Oh, that means you have to open a pipe to the process if you want to control it from another programming language? That would be a bit harder to leverage for automation (though I guess it's just a matter of writing a few helper functions, or you could always use bash and redirections if the language is ill-suited to pipes).

Add lftp on top of sftp and you get extensive scriptability. Working public anonymous demo: [1]

[1] - https://tinyvpn.org/sftp/#lftp