[SOLVED] adding a string to a number/string

[Garrett85]

In the code below I'M trying to add a 00 to the left side of the NUM if NUM is 1 digit, e.g. input 4 -> 004 and to add single 0 to NUM if NUM is 2 digits, e.g. 45 -> 045. Any ideas on how to accomplish that?

#!/bin/bash

read -p "Enter a number no higher than the billions range" NUM

NUMBEROFDIGITS=${#NUM}
NUMBEROFGROUPS=$( expr ${NUMBEROFDIGITS} / 3 )

if [[ ${NUMBEROFDIGITS} -lt 3 ]]; then # {
    NUMBEROFGROUPS=1
    if [[ ${NUMBEROFDIGITS} -eq 2 ]]; then # {
        NUM="0"+"${NUM}"
        echo ${NUM}
    else # } {
        NUM="00"+"${NUM}"
        echo ${NUM}
    fi #}
elif [[ `expr ${NUMBEROFDIGITS} % 3` -ne 0 ]]; then # } {
    let NUMBEROFGROUPS=NUMBEROFGROUPS+1
fi # }

echo "Number of groups is: ${NUMBEROFGROUPS}"
#END

[alf55]

See the answer in your old thread (or is this a class assignment) because this already has shown up in another thread.