

DD="."
TD=","
# getopts  Is used to parse parameters ,d:t:  Namely  -d -t  Parsing assigned variables opt
while getopts "d:t:" opt; do
 case $opt in
d ) DD="$OPTARG" ;;
t ) DD="$OPTARG" ;;
esac
done
#  Remove the corresponding parameter 
shift $(($OPTIND - 1))

if [ $# -eq 0 ]; then
 echo "Usage: $(basename $0) [ -d c ] [ -t c] number_value"
 echo " -d specifies the decimal point delimiter (default '.')"
 echo " -t specifies the thousands delimiter (default ',')"
 exit 0
fi
#  Force function echo 
nicenumber $1 1

exit 0