run-shell-command with output

[Ag Ibragimov]

I need to run shell command and collect its output but I can't figure out, for 
some reason it doesn't get the output. I tried using run-shell-command and 
run-prog-collect-output, and they either return nil or an empty string.

I'm trying something like this:  `xrandr | grep " connected "`

Can anyone suggest what I might be missing or misconfigured on my system?