Could not execute system() command in Ruby Controller when I put my code live on server

Urgent help would be great! I have a ruby controller method:

def wayback
 $newvar = "wayback_machine_downloader http://example.com"
 system($newvar)
end

Now, above controller method runs like a charm locally i.e in localhost:3000 but when I put my code live in server then system($newvar) command does not work. I am using digitalocean server. I have searched a lot on inteet but could not find anything helpful.