first of all, I want to create shell script to start/stop downloads in torrent client. I don't need CLI but if you know how I can do that with CLI using shell script then it is okay.

I use jDownloader which is GUI based application but has some command line arguments as below which I use to start/stop download.

-h/--help       Show this help message
-a/--add-link(s)    Add links
-co/--add-container(s)  Add containers
-d/--start-download Start download
-D/--stop-download  Stop download
-H/--hide       Don't open Linkgrabber when adding Links
-m/--minimize       Minimize download window
-f/--focus      Get jD to foreground/focus
-s/--show       Show JAC prepared captchas
-t/--train      Train a JAC method
-r/--reconnect      Perform a Reconnect
-C/--captcha <filepath or url> <method> Get code from image using JAntiCaptcha
-p/--add-password(s)    Add passwords
-n --new-instance   Force new instance if another jD is running

So I can easily start/stop download as follows,

jdownloader --start-download
jdownloader --stop-download

now I want torrent client to do that through shell script.