Login LOL from command line

Solution 1:

Most likely there's nothing available for what you're asking. The biggest reason is that the client is built to be launched by the patcher, not by users (allowing the game to start without going through the patcher would risk people playing with out-of-date software, or allow mods to go unchecked). Since the patcher has no way to use your credentials (and indeed shouldn't hold them), there'd be little reason to include that as something the for the game client to receive from it.

Hypothetically there could be console commands, but unfortunately, until they publish such commands (which they probably wouldn't), the only way to actually find out what console commands are available would be to reverse engineer the client, which is both difficult and in breach of their ToS.