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create variable name in bash

Hi,

I have a bash script which takes it's configuration options from another file.

The options are variables like:

Code:

abc_hello=1

abc_byebye=0

xyz_dog=4

xyz_tree=7

etc

Point being, the name consists of two or more parts.

The script loads the conf file:

Code:

. /path/to/config.conf

Now it has these variables,

Code:

echo $xyz_tree

will return 7 and so on.

Problem is, there are many variables and they change but are systematic. The script can actually generate names like abc_hello correctly from other settings in the config file and then, hopefully, use them in loops.

How can I force the generated name to act as a variable?

For example:

Code:

hello_world=10



one=hello

two=world

Now I want to echo the result "10" using "$one" and "$two".

Code:

echo "$"$one"_"$two""

produces '$hello_world', but I need the value of $hello_world which would be '10'.

Is it possible at all with bash 2? I have tried various combinations but haven't had any luck. I hope I'm just missing some kind of bash trick.

Thanks.

Quote:

I hope I'm just missing some kind of bash trick.

Fortunately, you are. :)

Code:

#!/bin/bash



hello_world=10



one=hello

two=world



varname=${one}_${two}  # Combining the two names to one

varvalue=${!varname}  # Here's the trick



echo $varvalue

Quote:

Originally Posted by Hko

Here's the trick

Thank you very very much. That'll save me quite a few headaches.

The bourne shell compatible way to do it is with eval:

Code:

eval varvalue=$varname