BASH scripts : whiptail file select

Build an array of file names and menu select tags:

i=0
s=65    # decimal ASCII "A" 
for f in *.tgz
do
    # convert to octal then ASCII character for selection tag
    files[i]=$(echo -en "\0$(( $s / 64 * 100 + $s % 64 / 8 * 10 + $s % 8 ))")
    files[i+1]="$f"    # save file name
    ((i+=2))
    ((s++))
done

A method like this will work even if there are filenames with spaces. If the number of files is large, you may have to devise another tag strategy.

Using alpha characters for the tags lets you press a letter to jump to the item. Numeric tags don't seem to do that. If you don't need that behavior, then you can eliminate some complexity.

Display the menu:

whiptail --backtitle "Welcome to SEUL" --title "Restore Files" \
    --menu "Please select the file to restore" 14 40 6 "${files[@]}"

If the exit code is 255, the dialog was canceled.

if [[ $? == 255 ]]
then
    do cancel stuff
fi

To catch the selection in a variable, use this structure (substitute your whiptail command for "whiptail-command"):

result=$(whiptail-command 2>&1 >/dev/tty)

Or

result=$(whiptail-command 3>&2 2>&1 1>&3-)

The variable $result will contain a letter of the alphabet that corresponds to a file in the array. Unfortunately, Bash prior to version 4 doesn't support associative arrays. You can calculate the index into the array of the file from the letter like this (notice the "extra" single quote):

((index = 2 * ( $( printf "%d" "'$result" ) - 65 ) + 1 ))

Example:

Welcome to SEUL
                ┌──────────┤ Restore Files ├───────────┐
                │ Please select the file to restore    │
                │                                      │
                │            A one.tgz      ↑          │
                │            B two.tgz      ▮          │
                │            C three.tgz    ▒          │
                │            D another.tgz  ▒          │
                │            E more.tgz     ▒          │
                │            F sp ac es.tgz ↓          │
                │                                      │
                │                                      │
                │       <Ok>           <Cancel>        │
                │                                      │
                └──────────────────────────────────────┘

Whiptail is a lightweight reimplementation of the most popular features of dialog, using the Newt library. I did a quick check, and many features in Whiptail seem to behave like their counterparts in dialog. So, a dialog tutorial should get you started. You can find one here but Google is your friend of course. On the other hand, the extended example probably contains a lot of inspiration for your problem.