I recently upgraded to version 1.5.1. Previously, I was able to use the "-p" and "-s" options to simplify the output when running on a dumb terminal (e.g., Emacs shell buffer). Now, when I use these options (and "-c"), even under a "normal" terminal window (e.g., xterm, Gnome Terminal), rtm prints neither the "Logged In As" message nor the ">" prompt. Typing in commands (e.g., "add task1") does not appear to work.
$ rtm
Logged In As: XXXXXXXX
> quit
$ rtm -c
[ no output after minutes ]
Interestingly, it does respond to CTRL-D (Unix end-of-file) and exits with a successful status.
I observe this behavior both under Linux and MacOS.
$ npm --version
6.9.0
$ rtm --version
1.5.1
$