Poettering: systemd for Administrators, Part VIII

Once you get into dealing with line numbers you're really dealing with the innards of your parser.

And while I'd _love_ for there to be a standard UNIX configuration file format instead of the current nightmare where every damn app uses its own format (and often a different format for different individual config files used by the same app!), that just ain't going to happen.

What you can do though is look into something like libconfig or libini or one of the dozen similar libraries and get foo.d support added there. It may not be a "standard" but it's at least a reliably available library you can depend on and use.