dynamic configuration with boost program_options

Question

Is there a way to load a dynamic INI file like the one below.

[basic]
number_of_servers=3

[server1]
ip=10.20.30.40
password=sdfslkhf    

[server2]
ip=10.20.30.41
password=sdfslkhf

[server3]
ip=10.20.30.42
password=sdfslkhf

Here the idea is that the servers that are defined here is very specific to the software's deployment; so the admin decides how many servers participate in the configuration.

Is there a way to handle this in boost program_options?

Answer 1

Another, potentially more standard way, would be like this:

[basic]
number_of_servers=3

[server]
name=server1
ip=10.20.30.40
password=sdfslkhf    

[server]
name=server2
ip=10.20.30.41
password=sdfslkhf

[server]
name=server3
ip=10.20.30.42
password=sdfslkhf

This way you don't need to worry about undefined section names, and I think this style is more widely used as well (definitely it's how QuickFIX does it, in a way very similar to what I outlined).

And you can probably remove the number_of_servers entry, and just use the count() function to find how many server sections there are.

Answer 2

There is an optional bool parameter to allow for unregistered entries in the parse_config_file function. It's set to false by default. See the documentation here:

http://www.boost.org/doc/libs/1_45_0/doc/html/boost/program_options/parse_config_file_id991860.html

If you call this function with true then it will add any unregistered entries into the variables_map as strings. You can check whether they exist with the variables_map::count function.

I hope that helps.

Answer 3

Sure you can. The server sections have a pattern: just load all those matching the pattern into a list of servers.

Answer 4

The challenges I faced while resolving this was to make sure the sections are kept together and are no way mixed up.

In the end I relied on a options_description with the known/finite options and then using the parsed_options that come out of parse_config_file, I had to collect all unrecognized options ( collect_unrecognized ). Then I had to iterate it to pick the options in order.

Thanks every one for their contribution.