A comment: the "commandline" name does not seem to be a good fit -- I clicked on the link expected to something related to a command line, like a parser or a he

A comment: the "commandline" name does not seem to be a good fit -- I clicked on the link expected to something related to a command line, like a parser or a help printer, but it actually has nothing for it... So perhaps a better name would have something about terminal or console or reading or TUI (text user interface). Also, have you considered using one of the BSD/MIT readline replacements (like replxx, libedit, or linenoise) as a backend, instead on implementing your own? This can potentially save a lot of work adding proper terminal type support, highlighting, advanced editing etc...