gtkdialog again, the other way around this time – how to use bash variables in dialog?

[Johnny Rosenberg]

Here is some nonsense code that I'm trying to make work:

#!/bin/bash

#--- Define some variables -----------------------------------------------------
RosenTagDir="${HOME}/bin/RosenTagg"
InstrumentsList="${RosenTagDir}/Lists/Instruments"
MusiciansList="${RosenTagDir}/Lists/Musicians"
#-------------------------------------------------------------------------------


#--- Define and open the dialogue ----------------------------------------------
export MainDialog='
    <vbox>
        <hbox>
            <text>
                <label>Instrument:</label>
            </text>
            <comboboxentry>
                <default>Välj musikinstrument</default>
                <variable>Instrument</variable>
                <input file>$InstrumentsList</input>
            </comboboxentry>
            <text>
                <label>Utövare:</label>
            </text>
            <comboboxentry>
                <default>Välj utövare</default>
                <variable>Musician</variable>
                <input file>$MusiciansList</input>
            </comboboxentry>
        </hbox>
        <hbox>
            <button ok></button>
            <button cancel></button>
        </hbox>
    </vbox>'
gtkdialog --program MainDialog
#-------------------------------------------------------------------------------

The problem is that $InstrumentsList and $MusiciansList doesn't
expand, and whatever I tried I failed.

MainDialog is just a variable, right? But how do I make bash variables expand?
I have tried to fiddle with eval with no luck, for instance:

$ echo $MainDialog
<vbox> <hbox> <text> <label>Instrument:</label> </text>
<comboboxentry> <default>Välj musikinstrument</default>
<variable>Instrument</variable> <input file>$InstrumentsList</input>
</comboboxentry> <text> <label>Utövare:</label> </text>
<comboboxentry> <default>Välj utövare</default>
<variable>Musician</variable> <input file>$MusiciansList</input>
</comboboxentry> </hbox> <hbox> <button ok></button> <button
cancel></button> </hbox> </vbox>
$ eval echo $MainDialog
bash: syntaxfel nära den oväntade symbolen "<"
$

(The error message, which is in Swedish, means something like ”syntax
error near the unexpected symbol ”<”.)
So obviously (?) I need a way to expand the variables but nothing
else. Unfortunately I am a bit out of ideas, which is maybe not so
strange considering that I'm not only a gtkdialog beginner; I'm a bash
beginner as well, even though I learned a lot last years…


Johnny Rosenberg