[Nottingham] bash scripting - gotme

[david wolfson]

Morning!
I've been got by some bash scripting I've been trying to sort out for 
someone in my office, and haven't been able to work out how to get round 
it.  I hoped someone wiser (but not necessarily older ;-)) might be able 
help...

The setup is this; we have another script that does a bunch of image 
analysis, but it needs to run from in the relavant folder.  There a 
quite a few folders, and the aim is to write a script to automate the 
task (i.e. cd into a folder, run the analysis script, cd .., cd into the 
next folder...). So far, we've got the each folder name assigned to 
variable i.e.

$a1=folder1
$a2=folder2
...
$an=foldern

The difficult bit appears to be automatically moving in and out of these 
folders. So far we tried variations on the following:

let i=1
 
        until [ $i -gt $no_of_folders ]; do
 
        folder_var='$'a$line_count                        
        cd $folder_var
        analysis_prog
        cd ..
        i=$(expr $i + 1) 

        done

You'll not be surprised to hear that this doesn't work as it can't find 
a folder called '$a1'.  Clearly the string substitution is not working, 
as it is reading $folder_var as a string, not a variable.  As I say, 
we've tried variations on this, including not using the folder_var 
variable at all, but with the same result. I've sent the lass who's 
needs this off to look at the advance bash scripting sites, but I 
thought it was an interesing (an hopefully simple) one, if anyone out 
there has encountered it before...

I guess the simplified version is; 'how do you get bash to read a string 
as a variable name?'

Thanks for any hints/tips/solutions,

Dave