Where are the /dev folder and the /dev/null device located on Mac OS X Mountain Lion?
It should be there as a character special file:

bash-3.2# cd /dev
bash-3.2# ls -l |grep null
crw-rw-rw-  1 root  wheel       3,   2 Mar  8 11:04 null


Finder doesn't show these folders so you need to be in terminal to see them.