How to automate a keystroke to a cli terminal appilcation like ranger?

I'd like to send a keystroke to ranger, when I have ranger running and have gotten it's PID with: Output of ps aux | grep '[/]usr/bin/python -O /usr/bin/ranger': chris 5054 3.1 0.1 116248 27828 pts/0 S+ 16:57 0:00 /usr/bin/python -O /usr/bin/ranger Following from https://serverfault.com/a/178470/135542 , if I send the value j to it's STDIN with: echo "j" > /proc/5440/fd/0 I just seem to get j mixed in the output (after I ran the command a few times): However when I press j on my keyboard, it reacts correctly.