[chli]

I've used http://docopt.org/ in the past for a toy project.

It's an interesting concept where you define the command line "help" syntax and it generates an arguments structure and an associated parser. I've used the C version, I believe the C++ version is better maintained.

[thechao]

Docopt is great until you start digging in and discover the author doesn't have the first clue about parsing. I don't mean in the sense of "weird opinions about recursive descent", but in the literal sense of "has no idea what parsing is or means". The internal implementation is a gigantic clusterfuck of the worst sort of poorly constructed, unmaintainable code you could imagine.

I maintain two ports of docopt and I'm telling you not to use it.