Dialog display with blank field assigned to variable in Mac Terminal?

I want to make a display box that has a text box that the user can enter a number into that will later be assigned to a variable. How would I do this?

Open AppleScript Editor, enter the following and save as script:

tell application "Terminal"
    repeat while true
        set input to display dialog "Enter a number:" default answer ""
        if button returned of input is equal to "OK" then
            try
                return (text returned of input) as number
            end try
        end if
    end repeat
end tell

(we need to tell application, because otherwise osascript doesn't allow user interaction)

Then run like this:

$ osascript path/to/script.scpt

Output of the program is the number the user entered.

Store in bash variable like this:

$ foo=$( osascript path/to/script.scpt )
$ echo $foo
42