At what point does a config file become a programming language?

Question

I have been mulling over config files and their relationship to code for a while now and depending on the day and direction of the wind my opinions seem to change. More and mor

Answer 1

Recently I was working upon a project and I realised that I wanted to have conditionals inside my configuration file - which had previously just been a pretty simple one of the form:

key = val
key2 = val
name = `hostname`

I didn't want to write a mini-language, because unless I did it very carefully I couldn't allow the flexibility that would be useful.

Instead I decided that I'd have two forms:

1. If the file started with "#!" and was executable I'd parse the result of running it.

2. Otherwise I'd read it as-is

This means that I can now allow people to write "configuration files" that look like this:

 #!/usr/bin/perl
if ( -x /bin/foo ) 
{
   print <


This way I get the power of a dynamic configuration file if the user wants to use it, and the simplicity of not having to write my own mini-language.