When i get to the step of sudo yo hubot --owner="OWNER <owner@example.com>" --name="bot" --description="Bot" --adapter="rocketchat@0.1" , PuTTY gave me error saying i don't have permission to some npm file, I researched online, looks like it is a common problem. So i used https://docs.npmjs.com/getting-started/fixing-npm-permissions#option-2-change-npms-default-directory-to-another-directory
Option 1 to change the permission

and this is what i got from PuTTY, I get the feel this is the right direction, but detail is wrong, can anyone tell me what went wrong?

jy@ubuntu-1gb-sfo2-01:~$ npm config get prefix
/usr/local
jy@ubuntu-1gb-sfo2-01:~$ sudo chown -R $jy /usr/local/lib/node_modules/
[sudo] password for jy:
chown: missing operand after ‘/usr/local/lib/node_modules/’
Try 'chown --help' for more information.